Lu Hai-Long, Li Ke-Wei, Nkoh Jackson Nkoh, He Xian, Xu Ren-Kou, Qian Wei, Shi Ren-Yong, Hong Zhi-Neng
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Ecotoxicol Environ Saf. 2022 Apr 1;234:113409. doi: 10.1016/j.ecoenv.2022.113409. Epub 2022 Mar 12.
Incubation experiments were conducted to investigate the influencing factors of pH variation in different paddy soils during submerging/draining alternation and the relationship between pH buffering capacity (pHBC) and Cd speciation in ten paddy soils developed from different parent materials (including 8 acid paddy soils and 2 alkaline paddy soils). The soil pHBC and the changes in soil pH, Eh, Fe, Mn, SO and Cd speciation were determined. The results showed that there was a significant positive correlation between cation exchange capacity (CEC) and pHBC of these paddy soils, indicating that soil CEC is a key factor affecting the pHBC of paddy soils. The contribution of Fe(III) oxide reduction to H consumption is far greater than the reduction of Mn(IV)/Mn(III) oxides and SO during the submerging. For example, the contribution of the reduction of manganese oxides, SO and iron oxides to H consumption in the paddy soils from Anthrosol at 15 d submerging was 1.2%, 11.6% and 87.2%, respectively. This confirms that the reduction of Fe(III) oxides plays a leading role in increasing soil pH. Importantly, we noticed that during submerging, soil pH was increased and resulted in the content of available Cd in soils being reduced. This was due to the transformation of Cd to less active forms. Also, there was a significant positive correlation between the change rate of available Cd, the percentage of acid extractable Cd and pH variation. This suggests that the variation in soil pH was responsible for the transformation of Cd speciation. In addition, the change rate of available Cd and the percentage of acid extractable Cd concentration were significantly negatively correlated with soil pHBC. The soil with higher pHBC experienced less pH change, and thus the change rate of available Cd and the percentage of acid extractable Cd concentration were less for the soil. The results of this study can provide a basis for the remediation of Cd-contaminated acidic paddy soils.
开展了培养实验，以研究不同母质发育的10种水稻土（包括8种酸性水稻土和2种碱性水稻土）在淹水/排水交替过程中pH变化的影响因素以及pH缓冲容量（pHBC）与Cd形态之间的关系。测定了土壤pHBC以及土壤pH、Eh、Fe、Mn、SO和Cd形态的变化。结果表明，这些水稻土的阳离子交换量（CEC）与pHBC之间存在显著正相关，表明土壤CEC是影响水稻土pHBC的关键因素。淹水过程中，Fe(III)氧化物还原对H消耗的贡献远大于Mn(IV)/Mn(III)氧化物和SO的还原。例如，淹水15 d时，人为土水稻土中锰氧化物、SO和铁氧化物还原对H消耗的贡献分别为1.2%、11.6%和87.2%。这证实了Fe(III)氧化物还原在提高土壤pH方面起主导作用。重要的是，我们注意到淹水期间土壤pH升高，导致土壤中有效Cd含量降低。这是由于Cd向活性较低的形态转化。此外，有效Cd变化率、酸可提取Cd百分比与pH变化之间存在显著正相关。这表明土壤pH变化是Cd形态转化的原因。此外，有效Cd变化率和酸可提取Cd浓度百分比与土壤pHBC显著负相关。pHBC较高的土壤pH变化较小，因此该土壤中有效Cd变化率和酸可提取Cd浓度百分比也较小。本研究结果可为Cd污染酸性水稻土的修复提供依据。
