Research Engineer, Earth System Science
PhD, Carnegie Mellon University, Civil & Environmental Engineering (2019)
MS, Carnegie Mellon University, Civil & Environmental Engineering (2016)
BS, Oberlin College, Chemistry (2014)
Environmental impact of solution pH on the formation and migration of iron colloids in deep subsurface energy systems.
The Science of the total environment
Deep subsurface stimulation processes often promote fluid-rock interactions that can lead to the formation of small colloidal particles that are suspected to migrate through the rock matrix, partially or fully clog pores and microfractures, and promote the mobilization of contaminants. Thus, the goal of this work is to understand the geochemical changes of the host rock in response to reservoir stimulation that promote the formation and migration of colloids. Two different carbonate-rich shales were exposed to different solution pHs (pH = 2 and 7). Iron and other mineral transformations at the shale-fluid interface were first characterized by synchrotron-based XRF mapping. Then, colloids that were able to migrate from the shale into the bulk fluid were characterized by synchrotron-based extended X-ray absorption structure (EXAFS), scanning electron microscopy (SEM), and single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-icpTOF-MS). When exposed to the pH = 2 solution, extensive mineral dissolution and secondary precipitation was observed; iron-(oxyhydr)oxide colloids colocated with silicates were observed by SEM at the fluid-shale interfaces, and the mobilization of chromium and nickel with these iron colloids into the bulk fluid was detected by sp-icpTOF-MS. Iron EXAFS spectra of the solution at the shale-fluid interface suggests the rapid (within minutes) formation of ferrihydrite-like nanoparticles. Thus, we demonstrate that the pH neutralization promotes the mobilization of existing silicate minerals and the rapid formation of new iron colloids. These Fe colloids have the potential to migrate through the shale matrix and mobilize other heavy metals (such as Cr and Ni, in this study) and impacting groundwater quality, as well produced waters from these hydraulic fracturing operations.
View details for DOI 10.1016/j.scitotenv.2023.166409
View details for PubMedID 37597537
- Impact of Acid-Base Stimulation Sequence on Mineral Stability forTight/Impermeable Unconventional Carbonate-Rich Rocks: ADelaware Basin Case Study br ENERGY & FUELS 2022; 36 (9): 4746-4756
Geochemical Modeling of Celestite (SrSO4) Precipitation and Reactive Transport in Shales.
Environmental science & technology
Celestite (SrSO4) precipitation is a prevalent example of secondary sulfate mineral scaling issues in hydraulic fracturing systems, particularly in basins where large concentrations of naturally occurring strontium are present. Here, we present a validated and flexible geochemical model capable of predicting celestite formation under such unconventional environments. Simulations were built using CrunchFlow and guided by experimental data derived from batch reactors. These data allowed the constraint of key kinetic and thermodynamic parameters for celestite precipitation under relevant synthetic hydraulic fracturing fluid conditions. Effects of ionic strength, saturation index, and the presence of additives were considered in the combined experimental and modeling construction. This geochemical model was then expanded into a more complex system where interactions between hydraulic fracturing fluids and shale rocks were allowed to occur subject to diffusive transport. We find that the carbonate content of a given shale and the presence of persulfate breaker in the system strongly impact the location and extent of celestite formation. The results of this study provide a novel multicomponent reactive transport model that may be used to guide future experimental design in the pursuit of celestite and other sulfate mineral scale mitigation under extreme conditions typical of hydraulic fracturing in shale formations.
View details for DOI 10.1021/acs.est.1c07717
View details for PubMedID 35297619
A Critical Review of the Physicochemical Impacts of Water Chemistry on Shale in Hydraulic Fracturing Systems.
Environmental science & technology
Hydraulic fracturing of unconventional hydrocarbon resources involves the sequential injection of a high-pressure, particle-laden fluid with varying pH's to make commercial production viable in low permeability rocks. This process both requires and produces extraordinary volumes of water. The water used for hydraulic fracturing is typically fresh, whereas "flowback" water is typically saline with a variety of additives which complicate safe disposal. As production operations continue to expand, there is an increasing interest in treating and reusing this high-salinity produced water for further fracturing. Here we review the relevant transport and geochemical properties of shales, and critically analyze the impact of water chemistry (including produced water) on these properties. We discuss five major geochemical mechanisms that are prominently involved in the temporal and spatial evolution of fractures during the stimulation and production phase: shale softening, mineral dissolution, mineral precipitation, fines migration, and wettability alteration. A higher salinity fluid creates both benefits and complications in controlling these mechanisms. For example, higher salinity fluid inhibits clay dispersion, but simultaneously requires more additives to achieve appropriate viscosity for proppant emplacement. In total this review highlights the nuances of enhanced hydrogeochemical shale stimulation in relation to the choice of fracturing fluid chemistry.
