Characterization Of Tuna Pollution Accumulation Based On The Organic Pollutant Composition In Tuna Stomach And Their Contents

As an oceanic migratory fish,tuna has a range of activities in tropical,subtropical and temperate seas.It mainly feeds on pelagic fish,cephalopods,crustaceans,etc.,and can consume up to 14% of their body weight daily.At the same time,tuna is the top predator in the ocean,at the top of the ocean food chain,with a high trophic level.During its growth and development,it accumulates large amounts of organic pollutants,including persistent organic pollutants(POPs)and pesticides.Moreover,due to the persistence,bioaccumulation,long-range transport and toxicity of organic pollutants,they are easily enriched in organisms and transmitted layer by layer through the food chain,eventually accumulating in organisms at higher trophic levels.Finally,this will affect its normal metabolism.At present,the research areas of organic pollution of tuna are mostly concentrated in coastal and Mediterranean areas,and the research objects are mostly bluefin tuna,and the research content is mainly the characteristics of pollution endowment content.Therefore,exploring the relationship between gastric contents,trophic level and bioconcentration of organic pollutants based on the gastric contents and trophic level of tuna is helpful to further explore the sources and occurrence of organic pollutants in tuna,and improve the diet,trophic level and bioconcentration mechanism of tuna.As a biological sample with a complex matrix,tuna is difficult to extract and detect organic pollutants in its body.At present,the extraction technology of organic pollutants in organisms mostly adopts traditional microwave assisted extraction(MAE),liquid-liquid extraction(LLE),Soxhlet Extractor Method,etc.Purification technology mostly uses Solid Phase Extraction(SPE)and Gel Permeation Chromatograph(GPC).The above extraction and purification methods have the disadvantages of large consumption,pollution,and time-consuming,which cannot meet the rapid and efficient processing of biological samples.Therefore,the use of QuEChERS method(fast,simple,cheap,efficient,durable,safe)to pre-treat animal and plant samples can adsorb impurities in the sample and extract the required targets,The method is simple to operate and low cost.In this study,the basic QuEChERS technology was optimized to obtain a rapid sample preparation technology suitable for marine biological samples such as tuna,and applied to the detection and analysis of trace pollutants such as organic pollutants.In this study,the stomach and gastric contents of tuna caught in the Atlantic,Indian and Pacific Oceans were studied as the research objects,and the characteristics of organic pollutants in the stomach and its gastric contents of tuna in various sea areas were analyzed by using the established QuEChERS rapid sample preparation technology.Through traditional gastric content analysis and stable isotope technology,food source identification and nutrition level calculation were used to determine the food source information,nutritional level and pollution concentration level of tuna in the sampling area,and then the influence of tuna gastric content and nutritional level on the occurrence of POPs was inferred.QuEChERS rapid sample preparation technology combined with LC-MS/MS and GC-MS/MS instrumental detection methods can be used to detect a variety of organic pollutant residues in marine organisms.15 m L of 1% acetonitrile acetate solution was selected as the extraction solvent,anhydrous magnesium sulfate as the main salting pretreatment agent and EMR-Lipid as the adsorption material for pretreatment of the biological matrix,and a good recovery rate of 88%-116% was obtained.After the pretreatment method was verified,the detection limit LOD and the limit of quantification LOQ ranged from 0.08 to 2.47 μg·kg-1 dw and 0.27-8.24μg·kg-1 dw,respectively,and the detection limit MDL range was 0.12-3.06 μg·kg-1dw.The results show that the optimized pretreatment method has good recovery,precision and accuracy,and can be applied to tuna stomach and gastric contents samples.The results showed that six groups of organic pollutants were distributed in tuna samples in the Pacific,Indian and Atlantic Oceans,with OCPs concentrations of 0.34-44.54 ng/g dw,PCBs concentrations of 0.10-18.20 ng/g dw,PAHs concentrations of5.71-100.86 μg/g dw,OPPs concentrations of 2.84-286.81 ng/g dw,and pyrs concentrations of nd-661 ng/g dw.NEOs concentration is nd-6.70 ng/g dw.Pollution concentrations in the three oceanic tuna samples analysed were at low levels compared to pollution levels in coastal and Mediterranean tuna.In general,DDTs was the main component of OCPs in tuna stomach,accounting for 61-96% of the total concentration of OCPs.PCBs use hexa-chlorobiphenyls as the main homologer;The content of low-loop PAHs was higher than that of high-loop PAHs.OPPs were mainly detected with triazophos;The highest detection rate of PYRs was cypermethrin;NEOs detected only thiamproline and acetamiprid.The results of tuna gastric contents analysis showed that the dominant gastric contents of tuna in different seas were different.The round rudder bonito and the iris squid are the dominant species in the Pacific Ocean,while the Indian Ocean prefers the rudder bonito and the squid.The stable isotope results of carbon and nitrogen showed that the food sources of tuna were consistent in different sea areas,and the nitrogen isotopes of tuna in the Indian Ocean were higher than those in the Pacific Ocean.Calculation of trophic level TL and trophic level biomagnification factor TMF(TMF>1 means biomagnification)showed that both biomagnification and biodilution effects of pollutants in the tuna food chain.OCPs and PCBs were biomagnified in tuna.