Geochemical Data for Mercury and Other Constituents in Shallow Sediment and Porewater from Clear Lake, Lake County, California

Clear Lake, located in Lake County, California, is impacted by mercury contamination associated with the historic Sulfur Bank mercury mine, which is adjacent to the lake’s eastern shore / Oaks Arm region. As part of a larger study designed to better understand the biogeochemical cycling of mercury in Clear Lake, shallow sediment (top 0-2 cm or 0-4 cm) was sampled from the three major zones of the lake (Oaks Arm [east and west], Lower Arm, Upper Arm) during 2022 and 2023 to better map the distribution and chemical speciation of mercury throughout the system.

Analyses on bulk sediment included those for total mercury, methylmercury, reactive inorganic mercury, dry weight, loss on ignition, wet density, total reduced sulfur, acid-extractable ferrous iron, crystalline ferric iron, and amorphous (poorly crystalline) ferric iron. Analyses on sediment porewater, collected in the laboratory under anoxic conditions, included: total mercury, methylmercury, sulfate, chloride, dissolved organic carbon, and total dissolved nitrogen.

This data release documents the analytical results for the above bulk sediment and porewater constituents. It includes three data tables given as machine readable 'comma-separated values' format (*.csv): 1) ‘T1_CL_SED_DataDictionary’, the Data Dictionary, which provides definitions and details related to the other two data tables and includes citations of analytical methods; 2) ‘T2_CL_SED_Discrete’, the sediment sample analytical results for the above constituents; and 3) ‘T3_CL_SED_QA’, a quality assurance data summary associated with the laboratory measurements for the above constituents. The analytical methods used are described in the metadata section of this product.