View details for DOI 10.1021/acs.est.0c04901
View details for PubMedID 33428391
Protein coating composition targets nanoparticles to leaf stomata and trichomes.
Plant nanobiotechnology has the potential to revolutionize agriculture. However, the lack of effective methods to deliver nanoparticles (NPs) to the precise locations in plants where they are needed impedes these technological innovations. Here, model gold nanoparticles (AuNP) were coated with citrate, bovine serum albumin (BSA) as a protein control, or LM6-M, an antibody with an affinity for functional groups unique to stomata on leaf surfaces to deliver the AuNPs to stomata. One-month-old Vicia faba leaves were exposed via drop deposition to aqueous suspensions of LM6-M-coated AuNPs and allowed to air dry. After rinsing, Au distribution on the leaf surface was investigated by enhanced dark-field microscopy and X-ray fluorescence mapping. While citrate-coated AuNPs randomly covered the plant leaves, LM6M-AuNPs strongly adhered to the stomata and remained on the leaf surface after rinsing, and BSA-AuNPs specifically targeted trichome hairs. To the authors' knowledge, this is the first report of active targeting of live leaf structures using NPs coated with molecular recognition molecules. This proof-of-concept study provides a strategy for future targeted nanopesticide delivery research.
View details for DOI 10.1039/c9nr08100c
View details for PubMedID 31998910
Differential Reactivity of Copper- and Gold-Based Nanomaterials Controls Their Seasonal Biogeochemical Cycling and Fate in a Freshwater Wetland Mesocosm.
Environmental science & technology
Reliable predictions of the environmental fate and risk of engineered nanomaterials (ENMs) require a better understanding of ENM reactivity in complex, biologically active systems for chronic low-concentration exposure scenarios. Here, simulated freshwater wetland mesocosms were dosed with ENMs to assess how their reactivity and seasonal changes in environmental parameters influence ENM fate in aquatic systems. Copper-based ENMs (Kocide), known to dissolve in water, and gold nanoparticles (AuNPs), stable against dissolution in the absence of specific ligands, were added weekly to mesocosm waters for 9 months. Metal accumulation and speciation changes in the different environmental compartments were assessed over time. Copper from Kocide rapidly dissolved likely associating with organic matter in the water column, transported to terrestrial soils and deeper sediment where it became associated with organic or sulfide phases. In contrast, Au accumulated on/in the macrophytes where it oxidized and transferred over time to surficial sediment. A dynamic seasonal accumulation and metal redox cycling were found between the macrophyte and the surficial sediment for AuNPs. These results demonstrate the need for experimental quantification of how the biological and chemical complexity of the environment, combined with their seasonal variations, drive the fate of metastable ENMs.
View details for DOI 10.1021/acs.est.9b05097
View details for PubMedID 31951397
CuO Nanoparticles Alter the Rhizospheric Bacterial Community and Local Nitrogen Cycling for Wheat Grown in a Calcareous Soil.
Environmental science & technology
The application of nanoparticles (NPs) to soils, as either fertilizers or fungicides (e.g., CuO NPs), has been proposed to improve the sustainability of agriculture. The observed effects could result directly from the NP-plant interactions or indirectly through effects on the soil microbiome. The objective of this study was to assess the effects of CuO NPs on the changes in the bacterial community structure and nitrogen-cycling-associated functions in a high pH soil and to correlate these changes with nitrate accumulation, soil parameter changes, and plant growth over 28 days. Triticum aestivum seedlings were exposed to 50 mg/kg CuO NPs, 50 mg/kg CuSO4, or 0.5 mg/kg CuSO4 in a standard soil (Lufa 2.1 soil, pH adjusted to 7.6). While Cu treatments reduced nitrate accumulation in the bulk soil, the effects were opposite in the rhizosphere (the soil influenced by root exudates). While nitrate accumulation in bulk soil negatively correlated with total Cu concentration, part of the nitrate concentration in the rhizosphere was explained by root uptake during plant growth, the rest being modulated by Cu treatments. The abundance of genes involved in the nitrogen cycle in the rhizosphere soil correlated with the ionic copper concentration. The increased nitrate concentration in the rhizosphere correlated with an increase of the gene abundance related to the nitrogen fixation and a decrease of denitrification gene abundance. Microbial diversity in bulk or rhizosphere soil under the different treatments alone could not explain these variations, while differences in the assemblages of bacteria associated with these functional gene abundances gave good insights. This study highlights the complexity of microbial N-related function in the rhizosphere and the need to characterize the rhizosphere soil, plant growth and root activity, NP (bio)transformations, along with microbial networks, to understand the impact of agrochemicals (here CuO NPs) on soil fertility.
