Progress and prospects of research on environmental background value of groundwater
DENG Yuan-dong1,2, YE Xue-yan3,4, DU Xin-qiang3,4
1. Key Laboratory of Groundwater Resources and Environment (Jilin University), Ministry of Education, Changchun 130021, China; 2. College of New Energy and Environment, Jilin University, Changchun 130021, China; 3. Guangdong-Hong Kong Joint Laboratory for Water Security, Beijing Normal University, Zhuhai 519087, China; 4. Center for Water Research, Advanced Institute of Natural Sciences, Beijing Normal University, Zhuhai 519087, China
Abstract：The determination of environmental background values for groundwater was recognized as a prerequisite and key step for the scientific identification, evaluation, and prevention of groundwater pollution. In this paper, the development history of groundwater environmental background value research was reviewed both domestically and internationally. Existing calculation methods for groundwater environmental background values were discussed along with their respective advantages and disadvantages. The research paradigm for background value reasonableness validation analysis and cause analysis was systematically summarized. Finally, existing problems in current groundwater environmental background value research were identified, and future development trends were projected. It was observed that inconsistencies in naming and definitions of groundwater environmental background values persisted among scholars worldwide. Although the influence of human activities on groundwater chemical components had been considered, quantitative determination of the "low human activity impact" threshold in conceptual frameworks remained challenging. Methods for determining environmental background values were generally categorized into mathematical-statistical approaches, model-based methodologies, and other alternative techniques. Each method was found to possess distinct advantages and limitations. The combination of hydrochemical analysis with mathematical statistics was demonstrated to emerge as one of the representative integrated approaches for calculating groundwater environmental background values, though methodologies for trace and micro-component analysis were noted to require further development. The reasonableness of environmental background values was typically assessed through comprehensive evaluation of multiple factors including surrounding pollution sources, hydrogeological conditions, lithological characteristics, land use patterns, pollution percentage indices, and stable isotope results. Regional geological settings and hydrogeological conditions were identified as primary controllers of groundwater environmental background values, while biogeochemical processes were determined to dominate micro-enrichment mechanisms. Based on established environmental background values, groundwater pollution levels were effectively evaluated, pollution risk areas were scientifically delineated, and reference thresholds were provided for environmental regulation and remediation targets. Future priorities were emphasized to include the urgent establishment of a global groundwater environmental background value database, enhanced application of existing background value data, and strategic utilization of big data analytics. These measures were proposed to optimize global groundwater resource protection and pollution control strategies under combined pressures of climate change and anthropogenic impacts.
邓远东, 冶雪艳, 杜新强. 地下水环境背景值研究进展及展望[J]. 中国环境科学, 2025, 45(5): 2530-2545.
