城市大气中多环芳烃的降雨冲刷

Scavenging of airborne polycyclic aromatic hydrocarbons by rainfall in urban area

2009年7～8月采集了10场降雨的雨水及对应降雨前后的大气样品,研究降雨对大气中多环芳烃的冲刷和净化作用.雨水中多环芳烃以颗粒态为主,4环组分浓度最高.气态、颗粒态和总的多环芳烃的净化率分别为3.9×102、3.7×104和5.9×103.降雨对大气的冲刷以颗粒物为主,气态多环芳烃的净化主要体现为低环组分(2～3环),高环(4～6环)组分主要以颗粒态的形式进行冲刷和净化,总净化率4～6环组分PAHs高于2～3环组分.大气颗粒态PAHs和气态PAHs的降雨沉降效率与包括降雨时间等在内的降雨综合特征有显著相关关系.

The removal of airborne PAHs,determined from atmospheric and precipitation samples,was observed during ten rain events from July to August in 2009.Concentrations of PAHs in rainwater were dominated in particle phase,with highest concentration in the 4-ring components.∑16PAHs scavenging ratios for gaseous,particles and total air averaged at 3.9×102,3.7×104 and 5.9×103,respectively.The PAHs removal from the atmosphere by precipitation occurred primarily in particle phase.The gaseous phase dominated the scavenging of low molecular weight components,while the particle phase dominated the scavenging of high molecular weight components.The total scavenging ratios of high molecular weight components were higher than those of low molecular weight components.Wet depositing efficiencies of PAHs for gaseous and particles were correlated with rain index.