Highly acidic phosphogypsum wastes with elevated potential for contaminant leaching are stack-piled near coastal areas worldwide, threatening the adjacent environment. Huge phosphogypsum stacks were disposed directly on the marshes of the Estuary of Huelva (SW Spain) without any impermeable barrier to prevent leaching and thus, contributing to the total contamination of the estuarine environment. According to the previous weathering model, the process water ponded on the surface of the stack, initially used to carry the waste, was thought to be the main washing agent through its infiltration and subsequently the main component of the leachates emerging as the edge outflows. Preliminary restorations have been applied to the site and similar ones are planned for the future considering process water as the only pollution agent. Further investigation to validate the pollution pathway was necessary, thus an evaluation of the relationship between leachates and weathering agents of the stack was carried out using stable isotopes (δ¹⁸O, δ²H, and δ³⁴S) as geochemical tracers. Quantification of the contribution of all possible end-members to the phosphogypsum leachates was also conducted using ternary mixing via the stable isotopic tracers. The results ruled out ponded process water as main vector of edge outflow pollution and unveiled a continuous infiltration of estuarine waters to the stack implying that is subjected to an open weathering system. The isotopic tracers revealed a progressive contribution downstream from fluvial to marine signatures in the composition of the edge outflows, depending on the location of each disposal zone within the different estuarine morphodynamic domains. Thus, the current study suggests that the access of intertidal water inside the phosphogypsum stack, for instance through secondary tidal channels, is the main responsible for the weathering of the waste in depth, underlying the necessity for new, more effective restorations plans.

具有高酸性污染物浸出潜力的高酸性磷石膏废料堆积在世界各地的沿海地区附近，威胁到附近的环境。巨大的磷石膏堆直接放置在韦尔瓦河口（西班牙西南部）的沼泽地上，没有任何不可渗透的屏障，以防止浸出，因此对河口环境造成了完全污染。根据先前的风化模型，堆积在烟囱表面的工艺水最初用于运送废物，被认为是通过其渗透而成为主要的清洗剂，随后渗滤液的主要成分随着边缘的流出而出现。初步修复已应用于该地点，并且计划将工艺用水作为唯一的污染源，计划在未来进行类似的修复。¹⁸ O，δ ² H，和δ ³⁴S）作为地球化学示踪剂。还使用三元混合通过稳定的同位素示踪剂对所有可能的末端成员对磷石膏浸出液的贡献进行了定量。结果排除了污水处理水作为边缘流出污染的主要媒介，并揭示了河口水持续渗透到烟囱中，这意味着要经过开放的风化系统。同位素示踪剂揭示了在河流流出物到海洋特征物下游的边缘流出物组成中的逐步贡献，这取决于不同河口形态动力学域内每个处置区的位置。因此，目前的研究表明，例如通过次潮汐通道，磷石膏堆栈内部的潮间水的进入，