Environmental effect of mercury contamination of farmland soils in the Tongguan gold mining area, Shaanxi, China

The paper focuses on the mercury contents in wheat, vegetable and fruit in mercury contaminated farmland soils in the Tongguan gold area and their comparison with those in uncontaminated farmland soils, as well as the crop effect of mercury contamination of soils. The Hg content of the wheat sample in the evaluation area is 78.5% higher than the standard rate. The excess of the standard rate is notably related to mercury contamination of soils. The mercury content in the radish sample in the evaluation area is 40% in excess of the standard rate and the percentage rates of exceeding the mercury content standards for the leaf vegetables, tomato, apple and sweet potato are all 100%. The mercury contents in fruits and vegetables in the contrast area all exceed their standard rates but notably lower than those in the evaluation area. The crops in the evaluation area are listed in decreasing order of times higher than the standard mercury contents as follows: green vegetables > oil vegetable > radish leaf > tomato > apple > sweet potato > wheat>radish. The environmental effect of mercury-contaminated soils is very serious. It is urgent to control environmental contamination in the mining area.