Effect of simulated acid rain on leaching and transformation of vanadium in paddy soils from stone coal smelting area

The agricultural soil contaminated with vanadium (V) has been attracting attention due to its adverse effect on human health and ecosystems. In this study, the leaching risk and transformation characteristics of V in contaminated paddy soils collected from the vicinity of stone coal smelting area were evaluated by a column leaching experiment with simulated acid rain (SAR). The results showed that the amount of soluble V leached was slight and only accounted for 0.04-0.06% of the total V, however, the concentrations of V in leachates after leaching with 10 years of rainfall precipitation using SAR at pH 4.5, pH 5.6 and neutral pH 7.0 were found to to be 49.0, 71.3 and 61.1 μg/l, respectively, which were higher than or near to the V threshold limit of Chinese Environmental Quality Standards for Surface Water (50 μg/l) (GB 3838-2002). The percentages of V in both the reducible and oxidizable fractions of the soils increased by 2.10-3.50%, whilst that in residual fraction decreased by 4.52-6.07% after leaching. The results suggest that the mobility of V in polluted paddy soil is increased by long-term rainfall leaching and poses a potential risk of V pollution in surrounding water.