Effect of dissolved organic matter source and character on microbial Hg methylation in Hg–S–DOM solutions
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Abstract
Dissolved organic matter (DOM) is a key component of fate and transport models for most metals, including mercury (Hg). Utilizing a suite of diverse DOM isolates, we demonstrated that DOM character, in addition to concentration, influences inorganic Hg (Hg(II)i) bioavailability to Hg-methylating bacteria. Using a model Hg-methylating bacterium, Desulfovibrio desulfuricansND132, we evaluated Hg-DOM-sulfide bioavailability in washed-cell assays at environmentally relevant Hg/DOM ratios (∼1–8 ng Hg/mg C) and sulfide concentrations (1–1000 μM). All tested DOM isolates significantly enhanced Hg methylation above DOM-free controls (from ∼2 to >20-fold for 20 mg C/L DOM solutions), but high molecular weight/highly aromatic DOM isolates and/or those with high sulfur content were particularly effective at enhancing Hg methylation. Because these experiments were conducted under conditions of predicted supersaturation with respect to metacinnabar (β-HgS(s)), we attribute the DOM-dependent enhancement of Hg(II)i bioavailability to steric and specific chemical (e.g., DOM thiols) inhibition of β-HgS(s) growth and aggregation by DOM. Experiments examining the role of DOM across a wide sulfide gradient revealed that DOM only enhances Hg methylation under fairly low sulfide conditions (≲30 μM), conditions that favor HgS nanoparticle/cluster formation relative to dissolved HgS species.
Suggested Citation
Graham, A.M., Aiken, G.R., and Gilmour, C., 2013, Effect of dissolved organic matter source and character on microbial Hg methylation in Hg–S–DOM solutions: Environmental Science & Technology, v. 47, no. 11, p. 5746-5754, https://doi.org/10.1021/es400414a.
ISSN: 1520-5851 (online)
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Effect of dissolved organic matter source and character on microbial Hg methylation in Hg–S–DOM solutions |
| Series title | Environmental Science & Technology |
| DOI | 10.1021/es400414a |
| Volume | 47 |
| Issue | 11 |
| Publication Date | May 16, 2013 |
| Year Published | 2013 |
| Language | English |
| Publisher | ACS |
| Contributing office(s) | National Research Program - Central Branch |
| Description | 9 p. |
| First page | 5746 |
| Last page | 5754 |