Sappa Giuseppe, Ergul Sibel, Ferranti Flavia
Dipartimento di Ingegneria Civile, Edile ed Ambientale, Sapienza, Università di Roma, Via Eudossiana, 18, 00186 Rome, Italy.
Springerplus. 2014 May 8;3:237. doi: 10.1186/2193-1801-3-237. eCollection 2014.
Contamination of groundwater by naturally occurring arsenic has recently become a disturbing environmental problem in Viterbo area, Central Italy. Arsenic concentrations in most of the public supply networks exceed the maximum allowable limit of 10 μg/l (WHO) for drinking water. The primary purpose of this paper is to obtain a better understanding of the factors contributing to the high levels of As in water supply networks. This study focuses on (a) the determination of basic hydrochemical characteristics of groundwater, (b) the identification of the major sources and processes controlling the As contamination in public supply networks, (c) to find out possible relationships among the As and other trace elements through principal component analysis (PCA). Groundwater samples from public water supply wells and springs were collected and analysed for physico-chemical parameters and trace elements. Springs and well water samples are predominantly of the Na-HCO3, Na -Ca-HCO3 and Ca-HCO3 types and the highest arsenic concentrations were observed in Na-HCO3 type water. Eh-pH diagrams reveal that H2AsO4 (-) and HAsO4 (2-), As(V) arsenate, are the dominating As species highlighting slightly to moderately oxidizing conditions. Geochemical modeling indicates that arsenic-bearing phases were undersaturated in the groundwater, however most of the samples were saturated with respect to Fe (i.e. magnetite, hematite and goethite) and Al (diaspore and boehmite) oxide and hydroxide minerals. Concentrations of As, Li, B, Co, Sr, Mo, U and Se are highly correlated (r > 0.7) with each other, however in some groundwater samples As show also good correlations (r > 0.5) with Fe and Mn elements reflecting the relationships among the trace elements result from different geochemical processes. Evaluation of the principal component (PCA) analysis and geochemical modeling suggest that the occurrence of As and other trace element concentrations in groundwater are probably derived from (i) weathering and/or dissolution of volcanic source aquifer materials and (ii) adsorption/desorption processes on the Fe and Al oxide and hydroxide minerals.
意大利中部维泰博地区，天然存在的砷对地下水的污染已成为一个令人不安的环境问题。大多数公共供水网络中的砷浓度超过了饮用水10微克/升（世界卫生组织标准）的最大允许限值。本文的主要目的是更好地了解导致供水网络中砷含量过高的因素。本研究着重于：（a）测定地下水的基本水化学特征；（b）识别公共供水网络中控制砷污染的主要来源和过程；（c）通过主成分分析（PCA）找出砷与其他微量元素之间可能存在的关系。采集了公共供水井和泉水中的地下水样本，并对其理化参数和微量元素进行了分析。泉水和井水样本主要为Na-HCO3型、Na-Ca-HCO3型和Ca-HCO3型，在Na-HCO3型水中观察到最高的砷浓度。Eh-pH图表明，H2AsO4(-)和HAsO4(2-)，即As(V)砷酸盐，是主要的砷形态，突出显示了弱至中等氧化条件。地球化学模型表明，地下水中含砷相不饱和，但大多数样本相对于铁（即磁铁矿、赤铁矿和针铁矿）以及铝（水铝石和勃姆石）的氧化物和氢氧化物矿物是饱和的。砷、锂、硼、钴、锶、钼、铀和硒的浓度彼此高度相关（r>0.7），然而在一些地下水样本中，砷与铁和锰元素也显示出良好相关性（r>0.5），反映了不同地球化学过程导致的微量元素之间的关系。主成分（PCA）分析和地球化学模型评估表明，地下水中砷和其他微量元素浓度的出现可能源于：（i）火山源含水层物质的风化和/或溶解；（ii）铁和铝的氧化物及氢氧化物矿物上的吸附/解吸过程。
