Peter K. Kitanidis

All Publications

• Aquifer conditions, not irradiance determine the potential of photovoltaic energy for groundwater pumping across Africa COMMUNICATIONS EARTH & ENVIRONMENT Meunier, S., Kitanidis, P. K., Cordier, A., MacDonald, A. M. 2023; 4 (1)

  View details for DOI 10.1038/s43247-023-00695-8

  View details for Web of Science ID 000940384700002

• Variational encoder geostatistical analysis (VEGAS) with an application to large scale riverine bathymetry ADVANCES IN WATER RESOURCES Forghani, M., Qian, Y., Lee, J., Farthing, M., Hesser, T., Kitanidis, P. K., Darve, E. F. 2022; 170

  View details for DOI 10.1016/j.advwatres.2022.104323

  View details for Web of Science ID 000883792800002

• Integration of Deep Learning-Based Inversion and Upscaled Mass-Transfer Model for DNAPL Mass-Discharge Estimation and Uncertainty Assessment WATER RESOURCES RESEARCH Kang, X., Kokkinaki, A., Shi, X., Yoon, H., Lee, J., Kitanidis, P. K., Wu, J. 2022; 58 (10)

  View details for DOI 10.1029/2022WR033277

  View details for Web of Science ID 000871486400001

• Hierarchical Bayesian Inversion of Global Variables and Large-Scale Spatial Fields WATER RESOURCES RESEARCH Wang, L., Kitanidis, P. K., Caers, J. 2022; 58 (5)

  View details for DOI 10.1029/2021WR031610

  View details for Web of Science ID 000788106700001

• An information inequality for Bayesian analysis in imaging problems GEM-INTERNATIONAL JOURNAL ON GEOMATHEMATICS Kitanidis, P. K. 2021; 12 (1)

  View details for DOI 10.1007/s13137-021-00178-y

  View details for Web of Science ID 000660532300001

• Integrating deep learning-based data assimilation and hydrogeophysical data for improved monitoring of DNAPL source zones during remediation JOURNAL OF HYDROLOGY Kang, X., Kokkinaki, A., Power, C., Kitanidis, P. K., Shi, X., Duan, L., Liu, T., Wu, J. 2021; 601

  View details for DOI 10.1016/j.jhydrol.2021.126655

  View details for Web of Science ID 000695816300068

• Application of deep learning to large scale riverine flow velocity estimation STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT Forghani, M., Qian, Y., Lee, J., Farthing, M. W., Hesser, T., Kitanidis, P. K., Darve, E. F. 2021

  View details for DOI 10.1007/s00477-021-01988-0

  View details for Web of Science ID 000620880500002

• Hydrogeophysical Characterization of Nonstationary DNAPL Source Zones by Integrating a Convolutional Variational Autoencoder and Ensemble Smoother WATER RESOURCES RESEARCH Kang, X., Kokkinaki, A., Kitanidis, P. K., Shi, X., Lee, J., Mo, S., Wu, J. 2021; 57 (2)

  View details for DOI 10.1029/2020WR028538

  View details for Web of Science ID 000624603200018

• Deep learning technique for fast inference of large-scale riverine bathymetry ADVANCES IN WATER RESOURCES Ghorbanidehno, H., Lee, J., Farthing, M., Hesser, T., Darve, E. F., Kitanidis, P. K. 2021; 147

  View details for DOI 10.1016/j.advwatres.2020.103715

  View details for Web of Science ID 000606420300005

• Routing algorithms as tools for integrating social distancing with emergency evacuation. Scientific reports Tsai, Y., Rastogi, C., Kitanidis, P. K., Field, C. B. 2021; 11 (1): 19623

  Abstract

  One of the lessons from the COVID-19 pandemic is the importance of social distancing, even in challenging circumstances such as pre-hurricane evacuation. To explore the implications of integrating social distancing with evacuation operations, we describe this evacuation process as a Capacitated Vehicle Routing Problem (CVRP) and solve it using a DNN (Deep Neural Network)-based solution (Deep Reinforcement Learning) and a non-DNN solution (Sweep Algorithm). A central question is whether Deep Reinforcement Learning provides sufficient extra routing efficiency to accommodate increased social distancing in a time-constrained evacuation operation. We found that, in comparison to the Sweep Algorithm, Deep Reinforcement Learning can provide decision-makers with more efficient routing. However, the evacuation time saved by Deep Reinforcement Learning does not come close to compensating for the extra time required for social distancing, and its advantage disappears as the emergency vehicle capacity approaches the number of people per household.

  View details for DOI 10.1038/s41598-021-98643-z

  View details for PubMedID 34608178

• Sensitivity Analysis of Photovoltaic Pumping Systems for Domestic Water Supply Meunier, S., Queval, L., Darga, A., Dessante, P., Marchand, C., Heinrich, M., Cherni, J. A., de la Fresnaye, E. A., Vido, L., Multon, B., Kitanidis, P. K. IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. 2020: 6734–43

  View details for DOI 10.1109/TIA.2020.3013513

  View details for Web of Science ID 000587752900062

• Improved Characterization of DNAPL Source Zones via Sequential Hydrogeophysical Inversion of Hydraulic-Head, Self-Potential and Partitioning Tracer Data WATER RESOURCES RESEARCH Kang, X., Kokkinaki, A., Kitanidis, P. K., Shi, X., Revil, A., Lee, J., Ahmed, A., Wu, J. 2020; 56 (8)

  View details for DOI 10.1029/2020WR027627

  View details for Web of Science ID 000582701700050

• Borehole water level model for photovoltaic water pumping systems APPLIED ENERGY Vezin, T., Meunier, S., Queval, L., Cherni, J. A., Vido, L., Darga, A., Dessante, P., Kitanidis, P. K., Marchand, C. 2020; 258

  View details for DOI 10.1016/j.apenergy.2019.114080

  View details for Web of Science ID 000506575100016

• Aquifer Imaging with Oscillatory Hydraulic Tomography: Application at the Field Scale. Ground water Cardiff, M., Zhou, Y., Barrash, W., Kitanidis, P. K. 2019

  Abstract

  Modeling and laboratory experiments have demonstrated the ability of oscillatory hydraulic tomography (OHT) to characterize heterogeneity in aquifer hydraulic properties. In OHT, a location is stressed via periodic pumping / injection at a set frequency, and the resulting head signal is measured at a number of monitoring locations. The source of oscillations is repeatedly moved, allowing tomographic imaging of aquifer properties. Changing the period of oscillation also results in observations with additional information. In theory, OHT is comparable to other hydraulic tomography methods in that distributed pressure change measurements provide characterization information. In practice, OHT has several benefits including: i) little to no water injected into or extracted from the aquifer; and ii) an observational signal at a set period that can be easily extracted in the presence of noise. We report the first field application of OHT, carried out at the Boise Hydrogeophysical Research Site (BHRS) using an oscillating signal generator with a very small cycling volume of <2 liters, and a period range of 5 to 70 seconds. For these tests, signals were detected at distances of over 15 m. After processing to extract periodic signal properties, we perform tomography using a frequency-domain numerical model for groundwater flow. In comparing results against prior characterization results from the BHRS, we find moderate to strong positive correlations between K profiles estimated via different methods at multiple wells, with moderate overall correlation between estimated 3-D K volumes. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1111/gwat.12960

  View details for PubMedID 31691263

• A validated model of a photovoltaic water pumping system for off-grid rural communities APPLIED ENERGY Meunier, S., Heinrich, M., Queval, L., Cherni, J. A., Vido, L., Darga, A., Dessante, P., Multon, B., Kitanidis, P. K., Marchand, C. 2019; 241: 580–91

  View details for DOI 10.1016/j.apenergy.2019.03.035

  View details for Web of Science ID 000465509500044

• Novel Data Assimilation Algorithm for Nearshore Bathymetry JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY Ghorbanidehno, H., Lee, J., Farthing, M., Hesser, T., Kitanidis, P. K., Darve, E. F. 2019; 36 (4): 699–715

  View details for DOI 10.1175/JTECH-D-18-0067.1

  View details for Web of Science ID 000465145300002

• Effect of irradiance data on the optimal sizing of photovoltaic water pumping systems Meunier, S., Queval, L., Heinrich, M., de la Fresnaye, E. A., Cherni, J. A., Vido, L., Darga, A., Dessante, P., Multon, B., Kitanidis, P. K., Marchand, C., IEEE IEEE. 2019: 653–58

  View details for Web of Science ID 000542034900138

• Modelling and Optimal Sizing of Photovoltaic Water Pumping Systems - Sensitivity Analysis Meunier, S., Queval, L., Darga, A., Dessante, P., Marchand, C., Heinrich, M., Cherni, J. A., de la Fresnaye, E. A., Vido, L., Multon, B., Kitanidis, P. K., IEEE IEEE. 2019

  View details for Web of Science ID 000505687800042

• Fast Large-Scale Joint Inversion for Deep Aquifer Characterization Using Pressure and Heat Tracer Measurements Lee, J., Kokkinaki, A., Kitanidis, P. K. SPRINGER. 2018: 533–43

  View details for DOI 10.1007/s11242-017-0924-y

  View details for Web of Science ID 000434910500006

• Riverine Bathymetry Imaging With Indirect Observations WATER RESOURCES RESEARCH Lee, J., Ghorbanidehno, H., Farthing, M. W., Hesser, T. J., Darve, E. F., Kitanidis, P. K. 2018; 54 (5): 3704–27

  View details for DOI 10.1029/2017WR021649

  View details for Web of Science ID 000442351300025

• Longitudinal dispersion coefficients for numerical modeling of groundwater solute transport in heterogeneous formations. Journal of contaminant hydrology Lee, J., Rolle, M., Kitanidis, P. K. 2018; 212: 41–54

  Abstract

  Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion and mass transfer limitations, i.e., the exchange of mass between the permeable matrix and the low permeability inclusions. We illustrate the physical meaning of the method and we show how the block longitudinal dispersivity approaches, under certain conditions, the Scheidegger limit at large Peclet numbers. Lastly, we discuss the potential and limitations of the method to accurately describe dispersion in solute transport applications in heterogeneous aquifers.

  View details for PubMedID 28943098

• Optimal estimation and scheduling in aquifer management using the rapid feedback control method ADVANCES IN WATER RESOURCES Ghorbanidehno, H., Kokkinaki, A., Kitanidis, P. K., Darve, E. 2017; 110: 310–18

  View details for DOI 10.1016/j.advwatres.2017.10.011

  View details for Web of Science ID 000418262400024

• Smoothing-based compressed state Kalman filter for joint state-parameter estimation: Applications in reservoir characterization and CO2 storage monitoring WATER RESOURCES RESEARCH Li, Y. J., Kokkinaki, A., Darve, E. F., Kitanidis, P. K. 2017; 53 (8): 7190–7207

  View details for DOI 10.1002/2016WR020168

  View details for Web of Science ID 000411202000044

• Teaching and communicating dispersion in hydrogeology, with emphasis on the applicability of the Fickian model ADVANCES IN WATER RESOURCES Kitanidis, P. K. 2017; 106: 11–23

  View details for DOI 10.1016/j.advwatres.2017.01.006

  View details for Web of Science ID 000407660800004

• Improved characterization of heterogeneous permeability in saline aquifers from transient pressure data during freshwater injection WATER RESOURCES RESEARCH Kang, P. K., Lee, J., Fu, X., Lee, S., Kitanidis, P. K., Juanes, R. 2017; 53 (5): 4444–58

  View details for DOI 10.1002/2016WR020089

  View details for Web of Science ID 000403712100054

• Trace organic chemical attenuation during managed aquifer recharge: Insights from a variably saturated 2D tank experiment JOURNAL OF HYDROLOGY Regnery, J., Lee, J., Drumheller, Z. W., Drewes, J. E., Illangasekare, T. H., Kitanidis, P. K., McCray, J. E., Smits, K. M. 2017; 548: 641–51

  View details for DOI 10.1016/j.jhydrol.2017.03.038

  View details for Web of Science ID 000403739000049

• Optimal Decision Making Algorithm for Managed Aquifer Recharge and Recovery Operation Using Near Real-Time Data: Benchtop Scale Laboratory Demonstration GROUND WATER MONITORING AND REMEDIATION Drumheller, Z., Smits, K. M., Illangasekare, T. H., Regnery, J., Lee, J., Kitanidis, P. K. 2017; 37 (1): 27-41

  View details for DOI 10.1111/gwmr.12198

  View details for Web of Science ID 000395067500003

• MULTIPRECONDITIONED GMRES FOR SHIFTED SYSTEMS SIAM JOURNAL ON SCIENTIFIC COMPUTING Bakhos, T., Kitanidis, P. K., Ladenheim, S., Saibaba, A. K., Szyld, D. B. 2017; 39 (5): S222–S247

  View details for DOI 10.1137/16M1068694

  View details for Web of Science ID 000415797300011

• Scalable subsurface inverse modeling of huge data sets with an application to tracer concentration breakthrough data from magnetic resonance imaging WATER RESOURCES RESEARCH Lee, J., Yoon, H., Kitanidis, P. K., Werth, C. J., Valocchi, A. J. 2016; 52 (7): 5213-5231

  View details for DOI 10.1002/2015WR018483

  View details for Web of Science ID 000383683800015

• Randomized algorithms for generalized Hermitian eigenvalue problems with application to computing Karhunen-Loeve expansion NUMERICAL LINEAR ALGEBRA WITH APPLICATIONS Saibaba, A. K., Lee, J., Kitanidis, P. K. 2016; 23 (2): 314-339

  View details for DOI 10.1002/nla.2026

  View details for Web of Science ID 000369856400006

• Hydraulic Tomography: Continuity and Discontinuity of High-K and Low-K Zones GROUNDWATER Hochstetler, D. L., Barrash, W., Leven, C., Cardiff, M., Chidichimo, F., Kitanidis, P. K. 2016; 54 (2): 171-185

  Abstract

  Hydraulic tomography is an emerging field and modeling method that provides a continuous hydraulic conductivity (K) distribution for an investigated region. Characterization approaches that rely on interpolation between one-dimensional (1D) profiles have limited ability to accurately identify high-K channels, juxtapositions of lenses with high K contrast, and breaches in layers or channels between such profiles. However, locating these features is especially important for groundwater flow and transport modeling, and for design and operation of in situ remediation in complex hydrogeologic environments. We use transient hydraulic tomography to estimate 3D K in a volume of 15-m diameter by 20-m saturated thickness in a highly heterogeneous unconfined alluvial (clay to sand-and-gravel) aquifer with a K range of approximately seven orders of magnitude at an active industrial site in Assemini, Sardinia, Italy. A modified Levenberg-Marquardt algorithm was used for geostatistical inversion to deal with the nonlinear nature of the highly heterogeneous system. The imaging results are validated with pumping tests not used in the tomographic inversion. These tests were conducted from three of five clusters of continuous multichannel tubing (CMTs) installed for observation in the tomographic testing. Locations of high-K continuity and discontinuity, juxtaposition of very high-K and very low-K lenses, and low-K "plugs" are evident in regions of the investigated volume where they likely would not have been identified with interpolation from 1D profiles at the positions of the pumping well and five CMT clusters. Quality assessment methods identified a suspect high-K feature between the tested volume and a lateral boundary of the model.

