Quantitative identification of nitrate pollution sources in karst water in carbonate basins combined with stable isotope tracer techniques

• Published in: Ecohydrology & Hydrobiology Vol. 25; no. 3; pp. 573 - 585
• Main Authors: Liu, Xuanrui, Han, Zhiwei, Li, Qinyuan, Wu, Pan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2025
• Subjects: basins; carbonates; groundwater; groundwater contamination; humans; hydrobiology; hydrochemistry; Karst area; karsts; land use; livestock; Nitrate; nitrates; nitrogen; Nitrogen and oxygen isotopes; nonpoint source pollution; poultry manure; rain; rivers; Siar model; soil organic nitrogen; Source analysis; stable isotopes; surface water; wastewater; water supply; watersheds; Siar model; Nitrate; Nitrogen and oxygen isotopes; Source analysis; Karst area
• ISSN: 1642-3593
• DOI: 10.1016/j.ecohyd.2024.09.006

Karst water, as an important source of water supply, is increasingly contaminated with nitrate. Determining the source and transformation of nitrate is key to effectively controlling its diffuse pollution. Defining the sources of nitrate pollution in watersheds plays an important role in the prevention and control of nitrogen pollution in the surface and groundwater and the development and utilization of water bodies. In this study,we conducted sampling in the Gaoping River of Huichuan, Zunyi City, in May (flat-water period), August (abundant-water period), October (flat-water period), and December (dry-water period). We characterized the distribution of nitrate in the surface water and groundwater of the basin using δ15NNO3-, δ18ONO3-, and δ18OH2O isotope tracer techniques and water chemistry analysis methods. The results show that the water chemistry of the study area is mainly influenced by the HCO3Ca type of water and land use. Nitrate contamination in surface water is less affected by human activities and land-use types than groundwater contamination. Surface water pollution is strongly influenced by the amount of rainfall. Based on the SIAR source analysis model,the distribution of NO3- sources was found to be closely related to the land use types. The main sources of nitrate pollution in the water bodies of the Gaoping River Basin can be classified into five categories: chemical fertilizers, atmospheric sedimentation, soil organic nitrogen, livestock, poultry manure, and wastewater. This study provides an important scientific basis for the protection of karst water and the corresponding theoretical support for the control of nitrate pollution in karst areas.