The failure of the tailing dam at the Aznalcóllar mine (SW Spain) in 1998 released ≈ 6 million m3 of pyrite sludge and acidic waters, and caused an enormous environmental disaster in the Agrio and Guadiamar rivers. A small aquifer formed by recent alluvial materials deposited by both rivers was also affected. The mine closed as a result of the spill but a new project for its reopening is currently being developed. The area covered by the spill (≈ 60 km long) was later transformed into a protected green corridor, which connects two important natural reserves. This work describes the effectiveness of the remediation measures taken and analyzes the evolution of water quality in the area since 1980 (almost 20 years before the accident occurred). The contaminant levels in both surface and groundwater showed a sharp decrease the first years after the spill, followed by a subsequent stabilization of pollution levels. Nowadays, pollutant concentrations in surface waters are even lower than those recorded before the spill, due to the cessation of mining and the effectiveness of the remediation. Despite this fast and outstanding improvement, the alluvial aquifer close to the mining zone is still polluted, with acidic pH values in some areas, probably due to the slow movement of groundwater together with the existence of some areas with polluted soils. As this aquifer feeds the streams, some pollutants (e.g. Al, Cd, and Zn) reach the surface waters. Remediation of the polluted soils as well as the alluvial aquifer in this sector is strongly recommended to achieve the complete rehabilitation of the affected area.

中文翻译：

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Aznalcóllar 矿山泄漏（西班牙西南部）后 Agrio 河和 Guadiamar 河的地表和地下水质量演变：经验教训

1998 年 Aznalcóllar 矿（西班牙西南部）尾矿坝的故障释放了约 600 万立方米的黄铁矿污泥和酸性水，并在阿格里奥河和瓜迪亚马尔河造成了巨大的环境灾难。由两条河流最近沉积的冲积物形成的小型含水层也受到影响。该矿因泄漏而关闭，但目前正在开发一个重新开放的新项目。泄漏区域（约 60 公里长）后来转变为受保护的绿色走廊，连接两个重要的自然保护区。这项工作描述了所采取的补救措施的有效性，并分析了自 1980 年以来（事故发生前将近 20 年）该地区水质的演变。地表水和地下水中的污染物水平在泄漏后的头几年急剧下降，随后污染水平趋于稳定。如今，由于采矿业的停止和修复的有效性，地表水中的污染物浓度甚至低于泄漏前记录的浓度。尽管取得了这种快速而显着的改善，但靠近矿区的冲积含水层仍然受到污染，一些地区的 pH 值为酸性，这可能是由于地下水流动缓慢以及一些地区存在土壤污染。由于该含水层为河流供水，一些污染物（例如铝、镉和锌）会到达地表水。