  View details for DOI 10.1111/gwat.12344

  View details for Web of Science ID 000373211200007

• Hydraulic Tomography: Continuity and Discontinuity of High-K and Low-K Zones. Ground water Hochstetler, D. L., Barrash, W., Leven, C., Cardiff, M., Chidichimo, F., Kitanidis, P. K. 2016; 54 (2): 171-185

  Abstract

  Hydraulic tomography is an emerging field and modeling method that provides a continuous hydraulic conductivity (K) distribution for an investigated region. Characterization approaches that rely on interpolation between one-dimensional (1D) profiles have limited ability to accurately identify high-K channels, juxtapositions of lenses with high K contrast, and breaches in layers or channels between such profiles. However, locating these features is especially important for groundwater flow and transport modeling, and for design and operation of in situ remediation in complex hydrogeologic environments. We use transient hydraulic tomography to estimate 3D K in a volume of 15-m diameter by 20-m saturated thickness in a highly heterogeneous unconfined alluvial (clay to sand-and-gravel) aquifer with a K range of approximately seven orders of magnitude at an active industrial site in Assemini, Sardinia, Italy. A modified Levenberg-Marquardt algorithm was used for geostatistical inversion to deal with the nonlinear nature of the highly heterogeneous system. The imaging results are validated with pumping tests not used in the tomographic inversion. These tests were conducted from three of five clusters of continuous multichannel tubing (CMTs) installed for observation in the tomographic testing. Locations of high-K continuity and discontinuity, juxtaposition of very high-K and very low-K lenses, and low-K "plugs" are evident in regions of the investigated volume where they likely would not have been identified with interpolation from 1D profiles at the positions of the pumping well and five CMT clusters. Quality assessment methods identified a suspect high-K feature between the tested volume and a lateral boundary of the model.

  View details for DOI 10.1111/gwat.12344

  View details for PubMedID 26096272

• Imaging geochemical heterogeneities using inverse reactive transport modeling: An example relevant for characterizing arsenic mobilization and distribution ADVANCES IN WATER RESOURCES Fakhreddine, S., Lee, J., Kitanidis, P. K., Fendorf, S., Rolle, M. 2016; 88: 186-197

  View details for DOI 10.1016/j.advwatres.2015.12.005

  View details for Web of Science ID 000371311800017

• Real-time data assimilation for large-scale systems: The spectral Kalman filter ADVANCES IN WATER RESOURCES Ghorbanidehno, H., Kokkinaki, A., Li, J. Y., Darve, E., Kitanidis, P. K. 2015; 86: 260-272

  View details for DOI 10.1016/j.advwatres.2015.07.017

  View details for Web of Science ID 000365623500002

• Frequency dependent hydraulic properties estimated from oscillatory pumping tests in an unconfined aquifer JOURNAL OF HYDROLOGY Rabinovich, A., Barrash, W., Cardiff, M., Hochstetler, D. L., Bakhos, T., Dagan, G., Kitanidis, P. K. 2015; 531: 2-16

  View details for DOI 10.1016/j.jhydrol.2015.08.021

  View details for Web of Science ID 000366769200002

• The compressed state Kalman filter for nonlinear state estimation: Application to large-scale reservoir monitoring WATER RESOURCES RESEARCH Li, J. Y., Kokkinaki, A., Ghorbanidehno, H., Darve, E. F., Kitanidis, P. K. 2015; 51 (12): 9942-9963

  View details for DOI 10.1002/2015WR017203

  View details for Web of Science ID 000368421500031

• A fast algorithm for parabolic PDE-based inverse problems based on Laplace transforms and flexible Krylov solvers JOURNAL OF COMPUTATIONAL PHYSICS Bakhos, T., Saibaba, A. K., Kitanidis, P. K. 2015; 299: 940-954

  View details for DOI 10.1016/j.jcp.2015.07.007

  View details for Web of Science ID 000360087400047

• Fast computation of uncertainty quantification measures in the geostatistical approach to solve inverse problems ADVANCES IN WATER RESOURCES Saibaba, A. K., Kitanidis, P. K. 2015; 82: 124-138

  View details for DOI 10.1016/j.advwatres.2015.04.012

  View details for Web of Science ID 000357742600010

• Persistent questions of heterogeneity, uncertainty, and scale in subsurface flow and transport WATER RESOURCES RESEARCH Kitanidis, P. K. 2015; 51 (8): 5888-5904

  View details for DOI 10.1002/2015WR017639

  View details for Web of Science ID 000363402800002

• Compressed state Kalman filter for large systems ADVANCES IN WATER RESOURCES Kitanidis, P. K. 2015; 76: 120–26

  View details for DOI 10.1016/j.advwatres.2014.12.010

  View details for Web of Science ID 000349673500010

• Fast Kalman filter using hierarchical matrices and a low-rank perturbative approach INVERSE PROBLEMS Saibaba, A. K., Miller, E. L., Kitanidis, P. K. 2015; 31 (1)

  View details for DOI 10.1088/0266-5611/31/1/015009

  View details for Web of Science ID 000347417900010

• Relating relative hydraulic and electrical conductivity in the unsaturated zone WATER RESOURCES RESEARCH Mawer, C., Knight, R., Kitanidis, P. K. 2015; 51 (1): 599-618

  View details for DOI 10.1002/2014WR015658

  View details for Web of Science ID 000349889800033

• Effects of compound-specific dilution on transient transport and solute breakthrough: A pore-scale analysis ADVANCES IN WATER RESOURCES Rolle, M., Kitanidis, P. K. 2014; 71: 186-199

  View details for DOI 10.1016/j.advwatres.2014.06.012

  View details for Web of Science ID 000340927600016

• Principal Component Geostatistical Approach for large-dimensional inverse problems WATER RESOURCES RESEARCH Kitanidis, P. K., Lee, J. 2014; 50 (7): 5428-5443

  View details for DOI 10.1002/2013WR014630

  View details for Web of Science ID 000342632000004

• Principal Component Geostatistical Approach for large-dimensional inverse problems. Water resources research Kitanidis, P. K., Lee, J. 2014; 50 (7): 5428-5443

  Abstract

  The quasi-linear geostatistical approach is for weakly nonlinear underdetermined inverse problems, such as Hydraulic Tomography and Electrical Resistivity Tomography. It provides best estimates as well as measures for uncertainty quantification. However, for its textbook implementation, the approach involves iterations, to reach an optimum, and requires the determination of the Jacobian matrix, i.e., the derivative of the observation function with respect to the unknown. Although there are elegant methods for the determination of the Jacobian, the cost is high when the number of unknowns, m, and the number of observations, n, is high. It is also wasteful to compute the Jacobian for points away from the optimum. Irrespective of the issue of computing derivatives, the computational cost of implementing the method is generally of the order of m2n, though there are methods to reduce the computational cost. In this work, we present an implementation that utilizes a matrix free in terms of the Jacobian matrix Gauss-Newton method and improves the scalability of the geostatistical inverse problem. For each iteration, it is required to perform K runs of the forward problem, where K is not just much smaller than m but can be smaller that n. The computational and storage cost of implementation of the inverse procedure scales roughly linearly with m instead of m2 as in the textbook approach. For problems of very large m, this implementation constitutes a dramatic reduction in computational cost compared to the textbook approach. Results illustrate the validity of the approach and provide insight in the conditions under which this method perform best.

  View details for DOI 10.1002/2013WR014630

  View details for PubMedID 25558113

  View details for PubMedCentralID PMC4280892

• Large-scale hydraulic tomography and joint inversion of head and tracer data using the Principal Component Geostatistical Approach (PCGA) WATER RESOURCES RESEARCH Lee, J., Kitanidis, P. K. 2014; 50 (7): 5410-5427

  View details for DOI 10.1002/2014WR015483

  View details for Web of Science ID 000342632000003

• A Kalman filter powered by H-2-matrices for quasi-continuous data assimilation problems WATER RESOURCES RESEARCH Li, J. Y., Ambikasaran, S., Darve, E. F., Kitanidis, P. K. 2014; 50 (5): 3734-3749

  View details for DOI 10.1002/2013WR014607

  View details for Web of Science ID 000337672900008

• Estimating temporal changes in hydraulic head using InSAR data in the San Luis Valley, Colorado WATER RESOURCES RESEARCH Reeves, J. A., Knight, R., Zebker, H. A., Kitanidis, P. K., Schreueder, W. A. 2014; 50 (5): 4459-4473

  View details for DOI 10.1002/2013WR014938

  View details for Web of Science ID 000337672900047

• Stochastic modeling of short-term exposure close to an air pollution source in a naturally ventilated room: An autocorrelated random walk method JOURNAL OF EXPOSURE SCIENCE AND ENVIRONMENTAL EPIDEMIOLOGY Cheng, K., Acevedo-Bolton, V., Jiang, R., Klepeis, N. E., Ott, W. R., Kitanidis, P. K., Hildemann, L. M. 2014; 24 (3): 311-318

  Abstract

  For an actively emitting source such as cooking or smoking, indoor measurements have shown a strong "proximity effect" within 1 m. The significant increase in both the magnitude and variation of concentration near a source is attributable to transient high peaks that occur sporadically-and these "microplumes" cause great uncertainty in estimating personal exposure. Recent field studies in naturally ventilated rooms show that close-proximity concentrations are approximately lognormally distributed. We use the autocorrelated random walk method to represent the time-varying directionality of indoor emissions, thereby predicting the time series and frequency distributions of concentrations close to an actively emitting point source. The predicted 5-min concentrations show good agreement with measurements from a point source of CO in a naturally ventilated house-the measured and predicted frequency distributions at 0.5- and 1-m distances are similar and approximately lognormal over a concentration range spanning three orders of magnitude. By including the transient peak concentrations, this random airflow modeling method offers a way to more accurately assess acute exposure levels for cases where well-defined airflow patterns in an indoor space are not available.

  View details for DOI 10.1038/jes.2013.63

  View details for Web of Science ID 000334571000011

  View details for PubMedID 24064529

• Data processing for oscillatory pumping tests JOURNAL OF HYDROLOGY Bakhos, T., Cardiff, M., Barrash, W., Kitanidis, P. K. 2014; 511: 310-319

  View details for DOI 10.1016/j.jhydrol.2014.01.007

  View details for Web of Science ID 000335274900029

• Long-term mass transfer and mixing-controlled reactions of a DNAPL plume from persistent residuals. Journal of contaminant hydrology Liu, Y., Illangasekare, T. H., Kitanidis, P. K. 2014; 157: 11-24

  Abstract

  Understanding and being able to predict the long-term behavior of DNAPL (i.e., PCE and TCE) residuals after active remediation has ceased have become increasingly important as attention at many sites turns from aggressive remediation to monitored natural attenuation and long-term stewardship. However, plume behavior due to mass loading and reactions during these later phases is less studied as they involve large spatial and temporal scales. We apply both theoretical analysis and pore-scale simulations to investigate mass transfer from DNAPL residuals and subsequent reactions within the generated plume, and, in particular, to show the differences between early- and late-time behaviors of the plume. In the zone of entry of the DNAPL entrapment zone where the concentration boundary layer in the flowing groundwater has not fully developed, the pore-scale simulations confirm the past findings based on laboratory studies that the mass transfer increases as a power-law function of the Peclét number, and is enhanced due to reactions in the plume. Away from the entry zone and further down gradient, the long-term reactions are limited by the available additive and mixing in the porous medium, thereby behave considerably differently from the entry zone. For the reaction between the contaminant and an additive with intrinsic second-order bimolecular kinetics, the late-time reaction demonstrates a first-order decay macroscopically with respect to the mass of the limiting additive, not with respect to that of the contaminant. The late-time decay rate only depends on the intrinsic reaction rate and the solubility of the entrapped DNAPL. At the intermediate time, the additive decays exponentially with the square of time (t(2)), instead of time (t). Moreover, the intermediate decay rate also depends on the initial conditions, the spatial distribution of DNAPL residuals, and the effective dispersion coefficient.

  View details for DOI 10.1016/j.jconhyd.2013.10.008

  View details for PubMedID 24269948

• Fast iterative implementation of large-scale nonlinear geostatistical inverse modeling WATER RESOURCES RESEARCH Liu, X., Zhou, Q., Kitanidis, P. K., Birkholzer, J. T. 2014; 50 (1): 198-207

  View details for DOI 10.1002/2012WR013241

  View details for Web of Science ID 000331798800014

• Large-scale stochastic linear inversion using hierarchical matrices COMPUTATIONAL GEOSCIENCES Ambikasaran, S., Li, J. Y., Kitanidis, P. K., Darve, E. 2013; 17 (6): 913-927

  View details for DOI 10.1007/s10596-013-9364-0

  View details for Web of Science ID 000328319900004

• A mathematical and computational study of the dispersivity tensor in anisotropic porous media ADVANCES IN WATER RESOURCES Liu, Y., Kitanidis, P. K. 2013; 62: 303-316

  View details for DOI 10.1016/j.advwatres.2013.07.015

  View details for Web of Science ID 000327540400012

• Surge block method for controlling well clogging and sampling sediment during bioremediation. Water research Wu, W., Watson, D. B., Luo, J., Carley, J., Mehlhorn, T., Kitanidis, P. K., Jardine, P. M., Criddle, C. S. 2013; 47 (17): 6566-6573

  Abstract

  A surge block treatment method (i.e. inserting a solid rod plunger with a flat seal that closely fits the casing interior into a well and stocking it up and down) was performed for the rehabilitation of wells clogged with biomass and for the collection of time series sediment samples during in situ bioremediation tests for U(VI) immobilization at a the U.S. Department of Energy site in Oak Ridge, TN. The clogging caused by biomass growth had been controlled by using routine surge block treatment for18 times over a nearly four year test period. The treatment frequency was dependent of the dosage of electron donor injection and microbial community developed in the subsurface. Hydraulic tests showed that the apparent aquifer transmissivity at a clogged well with an inner diameter (ID) of 10.16 cm was increased by 8-13 times after the rehabilitation, indicating the effectiveness of the rehabilitation. Simultaneously with the rehabilitation, the surge block method was successfully used for collecting time series sediment samples composed of fine particles (clay and silt) from wells with ID 1.9-10.16 cm for the analysis of mineralogical and geochemical composition and microbial community during the same period. Our results demonstrated that the surge block method provided a cost-effective approach for both well rehabilitation and frequent solid sampling at the same location.

