Pollution Evaluation And Bioavailability Of Heavy Metals And Polycyclic Aromatic Hydrocarbons In Pond Aquaculture Products In The Yangtze River Delta

The Yangtze River Delta(YRD),where "One Belt and One Road" strategy and Yangtze River economic band merges,is the most development region with the densest population with highest consuming intentions.The Yangtze River Delta is also the most important freshwater aquaculture region,contributing to 19% of the total aquaculture production nationwide.Along with the economic development and increasing life quality of the residents,the demand of high quality protein of people increased significantly.Recently,the demand of aquaculture products has increasing dramatically,as the protein content of aquaculture products is higher than other food.Due to the increasing attention from public for aquaculture products,it is,therefore,of of practical significance to study and ensure the quality of aquaculture products.Polycyclic aromatic hydrocarbons(PAHs)and heavy metals are toxic,bioaccumulative,and persistent in the global environment.They are important ecological environmental issues that may affect ecosystem and human health.They have drawn more and more attention and become the focus of environmental science,due their hydrophobicity and bioaccumulative through food chain.PAHs and heavy metal also can be adsorbed onto suspended particulate matters and deposited onto sediment,causing problems for benthos in sediments.Therefore,aquaculture products,sediments and water collected from Yangtze River Delta region,including Shandong,Jiangsu,Anhui,Zhejiang,Shanghai and Fujian,were studied.The residues,sources,distribution of PAHs and heavy metal in aquaculture were determined,and furthermore,the food safety and bioavailability of PAHs were evaluated.The major findings of this research are shown as follows:(1)The residual levels of heavy metal in aquaculture products collected from farm pond in YRD region were determined.Specifically,As and Cr in all the aquatic products were below the national guidelines,Cu and Pb in half of the samples exceeded the limits,and Cd was observed to be the predominant heavy metal,and exhibited the highest contamination levels.This study also found that concentrations of heavy metal in benthos were higher than in fish.The correlation of levels in aquatic species and sediments were investigated as well,and the results showed that the residues of Cr and Cd in aquatic species significantly correlated to that in sediments.Risk assessment by consuming these products were evaluated using different approaches.By intake safety evaluation approach,AWI/PTWI(adults)ratios of Cu,Pb,Cr and As were less than 100%,while the proportion of Cd was significantly higher than 100%,indicating that safety risk posed by Cd is higher than others.In the meantime,risk assessment suggested that part of the selected products may causing health risk or hazard for human being.Cu and Cd contributed more to the overall risk by dietary intake of these aquaculture products.In addition,the overall risk posed by benthos was higher than the risk caused by fish.(2)The concentrations of PAHs in aquatic species were measured as well.The residual levels of ∑PAHs ranged from 42 to 597ng/g dw,and the highest and lowest levels were all observed in fish.The majority of the PAHs congeners were observed,except NAP,DBA,and BPF.In addition,ANY and IPY were observed with low detection frequency.Comparing to the residues of PAHs in aquatic species collected from other region or country,the residual levels in the present study is not high,and the predominant congeners were 3-4 rings.Finally,risk assessment posed by PAHs in aquaculture products was conducted,and incremental lifetime cancer risk(ILCR)values were determined according to the guidelines published by EPA.The results indicated that PAHs in aquaculture products collected from YRD region were safe in general,except some cases which were also under control.BSAF and BCF values were determined as well in the study,indicating low bioavailability,non-persistency and low bioaccumulation potentials.(3)Source of PAHs in the selected aquaculture products were analyzed,indicating the PAHs in aquatic species were probably from sediments of the culture ponds.Meanwhile,the results of passive sampling method suggested that the residues of PAHs in the studied species were equilibrium to the concentration in the dissolved phase.Mass exchange between aquaculture products and sediments were not equilibrium due to short retention time of these animals in the ponds.The results also indicated that more PAHs in benthos were from sediments rather than fishes.