Anthropogenic impacts on the nitrate pollution in an urban river: Insights from a combination of natural-abundance and paired isotopes. (1st May 2023)

• Record Type: Journal Article
• Authors: Guo, Wenjing; Zhang, Dong; Zhang, Wenshi; Li, Shen; Pan, Ke; Jiang, Hao; Zhang, Quanfa
• Is Part Of: Journal of environmental management. Volume 333(2023)
• Publication Date: 2023-05-01
• Subjects: Urban river -- Nitrate -- Source -- Isotope -- 15N-pairing technique; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2023.117458
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Urban rivers are often characterized by high nitrate (NO3 − ) loadings. High NO3 − loadings cause water quality and ecological damages, which undermines the sustainable development of cities. To date, the drivers of these high NO3 − loadings remain unclear. This study, for the first time, integrated natural-abundance isotopes (δ 15 N/δ 18 O–NO3 − and δD/δ 18 O–H2 O) and 15 N-pairing techniques to comprehensively reveal the anthropogenic impacts on the NO3 − pollution in an urban river. Natural-abundance isotopes suggested that in both the wet and dry seasons, the NO3 − was predominantly from the conservative mixing of different sources, and biological NO3 − removal was minor. The 15 N-pairing experiments supported the natural-abundance isotope data, quantitatively showing that in-soil nitrification was prevailing, while NO3 − removal processes (denitrification, anammox, and dissimilatory NO3 − reduction to ammonium) were weak. A Bayesian isotope-mixing model showed that soil sources (soil organic nitrogen and chemical fertilizer) dominated the NO3 − in the upper reaches, while in the lower reaches, the impermeable riparian zone short-circuited the access of soils to the river. Here, the wastewater treatment plants became a significant source of NO3 − . This study quantitatively revealed the drivers of high NO3 − loadings in an urban river, and generated important clues for effective NO3 − pollution control and remediation in urban rivers. Graphical abstract: Image 1 Highlights: Coupling natural-abundance and paired isotopes for studying NO3 − pollution. Complex processes regulating the high NO3 − levels in an urban river were quantified. NO3 − removal pathways were weak relative to NO3 − production in the basin. WWTP was a significant source of NO3 − . A methodological improvement in the study of N pollution in rivers.