The role of sediment resuspension on estuarine suspended particulate mercury dynamics

摘要

Coastal sediments are an important site for transient and long-term mercury (Hg) storage and they foster a geochemical environment optimal for Hg methylation. Therefore, efforts have been taken to constrain the role of sediments as a source of methylmercury (MeHg) to the estuarine water column. This study employed the Gust Microcosm Erosion Core system capable of quantifying particle removal from undisturbed cores under measurable shear stress conditions to assess particulate Hg and MeHg exchange between sediments and the water column. Samples were collected from organic rich and organic poor sediment types from the mid- and lower- Delaware Bay. It was found that bulk sediment samples from organic rich systems overpredict total Hg and MeHg release to the water column whereas organic poor sediments under-predict the exchange. In general, organic rich sediments in shallow environments have the most impact on surface particle dynamics. There is little evidence to suggest that MeHg formed in the sediments is released to the water column via particulate exchange, and therefore non-sedimentary sources likely control MeHg levels in this estuarine water column.