Department of Minerals and Groundwater Resources, Faculty of Earth Sciences, Shahid Beheshti University, Evin Ave, Tehran, Iran; Engineering Geology and Hydrogeology, Faculty of Geology and Mines, Kabul Polytechnic University, District 5, Kabul, Afghanistan.
Department of Minerals and Groundwater Resources, Faculty of Earth Sciences, Shahid Beheshti University, Evin Ave, Tehran, Iran.
Sci Total Environ. 2022 Jun 1;823:153749. doi: 10.1016/j.scitotenv.2022.153749. Epub 2022 Feb 9.
The Kabul urban aquifer (Afghanistan), which is the main source of drinking water for Kabul city's inhabitants, is highly vulnerable to anthropogenic pollution. In this study, the geochemistry of major ions (including reactive nitrogen species such as NO, NO-, and NH) and stable isotope ratios (δN-NO, δO-NO, δO-HO, and δH-HO) of surface and groundwater samples from the Kabul Plain were analyzed over two sampling periods (dry and wet seasons). A Bayesian stable isotope mixing model (BSIMM) was also employed to trace potential nitrate sources, transformation processes, and proportional contributions of nitrate sources in the Kabul aquifer. The plotting of δN-NO against δO-NŌ (δN-NO and δO-NO values ranged from +4.8 to +25.4‰ and from -11.7 to +18.6‰, respectively) suggests that NO primarily originated from the nitrification of sewage rather than artificial fertilizer. The plotting of δN-NO versus NO/Cl ratios also supported the assumption that sewage is the dominant nitrate source. The results indicate that denitrification did not influence the NO isotopic composition in the Kabul aquifer. The BSIMM model suggests that nitrate in the dry season originated mainly from sewage (81%), followed by soil organic N (10.5%), and chemical fertilizer (8.5%). In the wet season, sewage (87.5%), soil organic N (6.7%), and chemical fertilizer (5.8%) were the main sources of NO in the Kabul aquifer. Effective land management measures should be taken to improve the sewage collection system in the Kabul Plain.
喀布尔市区含水层（阿富汗）是喀布尔市居民的主要饮用水源，极易受到人为污染。本研究对喀布尔平原地表水和地下水样本中的主要离子（包括活性氮物种如 NO、NO-和 NH）和稳定同位素比值（δN-NO、δO-NO、δO-HO 和 δH-HO）进行了分析，共涉及两个采样期（旱季和雨季）。还采用贝叶斯稳定同位素混合模型（BSIMM）来追踪硝酸盐的潜在来源、转化过程以及硝酸盐在喀布尔含水层中的比例贡献。δN-NO 与 δO-NO 的关系图（δN-NO 和 δO-NO 值分别在+4.8 到+25.4‰和-11.7 到+18.6‰之间）表明，NO 主要来源于污水的硝化作用，而不是人工肥料。δN-NO 与 NO/Cl 比值的关系图也支持了污水是主要硝酸盐来源的假设。结果表明，反硝化作用并未影响喀布尔含水层中 NO 的同位素组成。BSIMM 模型表明，旱季硝酸盐主要来源于污水（81%），其次是土壤有机氮（10.5%）和化肥（8.5%）。在雨季，污水（87.5%）、土壤有机氮（6.7%）和化肥（5.8%）是喀布尔含水层中硝酸盐的主要来源。应采取有效的土地管理措施来改善喀布尔平原的污水收集系统。