DENG Yuan-dong, YE Xue-yan, DU Xin-qiang. Progress and prospects of research on environmental background value of groundwater. CHINA ENVIRONMENTAL SCIENCECE, 2025, 45(5): 2530-2545.
[1] Kuang X X, Liu J G, Scanlon B R, et al. The changing nature of groundwater in the global water cycle [J]. Science, 2024,383(6686): adf0630. [2] Tegegne A M, Lohani T K, Eshete A A. Potential risk assessment due to groundwater quality deterioration and quantifying the major influencing factors using geographical detectors in the Gunabay watershed of Ethiopia [J]. Environmental Monitoring and Assessment, 2023,195(6):753. [3] 郭高轩,辛宝东,刘文臣,等.我国地下水环境背景值研究综述[J]. 水文地质工程地质, 2010,37(2):95-98. Guo G X, Xin B D, Liu W C, et al. A review of environmental background values of groundwater in China [J]. Hydrogeological Engineering Geology, 2010,37(2):95-98. [4] Molinari A, Guadagnini L, Marcaccio M, et al. Natural background levels and threshold values of chemical species in three large-scale groundwater bodies in Northern Italy [J]. Science of the Total Environment, 2012,425:9-19. [5] 高燕燕.关中平原地下水化学成分时空演化规律及人体健康风险评价[D]. 西安:长安大学, 2020. Gao Y Y. Spatial and temporal evolution of groundwater chemistry in Guanzhong Plain and human health risk assessment [D]. Xi'an: Chang'an University, 2020. [6] Li J, Shi Z M, Liu M Z, et al. Identifying anthropogenic sources of groundwater contamination by natural background levels and stable isotope application in Pinggu basin, China [J]. Journal of Hydrology, 2021,596:126092. [7] 李晓媛,张翼龙,王丽娟,等.河套盆地地下水环境背景值研究[J]. 干旱区资源与环境, 2020,34(3):180-187. Li X Y, Zhang Y L, Wang L J, et al. Study on the environmental background value of groundwater in the Loop Basin [J]. Arid Zone Resources and Environment, 2020,34(3):180-187. [8] Urresti-E B, Vadillo-P I, Jimenez-G P, et al. Application of stable isotopes Application of stable isotopes (δ34S-SO4, δ18O-SO4, δ15NNO3, δ18O-NO3) to determine natural background and contamination sources in the Guadalhorce River Basin (southern Spain) [J]. Science of the Total Environment, 2015,506:46-57. [9] Beygi M, Jalali M. Background levels of some trace elements in calcareous soils of the Hamedan Province, Iran [J]. Catena, 2018,162: 303-316. [10] Boy-R M, Nolan B T, Mencio A, et al. Regression model for aquifer vulnerability assessment of nitrate pollution in the Osona region (NE Spain) [J]. Journal of Hydrology, 2013,505:150-162. [11] Burgin A J, Hamilton S K. Have we overemphasized the role of denitrification in aquatic ecosystems? A review of nitrate removal pathways [J]. Frontiers in Ecology and the Environment, 2007,5(2): 89-96. [12] Reimann C, Filzmoser P, Garrett R G. Background and threshold: critical comparison of methods of determination [J]. Science of the Total Environment, 2005,346(1-3):1-16. [13] Preziosi E, Parrone D, Del B A, et al. Natural background level assessment in groundwaters: probability plot versus pre-selection method [J]. Journal of Geochemical Exploration, 2014,143:43-53. [14] De C M, Crosta G B, Frattini P. Hydrogeochemical characterization and Natural Background Levels in urbanized areas: Milan Metropolitan area (Northern Italy) [J]. Journal of Hydrology, 2017,547: 455-473. [15] Connor J J, Shacklette H T, Ebens R J. Background geochemistry of some rocks, soils, plants, and vegetables in the conterminous United States [M]. Washington: U.S. Government Printing Office, 1975. [16] Salminen R, Tarvainen T. The problem of defining geochemical baselines. A case study of selected elements and geological materials in Finland [J]. Journal of Geochemical Exploration, 1997,60(1):91-98. [17] EPA. Establishing background levels[R]. Wachington: Office of Soil Waste and Emergency Response, 1995. [18] Directive 2000/60/EC of the European