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Effect of solubility limitation on hygroscopic growth and cloud drop activation of SOA particles produced from traffic exhausts
Journal of Atmospheric Chemistry ( IF 2 ) Pub Date : 2018-11-23 , DOI: 10.1007/s10874-018-9380-5
C. Wittbom , A. C. Eriksson , J. Rissler , P. Roldin , E. Z. Nordin , S. Sjogren , P. T. Nilsson , E. Swietlicki , J. Pagels , B. Svenningsson

Hygroscopicity measurements of secondary organic aerosol (SOA) particles often show inconsistent results between the supersaturated and subsaturated regimes, with higher activity as cloud condensation nucleus (CCN) than indicated by hygroscopic growth. In this study, we have investigated the discrepancy between the two regimes in the Lund University (LU) smog chamber. Various anthropogenic SOA were produced from mixtures of different precursors: anthropogenic light aromatic precursors (toluene and m-xylene), exhaust from a diesel passenger vehicle spiked with the light aromatic precursors, and exhaust from two different gasoline-powered passenger vehicles. Three types of seed particles were used: soot aggregates from a diesel vehicle, soot aggregates from a flame soot generator and ammonium sulphate (AS) particles. The hygroscopicity of seed particles with condensed, photochemically produced, anthropogenic SOA was investigated with respect to critical supersaturation (sc) and hygroscopic growth factor (gf) at 90% relative humidity. The hygroscopicity parameter κ was calculated for the two regimes: κsc and κgf, from measurements of sc and gf, respectively. The two κ showed significant discrepancies, with a κgf /κsc ratio closest to one for the gasoline experiments with ammonium sulphate seed and lower for the soot seed experiments. Empirical observations of sc and gf were compared to theoretical predictions, using modified Köhler theory where water solubility limitations were taken into account. The results indicate that the inconsistency between measurements in the subsaturated and supersaturated regimes may be explained by part of the organic material in the particles produced from anthropogenic precursors having a limited solubility in water.

中文翻译:

溶解度限制对交通尾气产生的 SOA 颗粒吸湿生长和云滴活化的影响

二次有机气溶胶 (SOA) 粒子的吸湿性测量结果通常在过饱和和亚饱和状态之间显示不一致的结果,云凝结核 (CCN) 的活动比吸湿增长表明的要高。在这项研究中,我们调查了隆德大学 (LU) 烟雾室中两种制度之间的差异。各种人为 SOA 是由不同前体的混合物产生的:人为轻芳烃前体(甲苯和间二甲苯)、柴油乘用车的尾气中添加了轻芳烃前体,以及两种不同的汽油动力乘用车的尾气。使用了三种类型的种子颗粒:来自柴油车的烟灰聚集体、来自火焰烟尘发生器的烟灰聚集体和硫酸铵 (AS) 颗粒。在 90% 相对湿度下,针对临界过饱和度 (sc) 和吸湿性生长因子 (gf) 研究了具有凝聚的、光化学产生的、人为 SOA 的种子颗粒的吸湿性。分别从 sc 和 gf 的测量值计算了两种状态的吸湿性参数 κ:κsc 和 κgf。两个 κ 显示出显着的差异,对于硫酸铵种子的汽油实验,κgf /κsc 比最接近 1,而对于煤烟种子实验则较低。将 sc 和 gf 的经验观察与理论预测进行比较,使用修正的 Köhler 理论,其中考虑了水溶性限制。
更新日期:2018-11-23
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