Analysis of Factors Causing Mercury Impairment in Water Bodies of the Sierra Nevada, California Completed
The SWRCB has requested assistance from the USGS in analyzing the factors that control Hg concentrations in fish tissue in the Sierra Nevada. Specifically, the SWRCB wants to know whether Hg and (or) MeHg in bed sediment and (or) suspended sediment could be potentially useful in the future as a 303(d) listing criteria. The SWRCB has requested that the USGS perform an analysis of existing data for Hg in fish and Hg and MeHg in sediment to evaluate whether a threshold concentration of Hg in sediment can be determined which consistently (for example, with 90 % confidence) is associated spatially with Hg concentrations of fish tissue above current or proposed regulatory thresholds (i.e., 0.2 or 0.3 µg/g, wet). In addition, the SWRCB wants to know whether geospatial analysis could be used to develop a quantitative relationship between Hg in fish tissue and the intensity of historical gold mining in Sierra Nevada watersheds.
The primary objective of this project is to describe the occurrence and distribution of total mercury (THg) in fish tissue in water bodies in the Sierra Nevada of California in relation to factors that are thought to affect Hg bioaccumulation, including wetland and other land-use/land-cover (LULC) types and historical gold mining. Secondary objectives are: (1) to evaluate concentrations of THg and MeHg in bed sediment and surface water in relation to these factors and (2) to identify ecosystem characteristics that favor the production and bioaccumulation of MeHg.
The study is designed in two phases: Phase I will use existing data and Phase II will use newly collected data. The purposes of the first phase are to give the cooperator (SWRCB) a useful product as soon as possible and to develop an understanding of the most critical data gaps to be filled during Phase II to improve the analysis. Phase 1 will use existing data to investigate possible correlations between fish tissue Hg concentrations in Sierra Nevada water bodies and various other parameters, including water and sediment chemistry, watershed characteristics such as LULC, and distribution and production of historical gold mines. The approach will be based in large part on that used by Scudder et al. (2009) in their national-scale analysis of fish tissue Hg data from the NAWQA program, and will include participation from the WI WSC. The results from Phase I will be used to design a field sampling campaign intended to fill data gaps for at least 15 water bodies (streams, reservoirs, and (or) lakes) in the Sierra Nevada. In Phase II, the newly collected data (sediment and water by USGS, fish by UC Davis) will be combined with pre-existing data and the correlation analysis will be revisited.
The SWRCB has requested assistance from the USGS in analyzing the factors that control Hg concentrations in fish tissue in the Sierra Nevada. Specifically, the SWRCB wants to know whether Hg and (or) MeHg in bed sediment and (or) suspended sediment could be potentially useful in the future as a 303(d) listing criteria. The SWRCB has requested that the USGS perform an analysis of existing data for Hg in fish and Hg and MeHg in sediment to evaluate whether a threshold concentration of Hg in sediment can be determined which consistently (for example, with 90 % confidence) is associated spatially with Hg concentrations of fish tissue above current or proposed regulatory thresholds (i.e., 0.2 or 0.3 µg/g, wet). In addition, the SWRCB wants to know whether geospatial analysis could be used to develop a quantitative relationship between Hg in fish tissue and the intensity of historical gold mining in Sierra Nevada watersheds.
The primary objective of this project is to describe the occurrence and distribution of total mercury (THg) in fish tissue in water bodies in the Sierra Nevada of California in relation to factors that are thought to affect Hg bioaccumulation, including wetland and other land-use/land-cover (LULC) types and historical gold mining. Secondary objectives are: (1) to evaluate concentrations of THg and MeHg in bed sediment and surface water in relation to these factors and (2) to identify ecosystem characteristics that favor the production and bioaccumulation of MeHg.
The study is designed in two phases: Phase I will use existing data and Phase II will use newly collected data. The purposes of the first phase are to give the cooperator (SWRCB) a useful product as soon as possible and to develop an understanding of the most critical data gaps to be filled during Phase II to improve the analysis. Phase 1 will use existing data to investigate possible correlations between fish tissue Hg concentrations in Sierra Nevada water bodies and various other parameters, including water and sediment chemistry, watershed characteristics such as LULC, and distribution and production of historical gold mines. The approach will be based in large part on that used by Scudder et al. (2009) in their national-scale analysis of fish tissue Hg data from the NAWQA program, and will include participation from the WI WSC. The results from Phase I will be used to design a field sampling campaign intended to fill data gaps for at least 15 water bodies (streams, reservoirs, and (or) lakes) in the Sierra Nevada. In Phase II, the newly collected data (sediment and water by USGS, fish by UC Davis) will be combined with pre-existing data and the correlation analysis will be revisited.