Parliament and of the Council [Z]. [19] Directive 2006/118/EC of the European Parliament and of the Council [Z]. [20] Hinsby K, M.Teresa C, Dahl Mette. European case studies supporting the derivation of natural background levels and groundwater threshold values for the protection of dependent ecosystems and human health [J]. Science of the Total Environment, 2008,401(1-3):1-20. [21] Visser A, Broers H P, Grift B, et al. Demonstrating trend reversal of groundwater quality in relation to time of recharge determined by 3H/3He [J]. Environmental Pollution, 2007,148(3):797-807. [22] Hansen B, Thorling L, Dalgaard T, et al. Trend reversal of nitrate in danish groundwater - a reflection of agricultural practices and nitrogen surpluses since 1950[J]. Environmental Science & Technology, 2011, 45(1):228-234. [23] Edmunds W. Mike. Natural Groundwater Quality [M]. New Jersey: Blackwell Publishing, 2008. [24] The Turkish bylaw on the protection of groundwater against pollution and deterioration [Z]. [25] Commission directive 2014/80/EU [Z]. [26] Parrone D, Ghergo S, Preziosi E. A multi-method approach for the assessment of natural background levels in groundwater [J]. Science of the Total Environment, 2019,659:884- 894. [27] 何纪力,徐光炎,朱惠民,等.江西省土壤环境背景值研究[M]. 北京: 中国环境科学出版社, 2006. He J L, Xu G Y, Zhu H M, et al. Study on background values of soil environment in Jiangxi Province [M]. Beijing: China Environmental Science Press, 2006. [28] 贺秀全.地下水环境背景值研究[J]. 地下水, 1996,16(12):68- 69. He X Q. Research on environmental background values of groundwater [J]. Groundwater, 1996,16(12):68- 69. [29] 谢明武,区祖鉴.第二松花江流域地下水环境背景值检测技术[M]. 北京:地质出版社, 1990. Xie M W, Au Z J. Environmental background value of groundwater in the Second Songhua River Basin [M]. Beijing: Geological Press, 1990. [30] 于文礼.吉林省地下水环境背景值特征及其变异规律[J]. 吉林地质, 1991,(1):38-43. Yu W L. Characteristics of environmental background values of groundwater in Jilin Province and their variability [J]. Jilin Geology, 1991,(1):38-43. [31] 滕继奎.吉林省潜水地球化学分区及背景特征[J]. 吉林地质, 1990, (4):57-61. Teng J K. Geochemical zoning and background characteristics of diving in Jilin Province [J]. Jilin Geology, 1990,(4):57-61. [32] 曾昭华,丁汉文,多超美,等.江西省鄱阳湖地区地下水环境背景形成的控制因素[J]. 水文地质工程地质, 1990,(3):46-48. Zeng Z H, Ding H W, Duo C M, et al. Factors controlling the formation of groundwater environmental background in Poyang Lake area, Jiangxi Province [J]. Hydrogeological Engineering Geology, 1990,(3):46-48. [33] 曾昭华.长江中下游地区地下水中化学元素的背景特征及形成[J]. 地质学报, 1996,(3):262-270. Zeng Z H. Background characteristics and formation of chemical elements in groundwater in the middle and lower reaches of the Yangtze River [J]. Journal of Geology, 1996,(3):262-270. [34] 贺秀全.地下水环境背景值研究中存在的几个问题[J]. 地下水, 1994,(2):22-23. He X Q. Problems in the study of environmental background values for groundwater [J]. Groundwater, 1994,(2):22-23. [35] HJ 610-2016环境影响评价技术导则(地下水环境) [S]. HJ 610-2016 Technical Guidelines for Environmental Impact Assessment (Groundwater Environment) [S]. [36] 地下水环境背景值统计表征技术指南(试行) [S]. Technical Guidelines for the Statistical Characterisation of Environmental Background Values for Groundwater (Trial) [S]. [37] Gao Y Y, Qian H, Huo C C, et al. Assessing natural background levels in shallow groundwater in a large semiarid drainage Basin [J]. Journal of Hydrology, 2020,584:124638. [38] He B N, He J T, Zeng Y, et al. Coupling of multi-hydrochemical and statistical methods for identifying apparent background levels of major components and anthropogenic anomalous activities in shallow groundwater of the Liujiang Basin, China [J]. Science of the Total Environment, 2022,838:155905. [39] HJ 164-2020地下水环境监测技术规范[S]. HJ 