View details for DOI 10.1021/acs.est.0c00036
View details for PubMedID 32579348
- Nanoparticle surface charge influences translocation and leaf distribution in vascular plants with contrasting anatomy ENVIRONMENTAL SCIENCE-NANO 2019; 6 (8): 2508–19
Effect of Soil Organic Matter, Soil pH, and Moisture Content on Solubility and Dissolution Rate of CuO NPs in Soil
ENVIRONMENTAL SCIENCE & TECHNOLOGY
2019; 53 (9): 4959–67
The objectives of this research were to quantify the impact of organic matter content, soil pH and moisture content on the dissolution rate and solubility of copper oxide nanoparticles (CuO NPs) in soil, and to develop an empirical model to predict the dissolution kinetics of CuO NPs in soil. CuO NPs were dosed into standard LUFA soils with various moisture content, pH and organic carbon content. Chemical extractions were applied to measure the CuO NP dissolution kinetics. Doubling the reactive organic carbon content in LUFA 2.1 soil increased the solubility of CuO NP 2.7-fold but did not change the dissolution rate constant. Increasing the soil pH from 5.9 to 6.8 in LUFA 2.2 soil decreased the dissolution rate constant from 0.56 mol1/3·kg1/3·s-1 to 0.17 mol1/3·kg1/3·s-1 without changing the solubility of CuO NP in soil. For six soils, the solubility of CuO NP correlated well with soil organic matter content ( R2 = 0.89) independent of soil pH. In contrast, the dissolution rate constant correlated with pH for pH < 6.3 ( R2 = 0.89), independent of soil organic matter content. These relationships predicted the solubility and dissolution rate constants of CuO NP in two test soils (pH 5.0 and pH 7.6). Moisture content showed negligible impact on the dissolution kinetics of CuO NPs. Our study suggests that soil pH and organic matter content affect the dissolution behavior of CuO NP in soil in a predictable manner.
View details for DOI 10.1021/acs.est.8b07243
View details for Web of Science ID 000467641800032
View details for PubMedID 30920811
Nanoparticle Size and Coating Chemistry Control Foliar Uptake Pathways, Translocation, and Leaf-to-Rhizosphere Transport in Wheat
2019; 13 (5): 5291–5305
Nanoenabled foliar-applied agrochemicals can potentially be safer and more efficient than conventional products. However, limited understanding about how nanoparticle properties influence their interactions with plant leaves, uptake, translocation through the mesophyll to the vasculature, and transport to the rest of the plant prevents rational design. This study used a combination of Au quantification and spatial analysis to investigate how size (3, 10, or 50 nm) and coating chemistry (PVP versus citrate) of gold nanoparticles (AuNPs) influence these processes. Following wheat foliar exposure to AuNPs suspensions (∼280 ng per plant), adhesion on the leaf surface was increased for smaller sizes, and PVP-AuNPs compared to citrate-AuNPs. After 2 weeks, there was incomplete uptake of citrate-AuNPs with some AuNPs remaining on the outside of the cuticle layer. However, the fraction of citrate-AuNPs that had entered the leaf was translocated efficiently to the plant vasculature. In contrast, for similar sizes, virtually all of the PVP-AuNPs crossed the cuticle layer after 2 weeks, but its transport through the mesophyll cells was lower. As a consequence of PVP-AuNP accumulation in the leaf mesophyll, wheat photosynthesis was impaired. Regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10-30%) and in roots (10-25%), and 5-15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lower ζ potentials) was transported to the roots. The key hypotheses about the NPs physical-chemical and plant physiology parameters that may matter to predict leaf-to-rhizosphere transport are also discussed.
