Inventories of toxic elements in soil-rice systems in the main rice cultivated regions in China

To mitigate accumulation of potentially toxic elements (PTEs) in soil-rice systems, the quantification of inventories is essential. This study investigated PTE fluxes, including input fluxes from atmospheric deposition, fertilizers, irrigation water, and output fluxes from surface runoff and plant uptake in the main rice-cultivated region in China, which includes Yangtze River Basin (YRB), Southeast Coastal Region (SCR) and Northeast Plain (NP). Based on the calculated net fluxes, the future trend of heavy metal accumulation was also predicted. The results showed that atmospheric deposition was the dominant input source for Cd, Pb, Cr, Cu, and Zn (51.9–84.0%), while irrigation was the main source of Cd and As in SCR due to higher average PTE concentrations and irrigation demand. Fertilizers contributed 47.7% of Hg inputs. Surface runoff accounted for 11.9–78.3% of total outputs. The net accumulation rates of Cd in all three regions, and Cu and Zn in SCR region were the fastest and should be controlled first. Overall, for PTEs in soil-rice systems, the atmospheric deposition was still the dominant input source, but the contribution of surface runoff was not neglectable, which was different from the generalized soil-crop systems. These findings provide guidelines to decrease PTE net fluxes and facilitate a transformation from remediation to prevention PTE pollution. • The atmospheric decomposition was the dominant input source for all heavy metals except Hg. • Fertilizers were the main source of Hg inputs. • One of the primary sources of heavy metals in paddy soils was surface runoff. • It is important to pay more attention to preventing additional Cd accumulation.