164-2020 Technical Specification for Groundwater Environmental Monitoring [S]. [40] HJ 338-2018饮用水水源保护区划分技术规范[S]. HJ 338-2018 Technical specification for the delineation of drinking water source protection zones [S]. [41] 地下水生态环境监管系统数据编码及目录要求(试行) [Z]. Data coding and catalogue requirements for groundwater ecoenvironmental monitoring systems (for trial use) [Z]. [42] 地下水环境状况调查评价工作指南[Z]. Guidelines for the investigation and evaluation of the state of the groundwater environment [Z]. [43] DD2008-01地下水污染地质调查评价规范[S]. DD2008-01 Specification for geological investigation and evaluation of groundwater contamination [S]. [44] Zhou Yuhan, Wu Jianhua, Gao Xingyu, et al. Hydrochemical background levels and threshold values of phreatic groundwater in the greater Xi'an Region, China: Spatiotemporal distribution, influencing factors and implication to water quality management [J]. Exposure and Health, 2022,15:757–771. [45] Efstathiou Constantinos E. Estimation of type I error probability from experimental Dixon's "Q" parameter on testing for outliers within small size data sets [J]. Talanta, 2006,69(5):1068-1071. [46] 齐万秋,周金龙.石河子市地下水环境背景值[J]. 干旱环境监测, 1994,(1):14-16,60. Qi W Q, Zhou J L. Environmental background values of groundwater in Shihezi City [J]. Arid Environment Monitoring, 1994,(1):14-16,60. [47] 樊丽芳,陈植华.地下水环境背景值的确定[J]. 西部探矿工程, 2004, 16(7):90-92. Fan L F, Chen Z H. Determination of environmental background value of groundwater [J]. Western Prospecting Engineering, 2004,16(7):90- 92. [48] 方媛,吴昊,霍晨琛,等.石嘴山市浅层地下水的环境背景值[J]. 环境化学, 2016,35(7):1361-1371. Fang Y, Wu H, Huo C C, et al. Environmental background values of shallow groundwater in Shizuishan City [J]. Environmental Chemistry, 2016,35(7):1361-1371. [49] 霍晨琛,钱会,吴昊.关中盆地潜水环境背景值研究[J]. 南水北调与水利科技, 2016,14(4):99-106,134. Huo C C, Qian H, Wu H. Study on the background value of diving environment in Guanzhong Basin [J]. South-to-North Water Diversion and Water Science and Technology, 2016,14(4):99-106,134. [50] Amiri V, Nakagawa K. Using a linear discriminant analysis (LDA)- based nomenclature system and self-organizing maps (SOM) for spatiotemporal assessment of groundwater quality in a coastal aquifer [J]. Journal of Hydrology, 2021,603:127082. [51] Panno S V, Kelly W R, Martinsek A T, et al. Estimating background and threshold nitrate concentrations using probability graphs [J]. Ground Water, 2006,44(5):697-709. [52] Reimann C, Fabian K, Birke M, et al. GEMAS: Establishing geochemical background and threshold for 53 chemical elements in European agricultural soil [J]. Applied Geochemistry, 2018,88:302- 318. [53] Moreau M, Daughney C. Defining natural baselines for rates of change in New Zealand's ground-water quality: Dealing with incomplete or disparate datasets, accounting for impacted sites, and merging into state of the-environment reporting [J]. Science of the Total Environment, 2021,755:143292. [54] Rahman A, Tiwari K K, Mondal N C. Assessment of hydrochemical backgrounds and threshold values of groundwater in a part of desert area, Rajasthan, India [J]. Environmental Pollution, 2020,266:115150. [55] 邱汉学,黄巧珍.地下水环境背景值及其确定方法[J]. 青岛海洋大学学报, 1994,(A3):16-20. Qiu H X, Huang Q Z. Environmental background value of groundwater and its determination [J]. Journal of Qingdao Ocean University, 1994,(Vol.A3):16-20. [56] Huang G X, Pei L X, Li L P, et al. Natural background levels in groundwater in the Pearl River Delta after the rapid expansion of urbanization: A new pre-selection method [J]. Science of the Total Environment, 2022,813:151890. [57] Yan G L, Yang L G, Hou Q X. Natural background levels and driving factors of aluminum in shallow groundwater of an urbanized delta: Insight from eliminating anthropogenic-impacted groundwaters [J]. Water Environment Research, 2024,96(7):e11076. [58] Griffioen J, Passier H F., Klein J. Comparison of selection methods to deduce natural background levels for groundwater units [J]. Environmental Science & Technology, 2008,42(13):4863-4869. [59] 曹文庚,付宇,南天,等.