Controls on stream water dissolved mercury in three mid‐Appalachian forested headwater catchments

摘要: [1] Determining the controls on dissolved mercury (HgD) transport is necessary to improve estimations of export from unmonitored watersheds and forecast responses changes in deposition other environmental forcings. Stream water HgD organic carbon (DOC) were evaluated over a range discharge conditions three streams within Shenandoah National Park, VA. Watersheds are distinguished by stream pH (ranging neutral acidic) soil size fractioning clays sands). At all sites, was significant but poor predictor concentrations (r2 0.13–0.52). strongly coupled with DOC at sites 0.74–0.89). UV absorbance 254 nm (UV254), proxy for quantity quality, slightly improved predictions HgD. Mean quality differed between streams, less aromatic mobilized more acidic watershed. The site sandy soils Hg same DOC, likely due reduced capacity larger-grained retain Hg, leaving greater fraction associated matter. A similar amount 0.54 ng HgD/mg transported suggesting transports per unit offsetting effects type. This research demonstrates that composition influence HgDexport. We also provide evidence primary control Hg-DOC ratios (0.12–1.4 mg−1) observed across U.S. Sweden.