  View details for DOI 10.1016/j.watres.2013.08.033

  View details for PubMedID 24070865

• Hydraulic conductivity imaging from 3-D transient hydraulic tomography at several pumping/observation densities WATER RESOURCES RESEARCH Cardiff, M., Barrash, W., Kitanidis, P. K. 2013; 49 (11): 7311-7326

  View details for DOI 10.1002/wrcr.20519

  View details for Web of Science ID 000328683800010

• Bayesian inversion with total variation prior for discrete geologic structure identification WATER RESOURCES RESEARCH Lee, J., Kitanidis, P. K. 2013; 49 (11): 7658-7669

  View details for DOI 10.1002/2012WR013431

  View details for Web of Science ID 000328683800036

• On the importance of diffusion and compound-specific mixing for groundwater transport: An investigation from pore to field scale. Journal of contaminant hydrology Rolle, M., Chiogna, G., Hochstetler, D. L., Kitanidis, P. K. 2013; 153: 51-68

  Abstract

  Mixing processes significantly affect and limit contaminant transport and transformation rates in the subsurface. The correct quantification of mixing in groundwater systems must account for diffusion, local-scale dispersion and the flow variability in heterogeneous flow fields (e.g., flow-focusing in high-conductivity and de-focusing in low-conductivity zones). Recent results of multitracer laboratory experiments revealed the significant effect of compound-specific diffusive properties on the physical displacement of dissolved species across a representative range of groundwater flow velocities. The goal of this study is to investigate the role of diffusion and compound-specific mixing for solute transport across a range of scales including: (i) pore-scale (~10(-2)m), (ii) laboratory bench-scale (~10(0)m) and (iii) field-scale (~10(2)m). We investigate both conservative and mixing-controlled reactive transport using pore-scale modeling, flow-through laboratory experiments and simulations, and field-scale numerical modeling of complex heterogeneous hydraulic conductivity fields with statistical properties similar to the ones reported for the extensively investigated Borden aquifer (Ontario, Canada) and Columbus aquifer (Mississippi, USA, also known as MADE site). We consider different steady-state and transient transport scenarios. For the conservative cases we use as a metric of mixing the exponential of the Shannon entropy to quantify solute dilution either in a given volume (dilution index) or in a given solute flux (flux-related dilution index). The decrease in the mass and the mass-flux of the contaminant plumes is evaluated to quantify reactive mixing. The results show that diffusive processes, occurring at the small-scale of a pore channel, strongly affect conservative and reactive solute transport at larger macroscopic scales. The outcomes of our study illustrate the need to consider and properly account for compound-specific diffusion and mixing limitations in order to accurately describe and predict conservative and reactive transport in porous media.

  View details for DOI 10.1016/j.jconhyd.2013.07.006

  View details for PubMedID 23994908

• Aquifer heterogeneity characterization with oscillatory pumping: Sensitivity analysis and imaging potential WATER RESOURCES RESEARCH Cardiff, M., Bakhos, T., Kitanidis, P. K., Barrash, W. 2013; 49 (9): 5395-5410

  View details for DOI 10.1002/wrcr.20356

  View details for Web of Science ID 000325991100021

• Stochastic cost optimization of DNAPL remediation - Field application ENVIRONMENTAL MODELLING & SOFTWARE Kim, U., Parker, J., Kitanidis, P., Cardiff, M., Liu, X., Gillie, J. 2013; 46: 12-20

  View details for DOI 10.1016/j.envsoft.2012.05.003

  View details for Web of Science ID 000321088500002

• Integration of Artificial Recharge and Recovery Systems for Impaired Water Sources in Urban Settings: Overcoming Current Limitations and Engineering Challenges ENVIRONMENTAL ENGINEERING SCIENCE Regnery, J., Lee, J., Kitanidis, P., Illangasekare, T., Sharp, J. O., Drewes, J. E. 2013; 30 (8): 409-420

  View details for DOI 10.1089/ees.2012.0186

  View details for Web of Science ID 000323206400003

• Use of on-site bioreactors to estimate the biotransformation rate of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) during activated sludge treatment. Chemosphere Rhoads, K. R., Rostkowski, K. H., Kitanidis, P. K., Criddle, C. S. 2013; 92 (6): 702-707

  Abstract

  Accurate rates are needed for models that predict the fate of xenobiotic chemicals and impact of inhibitors at full-scale wastewater treatment plants. On-site rates for aerobic biotransformation of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), a fluorinated repellent, were determined by continuously pumping mixed liquor from an aeration basin into two well-mixed acrylic bioreactors (4-L) operated in parallel. Known masses of N-EtFOSE and bromide were continuously added to the reactors. Reactor effluents were then monitored for bromide, N-EtFOSE, and metabolites of N-EtFOSE. Of the six transformation products reported in batch studies, only N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA) was detected in the effluents. Bromide addition to the reactors enabled rate estimates despite variations in flow rate. Pseudo-second order rate coefficients for the N-EtFOSE biotransformation to N-EtFOSAA, predicted using a dynamic model of the reactor system, were k=2.0 and 2.4Lg(-1)VSSd(-1) for the two reactors, which are slower than the rates previously obtained using batch reactors. Given the relatively slow rate of N-EtFOSE transformation, its sorption and volatilization may be important in wastewater processes. The methodology used in this study should be suitable for similar on-site rate assessments with other contaminants or inhibitors.

  View details for DOI 10.1016/j.chemosphere.2013.04.059

  View details for PubMedID 23711409

• Effects of compound-specific transverse mixing on steady-state reactive plumes: Insights from pore-scale simulations and Darcy-scale experiments ADVANCES IN WATER RESOURCES Hochstetler, D. L., Rolle, M., Chiogna, G., Haberer, C. M., Grathwohl, P., Kitanidis, P. K. 2013; 54: 1-10

  View details for DOI 10.1016/j.advwatres.2012.12.007

  View details for Web of Science ID 000317344300001

• Electrical Resistivity for Characterization and Infiltration Monitoring beneath a Managed Aquifer Recharge Pond VADOSE ZONE JOURNAL Mawer, C., Kitanidis, P., Pidlisecky, A., Knight, R. 2013; 12 (1)

  View details for DOI 10.2136/vzj2011.0203

  View details for Web of Science ID 000317713300006

• Fast Algorithms for Bayesian Inversion Computational Challenges in the Geosciences Ambikasaran, S., Saibaba, A. K., Darve, E. F., Kitanidis, Peter, K. 2013; 156: 101-142

  View details for DOI 10.1007/978-1-4614-7434-0_5

• A FLEXIBLE KRYLOV SOLVER FOR SHIFTED SYSTEMS WITH APPLICATION TO OSCILLATORY HYDRAULIC TOMOGRAPHY SIAM JOURNAL ON SCIENTIFIC COMPUTING Saibaba, A. K., Bakhos, T., Kitanidis, P. K. 2013; 35 (6): A3001-A3023

  View details for DOI 10.1137/120902690

  View details for Web of Science ID 000330028400025

• The behavior of effective rate constants for bimolecular reactions in an asymptotic transport regime JOURNAL OF CONTAMINANT HYDROLOGY Hochstetler, D. L., Kitanidis, P. K. 2013; 144 (1): 88-98

  Abstract

  Previous research has shown that rate constants measured in batch tests (κ) may over-predict the amount of product formation when used in continuum models, and that these rate constants are often much greater than effective ones (κ(eff)) determined from upscaling studies. However, there is evidence that mixing is more important than the rate constants when using upscaled models. We use a numerical two-dimensional pore-scale porous medium with an approach similar to an experimental column test, and focus on the scenario of the displacement and mixing of two solutions with irreversible bimolecular reactions. Break-through curves of multiple cross-sectional averaged concentrations are analyzed for conservative and reactive transport, as well as the segregation of reactant species along the cross-sections. We compute effective parameters for the continuum scale in order to better understand the impact of using intrinsic rate constants in upscaled models. For a range of Damköhler numbers (Da), we compute effective reaction rate parameters and a reaction effectiveness factor; the latter is described by an empirical formula that depends on the Damköhler number and captures the upscaled system behavior. Our pore-scale results also confirm the segregation concept advanced by Kapoor et al. (1997). We find that for Da>1, κ(eff)<κ, and yet the relative difference in total mass transformation between the pore-scale simulation and what is predicted by the upscaled continuum model using κ is about 10%. The explanation for this paradox is that the early transition of the regime from rate-limited to mixing-limited results in a model that is relatively insensitive to the rate constant because mixing controls the availability of reactants. Thus, the reaction-rate parameter used in the model has limited influence on the rate of product computed.

  View details for DOI 10.1016/j.jconhyd.2012.10.002

  View details for Web of Science ID 000313994800007

  View details for PubMedID 23159763

• Stochastic cost optimization of DNAPL remediation - Method description and sensitivity study ENVIRONMENTAL MODELLING & SOFTWARE Parker, J., Kim, U., Kitanidis, P., Cardiff, M., Liu, X., Beyke, G. 2012; 38: 74-88

  View details for DOI 10.1016/j.envsoft.2012.05.002

  View details for Web of Science ID 000308971400008

• Applicability of the Dual-Domain Model to Nonaggregated Porous Media GROUND WATER Liu, Y., Kitanidis, P. K. 2012; 50 (6): 927-934

  Abstract

  More theoretical analysis is needed to investigate why a dual-domain model often works better than the classical advection-dispersion (AD) model in reproducing observed breakthrough curves for relatively homogeneous porous media, which do not contain distinct dual domains. Pore-scale numerical experiments presented here reveal that hydrodynamics create preferential flow paths that occupy a small part of the domain but where most of the flow takes place. This creates a flow-dependent configuration, where the total domain consists of a mobile and an immobile domain. Mass transfer limitations may result in nonequilibrium, or significant differences in concentration, between the apparent mobile and immobile zones. When the advection timescale is smaller than the diffusion timescale, the dual-domain mass transfer (DDMT) model better captures the tailing in the breakthrough curve. Moreover, the model parameters (mobile porosity, mean solute velocity, dispersivity, and mass transfer coefficient) demonstrate nonlinear dependency on mean fluid velocity. The studied case also shows that when the Peclet number, Pe, is large enough, the mobile porosity approaches a constant, and the mass transfer coefficient can be approximated as proportional to mean fluid velocity. Based on detailed analysis at the pore scale, this paper provides a physical explanation why these model parameters vary in certain ways with Pe. In addition, to improve prediction in practical applications, we recommend conducting experiments for parameterization of the DDMT model at a velocity close to that of the relevant field sites, or over a range of velocities that may allow a better parameterization.

  View details for DOI 10.1111/j.1745-6584.2011.00909.x

  View details for Web of Science ID 000310729100015

  View details for PubMedID 22276634

• Mixing, entropy and reactive solute transport GEOPHYSICAL RESEARCH LETTERS Chiogna, G., Hochstetler, D. L., Bellin, A., Kitanidis, P. K., Rolle, M. 2012; 39

  View details for DOI 10.1029/2012GL053295

  View details for Web of Science ID 000310345100003

• Application of Hierarchical Matrices to Linear Inverse Problems in Geostatistics OIL & GAS SCIENCE AND TECHNOLOGY-REVUE D IFP ENERGIES NOUVELLES Saibaba, A. K., Ambikasaran, S., Li, J. Y., Kitanidis, P. K., Darve, E. F. 2012; 67 (5): 857-875

  View details for DOI 10.2516/ogst/2012064

  View details for Web of Science ID 000314141700010

• Experimental Investigation and Pore-Scale Modeling Interpretation of Compound-Specific Transverse Dispersion in Porous Media TRANSPORT IN POROUS MEDIA Rolle, M., Hochstetler, D., Chiogna, G., Kitanidis, P. K., Grathwohl, P. 2012; 93 (3): 347-362

  View details for DOI 10.1007/s11242-012-9953-8

  View details for Web of Science ID 000305225500001

• A field proof-of-concept of aquifer imaging using 3-D transient hydraulic tomography with modular, temporarily-emplaced equipment WATER RESOURCES RESEARCH Cardiff, M., Barrash, W., Kitanidis, P. K. 2012; 48

  View details for DOI 10.1029/2011WR011704

  View details for Web of Science ID 000304253700007

• Efficient methods for large-scale linear inversion using a geostatistical approach WATER RESOURCES RESEARCH Saibaba, A. K., Kitanidis, P. K. 2012; 48

  View details for DOI 10.1029/2011WR011778

  View details for Web of Science ID 000304253100002

• Value of Information as a Context-Specific Measure of Uncertainty in Groundwater Remediation WATER RESOURCES MANAGEMENT Liu, X., Lee, J., Kitanidis, P. K., Parker, J., Kim, U. 2012; 26 (6): 1513-1535

  View details for DOI 10.1007/s11269-011-9970-3

  View details for Web of Science ID 000302283200006

• Cost Optimization of DNAPL Remediation at Dover Air Force Base Site GROUND WATER MONITORING AND REMEDIATION Lee, J., Liu, X., Kitanidis, P. K., Kim, U., Parker, J., Bloom, A., Lyon, R. 2012; 32 (2): 48-56

  View details for DOI 10.1111/j.1745-6592.2011.01382.x

  View details for Web of Science ID 000303595600004

• Generalized priors in Bayesian inversion problems ADVANCES IN WATER RESOURCES Kitanidis, P. K. 2012; 36: 3-10

  View details for DOI 10.1016/j.advwatres.2011.05.005

  View details for Web of Science ID 000299971900002

• TRANSPORT AND MIXING DELIVERY AND MIXING IN THE SUBSURFACE: PROCESSES AND DESIGN PRINCIPLES FOR IN SITU REMEDIATION Kitanidis, P. K., Kitanidis, P. K., McCarty, P. L. 2012: 53–75

  View details for DOI 10.1007/978-1-4614-2239-6_3

  View details for Web of Science ID 000303409300003

• Delivery and Mixing in the Subsurface: Processes and Design Principles for In Situ Remediation INTRODUCTION DELIVERY AND MIXING IN THE SUBSURFACE: PROCESSES AND DESIGN PRINCIPLES FOR IN SITU REMEDIATION Kitanidis, P. K., McCarty, P. L., Kitanidis, P. K., McCarty, P. L. 2012: 1–6

  View details for DOI 10.1007/978-1-4614-2239-6_1

  View details for Web of Science ID 000303409300001

• Estimating Reaction Rate Coefficients Within a Travel-Time Modeling Framework GROUND WATER Gong, R., Lu, C., Wu, W., Cheng, H., Gu, B., Watson, D., Jardine, P. M., Brooks, S. C., Criddle, C. S., Kitanidis, P. K., Luo, J. 2011; 49 (2): 209-218

  Abstract

  A generalized, efficient, and practical approach based on the travel-time modeling framework is developed to estimate in situ reaction rate coefficients for groundwater remediation in heterogeneous aquifers. The required information for this approach can be obtained by conducting tracer tests with injection of a mixture of conservative and reactive tracers and measurements of both breakthrough curves (BTCs). The conservative BTC is used to infer the travel-time distribution from the injection point to the observation point. For advection-dominant reactive transport with well-mixed reactive species and a constant travel-time distribution, the reactive BTC is obtained by integrating the solutions to advective-reactive transport over the entire travel-time distribution, and then is used in optimization to determine the in situ reaction rate coefficients. By directly working on the conservative and reactive BTCs, this approach avoids costly aquifer characterization and improves the estimation for transport in heterogeneous aquifers which may not be sufficiently described by traditional mechanistic transport models with constant transport parameters. Simplified schemes are proposed for reactive transport with zero-, first-, nth-order, and Michaelis-Menten reactions. The proposed approach is validated by a reactive transport case in a two-dimensional synthetic heterogeneous aquifer and a field-scale bioremediation experiment conducted at Oak Ridge, Tennessee. The field application indicates that ethanol degradation for U(VI)-bioremediation is better approximated by zero-order reaction kinetics than first-order reaction kinetics.

