| Guizhou Caohai is a national nature reserve,but due to long-term exposure to the surrounding soil zinc smelting and domestic sewage,it has been seriously threatened by ecological risks.Previous studies have also done a lot of research.This article aims to determine The bioavailability of heavy metals in the Caohai ecosystem was studied using various heavy metal contents in Caohai sediments,heavy metal content in aquatic animals,heavy metal content in feathers of Caohai birds,and indoor simulated experiments and in vitro digestion experiments.The results show:(1)The Zn content in surface sediments of the Caohai Sea ranged from 91.93 to 1199.91 ug/g(average 365.81 ug/g),and the Pb content ranged from 27.98 to 235.40 ug/g(average 100.62 ug/g).The range is 0.48-68.98ug/g(mean 21.55 ug/g).The three elements are much higher than the background values of soil elements in China.Among them,Zn has a background value of(74.2±32.78 ug/g)5-6 times.The value is(26±12.37 ug/g)4 to 5 times,and the Cd backgroundvalue(0.097±0.079 ug/g)is about 200 times.Affected by organic matter and ferromanganese oxides in the sediments of the Caohaihai Lake,all three elements showed that the content of the lakeside was lower than that of the lake.(2)The content of heavy metals in different types of benthic animals varies greatly.The zinc content of all benthic animals in the Caohai wetland ranges from 5.959 to 76.942 μg/g(mean value is 35.278 μg/g),and the lead content ranges from 0.007 to 0.190 μg/g.(Mean value:0.043ug/g),cadmium content ranged from 0.026 to 1.225ug/g(mean value 0.250ug/g).According to China’s fresh and frozen animal aquatic product hygiene standards(GB2733-2015),all three metal elements were excessive.phenomenon.In addition,the heavy metal contents in benthic macroalgae in different seagrasses are quite different.The order of Zn content from high to low is wolfberry> snail> goby> seabream> squid> shrimp> grass carp.The distribution of Pb content in benthic animals As snail> cockroach> shrimp> goby> cod fish> grass-fish> cod,the distribution law of Cd content is snail> cockroach> wheat-ear fish> goby-fish = grass carp> shrimp> cod.(3)There are some differences in the distribution of heavy metals in various forms of sediments in the Caohai Sea.Among them,Zn is mainly distributed in the residue state and in the iron-manganese oxidation binding state.Its distribution pattern in each form is residue state>Fe-Mn oxidation binding state> Fuli acid> humic acid> exchangeable> carbonate bound,and the distribution of Zn in the lake and the lake is very different;the distribution of lead in all forms is iron and manganese oxidized bound state> residual state> humin State>Fuliic acid>Exchangeable>Carbonate binding,still exists in the horizontal distribution difference,the exchangeable lead in lake core point is lower than the lakeside point,but the fulvic acid lead is obviously higher than the lakeside point The Cd elements in the Caohai sediments are mainly distributed in the iron-manganese oxidation state,the exchangeable state and the carbonate bound state.The distribution rule is iron and manganese oxidation state> exchangeable state> carbonate binding state> fulvic acid state.The humin state> residue state,there are also differences in the content of the lake point and lake core points.Correlation analysis found significant correlations between total heavy metals and iron-manganese oxide bound,residual,fulvic acid,and humic acid states,with exchangeable zinc,exchangeable lead,carbonate bound zinc,and carbon.There is no significant positive correlation between acid-bound cadmium.The total Zn content is closely related to its iron-manganese oxide bound state,fulvic acid state and humic acid state.The total amount of Pb and Cd elements is extremely related to its iron-manganese oxide bound state,fulvic acid state and residue state.From the results of several risk assessments of various forms of heavy metals in the Caohai Sea,the Zn and Pb elements in the Caohai sediments are at a moderately light pollution level,while the Cd elements are at a severely polluted level.(4)The response relationship between the heavy metal content in benthic macrobenthos andthe heavy metal contents of various forms of grass sea sediments showed that the iron and manganese zinc and hummin zinc had a greater effect on the zinc content of benthic animals and the carbon in the sediments of the Caohai Sea.The acid-bound lead has a great influence on the lead content in the snail,and the iron-manganese oxidized cadmium in the sediment has a great influence on the cadmium content in the snail.(5)The contents of heavy metals in the digestive fluids of the three elements in the Caohai sediments were consistent with that in the snails.Among them,the zinc content was higher in the lake core than in the lake,while the lead and cadmium elements were affected by the environmental pH.The influence is expressed as the lake point is lower than the lake point.(6)The content of Zn in feathers of seagrass was in the range of 118.73μg/g to 681.02μg/g(mean 177.34μg/g),and the content of Pb was in the range of 0.18μg/g to 14.90μg/g(average4.36μg/g).g);Cd element content ranges from 0.41 μg/g to 25.40 μg/g(mean value 4.78 μg/g).The contents of Zn and Cd in feathers of grass seabirds are much higher than those reported in other regions,but the Pb content is not much different from other ecosystems.The correlation analysis of different heavy metal elements in bird feathers showed that the pollution sources of bird Zn and Pb and Cd elements were different.The different parts,feeding habits and sex of birds in the Caohai region are not the main factors affecting the content of heavy metals in bird feathers;the content of heavy metals in bird feathers increases with age.From the differences in the distribution of heavy metals in birds with different migration characteristics,it can be seen that the existing heavy metal pollution in Caohai has a greater impact on the Zn content of bird feathers,making the Zn content in the resident birds larger than that of migratory birds;while the content of lead and cadmium in migratory birds is higher than that of the resident birds,indicating that they are migratory birds.In other living areas,there may also be lead and cadmium contamination,and the source of its pollution needs further study. |
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