Colette Kelly

All Publications

• pyisotopomer: A Python package for obtaining intramolecular isotope ratio differences from mass spectrometric analysis of nitrous oxide isotopocules. Rapid communications in mass spectrometry : RCM Kelly, C. L., Manning, C., Frey, C., Kaiser, J., Gluschankoff, N., Casciotti, K. L. 2023: e9513

  Abstract

  Obtaining nitrous oxide isotopocule measurements with isotope ratio mass spectrometry (IRMS) involves analyzing the ion current ratios of the nitrous oxide parent ion (N2 O+ ) as well as those of the NO+ fragment ion. The data analysis requires correcting for "scrambling" in the ion source, whereby the NO+ fragment ion obtains the outer N atom from the N2 O molecule. While descriptions exist for this correction, and interlaboratory intercalibration efforts have been made, there has yet to be published a package of code for implementing isotopomer calibrations.We developed a user-friendly Python package (pyisotopomer) to determine two coefficients (γ and κ) that describe scrambling in the IRMS ion source, and then to use this calibration to obtain intramolecular isotope deltas in N2 O samples.With two appropriate reference materials, γ and κ can be determined robustly and accurately for a given IRMS. An additional third reference material is needed to define the zero-point of the delta scale. We show that IRMS scrambling behavior can vary with time, necessitating regular calibrations. Finally, we present an intercalibration between two IRMS laboratories, using pyisotopomer to calculate γ and κ, and to obtain intramolecular N2 O isotope deltas in lake water unknowns.Given these considerations, we discuss how to use pyisotopomer to obtain high-quality N2 O isotopocule data from IRMS systems, including the use of appropriate reference materials and frequency of calibration.

  View details for DOI 10.1002/rcm.9513

  View details for PubMedID 36971184

• Nitrite cycling in the primary nitrite maxima of the eastern tropical NorthPacific BIOGEOSCIENCES Travis, N. M., Kelly, C. L., Mulholland, M. R., Casciotti, K. L. 2023; 20 (2): 325-347

  View details for DOI 10.5194/bg-20-325-2023

  View details for Web of Science ID 000917676100001

• Kinetics of nitrous oxide production from ammonia oxidation in the Eastern Tropical North Pacific LIMNOLOGY AND OCEANOGRAPHY Frey, C., Sun, X., Szemberski, L., Casciotti, K. L., Garcia-Robledo, E., Jayakumar, A., Kelly, C. L., Lehmann, M. F., Ward, B. B. 2022

  View details for DOI 10.1002/lno.12283

  View details for Web of Science ID 000898171000001

• Coincident Biogenic Nitrite and pH Maxima Arise in the Upper Anoxic Layer in the Eastern Tropical North Pacific GLOBAL BIOGEOCHEMICAL CYCLES Cinay, T., Dumit, D., Woosley, R. J., Boles, E. L., Kwiecinski, J., Mullen, S., Tamasi, T. J., Wolf, M. J., Kelly, C. L., Travis, N. M., Casciotti, K. L., Babbin, A. R. 2022; 36 (12)

  View details for DOI 10.1029/2022GB007470

  View details for Web of Science ID 000924445900001

• Identifying the Sources and Drivers of Nitrous Oxide Accumulation in the Eddy-Influenced Eastern Tropical North Pacific Oxygen-Deficient Zone GLOBAL BIOGEOCHEMICAL CYCLES Monreal, P. J., Kelly, C. L., Travis, N. M., Casciotti, K. L. 2022; 36 (6)

  View details for DOI 10.1029/2022GB007310

  View details for Web of Science ID 000811164200001

• Quantifying Nitrous Oxide Cycling Regimes in the Eastern Tropical North Pacific Ocean With Isotopomer Analysis Global Biogeochemical Cycles Kelly, C. L., Travis, N. M., Baya, P. A., Casciotti, K. L. 2021; 35 (2): e2020GB006637

  View details for DOI 10.1029/2020GB006637

• Microbial N2O consumption in and above marine N2O production hotspots. The ISME journal Sun, X., Jayakumar, A., Tracey, J. C., Wallace, E., Kelly, C. L., Casciotti, K. L., Ward, B. B. 2020

  Abstract

  The ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

  View details for DOI 10.1038/s41396-020-00861-2

  View details for PubMedID 33349653

• Amperometric sensor for nanomolar nitrous oxide analysis. Analytica chimica acta Damgaard, L. R., Kelly, C. n., Casciotti, K. n., Ward, B. B., Revsbech, N. P. 2020; 1101: 135–40

  Abstract

  Nitrous oxide is an important greenhouse gas and there is a need for sensitive techniques to study its distribution in the environment at concentrations near equilibrium with the atmosphere (9.6 nM in water at 20 °C). Here we present an electrochemical sensor that can quantify N2O in the nanomolar range. The sensor principle relies on a front guard cathode placed in front of the measuring cathode. This cathode is used to periodically block the flux of N2O towards the measuring cathode, thereby creating an amplitude in the signal. This signal amplitude is unaffected by drift in the baseline current and can be read at very high resolution, resulting in a sensitivity of 2 nM N2O for newly constructed sensors. Interference from oxygen is prevented by placing the front guard cathode in oxygen-consuming electrolyte. The sensor was field tested by measuring an N2O profile to a depth of 120 m in the oxygen minimum zone of the Eastern Tropical North Pacific Ocean (ETNP) off the coast of Mexico.

  View details for DOI 10.1016/j.aca.2019.12.019

  View details for PubMedID 32029104

• Quantitative drinking water arsenic concentrations in field environments using mobile phone photometry of field kits SCIENCE OF THE TOTAL ENVIRONMENT Haque, E., Mailloux, B. J., de Wolff, D., Gilioli, S., Kelly, C., Ahmed, E., Small, C., Ahmed, K., van Geen, A., Bostick, B. C. 2018; 618: 579–85

  Abstract

  Arsenic (As) groundwater contamination is common yet spatially heterogeneous within most environments. It is therefore necessary to measure As concentrations to determine whether a water source is safe to drink. Measurement of As in the field involves using a test strip that changes color in the presence of As. These tests are relatively inexpensive, but results are subjective and provide binned categorical data rather than exact determinations of As concentration. The goal of this work was to determine if photos of field kit test strips taken on mobile phone cameras could be used to extract more precise, continuous As concentrations. As concentrations for 376 wells sampled from Araihazar, Bangladesh were analyzed using ICP-MS, field kit and the new mobile phone photo method. Results from the field and lab indicate that normalized RGB color data extracted from images were able to accurately predict As concentrations as measured by ICP-MS, achieving detection limits of 9.2μg/L, and 21.9μg/L for the lab and field respectively. Data analysis is most consistent in the laboratory, but can successfully be carried out offline following image analysis, or on the mobile phone using basic image analysis software. The accuracy of the field method was limited by variability in image saturation, and variation in the illumination spectrum (lighting) and camera response. This work indicates that mobile phone cameras can be used as an analytical tool for quantitative measures of As and could change how water samples are analyzed in the field more widely, and that modest improvements in the consistency of photographic image collection and processing could yield measurements that are both accurate and precise.

  View details for DOI 10.1016/j.scitotenv.2016.12.123

  View details for Web of Science ID 000424130500059

  View details for PubMedID 29102200

  View details for PubMedCentralID PMC5773362

• Dancing up the glass escalator: Institutional advantages for men in ballet choreography Columbia Undergraduate Research Journal Kelly, C. L. 2017; 1 (2)

  View details for DOI 10.7916/D8R78MJX