The aida soot coating campaign influence of coatings on structure and optics of soot aerosol

摘要

Soot particles are the most strongly absorbing aerosol particles in the atmosphere.Therefore they have a direct climatic impact by absorbing solar radiation which may also affect photochemical reaction rates.Furthermore,the absorption of radiation within the troposphere can lead to an atmospheric warming which in turn may have an impact on cloud formation.Therefore soot aerosol can have also an indirect influence on climate.During the atmospheric lifetime of soot of about one week ageing processes like coagulation and condensation change the mixing state of soot from an external mixture to an internal one.These changes can alter their dynamic,optical,and hygroscopic properties significantly.This is evident in model calculations of the climatic impact of coated soot particles (Jacobson et al.,2001)but also in first laboratory investigations (Schnaiter et al.,2002;Saathoff et al.,2002)of a possible enhancement of the soot absorption upon coating with non absorbing material.With the participation of 7 German,Swiss and Austrian institutes an intensive soot coating campaign was organised in Spring 2002 at the aerosol chamber AIDA of Forschungszentrum Karlsruhe.The goal of the campaign was a comprehensive investigation of the changing physical and chemical properties of soot from a commercial Diesel engine and spark generated (Palas)soot due to coating with different layers of organic material or sulphate.