Heavy metal pollution and ecological risk assessment of arable land soil in Haigou small watershed

In order to understand the current situation of heavy metal pollution in the arable land of the Haigou small watershed, 106 samples of the surface soil of the arable land were collected in the small watershed, and the inverse distance weighting interpolation method and the Hakanson potential ecological risk index method were used to analyze the distribution of Cd, Pb, Hg, Cu and As in the arable land, in combination with the RS image interpretation and the ArcGIS land statistics method. The results showed that the average contents of heavy metals Cd, Pb, Hg, Cu and As were 0.307, 23.422, 0.041, 21.544 and 12.235 mg∕kg respectively, which were all higher than the background values of Heilongjiang Province. Compared with Soil Environmental Quality Standard (GB 15618-1995), the content of Cd exceeds Class Ⅱ standard, and that of other heavy metals meets Class Ⅰ standard. In terms of the spatial distribution of heavy metals, it was found that the change of As content gradually decreased from east to west, and the change of Cd content was opposite to that of As, which gradually decreased from east to west. The potential ecological risk of the arable land was evaluated by the Hakanson potential ecological risk index method. The results showed that the ecological risk grades of Cd and Hg in the arable land of the Haigou small watershed were relatively high and medium, while that of Pb, Cu and As were mild. Therefore, the potential ecological risk of the farmland in the Haigou small watershed was generally in the middle.