Farhat Boutheina, Chrigui Ranya, Rebai Noamen, Sebei Abdelaziz
Faculty of Sciences of Tunis, Department of Geology, Laboratory of Mineral Resources and Environment (LRME), University of Tunis El Manar, 2092 El Manar II, Tunis, Tunisia.
National School of Engineering of Tunis, LR14ES03 Geotechnical Engineering and Georisk Research Laboratory, University of Tunis El Manar, B.P. 37, Le Belvédère 1002, Tunis, Tunisia.
Environ Sci Pollut Res Int. 2023 Jul;30(35):84334-84356. doi: 10.1007/s11356-023-28216-2. Epub 2023 Jun 26.
The availability of good quality groundwater constitutes a major concern in many developing countries. The El Fahs shallow aquifer, northeastern Tunisia, is an important source of water supply for various economic sectors in the agricultural region. The intensive exploitation of this groundwater has led to its quality degradation. In fact, assessment of water quality degradation is very useful in planning the conservation and management practices of water resources in this watershed. This research aims to evaluate the groundwater quality and its suitability for irrigation uses, identify the main processes to assess their chemical composition, and investigate the potential sources of persistent organic pollutants (POPs). The hydrogeochemical investigation is thus conducted by collecting groundwater samples and analyzing their physicochemical characteristics. Polycyclic aromatic hydrocarbons (16 PAHs) and polychlorinated biphenyls (7 PCBs) were determined in groundwaters from nine stations. The sampling took place in July 2020. The relative abundance of ions was Na > Mg > Ca > K for cations and Cl > SO > HCO for anions. The groundwater exhibits two predominant hydrochemical facies: Ca-Mg-Cl/SO and Na-Cl. The relevant recorded pollutant is nitrate, which was generally far above values of pollution thresholds indicating the influence by the intensive agricultural activity. The suitability for irrigation purposes was assessed using several parameters (EC, SAR, %Na, TH, PI, M, and K). As a matter of fact, the results mentioned that the majority of the samples are unsuitable for irrigation uses. An analysis of the organic pollutants indicates that the total PAH and PCB concentrations are above the permissible values. Therefore, a considerable predominance of naphthalene and PCB28 was observed in order to discriminate between pyrolitic and petrogenic PAH sources; low-molecular-weight (LPAH)/high-molecular-weight (HPAH) ratio was calculated. Results showed that PAHs were mainly of petrogenic origin. The results revealed also that the chemical composition of groundwater is influenced by evaporation process, ion exchange, and water-rock interaction during the flow. A high risk of organic contamination has been highlighted linked to anthropogenic activities which have exerted increasing pressure on groundwater quality. The presence of organic pollutants in groundwater is becoming a serious threat to the environment and human health.
优质地下水的可获取性是许多发展中国家的一个主要关切问题。突尼斯东北部的埃尔法斯浅层含水层是农业地区各经济部门重要的供水水源。对该地下水的过度开采导致了其水质恶化。事实上，评估水质恶化情况对于规划该流域水资源的保护和管理措施非常有用。本研究旨在评估地下水质量及其灌溉适用性，确定评估其化学成分的主要过程，并调查持久性有机污染物（POPs）的潜在来源。因此，通过采集地下水样本并分析其理化特性来进行水文地球化学调查。在9个站点的地下水中测定了多环芳烃（16种PAHs）和多氯联苯（7种PCBs）。采样于2020年7月进行。阳离子的离子相对丰度为Na＞Mg＞Ca＞K，阴离子的离子相对丰度为Cl＞SO＞HCO。地下水呈现出两种主要的水化学相：Ca-Mg-Cl/SO和Na-Cl。记录到的相关污染物是硝酸盐，其含量普遍远高于污染阈值，表明受到集约农业活动的影响。使用几个参数（电导率、钠吸附比、钠百分比、总硬度、渗透指数、镁钠比和钾钠比）评估灌溉适用性。事实上，结果表明大多数样本不适合用于灌溉。对有机污染物的分析表明，PAH和PCB的总浓度高于允许值。因此，为了区分热解源和石油源PAH，观察到萘和PCB28占相当大的优势；计算了低分子量（LPAH）/高分子量（HPAH）比值。结果表明，PAHs主要来源于石油。结果还表明，地下水的化学成分受水流过程中的蒸发过程、离子交换和水岩相互作用的影响。已凸显出与人为活动相关的高有机污染风险，这些活动对地下水质量造成了越来越大的压力。地下水中有机污染物的存在正成为对环境和人类健康的严重威胁。
