Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires (IGEBA), CONICET- Universidad de Buenos Aires, Ciudad Universitaria Pabellón II 1er Piso, Int. Guiraldes 2160, C1428EHA, Ciudad Autónoma de Buenos Aires, Argentina.
Instituto de Investigación e Ingeniería Ambiental (3iA), Universidad Nacional de San Martín, Campus Miguelete, 25 de Mayo y Francia, San Martín 1650, Buenos Aires, Argentina.
Environ Geochem Health. 2022 Mar;44(3):729-747. doi: 10.1007/s10653-021-00970-7. Epub 2021 May 28.
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.
雷孔基斯塔河沉积物的矿物学和地球化学特征分析了阿根廷污染最严重的水道之一微量元素的地球化学分配。低溶解氧和高氨含量，以及高化学需氧量，证明了水质较差。地表水的氨、Cd 和 Cu 含量超过了阿根廷淡水的最大指导值。最上面一层的最近沉积物富含有机物 (OM)、硫、Zn、Cu 和 Pb。富集因子适中，Cu 和 Pb 的地球累积指数 (Igeo) 表明沉积物无污染到中度污染。As、Cr、Pb 和 Zn 与铁含量之间的正显著相关性表明，它们的保留受沉积物中铁氧（氢）氧化物数量的控制，可能与粉砂+粘土的丰度有关。与支流拉斯卡托纳斯河相比，雷孔基斯塔河的沉积物中 OM 和痕量元素较少，间隙水中溶解的痕量元素较多。我们推断 OM 是痕量元素的主要吸附剂。在没有 OM 的情况下，铁氧（氢）氧化物和粉砂+粘土部分是一种效率较低的替代品。因此，雷孔基斯塔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危险痕量元素从沉积物向间隙水释放，并进而向河流地表水释放。由于阿根廷的大多数大城市和农业活动都是在黄土基质上发展起来的，因此了解其与污染水的相互作用至关重要。