View details for DOI 10.1021/acsnano.8b09781
View details for Web of Science ID 000469886300038
View details for PubMedID 31074967
Gold nanoparticle biodissolution by a freshwater macrophyte and its associated microbiome
2018; 13 (11): 1072-+
Predicting nanoparticle fate in aquatic environments requires mimicking of ecosystem complexity to observe the geochemical processes affecting their behaviour. Here, 12 nm Au nanoparticles were added weekly to large-scale freshwater wetland mesocosms. After six months, ~70% of Au was associated with the macrophyte Egeria densa, where, despite the thermodynamic stability of Au0 in water, the pristine Au0 nanoparticles were fully oxidized and complexed to cyanide, hydroxyls or thiol ligands. Extracted biofilms growing on E. densa leaves were shown to dissolve Au nanoparticles within days. The Au biodissolution rate was highest for the biofilm with the lowest prevalence of metal-resistant taxa but the highest ability to release cyanide, known to promote Au0 oxidation and complexation. Macrophytes and the associated microbiome thus form a biologically active system that can be a major sink for nanoparticle accumulation and transformations. Nanoparticle biotransformation in these compartments should not be ignored, even for nanoparticles commonly considered to be stable in the environment.
View details for DOI 10.1038/s41565-018-0231-y
View details for Web of Science ID 000449291700022
View details for PubMedID 30104621
Temporal Evolution of Copper Distribution and Speciation in Roots of Triticum aestivum Exposed to CuO, Cu(OH)(2), and CuS Nanoparticles
ENVIRONMENTAL SCIENCE & TECHNOLOGY
2018; 52 (17): 9777–84
Utilization of nanoparticles (NP) in agriculture as fertilizers or pesticides requires an understanding of the NP properties influencing their interactions with plant roots. To evaluate the influence of the solubility of Cu-based NP on Cu uptake and NP association with plant roots, wheat seedlings were hydroponically exposed to 1 mg/L of Cu NPs with different solubilities [CuO, CuS, and Cu(OH)2] for 1 h then transferred to a Cu-free medium for 48 h. Fresh, hydrated roots were analyzed using micro X-ray fluorescence (μ-XRF) and imaging fluorescence X-ray absorption near edge spectroscopy (XANES imaging) to provide laterally resolved distribution and speciation of Cu in roots. Higher solubility Cu(OH)2 NPs provided more uptake of Cu after 1 h of exposure, but the lower solubility materials (CuO and CuS) were more persistent on the roots and continued to deliver Cu to plant leaves over the 48 h depuration period. These results demonstrate that NPs, by associating to the roots, have the potential to play a role in slowly providing micronutrients to plants. Thus, tuning the solubility of NPs may provide a long-term slow delivery of micronutrients to plants and provide important information for understanding mechanisms responsible for plant uptake, transformation, and translocation of NPs.
View details for DOI 10.1021/acs.est.8b02111
View details for Web of Science ID 000444061100025
View details for PubMedID 30078329
- Effect of silver concentration and chemical transformations on release and antibacterial efficacy in silver-containing textiles NANOIMPACT 2018; 11: 51–57
Elucidating nanoparticle-plant leaf interactions, uptake, and mobility for designing highly efficient foliar-applied agrochemicals
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435539901118
Toward improving agrochemical efficiency: Impact of Cu-based nanoparticle solubility on metal uptake, speciation, translocation, and distribution in Triticum aestivum (wheat)
AMER CHEMICAL SOC. 2018
View details for Web of Science ID 000435539901119
Impact of Surface Charge on Cerium Oxide Nanoparticle Uptake and Translocation by Wheat (Triticum aestivum)
ENVIRONMENTAL SCIENCE & TECHNOLOGY
2017; 51 (13): 7361–68
Nanoparticle (NP) physiochemical properties, including surface charge, affect cellular uptake, translocation, and tissue localization. To evaluate the influence of surface charge on NP uptake by plants, wheat seedlings were hydroponically exposed to 20 mg/L of ∼4 nm CeO2 NPs functionalized with positively charged, negatively charged, and neutral dextran coatings. Fresh, hydrated roots and leaves were analyzed at various time points over 34 h using fluorescence X-ray absorption near-edge spectroscopy to provide laterally resolved spatial distribution and speciation of Ce. A 15-20% reduction from Ce(IV) to Ce(III) was observed in both roots and leaves, independent of NP surface charge. Because of its higher affinity with negatively charged cell walls, CeO2(+) NPs adhered to the plant roots the strongest. After 34 h, CeO2(-), and CeO2(0) NP exposed plants had higher Ce leaf concentrations than the plants exposed to CeO2(+) NPs. Whereas Ce was found mostly in the leaf veins of the CeO2(-) NP exposed plant, Ce was found in clusters in the nonvascular leaf tissue of the CeO2(0) NP exposed plant. These results provide important information for understanding mechanisms responsible for plant uptake, transformation, and translocation of NPs, and suggest that NP coatings can be designed to target NPs to specific parts of plants.
