Shujian Li, Reynold Chow, He Su, Fengpeng Han, Zhi Li
{"title":"多种同位素和GIS分析揭示了黄土高原地下水中硝酸盐的来源和驱动因素。","authors":"Shujian Li, Reynold Chow, He Su, Fengpeng Han, Zhi Li","doi":"10.1016/j.envpol.2025.127022","DOIUrl":null,"url":null,"abstract":"<p><p>Groundwater plays a pivotal role in mediating nitrogen transfer to aquatic ecosystems, particularly in arid regions. Water scarcity, coupled with intensive agricultural activities, has placed the groundwater systems under significant pressure from non-point source pollution, underscoring the need for targeted investigation. Focusing on the Chinese Loess Plateau (CLP), we combined dual-isotope analysis (δ<sup>15</sup>N-NO<sub>3</sub><sup>-</sup>, δ<sup>18</sup>O-NO<sub>3</sub><sup>-</sup>) with water isotopes (δD-H<sub>2</sub>O, δ<sup>18</sup>O-H<sub>2</sub>O) and implemented a dual-framework approach to investigate nitrate dynamics. Specifically, we applied the MixSIAR model to quantify nitrate source contributions and employed the Geographical Detector model to identify spatial and seasonal drivers. The results showed that local piston-flow recharge predominates beneath the thick vadose zone. Nitrate concentrations decreased with increasing well depth (0.04 mg/L/m), accompanied by a convergence of nitrate isotopic signatures toward soil organic nitrogen (SN). Nitrate was derived primarily from SN (43 %) and ammonium NH<sub>4</sub><sup>+</sup> fertilizer (NHF) (34 %), underscoring the dominance of agriculture-related sources. Seasonal patterns revealed minor denitrification during the wet season. Spatial analysis identified land use, precipitation, and the normalized difference vegetation index (NDVI) as key factors controlling nitrate variability. Notably, nitrate leaching was strongly driven by precipitation in regions with sparse vegetation cover. These findings demonstrate that, although nitrate transport and transformation in the CLP are governed by its uniquely deep vadose zone and arid hydrogeological conditions, the integrated isotope and spatial framework developed here provides a transferable approach for investigating nitrate dynamics in other vulnerable deep groundwater systems worldwide.</p>","PeriodicalId":311,"journal":{"name":"Environmental Pollution","volume":"384 ","pages":"127022"},"PeriodicalIF":7.3000,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Multiple isotopes and GIS analyses reveal sources and drivers of nitrate in the Loess Plateau's groundwater.\",\"authors\":\"Shujian Li, Reynold Chow, He Su, Fengpeng Han, Zhi Li\",\"doi\":\"10.1016/j.envpol.2025.127022\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p><p>Groundwater plays a pivotal role in mediating nitrogen transfer to aquatic ecosystems, particularly in arid regions. Water scarcity, coupled with intensive agricultural activities, has placed the groundwater systems under significant pressure from non-point source pollution, underscoring the need for targeted investigation. Focusing on the Chinese Loess Plateau (CLP), we combined dual-isotope analysis (δ<sup>15</sup>N-NO<sub>3</sub><sup>-</sup>, δ<sup>18</sup>O-NO<sub>3</sub><sup>-</sup>) with water isotopes (δD-H<sub>2</sub>O, δ<sup>18</sup>O-H<sub>2</sub>O) and implemented a dual-framework approach to investigate nitrate dynamics. Specifically, we applied the MixSIAR model to quantify nitrate source contributions and employed the Geographical Detector model to identify spatial and seasonal drivers. The results showed that local piston-flow recharge predominates beneath the thick vadose zone. Nitrate concentrations decreased with increasing well depth (0.04 mg/L/m), accompanied by a convergence of nitrate isotopic signatures toward soil organic nitrogen (SN). Nitrate was derived primarily from SN (43 %) and ammonium NH<sub>4</sub><sup>+</sup> fertilizer (NHF) (34 %), underscoring the dominance of agriculture-related sources. Seasonal patterns revealed minor denitrification during the wet season. Spatial analysis identified land use, precipitation, and the normalized difference vegetation index (NDVI) as key factors controlling nitrate variability. Notably, nitrate leaching was strongly driven by precipitation in regions with sparse vegetation cover. These findings demonstrate that, although nitrate transport and transformation in the CLP are governed by its uniquely deep vadose zone and arid hydrogeological conditions, the integrated isotope and spatial framework developed here provides a transferable approach for investigating nitrate dynamics in other vulnerable deep groundwater systems worldwide.