Comparison of DGT sentinels and bioassays for long-term mercury TDML monitoring under San Francisco Bay
Best, E. P. H.; Hintelmann, H.; Clarisse, Oliver.; Furey, John S.; Greenfield, B.; Dimock, B.
Technical reportAbstract: Compliance with the mercury total mean daily load (TMDL) for San Francisco Bay adopted in 2004 requires long-term monitoring of mercury loadings from a range of sources, including extant and restored wetlands, into the Bay. This study explores the use of DGTs for long-term monitoring of MeHg in the field, by determining the performance of DGTs as indicators for potential MeHg accumulation at relevant field sites over a range of time periods (up to 28 days); comparing/ correlating the DGT results with MeHg bioaccumulation over the same time periods in originally 'clean' bioassay organisms (two clam species); and comparing/correlating the DGT results with the MeHg levels in site-inhabiting clams and small fish. The following conclusions can be reached based on study results: •DGT-labile MeHg concentrations of the water-DGTs were usually less than the unfiltered water concentrations. •The MeHg-time relationships of the water-DGTs differed from those of the +1.5-cm-sediment-DGTs. •The MeHg concentrations of the water-DGTs were not significantly related to those of M. nasuta test clams. •The MeHg concentrations of the water DGTs ranked similar to site as those of T. japonica test clams and, therefore, appeared to respond to the same processes. •The MeHg concentrations of the 14-day incubated water-DGTs were significantly related to those of the site-inhabiting clam Mya arenaria and weakly related to those of the site-inhabiting fish M. audens, and, therefore, water-DGTs appeared to respond to the same processes as these organisms.
Environmental Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Clams; Coastal wetlands; DGT; Fish; Management; Methylmercury; Monitoring; San Francisco Bay; Sediment
ERDC/EL TR ; 09-22.
Approved for public release; distribution is unlimited.