Hydrological controls on methylmercury distribution and flux in a tidal marsh
Environmental Science & Technology
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Abstract
The San Francisco Estuary, California, contains mercury (Hg) contamination originating from historical regional gold and Hg mining operations. We measured hydrological and geochemical variables in a tidal marsh of the Palo Alto Baylands Nature Preserve to determine the sources, location, and magnitude of hydrological fluxes of methylmercury (MeHg), a bioavailable Hg species of ecological and health concern. Based on measured concentrations and detailed finite-element simulation of coupled surface water and saturated-unsaturated groundwater flow, we found pore water MeHg was concentrated in unsaturated pockets that persisted over tidal cycles. These pockets, occurring over 16% of the marsh plain area, corresponded to the marsh root zone. Groundwater discharge (e.g., exfiltration) to the tidal channel represented a significant source of MeHg during low tide. We found that nonchannelized flow accounted for up to 20% of the MeHg flux to the estuary. The estimated net flux of filter-passing (0.45 μm) MeHg toward estuary was 10 ± 5 ng m–2 day–1 during a single 12-h tidal cycle, suggesting an annual MeHg load of 1.17 ± 0.58 kg when the estimated flux was applied to present tidal marshes and planned marsh restorations throughout the San Francisco Estuary.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Hydrological controls on methylmercury distribution and flux in a tidal marsh |
| Series title | Environmental Science & Technology |
| DOI | 10.1021/es500781g |
| Volume | 48 |
| Issue | 12 |
| Year Published | 2014 |
| Language | English |
| Publisher | American Chemical Society |
| Publisher location | Easton, PA |
| Contributing office(s) | National Research Program - Western Branch |
| Description | 10 p. |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Environmental Science and Technology |
| First page | 6795 |
| Last page | 6804 |
| Google Analytic Metrics | Metrics page |