Influences of atmospheric pollution on the contributions of major oxidation pathways to PM2.5 nitrate formation in Beijing
Influences of atmospheric pollution on the contributions of major oxidation pathways to PM2.5 nitrate formation in Beijing
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北京市大气污染对PM2.5硝酸盐主要氧化途径贡献的影响
DOI：
10.1029/2019jd030284
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
Xue-Yan Liu
中科院分区：
文献类型：
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作者：
Yan-Li Wang;Wei Song;Wen Yang;Xin-Chao Sun;Yin-Dong Tong;Xue-Mei Wang;Cong-Qiang Liu;Zhi-Peng Bai;Xue-Yan Liu
硝酸盐（NO3−）是无机气溶胶的主要成分，主要由NO2通过OH自由基（OH·）和大气中的O3氧化而成。然而，OH·和O3途径对城市气溶胶中NO3−的贡献以及空气污染对这两种途径的影响仍不清楚。2014年，在北京测量了PM2.5中NO3−的氧同位素。冬季的Δ 17 O-NO3-值（17.0-32.8‰）（27.2 ± 3.6‰）显著高于夏季（24.2 ± 1.3‰）。通过估算O3对NOx循环的贡献，计算了每个观测值的NO3−端元的Δ 17 O值，这些端元通过NO2+ OH·（P1）、NO3· + DMS/HC（P2）和N2 O 5水解（P3）途径产生。使用R模型中的稳定同位素分析计算三种途径的贡献（P1：32 ± 10%，P2：34 ± 10%，P3：34 ± 20%）。我们发现NO3−的形成主要由O3氧化途径（P2 + P3;每年68 ± 23%，春季73 ± 21%，夏季59 ± 23%，秋季75 ± 20%，冬季69 ± 22%）。此外，PM2.5、NO2和NO3−污染降低了OH·途径相对于O3途径对NO3−产生的重要性。然而，O3污染增加了OH·途径相对于O3途径对NO3−产生的重要性。这些结果为了解NO2主要氧化途径的相对重要性提供了对颗粒NO3−中氧同位素记录的全面分析。在城市环境中，大气污染严重影响NO2氧化为NO3−的途径。
Nitrate (NO3−), which is mainly oxidized from NO2by the OH radical (OH·) and O3in the atmosphere, is a major component of inorganic aerosols. However, the contributions of the OH· and O3pathways to NO3−in urban aerosols and the influence of air pollution to both pathways remain unclear. Oxygen isotopes of NO3−were measured for PM2.5in Beijing in 2014. The Δ17O‐NO3−values (17.0–32.8‰) were significantly higher in winter (27.2 ± 3.6‰) than in summer (24.2 ± 1.3‰). By estimating contributions of O3to the NOxcycle, the Δ17O values of NO3−endmembers produced via the NO2+ OH· (P1), NO3· + DMS/HC (P2), and N2O5hydrolysis (P3) pathways were calculated for each observation. The contributions of the three pathways (P1: 32 ± 10%, P2: 34 ± 10%, and P3: 34 ± 20% annually) were calculated using the Stable Isotope Analysis in R model. We found that NO3−formation was dominated by the O3oxidation pathways (P2 + P3; 68 ± 23% annually, 73 ± 21% in spring, 59 ± 23% in summer, 75 ± 20% in autumn, and 69 ± 22% in winter). Moreover, PM2.5, NO2, and NO3−pollution decreased the importance of the OH· pathway relative to the O3pathways for NO3−production. However, O3pollution increased the importance of the OH· pathway relative to the O3pathways for NO3−production. These results provided a comprehensive analysis on the oxygen isotope records in particulate NO3−for understanding the relative importance of major oxidation pathways of NO2. Atmospheric pollution substantially influenced the pathways of NO2oxidation to NO3−in city environments.