Measured particle water uptake enhanced by co-condensing vapours
Measured particle water uptake enhanced by co-condensing vapours
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DOI：
10.5194/acp-18-14925-2018
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发表时间：
2018-06
影响因子：
6.3
通讯作者：
Dawei Hu;D. Topping;G. Mcfiggans
中科院分区：
文献类型：
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作者：
Dawei Hu;D. Topping;G. Mcfiggans
抽象的。无机或有机水蒸气在不断增长的水滴上的共凝结可以显著增加云凝结核(CCN)和云滴数量浓度，从而影响云反照率和气候。到目前为止，关于这一过程的直接观测证据很少。我们在实验室中测量了无机盐颗粒在291.15 K下暴露在水和有机蒸气中的生长，结果表明有机蒸气的共冷凝显著地增强了气溶胶的吸水率。在接触水和丙二醇蒸气后，在相同的相对湿度(RH)下，硫酸铵颗粒的生长速度比之前测量的任何无机或有机颗粒都要大得多。观测到的最大当量吸湿性参数κ高达2.64，远高于用常规仪器测得的大气颗粒物的值(0.1lt；κ<；0.9)，这可能是对这种影响视而不见的。在不断补充的有机蒸汽场下，由于非挥发性溶质的存在，颗粒从未达到平衡，并随着暴露时间的增加而持续增长，这与模型模拟一致。此外，本研究还测定了丁二醇(挥发度相近，但在w=0.9时比丙二醇高)和三甘醇(挥发度低，在w=0.9时比丙二醇低)蒸汽的共缩合反应。在90%相对湿度下，硫酸铵颗粒在水和三甘醇蒸气中的最大等效吸湿性参数κ高达8.48。这种通过水蒸气共凝聚而增强的颗粒水吸收构成了对这一过程的直接测量，这可能会对大气中云滴的形成产生重大影响。此外，暴露在与水共冷凝的丁二醇和三甘醇蒸气中的模型模拟表明，除了Sorg之外，还有其他因素影响半挥发性有机化合物(SVOC)的共缩合，这些因素尚不清楚。
Abstract. Co-condensation of inorganic or organic vapours on growing droplets could significantly enhance both cloud condensation nucleus (CCN) and cloud droplet number concentration, thereby influencing cloud albedo and climate. Until now, there has been very few direct observational evidence of this process. We have measured the growth of inorganic salt particles exposed to both water and organic vapours at 291.15 K in the laboratory, showing that co-condensation of the organic vapours significantly enhances water uptake of aerosols. After exposure to water and propylene glycol vapours, ammonium sulfate particles grew much more than any previously measured particles, inorganic or organic, at the same relative humidity (RH). The maximum equivalent hygroscopicity parameter, κ, was observed to reach up to 2.64, very much higher than values (0.1 < κ < 0.9) measured for atmospheric particulate matter using conventional instrumentation, which may be blind to this effect. Under a continuously replenishing organic vapour field, the particles never reached equilibrium owing to the presence of the involatile solute and were observed to continuously grow with increasing exposure time, in agreement with model simulations. Co-condensation of butylene glycol (which has similar volatility but, at aw = 0.9, a higher Sorg than propylene glycol in our system) and tri-ethylene glycol (which has lower volatility and, at aw = 0.9, lower Sorg than propylene glycol in our system) vapours was additionally measured in this study. The maximum equivalent hygroscopicity parameter, κ, reached as high as 8.48 for ammonium sulfate particles exposed to water and tri-ethylene glycol vapours at 90 % RH. This enhancement of particle water uptake through co-condensation of vapours constitutes the direct measurement of this process, which may substantially influence cloud droplet formation in the atmosphere. In addition, the model simulations for exposure to co-condensing butylene glycol and tri-ethylene glycol vapours with water show that there are factors other than Sorg which influence the co-condensation of semi-volatile organic compounds (SVOCs) that are as yet not understood.