Geographical variation in arsenic, cadmium, and lead of soils and rice in the major rice producing regions of China.

Rapid industrialization and urbanization have accelerated the contamination of paddy soils with potentially toxic elements (PTEs). However, the status and the key factors responsible for the geographical variation in PTE concentrations in rice remain poorly understood. Here, a total of 113 pairs of soil and rice plant samples were collected from 19 provinces in four major rice producing areas of China to assess the geographical variation in total arsenic (As), cadmium (Cd) and lead (Pb) concentrations in the soil-rice system. Average total concentrations of As, Cd and Pb were 11.8, 0.45 and 25.7 mg kg-1, respectively, in the soils and 0.089, 0.087 and 0.036 mg kg-1 in the polished rice. The national maximum allowable concentrations of total soil As and Cd were exceeded in 6.19 and 33.6% of soils and that of Cd was exceeded in 7.96% of polished rice and no polished rice exceed the Pb limit. The As, Cd and Pb concentrations of rice were significantly and positively correlated (p < 0.05) with their corresponding soil available concentrations rather than with their soil total concentrations. Due to the combined effects of local rice varieties, cultivation of varieties with high Cd translocation factors and high Cd availability in acid soils, the highest rice Cd risk occurred in south China. The Cd concentrations in polished rice exceeded the maximum allowable by 4.0 and 15.8% in uncontaminated and contaminated soils, respectively. Results from 113 fixed samples may represent the actual current As, Cd and Pb status of rice in the main rice production areas nationally as they were very consistent with 574 random samples. In view of the high Cd contamination risk in acid soils of south China, countermeasures are needed to minimize Cd accumulation in rice crops in this region.