Abstract

Water in Central Asia is a precious resource in the semiarid and arid environments in which people live in the region. Understanding the groundwater quality is important as it is the main factor determining its suitability for drinking and agricultural purposes. This paper presents results of a groundwater hydrochemical assessment in the Herat City by measuring its physicochemical parameters: major cations and anions, pH, total dissolved solids and electrical conductivity. In the light of progressive depletion of groundwater reservoirs and water quality deterioration, an investigation of dissolved major constituents in 27 groundwater samples was performed. The objective was detection of processes for geochemical assessment throughout the area. Herat City has been intensively inhabited during the last decenniums, leading to expansion of the residential and agricultural areas. Besides semi-aridity, rapid social and economic development stimulates greater demand for water, which is gradually fulfilled by groundwater extraction. Groundwater of the study area are characterized by the dominance of Ca + Mg over Na + K. \({\text{HCO}}_{{\text{3}}}^{ - }\), which was found to be the dominant anion, followed by Cl^– and \({\text{SO}}_{4}^{{2 - }}\). The hydrochemical types in the area can be divided into two major groups: the first group includes mixed Ca–Mg–Cl and Ca–Cl types. The second group comprises mixed Ca–Na–HCO₃ and Ca–HCO₃ types. Calcite and aragonite have high SI values, which indicates precipitation as the result of evaporation, whereas dolomite shows an undersaturation state. Most of the samples are within the permissible limit of WHO standards. Interpretation of data suggests that weathering, ion exchange reactions, and evaporation to some extent are the dominant factors that determine the groundwater chemistry in the study area.

中文翻译：

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阿富汗西部赫拉特市的环境水文地球化学特征，控制因素和地下水质量评估

摘要

在该地区人们居住的半干旱和干旱环境中，中亚的水是一种宝贵的资源。了解地下水质量很重要，因为它是决定其是否适合饮用和农业用途的主要因素。本文通过测量赫拉特市的理化参数（主要阳离子和阴离子，pH，总溶解固体和电导率），介绍了赫拉特市地下水水化学评估的结果。鉴于地下水库逐渐枯竭和水质恶化，对27个地下水样品中溶解的主要成分进行了调查。目的是检测整个地区的地球化学评估过程。在过去的十年中，赫拉特市一直有人居住，导致居民和农业领域的扩大。除了半干旱以外，快速的社会和经济发展刺激了对水的更大需求，而地下水的开采逐渐满足了对水的需求。研究区域的地下水以Ca + Mg超过Na + K的优势为特征。\（{\ text {HCO}} _ {{\ text {3}}} ^ {-} \），它是主要的阴离子，其后是Cl ^–和\（{\ text {SO}} _ {4} ^ {{2-}} \）。该地区的水化学类型可以分为两大类：第一类包括混合的Ca–Mg–Cl和Ca–Cl类型。第二组包括混合的Ca–Na–HCO ₃和Ca–HCO ₃类型。方解石和文石具有较高的SI值，这表明由于蒸发而产生沉淀，而白云石则显示出欠饱和状态。大多数样品均在WHO标准的允许范围内。数据解释表明，风化，离子交换反应和蒸发在一定程度上是决定研究区域地下水化学的主要因素。