A continuous flow streamwise thermal gradientcloud condensation nuclei(CCN)counter with anaerosol focusing and a laser-charge-coupled device(CCD)camera detector system was developed here.The countingperformance of the...A continuous flow streamwise thermal gradientcloud condensation nuclei(CCN)counter with anaerosol focusing and a laser-charge-coupled device(CCD)camera detector system was developed here.The countingperformance of the laser-CCD camera detector system wasevaluated by comparing its measured number concentrationswith those measured with a condensation particlecounter(CPC)using polystyrene latex(PSL)and NaClparticles of varying sizes.The CCD camera parameters(e.g.brightness,gain,gamma,and exposure time)wereoptimized to detect moving particles in the sensing volumeand to provide the best image to count them.The CCNcounter worked well in the particle number concentrationrange of 0.6-8000#·cm^(-3)and the minimum detectablesize was found to be 0.5μm.The supersaturation in theCCN counter with varying temperature difference wasdetermined by using size-selected sodium chloride particlesbased on Köhler equation.The developed CCNcounter was applied to investigate CCN activity ofatmospheric ultrafine particles at 0.5%supersaturation.Data showed that CCN activity increased with increasingparticle size and that the higher CCN activation forultrafine particles occurred in the afternoon,suggesting thesignificant existence of hygroscopic or soluble species inphotochemically-produced ultrafine particles.展开更多
基金The research described in this paper was supported by the National Research Foundation of Korea(NRF)Grant Funded by the Korean Government(MEST)(NRF-2011-0015548 and NRF-2010-013-D00034)。
文摘A continuous flow streamwise thermal gradientcloud condensation nuclei(CCN)counter with anaerosol focusing and a laser-charge-coupled device(CCD)camera detector system was developed here.The countingperformance of the laser-CCD camera detector system wasevaluated by comparing its measured number concentrationswith those measured with a condensation particlecounter(CPC)using polystyrene latex(PSL)and NaClparticles of varying sizes.The CCD camera parameters(e.g.brightness,gain,gamma,and exposure time)wereoptimized to detect moving particles in the sensing volumeand to provide the best image to count them.The CCNcounter worked well in the particle number concentrationrange of 0.6-8000#·cm^(-3)and the minimum detectablesize was found to be 0.5μm.The supersaturation in theCCN counter with varying temperature difference wasdetermined by using size-selected sodium chloride particlesbased on Köhler equation.The developed CCNcounter was applied to investigate CCN activity ofatmospheric ultrafine particles at 0.5%supersaturation.Data showed that CCN activity increased with increasingparticle size and that the higher CCN activation forultrafine particles occurred in the afternoon,suggesting thesignificant existence of hygroscopic or soluble species inphotochemically-produced ultrafine particles.
