Politecnico di Milano, Dipartimento di Ingegneria Civile e Ambientale, Piazza L. Da Vinci 32, 20133, Milan, Italy.
Institute of Environmental Assessment and Water Research, CSIC, Jordi Girona 18, 08034, Barcelona, Spain.
Environ Sci Pollut Res Int. 2014 Feb;21(3):1628-1637. doi: 10.1007/s11356-013-2054-6. Epub 2013 Aug 16.
Dissolved arsenic (As) concentrations detected in groundwater bodies of the Emilia-Romagna Region (Italy) exhibit values which are above the regulation limit and could be related to the natural composition of the host porous matrix. To support this hypothesis, we present the results of a geochemical modeling study reproducing the main trends of the dynamics of As, Fe, and Mn concentrations as well as redox potential and pH observed during batch tests performed under alternating redox conditions. The tests were performed on a natural matrix extracted from a deep aquifer located in the Emilia-Romagna Region (Italy). The solid phases implemented in the model were selected from the results of selective sequential extractions performed on the tested matrix. The calibrated model showed that large As concentrations have to be expected in the solution for low crystallinity phases subject to dissolution. The role of Mn oxides on As concentration dynamics appears significant in strongly reducing environments, particularly for large water-solid matrix interaction times. Modeled data evidenced that As is released firstly from the outer surface of Fe oxihydroxides minerals exhibiting large concentrations in water when persistent reducing conditions trigger the dissolution of the crystalline structure of the binding minerals. The presence of organic matter was found to strongly affect pH and redox conditions, thus influencing As mobility.
在意大利艾米利亚-罗马涅地区（意大利）的地下水体中检测到的溶解砷（As）浓度超过了规定的限值，这可能与宿主多孔基质的自然组成有关。为了支持这一假设，我们展示了一项地球化学建模研究的结果，该研究再现了在交替氧化还原条件下进行的批量测试中观察到的 As、Fe 和 Mn 浓度以及氧化还原电位和 pH 的主要动态趋势。测试是在意大利艾米利亚-罗马涅地区（意大利）的一个深层含水层中提取的天然基质上进行的。模型中实施的固相是从对测试基质进行的选择性顺序提取的结果中选择的。经过校准的模型表明，对于低结晶度相，在发生溶解时，溶液中必须预期会有大量的 As 浓度。在强还原环境中，Mn 氧化物对 As 浓度动态的作用似乎很重要，特别是对于大的水-固矩阵相互作用时间。模型数据表明，As 首先从具有大量浓度的水的 Fe 氢氧化物矿物的外表面释放出来，当持续的还原条件触发结合矿物的晶体结构溶解时。发现有机物的存在强烈影响 pH 值和氧化还原条件，从而影响 As 的迁移性。
