基于单颗粒气溶胶吸湿增长模型,分别建立了亲水性和亲疏水性双颗粒凝聚气溶胶的吸湿增长模型,并利用离散偶极子近似方法计算了不同相对湿度时两种凝聚粒子的散射特性。结果表明: 在40%~90%湿度范围内,亲水性双颗粒凝聚气溶胶 [以氯化钠(NaCl)-硝酸钠(NaNO3)颗粒为例]的散射系数存在两次跃变,而散射系数跃变的位置和增幅与NaCl-NaNO3颗粒的体积比密切相关;二次潮解后,不同体积比的亲水性凝聚粒子的散射系数随相对湿度的增加均呈现出指数增长趋势,且NaNO3的体积分数越大,散射系数增长幅度越大。对于不同体积比的亲疏水性双颗粒凝聚粒子 (以NaCl-烟尘颗粒为例),散射系数随相对湿度的增加均呈现指数增长,NaCl的体积比越大,散射系数增长越快,而潮解后亲疏水性粒子的相对位置关系对凝聚粒子散射系数的影响较小。上述结果可为进一步研究多颗粒凝聚气溶胶的吸湿散射特性提供可靠的理论基础。

Based on the single particle aerosol hygroscopic growth model, the hygroscopic growth models of the hydrophilic and hydrophobic two-particle agglomerated aerosols are established, respectively. The scattering characteristics of two types of condensation particles at different relative humidity are calculated by using the discrete dipole approximation method. The results show that in the humidity range of 40%--90%, the scattering coefficient of the hydrophilic two-particle condensed aerosol (e.g., NaCl-NaNO₃) has two jumps, and the position and increase of the scattering coefficient jump are closely related to the volume ratio of NaCl-NaNO₃ particles. After the second deliquescence, the scattering coefficients of hydrophilic agglomerated particles with different volume ratios show an exponential growth trend with the increase of relative humidity. The greater the volume fraction of NaNO₃, the larger the increase in scattering coefficient. For hydrophilic and hydrophobic two-particle agglomerated aerosols (e.g., NaCl-Soot) with different volume ratios, the scattering coefficients show an exponential growth trend with the increase of relative humidity. The larger the NaCl volume ratio, the larger the growth rate of the scattering coefficient. But the relative position relationship between hydrophilic and hydrophobic particles after deliquescence has little effect on the scattering coefficient of agglomerated particles. The above results can provide a reliable theoretical basis for further research on the hygroscopic scattering characteristics of multi-particle aggregated aerosols.