About the Journal
In Memory of Professor Jerzy Radecki
Ownership and Management Statement
Editorial Office
Editorial Board
Scope
Impact Factor
Indexed by
Journal Impact Factor contributing items
Publication Frequency
Revenue Sources & Business Model
Contact
Subscription
Journals Statistics
Current issue
Online first
Instructions for Authors
Copyright & Licensing
Publication Fees
Editorial policies
Publication Policy Overview
Peer Review Policy
Research Ethics and Malpractice Policy
Plagiarism Policy
Conflict of Interest Policy
Open Access Policy
Instructions for Reviewers
Generative AI and AI-Assisted Technologies Policy
Advertising Policy
Direct Marketing & Manuscript Solicitation
Digital Archiving and Preservation Policy
CrossMark, Correction, and Retraction Policy
Complaints and Appeals Procedure
Archive
Publication Fees
Copyright & Licensing
Editorial policies
Publication Policy Overview
Peer Review Policy
Research Ethics and Malpractice Policy
Plagiarism Policy
Conflict of Interest Policy
Open Access Policy
Instructions for Reviewers
Generative AI and AI-Assisted Technologies Policy
Advertising Policy
Direct Marketing & Manuscript Solicitation
Digital Archiving and Preservation Policy
CrossMark, Correction, and Retraction Policy
Complaints and Appeals Procedure
eISSN: 2083-5906
ISSN: 1230-1485
ISSN: 1230-1485
ORIGINAL RESEARCH
Spatial Distribution and Source Apportionment
of Nitrate in Groundwater in a Representative
Agricultural Region of the Southern Piedmont
of the Qinling Mountains, China
1
Xi’an Mineral Resources Survey, China Geological Survey, Xi’an 710100, China
2
Qinling-Loess Plateau Transition Zone Observation and Research Station for Coupling of Soil and Water Elements
and Conservation of Biological Resources, Tongguan 714300, China
Submission date: 2026-03-09
Final revision date: 2026-08-26
Acceptance date: 2026-08-27
Online publication date: 2026-11-03
Corresponding author
Wenqiang Gong
Xi'an Mineral Resources Survey, China Geological Survey, Chang'an District, Xi'an City, Shaanxi Province, C, 710100, Xi'an, China
Xi'an Mineral Resources Survey, China Geological Survey, Chang'an District, Xi'an City, Shaanxi Province, C, 710100, Xi'an, China
KEYWORDS
TOPICS
ABSTRACT
As a critical ecological barrier and core water conservation zone in China, the southern slope of the
Qinling Mountains plays a pivotal role in safeguarding regional ecological security and ensuring a safe
drinking water supply, largely mediated by groundwater quality. However, systematic investigations
into nitrate contamination in this region remain limited, and the dominant sources as well as
hydrogeochemical migration pathways of nitrate are still poorly constrained. To address these knowledge
gaps, this study targets representative watersheds on the southern slope of the Qinling Mountains, with
an emphasis on characterizing the spatial – temporal distribution patterns and identifying the primary
sources of groundwater nitrate. A multi-gradient monitoring network was established along the Han
River and its tributaries, supporting seasonal sampling across both dry and wet periods. Coupled
with δ15N-δ18O dual-isotope tracing and comprehensive regional environmental background surveys,
we quantitatively assessed the spatial heterogeneity, temporal dynamics, and source apportionment
of nitrate in groundwater. Results reveal pronounced spatial variability: mean nitrate concentrations
decrease downstream, and levels adjacent to the main stem are consistently lower than those in tributary
zones. Furthermore, the spatial distribution of nitrate closely parallels the regional groundwater flow
direction. Vertically, soil nitrate concentrations decline with depth overall, yet exhibit anomalous
enrichment at a depth of ~1 m ‒ indicating that nitrate leaching has penetrated to at least this depth.
Source apportionment indicates that soil nitrogen, livestock and poultry manure, and domestic sewage
collectively account for the majority of nitrate inputs to groundwater. This study provides foundational
observational data on groundwater nitrogen cycling in mountain – basin transitional zones, thereby
strengthening the scientific basis for groundwater protection and ecosystem management in the region. It also advances theoretical understanding of nitrogen biogeochemistry in complex terrain and supports
the development of targeted, evidence-based groundwater pollution mitigation strategies.
