气溶胶生长过程的微观动力学研究

气溶胶作为大气颗粒物的重要成分对大气环境以及人体健康均有重要影响.其中气溶胶的吸湿性作为影响其在大气中存活时间以及物理化学性质的重要因素受到广泛关注.目前对于气溶胶颗粒的吸湿性研究较为简单,对于气溶胶颗粒物微观结构对吸湿性的影响较少.本文根据Langmuir吸附模型、Fick扩散定律建立了单颗粒的气-粒作用模型,分析了气溶胶颗粒物的均匀分布结构(H2O/C2H2O4)以及非均匀分布结构(H2O/C2H2O4/H2SO4)对其吸湿性的不同影响。研究结果发现,气溶胶颗粒物的非均匀分布结构会影响其吸湿过程的快慢;对于理想流体构成的气溶胶分子,由于分子之间不存在分子间相互作用,因此气-粒间的水分子交换更快,颗粒物外侧浓度首先升高,接着在浓度差的作用下,内侧颗粒逐渐向外扩散,直至达到平衡;相较与大尺寸的颗粒,在相同体积比的条件下,小颗粒由于气溶胶颗粒物的接触角大,因此表面张力大,水分更难流失;此外,由于大尺寸的气溶胶颗粒物表面积体积比较小,因此颗粒失水速度低,需要更多的时间达到相平衡。

Study on the Microscopic Dynamics of Aerosols Evolution

As an important component of atmospheric particulate matter,aerosols have an important impact on the atmospheric environment and human health.The hygroscopicity of aerosols has been widely researched as an important factor for its survival time and physicochemical properties in the atmosphere.At present,the researches on the hygroscopicity of aerosols is relatively simple,and the influence of the microstructure of aerosols on the hygroscopicity is less.Based on Langmuir adsorption model and Fick’s diffusion law,a single particle gas-particle interaction model was established.The uniform distribution structure of aerosol particles(H2O/C2H2O4)and the non-uniform distribution structure(H2O/C2H2O4/H2SO4)were analyzed.The results show that the non-uniform distribution structure of aerosols affects the speed of the water uptake process.For aerosol molecules composed of ideal fluids,there is no intermolecular interaction between molecules,so the water-particle exchange between gas and particles is faster,and the concentration of the outer layers firstly increases,and then the inner layers gradually diffuse outward until equilibrium is reached for the difference of layer concentration.Comparing with the large particles in the same volume ratio,the water in small particles is more difficult to run off because of the larger contact angle and surface tension.In addition,the surface area of??the large particles is small,and the rate of water loss is low.It needs more time to reach the balance.