</p>\",\"PeriodicalId\":311,\"journal\":{\"name\":\"Environmental Pollution\",\"volume\":\"384 \",\"pages\":\"127022\"},\"PeriodicalIF\":7.3000,\"publicationDate\":\"2025-11-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Environmental Pollution\",\"FirstCategoryId\":\"93\",\"ListUrlMain\":\"https://doi.org/10.1016/j.envpol.2025.127022\",\"RegionNum\":2,\"RegionCategory\":\"环境科学与生态学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"2025/8/21 0:00:00\",\"PubModel\":\"Epub\",\"JCR\":\"Q1\",\"JCRName\":\"ENVIRONMENTAL SCIENCES\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Environmental Pollution","FirstCategoryId":"93","ListUrlMain":"https://doi.org/10.1016/j.envpol.2025.127022","RegionNum":2,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/8/21 0:00:00","PubModel":"Epub","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
Multiple isotopes and GIS analyses reveal sources and drivers of nitrate in the Loess Plateau's groundwater.
Groundwater plays a pivotal role in mediating nitrogen transfer to aquatic ecosystems, particularly in arid regions. Water scarcity, coupled with intensive agricultural activities, has placed the groundwater systems under significant pressure from non-point source pollution, underscoring the need for targeted investigation. Focusing on the Chinese Loess Plateau (CLP), we combined dual-isotope analysis (δ15N-NO3-, δ18O-NO3-) with water isotopes (δD-H2O, δ18O-H2O) and implemented a dual-framework approach to investigate nitrate dynamics. Specifically, we applied the MixSIAR model to quantify nitrate source contributions and employed the Geographical Detector model to identify spatial and seasonal drivers. The results showed that local piston-flow recharge predominates beneath the thick vadose zone. Nitrate concentrations decreased with increasing well depth (0.04 mg/L/m), accompanied by a convergence of nitrate isotopic signatures toward soil organic nitrogen (SN). Nitrate was derived primarily from SN (43 %) and ammonium NH4+ fertilizer (NHF) (34 %), underscoring the dominance of agriculture-related sources. Seasonal patterns revealed minor denitrification during the wet season. Spatial analysis identified land use, precipitation, and the normalized difference vegetation index (NDVI) as key factors controlling nitrate variability. Notably, nitrate leaching was strongly driven by precipitation in regions with sparse vegetation cover. These findings demonstrate that, although nitrate transport and transformation in the CLP are governed by its uniquely deep vadose zone and arid hydrogeological conditions, the integrated isotope and spatial framework developed here provides a transferable approach for investigating nitrate dynamics in other vulnerable deep groundwater systems worldwide.
期刊介绍:
Environmental Pollution is an international peer-reviewed journal that publishes high-quality research papers and review articles covering all aspects of environmental pollution and its impacts on ecosystems and human health.
Subject areas include, but are not limited to:
• Sources and occurrences of pollutants that are clearly defined and measured in environmental compartments, food and food-related items, and human bodies;
• Interlinks between contaminant exposure and biological, ecological, and human health effects, including those of climate change;
• Contaminants of emerging concerns (including but not limited to antibiotic resistant microorganisms or genes, microplastics/nanoplastics, electronic wastes, light, and noise) and/or their biological, ecological, or human health effects;
• Laboratory and field studies on the remediation/mitigation of environmental pollution via new techniques and with clear links to biological, ecological, or human health effects;
• Modeling of pollution processes, patterns, or trends that is of clear environmental and/or human health interest;
• New techniques that measure and examine environmental occurrences, transport, behavior, and effects of pollutants within the environment or the laboratory, provided that they can be clearly used to address problems within regional or global environmental compartments.