CONFLICT OF INTEREST
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
REFERENCES (54)
1.
BOURAOUI F., UDIAS A., VIGIAK O., GRIZZETTI B. 30 years of Nitrates Directive in a changing climate: Environmental and policy impacts on nutrient pollution of French rivers. Journal of Hydrology: Regional Studies. 65, 103445, 2026.
2.
ALASSANE ZAKARI A., KPEGLI K. A. R., GNAZOU D.-T. M., ALASSANE A., GUIDAH CHABI B., LAWSON F. M. A., YALO N., MAMA D., BOUKARI M. Groundwater hydrochemistry and identification of nitrate pollution sources in the Ouémé Delta (Southern-Benin) using dual isotopes (15N-NO3 and 18O-NO3) and a Bayesian isotope mixing model. Case Studies in Chemical and Environmental Engineering. 13, 101303, 2026.
3.
TONG H., GAO R., YUE C., XIE L., DUAN L., ZHU Y., WANG G. Hydrochemical evolution and nitrate sources, migration, and transformation in surface water and groundwater of a typical tributary of the Yellow River. Journal of Environmental Management. 390, 126218, 2025.
4.
BORAH P., BORAH G., MALAKAR A. Mitigating nitrate contamination in groundwater: A comprehensive review of in-situ approaches. Groundwater for Sustainable Development. 28, 101406, 2025.
5.
LI P., WU J., HE X., WANG Y., REN X., LI L. Groundwater Nitrate Pollution and Health Risks Under Land Use Changes. Springer Nature Switzerland, Cham, 2026.
6.
SOULA R., CHEBIL A., CETIN M., MAJDOUB R. Spatial analysis and geostatistical characterization of nitrate pollution in Mahdia's shallow aquifers. Environmental Science and Pollution Research. 32 (27), 16380, 2025.
7.
NAKAGAWA K., AMANO H., SHINKAI F., WAKASA A., BERNDTSSON R. Integrated approach to investigate groundwater nitrate nitrogen pollution and remediation simulation in Shimabara Peninsula, Nagasaki, Japan. Environmental Earth Sciences. 84 (10), 256, 2025.
8.
BIDDAU R., DORE E., DA PELO S., LORRAI M., BOTTI P., TESTA M., CIDU R. Geochemistry, stable isotopes and statistic tools to estimate threshold and source of nitrate in groundwater (Sardinia, Italy). Water Research. 232, 119663, 2023.
9.
XUE Y., ZHANG Y., WANG H., ZHANG L., LI H. Seawater intrusion and nitrate pollution in coastal fishery areas: An integrated hydrogeological, hydrochemical, and isotopic approach. Marine Environmental Research. 213, 107668, 2026.
10.
LIU Y., QIAN H., GAO Y., LI S., SHI X., CAO Z., LONG Q., HE Y., MA Y., WU P., SHEN Y. Identifying nitrate pollution of groundwater based on aquifer vulnerability and surface nitrogen loads in the Northern Foot of the Qinling Mountains, China. Journal of Hazardous Materials. 495, 138939, 2025.
11.
CAO S., YANG G., ZHOU J., LIU J., LIU C., LI J., LI Y. Nitrate pollution sources and associated biogeochemical mechanisms in coastal groundwater affected by seawater intrusion using multiple isotopes and source apportionment models. Marine Pollution Bulletin. 232, 120059, 2026. 9
12.
TIAN P., QIAN H., LI S., SHI X., LI K., LIU Y., GAO Y., CAO Z., WU P., MA Y. Distribution, source apportionment, and non-carcinogenic health risk assessment of nitrate pollution in surface and groundwater of the Yi River Basin, China. Journal of Hydrology: Regional Studies. 64, 103237, 2026.
13.
HUANG S., GUO J., XIE Y., BIAN R., WANG N., QI W., LIU H. Distribution, sources, and potential health risks of fluoride, total iodine, and nitrate in rural drinking water sources of North and East China. Science of The Total Environment. 898, 165561, 2023.
14.
