Abstract: Mercury pollution in 15 vegetable species collected from a cropland near a closed mercury mine and their health risk were assessed in this article. The results showed that the concentration of total mercury differed with vegetable species, with an order of leafy vegetables > solanaceous vegetables > tuber vegetables. Among the 15 vegetables, the concentration of total mercury in lettuce was the highest (57 mg·kg^-1), whilst that in white radish was the lowest (1.67 mg·kg^-1). For the leafy and tuber vegetables, the concentrations of total mercury differed greatly in different parts of vegetable. For six leafy vegetables and two tuber vegetables, the concentration of total mercury in aboveground part was higher than that in underground part. For six leafy vegetables, the concentrations of total mercury in outer part, central part and their mixture were in the order of outer > mixture > central. For the two tuber vegetables, the concentrations of total mercury in leaf, root and root skin were in the order of leaf > root skin > root. The concentrations of total mercury in air and soil were 128-1109 ng·m^-3 and 3.88-91.62 mg·kg^-1 respectively, indicating that both the air and soil in this area were polluted by mercury. The risk assessment indicated that eating vegetables alone did not pose a risk to health of the residents living in this area, but it might not be true if other mercury exposure pathways were comprehensively considered.

Key words: biochar, soil organic carbon, priming effect, carbon sequestration, mineralization