分类： 环境科学技术及资源科学技术 >> 环境科学技术基础学科 提交时间： 2023-12-20 合作期刊: 《干旱区科学》
摘要： Globally, groundwater contamination by nitrate is one of the most widespread environmental problems, particularly in arid and semiarid areas, which are characterized by low amounts of rainfall and groundwater recharge. The stable isotope composition of groundwater (2H-H2O and 18O-H2O) and dissolved nitrate (15N-NO3 and 18O-NO3) and factor analysis (FA) were applied to explore groundwater provenance, pollution, and chemistry evolution in the northwestern part of the Amman-Al Zarqa Basin, Jordan. In this study, we collected 23 samples from the Lower Ajloun aquifer in 2021, including 1 sample from a groundwater well and 22 samples from springs. These samples were tested for electrical conductivity, total dissolved solids, pH, temperature, dissolved oxygen, the concentration of major ions (Ca2+, Mg2+, Na+, K+, HCO3, Cl, SO42, and NO3), and the stable isotope composition of groundwater and dissolved nitrate. The results revealed that groundwater in the study area is mainly CaMgHCO3 type and can be classified as fresh water, hard water, and very hard water. The range and average concentration of NO3 were 3.5230.8 and 50.9 mg/L, respectively. Approximately 33% of the sampling points showed NO3 levels above the maximum allowable concentration of 50.0 mg/L set by the World Health Organization (WHO) guidelines for drinking water quality. The values of 18O-H2O and 2H-H2O showed that groundwater in the study area is part of the current water cycle, originating in the Mediterranean Sea, with significant evaporation, orographic, and amount effects. The values of the stable isotope composition of NO3 corresponded to 15N-NO3 and 18O-NO3 values produced by the nitrification process of manure or septic waste and soil NH4+. The FA performed on the hydrochemical parameters and isotope data resulted in three main factors, with Factor 1, Factor 2, and Factor 3, accounting for 50%, 21%, and 11% of the total variance, respectively. Factor 1 was considered human-induced factor, named pollution factor, whereas Factor 2, named conservative fingerprint factor, and Factor 3, named hardness factor, were considered natural factors. This study will help local researchers manage groundwater sustainably in the study area and other similar arid and semiarid areas in the world.
分类： 地球科学 >> 地理学 提交时间： 2021-04-30 合作期刊: 《干旱区科学》
摘要： Groundwater forms the main freshwater supply in arid and semi-arid areas, and contamination of this precious resource is complicated by the slow rate of recharge in these areas. Nitrate contamination of groundwater is a global water quality problem, as it entails threat to human health as well as aquatic ecosystems. Source identification of contamination is the cornerstone and a prerequisite for any effective management program of water quality. Stable isotope composition of the dissolved nitrate (δ15N-NO3– and δ18O-NO3–) has been applied to identify NO3– sources and the main transformation processes in the upper aquifer system (A1/2, A4, and B2/A7 aquifers) in the Wadi Shueib catchment area, Jordan. Moreover, the stable isotope compositions of the groundwater (δ2H-H2O and δ18O-H2O) in conjunction with the groundwater hydrochemistry were integrated to investigate the origin and evolution of the groundwater. Results revealed that groundwater in the study area is fresh and hard-very hard water, and mainly a Ca-Mg-Cl type. NO3– concentration was in the range of 7.0–74.0 mg/L with an average of 37.0 mg/L. Most of the samples showed concentration higher than the natural background concentration of NO3– (5.0–10.0 mg/L). The δ2H-H2O and δ18O-H2O values indicated that the groundwater is meteoric, and of Mediterranean origin, with a strong evaporation effect. The δ15N-NO3– values ranged between 6.0‰ and 11.3‰ with an average of 8.7‰, and the δ18O-NO3– values ranged between 1.6‰ and 5.9‰ with an average of 3.4‰. These values are in conformity with the stable isotope composition of nitrate derived the nitrification of wastewater/manure, and soil NH4. Nitrification and denitrification are the main transformation processes affecting nitrogen species. Statistical analysis revealed no significant differences in the δ2H-H2O and δ18O-H2O values, and δ15N-NO3– and δ18O-NO3– values for the three aquifers (A1/2, A4, and B2/A7), indicating that the groundwater of these aquifers has the same origin, and a common source of pollution.
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