University of Waterloo, Department of Earth and Environmental Sciences, Waterloo, Ontario N2T 0A4, Canada.
Université du Québec à Chicoutimi, Département des Sciences Appliquées, Saguenay, Québec G7H 2B1, Canada; Centre d'études sur les ressources minérales, Groupe de recherche Risque Ressource Eau, Saguenay, Québec G7H 2B1, Canada.
J Contam Hydrol. 2022 Dec;251:104098. doi: 10.1016/j.jconhyd.2022.104098. Epub 2022 Oct 27.
Implementing sustainable groundwater resources management in coastal areas is challenging due to the negative impacts of anthropogenic stressors and various interactions between groundwater and surface water. This study focuses on nitrate contamination and transport via groundwater-surface water exchange in a Mediterranean coastal area (Guerbes-Senhadja region, Algeria) that is heavily affected by anthropogenic activities. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δH, δO, H, δN and δO), is combined with a Bayesian isotope mixing model (MixSIAR) to (i) elucidate the nitrate sources and their apportionments in water systems, and (ii) describe potential interactions between groundwater and surface water. Results from nitrate isotopic composition and the MixSIAR model show that nitrate concentrations mainly originate from sewage and manure sources. Nitrate derived from the sewage is attributed to urban and rural wastewater discharge, whereas nitrate derived from the manure is related to animal manure used to fertilise agricultural areas. High apportionments of nitrate-based atmospheric precipitation are identified in groundwater and surface water; a finding that is specific to this study. The multi-origin stresses combined with evidence of interactions between surface water and groundwater contribute to negatively impacting large parts of the study coastal area. The outcomes of this study are expected to contribute to sustainable management of coastal ecosystems by drawing more attention towards groundwater use and protection. Furthermore, this study may improve scientists' ability to predict the behavior of anthropogenically impacted coastal ecosystems and help decision-makers elsewhere to prepare suitable environmental strategies for other coastal ecosystems currently undergoing an early stage of groundwater resources deterioration.
在沿海地区实施可持续的地下水管理具有挑战性，因为人为压力和地下水与地表水之间的各种相互作用会产生负面影响。本研究聚焦于受人为活动严重影响的地中海沿海地区（阿尔及利亚 Guerbes-Senhadja 地区）的硝酸盐通过地下水-地表水交换的污染和迁移。本研究采用多示踪剂方法，整合水文地球化学和同位素示踪剂（δH、δO、H、δN 和 δO），并结合贝叶斯同位素混合模型（MixSIAR），（i）阐明水系统中硝酸盐的来源及其分配，（ii）描述地下水与地表水之间的潜在相互作用。硝酸盐同位素组成和 MixSIAR 模型的结果表明，硝酸盐浓度主要来源于污水和粪便源。来源于污水的硝酸盐归因于城市和农村污水排放，而来源于粪便的硝酸盐与用于施肥农业区的动物粪便有关。地下水和地表水都有很高的大气降水硝酸盐分配；这是本研究特有的发现。多源性压力加上地表水与地下水之间相互作用的证据，导致研究沿海地区的大部分地区受到负面影响。本研究的结果有望通过提高对地下水利用和保护的重视，为沿海生态系统的可持续管理做出贡献。此外，本研究可以提高科学家预测受人为影响的沿海生态系统行为的能力，并帮助其他地方的决策者为其他目前处于地下水资源恶化初期的沿海生态系统制定合适的环境战略。
