Abstract:In order to determine the inhibitory effect of the application of KMnO4-modified pig manure biochar(MZC) on the uptake and accumulation of Hg and Cd in rice from a combined pollution soil, pot experiments were carried out to investigate the effects of different dosages of MZC on the accumulation and distribution characteristics of Hg and Cd in rice, the concentrations of available Hg and Cd in soil and soil physiochemical properties, and the possible inhibitory mechanism of MZC on the heavy metals in rice grains was also discussed. Results show that compared to the blank control, the addition of 0.5% MZC reduces the concentrations of total Hg, methyl Hg and total Cd in rice grains by 50.4%, 58.4% and 79.3%, respectively, and the concentrations of available Hg and Cd in rhizosphere soil also are decreased by 31.1% and 39.9%, respectively; however, the concentration of total Mn in rhizosphere soil is increased by 70.3%. Furthermore, the addition of 0.5% pristine pig manure biochar decreases total Hg, methyl Hg and total Cd in rice grains significantly less than the addition of 0.5% MZC, indicating that the modification of KMnO4 can significantly enhance the ability of pristine pig manure biochar to passivate Hg and Cd in soil. The concentrations of Hg and Cd in rice grains, stems and leaves and the concentrations of available Hg and Cd in rhizosphere soil are decreased significantly with increasing the addition dosage of MZC. Correlation analysis shows that the concentrations of THg, MeHg and TCd in rice grains, stems and leaves are significantly positively correlated with the concentrations of available Hg and Cd in soil, but the concentrations of available Hg and Cd in soil show negative correlation with soil pH and CEC. The addition of MZC increases soil pH and CEC, which decreases the bioavailability of Hg and Cd in rhizosphere soil, and thereby reduces the uptake or accumulation of Hg and Cd by the aboveground parts of rice from polluted soil. Therefore, MZC is a promising remediation agent to ensure the safe production of rice in the Hg and Cd contaminated paddy.