State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China.
Hubei Key Laboratory of Soil Environment and Pollution Remediation, Huazhong Agricultural University, Wuhan, 430070, China.
Environ Sci Pollut Res Int. 2018 Nov;25(32):32130-32139. doi: 10.1007/s11356-018-3173-x. Epub 2018 Sep 15.
The bioavailability and potential uptake of heavy metals by crops is fundamentally influenced by the forms of metals in soils. Organic matter plays an important role in controlling the transformation of heavy metal fractionations in soils. However, long-term effects of organic matter on heavy metal speciation remains highly uncertain. In this study, rice straw was introduced to a subtropical Pb-contaminated soil for 2-year period so as to clarify the redistribution of Pb fractions and their correlations with soil properties. By combining sequential extraction and X-ray absorption fine structure spectroscopy, we find that lead is predominantly presented in Fe oxide-bound, surface adsorbed, and residual fractions in the soil. The incorporation of rice straw can effectively reduce the labile species of Pb by promoting the binding of Pb to iron oxides. Furthermore, aging leads to the transfer of considerable amounts of Pb to the association with Fe oxides and this transformation is enhanced by the presence of organic matter. Organic matter input and soil aging tend to shift Pb to amorphous Fe oxides than crystalline Fe oxides. The correlation analysis shows that Fe oxide fractions play vital roles in controlling the forms of Pb in soil. This study presents the first result regarding the long-term effect of organic matter on the redistribution of Pb in naturally polluted soil, which is useful for understanding the fate of Pb and developing remediation strategies for Pb-polluted soils.
重金属在作物中的生物可利用性和潜在吸收主要受到土壤中重金属形态的影响。有机质在控制土壤中重金属形态转化方面起着重要作用。然而，有机质对重金属形态的长期影响仍然高度不确定。在这项研究中，将稻草引入亚热带 Pb 污染土壤中 2 年，以阐明 Pb 形态的重新分布及其与土壤特性的关系。通过结合连续提取和 X 射线吸收精细结构光谱，我们发现 Pb 主要以铁氧化物结合态、表面吸附态和残渣态存在于土壤中。稻草的添加可以通过促进 Pb 与铁氧化物的结合有效地减少 Pb 的可利用态。此外，老化导致大量 Pb 转移到与铁氧化物的结合，而有机质的存在增强了这种转化。有机质的输入和土壤老化往往会使 Pb 向无定形铁氧化物转移而不是向结晶铁氧化物转移。相关分析表明，铁氧化物对控制土壤中 Pb 形态起着重要作用。本研究首次揭示了有机质对自然污染土壤中 Pb 再分布的长期影响，这有助于理解 Pb 的归宿，并为 Pb 污染土壤的修复策略提供依据。
