DISTRIBUTIONS AND FATE OF CHLORINATED PESTICIDES, BIOMARKERS AND POLYCYCLIC AROMATIC-HYDROCARBONS IN SEDIMENTS ALONG A CONTAMINATION GRADIENT FROM A POINT-SOURCE IN SAN-FRANCISCO BAY, CALIFORNIA

The distribution and fate of chlorinated pesticides, biomarkers, and p olycyclic aromatic hydrocarbons (PAHs) in surficial sediments along a contamination gradient in the Lauritzen Canal and Richmond Harbor in S an Francisco Bay was investigated. Compounds were identified and quant ified using gas chromatography-ion trap mass spectrometry. Biomarkers and PAHs were derived primarily from weathered petroleum. DDT was redu ctively dechlorinated under anoxic conditions to DDD and several minor degradation products, DDMU, DDMS, and DDNU. Under aerobic conditions, DDT was dehydrochlorinated to DDE and DBP. Aerobic degradation of DDT was diminished or inhibited in zones of high concentration, and incre ased significantly in zones of lower concentration. Other chlorinated pesticides identified in sediment included dieldrin and chlordane isom ers. Multivariate analysis of the distributions of the DDTs suggested that there ave probably two sources of DDD. In addition, DDE and DDMU ave probably formed by similar mechanisms, i.e. dehydrochlorination. A steep concentration gradient existed from the Canal to the Outer Rich mond Harbor, but higher levels of DDD than those found in the remainde r of the Bay indicated that these contaminants are transported on part iculates and colloidal organic matter from this source into San Franci sco Bay. Chlorinated pesticides and PAHs may pose a potential problem to biota in San Francisco Bay.