Laboratory observations of temperature and humidity dependencies of nucleation and growth rates of sub‐3 nm particles
Laboratory observations of temperature and humidity dependencies of nucleation and growth rates of sub‐3 nm particles
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DOI：
10.1002/2016jd025619
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发表时间：
2017-02
期刊：
影响因子：
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通讯作者：
Huan Yu;Liang Dai;Yi Zhao;V. Kanawade;S. N. Tripathi;X. Ge;Mindong Chen;Shan‐Hu Lee
中科院分区：
文献类型：
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作者：
Huan Yu;Liang Dai;Yi Zhao;V. Kanawade;S. N. Tripathi;X. Ge;Mindong Chen;Shan‐Hu Lee
温度和相对湿度（RH）是气溶胶形成中最重要的热力学参数，但缺乏对温度和RH对成核和生长依赖的实验室研究。在这里，我们报告了实验观察到的温度和相对湿度对硫酸气溶胶成核和生长的依赖。实验在流动管中进行，温度为248 ~ 313 K，相对湿度为0.8% ~ 79%，硫酸的相对酸度（RA）为6 × 10−5 ~ 0.38 （2 × 107 ~ 109 cm−3）。碱基化合物的杂质水平测定为NH3 < 23 pptv（千分之一体积），甲胺< 1.5 pptv，二甲胺< 0.52 pptv。结果表明，在固定硫酸浓度下，低温有利于成核，而在固定硫酸浓度下，低温不利于成核。在行星边界层温度和硫酸范围内，硫酸和水的二元成核可以忽略不计。推导了一种经验算法，将成核速率与RA、RH和温度一起关联起来。碰撞限制的自由硫酸分子的冷凝不能预测在亚3nm尺寸范围内观察到的生长速率，以及它对温度和相对湿度的依赖。这表明，对于亚3nm的颗粒生长，应考虑蒸发、硫酸水化和其他三元分子的可能参与。
Temperature and relative humidity (RH) are the most important thermodynamic parameters in aerosol formation, yet laboratory studies of nucleation and growth dependencies on temperature and RH are lacking. Here we report the experimentally observed temperature and RH dependences of sulfuric acid aerosol nucleation and growth. Experiments were performed in a flow tube in the temperature range from 248 to 313 K, RH from 0.8% to 79%, and relative acidity (RA) of sulfuric acid from 6 × 10−5 to 0.38 (2 × 107–109 cm−3). The impurity levels of base compounds were determined to be NH3 < 23 pptv (parts per thousand by volume), methylamine < 1.5 pptv, and dimethylamine < 0.52 pptv. Our results showed that low temperatures favor nucleation at fixed sulfuric acid concentration but impede nucleation when RA is fixed. It is also shown that binary nucleation of sulfuric acid and water is negligible in planetary boundary layer temperature and sulfuric acid ranges. An empirical algorithm was derived to correlate the nucleation rate with RA, RH, and temperature together. Collision‐limited condensation of free‐sulfuric acid molecules fails to predict the observed growth rate in the sub‐3 nm size range, as well as its dependence on temperature and RH. This suggests that evaporation, sulfuric acid hydration, and possible involvement of other ternary molecules should be considered for the sub‐3 nm particle growth.