Data for monitoring trace metals in sediment and clam tissue near the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay, California (ver 3.0, July 2025)

Sediment particles can strongly bind metals, effectively repartitioning them from solution to a solid phase. As a result, sediments may accumulate and retain metals released to an aquatic environment. Sediment cores provide a historical record of metal inputs that can reveal anthropogenic influences (Förstner and Wittmann, 1979). Specifically, studies of sediment cores in San Francisco Bay chronicled metal inputs and suggested that legacy contamination can remain a chronic source of metals to the system owing to sediment mixing and redistribution (Hornberger and others, 1999; Van Geen and Luoma, 1999). Metals in sediments also indicate exposure levels to benthic animals through contact with, and ingestion of, bottom sediments and suspended particulate materials. However, physical and geochemical conditions of the sediment affect the biological availability of the bound metals. Assimilation of bioavailable sediment-bound metal by digestive processes and the contribution of this source of metals relative to metals in the aqueous phase are difficult to predict from sediment concentrations alone. Thus, in order to better estimate bioavailable metal exposures, the tissues of organisms may be analyzed for trace metals (Phillips and Rainbow, 1993). Different species concentrate metals to different degrees. However, if one species is analyzed consistently, the results can be used to track temporal changes in trace-element exposures at a specified location.
This data release includes the sediment and tissue metal data starting in January 2019 and is presented in 13 tables as comma-separated values (.CSV) files as follows: 
T1_Sediment_Summary as a summary of the fine sediment, silver, aluminum, chromium, copper, iron, mercury, nickel, selenium, zinc and total organic carbon in the sediment. 
T2_Sediment_Metals_ICPOES provides detailed silver, aluminum, chromium, copper, iron, mercury, nickel, selenium and zinc data collected by inductively coupled plasma-optical emission spectrophotometry (ICP-OES)
T3_Sediment_Hg_Se reports detailed mercury and selenium data
T4_TOC reports detailed total organic carbon data from the sediment
T5_Tissue_Metals reports the silver, chromium, copper, nickel, and zinc data collected from clams with the size and mass of the collected clam tissue for each sample date.
T6_Tissue_Hg_Se reports the mercury and selenium data collected from clam tissue collected by size fraction and collection date. 
T7_QA_ICPOES_Sediment_SRM reports the standard reference material run data for certified reference standards for sediment analyzed on the ICP-OES.
T8_QA_ICPOES_Tissue_SRM reports the standard reference material run data collected for certified standards for biological tissues analyzed on the ICP-OES.
T9_QA_Hg_ Se reports the standard reference materials run for mercury and selenium data
T10_QA_Spike_Recovery reports the spike recovery runs for the ICP-OES
T11_QA_ICPOES_Blanks reports the procedural blanks run on the ICP-OES
T12_QA_MDL_MRL reports the annual method detection limits and method reporting limits for the listed analyte
T13_QA_SRM_reference_values reports the reference values for each of the reported standard reference material included in this data release

Tags: aluminum, benthic-ecosystems, benthic-environments, benthos, biological-sampling, biota, bivalves, burrowing-organisms, chromium, copper, geochemistry, iron, mercury, metal-elements, metals, nickel, sediment-geochemistry, sediments, selenium, silver, usgs-606f2b79d34ef99870188994, zinc
Organization: Department of the Interior