Fluorine pollution characteristics and risk assessment of electrolytic aluminum plant site in high fluoride area

Based on the environmental investigation of the fluorine-contaminated site located at a typical fluorine rich region in China, the distribution characteristics of fluoride pollution level were analyzed, the underground migration characteristics of fluoride in different depth soil layers in the heavily polluted areas investigated, and the environmental risk effect of fluoride of the sites evaluated based on different landuse functions. The results showed that the concentrations of fluoride in surface soil ranged from 3 340 to 38 400 mg/kg, while the water-soluble fluoride content ranged from 0.06 to 25.40 mg/L. The over-standard rate was as high as 96% compared with the local soil fluoride background value. The occurrence forms of fluoride in soil were mainly residual state with percentage of 93.88% and the water-soluble percentage was 0.85%. The underground migration behaviours of fluoride were affected by soil types of the contaminated site, where the fluorine was strongly adsorbed and detained by the clay layer. The healthy risk was over the acceptable level when the contaminated site was used as the Classification Ⅰ lands, represented by residential land. If it was used as Classification Ⅱ lands, represented by industrial land, its hazard did not exceed the acceptable risk level.