SAN A., KHANT N. A., MOON J., KIM H. Groundwater nitrate pollution in Myanmar and policy implications for sustainable water management. Hydrogeology Journal. 34 (3), 749, 2026.
15.
ZHANG Q., XU P., QIAN H., WEI A., CAO K. Nitrate pollution mechanisms and health risk assessment of shallow groundwater in a millennium-cultivated region of China. Physics and Chemistry of the Earth, Parts A/B/C. 143, 104363, 2026.
16.
WANG K., ZHAO W., GUO J., YANG L., LI S., DAI J. Spatiotemporal variations in groundwater nitrate and its sources regulated by external inputs and soil profile characteristics in an agricultural basin. Journal of Hazardous Materials. 500, 140571, 2025.
17.
CHAI G., YANG F., LIAO H., JIA D., FENG W., HO C., LIU D., CHEN S., LIU J., YU H. Coupling of spectroscopy and nitrogen-oxygen isotopes unveils the mechanisms of dissolved organic matter and nitrate pollution in lakes within the agro-pastoral transition zone. Journal of Environmental Sciences. 168, 371, 2026.
18.
CHEN Q., WANG C., CHEN A., CUI R., HU W., FU B., JIANG C., CHEN X., ZHANG D. Source apportionment and uncertainty assessment of nitrate and phosphate pollution in shallow groundwater in agricultural watersheds based on multi-isotope methods. Groundwater for Sustainable Development. 32, 101561, 2026.
19.
WANG H., ISHII S. Bioremediation of agricultural nitrate pollution - challenges and opportunities. Water Research X. 29, 100410, 2025.
20.
SI W., ZHOU H., XU J., XIE Z., ZHANG M., LIU G., WANG C. Water transformations and nitrate pollution sources in typical agricultural watershed of China during the Dry Season. Journal of Environmental Sciences. 169, 137, 2026.
21.
CHEN R., WANG Y., YANG S., WANG Y., ZHI W. Source apportionment of nitrate pollution in the reservoir basins based on dual isotopes of nitrogen and oxygen. Journal of Contaminant Hydrology. 281, 104980, 2026.
22.
XU Z., HU B. X., DAVIS H., CAO J. Simulating long term nitrate-N contamination processes in the Woodville Karst Plain using CFPv2 with UMT3D. Journal of Hydrology. 524, 72, 2015.
23.
PAL S. C., BISWAS T., JAYDHAR A. K., RUIDAS D., SAHA A., CHOWDHURI I., MANDAL S., ISLAM A., ISLAM A. R. M. T., PANDE C. B., ALAM E., ISLAM M. K. Source identification and potential health risks from elevated groundwater nitrate contamination in Sundarbans coastal aquifers, India. Scientific Reports. 14 (1), 4153, 2024.
24.
LIU X., HAN Z., LI Q., WU P. Quantitative identification of nitrate pollution sources in karst water in carbonate basins combined with stable isotope tracer techniques. Ecohydrology & Hydrobiology. 25 (3), 573, 2025.
25.
MONDAL M., SEN S., MUKHERJEE A., DAS K. Lateral and vertical solute transport controlling groundwater pollution in the Sundarbans: Insights from nitrate concentration and stable isotopic signatures. Science of The Total Environment. 1048, 182043, 2026.
26.
NING J., LI P., WU J., YUAN Z., XU F., ZHENG L. Source apportionment of groundwater nitrate pollution in irrigation districts along the Jing River, Guanzhong Basin: Insights from hydrochemistry, isotopes, and the MixSIAR model. Journal of Environmental Chemical Engineering. 13 (3), 116231, 2025.
27.
CHEN W., HU L., LI J., LIN X., YANG X. Spatiotemporal heterogeneity, source apportionment, and transformation-driven partitioned control of nitrate pollution in urban river network: Isotopic and Bayesian insights from the Liuxi-Baini River Basin. Journal of Environmental Chemical Engineering. 14 (2), 121552, 2026.
28.
ZHENG J., GUO X., CAI Y., LIU J., WANG D., GAO X., TAN B. Source apportionment and health risks of nitrate pollution in shallow groundwater in the agricultural Northern Xiaoxing' an Mountains region of China. Journal of Hydrology: Regional Studies. 59, 102394, 2025.