机器学习在地下水环境背景值与污染风险评价的应用和展望[J]. 地质学报, 2023,97(7):2408-2424. Cao W G, Fu Y, Nantian et al. Application and outlook of machine learning in groundwater environmental background value and pollution risk evaluation [J]. Journal of Geology, 2023,97(7):2408- 2424. [60] 褚宴佳,何宝南,陈珍,等.基于随机森林模型识别浅层地下水TDS异常的方法研究[J]. 地学前缘, 2025,32(2):456-468. Chu Y J, He B N, Chen Z, et al. A method to identify TDS anomalies in shallow groundwater based on random forest model [J]. Geological Frontiers, 2025,32(2):456-468. [61] Afrifa GY, Ansah-Narh T, Doe C, et al. A gamma mixture model-based approach for the estimation of natural background levels of NO3--N in groundwater [J]. Modeling Earth Systems and Environment, 2022,8(4):4975-4983. [62] Kubier A, Hamer K, Pichler T. Cadmium background levels in groundwater in an area dominated by agriculture [J]. Integrated Environmental Assessment and Management, 2020,16(1):103-113. [63] Chidichimo F, De B M, Costabile A, et al. GuEstNBL: The software for the guided estimation of the natural background levels of the aquifers [J]. Water, 2020,12(10):2728. [64] Ducci D, Condesso M M T, Preziosi E, et al. Combining natural background levels (NBLs) assessment with indicator kriging analysis to improve groundwater quality data interpretation and management [J]. Science of the Total Environment, 2016,569:569-584. [65] Dalla L N, Fabbri P, Mason L, et al. Geostatistics as a tool to improve the natural background level definition: An application in groundwater [J]. Science of the Total Environment, 2017,598:330-340. [66] Biddau R, Dore E, Da P S, et al. Geochemistry, stable isotopes and statistic tools to estimate threshold and source of nitrate in groundwater (Sardinia, Italy) [J]. Water Research, 2023,232:119663. [67] 耿婷婷,李颖智,张涛,等.地下水环境背景值研究进展的分析与建议[J]. 环境科学与管理, 2018,43(5):33-35. Geng T T, Li Y Z, Zhang T, et al. Analysis and suggestions on the progress of groundwater environmental background value research [J]. Environmental Science and Management, 2018,43(5):33-35. [68] 袁利娟.燕山山前滦河冲洪积扇地下水硝酸盐污染来源及转化的同位素示踪[D]. 北京:中国科学院研究生院, 2012. Yuan L J. Isotope tracing of nitrate contamination sources and transformation in groundwater of Yanshan pre-mountain Luanhe alluvial fan [D]. Beijing: Graduate School of Chinese Academy of Sciences, 2012. [69] 廖磊,何江涛,彭聪,等.地下水次要组分视背景值研究:以柳江盆地为例[J]. 地学前缘, 2018,25(1):267-275. Liao L, He J T, Peng C, et al. Study on the apparent background values of groundwater minor components:A case study of Liujiang Basin [J]. Geological Frontiers, 2018,25(1):267-275. [70] 廖磊.柳江盆地浅层地下水次要组分和微量组分视背景值研究[D]. 北京:中国地质大学(北京), 2016. Liao L. Study on the apparent background values of minor and trace components of shallow groundwater in Liujiang Basin [D]. Beijing: China University of Geosciences (Beijing), 2016. [71] 曾颖.秦皇岛柳江盆地浅层地下水常规组分背景值研究[D]. 北京:中国地质大学(北京), 2015. Zeng Y. Study on background values of conventional components of shallow groundwater in Liujiang Basin, Qinhuangdao [D]. Beijing: China University of Geosciences (Beijing), 2015. [72] 刘畅,甘圣斌.地下水环境背景值的确定方法探讨[J]. 绿色科技, 2016,(16):132-133. Liu C, Gan S B. Discussion on the method of determining environmental background value of groundwater [J]. Green Technology, 2016,(16):132-133. [73] 张英.珠江三角洲地区地下水环境背景值研究[D]. 北京:中国地质科学院, 2011. Zhang Y. Environmental background values of groundwater in the Pearl River Delta region [D]. Beijing: Chinese Academy of Geological Sciences, 2011. [74] 王林生.