  View details for DOI 10.1111/j.1745-6584.2010.00683.x

  View details for Web of Science ID 000287584100015

  View details for PubMedID 20132330

• Increasing Confidence in Mass Discharge Estimates Using Geostatistical Methods GROUND WATER Cai, Z., Wilson, R. D., Cardiff, M. A., Kitanidis, P. K. 2011; 49 (2): 197-208

  Abstract

  Mass discharge is one metric rapidly gaining acceptance for assessing the performance of in situ groundwater remediation systems. Multilevel sampling transects provide the data necessary to make such estimates, often using the Thiessen Polygon method. This method, however, does not provide a direct estimate of uncertainty. We introduce a geostatistical mass discharge estimation approach that involves a rigorous analysis of data spatial variability and selection of an appropriate variogram model. High-resolution interpolation was applied to create a map of measurements across a transect, and the magnitude and uncertainty of mass discharge were quantified by conditional simulation. An important benefit of the approach is quantified uncertainty of the mass discharge estimate. We tested the approach on data from two sites monitored using multilevel transects. We also used the approach to explore the effect of lower spatial monitoring resolution on the accuracy and uncertainty of mass discharge estimates. This process revealed two important findings: (1) appropriate monitoring resolution is that which yielded an estimate comparable with the full dataset value, and (2) high-resolution sampling yields a more representative spatial data structure descriptor, which can then be used via conditional simulation to make subsequent mass discharge estimates from lower resolution sampling of the same transect. The implication of the latter is that a high-resolution multilevel transect needs to be sampled only once to obtain the necessary spatial data descriptor for a contaminant plume exhibiting minor temporal variability, and thereafter less spatially intensely to reduce costs.

  View details for DOI 10.1111/j.1745-6584.2010.00709.x

  View details for Web of Science ID 000287584100014

  View details for PubMedID 20477878

• Large-scale inverse modeling with an application in hydraulic tomography WATER RESOURCES RESEARCH Liu, X., Kitanidis, P. K. 2011; 47

  View details for DOI 10.1029/2010WR009144

  View details for Web of Science ID 000287037300002

• Effects of model formulation and calibration data on uncertainty in dense nonaqueous phase liquids source dissolution predictions WATER RESOURCES RESEARCH Parker, J. C., Kim, U., Widdowson, M., Kitanidis, P., Gentry, R. 2010; 46

  View details for DOI 10.1029/2010WR009361

  View details for Web of Science ID 000285016700004

• Assessment of the Effectiveness of a Constructed Compound Channel River Restoration Project on an Incised Stream JOURNAL OF HYDRAULIC ENGINEERING-ASCE MacWilliams, M. L., Tompkins, M. R., Street, R. L., Kondolf, G. M., Kitanidis, P. K. 2010; 136 (12): 1042-1052

  View details for DOI 10.1061/(ASCE)HY.1943-7900.0000196

  View details for Web of Science ID 000284276300008

• Fitting Data Under Omnidirectional Noise: A Probabilistic Method for Inferring Petrophysical and Hydrologic Relations MATHEMATICAL GEOSCIENCES Cardiff, M., Kitanidis, P. K. 2010; 42 (8): 877-909

  View details for DOI 10.1007/s11004-010-9301-x

  View details for Web of Science ID 000283087600001

• Significant Association between Sulfate-Reducing Bacteria and Uranium-Reducing Microbial Communities as Revealed by a Combined Massively Parallel Sequencing-Indicator Species Approach APPLIED AND ENVIRONMENTAL MICROBIOLOGY Cardenas, E., Wu, W., Leigh, M. B., Carley, J., Carroll, S., Gentry, T., Luo, J., Watson, D., Gu, B., Ginder-Vogel, M., Kitanidis, P. K., Jardine, P. M., Zhou, J., Criddle, C. S., Marsh, T. L., Tiedje, J. M. 2010; 76 (20): 6778-6786

  Abstract

  Massively parallel sequencing has provided a more affordable and high-throughput method to study microbial communities, although it has mostly been used in an exploratory fashion. We combined pyrosequencing with a strict indicator species statistical analysis to test if bacteria specifically responded to ethanol injection that successfully promoted dissimilatory uranium(VI) reduction in the subsurface of a uranium contamination plume at the Oak Ridge Field Research Center in Tennessee. Remediation was achieved with a hydraulic flow control consisting of an inner loop, where ethanol was injected, and an outer loop for flow-field protection. This strategy reduced uranium concentrations in groundwater to levels below 0.126 μM and created geochemical gradients in electron donors from the inner-loop injection well toward the outer loop and downgradient flow path. Our analysis with 15 sediment samples from the entire test area found significant indicator species that showed a high degree of adaptation to the three different hydrochemical-created conditions. Castellaniella and Rhodanobacter characterized areas with low pH, heavy metals, and low bioactivity, while sulfate-, Fe(III)-, and U(VI)-reducing bacteria (Desulfovibrio, Anaeromyxobacter, and Desulfosporosinus) were indicators of areas where U(VI) reduction occurred. The abundance of these bacteria, as well as the Fe(III) and U(VI) reducer Geobacter, correlated with the hydraulic connectivity to the substrate injection site, suggesting that the selected populations were a direct response to electron donor addition by the groundwater flow path. A false-discovery-rate approach was implemented to discard false-positive results by chance, given the large amount of data compared.

  View details for DOI 10.1128/AEM.01097-10

  View details for Web of Science ID 000282595100009

  View details for PubMedID 20729318

  View details for PubMedCentralID PMC2953039

• Parameter estimation in nonlinear environmental problems STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT Liu, X., Cardiff, M. A., Kitanidis, P. K. 2010; 24 (7): 1003-1022

  View details for DOI 10.1007/s00477-010-0395-y

  View details for Web of Science ID 000284070200006

• Estimating kinetic mass transfer by resting-period measurements in flow-interruption tracer tests JOURNAL OF CONTAMINANT HYDROLOGY Gong, R., Lu, C., Wu, W., Cheng, H., Gu, B., Watson, D. B., Criddle, C. S., Kitanidis, P. K., Brooks, S. C., Jardine, P. M., Luo, J. 2010; 117 (1-4): 37-45

  Abstract

  Flow-interruption tracer test is an effective approach to identify kinetic mass transfer processes for solute transport in subsurface media. By switching well pumping and resting, one may alter the dominant transport mechanism and generate special concentration patterns for identifying kinetic mass transfer processes. In the present research, we conducted three-phase (i.e., pumping, resting, and pumping) field-scale flow-interruption tracer tests using a conservative tracer bromide in a multiple-well system installed at the US Department of Energy Site, Oak Ridge, TN. A novel modeling approach based on the resting-period measurements was developed to estimate the mass transfer parameters. This approach completely relied on the measured breakthrough curves without requiring detailed aquifer characterization and solving transport equations in nonuniform, transient flow fields. Additional measurements, including hydraulic heads and tracer concentrations in large pumping wells, were taken to justify the assumption that mass transfer processes dominated concentration change during resting periods. The developed approach can be conveniently applied to any linear mass transfer model. Both first-order and multirate mass transfer models were applied to analyze the breakthrough curves at various monitoring wells. The multirate mass transfer model was capable of jointly fitting breakthrough curve behavior, showing the effectiveness and flexibility for incorporating aquifer heterogeneity and scale effects in upscaling effective mass transfer models.

  View details for DOI 10.1016/j.jconhyd.2010.06.003

  View details for Web of Science ID 000282252600004

  View details for PubMedID 20638152

• Effects of Nitrate on the Stability of Uranium in a Bioreduced Region of the Subsurface ENVIRONMENTAL SCIENCE & TECHNOLOGY Wu, W., Carley, J., Green, S. J., Luo, J., Kelly, S. D., Van Nostrand, J., Lowe, K., Mehlhorn, T., Carroll, S., Boonchayanant, B., Loefller, F. E., Watson, D., Kemner, K. M., Zhou, J., Kitanidis, P. K., Kostka, J. E., Jardine, P. M., Criddle, C. S. 2010; 44 (13): 5104-5111

  Abstract

  The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H(2)S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 microM.

  View details for DOI 10.1021/es1000837

  View details for PubMedID 20527772

• Stochastic Cost Optimization of Multistrategy DNAPL Site Remediation GROUND WATER MONITORING AND REMEDIATION Parker, J., Kim, U., Kitanidis, P. K., Cardiff, M., Liu, X. 2010; 30 (3): 65-78

  View details for DOI 10.1111/j1745-6592.2010.001287.x

  View details for Web of Science ID 000281063400006

• Cost optimization of DNAPL source and plume remediation under uncertainty using a semi-analytic model JOURNAL OF CONTAMINANT HYDROLOGY Cardiff, M., Liu, X., Kitanidis, P. K., Parker, J., Kim, U. 2010; 113 (1-4): 25-43

  Abstract

  Dense non-aqueous phase liquid (DNAPL) spills represent a potential long-term source of aquifer contamination, and successful low-cost remediation may require a combination of both plume management and source treatment. In addition, substantial uncertainty exists in many of the parameters that control field-scale behavior of DNAPL sources and plumes. For these reasons, cost optimization of DNAPL cleanup needs to consider multiple treatment options and their associated costs while also gauging the influence of prediction uncertainty on expected costs. In this paper, we present a management methodology for field-scale DNAPL source and plume management under uncertainty. Using probabilistic methods, historical data and prior information are combined to produce a set of equally likely realizations of true field conditions (i.e., parameter sets). These parameter sets are then used in a simulation-optimization framework to produce DNAPL cleanup solutions that have the lowest possible expected net present value (ENPV) cost and that are suitably cautious in the presence of high uncertainty. For simulation, we utilize a fast-running semi-analytic field-scale model of DNAPL source and plume evolution that also approximates the effects of remedial actions. The degree of model prediction uncertainty is gauged using a restricted maximum likelihood method, which helps to produce suitably cautious remediation strategies. We test our methodology on a synthetic field-scale problem with multiple source architectures, for which source zone thermal treatment and electron donor injection are considered as remedial actions. The lowest cost solution found utilizes a combination of source and plume remediation methods, and is able to successfully meet remediation constraints for a majority of possible scenarios. Comparisons with deterministic optimization results show that not taking into account uncertainty can result in optimization strategies that are not aggressive enough and result in greater overall total cost.

  View details for DOI 10.1016/j.jconhyd.2009.11.004

  View details for Web of Science ID 000276766000002

  View details for PubMedID 20185203

• Effects of kinetic mass transfer and transient flow conditions on widening mixing zones in coastal aquifers WATER RESOURCES RESEARCH Lu, C., Kitanidis, P. K., Luo, J. 2009; 45

  View details for DOI 10.1029/2008WR007643

  View details for Web of Science ID 000272448400001

• Bayesian inversion for facies detection: An extensible level set framework WATER RESOURCES RESEARCH Cardiff, M., Kitanidis, P. K. 2009; 45

  View details for DOI 10.1029/2008WR007675

  View details for Web of Science ID 000270945800001

• Geostatistical inversing for large-contrast transmissivity fields STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT Zanini, A., Kitanidis, P. K. 2009; 23 (5): 565-577

  View details for DOI 10.1007/s00477-008-0241-7

  View details for Web of Science ID 000266394700003

• A Potential-Based Inversion of Unconfined Steady-State Hydraulic Tomography GROUND WATER Cardiff, M., Barrash, W., Kitanidis, P. K., Malama, B., Revil, A., Straface, S., Rizzo, E. 2009; 47 (2): 259-270

  Abstract

  The importance of estimating spatially variable aquifer parameters such as transmissivity is widely recognized for studies in resource evaluation and contaminant transport. A useful approach for mapping such parameters is inverse modeling of data from series of pumping tests, that is, via hydraulic tomography. This inversion of field hydraulic tomographic data requires development of numerical forward models that can accurately represent test conditions while maintaining computational efficiency. One issue this presents is specification of boundary and initial conditions, whose location, type, and value may be poorly constrained. To circumvent this issue when modeling unconfined steady-state pumping tests, we present a strategy that analyzes field data using a potential difference method and that uses dipole pumping tests as the aquifer stimulation. By using our potential difference approach, which is similar to modeling drawdown in confined settings, we remove the need for specifying poorly known boundary condition values and natural source/sink terms within the problem domain. Dipole pumping tests are complementary to this strategy in that they can be more realistically modeled than single-well tests due to their conservative nature, quick achievement of steady state, and the insensitivity of near-field response to far-field boundary conditions. After developing the mathematical theory, our approach is first validated through a synthetic example. We then apply our method to the inversion of data from a field campaign at the Boise Hydrogeophysical Research Site. Results from inversion of nine pumping tests show expected geologic features, and uncertainty bounds indicate that hydraulic conductivity is well constrained within the central site area.

  View details for DOI 10.1111/j.1745-6584.2008.00541.x

  View details for Web of Science ID 000263600800013

  View details for PubMedID 19178572

• Efficient solution of nonlinear, underdetermined inverse problems with a generalized PDE model COMPUTERS & GEOSCIENCES Cardiff, M., Kitanidis, P. K. 2008; 34 (11): 1480-1491

  View details for DOI 10.1016/j.cageo.2008.01.013

  View details for Web of Science ID 000260287400007

• An interactive Bayesian geostatistical inverse protocol for hydraulic tomography WATER RESOURCES RESEARCH Fienen, M. N., Clemo, T., Kitanidis, P. K. 2008; 44

  View details for DOI 10.1029/2007WR006730

  View details for Web of Science ID 000258003800002

• Microbial communities in contaminated sediments, associated with bioremediation of uranium to submicromolar levels APPLIED AND ENVIRONMENTAL MICROBIOLOGY Cardenas, E., Wu, W., Leigh, M. B., Carley, J., Carroll, S., Gentry, T., Luo, J., Watson, D., Gu, B., Ginder-Vogel, M., Kitanidis, P. K., Jardine, P. M., Zhou, J., Criddle, C. S., Marsh, T. L., Tiedje, J. A. 2008; 74 (12): 3718-3729

  Abstract

  Microbial enumeration, 16S rRNA gene clone libraries, and chemical analysis were used to evaluate the in situ biological reduction and immobilization of uranium(VI) in a long-term experiment (more than 2 years) conducted at a highly uranium-contaminated site (up to 60 mg/liter and 800 mg/kg solids) of the U.S. Department of Energy in Oak Ridge, TN. Bioreduction was achieved by conditioning groundwater above ground and then stimulating growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria in situ through weekly injection of ethanol into the subsurface. After nearly 2 years of intermittent injection of ethanol, aqueous U levels fell below the U.S. Environmental Protection Agency maximum contaminant level for drinking water and groundwater (<30 microg/liter or 0.126 microM). Sediment microbial communities from the treatment zone were compared with those from a control well without biostimulation. Most-probable-number estimations indicated that microorganisms implicated in bioremediation accumulated in the sediments of the treatment zone but were either absent or in very low numbers in an untreated control area. Organisms belonging to genera known to include U(VI) reducers were detected, including Desulfovibrio, Geobacter, Anaeromyxobacter, Desulfosporosinus, and Acidovorax spp. The predominant sulfate-reducing bacterial species were Desulfovibrio spp., while the iron reducers were represented by Ferribacterium spp. and Geothrix spp. Diversity-based clustering revealed differences between treated and untreated zones and also within samples of the treated area. Spatial differences in community structure within the treatment zone were likely related to the hydraulic pathway and to electron donor metabolism during biostimulation.

  View details for DOI 10.1128/AEM.02308-07

  View details for Web of Science ID 000256899700013

  View details for PubMedID 18456853

• Estimating first-order reaction rate coefficient for transport with nonequilibrium linear mass transfer in heterogeneous media JOURNAL OF CONTAMINANT HYDROLOGY Luo, J., Wu, W., Carley, J., Fienen, M. N., Cheng, H., Watson, D., Criddle, C. S., Jardine, P. M., Kitanidis, P. K. 2008; 98 (1-2): 50-60

  Abstract

  A travel-time based approach is developed for estimating first-order reaction rate coefficients for transport with nonequilibrium linear mass transfer in heterogeneous media. Tracer transport in the mobile domain is characterized by a travel-time distribution, and mass transfer rates are described by a convolution product of concentrations in the mobile domain and a memory function rather than predefining the mass transfer model. A constant first-order reaction is assumed to occur only in the mobile domain. Analytical solutions in Laplace domain can be derived for both conservative and reactive breakthrough curves (BTCs). Temporal-moment analyses are presented by using the first and second moments of conservative and reactive BTCs and the mass consumption of the reactant for an inverse Gaussian travel-time distribution. In terms of moment matching, there is no need for one to specify the mass transfer model. With the same capacity ratio and the mean retention time, all mass transfer models will lead to the same moment-derived reaction rate coefficients. In addition, the consideration of mass transfer generally yields larger estimations of the reaction rate coefficient than models ignoring mass transfer. Furthermore, the capacity ratio and the mean retention time have opposite influences on the estimation of the reaction rate coefficient: the first-order reaction rate coefficient is positively linearly proportional to the capacity ratio, but negatively linearly proportional to the mean retention time.

  View details for DOI 10.1016/j.jconhyd.2008.03.002

  View details for Web of Science ID 000256852300005

  View details for PubMedID 18440665

• Growth and cometabolic reduction kinetics of a uranium- and sulfate-reducing Desulfovibrio Clostridia mixed culture: Temperature effects BIOTECHNOLOGY AND BIOENGINEERING Boonchayaanant, B., Kitanidis, P. K., Criddle, C. S. 2008; 99 (5): 1107-1119

  Abstract

  Bioremediation of contaminated soils and aquifers is subject to spatial and temporal temperature changes that can alter the kinetics of key microbial processes. This study quantifies temperature effects on the kinetics of an ethanol-fed sulfate-reducing mixed culture derived from a uranium-contaminated aquifer subject to seasonal temperature fluctuations. The mixed culture contains Desulfovibrio sp. and a Clostridia-like organism. Rates of growth, ethanol utilization, decay, and uranium reduction decreased with decreasing temperature. No significant uranium reduction was observed at 10 degrees C. While both Monod saturation kinetics and pseudo second-order kinetics adequately described the rates of growth and utilization of electron donor (ethanol), model parameters for the pseudo second-order expression had smaller uncertainties. Uranium reduction kinetics were best described by pseudo second-order kinetics modified to include a term for inactivation/death of cells.

  View details for DOI 10.1002/bit.21670

  View details for Web of Science ID 000253925800007

  View details for PubMedID 17929318

• Effective reaction parameters for mixing controlled reactions in heterogeneous media WATER RESOURCES RESEARCH Luo, J., Dentz, M., Carrera, J., Kitanidis, P. 2008; 44 (2)

  View details for DOI 10.1029/2006WR005658

  View details for Web of Science ID 000253070600001

• Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater 3rd European Bioremediation Conference McCarty, P. L., Chu, M., Kitanidis, P. K. ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER. 2007: 276–82

  View details for DOI 10.1016/j.ejsobi.2007.03.004

  View details for Web of Science ID 000251684000003

• Inhibition of a U(VI)- and sulfate-reducing consortia by U(VI) ENVIRONMENTAL SCIENCE & TECHNOLOGY Nyman, J. L., Wu, H., Gentile, M. E., Kitanidis, P. K., Criddle, C. S. 2007; 41 (18): 6528-6533

  Abstract

  The stimulation of microbial U(VI) reduction is currently being investigated as a means to reduce uranium's mobility in groundwater, but little is known about the concentration at which U(VI) might inhibit microbial activity, or the effect of U(VI) on bacterial community structure. We investigated these questions with an ethanol-fed U(VI)- and sulfate-reducing enrichment developed from sediment from the site of an ongoing field biostimulation experiment at Area 3 of the Oak Ridge Field Research Center (FRC). Sets of triplicate enrichments were spiked with increasing concentrations of U(VI) (from 49 microm to 9.2 mM). As the U(VI) concentration increased to 224 microM, the culture's production of acetate from ethanol slowed, and at or above 1.6 mM U(VI) little acetate was produced over the time frame of the experiment. An uncoupling inhibition model was applied to the data, and the inhibition coefficient for U(VI), Ku, was found to be approximately 100 microM U(VI), or 24 mg/L, indicating the inhibitory effect is relevant at highly contaminated sites. Microbial community structure at the conclusion of the experiment was analyzed with terminal restriction fragment length polymorphism (T-RFLP) analysis. T-RFs associated with Desulfovibrio-like organisms decreased in relative abundance with increasing U(VI) concentration, whereas Clostridia-like T-RFs increased.

  View details for DOI 10.1021/es062985b

  View details for Web of Science ID 000249500700039

  View details for PubMedID 17948804

• Breakthrough curve tailing in a dipole flow field WATER RESOURCES RESEARCH Luo, J., Dentz, M., Cirpka, O. A., Kitanidis, P. K. 2007; 43 (9)

  View details for DOI 10.1029/2006WR005600

  View details for Web of Science ID 000249374000002

• In situ bioreduction of uranium (VI) to submicromolar levels and reoxidation by dissolved oxygen ENVIRONMENTAL SCIENCE & TECHNOLOGY Wu, W., Carley, J., Luo, J., Ginder-Vogel, M. A., Cardenas, E., Leigh, M. B., Hwang, C., Kelly, S. D., Ruan, C., Wu, L., Van Nostrand, J., Gentry, T., Lowe, K., Mehlhorn, T., Carroll, S., Luo, W., Fields, M. W., Gu, B., Watson, D., Kemner, K. M., Marsh, T., Tiedje, J., Zhou, J., Fendorf, S., Kitanidis, P. K., Jardine, P. M., Criddle, C. S. 2007; 41 (16): 5716-5723

  Abstract

  Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 microM uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agengy maximum contaminant limit (MCL) for drinking water (< 30/microg L(-1) or 0.126 microM). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L(-1)) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from < 0.13 to 2.0 microM at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. Atthe completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 microM. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp.

  View details for DOI 10.1021/es062657b

  View details for Web of Science ID 000248886000026

  View details for PubMedID 17874778

• Modeling in-situ uranium(VI) bioreduction by sulfate-reducing bacteria JOURNAL OF CONTAMINANT HYDROLOGY Luo, J., Weber, F., Cirpka, O. A., Wu, W., Nyman, J. L., Carley, J., Jardine, P. M., Criddle, C. S., Kitanidis, P. K. 2007; 92 (1-2): 129-148

  Abstract

  We present a travel-time based reactive transport model to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI). The model considers aquatic equilibrium chemistry of uranium and other groundwater constituents, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). Kinetic sorption/desorption of U(VI) is characterized by mass transfer between stagnant micro-pores and mobile flow zones. The model describes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results show that (1) the presence of nitrate inhibits U(VI) reduction at the site; (2) the fitted effective rate of in-situ U(VI) reduction is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption, which affects U(VI) bioavailability at the site, is strongly controlled by kinetics; (4) both pH and bicarbonate concentration significantly influence the sorption/desorption of U(VI), which therefore cannot be characterized by empirical isotherms; and (5) calcium-uranyl-carbonate complexes significantly influence the model performance of U(VI) reduction.

  View details for DOI 10.1016/j.jconhyd.2007.01.004

  View details for Web of Science ID 000247415600008

  View details for PubMedID 17291626

• Dependence of lumped mass transfer coefficient on scale and reactions kinetics for biologically enhanced NAPL dissolution ADVANCES IN WATER RESOURCES Chu, M., Kitanidis, P. K., McCarty, P. L. 2007; 30 (6-7): 1618-1629

  View details for DOI 10.1016/j.advwatres.2006.06.016

  View details for Web of Science ID 000246902300017

• Analyzing bank filtration by deconvoluting time series of electric conductivity GROUND WATER Cirpka, O. A., Fienen, M. N., Hofer, M., Hoehn, E., Tessarini, A., Kipfer, R., Kitanidis, P. K. 2007; 45 (3): 318-328

  Abstract

  Knowing the travel-time distributions from infiltrating rivers to pumping wells is important in the management of alluvial aquifers. Commonly, travel-time distributions are determined by releasing a tracer pulse into the river and measuring the breakthrough curve in the wells. As an alternative, one may measure signals of a time-varying natural tracer in the river and in adjacent wells and infer the travel-time distributions by deconvolution. Traditionally this is done by fitting a parametric function such as the solution of the one-dimensional advection-dispersion equation to the data. By choosing a certain parameterization, it is impossible to determine features of the travel-time distribution that do not follow the general shape of the parameterization, i.e., multiple peaks. We present a method to determine travel-time distributions by nonparametric deconvolution of electric-conductivity time series. Smoothness of the inferred transfer function is achieved by a geostatistical approach, in which the transfer function is assumed as a second-order intrinsic random time variable. Nonnegativity is enforced by the method of Lagrange multipliers. We present an approach to directly compute the best nonnegative estimate and to generate sets of plausible solutions. We show how the smoothness of the transfer function can be estimated from the data. The approach is applied to electric-conductivity measurements taken at River Thur, Switzerland, and five wells in the adjacent aquifer, but the method can also be applied to other time-varying natural tracers such as temperature. At our field site, electric-conductivity fluctuations appear to be an excellent natural tracer.

  View details for DOI 10.1111/j.1745-6584.2006.00293.x

  View details for Web of Science ID 000246030800010

  View details for PubMedID 17470121

• Hydraulic performance analysis of a multiple injection-extraction well system JOURNAL OF HYDROLOGY Luo, J., Wu, W., Carley, J., Ruan, C., Gu, B., Jardine, P. M., Criddle, C. S., Kitanidis, P. K. 2007; 336 (3-4): 294-302

  View details for DOI 10.1016/j.jhydrol.2007.01.002

  View details for Web of Science ID 000245656800005

• Flow convergence routing hypothesis for pool-riffle maintenance in alluvial rivers WATER RESOURCES RESEARCH MacWilliams, M. L., Wheaton, J. M., Pasternack, G. B., Street, R. L., Kitanidis, P. K. 2006; 42 (10)

  View details for DOI 10.1029/2005WR004391

  View details for Web of Science ID 000241870600001

• Temporal-moment matching for truncated breakthrough curves for step or step-pulse injection ADVANCES IN WATER RESOURCES Luo, J., Cirpka, O. A., Kitanidis, P. K. 2006; 29 (9): 1306-1313

  View details for DOI 10.1016/j.advwatrers.2005.10.005

  View details for Web of Science ID 000240178400004

• A Bayesian geostatistical transfer function approach to tracer test analysis WATER RESOURCES RESEARCH Fienen, M. N., Luo, J., Kitanidis, P. K. 2006; 42 (7)

  View details for DOI 10.1029/2005WR004576

  View details for Web of Science ID 000239492700001

• Experimental determination of transverse dispersivity in a helix and a cochlea WATER RESOURCES RESEARCH Benekos, I. D., Cirpka, O. A., Kitanidis, P. K. 2006; 42 (7)

  View details for DOI 10.1029/2005WR004712

  View details for Web of Science ID 000239221500003

• Pilot-scale in situ bioremedation of uranium in a highly contaminated aquifer. 2. Reduction of U(VI) and geochemical control of U(VI) bioavailability ENVIRONMENTAL SCIENCE & TECHNOLOGY Wu, W., Carley, J., Gentry, T., Ginder-Vogel, M. A., Fienen, M., Mehlhorn, T., Yan, H., Caroll, S., Pace, M. N., Nyman, J., Luo, J., Gentile, M. E., Fields, M. W., Hickey, R. F., Gu, B., Watson, D., Cirpka, O. A., Zhou, J., Fendorf, S., Kitanidis, P. K., Jardine, P. M., Criddle, C. S. 2006; 40 (12): 3986-3995

