Southern California Coastal Water Research Project
A Public Agency for Environmental Research
Sediment Processes
Sources of Contamination to Coastal Areas
Bays and estuaries contain some of the most contaminated sediments in the state since they were often heavily industrialized in the past and may still receive contaminants from a variety of sources. Common contaminant sources into bays and estuaries include wastewater discharges, stormwater runoff, and accidental spills and releases. Contaminants may be easily transferred from the watershed upstream by attaching to particles (soil and organic material), which can be suspended in water and transferred long distances down rivers or creeks. Upon reaching the ocean, low current speeds and calm water often allow these particles (some of which contain contaminants) to be deposited as sediments.
Influences on Contaminants in Coastal Areas
Many factors affect the ultimate impact of sediment contamination. First, the types of contamination sources determine the overall magnitude and patterns of contaminant input. Physical mixing in bays and estuaries influences where contaminants settle. A variety of transformation processes can occur in the environment to change the chemical properties or form of the contaminant. Once these processes take place, the exposure level to a particular organism may depend on whether it ingests the sediments or consumes sediment-dwelling organisms. Thus, evaluating exposure levels from chemical measurements can be tricky.