This region, with intense agricultural and aquaculture activities, serves as a critical source of nitrogen pollution, contributing to the growing contamination of both surface water and groundwater, which ultimately affects the health of Taihu Lake.
Excessive nitrogen inputs, particularly nitrate (NO3−), from anthropogenic activities have significantly altered aquatic ecosystems worldwide, posing risks to both human health and biodiversity. In China, agricultural intensification has led to rising nitrogen levels in water bodies, with non-point source pollution—stemming from fertilizer application, livestock breeding, and aquaculture—being a major contributor. Despite numerous studies, comprehensive understanding of nitrogen's sources, transport, and transformation in complex landscapes like the Taihu Lake Basin remains insufficient. This study, focusing on two representative counties in the region, aims to address these gaps by combining isotopic and hydrochemical data to identify primary nitrogen sources and assess their environmental impacts.
A study (DOI: 10.48130/nc-0025-0011) published in Nitrogen Cycling on 30 December 2025 by Yanhua Wang’s team, Nanjing Normal University, underscores the importance of both surface and groundwater as critical nitrogen transport pathways to Taihu Lake, revealing the significant role of agricultural and aquaculture practices in nitrogen pollution.
This study examined the spatiotemporal variations in nitrogen concentrations across two river networks—Lakeside River Network (LRN) and Tai-ge Canal River Network (TGRN)—during dry, wet, and regular flow seasons. By analyzing surface water and groundwater samples, a multi-tracer approach, including hydrochemical indicators and dual stable isotopes, was applied to identify key nitrogen sources and reveal their transport pathways. Results showed that nitrification, driven by agricultural activities, dominated in LRN during the dry season, while denitrification was more prominent in groundwater. Nitrogen pollution was more severe in groundwater, with concentrations of total nitrogen (TN) and NO3− significantly higher than in surface water. The study found that manure was the primary nitrogen source in both surface water (69%) and groundwater (60%) in agricultural regions, whereas aquaculture effluent was a key contributor in hybridized areas, particularly during the dry season. The N/P ratio was higher in the dry season, potentially aggravating nutrient limitation in Taihu Lake. Using a county-scale nitrogen cascade model, the study revealed that long-term manure return and the expansion of aquaculture and commercial crop cultivation significantly increased nitrogen losses to aquatic systems, particularly in TGRN, where nitrogen discharge rose from 35.6 to 137.3 kg N ha−1. Isotopic data identified five main nitrogen sources: manure, chemical fertilizers, aquaculture effluent, sewage, and atmospheric deposition. The findings underscore the need for targeted nitrogen management strategies in agricultural and aquacultural areas to mitigate nitrogen pollution and protect the water quality of Taihu Lake.
This research highlights the crucial role of both surface water and groundwater as nitrogen transport pathways to Taihu Lake, underlining the need for integrated management strategies to reduce nitrogen pollution. The findings suggest that manure application, aquaculture practices, and fragmented cropland contribute substantially to the nitrogen load in the region. A key implication of this study is the need for coordinated management policies targeting the control of these primary nitrogen sources. The integration of hydrological flow control, pollutant-removal buffer zones, and improved fertilizer practices can help mitigate nitrogen losses.
###
References
DOI
10.48130/nc-0025-0011
Original Souce URL
https://doi.org/10.48130/nc-0025-0011
Funding information
This work was supported by the National Key Research and Development Program of China (Grant No. 2021YFC3201500), the Open Research Fund of Key Laboratory of Drinking Water Source Protection of the Ministry of Ecology and Environment, Chinese Research Academy of Environmental Sciences (Grant No. 2024YYSYKFYB01), the Fundamental Research Funds for the Central Public-interest Scientific Institution (Grant No. 2024YSKY-02), and the Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant No. KYCX24_1830).
About Nitrogen Cycling
Nitrogen Cycling is a multidisciplinary platform for communicating advances in fundamental and applied research on the nitrogen cycle. It is dedicated to serving as an innovative, efficient, and professional platform for researchers in the field of nitrogen cycling worldwide to deliver findings from this rapidly expanding field of science.