Mercury in soils of three agricultural experimental stations with long-term fertilization in China.

Mercury (Hg) in the agricultural ecosystem is a global concern because of its high potential toxicity. The objectives of this study were to determine the concentration and distribution of Hg in soils from three long-term experimental stations, i.e., Taoyuan (TY) and Qiyang (QY) in Hunan Province and Fengqiu (FQ) in Henan Province of China, and thus to assess the possible food and health risk of long-term applications of fertilizers. Soil samples at each site were collected from different fertilization plots and also from soil profiles with depths 0-100 cm. There were significant differences in soil Hg concentrations in 0-20 cm (A) or 20-40 cm (B) horizon among the three experimental stations. QY station showed significantly higher Hg concentrations than TY and FQ stations. However, there were no significant differences in soil Hg concentrations between A and B horizons at each station. It was concluded that the soil Hg concentrations at the three sites were mainly controlled by the parent materials. Moreover, chemical fertilizer, especially phosphorous fertilizers, could influence the soil Hg concentrations to some extent at the station with lower soil Hg concentrations, for example, at TY station. There were minimal amounts of Hg resulting from applications of the other chemical fertilizers and organic manure, and thus the fertilization had very low risk to the food security of the agro-ecosystems in the terms of Hg inputs and contamination.