Water management impacts on the solubility of Cd, Pb, As, and Cr and their uptake by rice in two contaminated paddy soils.

Agricultural soil contaminated with heavy metals and the subsequent heavy metals uptake by rice have increasingly been reported in the last few decades. In this study, pot experiments with two contaminated soils (acidic soil from Jiangxi Province and slightly alkaline soil from Hunan Province) were conducted to investigate the effects of water management (flooding and aerobic treatment) on the uptake of cadmium (Cd), lead (Pb), arsenic (As), and chromium (Cr) by rice (Oryza sativa L.). The pore water contents of these heavy metals were determined during the growing season. Flooding the soil decreased Cd, Pb, and Cr in soil pore water, but increased As in the soil solution. Relative to the aerobic treatment, flooding decreased the Cd in the soil solution by 17.3-94.5% and 54.7-88.3% in acidic and slightly alkaline soils, respectively. The total As in the soil solutions increased by 0.2-20.9 and 0.1-15.2 times throughout the growing season in acidic and slightly alkaline soils, respectively. In acidic soil, flooding significantly decreased the Cd contents in iron plaque and rice tissues, significantly increased the Cr content in iron plaque, slightly decreased the Cr uptake by rice, and decreased the Pb content in the aboveground parts of rice, and increased the Pb content in rice roots and iron plaque. Relatively fewer changes were observed in rice grown in slightly alkaline soil. Results suggested that flooding the acidic soil had mixed results on heavy metal bioavailability, and the bioavailability in slightly alkaline soil was not notably impacted by flooding.