Persistent organic pollutants in sediment cores from the southern region of the Bight of the Californias

Abstract

 In January 1998, four sediment cores were collected to reconstruct the history of contamination by persistent organic compounds in the southern region of the Bight of the Californias. Two groups of compounds were determined using chromatographic methods: petroleum hydrocarbons (aliphatic hydrocarbons, AHs, and polynuclear aromatic hydrocarbons, PAHs) and chlorinated hydrocarbons (pesticides and polychlorinated biphenyls, PCBs). The AHs had low concentrations, from 0.30 to 3.38 µg g^–1, and presented a biogenic allocthonous origin. The PAH concentrations ranged from 0.99 to 673 ng g^–1. The distribution of the alkyl homologues and the compound indices showed a clear predominance of PAHs of petrogenic origin. The chlorinated hydrocarbons presented a surface maximum, decreasing with depth to non-detectable levels. The PCB concentrations ranged from 0.18 to 7.15 ng g^–1 and pesticides from 0.09 to 19.71 ng g^–1. The pesticides that occurred most frequently were p,p'-DDT and its metabolites (p,p'-DDE and p,p'-DDD). Other pesticides detected were γ-chlordane and BHC isomers (α and γ). The statigraphy of the cores was carried out with molecular markers (chlorinated hydrocarbons), which were used to calculate a rate of sedimentation of 0.17 to 0.55 cm yr^–1.