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 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. 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.
| Original language | English |
|---|---|
| Pages (from-to) | 2063-2070 |
| Number of pages | 8 |
| Journal | Environmental Science and Technology |
| Volume | 52 |
| Issue number | 4 |
| DOIs | |
| State | Published - Feb 20 2018 |
Funding
*E-mail: [email protected]. Tel: 865-574-6398. Fax: 865-576-8646. ORCID Scott C. Brooks: 0000-0002-8437-9788 Present Address †(T.A.O.) Geosnytec Consultants, 3043 Goal Canal Drive, Suite 100, Rancho Cordova, CA, 95670. Notes This manuscript has been authored by UT−Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). The authors declare no competing financial interest. This work was funded by the U.S. Department of Energy, Office of Science, Biological and Environmental Research, Subsurface Biogeochemical Research (SBR) Program, and is a product of the SBR Science Focus Area (SFA) at ORNL. The isotopes used in this research were supplied by the United States Department of Energy Office of Science by the Isotope Program in the Office of Nuclear Physics.
| Funders | Funder number |
|---|---|
| Office of Nuclear Physics | |
| Office of Science, Biological and Environmental Research | SBR |
| United States Department of Energy Office of Science | |
| U.S. Department of Energy | |
| Oak Ridge National Laboratory | |
| Stephen F. Austin State University | |
| University of Tampa |