  Abstract

  In situ microbial reduction of soluble U(VI) to sparingly soluble U(IV) was evaluated at the site of the former S-3 Ponds in Area 3 of the U.S. Department of Energy Natural and Accelerated Bioremediation Research Field Research Center, Oak Ridge, TN. After establishing conditions favorable for bioremediation (Wu, et al. Environ. Sci. Technol. 2006, 40, 3988-3995), intermittent additions of ethanol were initiated within the conditioned inner loop of a nested well recirculation system. These additions initially stimulated denitrification of matrix-entrapped nitrate, but after 2 months, aqueous U levels fell from 5 to approximately 1 microM and sulfate reduction ensued. Continued additions sustained U(VI) reduction over 13 months. X-ray near-edge absorption spectroscopy (XANES) confirmed U(VI) reduction to U(IV) within the inner loop wells, with up to 51%, 35%, and 28% solid-phase U(IV) in sediment samples from the injection well, a monitoring well, and the extraction well, respectively. Microbial analyses confirmed the presence of denitrifying, sulfate-reducing, and iron-reducing bacteria in groundwater and sediments. System pH was generally maintained at less than 6.2 with low bicarbonate level (0.75-1.5 mM) and residual sulfate to suppress methanogenesis and minimize uranium mobilization. The bioavailability of sorbed U(VI) was manipulated by addition of low-level carbonate (< 5 mM) followed by ethanol (1-1.5 mM). Addition of low levels of carbonate increased the concentration of aqueous U, indicating an increased rate of U desorption due to formation of uranyl carbonate complexes. Upon ethanol addition, aqueous U(VI) levels fell, indicating that the rate of microbial reduction exceeded the rate of desorption. Sulfate levels simultaneously decreased, with a corresponding increase in sulfide. When ethanol addition ended but carbonate addition continued, soluble U levels increased, indicating faster desorption than reduction. When bicarbonate addition stopped, aqueous U levels decreased, indicating adsorption to sediments. Changes in the sequence of carbonate and ethanol addition confirmed that carbonate-controlled desorption increased bioavailability of U(VI) for reduction.

  View details for DOI 10.1021/es051960u

  View details for Web of Science ID 000238217200052

  View details for PubMedID 16830572

• Pilot-scale in situ bioremediation of uranium in a highly contaminated aquifer. 1. Conditioning of a treatment zone ENVIRONMENTAL SCIENCE & TECHNOLOGY Wu, W., Carley, J., Fienen, M., Mehlhorn, T., Lowe, K., Nyman, J., Luo, J., Gentile, M. E., Rajan, R., Wagner, D., Hickey, R. F., Gu, B., Watson, D., Cirpka, O. A., Kitanidis, P. K., Jardine, P. M., Criddle, C. S. 2006; 40 (12): 3978-3985

  Abstract

  To evaluate the potential for in situ bioremediation of U(VI) to sparingly soluble U(IV), we constructed a pilot test facility at Area 3 of the U.S. Department of Energy Natural and Accelerated Bioremediation Research (NABIR) Field Research Center (FRC) in Oak Ridge, TN. The facility is adjacent to the former S-3 Ponds which received trillions of liters of acidic plating wastes. High levels of uranium are present, with up to 800 mg kg(-1) in the soil and 84-210 microM in the groundwater. Ambient groundwater has a highly buffered pH of approximately 3.4 and high levels of aluminum (12-13 mM), calcium (22-25 mM), and nitrate (80-160 mM). Adjusting the pH of groundwater to approximately 5 within the aquifer would deposit extensive aluminum hydroxide precipitate. Calcium is present in the groundwater at levels that inhibit U(VI) reduction, but its removal by injection of a high pH solution would generate clogging precipitate. Nitrate also inhibits U(VI) reduction and is present at such high concentrations that its removal by in situ denitrification would generate large amounts of N2 gas and biomass. To establish and maintain hydraulic control, we installed a four well recirculation system parallel to geologic strike, with an inner loop nested within an outer loop. For monitoring, we drilled three boreholes perpendicular to strike across the inner loop and installed multilevel sampling tubes within them. A tracer pulse with clean water established travel times and connectivity between wells and enabled the assessment of contaminant release from the soil matrix. Subsequently, a highly conductive region of the subsurface was prepared for biostimulation by removing clogging agents and inhibitors and increasing pH. For 2 months, groundwater was pumped from the hydraulically conductive zone; treated to remove aluminum, calcium, and nitrate, and supplemented with tap water; adjusted to pH 4.3-4.5; then returned to the hydraulically conductive zone. This protocol removed most of the aqueous aluminum and calcium. The pH of the injected treated water was then increased to 6.0-6.3. With additional flushing, the pH of the extracted water gradually increased to 5.5-6.0, and nitrate concentrations fell to 0.5-1.0 mM. These conditions were judged suitable for biostimulation. In a companion paper (Wu et al., Environ. Sci. Technol. 2006, 40, 3978-3987), we describe the effects of ethanol addition on in situ denitrification and U(VI) reduction and immobilization.

  View details for DOI 10.1021/es051954y

  View details for Web of Science ID 000238217200051

  View details for PubMedID 16830571

• A nested-cell approach for in situ remediation GROUND WATER Luo, J., Wu, W. M., Fienen, M. N., Jardine, P. M., Mehlhorn, T. L., Watson, D. B., Cirpka, O. A., Criddle, C. S., Kitanidis, P. K. 2006; 44 (2): 266-274

  Abstract

  We characterize the hydraulics of an extraction-injection well pair in arbitrarily oriented regional flow by the recirculation ratio, area, and average residence time in the recirculation zone. Erratic regional flow conditions may compromise the performance of the reactor between a single well pair. We propose an alternative four-well system: two downgradient extraction and two upgradient injection wells creating an inner cell nested within an outer cell. The outer cell protects the inner cell from the influence of regional flow. Compared to a two-well system, the proposed four-well system has several advantages: (1) the recirculation ratio within the nested inner cell is less sensitive to the regional flow direction; (2) a transitional recirculation zone between the inner and outer cells can capture flow leakage from the inner cell, minimizing the release of untreated contaminants; and (3) the size of the recirculation zone and residence times can be better controlled within the inner cell by changing the pumping rates. The system is applied at the Field Research Center in Oak Ridge, Tennessee, where experiments on microbial in situ reduction of uranium (VI) are under way.

  View details for DOI 10.1111/j.1745-6584.2005.00106.x

  View details for Web of Science ID 000235730800021

  View details for PubMedID 16556208

• A parametric transfer function methodology for analyzing reactive transport in nonuniform flow JOURNAL OF CONTAMINANT HYDROLOGY Luo, J., Cirpka, O. A., Fienen, M. N., Wu, W. M., Mehlhorn, T. L., Carley, J., Jardine, P. M., Criddle, C. S., Kitanidis, P. K. 2006; 83 (1-2): 27-41

  Abstract

  We analyze reactive transport during in-situ bioremediation in a nonuniform flow field, involving multiple extraction and injection wells, by the method of transfer functions. Gamma distributions are used as parametric models of the transfer functions. Apparent parameters of classical transport models may be estimated from those of the gamma distributions by matching temporal moments. We demonstrate the method by application to measured data taken at a field experiment on bioremediation conducted in a multiple-well system in Oak Ridge, TN. Breakthrough curves (BTCs) of a conservative tracer (bromide) and a reactive compound (ethanol) are measured at multi-level sampling (MLS) wells and in extraction wells. The BTCs of both compounds are jointly analyzed to estimate the first-order degradation rate of ethanol. To quantify the tracer loss, we compare the approaches of using a scaling factor and a first-order decay term. Results show that by including a scaling factor both gamma distributions and inverse-Gaussian distributions (transfer functions according to the advection-dispersion equation) are suitable to approximate the transfer functions and estimate the reactive rate coefficients for both MLS and extraction wells. However, using a first-order decay term for tracer loss fails to describe the BTCs at the extraction well, which is affected by the nonuniform distribution of travel paths.

  View details for DOI 10.1016/j.jconhyd.2005.11.001

  View details for Web of Science ID 000234782000002

  View details for PubMedID 16337023

• Application of the complementary volume method to simulation of flows on an unstructured grid 16th International Offshore and Polar Engineering Conference (ISOPE 2006) Zhao, G., Kitanidis, P. K., Street, R. L. INTERNATIONAL SOCIETY OFFSHORE& POLAR ENGINEERS. 2006: 402–405

  View details for Web of Science ID 000240311500058

• A numerical study of surface-subsurface exchange processes at a riffle-pool pair in the Lahn River, Germany WATER RESOURCES RESEARCH Saenger, N., Kitanidis, P. K., Street, R. L. 2005; 41 (12)

  View details for DOI 10.1029/2004WR003875

  View details for Web of Science ID 000234370200003

• Mass-transfer limitations for nitrate removal in a uranium-contaminated aquifer ENVIRONMENTAL SCIENCE & TECHNOLOGY Luo, J., Cirpka, O. A., Wu, W. M., Fienen, M. N., Jardine, P. M., Mehlhorn, T. L., Watson, D. B., Criddle, C. S., Kitanidis, P. K. 2005; 39 (21): 8453-8459

  Abstract

  A field test on in situ subsurface bioremediation of uranium(VI) is underway at the Y-12 National Security Complex in the Oak Ridge Reservation, Oak Ridge, TN. Nitrate has a high concentration at the site, which prevents U(VI) reduction, and thus must be removed. An acidic-flush strategy for nitrate removal was proposed to create a treatment zone with low levels of accessible nitrate. The subsurface at the site contains highly interconnected fractures surrounded by matrix blocks of low permeability and high porosity and is therefore subject to preferential flow and matrix diffusion. To identify the heterogeneous mass transfer properties, we performed a novel forced-gradient tracer test, which involved the addition of bromide, the displacement of nitrate, and the rebound of nitrate after completion of pumping. The simplest conceptualization consistent with the data is that the pore-space consists of a single mobile domain, as well as a fast and a slowly reacting immobile domain. The slowly reacting immobile domain (shale matrix) constitutes over 80% of the pore volume and acts as a long-term reservoir of nitrate. According to simulations, the nitrate stored in the slowly interacting immobile domain in the fast flow layer, at depths of about 12.2-13.7 m, will be reduced by an order of magnitude over a period of about a year. By contrast, the mobile domain rapidly responds to flushing, and a low average nitrate concentration can be maintained if the nitrate is removed as soon as it enters the mobile domain. A field-scale experiment in which the aquifer was flushed with acidic solution confirmed our understanding of the system. For the ongoing experiments on microbial U(VI) reduction, nitrate concentrations must be low in the mobile domain to ensure U(VI) reducing conditions. We therefore conclude that the nitrate leaching out of the immobile pore space must continuously be removed by in situ denitrification to maintain favorable conditions.

  View details for DOI 10.1021/es050195g

  View details for Web of Science ID 000233078000054

  View details for PubMedID 16294887

• Semi-analytical homogeneous anisotropic capture zone delineation JOURNAL OF HYDROLOGY Fienen, M. N., Luo, J., Kitanidis, P. K. 2005; 312 (1-4): 39-50

  View details for DOI 10.1016/j.jhydrol.2005.02.008

  View details for Web of Science ID 000232672500004

• Modeling microbial reactions at the plume fringe subject to transverse mixing in porous media: When can the rates of microbial reaction be assumed to be instantaneous? WATER RESOURCES RESEARCH Chu, M., Kitanidis, P. K., McCarty, P. L. 2005; 41 (6)

  View details for DOI 10.1029/2004WR003495

  View details for Web of Science ID 000229832500001

• A method for the interpolation of nonnegative functions with an application to contaminant load estimation STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT Michalak, A. M., Kitanidis, P. K. 2005; 19 (1): 8-23

  View details for DOI 10.1007/s00477-004-0189-1

  View details for Web of Science ID 000226812000002

• On the asymptotic behavior of dilution parameters for Gaussian and hole-Gaussian log-conductivity covariance functions TRANSPORT IN POROUS MEDIA Pannone, M., Kitanidis, P. K. 2004; 56 (3): 257-281

  View details for Web of Science ID 000221122100002

• Fluid residence times within a recirculation zone created by an extraction-injection well pair JOURNAL OF HYDROLOGY Luo, J., Kitanidis, P. K. 2004; 295 (1-4): 149-162

  View details for DOI 10.1016/j.jhydrol.2004.03.006

  View details for Web of Science ID 000222955300011

• Estimation of historical groundwater contaminant distribution using the adjoint state method applied to geostatistical inverse modeling WATER RESOURCES RESEARCH Michalak, A. M., Kitanidis, P. K. 2004; 40 (8)

  View details for DOI 10.1029/2004WR003214

  View details for Web of Science ID 000223341000003

• Possible factors controlling the effectiveness of bioenhanced dissolution of non-aqueous phase tetrachloroethene ADVANCES IN WATER RESOURCES Chu, M., Kitanidis, P. K., McCarty, P. L. 2004; 27 (6): 601-615

  View details for DOI 10.1016/j.advwatres.2004.03.002

  View details for Web of Science ID 000221814200003

• Summary of a Panel Discussion at the International Groundwater Symposium held on March 25-28, 2002 in Berkeley, California, USA JOURNAL OF HYDRAULIC RESEARCH Findikakis, A. N., Helmig, R., Kitanidis, P., Nimmo, J., Pruess, K., Rubin, Y., Stauffer, F., Tsang, C. F. 2004; 42: III-IV

  View details for Web of Science ID 000221240800002

• Application of geostatistical inverse modeling to contaminant source identification at Dover AFB, Delaware International Groundwater Symposium Michalak, A. M., Kitanidis, P. K. TAYLOR & FRANCIS LTD. 2004: 9–18

  View details for Web of Science ID 000221240800004

• An application of Bayesian inverse methods to vertical deconvolution of hydraulic conductivity in a heterogeneous aquifer at Oak Ridge National Laboratory MATHEMATICAL GEOLOGY Fienen, M. N., Kitanidis, P. K., Watson, D., Jardine, P. 2004; 36 (1): 101-126

  View details for Web of Science ID 000189013000005

• Effects of biomass accumulation on microbially enhanced dissolution of a PCE pool: a numerical simulation JOURNAL OF CONTAMINANT HYDROLOGY Chu, M., Kitanidis, P. K., McCarty, P. L. 2003; 65 (1-2): 79-100

  Abstract

  Recent studies have shown that dechlorinating bacteria can accelerate the dissolution rate of dense, nonaqueous phase liquids (DNAPLs) containing tetrachloroethene (PCE). We present an advection-dispersion-reaction model for a two-dimensional domain, with groundwater flowing over a pool of free-product PCE. PCE is converted to cis-1,2-dichloroethene (cDCE) and toxicity due to PCE or cDCE is neglected. We adopt previously published correlations relating biomass concentrations and hydraulic conductivity, accounting for biofilm growth and plug-like growth. The system of coupled equations is solved numerically. The high biotransformation rate of PCE increases the concentration gradient of PCE at the water-DNAPL interface, enhancing dissolution. The higher the electron donor (ED) concentration, the larger the dissolution enhancement. Based on the values of maximum specific rate we used, when the electron donor is unlimited, the active biomass accumulates adjacent to the water-NAPL interface and microbial reactions can significantly enhance the pool dissolution. The resulting steady-state dissolution rate can be approximated by a half-order solution when zero-order kinetics are suitable for representing the microbial reaction. However, bioclogging may significantly reduce local hydraulic conductivity; thus, it decreases the flow near the water-DNAPL interface, decreasing dissolution. When the ED is the limiting factor, active biomass accumulates away from the interface. This creates a no-flow zone between the active biomass and the interface. The enlargement of the no-flow zone, due to the donor limitation, diminishes the concentration gradient and the flushing around the water-DNAPL interface. Such adverse impacts may significantly decrease the enhancement predicted by models that do not consider the effects of bioclogging.

