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Isotopic Interpretation of Particulate Nitrate in the Metropolitan City of Karachi, Pakistan: Insight into the Oceanic Contribution to NOx.
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2020-06-03 , DOI: 10.1021/acs.est.0c00490
Zheng Zong 1, 2 , Chongguo Tian 1, 2 , Jun Li 3 , Jabir Hussain Syed 4 , Wei Zhang 5 , Yunting Fang 6 , Yifan Jiang 7 , Jawad Nasir 8 , Muhammad Mansha 8 , Syed Hussain Haider Rizvi 8 , Muhammad Shafiq 8 , Suhaib Bin Farhan 8 , Gan Zhang 3
Affiliation  

Nitrogen oxide (NOx) abatement has become the focus of air quality management strategies. In this study, we examined NOx sources and the atmospheric conversion of NOx in Karachi, Pakistan, a megacity in South Asia with serious particulate pollution problems. Oceanic contributions to NOx were quantified for the first time based on a novel approach using nitrogen/oxygen isotopic analysis in nitrate (δ15N–NO3; δ18O–NO3) and a Bayesian model. Our results showed that δ15N–NO3 in Karachi varied between −10.2‰ and +12.4‰. As indicated by the δ18O–NO3 findings (+66.2 ± 7.8‰), the •OH pathway dominated NOx conversion throughout the nearly two-year observation, but high NO3 events were attributed to the O3 pathway. Coal combustion was the most significant source (32.0 ± 9.8%) of NOx in Karachi, with higher contributions in the autumn and winter; a similar situation occurred for biomass burning + lightning (30.3 ± 6.5%). However, mobile sources (25.2 ± 6.4%) and microbial processes (12.5 ± 7.5%) exhibited opposite seasonal trends. The oceanic contributions to NOx in Karachi were estimated to be 16.8%, of which lightning, shipping emissions, and microbial processes accounted for 20.3%, 46.3%, and 33.4%, respectively, emphasizing the dominance of shipping emissions as an oceanic NOx source.

中文翻译:

巴基斯坦首都卡拉奇大都会城市地区硝酸盐的同位素解释:海洋对NOx的贡献。

减少氮氧化物(NO x)已成为空气质量管理策略的重点。在这项研究中,我们研究了NO X光源和NO的转化大气X在卡拉奇,巴基斯坦,南亚大城市严重的颗粒物污染问题。到NO海洋贡献X用于使用硝酸盐氮/氧同位素分析基于一种新的方法在第一时间进行定量(δ 15 N-NO 3 -18 O型NO 3 - )和贝叶斯模型。我们的研究结果表明,δ 15 N-NO 3 -卡拉奇之间变化-10.2‰和+ 12.4‰。如δ所示18 O型NO 3 -的调查结果(66.2±7.8‰),该•OH途径的主导NO X转换贯穿近两年的观察,但高NO 3 -事件归因于将O 3途径。在卡拉奇,煤炭燃烧是NO x的最主要来源(32.0±9.8%),在秋季和冬季贡献更大;生物质燃烧+闪电的情况类似(30.3±6.5%)。然而,流动源(25.2±6.4%)和微生物过程(12.5±7.5%)表现出相反的季节性趋势。海洋对NO x的贡献在卡拉奇估计为16.8%,其中闪电,航运排放和微生物过程分别占20.3%,46.3%,和33.4%,,强调航运排放作为海洋NO的主导地位X源。
更新日期:2020-07-07
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