Significant impactor sampling artifacts of ammonium, nitrate, and organic acids
Significant impactor sampling artifacts of ammonium, nitrate, and organic acids
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DOI：
10.1016/j.atmosenv.2022.118985
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发表时间：
2022-04
影响因子：
5
通讯作者：
Y. Yao;X. Ye;Tianxiang Gao;Hao Feng;Yanan Chen;Jianmin Chen
中科院分区：
文献类型：
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作者：
Y. Yao;X. Ye;Tianxiang Gao;Hao Feng;Yanan Chen;Jianmin Chen
半挥发性化合物如硝酸铵和有机酸在裸露和未裸露撞击器上的蒸发损失可能大大低估其质量负荷。在这项研究中，甲酸盐，草酸盐，和其他半挥发性无机成分的采样文物进行了测量，使用上游和下游的MOUDI系统在上海的组合。与常规采样相比，MOUDI采样器采集到的半挥发性铵、硝酸盐、甲酸盐和草酸盐的浓度降低了11%-43%，表明去除采样空气中的酸性和碱性气态化合物对半挥发性无机盐和低分子量有机酸具有显著的负采样伪像。下游扩散管中酸性和碱性气体化合物浓度较高，证实了定期MOUDI取样的蒸发损失。气溶胶甲酸盐的浓度被严重低估，在裸露和未裸露的MOUDI上的平均采样效率分别为36.7 ± 10%和55.2 ± 8.5%。对于小于0.1 μm的颗粒群，总有机酸与硫酸盐的质量比增加到约0.5，表明有机酸可能影响该尺寸范围内的颗粒酸性和化学行为。
The evaporation losses of semi-volatile compounds such as ammonium nitrate and organic acids on denuded and undenuded impactors can significant underestimate their mass loadings. In this study, sampling artifacts of formate, oxalate, and other semi-volatile inorganic components were measured using a combination of an upstream-denuded and a downstream-denuded MOUDI system in Shanghai. Compared to regular sampling, the concentrations of semi-volatile ammonium, nitrate, formate, and oxalate collected on the upstream-denuded MOUDI sampler decreased by 11%–43%, suggesting removing acidic and alkaline gaseous compounds from the sampled air had significant negative sampling artifacts for semi-volatile inorganic salts and low-molecular-weight organic acids. Evaporation losses from regular MOUDI sampling were confirmed by the higher concentrations of acidic and alkaline gaseous compounds in the downstream denuder. The concentration of aerosol formate was seriously underestimated, with average sampling efficiencies of 36.7 ± 10% and 55.2 ± 8.5% on denuded and undenuded MOUDIs, respectively. The mass ratio of total organic acids to sulfate increased to approximately 0.5 for the particle population smaller than 0.1 μm, indicating that organic acids might influence particle acidity and chemical behaviors in this size range.