Zhou Dong-Mei, Wang Yu-Jun, Cang Long, Hao Xiu-Zhen, Luo Xiao-San
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing 210008, China.
Chemosphere. 2004 Dec;57(10):1237-44. doi: 10.1016/j.chemosphere.2004.08.043.
Glyphosate [N-(phosphonomethyl)glycine] (GPS; H3G) is a widely used pesticide throughout the world. It affects metal behaviors in soil-plant system due to its functional groups, which react with metal ions to form metal complexes. Adsorption and cosorption of cadmium and glyphosate on a Wushan soil (WS soil, Anthrosol) and a Zhuanhong soil (ZH soil, Udic Ferrisol) as affect by solution pH were studied by means of batch adsorption experiments. It indicated that the adsorption quantity of Cd or glyphosate was highly relevant to soil characteristics. The WS soil had higher adsorption capacity of Cd than the ZH soil, due to its high organic matter content and cation exchange capacity (CEC). In contrast, the adsorption quantity of glyphosate on the WS soil was less than that on the ZH soil, because the WS soil has lower iron and aluminum oxides content but higher pH than the ZH soil. The herbicide glyphosate affected Cd adsorption on the two soils when they coexisted in a same soil solution, which was attributed to a glyphosate-induced pH-decrease and the corresponding decline in negative surface charges of the soil. Beside that, glyphosate reacted with solution Cd to form the water-soluble complexes that had lower affinity to soil surface in comparison with Cd itself. On the other hand, the presence of Cd in the soil solution also affected the adsorption of glyphosate on the soils. The presence of Cd increased adsorption quantity of glyphosate on the WS and ZH soils, which was resulted from the decrease of equilibrium solution pH caused by Cd2+ exchange with H+ ions of soil surface. In addition to that, glyphosate adsorption possibly takes place on sites where Cd was previously adsorbed and acted as a bridge between the soil and glyphosate.
草甘膦N-(膦酰基甲基)甘氨酸是一种在全球广泛使用的农药。由于其官能团能与金属离子反应形成金属络合物，它会影响土壤-植物系统中的金属行为。通过批量吸附实验研究了镉和草甘膦在巫山土壤（WS土壤，人为土）和砖红土壤（ZH土壤，铁铝土）上的吸附及共吸附情况，以及溶液pH值对其的影响。结果表明，镉或草甘膦的吸附量与土壤特性高度相关。WS土壤由于其较高的有机质含量和阳离子交换量（CEC），对镉的吸附能力比ZH土壤高。相反，草甘膦在WS土壤上的吸附量小于在ZH土壤上的吸附量，这是因为WS土壤的铁铝氧化物含量低于ZH土壤，但其pH值高于ZH土壤。当除草剂草甘膦与镉在同一土壤溶液中共存时，会影响镉在这两种土壤上的吸附，这归因于草甘膦导致的pH值降低以及相应的土壤表面负电荷减少。除此之外，草甘膦与溶液中的镉反应形成水溶性络合物，与镉本身相比，该络合物对土壤表面的亲和力较低。另一方面，土壤溶液中镉的存在也会影响草甘膦在土壤上的吸附。镉的存在增加了草甘膦在WS和ZH土壤上的吸附量，这是由于Cd2+与土壤表面的H+离子交换导致平衡溶液pH值降低所致。此外，草甘膦的吸附可能发生在镉先前吸附的位点上，并在土壤和草甘膦之间起到桥梁作用。
