基于IsoSource模型的沿海流域硝酸盐氮溯源研究

作者	单位
孙健安	宁波市甬环苑环保工程科技有限公司, 浙江宁波 315012
李智渊	中国科学院城市环境研究所, 城市环境与健康重点实验室, 福建厦门 361021
罗纲	中国科学院城市环境研究所, 城市环境与健康重点实验室, 福建厦门 361021
刘懂	中国科学院城市环境研究所, 城市环境与健康重点实验室, 福建厦门 361021
郭兆凤*	中国科学院城市环境研究所, 城市环境与健康重点实验室, 福建厦门 361021

通讯作者:郭兆凤* 中国科学院城市环境研究所, 城市环境与健康重点实验室, 福建厦门 361021

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中文摘要:

过量的硝酸盐氮负荷在导致水质下降的同时,也会对流域生态和人类生产生活造成危害,尤其是在东南沿海地区,硝酸盐氮污染现状堪忧。因此,亟需对沿海流域开展氮污染调查,以阐明氮污染分布格局,识别主要污染来源并量化其贡献,进而保障流域水环境安全,促进沿海城市可持续发展。基于此,以东南地区沿海流域——白溪流域为例,结合2016—2020年长时序水质监测数据和硝酸盐氮氧稳定同位素溯源数据,采用IsoSource质量守恒模型,对氮污染分布格局和污染来源进行定量解析。结果表明:①该流域水体中的总氮主要以溶解性无机氮的形态存在。其中,总氮在2019年呈现整体偏高的态势。硝酸盐氮是干流水车国控断面和支流屠岙胡市控断面的主要氮污染形态。水车断面的总氮浓度范围为1.46~1.83 mg/L,屠岙胡断面的总氮浓度在2.12~2.36 mg/L之间。②流域硝酸盐氮污染主要来自流域内村庄排放的污水和粪便,其贡献率达到了44%;其次是土壤有机氮、大气沉降物、化学合成肥,贡献率分别为25%、16%、15%。③从减少氮污染物排放、提高作物氮吸收率、改进养殖策略和完善污水处理设施角度出发采取相关措施,可以有效缓解流域氮污染。另外,还需要全面落实最严格的水资源管理制度,进一步规范库区内各类水资源开发利用活动,继续做好对库区周边生产经营活动的监督管理,从而减少陆源污染物排放,更好地保护饮用水水源地。

英文摘要:

Nitrate nitrogen excess is known to result in decreased water quality, negative impacts on watershed ecosystems and human production and livelihood. In the southeastern coastal region,the issue of nitrate nitrogen pollution is of particular concern. Thus,a comprehensive investigation of nitrogen pollution in coastal watersheds is urgently needed. Such an investigation would elucidate the distribution pattern of nitrogen pollution,identify the main pollution sources,and quantify the contribution of these sources,all with the goal of protecting the watershed environment and promoting the sustainable development of coastal cities. This study focuses on the Baixi Basin,located in Southeast China,and uses the IsoSource mass conservation model to quantitatively analyze the distribution patterns and source of nitrogen pollution by combining long time series water quality monitoring data and dual isotopes of nitrate (δ¹⁵N and δ¹⁸O) from 2016 to 2020.The results demonstrate that: ① total nitrogen in the watershed primarily exists in the form of dissolved inorganic nitrogen, with an overall high trend observed in 2019. Nitrated nitrogen is identified as the primarily nitrogen pollution pattern in both the Shuiche national controlled section and the Tuaohu municipal control section,which are located in the main stream and tributaries, respectively. The total nitrogen concentration ranges from 1. 46 mg/L to 1. 83 mg/L in the Shuiche section and 2. 12 mg/L to 2. 36 mg/L in the Tuaohu section. ② Nitrate nitrogen pollution in the watershed is mainly caused by the discharge of sewage and manure from villages along the watershed, which contributes 44%, followed by soil organic nitrogen, atmospheric deposition, and chemical synthetic fertilizer at 25%, 16%, and 15%, respectively. ③ Several strategies are proposed for mitigating nitrogen pollution in the watershed, including reducing discharges,improving crop nitrogen uptake rates, improving breeding strategies, and improving sewage treatment facilities. In addition,strict water resource management system should be fully implemented, and all resource development and utilization activities in the reservoir area should be further regulated to reduce the discharge of land-based pollutants and protect drinking water sources.

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