锰改性猪粪炭对水稻吸收累积土壤中汞镉的影响

为了探明KMnO4改性猪粪炭对水稻吸收累积复合污染土壤中汞镉的阻控效果，通过盆栽试验研究添加不同量的锰改性猪粪炭（MZC）对水稻中汞镉累积分布特征、根际土壤有效态汞镉含量和土壤理化性质的影响，并探讨了MZC阻控水稻籽粒吸收累积汞镉的可能机制。结果表明：与空白对照相比，添加0.5%MZC使水稻籽粒的总汞、甲基汞和总镉含量分别降低了50.4%、58.4%和79.3%，同时降低了31.1%和39.9%根际土壤有效态汞和镉的含量，但增加了70.3%根际土壤总Mn含量；且添加0.5%的原始猪粪炭对水稻籽粒中总汞、甲基汞和镉含量的降幅显著小于锰改性猪粪炭的，表明经过KMnO4改性可以显著增强猪粪炭对土壤汞镉的钝化能力。水稻籽粒、茎叶中的汞镉含量和根际土壤有效态汞镉含量都随着MZC添加量的增加呈明显的降低趋势。统计分析显示水稻籽粒和茎叶中的汞镉含量与根际土壤中有效态汞、镉呈显著正相关性，而土壤中有效态汞镉含量与土壤的pH、CEC呈负相关。添加MZC使土壤pH、CEC升高，降低了根际土壤中汞、镉的生物有效性，从而减少了水稻地上部分对汞镉的吸收累积。因此，锰改性猪粪炭是一种具有应用潜力的能保障汞镉复合污染农田水稻安全生产的土壤修复剂。

Effect of Mn Modified Pig Manure Biochar on Uptake and Accumulation of Hg and Cd in Rice

In order to determine the inhibitory effect of the application of KMnO4-modified pig manure biochar (MZC) on the uptake and accumulation of mercury (Hg) and cadmium (Cd) in rice from a combined pollution soil, the 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 mercury and cadmium in soil and the physical and chemical properties of soil, and the possible inhibitory mechanism of MZC on the heavy metals in rice grains was also discussed. Results showed that compared to the blank control, the addition of 0.5% MZC reduced the concentrations of total Hg, methyl mercury and total Cd in rice grains by 50.4%, 58.4% and 79.3%, respectively, and the concentrations of available mercury and cadmium in rhizosphere soil also decreased by 31.1% and 39.9%, respectively; however, the concentration of total Mn in rhizosphere soil increased by 70.3%. Furthermore, the addition of 0.5% pristine pig manure biochar decreased obviously less amounts of total Hg, methyl mercury and Cd in rice grains than the addition of 0.5% MZC, indicating that the modification of KMnO4 could 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 decreased significantly with increasing the addition dosage of MZC. Statistical analysis showed that the concentrations of Hg and Cd in rice grains, stems and leaves are significantly positive correlation with the concentrations of available Hg and Cd in soil, but the concentrations of available Hg and Cd in soil show negative correlations with the values of soil pH and CEC. The addition of MZC increased the values of soil pH and CEC, which caused the decrease of the bioavailability of Hg and Cd in rhizosphere soil, and thereby reduced the uptake or accumulation of Hg and Cd by the aboveground part 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.