Atmospheric Δ17O(NO3-) reveals nocturnal chemistry dominates nitrate production in Beijing haze
Atmospheric Δ17O(NO3-) reveals nocturnal chemistry dominates nitrate production in Beijing haze
复制标题
大气中硝酸根的Δ17O值表明，夜间化学反应主导了北京雾霾中硝酸盐的生成 。
DOI：
10.5194/acp-18-14465-2018
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发表时间：
2018-10-10
影响因子：
6.3
通讯作者：
Zhan, Haicong
中科院分区：
文献类型：
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作者：
He, Pengzhen;Xie, Zhouqing;Zhan, Haicong
大气硝酸盐浓度的快速增加是北京市细颗粒物污染（以下简称灰霾）发生的重要驱动力。然而，这种快速增加的硝酸盐质量的确切机制还没有得到很好的限制，从实地观察。本文首次观测了北京灰霾中NO3-的氧17过量（Δ O-17（NO3-）），揭示了不同NO3-形成途径的相对重要性，同时还观测了Δ N-15（NO3-）。在我们的采样期间，PM2.5的12小时平均质量浓度从16到323 μ g m（-3）不等，平均值为（141 +/- 88（1 SD））μ g m（-3），硝酸盐从0.3到106.7 μ g m（-3）不等。观察到的Delta O-17（NO3-）范围为27.5% 0至33.9% 0，平均值为（30.6 +/- 1.8）% 0，而Delta N-15（NO3-）范围为-2.5% 0至19.2% 0，平均值为（7.4 +/- 6.8）% 0。Delta O-17（NO3-）约束计算表明，在污染日（PM2.5 >= 75 μ g m（-3）），夜间途径（N2 O 5 + H2O/Cl-和NO3 + HC）主导硝酸盐的产生，平均可能比例为56- 97%。我们的研究结果说明了Delta（17）在追踪硝酸盐形成途径方面的潜力;未来的建模工作与同位素数据的约束可能会进一步提高我们对雾霾期间氮循环的理解。
The rapid mass increase of atmospheric nitrate is a critical driving force for the occurrence of fine-particle pollution (referred to as haze hereafter) in Beijing. However, the exact mechanisms for this rapid increase of nitrate mass have not been well constrained from field observations. Here we present the first observations of the oxygen-17 excess of atmospheric nitrate (Delta O-17(NO3-)) collected in Beijing haze to reveal the relative importance of different nitrate formation pathways, and we also present the simultaneously observed delta N-15(NO3-). During our sampling period, 12h averaged mass concentrations of PM2.5 varied from 16 to 323 mu g m(-3) with a mean of (141 +/- 88(1SD)) mu g m(-3), with nitrate ranging from 0.3 to 106.7 mu g m(-3). The observed Delta O-17(NO3-) ranged from 27.5 %0 to 33.9 %0 with a mean of (30.6 +/- 1.8)%0, while delta N-15(NO3-) ranged from -2.5 %0 to 19.2 %0 with a mean of (7.4 +/- 6.8)%0. Delta O-17(NO3-)-constrained calculations suggest nocturnal pathways (N2O5 + H2O/Cl- and NO3 + HC) dominated nitrate production during polluted days (PM2.5 >= 75 mu g m(-3)), with a mean possible fraction of 56-97 %. Our results illustrate the potentiality of Delta(17) in tracing nitrate formation pathways; future modeling work with the constraint of isotope data reported here may further improve our understanding of the nitrogen cycle during haze.