Spatio-temporal distribution and release characteristics of As in sediment-overlying water of Daye Lake
In this study,arsenic(As)in the sediment-overlying water of Daye Lake was taken as an object,the corresponding samples were collected in winter(February)and summer(August),respectively.The content,forms of occurrence and spatio-temporal distribution characteristics of As were analyzed,and the factors affecting the release of As between the interface of the sediment-overlying water were studied.At last,the ecological risk level of As in the sediments of Daye Lake was evaluated through the methods of geologic cumulative index and potential ecological risk index.This will provide theoretical basis and guidance for the precise prevention and control of As pollution in Daye Lake and other urban shallow lakes in the middle and lower reaches of the Yangtze River.The results showed that there is a significant seasonal difference in the content and distribution of As in Daye Lake.In winter and summer,the average values of As mass concentration in the overlying water were 3.38 μg·L-1 and 51.6 μg·L-1,respectively,and As mass concentration in winter could meet the class Ⅲ of environmental quality standards for surface water,while As mass concentration fluctuated a lot in summer and the sample points with high As mass concentrations were mainly distributed in the central and southeastern regions.The average values of As mass contents in the sediment were 79.6 mg·kg-1 and 94.6 mg·kg-1 in winter and summer,respectively.And the spatial distribution of As was not uniform,which was mainly enriched in the western and central part of Daye Lake,the analysis indicated that this might be closely related to anthropogenic activities.The forms of As occurrence in the sediment was mainly the stable residual form and the proportion of the extractable form of As in the summer was higher than that in winter,implying a high potential ecological risk of As in summer.The released flux experiments of As showed that the release flux of As from sediments was negatively correlated with ambient pH and positively correlated with temperature,and that both disturbance and aerobic state could promote the release of As.The evaluation of potential ecological risk showed that As pollution in the sediments of Daye Lake was serious,and the potential ecological risk in summer was higher than that in winter.Thus,it is urgent to implement the prevention and control of As pollution and ecological protection in Daye Lake.
Daye lakesedimentsarsenicTemporal and spatial distributionrelease characteristics
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