Nitrogen and oxygen isotope analysis of nitrate-nitrogen pollution sources in a typical urban river
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摘要:
城市河流硝态氮(NO3-N)污染已经成为快速城市化发展中备受关注的水环境问题。以西安市皂河为例,于2021年的5月(旱季)和9月(雨季)采集其河流水体、排口出水和污水处理厂进出水,测定水质参数,并利用氮氧稳定同位素和Iso Source模型解析NO3-N来源。结果表明:5月和9月皂河NO3-N的δ15N分别为−26.43‰~32.29‰和−2.81‰~20.85‰,δ18O分别为−23.42‰~53.02‰和−5.26‰~21.53‰;粪污是皂河NO3-N的主要来源,皂河不同污染源NO3-N来源的平均贡献率,河流水体为粪污>土壤中氮>化肥>大气沉降,排口出水为粪污>土壤中氮>化肥>大气沉降,污水处理厂进水为大气沉降>粪污>土壤中氮>化肥,污水处理厂出水为粪污>土壤中氮>化肥>大气沉降;土壤中氮和粪污合计对皂河流域NO3-N的贡献率大于70%。控制居民生活污水排放、加强管网建设、强化畜禽粪污管理以及加强土地施肥监督等,有利于减轻城市河流NO3-N污染。
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关键词:
- 城市河流 /
- 硝态氮(NO3-N) /
- 水化学 /
- 氮氧同位素 /
- Iso Source模型
Abstract:Nitrate-nitrogen (NO3-N) pollution in urban rivers has become a water environment problem of great concern in the context of rapid urbanization. Taking the Zaohe River in Xi'an City as an example, the river water body, discharge wastewater and inlet and outlet water of wastewater treatment plants were sampled in May (dry season) and September (rainy season) in 2021 to determine the water quality parameters and to resolve their nitrate-nitrogen sources using nitrogen and oxygen stable isotope and Iso Source models. The results showed that δ15N values of nitrate-nitrogen in the Zaohe River ranged from −26.43‰ to 32.29‰ and −2.81‰ to 20.85‰ in May and September, respectively, and δ18O values ranged from −23.42‰ to 53.02‰ and −5.26‰ to 21.53‰, respectively. Manure was the main source of nitrate pollution in the Zaohe River, and the average contribution rate of different nitrate sources in the river was in the order as follows: for river water, manure > soil organic nitrogen > fertilizer > atmospheric deposition; for discharge water, manure > soil organic nitrogen > fertilizer > atmospheric deposition; for sewage treatment plant influent water, atmospheric deposition > manure > soil organic nitrogen > fertilizer; for sewage treatment plant effluent, manure > soil organic nitrogen > fertilizer > atmospheric deposition. The combined contribution of soil organic nitrogen and manure to the Zaohe River watershed was greater than 70%. Therefore, controlling the discharge of residential sewage, strengthening the construction of pipeline networks, enhancing the management of livestock and poultry manure and strengthening the supervision of land fertilization were conducive to reducing the pollution of nitrate-nitrogen in urban rivers.
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Key words:
- urban rivers /
- nitrate-nitrogen /
- water chemistry /
- nitrogen and oxygen isotopes /
- Iso Source model
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表 1 NO3-N不同污染源来源的氮氧同位素特征范围
Table 1. Range of nitrogen and oxygen isotope characteristics of different sources of nitrate-nitrogen pollution
‰ 表 2 皂河不同类型采样点NO3-N来源贡献率分布
Table 2. Distribution of NO3-N source contribution at different types of sampling sites in Zaohe River
% 采样时间 氮来源 河流水体 排口出水 污水处理厂 进水 出水 旱季 大气沉降 平均值 1.67 16.00 52.86 0.67 标准差 1.83 30.51 13.51 0.75 化肥 平均值 7.89 5.40 19.14 5.00 标准差 6.59 3.01 18.57 3.92 土壤中氮 平均值 25.89 25.00 24.00 49.00 标准差 10.98 15.53 11.34 17.24 粪污 平均值 64.56 53.60 4.00 45.33 标准差 13.64 24.32 6.70 20.99 雨季 大气沉降 平均值 1.00 1.83 9.00 0.71 标准差 1.32 1.57 13.87 1.03 化肥 平均值 18.06 11.50 5.00 7.71 标准差 6.42 2.57 1.22 3.33 土壤中氮 平均值 38.00 37.83 22.75 37.00 标准差 14.44 17.05 11.14 21.71 粪污 平均值 42.94 48.83 63.25 54.57 标准差 10.33 17.23 11.90 23.39 -
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