Kinetics of Methylmercury Production Revisited
Abstract
Laboratory measurements of the biologically mediated methylation of mercury (Hg) to the neurotoxin monomethylmercury (MMHg) often exhibit kinetics that are inconsistent with first-order kinetic models. Using time-resolved measurements of filter passing Hg and MMHg during methylation/demethylation assays, a multisite kinetic sorption model, and reanalyses of previous assays, we show in this paper that competing kinetic sorption reactions can lead to time-varying availability and apparent non-first-order kinetics in Hg methylation and MMHg demethylation. The new model employing a multisite kinetic sorption model for Hg and MMHg can describe the range of behaviors for time-resolved methylation/demethylation data reported in the literature including those that exhibit non-first-order kinetics. Additionally, we show that neglecting competing sorption processes can confound analyses of methylation/demethylation assays, resulting in rate constant estimates that are systematically biased low. Finally, simulations of MMHg production and transport in a hypothetical periphyton biofilm bed illustrate the implications of our new model and demonstrate that methylmercury production may be significantly different than projected by single-rate first-order models.
- Authors:
-
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division
- Publication Date:
- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- OSTI Identifier:
- 1423042
- Grant/Contract Number:
- AC05-00OR22725
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Environmental Science and Technology
- Additional Journal Information:
- Journal Volume: 52; Journal Issue: 4; Journal ID: ISSN 0013-936X
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES
Citation Formats
Olsen, Todd A., Muller, Katherine A., Painter, Scott L., and Brooks, Scott C. Kinetics of Methylmercury Production Revisited. United States: N. p., 2018.
Web. doi:10.1021/acs.est.7b05152.
Olsen, Todd A., Muller, Katherine A., Painter, Scott L., & Brooks, Scott C. Kinetics of Methylmercury Production Revisited. United States. https://doi.org/10.1021/acs.est.7b05152
Olsen, Todd A., Muller, Katherine A., Painter, Scott L., and Brooks, Scott C. Sat .
"Kinetics of Methylmercury Production Revisited". United States. https://doi.org/10.1021/acs.est.7b05152. https://www.osti.gov/servlets/purl/1423042.
@article{osti_1423042,
title = {Kinetics of Methylmercury Production Revisited},
author = {Olsen, Todd A. and Muller, Katherine A. and Painter, Scott L. and Brooks, Scott C.},
abstractNote = {Laboratory measurements of the biologically mediated methylation of mercury (Hg) to the neurotoxin monomethylmercury (MMHg) often exhibit kinetics that are inconsistent with first-order kinetic models. Using time-resolved measurements of filter passing Hg and MMHg during methylation/demethylation assays, a multisite kinetic sorption model, and reanalyses of previous assays, we show in this paper that competing kinetic sorption reactions can lead to time-varying availability and apparent non-first-order kinetics in Hg methylation and MMHg demethylation. The new model employing a multisite kinetic sorption model for Hg and MMHg can describe the range of behaviors for time-resolved methylation/demethylation data reported in the literature including those that exhibit non-first-order kinetics. Additionally, we show that neglecting competing sorption processes can confound analyses of methylation/demethylation assays, resulting in rate constant estimates that are systematically biased low. Finally, simulations of MMHg production and transport in a hypothetical periphyton biofilm bed illustrate the implications of our new model and demonstrate that methylmercury production may be significantly different than projected by single-rate first-order models.},
doi = {10.1021/acs.est.7b05152},
journal = {Environmental Science and Technology},
number = 4,
volume = 52,
place = {United States},
year = {Sat Jan 27 00:00:00 EST 2018},
month = {Sat Jan 27 00:00:00 EST 2018}
}
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Figures / Tables:
Figure 1: Hg methylation/MMHg demethylation conceptual model incorporating changing Hg/ MMHg availability. Subscripted “f” refers to fast sorption sites and the subscripted “s” refers to slow sorption sites. See Methods for explanation of symbols.
Figures / Tables found in this record: