Department of Geology and Geochemistry, Faculty of Science, Autonomous University of Madrid, Campus Cantoblanco, C/Fco. Tomás y Valiente 7, 28049 Madrid, Spain.
Sci Total Environ. 2013 Oct 1;463-464:1049-59. doi: 10.1016/j.scitotenv.2013.06.047. Epub 2013 Jul 24.
Analyses of substratum samples under a landfill were performed to assess the pollution impact of waste over a clay-sand material after nine years of exposure. These samples presented different illite/kaolinite ratios and an acid pH, especially low near the waste/soil contact in a 1-1.5 m soil thickness with low density and despite the basic pH of the collected actual methanogenic leachate. This study has raised the effects of a presumably acid stage in the waste leachate on the substratum final quality of clay and its physical-chemical properties as an attenuation buffer. These effects were the dissolution of carbonate minerals, decrease of dry density, increase of hydraulic conductivity, release of metals and formation of clays with low cationic exchange capacity (CEC) as kaolinite. The large presence of H(+) and Al(OH)(3-x)(x+) depleted the neutralizing capacity of the substratum and occupied exchangeable sites, decreasing therefore the available sites for retaining leachate pollutants, which traveled further than the first-meter depth of the substratum. In order to combat and prevent pollution as well as to preserve the good barrier properties under new landfills it is proposed to select illitic materials better than kaolinitic substratum, to avoid acid landfilling and if not possible to add lime.
对垃圾填埋场下的底土样本进行了分析，以评估在暴露九年后废物对粘土-砂质材料的污染影响。这些样本呈现出不同的伊利石/高岭石比率和酸性 pH 值，尤其是在 1-1.5 米厚的土壤中，靠近废物/土壤接触处，密度较低，尽管收集到的实际产甲烷浸出液的 pH 值为碱性。本研究揭示了废物浸出液中假定的酸性阶段对粘土底土最终质量及其物理化学性质作为衰减缓冲的影响。这些影响包括碳酸盐矿物的溶解、干密度的降低、水力传导性的增加、金属的释放以及形成低阳离子交换能力（CEC）的高岭石粘土。大量的 H(+)和 Al(OH)(3-x)(x+)耗尽了底土的中和能力并占据了可交换位，从而减少了保留浸出液污染物的可用位，这些污染物的迁移深度超过了底土的第一米深度。为了防治污染并保护新填埋场下的良好阻隔性能，建议选择伊利石材料而不是高岭石底土，以避免酸性填埋，如果不可能，则添加石灰。
