Farmland Soilheavy Metal Risk Assessment Of New Submergedareain Danjiangkou Reservoir Area

Soil heavy metal pollution with concealment,was not easy to degrade, which can be direct or indirect harm to human health through a variety of ways, has become the important issues in environmental science research. Danjiangkou reservoir was not only the water source of south-to-north water transfer project but also the biggest drinking areas of tens of millions people. To ensure the safety of the reservoir water quality was not only related to the success of the entire project but also related to the lives and health of countless people. As the Danjiangkou dam heightening, more than 30 acres farmland of the new submerged will become the new reservoir sediment, accumulation of heavy metals in farmland soil will be released into the water under suitable conditions and reservoir water quality was affected even endanger human body health, thereby in order to maintain the ecological environment of Danjiangkou reservoir, it is necessary to study the pollution degree and the spatial distribution characteristics about Farmland soil heavy metal and assessment the ecological risk. The spatial distribution、pollution characteristics and Correlation analysis of 6 kinds of soil heavy metals(Cr、Cd、Pb、Zn、Cu、As) in farmland soil from submerged area in Danjiangkou reservoir was analyzed through field investigation which got 165 soil samples from the farmland. the geoaccumulation index method and potential ecological risk index method were applied to assess the ecological risk of heavy metals, the results indicted:(1) Among six kinds of heavy metal elements in this study,except for Cr and As, the rest of the four kinds of heavy metal element is higher than the national soil environmental background values, among them, Zn and Pb has little difference with the national soil environmental background values, Compared with the national environment background value, the element of Cr was less than 11.2 mg/kg, and the element of Cu was more than18.6 mg/kg. The element of Cd was 13.04 time of the national environment background value. The coefficient of variation range of 0.34-1.17 about six kinds of heavy metals,except for As belongs to the height variation, other heavy metals belonged to moderate variability.(2) The inverse distance weighting method was used to study the spatial distribution of soil heavy metals, the results indicted: The Heavy metal elements Cr、Pb、Zn、Cu had some similarities and showed strong spatial variability about spatial distribution in entire Danjiangkou Reservoir, the high soil heavy metals were distributed in the place of the population density and the intensity of human activities such as Xichuan country,Danjiangkou city area, Jiuchong town and Shengwan town of Henan province by spatial analysis technology, It is consistent with the distribution of Danjiangkou Reservoir pollution sources distribution. There were so vast factories that produce potential pollution sources in these areas, in addition, large agricultural production strength in these areas,pesticide and fertilizer using in agricultural activities, also may be an important source of heavy metals in contaminated soil; the spatial variability of Cd was not obvious, the content was high in the entire region; the spatial distribution of As was different from other heavy metals, In the northwest of the reservoir tributaries, that was a higher content of Taohe town、old town and Shengwan town in Xichuan. human activities in these towns were more active, such as wastewater irrigation, pesticides fertilizer usage was likely to be the leading cause of the As content is higher.(3) Correlation analysis results showed that the p H and As、Cr、Pb show extremely significant correlation(p < 0.05) and Cd、Cr、Cu、Pb、Zn show significant positive correlation between them(p < 0.05), indicating that the sources of heavy metals has similarity, namely soil has composite pollution characteristics.(4) The Geoaccumulation index(Igeo) was used to assess the harm of soil heavy metals, the results show that heavy metal pollution levels order Cd > Cu > Pb >Cr>As>Zn about soil heavy metal of the new submerged areas in the Danjiangkou Reservoir. In addition to Cd reached serious pollution levels, and the rest of 5 kinds of heavy metal pollution were in non-pollution or light pollution levels.(5) The potential ecological risk index was use to assess the potential ecological risk assessment of soil heavy metals, results showed: the potential ecological risk of soil heavymetals index(RI) was up to 3155.58 and in strong ecological risk level; 6 kinds of potential ecological risk coefficient of heavy metals order Cd> Cu> As> Pb> Cr> Zn,Among them the element of Cd was 393.18 and belong to strong ecological risk levels, the other five kinds of heavy metals were in slight ecological risk levels.