Study On Bioaccumulation,Elimination And Toxic Effects Of Typical Organochlorine Pesticides On Tubifex Tubifex And Carp

Most organochlorine pesticides(OCPs)are persistent organic pollutants(POPs)with high hydrophobicity,accumulation potential,persistence and potential long-range transport.Although most OCPs have been banned for several decades,they can be generally detected in various environmental media,such as food web,sediment,water and air.Besides,some OCPs are chiral pesticides,and their enantiomers have different environmental behaviours in the environment,especially in the organisms.The enantiomers generally have different toxicity,bioactivity,accumulation and metabolism behaviours,sometimes even showed the opposite physiological effects.Hence,the study on the environmental behaviours and toxic effects of OCPs help to better understand the fate of OCPs in the environment,and provide more information about the potential ecological risks.Thus,benthic organism Tubifex Tubifex was chosen,which response to two aspects of water quality and bottom sediment pollutions is very sensitive,can synthetically reflect the pollution situation of water and sediment and pollutant toxicity.T.tubifex is an important part of the food chain,which can be preyed by many fish,such as carp.Carp can be preyed by larger fish or other top-predators,which help to assess biomagnification and environment risks.Based on these organisms,four hexachlorocyclohexane(HCH)isomers,dichlorodiphenyltrichloroethane(DDT)and its metabolite dichlorodiphenyldichloroethane(DDD)and dichlorodiphenyldichloroethylene(DDE)were studied,a-HCH,o,p'-DDT and o,p'-DDD are chiral pesticides.We carried out the following research about HCH isomers.1.Toxicokinetics and oxidative stress in Tubifex tubifex exposed to HCH isomers.Rapid accumulation and elimination processes were observed in T.tubifex,while no enantioselective accumulation or elimination were found for a-HCH enantiomers in T.tubifex.The responses of biochemical biomarkers demonstrated the toxic impacts of HCH isomers,and the malondialdehyde(MDA)levels increased,which would cause oxidative stress and affect the health of T.tubifex.2.Selective bioaccumulation and elimination of sediment associated HCH isomers in Tubifex tubifex.The bioaccumulation curves of HCHs were approximate to M-type in T.tubifex,which might be relate to the autotomy and regeneration of their caudal part.The existence of T.tubifex can accelerate the dissipation of HCHs in sediment,which is important for the elimination of HCHs in sediment.Simultaneously,the enantioselective accumulation of a-HCH enantiomers were observed in T.tubifex.3.Effects of benthic organism Tubifex tubifex on HCH isomers transfer and distribution into freshwater sediment.The existence of T.tubifex significantly reduced ?-HCH fluxes from the overlying water to sediment.4.Selective bioaccumulation,biomagnification and depuration of HCH isomers in a freshwater food chain(T.tubifex-carp).The bioaccumulation curves of HCH isomers in carp were similar to those in T.tubifex,while the bioaccumulation abilities of HCHs in T.tubifex were higher than those in carp.The presence of contaminated worms as a dietary source in the food chain led to significantly higher bioaccumulation in carp.The biomagnification factor(BMF)values for HCH isomers were all greater than 1.It should be noted that the concentrations of HCHs in feces were high,and the feces may exist a potential risk for the feces feeders,leading to the re-exposure of HCHs to the food chain.T.tubifex and carp rapidly eliminated HCHs in the elimination experiments,and the half-lives were shorter than 2.5 days.The enantioselective bioaceumulation and elimination of a-HCH enantiomers in T.tubifex led to the enantioselectivity of ?-HCH enantiomers in carp,which may lead to the changes of the toxic effects of contaminants.We carried out the following research about DDT.1.Bioaccumulation of DDT in carp and Tubifex tubifex in a water/sediment microcosm:important role of sediment particulate matter and bioturbation.The different exposure routes affect the bioaccumulation and elimination of DDT and its metabolites(DDD and DDE)in carp.Simultaneously,the enantioselective bioaccumulation and elimination of o,p'-DDT and o,p-DDD were observed in T.tubifex and carp.2.Assessment of tissue-specific accumulation,elimination and toxic effects of DDTs in carp through aquatic food web.The changes of DDT and its metabolites(DDD and DDE)concentrations differed in the tissues/organs of carp.The responses of biochemical biomarkers demonstrated the toxic impacts of DDTs.The gill and kidney of carp were the main target organs.