CHEMISTRY OF METAL RETENTION BY SOILS - SEVERAL PROCESSES ARE EXPLAINED
CHEMISTRY OF METAL RETENTION BY SOILS - SEVERAL PROCESSES ARE EXPLAINED
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DOI：
10.1021/es00067a001
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发表时间：
1989-09-01
影响因子：
11.4
通讯作者：
EVANS, LJ
中科院分区：
文献类型：
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作者：
EVANS, LJ
几千年来，土壤一直是社会废物的储存库。挖掘出的墓穴为考古学家提供了有关过去文明日常生活的宝贵信息，表明自古以来就有土地处理。然而，近年来，在垃圾填埋场处理城市和工业废物的迅速增加，以及这些垃圾填埋场的渗滤液和污水污泥在土地上的应用，引起了人们对环境污染的关注。此外，金属也通过农业生产直接或通过工业污染物和汽车排放的大气沉淀间接地被添加到土壤中。许多金属与生物分子形成稳定的配合物，它们的存在即使是少量也会对植物和动物有害。然而，金属对植物和动物的相对毒性可能差别很大（见框）；与配体形成稳定配合物的金属往往毒性最大（1,2）。因此，从填埋场浸出的金属可能污染地下水供应，是一个主要的环境问题。这种担忧导致许多工业国家规定了饮用水中钡、镉、铬、铅、汞和银等金属的最大可接受浓度。然而，在陆地表面形成或沉积的土壤和沉积物可以作为容纳这些金属的巨大储藏库。土壤特别重要，因为它们含有表面活性矿物和土壤成分，这些成分参与影响金属保留的反应。土壤或其他表面物质对金属的滞留是近年来许多研究的焦点(4)。人们开发了各种数学模型来预测天然水体中金属的形态，并制定了机制模型来量化矿物和有机土壤成分对金属的保留（5,6）。细粒土壤颗粒表面的化学性质非常活跃；表面位置带负电或正电，或者它们是电中性的。土壤溶液中带相反电荷的金属反离子被吸引到这些带电荷的表面。吸引到这些不同地点的离子的相对比例取决于土壤的酸度或碱度、矿物组成和土壤的含水量
For thousands of years, soil has been the repository of society’s wastes. The excavation of middens, which has provided archaeologists with valuable information on the daily life of past civili-zations, has shown that land disposal has been carried out since antiquity. In recent years, however, the rapid in-crease in the disposal of municipal and industrial wastes in landfill sites, and the application both of leachates from these landfill sites and of sewage sludge to land, is causing much concern about environmental pollution. Moreover, metals also are being addedto soil either directly through agricultural prac-tices or indirectly through the atmo-spheric precipitation of industrial pollutants and automobile emissions. Many metals form stable complexes with biomolecules, and their presence in even small amounts can be detrimental to plants and animals. The relative toxicity of metals to plants and animals, however, can vary greatly (see box); metals that form stable complexes with ligands tendto be the most toxic (1, 2). The possible contamination of groundwater supplies by metals leached from landfill sites, therefore, is a major environmental concern. This concern has led many industrial nations to specify the maximum acceptableconcentra-tions of metals, such as barium, cad-mium, chromium, lead, mercury, and silver in drinking water. The soils and sediments formed or deposited on the land surface can, how-ever, act as vast reservoirs for the con-tainment of these metals. Soils are important particularly because they contain surface-active mineral and hu-mic constituents involved in reactions that affect metal retention. The retention of metals by soil or other surface materials has been a focus of much research in recent years (4). Various mathematical models have been developed to predict the speciation of metals in natural waters, and mecha-nistic modelshave been formulated to quantify the retention of metals by both mineral and organic soil constituents (5, 6).The surfaces of fine-grained soil particles are very active chemically; sur-face sites are negatively or positively charged or they are electrically neutral. Oppositely charged metallic counterions from solutions in soils are attracted to these charged surfaces. The relative proportions of ions attracted to these various sites depends on the degree of acidity or alkalinity of the soil, on its mineralogical composition, and on its