View details for DOI 10.1021/acs.est.7b00813
View details for Web of Science ID 000405056200007
View details for PubMedID 28575574
Tuning NP properties for optimizing plant uptake and translocation
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569101533
Time and Nanoparticle Concentration Affect the Extractability of Cu from CuO NP-Amended Soil
ENVIRONMENTAL SCIENCE & TECHNOLOGY
2017; 51 (4): 2226–34
We assess the effect of CuO nanoparticle (NP) concentration and soil aging time on the extractability of Cu from a standard sandy soil (Lufa 2.1). The soil was dosed with CuO NPs or Cu(NO3)2 at 10 mg/kg or 100 mg/kg of total added Cu, and then extracted using either 0.01 M CaCl2 or 0.005 M diethylenetriaminepentaacetic acid (DTPA) (pH 7.6) extraction fluid at selected times over 31 days. For the high dose of CuO NPs, the amount of DTPA-extractable Cu in soil increased from 3 wt % immediately after mixing to 38 wt % after 31 days. In contrast, the extractability of Cu(NO3)2 was highest initially, decreasing with time. The increase in extractability was attributed to dissolution of CuO NPs in the soil. This was confirmed with synchrotron X-ray absorption near edge structure measurements. The CuO NP dissolution kinetics were modeled by a first-order dissolution model. Our findings indicate that dissolution, concentration, and aging time are important factors that influence Cu extractability in CuO NP-amended soil and suggest that a time-dependent series of extractions could be developed as a functional assay to determine the dissolution rate constant.
View details for DOI 10.1021/acs.est.6b04705
View details for Web of Science ID 000394724300037
View details for PubMedID 28106997
- In Situ Measurement of CuO and Cu(OH)(2) Nanoparticle Dissolution Rates in Quiescent Freshwater Mesocosms ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS 2016; 3 (10): 375–80
Impact of metal and metal oxide nanoparticle speciation and solubility on their bioavailability to terrestrial and aquatic plants
AMER CHEMICAL SOC. 2016
View details for Web of Science ID 000431460204309
Thermal decomposition of nano-enabled thermoplastics: Possible environmental health and safety implications
JOURNAL OF HAZARDOUS MATERIALS
2016; 305: 87–95
Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of widely used NEPs, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications.
View details for DOI 10.1016/j.jhazmat.2015.11.001
View details for Web of Science ID 000369451400010
View details for PubMedID 26642449
View details for PubMedCentralID PMC4707061
Toward a mechanistic understanding of the effect of natural organic matter coatings on nanoparticle aggregation
AMER CHEMICAL SOC. 2015
View details for Web of Science ID 000411186500174
Correlation of the Physicochemical Properties of Natural Organic Matter Samples from Different Sources to Their Effects on Gold Nanoparticle Aggregation in Monovalent Electrolyte
ENVIRONMENTAL SCIENCE & TECHNOLOGY
2015; 49 (4): 2188–98
Engineered nanoparticles (NPs) released into natural environments will interact with natural organic matter (NOM) or humic substances, which will change their fate and transport behavior. Quantitative predictions of the effects of NOM are difficult because of its heterogeneity and variability. Here, the effects of six types of NOM and molecular weight fractions of each on the aggregation of citrate-stabilized gold NPs are investigated. Correlations of NP aggregation rates with electrophoretic mobility and the molecular weight distribution and chemical attributes of NOM (including UV absorptivity or aromaticity, functional group content, and fluorescence) are assessed. In general, the >100 kg/mol components provide better stability than lower molecular weight components for each type of NOM, and they contribute to the stabilizing effect of the unfractionated NOM even in small proportions. In many cases, unfractionated NOM provided better stability than its separated components, indicating a synergistic effect between the high and low molecular weight fractions for NP stabilization. Weight-averaged molecular weight was the best single explanatory variable for NP aggregation rates across all NOM types and molecular weight fractions. NP aggregation showed poorer correlation with UV absorptivity, but the exponential slope of the UV-vis absorbance spectrum was a better surrogate for molecular weight. Functional group data (including reduced sulfur and total nitrogen content) were explored as possible secondary parameters to explain the strong stabilizing effect of a low molecular weight Pony Lake fulvic acid sample to the gold NPs. These results can inform future correlations and measurement requirements to predict NP attachment in the presence of NOM.
View details for DOI 10.1021/es505003d
View details for Web of Science ID 000349806400027
View details for PubMedID 25611369
Properties of various natural organic matter samples that control gold nanoparticle aggregation
AMER CHEMICAL SOC. 2014
View details for Web of Science ID 000348457600274