Transport and fate of organochlorines discharged to the salt marsh at Upper Newport Bay, California, USA

Despite long-term monitoring of water quality in the coastal lagoons of California, USE, the fate of organochlorines discharged from agricultural and urban sources to salt marsh habitats has received little attention. We measured organochlorine concentrations in Upper Newport Bay marsh and channel sediments and salt marsh plants. Sediment grain-size analyses show that organochlorines are fractionated and concentrated in the organic material traveling with the clay fraction of the washload discharged into the bay from San Diego Creek. Hydrophobic compounds such as DDT are not associated with the sand and silt fractions. The most frequently detected analyte was p,p'-1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE), occurring in 100% of the sediment samples and 87% of the plant root samples. Maximum concentrations in sediment were 122 ng/g (dry wt) for DDE and 162 ng/g DDT plus metabolites (Sigma DDT) in salt marsh deposited since 1980. Ratios of DDT to its metabolites suggest that anaerobic degradation of DDT occurs in the cordgrass (Spartina foliosa Trin.) sediments. Cordgrass and pickleweed (Salicornia virginica L.) partition organochlorine residues to the root epidermis, attaining values of 50,000 ng/g lipid for Sigma DDT and 80,000 ng/g lipid for heptachlorepoxide (1,4,5,6,7,8,8-heptachloro-2,3-epoxy-3 alpha,4,7,7 alpha-tetrahydro-4,7-methanoindan).