College of Environment, Zhejiang University of Technology, Hangzhou, 310032, China.
Zhejiang Construction Investment Environment Engineering Co., Ltd, Hangzhou, 31000, China.
Environ Monit Assess. 2022 Mar 2;194(3):238. doi: 10.1007/s10661-022-09763-6.
Increased nitrogen (N) from urban stormwater runoff aggravates the deterioration of aquatic ecosystems as urbanisation develops. The sources and transport of nitrate (NO) in urban stormwater runoff were investigated by analysing different forms of N, water isotopes (δD-HO and δO-HO), and NO isotopes (δN-NO and δO-NO) in urban stormwater runoff in a residential area in Hangzhou, China. The results showed that the concentrations of total N and nitrate N in road runoff were higher than those in roof runoff. Moreover, high concentrations of dissolved organic N and particulate N led to high total nitrogen (TN) concentrations in road runoff (mean: 3.76 mg/L). The high δO-NO values (mean: + 60 ± 13.1‰) indicated that atmospheric deposition was the predominant NO source in roof runoff, as confirmed by the Bayesian isotope mixing model (SIAR model), contributing 84-98% to NO. Atmospheric deposition (34-92%) and chemical fertilisers (6.2-54%) were the main NO sources for the road runoff. The proportional contributions from soil and organic N were small in the road runoff and roof runoff. For the initial period, the NO contributions from atmospheric deposition and chemical fertilisers were higher and lower, respectively, than those in the middle and late periods in road runoff during storm events 3 and 4, while an opposite trend of road runoff in storm event 7 highlighted the influence of short antecedent dry weather period. Reducing impervious areas and more effective management of fertiliser application in urban green land areas were essential to minimize the presence of N in urban aquatic ecosystems.
随着城市化的发展，城市雨水径流中增加的氮（N）加剧了水生生态系统的恶化。本研究通过分析杭州市某居民区雨水径流水体中不同形态的 N、水稳定同位素（δD-HO 和 δO-HO）和硝酸盐同位素（δN-NO 和 δO-NO），研究了城市雨水径流中硝酸盐（NO）的来源和迁移。结果表明，道路径流水体中总氮（TN）和硝酸盐氮（NO）浓度高于屋顶径流水体。此外，溶解有机氮（DON）和颗粒态氮（PN）浓度较高导致道路径流水体中 TN 浓度较高（平均值：3.76mg/L）。高 δO-NO 值（平均值：+60±13.1‰）表明大气沉降是屋顶径流中 NO 的主要来源，贝叶斯同位素混合模型（SIAR 模型）证实了这一点，大气沉降对 NO 的贡献率为 84-98%。大气沉降（34-92%）和化肥（6.2-54%）是道路径流水体中 NO 的主要来源。道路和屋顶径流水体中土壤和有机氮的贡献比例较小。在事件 3 和 4 的降雨过程中，道路径流水体中，大气沉降和化肥对 NO 的贡献分别在初期和中期较高，而在后期较低，而事件 7 中道路径流水体的相反趋势则突出了短时间前期干燥天气的影响。减少不透水面积和更有效地管理城市绿地中的施肥是减少城市水生生态系统中 N 存在的关键。
