Mercury speciation in surface-waters of South San Francisco Bay, California

The southern portion of the San Francisco Bay (SFB) Estuary, California, is impacted by mercury (Hg) contamination associated with multiple sources, including: a) inputs from the Guadalupe River watershed, which drains the historic New Almaden Mercury Mining district, b) the entrainment of waters from the northern portion of SFB and the Sacramento-San Joaquin Delta, which are also impacted by historic Hg and gold mining in the upstream watersheds draining to them, and c) from contemporary urban and industrial Hg sources. This data release is in support of a larger study designed to use a combination of satellite remote sensing data and fixed station continuous monitoring data to estimate a range of Hg species in surface waters of southern SFB.

The data presented herein represents a combination of laboratory analytical results from surface water grab samples and from on-board sensor data collected by boat, at 12 primary southern SFB sampling sites, during ten field trips conducted between August 2022 and June 2024. Laboratory results from the discrete grab samples include the following analytes: filter-passing total Hg (THg), particulate THg (on both a volumetric and gravimetric basis), filter-passing methylmercury (MeHg), particulate MeHg (on both a volumetric and gravimetric basis), total suspended solids, and chlorophyll-a. On-board sensor data collected in the field include the following surface water parameters: temperature, pH, specific conductance, fluorescent dissolved organic matter, fluorescent chlorophyll, dissolved oxygen, and turbidity. The data is presented in two tables, which are in machine readable 'comma-separated values' format (*.csv): 1) ‘SSFB_Discrete’, the analytical results for the above grab sample constituents and the on-board sensor data; and B) ‘SSFB_QA’, a quality assurance data summary associated with the laboratory measurements for the grab-sample constituents. The analytical methods used are described in the metadata section of this product.