Characteristics Of Arsenic And Mercury Contents In Typical Fishpond Ecosystems In Chengdu And Health Risk Assessment

In the ecosystem of fish pond,Arsenic(As)and Mercury(Hg)are increasingly polluting the environment,and the safety of aquatic products has always been focused by people.In order to reveal the factors which affects the fish body to be with heavy metals in the fish pond ecosystems,this thesis toke the water,sediment,feed and fish in the fish pond of Chengdu area as the research object.By investigating the content characteristics of As and Hg in the sample,the pollution characteristics of water and sediment As and Hg were evaluated.At the same time,the enrichment characteristics of As and Hg between different fish species and their correlation with the environment in the fish pond ecosystem were discussed,and under dietary exposure conditions,the health risks caused by fish body with As and Hg were evaluated.The main conclusions are as follows:(1)The contents of As and Hg in the waters of 10 typical fish pond ecosystem in Chengdu were in the values specified of the Fishery Water Quality Standard(GB11607-1989).The average value of As in the 4th ring road area around the city is lower than that in the 6th ring road area and the Hg content in the 4th ring road area around the city is higher than that in the 6th ring road area.That is there is no significant difference between As and Hg in the two areas(P > 0.05).The As content of all sampling points showed the characteristics of spring more than autumn,while the Hg content showed the characteristics of spring less than autumn.Using the single factor index form to evaluate the As and Hg of the water,it was not polluted and the pollution risk of fish pond water was small.(2)In the 10 typical fish ponds of Chengdu,the content of As ranged from 0.77 to 7.71mg/kg,with an average of 4.08 mg/kg,and the content of Hg ranged from 30.83 to 160.77 ng/g,with an average of 93.29 ng/g.The average content of As and Hg in the 4th ring road area around the city is higher than that in the 6th ring road area around the city.The average content of As in the 10 typical fishpond ecosystems in Chengdu showed the characteristics of spring greater than autumn,and the average content of Hg showed the characteristics of spring smaller than autumn,which means As and Hg showed significant differences between the two regions(P < 0.01).By the methods of ground accumulation index and potential ecological hazard index for evaluating the As and Hg in sediments,the results showed that As in sediments was not polluted and the ecological hazards caused by As were slight while Hg was non-slight pollution and the ecological hazards caused by Hg were slight-strong.The content of As and Hg in feed at all sampling sites did not exceed the Safety Limit of Fishery Formula Feed(NY 5072-2002).(3)The contents of As and Hg in muscle of grass carp,crucian carp and common carp in typical fish pond ecosystem of Chengdu did not exceed the Sanitary Standard for the Limitation of Arsenic in Food(GB4810-1994).The contents of As in grass carp,crucian carp and common carp were 0.047-0.199 mg/kg,0.122-0.393 mg/kg,and 0.224-0.449 mg/kg,while the contents of Hg were 16.04-37.61 ng/g,50.01-162.22 ng/g and 40.88-117.37 ng/g.The content of As showed the regularity of grass carp < crucian carp < common carp,and the content of Hg showed the regularity of grass carp < common carp < crucian carp.Meanwhile,the content of As and Hg of fish in the upper layer was less than that in the middle and lower layer,and the content of As and Hg of the herbivorous fish was lower than the omnivorous fish.The average content of As and Hg in the 4th ring road area around the city is higher than that in the 6th ring road area.In general,the risk of As and Hg from eating grass carp,crucian carp and common carp in fish ponds of Chengdu can be neglected.(4)The content of As in crucian carp and common carp was positively correlated with the content of As in water samples(P < 0.01).And the content of As in water samples was positively correlated with total nitrogen and permanganate index(P < 0.01),as well as positively correlated with total phosphorus index(P < 0.05).Similarly,the content of Hg in crucian carp and common carp was positively correlated with total phosphorus and permanganate index(P < 0.05),and the content of Hg in sediment was significantly correlated with organic matter(P < 0.05).