The use of the pulse height analyser ultrafine condensation particle counter (PHA-UCPC) technique applied to sizing of nucleation mode particles of differing chemical composition

摘要

A modified white-light pulse-height analyser (PHA) TSI 3025 ultra-fine condensation particle counter (UCPC) is often used to provide fast response of aerosol size distributions between 3 and 10nm since there is a monotonic link between initial aerosol size and nucleated droplet final size.The use of the PHA-UCPC for sizing nucleation mode particles depends on the droplet nucleation in the condenser chamber being some-what independent of particle composition.Laboratory characterization of the PHA-UCPC for a range of chemical compositions,thought to be involved in atmospheric aerosol nucleation and growth,are presented here.Ammonium sulphate,pinic acid,cis-pinonic acid,malonic acid and an iodine oxide were studied and their PHA-UCPC calibration kernels are presented.It was found that all species possessed significantly different PHA responses.The results suggest that,unless the nano-particle chemical composition is known,the the PHA-UCPC cannot be used for measurements of aerosol size distributions.However,the PHA-UCPC,if used in parallel with mobility size distribution measurements,can help elucidate nano-particle chemical composition.Using the combination of mobility size distributions and the PHA-UCPC response during a nucleation and growth event over the boreal forest indicates that new particle formation,in this region,is driven by condensation of organic vapours.