Hygroscopicity and optical properties of alkylaminium sulfates

摘要

The hygroscopicity and optical properties of alkylaminium sulfates(AASs) were investigated using a hygroscopicity tandem diferential mobility analyzer coupled to a cavity ring-down spectrometer and a nephelometer. AAS particles do not exhibit a deliquescence phenomenon and show a monotonic increase in diameter as the relative humidity(RH) ascends. Hygroscopic growth factors(GFs) for 40, 100 and 150 nm alkylaminium sulfate particles do not show an apparent Kelvin efect when RH is less than 45%, whereas GFs of the salt aerosols increase with initial particle size when RH is higher than 45%. Calculation using the Zdanovskii-Stokes-Robinson mixing rule suggests that hygroscopic growth of triethylaminium sulfate-ammonium sulfate mixtures is non-deliquescent, occurring at very low RH, implying that the displacement of ammonia by amine will significantly enhance the hygroscopicity of(NH4)2SO4aerosols. In addition, light extinction of AAS particles is a combined efect of both scattering and absorption under dry conditions, but is dominated by scattering under wet conditions.