The Correlation Study Between PCBs And ?¹⁵N Values Or FAs In Fish Collected From Dongting Lake

Polychlorinated biphenyls(PCBs)belong to Persistent Organic pollutants(POPs),which can pose a threat to environment and human health even at low concentrations.And it were among the first banned under the Stockholm Convention on POPs.The toxicity of polychlorinated biphenyls(PCBs)and their transformation have been intensively investigated in recent years.However,the potential mechanisms of biotransformation in a lake food web remain unclear.Dongting Lake,the second largest freshwater lake in China,and it is also the main production base of commercial freshwater fish in China.Fish also is an important part of the food of local residents.The predominantly commercial fish species are Ctenopharyngodon idellus,Cyprinus carpio,Hypophthalmichthys molitrix,Aristichthys nobilis,Elopichthys bambusa,Silurus asotus and so on.And these fish species are the important part of daily diet.In this study,six fish species were collected in Dongting Lake,including Ctenopharyngodon idellus,Cyprinus carpio,Hypophthalmichthys molitrix,Aristichthys nobilis,Elopichthys bambusa and Silurus asotus,and tissues,such as skin,eye,muscle,gill,liver,swim bladder,intestine,kidney,fat,blood,gonad,intestinal content and stomach were dissected.PCBs,?15N values and fatty acids(FAs)of the different fish tissues were determined with the stable isotope analysis technics and gas chromatography-mass spectrometry analysis,respectively.And the correlation analysis between PCBs and ?15N values or FAs was conducted.The results can provide scientific basis to ecosystem of Dongting Lake and human health with low concentration of PCBs.The results indicated that 115 PCB congeners were detected,based on three measurement forms,the concentration of ?PCBs115 ranged from 0.04 to 9.77ng/g wet weight(ww),0.33 to 47.4 ng/g dry weight(dw),4.29 to 326 ng/g lipid weight(lw),respectively,the highest level was found in gonad tissues of Cyprinus carpio.The highest toxicity equivalent(TEQ)values were found in different fish tissues based on three measurement forms,which ranged from 0.0003-2.39 pg/g ww,the highest level was found in Elopichthys bambusa fat,0.0016-4.64 pg/g dw,the highest level was found in Hypophthalmichthys molitrix eye,and 0.017-19.89 pg/g lw,the highest level was found in Silurus asotus fat.The PCBs levels in fish collected from Dongting Lake were at the low end of the global range compared with other studies.PCB28,52,95,99,101,105 110,118,138,153,155 and 209 were found in all tissues.Co-PCBs,Ind-PCBs and PCB209 had a different distribution in tissues of the collected fish species.And the changes in the gonad of Cyprinus carpio were dramatically.The low chlorinated PCBs,which were tri-to penta-PCBs,had the highest percentage in all tissues.Based on the lw,PCB138 and 153 have correlations with TEQ in liver,gill,intestine and skin,respectively.The order of the ?15N values in five fish tissues(liver,muscle,gill,skin and intestine)was consistent with the living habit in the food web,which was Ctenopharyngodon idellus,Cyprinus carpio,Hypophthalmichthys molitrix,Aristichthys nobilis,Elopichthys bambusa and Silurus asotus.The correlation between PCBs and the ?15N values indicated that due to the difference of metabolism and lipid content in different tissues,based on the three forms of measurement,the correlation between PCBs and ?15N values in tissues was different.Based on the ww,in liver,PCB52 has a positive correlation with the ?15N values;Based on the lw,in liver,PCB153,?hexa-PCBs and ?TEQ have positive correlation with the ?15N values,respectively.In skin,PCB138 and 153 have correlations with the ?15N values.And other PCBs have correlations with the ?15N values in other tissues.The correlation between PCBs and FAs values indicated that PCB155 has a positive correlation with docosahexaenoic acid/eicosapentaenoic acid(DHA/EPA)in intestine.Polyunsaturated fatty acid/saturated fatty acid(PUFA/SFA)and DHA/EPA might be indicators for the transfer of PCB congeners.In liver,muscle,gill and intestine,other PCBs congeners also have correlations with other fatty acids.The risk assessment results indicated that there was an acceptable risk of cancer for the people who consumed the fish from Dongting Lake.