A Case Study: Arsenic, Cadmium and Copper Distribution in the Soil–Rice System in Two Main Rice-Producing Provinces in China

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Arsenic (As) and cadmium (Cd) pose great risk to rice plants and human health. Copper (Cu) agrichemicals also draw increasing attention. This study investigated the distributions of As, Cd and Cu in the soil–rice system in two major rice-producing provinces, Hunan and Jiangxi, China. Arsenic in soils at site A in Hunan reached 47.95–60.25 mg/kg, all exceeding the national standard (GB15618-2018), but As in rice was all below the safe limit for humans (0.20 mg/kg, GB2762-2017). In contrast, As in all rice husks and 5% of grain samples from Jiangxi exceeded the safe limit, while As in soils was 3.40–9.92 mg/kg, all below the standard. Cadmium in soils at site A and site B in Hunan were 3.96–5.11 and 1.83–2.77 mg/kg, respectively, all exceeding the national standard; Cd in 60% of rice grains exceeded the safe limit (0.20 mg/kg, GB2762-2017). Despite Cd in soils from Jiangxi being much lower (0.20–0.34 mg/kg), Cd in 56% of the rice grains exceeded the safe limit. The different distribution patterns of As and Cd in the soil–rice system probably result from the dynamic environmental conditions during farming practice. Risk from dietary products made from rice husks should also be considered. Although not regulated in rice, Cu in the soil from Hunan exceeds the national standard. This study helps to understand As and Cd pollution in paddies and its risk to human health, and suggests limiting the application of Cu-based agrichemicals.