  View details for DOI 10.1016/S0169-7722(02)00232-2

  View details for Web of Science ID 000184322200005

  View details for PubMedID 12855202

• A method for enforcing parameter nonnegativity in Bayesian inverse problems with an application to contaminant source identification WATER RESOURCES RESEARCH Michalak, A. M., Kitanidis, P. K. 2003; 39 (2)

  View details for DOI 10.1029/2002WR001480

  View details for Web of Science ID 000181964900001

• Numerical evaluation of solute dispersion and dilution in unsaturated heterogeneous media WATER RESOURCES RESEARCH Cirpka, O. A., Kitanidis, P. K. 2002; 38 (11)

  View details for DOI 10.1029/2001WR001262

  View details for Web of Science ID 000180527800002

• Travel-time based model of bioremediation using circulation wells 3rd International Conference on Groundwater Quality Cirpka, O. A., Kitanidis, P. K. INT ASSOC HYDROLOGICAL SCIENCES. 2002: 485–92

  View details for Web of Science ID 000185215100072

• Application of Bayesian inference methods to inverse modeling for contaminant source identification at Gloucester Landfill, Canada 14th International Conference on Computational Methods in Water Resources Michalak, A. M., Kitanidis, P. K. ELSEVIER SCIENCE BV. 2002: 1259–1266

  View details for Web of Science ID 000178839400164

• Pore-scale modeling of biological clogging due to aggregate expansion: A material mechanics approach WATER RESOURCES RESEARCH Dupin, H. J., Kitanidis, P. K., McCarty, P. L. 2001; 37 (12): 2965-2979

  View details for Web of Science ID 000173283000010

• Simulations of two-dimensional modeling of biomass aggregate growth in network models WATER RESOURCES RESEARCH Dupin, H. J., Kitanidis, P. K., McCarty, P. L. 2001; 37 (12): 2981-2994

  View details for Web of Science ID 000173283000011

• Transport of volatile compounds in porous media in the presence of a trapped gas phase JOURNAL OF CONTAMINANT HYDROLOGY Cirpka, O. A., Kitanidis, P. K. 2001; 49 (3-4): 263-285

  Abstract

  The presence of an immobile gaseous phase in an otherwise-saturated porous medium affects the transport of volatile compounds. The linear theory of partitioning tracers suggests that a volatile tracer introduced into such a system should be retarded with a constant retardation factor. Using high concentrations, however, the saturation of the gaseous phase will change as an effect of the tracer test itself. Competitive gas transfer among all volatile compounds and the change of saturation may lead to tracer concentrations that are temporarily higher than those injected. We analyze the system in the framework of the coherence theory by Helfferich [Soc. Pet. Eng. J. 21 (1) (1981) 51]. The governing equations are formulated as functions of total concentration, i.e., the mass of solutes in all phases per pore volume. Neglecting dispersion and mass-transfer kinetics, we derive the characteristic form of the resulting system of hyperbolic equations. In a system with N volatile compounds, a variation of the concentrations splits up into N waves, each traveling with its own characteristic velocity. If the presence of a gaseous phase is sustained, one wave will be a standing one. We perform numerical model calculations for tracers with various Henry's law coefficients and show that the results agree with the semi-analytical solution obtained by coherence theory.

  View details for Web of Science ID 000168794900005

  View details for PubMedID 11411400

• Improved dynamic programming methods for optimal control of lumped-parameter stochastic systems OPERATIONS RESEARCH Philbrick, C. R., Kitanidis, P. K. 2001; 49 (3): 398-412

  View details for Web of Science ID 000169449900006

• Travel-time based model of bioremediation using circulation wells GROUND WATER Cirpka, O. A., Kitanidis, P. K. 2001; 39 (3): 422-432

  Abstract

  Vertical circulation wells can efficiently provide microorganisms with substrates needed for enhanced bioremediation. We present a travel-time based approach for modeling bioreactive transport in a flow field caused by a series of circulation wells. Mixing within the aquifer is due to the differences in sorption behavior of the reactants. Neglecting local dispersion, transport simplifies to a single one-dimensional problem with constant coefficients for each well. Recirculation is characterized by the discharge densities over travel time. We apply the model to the stimulation of cometabolic dechlorination of trichloroethene (TCE) by alternate injection of oxygen and toluene into the circulation wells. Mixing within the wells can be minimized by interposing sufficiently long breaks between the oxygen and toluene pulses. In our simulation, the proposed injection scheme stimulates biomass growth without risking biofouling of the aquifer.

  View details for Web of Science ID 000168446500014

  View details for PubMedID 11341008

• Theoretical basis for the measurement of local transverse dispersion in isotropic porous media WATER RESOURCES RESEARCH Cirpka, O. A., Kitanidis, P. K. 2001; 37 (2): 243-252

  View details for Web of Science ID 000166582800006

• Large-time spatial covariance of concentration of conservative solute and application to the Cape Cod tracer test TRANSPORT IN POROUS MEDIA Pannone, M., Kitanidis, P. K. 2001; 42 (1-2): 109-132

  View details for Web of Science ID 000166056200006

• Sensitivity of temporal moments calculated by the adjoint-state method and joint inversing of head and tracer data ADVANCES IN WATER RESOURCES Cirpka, O. A., Kitanidis, P. K. 2000; 24 (1): 89-103

  View details for Web of Science ID 000089729900007

• Modeling particle transport and aggregation in a quiescent aqueous environment using the residence-time scheme WATER RESOURCES RESEARCH Perigault, J. G., Leckie, J. O., Kitanidis, P. K. 2000; 36 (8): 2249-2261

  View details for Web of Science ID 000088554500021

• Macroscopic behavior and random-walk particle tracking of kinetically sorbing solutes WATER RESOURCES RESEARCH Michalak, A. M., Kitanidis, P. K. 2000; 36 (8): 2133-2146

  View details for Web of Science ID 000088554500012

• An advective-dispersive stream tube approach for the transfer of conservative-tracer data to reactive transport WATER RESOURCES RESEARCH Cirpka, O. A., Kitanidis, P. K. 2000; 36 (5): 1209-1220

  View details for Web of Science ID 000086814100005

• Characterization of mixing and dilution in heterogeneous aquifers by means of local temporal moments WATER RESOURCES RESEARCH Cirpka, O. A., Kitanidis, P. K. 2000; 36 (5): 1221-1236

  View details for Web of Science ID 000086814100006

• Impact of biomass-decay terms on the simulation of pulsed bioremediation GROUND WATER Cirpka, O. A., Kitanidis, P. K. 2000; 38 (2): 254-263

  View details for Web of Science ID 000087761200014

• Numerical investigations of mixing in physically heterogeneous porous media using the one- and two-particle covariance XIIIth International Conference on Computational Methods in Water Resources Michalak, A. M., Kitanidis, P. K. A A BALKEMA PUBLISHERS. 2000: 423–429

  View details for Web of Science ID 000088804700058

• Effects of shear detachment on biomass growth and in situ bioremediation GROUND WATER MacDonald, T. R., Kitanidis, P. K., McCarty, P. L., Roberts, P. V. 1999; 37 (4): 555-563

  View details for Web of Science ID 000081268800016

• Mass-transfer limitations for macroscale bioremediation modeling and implications on aquifer clogging GROUND WATER MacDonald, T. R., Kitanidis, P. K., McCarty, P. L., Roberts, P. V. 1999; 37 (4): 523-531

  View details for Web of Science ID 000081268800012

• Limitations of deterministic optimization applied to reservoir operations JOURNAL OF WATER RESOURCES PLANNING AND MANAGEMENT-ASCE Philbrick, C. R., Kitanidis, P. K. 1999; 125 (3): 135-142

  View details for Web of Science ID 000079795300004

• Generalized covariance functions associated with the Laplace equation and their use in interpolation and inverse problems WATER RESOURCES RESEARCH Kitanidis, P. K. 1999; 35 (5): 1361-1367

  View details for Web of Science ID 000079992400003

• Adaptive-grid simulation of groundwater flow in heterogeneous aquifers ADVANCES IN WATER RESOURCES Cao, J., Kitanidis, P. K. 1999; 22 (7): 681-696

  View details for Web of Science ID 000079915900002

• Analysis of macrodispersion through volume averaging: comparison with stochastic theory STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT Wang, J., Kitanidis, P. K. 1999; 13 (1-2): 66-84

  View details for Web of Science ID 000082285600004

• Large-time behavior of concentration variance and dilution in heterogeneous formations WATER RESOURCES RESEARCH Pannone, M., Kitanidis, P. K. 1999; 35 (3): 623-634

  View details for Web of Science ID 000078771700002

• Transmissivity identification through multi-directional aquifer stimulation STOCHASTIC HYDROLOGY AND HYDRAULICS Snodgrass, M. F., Kitanidis, P. K. 1998; 12 (5): 299-316

  View details for Web of Science ID 000077855400002

• Adaptive finite element simulation of Stokes flow in porous media ADVANCES IN WATER RESOURCES Cao, J., Kitanidis, P. K. 1998; 22 (1): 17-31

  View details for Web of Science ID 000076182400002

• How observations and structure affect the geostatistical solution to the steady-state inverse problem GROUND WATER Kitanidis, P. K. 1998; 36 (5): 754-763

  View details for Web of Science ID 000075962300014

• Pore-scale dilution of conservative solutes: An example WATER RESOURCES RESEARCH Cao, J., Kitanidis, P. K. 1998; 34 (8): 1941-1949

  View details for Web of Science ID 000075025700009

• A method to infer in situ reaction rates from push-pull experiments GROUND WATER Snodgrass, M. F., Kitanidis, P. K. 1998; 36 (4): 645-650

  View details for Web of Science ID 000074934300015

• Spreadsheet method for evaluation of biochemical reaction rate coefficients and their uncertainties by weighted nonlinear least-squares analysis of the integrated monod equation APPLIED AND ENVIRONMENTAL MICROBIOLOGY Smith, L. H., McCarty, P. L., Kitanidis, P. K. 1998; 64 (6): 2044-2050

  View details for Web of Science ID 000073904800009

• A comparison of seven geostatistically based inverse approaches to estimate transmissivities for modeling advective transport by groundwater flow WATER RESOURCES RESEARCH Zimmerman, D. A., de Marsily, G., Gotway, C. A., Marietta, M. G., Axness, C. L., Beauheim, R. L., Bras, R. L., Carrera, J., Dagan, G., Davies, P. B., Gallegos, D. P., Galli, A., Gomez-Hernandez, J., Grindrod, P., Gutjahr, A. L., Kitanidis, P. K., Lavenue, A. M., McLaughlin, D., Neuman, S. P., RamaRao, B. S., Ravenne, C., Rubin, Y. 1998; 34 (6): 1373-1413

  View details for Web of Science ID 000073917600002

• Concentration fluctuations and dilution in aquifers WATER RESOURCES RESEARCH Kapoor, V., Kitanidis, P. K. 1998; 34 (5): 1181-1193

  View details for Web of Science ID 000073407600019

• Optimal conjunctive-use operations and plans WATER RESOURCES RESEARCH Philbrick, C. R., Kitanidis, P. K. 1998; 34 (5): 1307-1316

  View details for Web of Science ID 000073407600030

• Stochastic approaches to inverse problems 12th International Conference on Computational Methods in Water Resources Kitanidis, P. K. COMPUTATIONAL MECHANICS PUBLICATIONS LTD. 1998: 281–288

  View details for Web of Science ID 000074946700035

• Advection-diffusion in spatially random flows: Formulation of concentration covariance STOCHASTIC HYDROLOGY AND HYDRAULICS Kapoor, V., Kitanidis, P. K. 1997; 11 (5): 397-422

  View details for Web of Science ID A1997YE68400003

• The minimum structure solution to the inverse problem WATER RESOURCES RESEARCH Kitanidis, P. K. 1997; 33 (10): 2263-2272

  View details for Web of Science ID A1997XY63200005

• A reassessment of the groundwater inverse problem - Comment WATER RESOURCES RESEARCH Kitanidis, P. K. 1997; 33 (9): 2199-2202

  View details for Web of Science ID A1997XU47300014

• A variance-ratio test for supporting a variable mean in kriging MATHEMATICAL GEOLOGY Kitanidis, P. K. 1997; 29 (3): 335-348

  View details for Web of Science ID A1997WY26900002

• A geostatistical approach to contaminant source identification WATER RESOURCES RESEARCH Snodgrass, M. F., Kitanidis, P. K. 1997; 33 (4): 537-546

  View details for Web of Science ID A1997WQ77800004

• Numerical modeling and uncertainties in rate coefficients for methane utilization and TCE cometabolism by a methane-oxidizing mixed culture BIOTECHNOLOGY AND BIOENGINEERING Smith, L. H., Kitanidis, P. K., McCarty, P. L. 1997; 53 (3): 320-331

  Abstract

  The rates of methane utilization and trichloroethylene (TCE) cometabolism by a methanotrophic mixed culture were characterized in batch and pseudo-steady-state studies. Procedures for determination of the rate coefficients and their uncertainties by fitting a numerical model to experimental data are described. The model consisted of a system of differential equations for the rates of Monod kinetics, cell growth on methane and inactivation due to TCE transformation product toxicity, gas/liquid mass transfer of methane and TCE, and the rate of passive losses of TCE. The maximum specific rate of methane utilization (k(CH(4) )) was determined by fitting the numerical model to batch experimental data, with the initial concentration of active methane-oxidizing cells (X(0) (a)) also used as a model fitting parameter. The best estimate of k(CH(4) ) was 2.2 g CH(4)/g cells-d with excess copper available, with a single-parameter 95% confidence interval of 2.0-2.4 mg/mg-d. The joint 95% confidence region for k(CH(4) ) and X(0) (a) is presented graphically. The half-velocity coefficient (K(S,CH(4) )) was 0.07 mg CH(4)/L with excess copper available and 0.47 mg CH(4)/L under copper limitation, with 95% confidence intervals of 0.02-0.11 and 0.35-0.59 mg/L, respectively. Unique values of the TCE rate coefficients k(TCE) and K(S,TCE) could not be determined because they were found to be highly correlated in the model fitting analysis. However, the ratio k(TCE)/K(S,TCE) and the TCE transformation capacity (T(C)) were well defined, with values of 0.35 L/mg-day and 0.21 g TCE/g active cells, respectively, for cells transforming TCE in the absence of methane or supplemental formate. The single-parameter 95% confidence intervals for k(TCE)/K(S,TCE) and T(C) were 0.27-0.43 L/mg-d and 0.18-0.24 g TCE/g active cells, respectively. The joint 95% confidence regions for k(TCE)/K(S,TCE) and T(C) are presented graphically.

