Distribution Characteristics Of Nutrient Elements And Heavy Metals And Its Risk Assessment In Sediments Of Villages In Baiyangdian Lake

Based on the Baiyangdian Lake(BYDL)in Xiong'an New District,this paper studies the water areas affected by human life that are connected to the BYDL Village and the Lake.The ecological toxicity evaluation of sediments in the typical village waters of BYDL is carried out,and the influence of village waters on the ecological security of the Lake is studied,so as to provide basic data support for the endogenous governance and ecological restoration of rural water environment in BYDL.Five typical villages in the BYDL Lake,Xiazhang zhuang(XZZ),Datianzhaung(DTZ),Dizhuang(DZ),Quantou(QT)and Caiputai(CPT),were selected as the research objects.For the open water surface and ponds around the village.Four different types of waters,trenches and waterways,were studied experimentally.DO,ORP,p H,CODcr,NH₃-N,NO₃-N,TN,SRP and TP were determined in overlying water,and water pollution characteristics were analyzed based on?GB 3838-2002?;The spatial distribution characteristics of nutrient elements(N,P,S,C)and heavy metals(Cd,Cr,Cu,Ni,Pb,Zn)in sediments were analyzed.Organic pollution index(OPI),sediment pollution index(SPI)and potential ecological risk index(RI)were employed to systematically evaluate the sediment pollution levels and ecological risks.23 representative sites were selected from 5 villages in the BYDL and 4 different water areas to extract the speciation of heavy metals,and the Risk assessment code was used to evaluate the degree of heavy metal pollution in villages in the BYDL based on the proportion of acid extractable state in total.The chironomid larvae were selected as indicator organisms,and the survival rate,SOD and Car E activities were detected after ten days of culture.(1)The overlying water around the middle village of BYDL is generally in the V-type water standard of surface water.The contents of TP and TN were lower than the surface water standard III(0.05 mg·L^-1and 1.0 mg·L^-1).The average value of ammonia nitrogen is in the range of surface water standard III,but the maximum value is 5.01 mg·L^-1,and the difference is large.DO index is lower than the surface water standard III water;The ORP value is between 158m V?-225m V,with an average value of 73.20m V.Some water bodies are black and smelly water bodies.(2)The mean values of TN and TP in sediments were 1687.16 and 642.91mg·kg^-1,respectively.The maximum values of TN and TP were in the waters of DTZ waterway,and the order of the average content of TN was waterway>ditch>pond>lake region near the residential area.Except CPT,the OPI of the villages were at level IV,which indicated that the organic pollution and organic nitrogen pollution in sediment were considerably serious.The average concentration of Cd,Cr,Cu,Ni,Pb,and Zn were 0.17,55.77,35.52,28.25,19.99 and 119.74 mg·kg^-1,respectively.Correlation analysis showed that Cd was correlated with secondary phase,and the correlation coefficient was 0.749.The average enrichment factor of Cd is 1.65,so the source of Cd is mainly human input.The risk coefficients are SPI=1.85<5,RI=76.87<150,respectively.(3)The biological toxicity of sediments in village waters is DZ>XZZ>QT>DTZ>CPT.The biological toxicity of sediments in DZ waters is medium to high level,and the other four villages are mostly medium to low toxicity.The survival rate of Chironomid larvae was about 60%,and there was no significant change in the insect body,which was highly sensitive to external stimuli.SOD activity villages in the BYDL was significantly correlated with B1 Cu at p<0.01 level.At the significant level of p<0.01,TN,TC,Ni and Zn were significantly correlated with Car E activity,and the correlation coefficients were 0.415,0.381,0.372 and 0.319,respectively.At the significant level of p<0.05,Cu,TS and TP were significantly correlated with Car E activity,with correlation coefficients of 0.309,0.302 and 0.268,respectively.