Biological Monitoring And Evaluation Of Combined Pollution Of Typical Wetlands In Baotou City

The wetland area of Baotou City is shrinking year by year,and is subject to different degrees of pollution.The pollutants mainly include rare earths,heavy metals,various salt ions,radioactive pollutants,antibiotics,and ammonia nitrogen,which was typical compound pollution.It lead to serious damage to wetland ecological functions and biological species.At present,the research on urban wetlands mainly focuses on the construction of constructed wetlands and sewage treatment.There are relatively few reports on biological monitoring and evaluation of combined pollution levels.The purpose of this study was to clarify the main pollution factors and the toxic effects of combined pollution on B.raddei.Our work aimed to find one or several biological monitoring indicators that could will reflecting the water quality,and then use these indicators to assess the pollution degrees of wetlands.It is of great significance for the prevention,control,monitoring,and evaluation of urban wetland pollution and local amphibious population protection.In this study,B.raddei was taken as the research object,a Tailings Reservoir Wetland in Inner Mongolia and Kunhuang intersection wetland as the research sampling sites,and Xiaobaihe Yellow River wetland as the control sampling site.Combined with field investigation and laboratory analysis,the main pollution factors were analyzed by comparing and analyzing the contents of heavy metals and rare earth elements in sediment,water and tissues of B.raddei in three sampling sites.By analyzing genotoxicity,antioxidant enzyme activity,histopathological changes and physiological responses,the ecotoxic effects of typical wetland combined pollution in Baotou City on local amphibians were studied.By analyzing genotoxicity,antioxidant enzyme activities,histopathological changes,and physiological responses,to study the ecological toxicity effects of typical wetland combined pollution on the B.raddei.The single factor pollution index and the Nemero index were used to evaluate the degrees of heavy metals pollution in the sample sites.The comprehensive biomarker response index method(IBRv2)was used to evaluate the overall pressure of urban wetland combined pollution on the B.raddei,and to reveal the wetland water environmental risks.Through the correlation analysis of the above indicators,the biological monitoring and evaluation effects of the typical wetland complex pollution in Baotou City were studied.The Genotoxicity indexes mainly analyzed micronuclei(MN)and DNA damage.The activity indexes of antioxidant enzymes mainly analyzed total superoxide dismutase(SOD),glutathione(GSH),malondialdehyde(MDA),glutathione peroxidase(GPx),and total antioxidant capacity(TAOC).Meanwhile,histopathological changes of liver,kidney,and testis were analyzed.Physiological responses indexes mainly analyzed the length,weight,conditional factors(CF),and liver body index(LSI).The results show that: compared with the Yellow River wetland,the contents of Cr,Cu,Zn,and Cd in the sediments of Tailings Wetland and Kunhuang wetland were significantly different(p< 0.05).The contents of light rare earth elements in the sediment of Tailings wetland were significantily higher than that in Kunhuang and Yellow River(p<0.05),and the highest reached9884.72 +1682.49 mg/kg.Bioaccumulation factor(BAF)showed that Zn,As,Cr,Cu,and Pb were most easily absorbed by B.raddei.The genotoxicity analysis showed that the degrees of DNA damage of red blood cells were Kunhuang > Tailings reservoir > Yellow River,and Kunhuang and Tailings wetlands were 4.49 and 3.62 times of Yellow River wetland respectively.The micronucleus rates of red blood cells were 11.7 and 5.8 times of that in Yellow River wetland.The SOD activities,MDA contants,and T-AOC values of testis,liver,and kidney in Tailings and Kunhuang wetlands were significantly higher than that in the Yellow River wetland(p<0.05).The IBRv2 index of the Tailings wetland was higher than that of Kunhuang and Yellow River wertland.Therefore,these results showed that:(1)Heavy metals were the main pollution factors of typical wetlands in Baotou City.(2)The higher contents of heavy metals in the tissues of B.raddeiwere the main cause of toxicities in Tailings and kunhuang wetlands.(3)Compound pollution of typical wetlands in Baotou City has effected on the genetic toxicity,oxidative stress,and physiological response of B.raddei.Among them,DNA damage,MDA,TAOC,MN,DNA damage,CF,and LSI were the most sensitive indexes,and their sensitivities were in the order of MN > LSI > CF > DNA damage > MDA > T-AOC > MDA.(4)The results of IBRv2 showed that the Tailings wetland were the most polluted site.IBRv2 can make good warning of wetland environmental pollution comprehensively and intuitively,and make environmental monitoring more perfect and scientific by combining physical and chemical analysis with IBRv2.The results of this project intuitively revealed the mechanism of toxicological effects on amphibians under the typical wetland complex pollution.And the ecological indicators were used to make a reasonable assessment to the wetland composite pollution in Baotou City.It is of great significance to the protection of local amphibious populations and the prevention,control,monitoring,and evaluation of rare earth Tailings wetland pollution.