Study On Correlations Of Fatty Acids,organochlorine Pesticides And?¹⁵N Values In Fish Tissues From Dongting Lake

Fatty acids?FAs?have special biological activity which is an important indicator to reflect the nutritional value of aquatic products.In addition,the source of food and the flow of substances within the ecosystem in the organism can be traced by fatty acids biomarker.Organochlorine pesticides?OCPs?,a typical persistent organic pollutant,have strong lipophilicity,persistence,bioaccumulation and toxicity.Even if existing in the environment at a trace level,it will have a potential negative impact on the ecological environment and human health.At present,there have been many reports on the application of FAs in marine food web research and on the biomagnification behavior of OCPs,but the research on the correlation between FAs and OCPs in organism is relatively lacking.The fish consumed by Chinese residents are mainly freshwater fish.Dongting Lake,the second largest freshwater lake in China,is the major producing regions of commercial freshwater fish in China.Thus,in this paper,six fish species were collected from Dongting Lake,including Ctenopharyngodon idellus,Hypophthalmichthys molitrix,Cyprinus carpio,Aristichthys nobilis,Elopichthys bambusa and Silurus asotus,and were dissected to more than ten kinds of tissues,such as muscle,liver,gill,skin,intestine,etc.The FAs,OCPs and stable nitrogen isotope ratios(?¹⁵N values)in fish tissues were determined by gas chromatography-mass spectrometry,high resolution gas chromatography-high resolution mass spectrometry and isotope ratio mass spectrometry,respectively.The distributions of FAs and OCPs in fish tissues and the correlations of FAs,OCPs and?¹⁵N values were studied.It is desirable that the study in this paper could help to provide advice and reference for people to consume fish from Dongting Lake,and also provide data support for research on material flow in freshwater ecosystems and further understanding of the biomagnification behavior of OCPs.The results of the distributions of FAs in fish tissues from Dongting Lake indicated that the saturated fatty acids?SFAs?were mainly composed of palmitic acid and stearic acid;the monounsaturated fatty acids?MUFAs?were mainly composed of palmitoleic acid and oleic acid;the polyunsaturated fatty acid?PUFAs?were mainly composed of linoleic acid and?-linoleic acid?GLA?.The content of?SFAs,?MUFAs and?PUFAs in the muscle tissues varied from 32.31⁵1.33%,23.36⁵1.32%and 1.92²5.32%,respectively.The contents of?SFAs and?PUFAs were higher in A.nobilis,and the content of?MUFAs was higher in C.idellus.The distribution of?PUFAs was tissues-specific and species-specific,while the distributions of?SFAs and?MUFAs were not this phenomenon.The contents of?PUFAs were higher in the muscle tissues of H.molitrix,A.nobilis and E.bambusa,while lower in the liver tissues of H.molitrix and A.nobilis.In terms of nutritional value,the fish muscles from Dongting Lake would effectively supplement the n3-PUFAs required by human.And the nutritional value of FAs in the muscles of H.molitrix and A.nobilis was higher.The results of the distributions of OCPs in fish tissues from Dongting Lake showed that the detection rates of hexachlorocyclohexanes?HCHs?and dichlorodiphenyltrichloroethnes?DDTs?were 100%,the concentration of?DDTs was greater than?HCHs,but were all below the maximum limit value of aquatic products set by Chinese rule.The concentration of?HCHs and?DDTs in fish muscles ranged from 0.04 to 2.02 ng/g?ww?and 0.60 to 16.0 ng/g?ww?,respectively.Compared with freshwater fish from other regions,the concentration of?HCHs in fish muscles of this study was at a moderate pollution level,while the concentration of?DDTs was at an above the intermediate pollution level.The distributions of?DDTs and?HCHs in fish tissues were tissues-specific.The higher concentrations of?HCHs and?DDTs were found in the fat tissue,followed by the liver.The composition of HCHs was tissues-specific and species-specific,while the composition of DDTs was not.In terms of health risk assessment,the OCPs in the muscles of fish from Dongting Lake would not bring potential non-carcinogenic health risks to humans,and the OCPs in the muscles of C.idellus and A.nobilis would not bring potential carcinogenic health risks to humans.The results of correlation analysis of FAs,OCPs and?¹⁵N values in the liver,muscle,gill,skin and intestine of fish from Dongting Lake showed that there was a trend that the ratio of docosahexaenoic acid to eicosapentaenoic acid?DHA/EPA?was increased with the increase of?¹⁵N values in fish tissues.The proportions of pentadecanoic acid and heptadecanoic acid were significantly positively correlated with?¹⁵N values in the muscle,gill and skin tissues.The concentration of DDTs was positively correlated with the?¹⁵N value in the intestine,while the concentration of HCHs was not.And there was a trend that the ratios of?-HCH to?HCHs and p,p'-DDE to?DDTs increased with the increase of?¹⁵N value in the intestine.There was a difference in the correlation between the concentrations of FAs and OCPs in different fish tissues.And the concentrations of many kinds of FAs showed significant positive correlations with the concentrations of many kinds of OCPs in fish tissues based on the wet weight and dry weight measurement,while the same results were not found based on lipid weight measurement.In the muscle,the concentrations of many kinds of SFAs and MUFAs were significantly positively correlated with the concentrations of many kinds of OCPs and the concentrations of linoleic acid,GLA and cis-11,14,17-eicosatrienoic acid were significantly positively correlated with the concentrations of?-HCH,p,p'-DDD and o,p'-DDT based on the wet weight and dry weight measurement;while only the concentrations of a few kinds of SFAs and MUFAs were positively correlated with the concentration of?-HCH based on the lipid weight measurement.There were significant positive correlations between the concentrations of PUFAs and the concentrations of OCPs in the muscle,which indicated that people should pay attention to co-intake of OCPs when they supplement the PUFAs needed by the human body through fish.