How Does Dissolved Organic Matter Impact Microbial Arsenic Transformations?

Abstract. Growing awareness of elevated concentrations of arsenic in rice have motivated significant research attention to the biogeochemical dynamics of arsenic in rice paddy soils. However, fundamental understanding of how environmental conditions regulate microbe-mediated arsenic transformations - and the resulting impacts on arsenic speciation and fate - is lacking. This presentation explores the multi-faceted role of dissolved organic matter (DOM) quality and quantity in regulating microbial uptake and transformation of arsenic, with a focus on methylation-demethylation reactions. The presentation will discuss: (i) Bioavailability of arsenic in the presence of DOM-stabilized iron colloids; (ii) Effects of bio-labile carbon in suppressing microbial uptake and methylation of arsenic through a carbon catabolite repression-like mechanism; and (iii) Effects of methylated organic substrates for methylotrophic methanogenesis on stimulating the demethylation of methylarsenic species. Implications of the research findings for concentrations of inorganic and methylated arsenic species in rice paddy soils will be discussed.

Bio. Dr. Matthew Reid is an assistant professor in the School of Civil and Environmental Engineering at Cornell University and directs the Biogeochemistry and Ecosystem Engineering Research Group. Research in the Reid Lab focuses on applications of biogeochemistry and ecosystem engineering to water quality problems and greenhouse gas emissions from environmental processes. The Reid Lab performs research across physical scales from molecular-level investigations and modeling to field-scale observations and experiments. Dr. Reid was a postdoctoral scientist in the Environmental Microbiology Laboratory at the Swiss Federal Institute of Technology, Lausanne (EPFL), where he was supported by a Marie Sklodowska-Curie fellowship. Dr. Reid completed his Ph.D. in Civil and Environmental Engineering at Princeton University in 2014 and received his bachelors degree in chemistry from the University of Chicago. Dr. Reid has also worked as a high school chemistry teacher with the United States Peace Corps in Tanzania.