  View details for Web of Science ID A1997WG06900011

  View details for PubMedID 18633987

• In situ BTEX biotransformation under enhanced nitrate- and sulfate-reducing conditions ENVIRONMENTAL SCIENCE & TECHNOLOGY Reinhard, M., Shang, S., Kitanidis, P. K., Orwin, E., Hopkins, G. D., Lebron, C. A. 1997; 31 (1): 28-36

  View details for Web of Science ID A1997WC40000023

• Stokes flow in a slowly varying two-dimensional periodic pore TRANSPORT IN POROUS MEDIA Kitanidis, P. K., Dykaar, B. B. 1997; 26 (1): 89-98

  View details for Web of Science ID A1997WM35800005

• On the geostatistical approach to the inverse problem ADVANCES IN WATER RESOURCES Kitanidis, P. K. 1996; 19 (6): 333-342

  View details for Web of Science ID A1996VM76900001

• Optimization of Monitoring Well Installation Time and Location During Aquifer Decontamination WATER RESOURCES MANAGEMENT Lee, S., Kitanidis, P. K. 1996; 10 (6): 439-462

  View details for Web of Science ID 000208540400002

• Geostatistical interpolation of chemical concentration ADVANCES IN WATER RESOURCES Kitanidis, P. K., Shen, K. F. 1996; 19 (6): 369-378

  View details for Web of Science ID A1996VM76900004

• Analytical expressions of conditional mean, covariance, and sample functions in geostatistics STOCHASTIC HYDROLOGY AND HYDRAULICS Kitanidis, P. K. 1996; 10 (4): 279-294

  View details for Web of Science ID A1996VR85800002

• Effects of first-order approximations on head and specific discharge covariances in high-contrast log conductivity WATER RESOURCES RESEARCH VANLENT, T., Kitanidis, P. K. 1996; 32 (5): 1197-1207

  View details for Web of Science ID A1996UH88200005

• Macrotransport of a biologically reacting solute through porous media WATER RESOURCES RESEARCH Dykaar, B. B., Kitanidis, P. K. 1996; 32 (2): 307-320

  View details for Web of Science ID A1996TT02500008

• Concentration fluctuations and dilution in two-dimensionally periodic heterogeneous porous media TRANSPORT IN POROUS MEDIA Kapoor, V., Kitanidis, P. K. 1996; 22 (1): 91-119

  View details for Web of Science ID A1996UB70400004

• QUASI-LINEAR GEOSTATISTICAL THEORY FOR INVERSING WATER RESOURCES RESEARCH Kitanidis, P. K. 1995; 31 (10): 2411-2419

  View details for Web of Science ID A1995RX71500003

• PREDICTION OF SINGLE-PHASE TRANSPORT PARAMETERS IN A VARIABLE APERTURE FRACTURE GEOPHYSICAL RESEARCH LETTERS Keller, A. A., Roberts, P. V., Kitanidis, P. K. 1995; 22 (11): 1425-1428

  View details for Web of Science ID A1995RB55000028

• ANAEROBIC TRANSFORMATION OF CHLORINATED ALIPHATIC-HYDROCARBONS IN A SAND AQUIFER BASED ON SPATIAL CHEMICAL-DISTRIBUTIONS WATER RESOURCES RESEARCH Semprini, L., Kitanidis, P. K., Kampbell, D. H., WILSON, J. T. 1995; 31 (4): 1051-1062

  View details for Web of Science ID A1995QQ32000024

• Biofouling effects on in situ TCE bioremediation by phenol utilizers 3rd International In Situ and On-Site Bioreclamation Symposium MacDonald, T. R., Kitanidis, P. K. BATTELLE PRESS. 1995: 213–19

  View details for Web of Science ID A1995BG31R00025

• RECENT ADVANCES IN GEOSTATISTICAL INFERENCE ON HYDROGEOLOGICAL VARIABLES REVIEWS OF GEOPHYSICS Kitanidis, P. K. 1995; 33: 1103-1109

  View details for Web of Science ID A1995RJ50900038

• PARTICLE-TRACKING EQUATIONS FOR THE SOLUTION OF THE ADVECTION-DISPERSION EQUATION WITH VARIABLE-COEFFICIENTS WATER RESOURCES RESEARCH Kitanidis, P. K. 1994; 30 (11): 3225-3227

  View details for Web of Science ID A1994PP21300033

• SOLUTE DILUTION AT THE BORDEN AND CAPE-COD GROUNDWATER TRACER TESTS WATER RESOURCES RESEARCH Thierrin, J., Kitanidis, P. K. 1994; 30 (11): 2883-2890

  View details for Web of Science ID A1994PP21300002

• THE CONCEPT OF THE DILUTION INDEX WATER RESOURCES RESEARCH Kitanidis, P. K. 1994; 30 (7): 2011-2026

  View details for Web of Science ID A1994NV57900006

• MODELING THE FREE-SURFACE OF AN UNCONFINED AQUIFER NEAR A RECIRCULATION WELL GROUND WATER MacDonald, T. R., Kitanidis, P. K. 1993; 31 (5): 774-780

  View details for Web of Science ID A1993LW31500011

• GENERALIZED COVARIANCE FUNCTIONS IN ESTIMATION MATHEMATICAL GEOLOGY Kitanidis, P. K. 1993; 25 (5): 525-540

  View details for Web of Science ID A1993LK53100002

• TRANSMISSIVITY OF A HETEROGENEOUS FORMATION WATER RESOURCES RESEARCH Dykaar, B. B., Kitanidis, P. K. 1993; 29 (4): 985-1001

  View details for Web of Science ID A1993KW17800021

• MACRODISPERSION OF SORBING SOLUTES IN HETEROGENEOUS POROUS FORMATIONS WITH SPATIALLY PERIODIC RETARDATION FACTOR AND VELOCITY-FIELD WATER RESOURCES RESEARCH Chrysikopoulos, C. V., Kitanidis, P. K., Roberts, P. V. 1992; 28 (6): 1517-1529

  View details for Web of Science ID A1992HX30900003

• DETERMINATION OF THE EFFECTIVE HYDRAULIC CONDUCTIVITY FOR HETEROGENEOUS POROUS-MEDIA USING A NUMERICAL SPECTRAL APPROACH .1. METHOD WATER RESOURCES RESEARCH Dykaar, B. B., Kitanidis, P. K. 1992; 28 (4): 1155-1166

  View details for Web of Science ID A1992HN11300020

• DETERMINATION OF THE EFFECTIVE HYDRAULIC CONDUCTIVITY FOR HETEROGENEOUS POROUS-MEDIA USING A NUMERICAL SPECTRAL APPROACH .2. RESULTS WATER RESOURCES RESEARCH Dykaar, B. B., Kitanidis, P. K. 1992; 28 (4): 1167-1178

  View details for Web of Science ID A1992HN11300021

• ANALYSIS OF MACRODISPERSION THROUGH VOLUME-AVERAGING - MOMENT EQUATIONS STOCHASTIC HYDROLOGY AND HYDRAULICS Kitanidis, P. K. 1992; 6 (1): 5-25

  View details for Web of Science ID A1992HL12400002

• GENERALIZED TAYLOR-ARIS MOMENT ANALYSIS OF THE TRANSPORT OF SORBING SOLUTES THROUGH POROUS-MEDIA WITH SPATIALLY PERIODIC RETARDATION FACTOR TRANSPORT IN POROUS MEDIA Chrysikopoulos, C. V., Kitanidis, P. K., Roberts, P. V. 1992; 7 (2): 163-185

  View details for Web of Science ID A1992HF78600004

• OPTIMAL ESTIMATION AND SCHEDULING IN AQUIFER REMEDIATION WITH INCOMPLETE INFORMATION WATER RESOURCES RESEARCH Lee, S. I., Kitanidis, P. K. 1991; 27 (9): 2203-2217

  View details for Web of Science ID A1991GD92700004

• ORTHONORMAL RESIDUALS IN GEOSTATISTICS - MODEL CRITICISM AND PARAMETER-ESTIMATION MATHEMATICAL GEOLOGY Kitanidis, P. K. 1991; 23 (5): 741-758

  View details for Web of Science ID A1991FV79900004

• ONE-DIMENSIONAL SOLUTE TRANSPORT IN POROUS-MEDIA WITH PARTIAL WELL-TO-WELL RECIRCULATION - APPLICATION TO FIELD EXPERIMENTS WATER RESOURCES RESEARCH Chrysikopoulos, C. V., Roberts, P. V., Kitanidis, P. K. 1990; 26 (6): 1189-1195

  View details for Web of Science ID A1990DH11900008

• EFFECTIVE HYDRAULIC CONDUCTIVITY FOR GRADUALLY VARYING FLOW WATER RESOURCES RESEARCH Kitanidis, P. K. 1990; 26 (6): 1197-1208

  View details for Web of Science ID A1990DH11900009

• OPTIMIZATION OF THE PUMPING SCHEDULE IN AQUIFER REMEDIATION UNDER UNCERTAINTY WATER RESOURCES RESEARCH Andricevic, R., Kitanidis, P. K. 1990; 26 (5): 875-885

  View details for Web of Science ID A1990DD09400010

• ANALYSIS OF ONE-DIMENSIONAL SOLUTE TRANSPORT THROUGH POROUS-MEDIA WITH SPATIALLY-VARIABLE RETARDATION FACTOR WATER RESOURCES RESEARCH Chrysikopoulos, C. V., Kitanidis, P. K., Roberts, P. V. 1990; 26 (3): 437-446

  View details for Web of Science ID A1990CU45800008

• GEOSTATISTICAL ESTIMATION OF HYDRAULIC-HEAD GRADIENTS GROUND WATER PHILIP, R. D., Kitanidis, P. K. 1989; 27 (6): 855-865

  View details for Web of Science ID A1989AZ34200009

• A NUMERICAL SPECTRAL APPROACH FOR THE DERIVATION OF PIEZOMETRIC HEAD COVARIANCE FUNCTIONS WATER RESOURCES RESEARCH VANLENT, T., Kitanidis, P. K. 1989; 25 (11): 2287-2298

  View details for Web of Science ID A1989AZ73900001

• STOCHASTIC-CONTROL OF CONTAMINANT TRANSPORT PROBLEMS SYMP ON GROUNDWATER MANAGEMENT : QUANTITY AND QUALITY Andricevic, R., Kitanidis, P. K. INT ASSOC HYDROLOGICAL SCIENCES. 1989: 271–284

  View details for Web of Science ID A1989BP90H00024

• PREDICTION BY THE METHOD OF MOMENTS OF TRANSPORT IN A HETEROGENEOUS FORMATION JOURNAL OF HYDROLOGY Kitanidis, P. K. 1988; 102 (1-4): 453-473

  View details for Web of Science ID A1988Q618100024

• GRADIENT DYNAMIC-PROGRAMMING FOR STOCHASTIC OPTIMAL-CONTROL OF MULTIDIMENSIONAL WATER-RESOURCES SYSTEMS WATER RESOURCES RESEARCH Foufoula-Georgiou, E., Kitanidis, P. K. 1988; 24 (8): 1345-1359

  View details for Web of Science ID A1988P677200014

• PARAMETRIC-ESTIMATION OF COVARIANCES OF REGIONALIZED VARIABLES WATER RESOURCES BULLETIN Kitanidis, P. K. 1987; 23 (4): 557-567

  View details for Web of Science ID A1987J814400002

• ERROR ANALYSIS OF CONVENTIONAL DISCRETE AND GRADIENT DYNAMIC-PROGRAMMING WATER RESOURCES RESEARCH Kitanidis, P. K., Foufoula-Georgiou, E. 1987; 23 (5): 845-858

  View details for Web of Science ID A1987H299600011

• A 1ST-ORDER APPROXIMATION TO STOCHASTIC OPTIMAL-CONTROL OF RESERVOIRS STOCHASTIC HYDROLOGY AND HYDRAULICS Kitanidis, P. K. 1987; 1 (3): 169-184

  View details for Web of Science ID A1987K189400002

• ADAPTIVE FILTERING THROUGH DETECTION OF ISOLATED TRANSIENT ERRORS IN RAINFALL-RUNOFF MODELS WATER RESOURCES RESEARCH Kitanidis, P. K., Bras, R. L. 1980; 16 (4): 740-748

  View details for Web of Science ID A1980KG45700017

• REAL-TIME FORECASTING WITH A CONCEPTUAL HYDROLOGIC MODEL .1. ANALYSIS OF UNCERTAINTY WATER RESOURCES RESEARCH Kitanidis, P. K., Bras, R. L. 1980; 16 (6): 1025-1033

  View details for Web of Science ID A1980KW20100007

• REAL-TIME FORECASTING WITH A CONCEPTUAL HYDROLOGIC MODEL .2. APPLICATIONS AND RESULTS WATER RESOURCES RESEARCH Kitanidis, P. K., Bras, R. L. 1980; 16 (6): 1034-1044

  View details for Web of Science ID A1980KW20100008

• COLLINEARITY AND STABILITY IN THE ESTIMATION OF RAINFALL-RUNOFF MODEL PARAMETERS JOURNAL OF HYDROLOGY Kitanidis, P. K., Bras, R. L. 1979; 42 (1-2): 91-108

  View details for Web of Science ID A1979HE53700007