Polycyclic aromatic hydrocarbon (PAH) contamination in San Francisco Bay: A 10-year retrospective of monitoring in an urbanized estuary

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 (10,700 kg/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 1000 ng/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.