29.
ZHANG Y., XIE Z., LIU W., HUANG J., CHEN S., ZHANG X., YANG C., LI J., KANG W., WANG Y. Source identification and health risk assessment of urban groundwater nitrate contamination in Chongqing, southwestern China. Journal of Hydrology: Regional Studies. 62, 102792, 2025.
30.
UDESHANI C., YUE F. J., GONG Y. Q., LI S. L., CHANDRAJITH R. Sources and dynamics of nitrate in groundwater in a crystalline terrain of tropical Sri Lanka based on a dual isotope approach. Water Research. 282, 123914, 2025.
31.
KOHL D. H., SHEARER G. B., COMMONER B. Fertilizer Nitrogen: Contribution to Nitrate in Surface Water in a Corn Belt Watershed. Science. 174 (4016), 1331, 1971.
32.
VOGEL J. C., TALMA A. S., HEATON T. H. E. Gaseous nitrogen as evidence for denitrification in groundwater. Journal of Hydrology. 50, 191, 1981.
33.
MCMAHON P. B., BöHLKE J. K. Denitrification and mixing in a stream-aquifer system: effects on nitrate loading to surface water. Journal of Hydrology. 186 (1-4), 105, 1996.
34.
DENG Q., WU X., ZHANG W., LI C., ZHANG L., TENG Y., ZHANG Y., LI G. Characteristics and source analysis of nitrate pollution of karst groundwater in the Xiaoli area of the lower Yellow River Basin. Applied Water Science. 16 (7), 213, 2026.
35.
SAMBORSKA-GOIK K., WASSENAAR L.I. Reimagining the Kendall plot: using δ15N and δ18O of nitrate and advanced machine learning to improve N pollutant source classification. Isotopes in environmental and health studies. 61 (3), 310, 2025.
36.
LONG R., TIAN F., CHEN J. H., ZHOU Y. B., LI X. F., LI Y. T., TANG H. W., CHEN H. G. Source apportionment of nitrate in the Pearl River Estuary using δ15N and δ18O values and isotope mixing model. Marine Pollution Bulletin. 191, 114962, 2023.
37.
XU B., LIN Y., WU Y., WANG Y. Identifying sources and transformations of nitrate in different occurrence environments of carbonate rocks using a coupled isotopic approach (δ15N, δ18O, 87Sr/86Sr) in karst groundwater system, North China. Science of The Total Environment. 912, 169300, 2024.
38.
JI X., SHU L., LI J., ZHAO C., CHEN W., CHEN Z., SHANG X., DAHLGREN R. A., YANG Y., ZHANG M. Tracing nitrate sources and transformations using △17O, δ15N, and δ18O-NO3− in a coastal plain river network of eastern China. Journal of Hydrology. 610, 127829, 2022.
39.
MADRIGAL-SOLÍS H., VADILLO-PÉREZ I., JIMÉNEZ-GAVILÁN P., FONSECA-SÁNCHEZ A., QUESADA-HERNÁNDEZ L., CALDERÓN-SÁNCHEZ H., GÓMEZ-CRUZ A., MURILLO J. H., SALAZAR R. P. A multidisciplinary approach using hydrogeochemistry, δ15NNO3 isotopes, land use, and statistical tools in evaluating nitrate pollution sources and biochemical processes in Costa Rican volcanic aquifers. Science of The Total Environment. 951, 174996, 2024.
40.
ZHANG H., LUO J., WU J., DONG H. Dynamic multiobjective two-stage fuzzy stochastic strategy for optimal water allocation in inter-basin water division under changing environment: A case study of Hanjiang-to-Weihe water division in Shaanxi Province, China. Journal of Cleaner Production. 452, 142175, 2024.
41.
LAI Y., CHENG L., FU C., WU Y., WANG S., HOU Q., LIU P., ZHANG L. Ecohydrological characteristics of a typical small catchment in the Upper Han River Basin: Insights from field measurements and modelling. Journal of Hydrology: Regional Studies. 66, 103558, 2026.
42.
JIANG X., WANG J., LIU X., CHEN S., YI L. Impact of landscape patterns on solute dynamics during hydrological events: A multiscale study in the upper Han River basin. Ecological Indicators. 176, 113722, 2025.
