KTH-International Groundwater Arsenic Research Group, Department of Sustainable Development, Environmental Science and Engineering, Teknikringen 10B, SE-100 44 Stockholm, Sweden.
Universidad Nacional de La Pampa (UNLPam), Facultad de Ciencias Exactas y Naturales, Av. Uruguay 151, L6300 Santa Rosa, La Pampa, Argentina.
Sci Total Environ. 2020 May 1;715:136671. doi: 10.1016/j.scitotenv.2020.136671. Epub 2020 Jan 13.
Elevated Arsenic (As) and Fluoride (F) concentrations in groundwater have been studied in the shallow aquifers of northeastern of La Pampa province, in the Chaco-Pampean plain, Argentina. The source of As and co-contaminants is mainly geogenic, from the weathering of volcanic ash and loess (rhyolitic glass) that erupted from the Andean volcanic range. In this study we have assessed the groundwater quality in two semi-arid areas of La Pampa. We have also identified the spatial distribution of As and co-contaminants in groundwater and determined the major factors controlling the mobilization of As in the shallow aquifers. The groundwater samples were circum-neutral to alkaline (7.4 to 9.2), oxidizing (Eh ~0.24 V) and characterized by high salinity (EC = 456-11,400 μS/cm) and Na-HCO water types in recharge areas. Carbonate concretions ("tosca") were abundant in the upper layers of the shallow aquifer. The concentration of total As (5.6 to 535 μg/L) and F (0.5 to 14.2 mg/L) were heterogeneous and exceeded the recommended WHO Guidelines and the Argentine Standards for drinking water. The predominant As species were arsenate As(V) oxyanions, determined by thermodynamic calculations. Arsenic was positively correlated with bicarbonate (HCO), fluoride (F), boron (B) and vanadium (V), but negatively correlated with iron (Fe), aluminium (Al), and manganese (Mn), which were present in low concentrations. The highest amount of As in sediments was from the surface of the dry lake. The mechanisms for As mobilization are associated with multiple factors: geochemical reactions, hydrogeological characteristics of the local aquifer and climatic factors. Desorption of As(V) at high pH, and ion competition for adsorption sites are considered the principal mechanisms for As mobilization in the shallow aquifers. In addition, the long-term consumption of the groundwater could pose a threat for the health of the local community and low cost remediation techniques are required to improve the drinking water quality.
已对阿根廷查科-潘帕斯平原拉潘帕省东北部浅层含水层中地下水的砷（As）和氟（F）浓度升高情况进行了研究。As 和共存污染物的主要来源是地球成因的，源自安第斯火山带喷发的火山灰和黄土（流纹质玻璃）的风化。在这项研究中，我们评估了拉潘帕两个半干旱地区的地下水质量。我们还确定了地下水砷和共存污染物的空间分布，并确定了控制浅层含水层中砷迁移的主要因素。地下水样本呈弱碱性至碱性（7.4 至 9.2），氧化（Eh~0.24 V），在补给区具有高盐度（EC=456-11400 μS/cm）和 Na-HCO 水型的特点。在浅层含水层的上层中，碳酸盐结核（“tosca”）很丰富。总砷（5.6 至 535μg/L）和 F（0.5 至 14.2mg/L）的浓度不均一，超过了世界卫生组织指南和阿根廷饮用水标准。优势砷物种为砷酸盐 As(V)氧阴离子，由热力学计算确定。砷与碳酸氢根（HCO）、氟（F）、硼（B）和钒（V）呈正相关，但与铁（Fe）、铝（Al）和锰（Mn）呈负相关，后三者的浓度较低。沉积物中最高的砷含量来自干涸湖泊的表面。砷的迁移机制与多种因素有关：地球化学反应、当地含水层的水文地质特征和气候因素。高 pH 值下 As(V)的解吸和离子对吸附位点的竞争被认为是浅层含水层中砷迁移的主要机制。此外，长期饮用地下水可能会对当地社区的健康构成威胁，需要采用低成本的修复技术来改善饮用水质量。
