淹水土壤中镉活性变化及其制约机理

近年来,面对全球土壤Cd污染日益严重的现状,国内外许多专家和学者对土壤中Cd的迁移转化进行了大量的探索和研究。但是,由于土壤自身的复杂性以及影响因素的多样性和不确定性,有关淹水土壤中镉(Cd)活性变化及其制约机理的研究常常出现截然不同甚至相反的报道。铁锰氧化物、碳酸盐、固相有机质、硫化物、DOM、阴离子(主要是Cl-和SO42-)和阳离子(如Al3+、Ca2+、Mg2+、Na+等)等繁多的制约因素及其制约机理使得Cd的土壤化学理论复杂化,也给土壤Cd污染的控制和治理带来困难。本文从Cd在土-水界面发生迁移转化的化学过程(吸附与解吸、沉淀与溶解和配位与螯合)入手,总结并阐述了淹水土壤中Cd活性的变化及其制约机理,同时对该领域的研究进行了展望,试图为淹水土壤中Cd活性的深入研究和Cd污染土壤的修复与治理提供参考。

Variation of cadmium activity in flooded soils and its controlling mechanisms

Cadmium contamination of soil has been a world-wide concern in decades. Cadmium activity may vary sharply in submerged soils but the mechanisms so far found underlying the variation have remained conflicting and ambiguous because of the huge variety of the submerged soils, the complexity of their properties and the diversity of the external factors they are exposed. Various factors, such as Fe and Mn oxides, carbonates, particle organic matters, sulfide, DOM, anions (mainly Cl- and SO42-), cations (such as Al3+, Ca2+, Mg2+, Na+, etc.) and so on, and their controlling mechanisms not only perplex the soil chemistry of Cd, but also hamper the control and remediation of Cd polluted soils. At the oxic-anoxic interface of flooded soils, the variation of Cd activity is largely controlled by some chemical processes, such as adsorption-desorption, precipitation-dissolution, complexation and chelation. The paper reviews in detail these processes and mechanisms controlling the variation of Cd activity in flooded soils. At the same time, some important issues and directions are set forth for further research.