Abstract High evaporation rates in semi-arid to arid regions result in an increase in salinity that can exacerbate the effect of pollutants in water bodies.This study examines how groundwater drives pollution removal in wetlands, wells and springs within the Chaotic Subbetic Complexes (southern Spain). This evaporitic system, localy with a clear karstic functioning, is characterized by groundwater with a wide range of mineralization. Hydrochemical and multi-isotopic (δ34S, δ18O, δ15N, δ13C and δ2H) techniques were used to understand the geochemical processes leading to pollutant attenuation within the complexes. There, regional groundwater evolve from recharge/transition areas, with low salinity, to the discharge zone. Mineralization of groundwater depends on the dissolution of evaporitic deposits (gypsum, halite) of Keuper age, which increases salinity of the water drained by the outlet springs. δ15N and δ18O values of dissolved nitrate (NO3-) were used to estimate the relative contribution of N sources. NO3- is mainly derived from agricultural inputs (nitrate and urea fertilizers). Long-residence groundwater plays an important role in the biogeochemical evolution. Denitrification is responsible for NO3- removal in transitional zones and discharge springs. This process is promoted by the oxidation of organic carbon, derived from recharge areas and further transported to deeper zones of the aquifer. The findings of this study provide a new understanding of how hydrogeological functioning is connected to pollutant removal in an evaporitic karst system, where the scale of groundwater flows plays a key role in biogeochemical processes.

中文翻译：

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解开西班牙南部蒸发岩溶系统中地下水的功能和硝酸盐衰减：同位素方法

摘要 半干旱到干旱地区的高蒸发率导致盐度增加，从而加剧污染物对水体的影响。本研究探讨地下水如何推动混沌亚贝蒂克复合体（西班牙南部）内湿地、水井和泉水的污染清除。 ）。该蒸发系统具有明显的岩溶作用，以具有广泛矿化作用的地​​下水为特征。水化学和多同位素（δ34S、δ18O、δ15N、δ13C 和 δ2H）技术用于了解导致复合物中污染物衰减的地球化学过程。在那里，区域地下水从低盐度的补给/过渡区演变为排放区。地下水的矿化取决于 Keuper 时代蒸发沉积物（石膏、岩盐）的溶解，这会增加出水泉排出的水的盐度。溶解硝酸盐 (NO3-) 的 δ15N 和 δ18O 值用于估计 N 源的相对贡献。NO3- 主要来自农业投入物（硝酸盐和尿素肥料）。长期滞留地下水在生物地球化学演化中起着重要作用。反硝化作用负责在过渡区和排放弹簧中去除 NO3。这一过程由来自补给区的有机碳的氧化促进，并进一步输送到含水层的更深区域。这项研究的结果提供了对水文地质功能如何与蒸发岩溶系统中污染物去除的关系的新理解，其中地下水流的规模在生物地球化学过程中起着关键作用。