The mineralogical and geochemical characterization of sediments of the Reconquista River allows analyzing the geochemical partition of trace elements in one of the most polluted water courses of Argentina. The low dissolved oxygen and high ammonia contents, together with the high chemical oxygen demand, attest to the poor water quality. Ammonia, Cd and Cu content in surficial water exceeds the maximum guidelines for freshwater in Argentina. The recent sediments of the uppermost bed are enriched in organic matter (OM), sulfur, Zn, Cu and Pb. The enrichment factor is moderate, and the geoaccumulation index (Igeo) for Cu and Pb indicates uncontaminated to moderately contaminated sediments. The positive and significant correlation between As, Cr, Pb and Zn with the iron content suggests that their retention is controlled by the amount of iron oxy (hydr)oxides in the sediments, probably combined with the silt + clay abundance. In comparison with its tributary, the Las Catonas Stream, the Reconquista River, has less OM and trace elements in the sediments and more dissolved trace elements in the interstitial water. We interpret that OM is the main sorbent of the trace element. In the absence of OM, the iron oxy (hydr)oxides and the silt + clay fraction are a less efficient substitute. Consequently, the interstitial waters of the Reconquista River are enriched in these elements. Therefore, minor changes in the environmental conditions may generate significant release of hazardous trace elements from the sediments to the interstitial water and, in turn, to the surficial water of the river. As most of the big cities and the agricultural activities of Argentina are developed on the loessic substrate, the understanding of its interaction with polluted waters is crucial.

Reconquista 河沉积物的矿物学和地球化学特征可以分析阿根廷污染最严重的水道之一中微量元素的地球化学分布。低溶解氧和高氨含量以及高化学需氧量证明水质差。地表水中的氨、镉和铜含量超过了阿根廷淡水的最高标准。最上层床层的近期沉积物富含有机质（OM）、硫、锌、铜和铅。富集因子适中，Cu 和 Pb 的地积聚指数 (Igeo) 表明沉积物未受污染至中度污染。As、Cr、含铁的铅和锌表明它们的保留受沉积物中氧化铁（氢）氧化物的量控制，可能与淤泥 + 粘土的丰度相结合。与其支流 Las Catonas Stream 的 Reconquista 河相比，沉积物中 OM 和微量元素较少，而间隙水中溶解的微量元素较多。我们认为 OM 是微量元素的主要吸附剂。在没有 OM 的情况下，铁氧（氢氧化物）氧化物和淤泥 + 粘土部分是效率较低的替代品。因此，Reconquista 河的间隙水富含这些元素。因此，环境条件的微小变化可能会导致有害微量元素从沉积物中大量释放到间隙水中，进而释放到河流的表层水中。