Bioaccumulation, Biomagnification And Distribution Of Organochlorine Pesticide (OCPs) In Aquatic Organisms Of Zhoushan Fishing Ground, China

Organochlorine Pesticides (OCPs) have the characteristics of environmental persistence, semi-volatility, transmission with long distance, high toxicity, bio-accumulation and bio-magnification in the food web. Eating seafood containing organochlorine pesticides is the main path of human beings exposed to this typical persistent organic pollutants. As a result, the concentrations, transformation and health risk of OCPs in marine organisms has received great attention around the world. Residues of12organochlorine pesticides and the enantiomeric fractions (EFs) of five chiral OCPs were investigated in20marine organisms collected from Zhoushan Fishing Ground, China, and the possible sources and health risk of these pollutants were ananlyzed. Moreover, based on the values of δ15Nfå'ŒÎ´13C isotopes, nutrition structure of the ecological system in the study area was constructed in order to survey bio-accumulation and bio-magnification of OCPs within the food web. In addition, OCPs concentrations in five tissues (muscle, liver, skin, fins, gills) of the dog shark (Mustelus griseus) were measured in order to discuss the possible mechanisms of distribution, metabolism and transformation of OCPs in this high trophic level marine animals. All of the investigation would provide theoretic basis and technical support for pollutant control and management, thus having great significance for protecting people’s health and safety.The main conclusions in the present thesis were as follows:(1)Total OCPs concentrations in zooplankton, macroalgae, Crustacea, cephalopoa, fish and cetacean ranged from0.81to0.83,0.87to1.64,0.51to32.28,2.89to4.22,1.44to39.18and79-111.27ng/g wet weight (ww) respectively. And the residues of DDTs, HCHs and chlordanes (CLDs) showed a decreasing trend. The composition profiles indicated that HCHs in marine organisms of Zhoushan Fishing Ground originated both from technical HCH and lindane, and that there were fresh inputs of dicofol and CLDs in the studied sea areas.(2)The enantiomeric fractions (EFs) of a-HCH were from0.437to0.624, with crustacea only enriched (+)-enantiomers. EFs of o,p’-DDD were0.358-0.564, with90%less than0.5. All of the EFs of o,p’-DDT were less than0.5, resulting in enrichment of (-)-enantiomers. Moreover, there was no correlation between values of EFs and concentrations of racemic compounds in fish.(3)Trophic magnification factors (TMFs) were>1for all the OCPs expect TC, but only o,p’-DDE and o,p’-DDD showed statistically significant biomagnification. Imbalance of biological substance distribution, ability of biological metabolism, individual size may affect the biomagnification. Moreover, significant positive correlation were found between the concentration of OCPs and the lipid content of aquatic organisms, indicating that lipid content was one of the main controls of accumulation for OCPs in organisms from Zhoushan Fishing Ground.(4)The concentrations of DDTs, HCHs, and CLDs in muscles of the dog sharks were7.27-26.62,2.67-3.35, and0.54-0.61ng/g ww, respectively. In the five tissues, the concentrations of total OCPs followed as livers> muscles> gills> skins> fins. HCHs were most abundant in gills, while DDTs and CLDs mostly redistributed and accumulated in livers. The residue levels of HCHs with low Kow, depend on, to a great extent, by exchange with the surrounding environment across the gills. Unlike HCHs, the maternal compounds were predominant DDT congeners in livers, muscles, and skins, but for gills and fins, the metabolites, including DDDs and DDEs contrarily occupied the major proportion. This phenomenon supported the suspicion that DDTs in gills may come mainly from the redistribution rather than a direct penetration through the gills. Because of high lipid content in liver and high affinity to the phase-1biotransformation enzyme cytochrome P4501A (CYP1A) as well, DDTs and CLDs with higher lipophilicities actively accumulated in liver. cis-chlordane was the predominant isomer of CLDs in either tissue of the sharks, and the percentages of cis-chlordane in liver were higher than those in other tissues, indicating faster metabolism and/or excretion of trans-chlordane.(5)The health risk assessments performed based on several available guidelines suggested that although no significant human health risks were associated with the dietary intake of OCPs,26.7%of DDTs residues exceeded the maximum residual limits of China. Moreover, an increased lifetime cancer risk from dietary exposure to51.5%of DDTs and63.4%of HCHs remains a possibility.