The reductions of oxalate and its precursors in cloud droplets relative to wet particles
The reductions of oxalate and its precursors in cloud droplets relative to wet particles
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云滴中草酸盐及其前体相对于湿颗粒的减少
DOI：
10.1016/j.atmosenv.2020.117632
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发表时间：
2020-08-15
影响因子：
5
通讯作者：
Sheng, Guoying
中科院分区：
文献类型：
--
作者：
Lin, Qinhao;Yang, Yuxiang;Sheng, Guoying
水相中草酸盐的形成机制仍不确定。 2018年5月9日至6月4日，利用单颗粒气溶胶质谱仪在中国南方山区采集了约60万个含草酸盐颗粒和45万个含草酸盐前体颗粒（例如乙酸盐、乙醛酸盐、丙酮酸盐和丙二酸盐）。比较了三种具有不同液态水含量（包括云滴残留物）的代表性气溶胶中草酸盐或其前体物的数量分数(RES)、云间质粒子 (INTER) 和无云环境粒子 (AMB)。相对于 INTER 和 AMB，RES 中草酸盐的数量分数较低，这主要归因于前体的减少。这与之前报道的云内草酸盐形成的增强相矛盾。进一步分析表明，气溶胶酸度对前体的形成及其向草酸盐的转化有重大影响。随着相对气溶胶酸度（定义为硫酸盐和硝酸盐峰面积之和除以铵峰面积）的增加，前体的形成增加，同时前体向草酸盐的转化受到抑制。同时，相对于RES，这种影响在国米和AMB中更为明显。这项工作强调了气溶胶酸度和液态水含量在草酸盐及其前体的水相形成中的作用。
The formation mechanism of oxalate in the aqueous phase remains uncertain. Approximately 600 000 oxalate-containing particles and 450 000 its precursors-containing particles (e.g., acetate, glyoxylate, pyruvate and malonate) were obtained using a single particle aerosol mass spectrometer at a mountain site in southern China from 9 May to 4 June, 2018. The number fraction of oxalate or its precursors was compared within three representative aerosols with different liquid water contents including cloud droplet residues (RES), cloud interstitial particles (INTER) and cloud-free ambient particles (AMB). Lower number fraction of oxalate was found in the RES relative to INTER and AMB, mostly attributed to the decrease in precursors. This was conflicted with the enhancement of in-cloud oxalate formation previously reported. Further analysis indicated that the aerosol acidity had a major influence on the formation of precursors and their conversion to oxalate. With the increase of relative aerosol acidity (defined as the sum of sulfate and nitrate peak areas divided by ammonium peak area), the formation of precursors was increased while the conversion of precursors to oxalate was suppressed. Meanwhile, this influence was more pronounced in the INTER and AMB relative to RES. This work highlighted the roles of aerosol acidity and liquid water content in the aqueous phase formations of oxalate and its precursors.