珠江三角洲地区地下水环境背景值研究[M]. 广州:广东人民出版社, 2012. Wang L S. Study on environmental background values of groundwater in the Pearl River Delta region [M]. Guangzhou: Guangdong People's Publishing House, 2012. [75] 孙杉,刘为典.天津市第Ⅱ承压含水组某些地下水环境因子背景值及其分布规律[J]. 石家庄经济学院学报, 1987,(3):225-256. Sun S, Liu W D. Background values and distribution patterns of some groundwater environmental factors in the pressurised aquifer group Ⅱ in Tianjin [J]. Journal of Shijiazhuang Economic College, 1987, (3):225-256. [76] 刘慧文,姜纪沂,刘春平,等.新疆伊犁河谷平原区地下水环境背景值研究[J]. 南水北调与水利科技, 2016,14(4):107-111. Liu H W, Jiang J Y, Liu C P. Study on environmental background values of groundwater in the plain area of Ili River Valley, Xinjiang [J]. South-to-North Water Diversion and Water Science and Technology, 2016,14(4):107-111. [77] Hinsby K, Condesso M M T, Dahl M. European case studies supporting the derivation of natural background levels and groundwater threshold values for the protection of dependent ecosystems and human health [J]. Science of the Total Environment, 2008,401(1):1-20. [78] Arianna A, Loris C, Silvia L, et al. Groundwater diffuse pollution in functional urban areas: The need to define anthropogenic diffuse pollution background levels [J]. Science of the Total Environment, 2019,656:1207-1222. [79] Kim K H, Yun S T, Kim H K, et al. Determination of natural backgrounds and thresholds of nitrate in South Korean groundwater using model-based statistical approaches [J]. Journal of Geochemical Exploration, 2015,148:196-205. [80] Urresti E B, Vadillo P I, Jiménez G P, et al. Application of stable isotopes (δ34S-SO4, δ18O-SO4, δ15N-NO3, δ18O-NO3) to determine natural background and contamination sources in the Guadalhorce River Basin (southern Spain) [J]. Science of the Total Environment, 2015,506-507:46-57. [81] Soumya B S, Sekhar M, Riotte J, et al. Characterization of groundwater chemistry under the influence of lithologic and anthropogenic factors along a climatic gradient in Upper Cauvery basin, South India [J]. Environmental Earth Sciences, 2013,69(7): 2311-2335. [82] Huang Y W, Du Y, Ma T, et al. Dissolved organic matter characterization in high and low ammonium groundwater of Dongting Plain, central China [J]. Ecotoxicology and Environmental Safety, 2021,208:111779. [83] Liao R K, Han Y G, Guo Z F. Assessing the impact of soil aggregate size on mineralization of nitrogen in different soils, China [J]. Catena, 2021,203:105358. [84] Garvin J, Buick R, Anbar A D, et al. Isotopic evidence for an aerobic nitrogen cycle in the Latest Archean [J]. Science, 2009,323(5917): 1045-1048. [85] Sahoo S K, Planavsky N J, Jiang G, et al. Oceanic oxygenation events in the anoxic Ediacaran ocean [J]. Geobiology, 2016,14(5):457-468. [86] 曹玉清,胡宽瑢,李振拴.地下水化学动力学与生态环境区划分[M]. 北京:科学出版社, 2009. Cao Y Q, Hu K R, Li Z S. Groundwater chemical dynamics and ecological zoning [M]. Beijing: Science Press, 2009. [87] 邓远东,冶雪艳,吴亚敏,等.松嫩平原西部地下水氟和砷的富集机理与动态变化特征[J]. 中国环境科学, 2023,43(10):5277-5290. Deng Y D, Ye X Y, Wu Y M, et al. Enrichment mechanism and dynamic change characteristics of fluorine and arsenic in groundwater of western Songnen Plain [J]. China Environmental Science, 2023,43(10):5277-5290. [88] Guo H M, Liu C, Yan S, et al. Source, distribution, and geochemical processes of geogenic high chromium groundwater around the world: A critical review [J]. Journal of Hydrology, 2024,638:131480. [89] Liu C, Guo H M, Yan S, et al. Control of paleoclimate and paleoweathering on chromium contents in a non-ultramafic aquifer hosting high chromium groundwater [J]. Environmental Geochemistry and Health, 