Assessment of Arsenic Distribution in Paddy Soil and Rice Plants of a Typical Karst Basin Affected by Acid Mine Drainage in Southwest

The influence of arsenic coal mine on nearby paddy fields was surveyed in Guizhou province, China. The paddy fields were divided into three areas using cluster analysis based on the soil pH, Fe and As contents. The average values were 6.5, 68.70 g/kg and 47.36 mg/kg in Area I, were 5.2, 62.36 g/kg and 82.88 mg/kg in Area II, and were 4.3, 78.38 g/kg and 121.03 mg/kg in Area III, respectively. The mobile As contents in Areas II and III were higher than in Area I. The enrichment of As in paddy soil and change of soil properties increased the arsenic concentration in rice plants, where the transfer factor of As from soil to rice grain was about 0.009. The average As concentrations in Areas I, II and III were 9.58, 21.67 and 25.41 mg/kg in roots of rice, 2.50, 3.41 and 3.90 mg/kg in straw, and 0.42, 0.85 and 1.09 mg/kg in grain, respectively. It was estimated that the daily intake of total As and inorganic As for a 60 kg adult through rice consumption were above 4.2 μg/kg body weight/day and above 0.144 mg/day, respectively. The correlation analysis showed that As concentration in rice had a significant positive correlation with soil As concentration (rroot = 0.672, p < 0.05; rstraw = 0.725, p < 0.01; rgrain = 0.759, p < 0.01), a negative correlation with soil pH, K, Ca and Mg contents, and a positive correlation with soil organic matter and Fe content