霾过程黑碳对气溶胶散射吸湿增长的影响

Black carbon during haze processes impact on aerosol scattering hygroscopic growth

利用成都市2017年10~12月逐时的“干”气溶胶散射系数、吸收系数和环境气象监测资料,结合同时次气溶胶粒径吸湿增长因子(Gf)的反演数据,分析了4类霾强度条件下黑碳浓度(C_(BC))的变化特征,并基于广义可加模型(GAM)探讨了C_(BC)对气溶胶散射吸湿增长因子(f)的影响机制.结果表明:(1)轻微、轻度、中度和重度霾强度条件下的C_(BC)均服从对数正态分布,其均值随霾强度的增加而增大,变差系数则随霾强度的增加而减小.(2) C_(BC)与Gf之间呈现非线性负相关,C_(BC)与C_(PM2.5/PM10)(细颗粒物质量浓度与粗颗粒物质量浓度之比)之间则呈现非线性正相关(均通过了α=0.01的显著性检验);随着霾的渐近演化,Gf随C_(BC)增加而减小的趋势持续增强,C_(PM2.5/PM10)随C_(BC)增加而增大的趋势则持续减弱.(3) Gf与C_(PM2.5/PM10)之间存在显著的交互作用(通过了α=0.001的显著性检验),以Gf与C_(PM 2.5/PM10)为双变量的GAM模型能更好地表征f的变化特征.

Based on the hourly observed“dry”aerosol scattering coefficient,aerosol absorption coefficient,and the environmental meteorological monitoring data,and the retrieved aerosol particle size hygroscopic growth factor (Gf) from October to December2017 in Chengdu,the statistical characteristics of black carbon concentration (C_(BC)) were analyzed under four kinds of haze intensity conditions.Besides,the influence mechanism for C_(BC) on the aerosol scattering hygroscopic growth was investigated using the aid of Generalized Additive Model (GAM).The results show that:(1) C_(BC) obeyed lognormal distribution under slight,mild,moderate,and severe haze conditions.The averaged value of C_(BC) increased but the variation coefficient of C_(BC) decreased with increasing haze intensity.(2) C_(BC) showed nonlinear negative correlations with Gf,and nonlinear positive correlations with C_(PM2.5/PM10 )(mass concentration ratio between fine particulate matter and coarse particulate matter)(passing the α=0.01 significant test).Haze development intensified the downward trend of Gf with C_(BC) and reduced the upward trend of C_(PM2.5/PM10) with C_(BC).(3) There were significant interactions between C_(PM2.5/PM10)and Gf (passing the α=0.001 significant test).The bivariate GAM model with Gf and C_(PM2.5/PM10) could better characterize the variation on f.