Integrated management strategies for arsenic and cadmium in rice paddy environments

Abstract

Cadmium (Cd) exposure risks to consumers of locally grown rice are often estimated without considering the sources and bioavailability of Cd. Here, we present the first comprehensive and quantitative analysis on the sources and transport of Cd in paddy ecosystems by combining a regional investigation in southern China, a positive matrix factorization algorithm, and a classification and regression tree approach. Results showed that local atmospheric emission regulations failed to mitigate Cd contamination as the Cd inputs from industrial effluent irrigation were largely overlooked. Leaching loss of soil Mn is an invisible threat to grain safety as Mn can exhibit a significant facilitation effect on rice Cd uptake under acidic pH. A probability-based toxicokinetic model is proposed to optimize the strategies for minimizing the Cd body burden through the source-soil-rice-human pathway. Urinary Cd exceeded its safety threshold in 61.7 % of local female adults (6.14 ± 4.42 µg g-1 creatinine) who consumed less rice grain but with a low Zn bioavailability. To protect 85 % of local rice production from causing excessive Cd exposure risk, irrigation channel needs to be effectively cleaned up, and the pH and amorphous Mn content of rice soils need to be raised to 5.50 and 179 mg kg-1, respectively.