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Abstract: Monitoring sediment quality and total mercury concentrations over the period 1993–2001 at 26 stations in San Francisco Estuary has shown the seasonal cycling of mercury sediment concentrations, as well as a significant () decrease in those concentrations at eight stations across the estuary. This decrease in sediment mercury concentrations is attributed to the transport of relatively cleaner sediment to the estuary from the Sacramento River and San Joaquin River watersheds. Despite the decreases observed in some parts of the estuary, no corresponding trend has been found in concurrent studies on sport fish and bivalves in the estuary. [Copyright &y& Elsevier]

Abstract: Polycyclic aromatic hydrocarbons (PAH) are widespread contaminants in the San Francisco Bay. Several exceedances of water quality criteria raise the possibility that PAH may be impacting aquatic biota. The Regional Monitoring Program for Water Quality in the San Francisco Estuary (RMP) has collected annual monitoring data on PAH in the Bay since 1993. Analysis of Bay water, sediment, and mussel ΣPAH concentration data showed that there were very few significant (P<0.05) increasing or decreasing temporal trends in ΣPAH concentrations in the Bay during the period of 1993–2001. Wet and dry season input of PAH did not show any major influence on water ΣPAH concentrations over the same period. Based on their relative contribution to the estimated total maximum PAH loading (10,700kg/yr) into the Bay, the PAH loading pathways are ranked as storm water runoff (∼51%)>tributary inflow (∼28%)>wastewater treatment plant effluent (∼10%)>atmospheric deposition (∼8%)>dredged material disposal (∼2%). The PAH sediment quality threshold of 1000ng/g, which has been previously suggested by NOAA to protect estuarine fish such as English sole against adverse health effects, was frequently exceeded at individual monitoring stations (11 of the 26 stations exceeded the threshold over 50% of the time). Modeling results have shown that the predominant loss pathway for PAH is degradation in sediments, and unless external loading levels of PAH are controlled, the Bay is not expected to recover rapidly. [Copyright &y& Elsevier]

Abstract: Following basin-wide contamination from industrial emissions and urban development, total dissolved copper concentrations in some regions of San Francisco Bay have exceeded national and state guidelines for water quality. In the face of dramatic improvements in wastewater treatment and point source control, persisting elevated dissolved copper concentrations in the Bay have prompted multiple studies and extensive monitoring of this estuary since 1989. Statistical analyses of monitoring data show that total dissolved copper concentrations have declined in the North (by 17%) and South (29%) San Francisco Bay as well as in the Southern Sloughs (44%) from 1993 to 2001. Concentrations remain elevated in the farthest reaches of the Bay (Delta and Estuary Interface), and in the Central Bay. Dissolved copper concentrations throughout the Bay have also been positively correlated (, , ) with dissolved organic matter, supporting results from complimentary chemical speciation studies which indicate that high-affinity copper-binding organic ligands dominate the chemical speciation of dissolved copper in the Bay. These organic ligands typically bind>99.9% of the dissolved copper, effectively buffering the system against small changes in dissolved copper concentrations, and maintaining free Cu2+ concentrations well below the toxicity threshold of ambient aquatic microorganisms. In response to these findings, site-specific water quality criteria for dissolved copper concentrations are now being developed by the Regional Water Quality Board to provide a more appropriate standard for copper toxicity in the Bay—one based on its chemical speciation and bioavailability. [Copyright &y& Elsevier]