2024,46(9):316. [90] Zhang H Y, Zhang X J, Liu W B, et al. Impacts of active tectonics on geogenic arsenic enrichment in groundwater in the Hetao Plain, Inner Mongolia [J]. Quaternary Science Reviews, 2022,278:107343. [91] Mukherjee A, Coomar P, Sarkar S, et al. Arsenic and other geogenic contaminants in global groundwater [J]. Nature Reviews Earth & Environment, 2024,5(4):312-328. [92] Rivera A C A, Cardona B A, Badenszki E, et al. Multimethod characterization of geogenic sources of fluoride, arsenic, and uranium in Mexican groundwater [J]. Applied Geochemistry, 2024,175:106184. [93] Shen S, Luo K W, Ma T, et al. Nitrogen burial characteristics of Quaternary sediments and its controls on high ammonium groundwater in the Central Yangtze River Basin [J]. Science of the Total Environment, 2022,842:156659. [94] Du Y, Deng Y M, Li Y P, et al. Paleo-Geomorphology Determines Spatial Variability of Geogenic Ammonium Concentration in Quaternary Aquifers [J]. Environmental Science & Technology, 2023, 57(14):5726-5738. [95] Xiong Y J, Du Y, Liu Z H, et al. Characteristics of dissolved organic matter contribute to Geogenic ammonium enrichment in coastal versus alluvial-lacustrine aquifers [J]. Water Research, 2024,250:121025. [96] Zhao L, Zhang L, Sun Y F, et al. The release of dissolved organic matter and inorganic nitrogen from coal gangue of different geologic ages in North China [J]. Mine Water and the Environment, 2020,39(1): 93-102. [97] Li Y F, Zhang T W, Ellis G S, et al. Depositional environment and organic matter accumulation of Upper Ordovician-Lower Silurian marine shale in the Upper Yangtze Platform, South China [J]. Palaeogeography Palaeoclimatology Palaeoecology, 2017,466:252- 264. [98] Hinkle S R., Böhlke J K., Duff J H, et al. Aquifer-scale controls on the distribution of nitrate and ammonium in ground water near La Pine, Oregon, USA [J]. Journal of Hydrology, 2007,333(2):486-503. [99] Waring S A., Bremner J M. Ammonium Production in Soil under Waterlogged Conditions as an Index of Nitrogen Availability [J]. Nature, 1964,201(4922):951-952. [100] Knoll L, Breuer L, Bach M. Nation-wide estimation of groundwater redox conditions and nitrate concentrations through machine learning [J]. Environmental Research Letters, 2020,15(6):064004. [101] Sun D H, Bloemendal J, Rea D K, et al. Grain-size distribution function of polymodal sediments in hydraulic and aeolian environments, and numerical partitioning of the sedimentary components [J]. Sedimentary Geology, 2002,152(3/4):263-277. [102] Boulter C A., Hopkinson L J, Ineson M G, et al. Provenance and geochemistry of sedimentary components in the Volcano-Sedimentary Complex, Iberian Pyrite Belt: discrimination between the sillsediment-complex and volcanic-pile models [J]. Journal of the Geological Society, 2004,161:103-115. [103] Rieu R, Allen P A, Ploetze M, et al. Climatic cycles during a Neoproterozoic "snowball" glacial epoch [J]. Geology, 2007,35(4): 299-302. [104] Jia J, Bai J H, Gao H F, et al. In situ soil net nitrogen mineralization in coastal salt marshes (Suaeda salsa) with different flooding periods in a Chinese estuary [J]. Ecological Indicators, 2017,73:559-565. [105] Tesoriero A J, Gronberg J A, Juckem P F, et al. Predicting redox-sensitive contaminant concentrations in groundwater using random forest classification [J]. Water Resources Research, 2017, 53(8):7316-7331. [106] Cao W G, Zhang Z, Fu Y, et al. Prediction of arsenic and fluoride in groundwater of the North China Plain using enhanced stacking ensemble learning [J]. Water Research, 2024,259:121848. [107] Du Y, Deng Y M, Ma T, et al. Enrichment of geogenic ammonium in quaternary alluvial–lacustrine aquifer systems: Evidence from carbon isotopes and DOM characteristics [J]. Environmental Science & Technology, 2020,54(10):6104-6114. [108] Du Y, Deng Y M, Liu Z H, et al. Novel insights into dissolved organic matter processing pathways in a coastal confined aquifer system with the highest known concentration of geogenic ammonium [J]. Environmental Science & Technology, 2021,55(21):14676-14688. [109]钟秋娟,肖兴,汪凡,等.