Metal Concentrations of Sediment from 1993-2017 in San Francisco Bay-Delta Estuary (San Pablo Bay and Suisun Bay), CA

Surface sediment samples from the North San Francisco Bay-Delta Estuary were collected monthly at five stations located west of Rio Vista and east of Point Pinole. Sediment was collected near Montezuma Slough, Chips Island, the Concord Naval Weapons Station, Carquinez Strait near Martinez, and San Pablo Bay at water depths ranging from 6.5 to 14.3 meters. Samples were collected coincident with water-quality measurements (Cloern and Schraga, 2016) and metal concentrations in filter-feeding bivalves (Brown and Luoma, 1995; Stewart et al., 2013). Depending on the station, the period of record ranges from 13 to 24 years, from December 1993 to September 2017. Samples were sieved to <64 micrometers to eliminate grain-size bias and digested in hot, concentrated nitric acid for a near-total digest (Luoma and Bryan, 1981). Grain-size was also determined and is both seasonally and spatially variable. Sediments were analyzed for Aluminum, Arsenic, Chromium, Copper, Iron, Lead, Manganese, Nickel, Vanadium, and Zinc on an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Metal recoveries for this project were evaluated yearly using the standard reference material NIST 2709a-San Joaquin soils. This spatial and temporal documentation of metal concentrations in North San Francisco Bay sediments, and ancillary data, such as grain size, provides important baseline data that can be used to monitor future changes of metal contamination to San Francisco Bay. Figure 1 A The USGS R.V. Peterson. PC Rachel Keating B Morgan crane and ponar grab assembly used for benthic sampling. PC Rachel Keating C Collecting sediment from North San Francisco Bay. PC Kelly Shrader D Homogenized sediment in a mortar and pestle. PC Rachel Keating E Sediment samples digesting on hotplates. PC Rachel Keating F Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). PC Rachel Keating Figure 2 Sampling locations along the San Francisco Bay-Delta Estuary Station 2.1- Montezuma Slough Station 4.1- Chips Island Station 6.1- Concord Naval Weapons Station Station 8.1- Carquinez Strait Station 12.5- San Pablo Bay References: Brown, C. L., and Luoma, S. N., 1995, Use of the euryhaline bivalve Potamocorbula amurensis as a biosentinel species to assess trace metal contamination in San Francisco Bay: Marine Ecology Progress Series, v. 124, p. 129-142. Cloern, J. E., and Schraga, T.S., 2016, USGS measurements of water quality in San Francisco Bay (CA), 1969-2015: U. S. Geological Survey data release, https://doi.org/10.5066/F7TQ5ZPR. Luoma, S. N., and Bryan, G. W., 1981, A statistical assessment of the form of trace metals in oxidized estuarine sediments employing chemical extractants: Science of the Total Environment, v. 17, no. 17, p. 167-196. Stewart, A. R., Luoma, S. N., Elrick, K. A., Carter, J. L., van der Wegen, M., 2013, Influence of estuarine processes on spatiotemporal variation in bioavailable selenium: Marine Ecology Progress Series, v. 492, p. 41-56.