Determining nitrate sources in storm runoff in complex urban environments based on nitrogen and oxygen isotopes

Jiaxun Guo; Ping Zuo; Long Yang; Lachun Wang; Hong Yang

doi:10.1016/j.scitotenv.2022.155680

Determining nitrate sources in storm runoff in complex urban environments based on nitrogen and oxygen isotopes

Sci Total Environ. 2022 Sep 10;838(Pt 1):155680. doi: 10.1016/j.scitotenv.2022.155680. Epub 2022 May 4.

Authors

Jiaxun Guo¹, Ping Zuo², Long Yang², Lachun Wang³, Hong Yang⁴

Affiliations

¹ School of Geography and Ocean Science, Nanjing University, Nanjing, Jiangsu province 210023, China; Center for Water and Ecology, State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
² School of Geography and Ocean Science, Nanjing University, Nanjing, Jiangsu province 210023, China.
³ School of Geography and Ocean Science, Nanjing University, Nanjing, Jiangsu province 210023, China. Electronic address: wang6312@nju.edu.cn.
⁴ Department of Geography and Environmental Science, University of Reading, Reading RG6 6AB, UK. Electronic address: hongyanghy@gmail.com.

PMID: 35525348
DOI: 10.1016/j.scitotenv.2022.155680

Abstract

Urban storm runoff, as the primary transport medium for nutrients entering urban rivers, contributes to urban water contamination. Accurate source identification is critical for controlling water pollution. Although some studies have used nitrate isotopic composition (δ¹⁵N-NO₃^- and δ¹⁸O-NO₃^-) to identify nitrate (NO₃^--N) in urban storm runoff, the relatively low frequency of collecting samples in surface runoff within a single functional area hinders the understanding of spatial variations and dynamic process of NO₃^--N sources over the runoff process. This study investigated the nitrogen (N) concentrations and analyzed dynamic changes of NO₃^--N sources in surface runoff in different urban functional areas, drainage pipeline runoff, and channels during the complete runoff process in Wuxi, east China. The results showed that N concentrations in pipeline runoff and channels were higher than those in surface runoff, indicating that high concentration of N pollutants were accumulated in drainage pipelines. Information of δ¹⁵N-NO₃^- and δ¹⁸O-NO₃^- suggested that the main NO₃^--N source varied between runoff stages. NO₃^--N contribution from atmospheric deposition decreased in the order: surface runoff (57%) > residential pipeline runoff (25%) > channels (14%), while the opposite trend was observed for the contributions from sewage, increasing from 10%, 26% to 39%. In urban storm runoff, more sewage, fertilizers, and soil N were carried into the surface runoff after 30% of cumulative runoff ratio and carried into pipeline runoff in the initial 25% of cumulative runoff ratio in the residential area. As the first attempt to identify nitrate sources over the cumulative runoff in different urban functional areas, this work expands our understanding of the primary nitrate source in urban storm runoff. The findings provide important insights for developing strategies to mitigate non-point source water pollution.

Keywords: Bayesian mixing model; Different functional areas; Nitrate isotopes; Urban storm runoff.

MeSH terms

Bayes Theorem
China
Environmental Monitoring / methods
Nitrates* / analysis
Nitrogen / analysis
Nitrogen Isotopes / analysis
Oxygen Isotopes / analysis
Sewage
Water Pollutants, Chemical* / analysis

Substances

Nitrates
Nitrogen Isotopes
Oxygen Isotopes
Sewage
Water Pollutants, Chemical
Nitrogen