ICP-OES research on the spatial distribution characteristics and ecological risk assessment of heavy metals in the surface sediments of the North Canal

The ecological risk assessment of heavy metal elements in river sediments is of great significance to the study of the pollution degree and migration and transformation laws of heavy metals in river basins. The North Canal is an important pollutant-receiving river in the BeijingTianjin-Hebei region. The distribution characteristics and ecological risks of heavy metals in the whole basin are still unclear. In order to fully understand the occurrence level of heavy metals in the sediments of the Beiyun River basin, the study selected 17 national and provincial control sections to collect surface sediments in the upper, middle, and lower reaches. Pre-treatment of sediment samples using aqua regia extraction-water bath digestion and continuous extraction method, inductively coupled plasma emission spectrometry (ICP-OES) simultaneous determination of eight kinds of As, Cd, Cr, Cu, Mn, Ni, Pb and Zn The content and form of the elements, and carry out ecological risk assessment on them. The results show that the average content of heavy metals in the surface sediments of the North Canal is Mn>Pb>Zn>Cu>Cr>Ni>Cd>As. The average content of heavy metal elements Pb, Zn and Cu is higher than the background value, and the average content of Pb element is more than 4 times the background value. The spatial variation of different heavy metals is quite different, and the content in the middle and lower reaches is relatively high. Through morphological analysis, it is found that the forms of Cd and Zn elements are mainly acid-soluble and reducible, with strong biological activity and greater harm to the environment; the forms of As, Mn, Cr, Cu, Ni and Pb elements are mainly available. Mainly oxidized state and residue state, with weaker biological activity and less harmful to the environment. The geoaccumulation index ( I (geo )) indicates that heavy metal pollution from external sources is serious, Pb ( I (geo) = 2.24) pollution levels are heavy, Cu (I (geo) = 1.44) and Cd (I (geo) = 1.45) pollution levels are medium, and Zn (I (geo )= 1.45) pollution levels are moderate.=0.99) The pollution level is relatively light, and other elements are at the pollution-free level. The potential ecological risk index shows that the comprehensive ecological risk of heavy metals in the surface sediments of the North Canal basin is low. Only the presence of Cd makes the North Canal with a medium risk, and none of the other elements poses a risk to the North Canal (low risk). Principal component analysis showed that heavy metals in the surface sediments of the North Canal Basin mainly come from the unreasonable use of pesticides and fertilizers, atmospheric deposition, and emissions from industry and transportation. Compared with other typical river basins in my country, the heavy metal content of surface sediments in the North Canal basin is relatively low. Provide data support for subsequent North Canal governance and management.