Temporal variability of selenium fluxes in San Francisco Bay

Abstract

Selenium is introduced into San Francisco Bay primarily via rivers and anthropogenic sources which include effluents from oil refineries and sewage treatment plants. These sources have unique concentration and chemical speciation signatures for selenium, allowing their input to the estuary to be traced. Of the selenium fluxes to San Francisco Bay, the anthropogenic contribution ranges from 52 to 90% of the total. The riverine flux of selenium varies considerably with time, while the anthropogenic fluxes are relatively constant. However, the freshwater residence time for the estuary varies with the riverine discharge rate, and thus the effect of anthropogenic inputs on the distribution and concentration of selenium species in San Francisco Bay also varies with time.