Bioaccumulation and cycling of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in three mangrove reserves of south China.

Total 22 organochlorine pesticides (OCPs) compounds and 31 polychlorinated biphenyls (PCBs) congeners in mangrove sediments and tissues (leaf, branch, root and fruit) of nine species from three Mangrove Reserves of China were studied. The mean concentrations of total DDTs, HCHs, OCPs and PCBs in sediments were 2.84, 0.06, 3.84 and 0.17 ng g-1 dw, while those in tissues were 1.85, 0.22, 9.43 and 1.61 ng g-1 dw, respectively. The elevated OCPs and PCBs levels in mangrove leaves may be caused by atmospheric sedimentation. The biota sediment accumulation factor (BSAF) values of both OCPs (mean: 3.4) and PCBs (mean: 9.9) are generally larger than one, implying mangroves' bioaccumulation and their ability to intercept pollutants. The BSAFs of PCBs in mangrove tissues were negatively correlated with the PCB congener's octanol-water partition coefficients (KOW, R = 0.58, n = 31, p < 0.001), suggesting that lower chlorinated CB congeners are more bioaccumulative in mangroves. In order to better understanding the fate of these organochlorine compounds, the cycling (including the standing accumulation, the annual absorption, the annual net retention, the annual return, and the turnover period) of OCPs and PCBs in the Mangrove Reserves were estimated, and the results indicated that mangroves are playing important roles in retaining OCPs and PCBs.