Distribution Patterns Of Polycyclic Aromatic Hydrocarbon And Toxicokinetics In Bivalves From Lian And Xincun Bays, Hainan

Polycyclic aromatic hydrocarbons ?PAHs? are an important class of persistent organic pollutants ?POPs? containing two or more fused benzene rings. The primary petroleum product constituents most toxic to aquatic organisms are polycyclic aromatic hydrocarbons?PAHs?, which due to their lipophilic character ?low solubility?, tend to be adsorbed onto particles in marine water and ultimately accumulate in sediments. Due to their potential mutagenic, carcinogenic and hazardous risks to organisms and human beings, PAHs have received special environmental concerns and 16 of them have been listed as priority control pollutants by the environmental protection agency of the USA. They are of high priority for environmental pollution monitoring. Once the PAHs enter themarine environment, they can then readily be taken up by marine biota either through their gills or via ingestion. Therefore the present study aims to analyze the distribution patterns and sources of PAHs in surface seawater, sediments and bivalves form the Lian and Xincun Bay of China, and comparative Studies on the Toxicokinetics of Benzo[a]pyrene in Pinctada martensii and Perna viridis. The results may provide baseline information regarding the extent of PAHs contamination and make up for the limitations of previous investigations in the Lian and Xincun Bay. Such data may be helpful in policy making on sustainable development andmarine environmental conservation in the South China Sea.1. Levels, distribution, and sources of 16 PAHs in surface seawater and sediments from the Lian and Xincun Bay of China were investigated. The Lian and Xincun Bay of total concentrations of PAHs varied from 35.61 to 131.50 ng L^-1 and 172.56 to 800.34 ng L^-1 in seawater, respectively, and from 571.46 to 1186.01 ng g^-1 and 743.29 to 1044.42 ng g^-1 in sediments, respectively. PAH concentrations in seawater differed significantly in the Lian and Xincun Bay, whereas those in sediments exhibited a relatively stable pattern.PAHs with low molecular weight were predominant in seawater and sediments. The current levels of PAHs in the Lian and Xincun Bay are relatively moderate compared with those in other bays and estuaries. Petroleum products and pyrogenic sources were the main PAH pollution sources in seawater. The main sources of PAHs were Combustion sources including petroleum products and biomass combustion in sediments.2. The levels of 16 PAHs were determined in the adductor, liver, mantles, gills and gonad tissues of clam Pinctada martensii and mussel Perna viridis collected from coastal waters of the Lian and Xincun bay from September 2016. The distribution and composition pattern of PAHs in the different tissues of bivalves were analyzed. The levels of total PAHs in the various tissues of Pinctada martensii and Perna viridis ranged from 887.80 to 2623.83 ng g^-1 dw and 1181.35-2261.29 ng g^-1 dw, respectively. Pinctada martensii showed significantly higher levels of MWM-PAHs ?4-rings? than Perna viridis. The analysis has revealed a high degree of accumulation of the studied PAHs in the tissues of the both species. 2-?4-rings PAHs predominated in the bivalves. Among the sixteen tested PAHs, phenanthrene was the most dominant congener, followed by naphthalene and fluorene. The PAHs levels and distribution in the tissues of bivalves are dependent on both the K_ow of PAH congeners and the lipid content in these tissues.3. Benzo[a]pyrene ?B[a]P?,a typical polycyclic aromatic hydrocarbon ?PAH?,was a common pollutant in the marine environment. The uptake of PAH from sediment and water can contribute significantly to body burdens of deposit Feeders. Research on the kinetics of Benzo[a]pyrene ?B[a]P? bioaccumulation in the clam Pinctada martensii and mussel Perna viridis showed that the initial rate of uptake was directly related to the PAH concentrations in the ambient environment. The uptake and depuration rate constants were different at the four B[a]P exposure levels, which indicated that the toxicokinetic rate constants mainly depended on the exposure levels of pollutants to the environment. In addition, the uptake rate constants of B[a]P were higher than the depuration rate constants in the entire experiment. The comparison demonstrated that mussels release B[a]P more rapidly than clams. The bioconcentration factors ?BCFs? of B[a]P varied from 3335 to 12892 in the clam and 2373?6235 in the mussel. These findings on the bioaccumulation kinetics for petroleum hydrocarbons, in association with the critical body residue, will be valuable when choosing sensitive organisms to assess the potential ecotoxicological risk to the marine environment.