Evaluation of Contamination and the Ecological Risk of the Heavy Metals in the Farmland Soil Influenced around an Uranium Mine in Southwest China

The farmland surface soils effected by uranium tailing were sampled, and the contents of 238U, 232Th, 226Ra, Cu, As, Cd, Pb and Zn in the samples were analyzed. The Index of Geoaccumulation and the Potential Ecological Risk Index were employed to evaluate the pollution degree of heavy metals in the soil. The results showed the content of Cd, As, Pb, 238U and 226Ra in the farmland soil exceeded background value. The Index of Geoaccumulation indicated the main polluted factor influencing farmland soil was 226Ra (highly contaminated), the next was 238U and Cd (uncontaminated-moderate contaminated). The potential ecological risk intensity caused by Cu, Zn, Pb and As are all low, and by Cd was moderate contaminated. The potential ecological risk level of integrated heavy metals was low in the study area, and Cd was the main factor. However, the potential ecological risk assessment did not take into account the effects of radionuclide 238U, 232Th, 226Ra, so that and the results of the potential ecological risk were less than that of actual. The metals input in farmland soil are possibly caused by uranium tailings loss and their seepage.