鄱阳湖滨湖区浅层地下水镉元素分布特征及成因分析[J]. 上海国土资源, 2017,38(2):46-48. Zhong Q J, Xiao X, Wang F, et al. Distribution characteristics and cause analysis of cadmium in shallow groundwater in the lakeside area of Poyang Lake [J]. Shanghai Land Resources, 2017,38(2):46-48. [110] Ming X X, Li X F, Zhang Q Y, et al. Provenance, chemical weathering, and sedimentary environment of the aquifer sediments: Implication for arsenic enrichment in groundwater [J]. Catena, 2024,239:107915. [111]郭华明,杨素珍,沈照理.富砷地下水研究进展[J]. 地球科学进展, 2007,22(11):1109-1117. Guo H M, Yang S Z, Shen Z L. Progress in the study of arsenic-rich groundwater [J]. Advances in Earth Sciences, 2007,22(11):1109- 1117. [112]丁爱中,杨双喜,张宏达.地下水砷污染分析[J]. 吉林大学学报(地球科学版), 2007,37(2):319-326. Ding A Z, Yang S X, Zhang H D. Analysis of arsenic contamination in groundwater [J]. Journal of Jilin University (Earth Science Edition), 2007,37(2):319-326. [113]朱其顺,许光泉.中国地下水氟污染的现状及研究进展[J]. 环境科学与管理, 2009,(1):42-44,51. Zhu Q S, Xu G Q. Current status and research progress of groundwater fluoride contamination in China [J]. Environmental Science and Management, 2009,(1):42-44,51. [114]吕晓立,郑跃军,刘可,等.兰州不同城镇功能区地下水氟赋存特征及影响因素[J]. 水文地质工程地质, 2024,51(2):215-226. Lv X L, Zheng Y J, Liu K, et al. Characteristics of fluorine in groundwater in different urban functional areas of Lanzhou and the factors affecting it [J]. Hydrogeology and Engineering Geology, 2024,51(2):215-226. [115]陈建平,李靖,谢帅,等.中国地质大数据研究现状[J]. 地质学刊, 2017,41(3):353-366. Chen J P, Li J, Xie S, et al. Current status of geological big data research in China [J]. Journal of Geology, 2017,41(3):353-366. [116]翟明国,杨树锋,陈宁华,等.大数据时代:地质学的挑战与机遇[J]. 中国科学院院刊, 2018,33(8):825-831. Zhai M G, Yang S F, Chen N H, et al. The era of big data: challenges and opportunities for geology [J]. Proceedings of the Chinese Academy of Sciences, 2018,33(8):825-831. [117]周永章,左仁广,刘刚,等.数学地球科学跨越发展的十年:大数据、 人工智能算法正在改变地质学[J]. 矿物岩石地球化学通报, 2021, 40(3):556-573,777. Zhou Y Z, Zuo R G, Liu G. et al. A decade of leapfrogging in mathematical geosciences: big data, artificial intelligence algorithms are changing geology [J]. Bulletin of Mineral and Rock Geochemistry, 2021,40(3):556-573,777. [118] Zhao T J, Wang S, Ouyang C J, et al. Artificial intelligence for geoscience: Progress, challenges, and perspectives [J]. The Innovation, 2024,5(5):100691. [119] van H T C., Jongen H J, Al-Zawaidah H, et al. Where should hydrology go? An early-career perspective on the next IAHS Scientific Decade: 2023–2032[J]. Hydrological Sciences Journal, 2023,68(4):529-541. [120] Huang G X, Song Ji M, Han D Y, et al. Assessing natural background levels of geogenic contaminants in groundwater of an urbanized delta through removal of groundwaters impacted by anthropogenic inputs: New insights into driving factors [J]. Science of the Total Environment, 2023,857:159527. [121] Bijay S, Craswell E. Fertilizers and nitrate pollution of surface and ground water: an increasingly pervasive global problem [J]. SN Applied Sciences, 2021,3(4):518. [122] Avila S C, Junez F H, Gonzalez T J, et al. Spatio-temporal analysis of natural and anthropogenic arsenic sources in groundwater flow systems [J]. International Journal of Environmental Research and Public Health, 2018,15(11):2374.
