| In order to understand the characteristics of the heavy metal concentration of aquatic organisms in Wanfeng Lake,we went to Xingyi,Guizhou in September 2020 to collect aquatic biological samples.According to the special karst landform environment and river-type water environment points of Wanfeng Lake,a total of 18 sampling points were selected from the upper,middle,and lower reaches and under the outer dam of the reservoir area to conduct water samples,sediments,aquatic plants,and plankton samples.The paper discussed and studied the characteristics of the water environment of Wanfeng Lake,the concentration of 8 heavy metals(As,Cd,Cr,Hg,Pb,Cu,Mn,Zn)in the aquatic organisms,as well as the current status of conventional physical and chemical factors and the structure of plankton communities in Wanfeng Lake.Correlation analysis of heavy metal content in fish with environmental factors and growth parameters was conducted.The analysis the enrichment and migration law of heavy metals in Wanfeng Lake environment-aquatic organisms.In addition,the Nemeiro comprehensive pollution index method was used to analyze the heavy metals in Wanfeng Lake water.Pollution status,using the health risk assessment model recommended by the US Environmental Protection Agency(USEPA)to analyze the risk of human health of heavy metals on behalf of fish in Wanfeng Lake.The main results obtained in the paper are as follows:(1)The physical and chemical water quality indexes of the 18 sampling points of Wanfeng Lake are all within the standard range,and the water quality can reach Class I water.The content of heavy metals in water is as follows: Cr > Zn > As > Cu > Hg >Mn > Pb > Cd.Except for the heavy metal Hg,the content of other heavy metals is in compliance with the level II and III limits of the surface water environmental quality standards and the drinking water standards.The single factor index of the eight heavy metals is the highest in Hg pollution index,which is a strong pollution.The other heavy metals are at a safe level and are pollution-free.The middle and upper reaches of Wanfeng Lake are at the pollution-free level of heavy metals.The lower reaches of S13(Zhemo),is low pollution,and S11(Baai Village)and S17(Large)The dam is moderately polluted,and S16(Hongchun Village)and outside the reservoir area are heavily polluted.The total health risk values of the 18 samples all exceeded the maximum acceptable risk level stipulated by ICRP.Among them,the carcinogenic pollution factor Cr contributed the most,indicating that the Wanfeng Lake water body has the health risk of Cr heavy metals.Therefore,most of the water quality indicators of Wanfeng Lake are within the standard range,and the water quality can reach Class I water.Only S11(Baai Village),S16(Hongchun Village),S17(dam),S18(under the dam)samples The point Hg content exceeds the limits for water of Class II and III,and only reaches the overall water of Class IV.(2)A total of 151 species of phytoplankton in 7 phyla were identified,and the main species composition was Chlorophyta.There are 71 species of zooplankton in 4phyla,mainly rotifers.The composition,density,and biomass of plankton species were significantly higher in the upper and middle layers than in the lower layer.The spatial distribution of density and biomass was higher than that in the upper and middle and lower layers.The spatial distribution of phytoplankton and animal species did not show a consistent trend.The phytoplankton diversity index is between 1.24 and 3.54,and the zooplankton diversity index is between 0.82 and 2.24.It can be preliminarily judged that the water quality of the Wanfeng Lake basin belongs to the clean and oligotrophicmedium-pollution medium-nutrient type.The content of heavy metals in plankton is low,and the enrichment level is low.(3)By comparing the differences in the content of heavy metals in different fish tissues,it is found that the content and distribution of heavy metals in different fish tissues in Wanfeng Lake are quite different.The As content in the muscles of silver carp,crucian carp,bighead carp,tilapia,sclerophyllum,longsnout and clarias catfish exceeds the national limit of 0.1 mg/kg,and the Cd in the muscles of bighead carp and carp exceeds the national limit of 0.1 mg/kg,and the rest The types of heavy metals are not exceeded.The analysis showed that the content of Zn and Hg in fish muscles showed a significant negative correlation with body weight,and Zn showed a significant negative correlation with body length,indicating that Wanfeng Lake fishes have significant biological effects on the enrichment of heavy metal elements Zn and Hg.There are differences in the accumulation and enrichment of different heavy metal elements in fish with different feeding habits.Zn,Mn,Hg and Pb may have biomagnification in the process of food chain transmission,while heavy metal elements such as Cu,Cr,As and Cd vary with fish nutrition.The trend of increasing and decreasing the level.The heavy metals Zn,Mn,Cu,Cr,and Pb in the fish muscles of Wanfeng Lake did not show a consistent change trend between different habitat water layers.The heavy metals As,Cd,and Hg showed that the upper fish were significantly higher than the middle and lower fish.By comparing the contents of 8 heavy metals in grass carp,common carp,tilapia,and calamari in 2018 and 2020,the content of Cr in the four fishes in 2020 is higher than that in 2018,and the levels of Hg,Pb,Cu,and Mn are all lower.In 2018.Research on the health risks of 9 economic fish species in Wanfeng Lake found that adults’ THQ is significantly higher than children’s,and they are more sensitive to heavy metals than children,and are more susceptible to heavy metals.As has the highest contribution rate to TTHQ and is the most important risk element.,The health risk prevention and control of As in fish food products should be strengthened.The TTHQ of Wanfeng Lake fish treated crucian carp and Aphid cichlid was greater than 1,and the other common fishes were all less than 1.Therefore,the consumption of crucian carp and Alice-billed crucian carp poses a health risk for local residents to accumulate heavy metals.(4)By comparing the correlation coefficients of heavy metal content among water bodies,sediments,plankton and aquatic plants,it is found that the content of heavy metals in plankton mainly depends on sediments,and is also affected by water bodies and aquatic plants.By comparing the correlation coefficients of heavy metal content among water bodies,sediments,plankton,aquatic plants,and four different feeding fishes,it is found that Zn and Pb may migrate to fish through food pathways,and are also affected by water bodies and sediments.Hg,Cd and Mn migrate from the environment to fish.From the above results,most of the water quality of Wanfeng Lake can reach Class I water,some of the samples have Hg pollution,and only reach Class IV water.There is a risk of carcinogenic Cr in the water.The As and Cd in the muscles of some fish exceed the limit values of heavy metals in aquatic products in the national standard NY5073-2006,while the rest of the heavy metals do not exceed.The adult risk of fish exposure to heavy metals is significantly higher than that of children.As is the most important element of risk,and crucian carp and calamari have food risk.The ability of fish to accumulate heavy metals is higher than that of aquatic plants and plankton.Among them,filter-feeding fish,omnivorous fish and herbivorous fish are more capable of accumulating heavy metals than carnivorous fish.The heavy metals Zn and Pb in Wanfeng Lake may Migrate to fish through food,Hg,Cd,Mn migrate to fish from the environment.Therefore,it is necessary to strengthen the monitoring of Cr and Hg in water and As in fish. |
