Sources, distribution and toxicity of organic pollutants in coastal and shelf sediments of developing southwest China

Abstract

Persistent organic pollutants are principally anthropogenic toxic compounds ubiquitously found in coastal marine sediments. As different compound classes derive from industrial and agricultural activities, we seek to investigate their composition, transport pathways, and potential toxicities in a developing region of southern China. Surface sediments were obtained from the Nanliu estuary, its mangroves and aquaculture ponds, as well as the enclosed Gulf of Tonkin. The absence of polychlorinated biphenyls (PCB; generally below detection limit), low concentrations of polycyclic aromatic hydrocarbons (PAH; 24-647 ng g-1), and locally high contamination with organo-chloro pesticides (DDT; 0.03-92 ng g-1) reflect the early stages of development in southwest China, with human activities dominated by agriculture and low impact of industry. In corroboration, diagnostic ratios suggest that PAH derive mainly from combustion of biomass and diesel fuels, and that technical DDT is recently used in agriculture and antifouling paint. Distribution patterns along the coastal-shelf-gradient indicate mainly airborne transport of PAH and waterborne transport of DDT. In comparison with sediment quality guidelines, concentrations of PCB and PAH indicate no ecological risk. Contrarily, the intensive use of pesticides has rendered DDT accumulation a probable toxic risk to sedimentary organisms and higher trophic levels, including human consumers of seafood.