43.
HAN C. H., WANG Z. R., TIAN H., NIU Q. S., LIU L., ZHU Y. L., DING L. C., ZHAO L. L., ZHAO H., ZHAO C., WANG F., LI X. B., GONG W. Q. Hydrochemical Characteristics and Genesis of Groundwater in the Hanzhong Basin[J]. Northwestern Geology. 56 (4), 263, 2023 [In Chinese].
44.
KOROM S. F. Natural denitrification in the saturated zone: A review. Water Resources Research. 28 (6), 1657, 1992.
45.
WANG S., CHEN J., ZHANG S., BAI Y., ZHANG X., CHEN D., HU J. Groundwater hydrochemical signatures, nitrate sources, and potential health risks in a typical karst catchment of North China using hydrochemistry and multiple stable isotopes. Environmental Geochemistry and Health. 46 (5), 173, 2024.
46.
YU L., ZHENG T., ZHENG X., HAO Y., YUAN R. Nitrate source apportionment in groundwater using Bayesian isotope mixing model based on nitrogen isotope fractionation. Science of The Total Environment. 718, 137242, 2020.
47.
JIN Z., WANG J., CHEN J., ZHANG R., LI Y., YAOTING L., HE K. Identifying the sources of nitrate in a small watershed using δ15N-δ18O isotopes of nitrate in the Kelan Reservoir, Guangxi, China. Agriculture, Ecosystems & Environment. 297, 106936, 2020.
48.
KRUK M. K., MAYER B., NIGHTINGALE M., LACEBY J. P. Tracing nitrate sources with a combined isotope approach (δ15N-NO3, δ18O-NO3 and δ11B) in a large mixed-use watershed in southern Alberta, Canada. Science of The Total Environment. 703, 135043, 2020.
49.
LORETTE G., SEBILO M., BUQUET D., LASTENNET R., DENIS A., PEYRAUBE N., CHARRIERE V., STUDER J.-C. Tracing sources and fate of nitrate in multilayered karstic hydrogeological catchments using natural stable isotopic composition (δ15N-NO3− and δ18O-NO3−). Application to the Toulon karst system (Dordogne, France). Journal of Hydrology. 610, 127972, 2022.
50.
LI Y., YANG Z., KANG F. X., LIU J. Y., SUN Y. W., HUANG J. B. Isotope analysis on the source of nitrate contamination to groundwater in the Dong'e hydrogeologic unit. Carsologica Sinica. 38 (1), 19, 2019.
51.
WANG S., LI H., KANG T., LI R.X., ZHANG C.Z. Resolving nitrate sources in rivers through dual isotope analysis of δ15N and δ18O. Water, 17 (23), 3370, 2025
52.
SUN X. B., GUO C. L., ZHANG J., SUN J. Q., CUI J., LIU M. H. Spatial-temporal difference between nitrate in groundwater and nitrogen in soil based on geostatistical analysis. Journal of Groundwater Science and Engineering. 11 (1), 37, 2023.
53.
NAKAGAWA K., AMANO H., PERSSON M., BERNDTSSON R. Spatiotemporal variation of nitrate concentrations in soil and groundwater of an intensely polluted agricultural area. Scientific Reports. 11 (1), 2598, 2021.
54.
RUMAN M., DĄBROWSKA D. Evaluation of Water Quality from the Zimny Sztok Spring (Southern Poland)-Preliminary Results. Sustainability. 16 (12), 4962, 2024.
Share
RELATED ARTICLE
| eISSN: | 2083-5906 |
| ISSN: | 1230-1485 |
We process personal data collected when visiting the website. The function of obtaining information about users and their behavior is carried out by voluntarily entered information in forms and saving cookies in end devices. Data, including cookies, are used to provide services, improve the user experience and to analyze the traffic in accordance with the Privacy policy. Data are also collected and processed by Google Analytics tool (more).
You can change cookies settings in your browser. Restricted use of cookies in the browser configuration may affect some functionalities of the website.
You can change cookies settings in your browser. Restricted use of cookies in the browser configuration may affect some functionalities of the website.
