Profiles and inventories of organic pollutants in sediments from the central Beibu Gulf and its coastal mangroves

• First organic pollution history of central Beibu Gulf, South China Sea.
• Local and regional pollution recorded despite tide and storm influence.
• Changing BaA/(BaA + Phe) and Ant/(Ant + Phen) ratios reflect phases in use of energy carriers.
• First conservative estimate of mangrove sediment POP inventory.
• Mangrove are relatively small reservoirs with potential as local sinks.

Sediment cores from the central Beibu Gulf and its northern coastal mangroves were analyzed for polycyclic aromatic hydrocarbons (PAH), the organo-chlorine pesticides dichlorodiphenyltrichloroethane (DDT) and hexachlorobenzene (HCB), and polychlorinated biphenyls (PCB), to reconstruct the organic pollution history of developing south-west China. Reflecting regional development, in the gulf ∑PAH (38–74 ng g−1) decreased towards the surface after peak concentrations near 10 cm, while ∑DDT (ND – 0.5 ng g−1) increased due to fresh inputs, and HCB (ND – 0.04 ng g−1) occurred only in surface sediments. Profiles in mangrove sediments showed a continuing local scale increase in ∑PAH (29–438 ng g−1) as well as ∑DDT (0.2–41.0 ng g−1) and HCB (0.01–1.01 ng g−1) pollution, despite some variability. No trend was evident for ∑PCB (ND – 0.22 ng g−1), which was not detected in the central gulf. Calculated loads estimate that 2816 ng cm−2 PAHs and 7 ng cm−2 DDTs are stored in depositional areas of the Beibu Gulf. Mangrove sediments, threatened by land-use-change, contain 1400–4600 ng cm−2 PAHs and 34–39 ng cm−2 DDTs.