Even though attenuation processes in the subsurface are known to reduce the impacts of contaminant plumes, their importance is significantly dependent on geological and climatic characteristics, as well as on the leachate quality. The knowledge of attenuation processes linked to different geological formations is therefore fundamental in predicting the impacts of waste disposal areas. Geophysical methods are useful tools for assessing and delineating contaminant plumes, as well as their changes with time, which enables their lower-cost monitoring and association with geological and environmental properties. This paper shows the results of geophysical surveys conducted in the years of 1996, 2005 and 2018 in a waste disposal area located at a Guarani Aquifer recharge zone in Brazil. The objective of this study was to show the evolution of the contamination plume, as well as discuss some possible transport and attenuation processes that the contaminants may undergo in similar areas. Five geophysical sections surveyed within a time span of 20 years were compared, and the information was integrated with physicochemical data from monitoring wells. The results show a horizontal plume spreading, reaching about 200 m from the deposit and about 60 m of depth, 20 years after the ending of disposal activities. The measured resistivities in 2018 are similar to the ones found in 1996 and 2005 in the same surveyed areas, showing that a significant temporal attenuation did not occur. Moreover, samples collected close to anomaly zones and within a distance of 200 m from the deposit presented concentrations of some heavy metals above the screening values according to the Brazilian legislation, showing a metals mobility higher than previously expected, which can be possibly explained by the aquifer's acidic conditions. The estimated plume velocity was about 7 m/yr, a plume deepening was observed until about 50 m and changes in water flow direction and/or diffusion processes made the plume spread to areas previously regarded as upgradient. Therefore, the present paper shows that the rehabilitation of sites neighboring waste disposal sites (less than 200 m from it) did not seem to be feasible through natural attenuation in sandy soils and that the plume spreading is significant in this geological formation. Thus, abandoned disposal areas, constantly considered to be closed after the ending of disposal activities in developing countries, generate plumes which move silently and may reach areas of concern in the future.

尽管已知地下的衰减过程可以减少污染物羽流的影响，但其重要性在很大程度上取决于地质和气候特征以及渗滤液的质量。因此，了解与不同地质构造相关的衰减过程的知识对于预测废物处置区的影响至关重要。地球物理方法是评估和描绘污染物羽流及其随时间变化的有用工具，可实现低成本监测以及与地质和环境属性的关联。本文显示了1996年，2005年和2018年在巴西瓜拉尼含水层补给区的废物处置区进行的地球物理调查的结果。这项研究的目的是显示污染物羽流的演变，并讨论污染物在相似区域可能经历的一些可能的传输和衰减过程。比较了20年内调查的五个地球物理剖面，并将这些信息与来自监测井的理化数据整合在一起。结果表明，在处置活动结束20年后，水平烟羽开始扩散，距沉积物约200 m，深度约60 m。2018年测得的电阻率与1996年和2005年在同一调查区域中测得的电阻率相似，表明未发生明显的时间衰减。此外，在接近异常区域且距矿床200 m的距离内收集的样品显示，根据巴西法律，某些重金属的浓度高于筛查值，表明金属迁移率高于先前的预期，这可能可以用含水层的酸性来解释。条件。估计的羽流速度为约7 m / yr，观察到羽流加深直至约50 m，并且水流方向和/或扩散过程的变化使羽流散布到先前认为是渐进的区域。因此，本文表明，通过自然减缓沙质土壤来恢复废物处理场附近的场址（距该场不到200 m）似乎是不可行的，并且在这种地质构造中烟羽的扩散非常重要。从而，