Yearly variations of water-soluble ions over Xi'an, China: Insight into the importance contribution of nitrate to PM2.5

IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES
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Abstract

Water-soluble inorganic ions (WSIIs) in PM2.5 play an important role in the formation of air pollution, which in turn affects climate change and human health. The formation pathways and factors influencing WSIIs have received extensive attention. Here, we analyzed the contents of nine WSIIs in PM2.5, collected from 2015 to 2021 in Xi'an City, China, with the aim of investigating long-term atmospheric pollution changes. Sulfate (SO42−), nitrate (NO3), and ammonium (NH4+) together contributed to 66.8%–88.1% and Ca2+ accounted for 5.1%–13.1% of total WSIIs. The relative content of SO42− exhibited a gradually decreasing trend (from 49.80% in 2015 to 29.98% in 2021), whereas NO3 was increased in the same time period (from 13.96% in 2015 to 29.92% in 2021). In addition, the nitrogen oxidation rate showed an annual increase in this period, whereas the sulfur oxidation rate decreased, and their fitted curves intersected in 2019. The key finding of this study is that the air pollution pattern in Xi'an has changed from sulfate-dominated to nitrate-dominated particles, as evidenced by the feature importance results of the random forest model. We propose that more attention should be paid to vehicle emissions and road dust as pollution sources. Overall, the findings of this study serve as a useful reference to aid relevant authorities in devising more effective policies for controlling PM2.5 pollution at its source.

Abstract Image

中国西安上空水溶性离子的年变化:洞察硝酸盐对 PM2.5 的重要贡献
PM2.5 中的水溶性无机离子(WSIIs)在空气污染的形成过程中发挥着重要作用,进而影响气候变化和人类健康。WSIIs 的形成途径和影响因素受到广泛关注。在此,我们分析了 2015 年至 2021 年在中国西安市采集的 PM2.5 中 9 种 WSIIs 的含量,旨在研究大气污染的长期变化。硫酸盐(SO42-)、硝酸盐(NO3-)和铵盐(NH4+)共占WSII总量的66.8%-88.1%,Ca2+占5.1%-13.1%。SO42- 的相对含量呈逐渐下降趋势(从 2015 年的 49.80% 下降到 2021 年的 29.98%),而 NO3- 的相对含量在同一时期则有所上升(从 2015 年的 13.96% 上升到 2021 年的 29.92%)。此外,氮氧化率在此期间呈逐年上升趋势,而硫氧化率则有所下降,两者的拟合曲线在 2019 年相交。本研究的主要发现是,从随机森林模型的特征重要性结果来看,西安的空气污染模式已从硫酸盐颗粒为主转变为硝酸盐颗粒为主。我们建议应更多地关注汽车尾气排放和道路扬尘这两个污染源。总之,本研究的结果可作为有益的参考,帮助相关部门制定更有效的政策,从源头上控制 PM2.5 污染。
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来源期刊
Atmospheric Pollution Research
Atmospheric Pollution Research ENVIRONMENTAL SCIENCES-
CiteScore
8.30
自引率
6.70%
发文量
256
审稿时长
36 days
期刊介绍: Atmospheric Pollution Research (APR) is an international journal designed for the publication of articles on air pollution. Papers should present novel experimental results, theory and modeling of air pollution on local, regional, or global scales. Areas covered are research on inorganic, organic, and persistent organic air pollutants, air quality monitoring, air quality management, atmospheric dispersion and transport, air-surface (soil, water, and vegetation) exchange of pollutants, dry and wet deposition, indoor air quality, exposure assessment, health effects, satellite measurements, natural emissions, atmospheric chemistry, greenhouse gases, and effects on climate change.
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