A Spectrometer For Measuring Particle Size Distributions In The Range Of3nm To10μm

A spectrometer combining electrical mobility sizing and aerodynamic sizing wasdeveloped to measure aerosol size distributions in the range of3nm to10|im. Itconsists of three instruments which cover different size ranges, respectively, i.e., a nanoscanning mobility particle sizer (NSMPS,3-60nm), a regular scanning mobilityparticle sizer (RSMPS,40-700nm), and an aerodynamic particle sizer (APS,550nm-10^m). Voltage and sheath flow in the NSMPS md RSMPS were supplied using twohome-built control boxes. A Lab VIEW program was developed for spectrometerautomatic operation. A linear inversion method was applied to correct particle multiplecharging effects and to integrate data from the three instruments into a wide-range sizedistribution. Experiments were conducted to compare distributions in the overlap sizeranges measured by three instruments. Good agreement between the NSMPS andRSMPS was achieved atfer correcting for the difference in counting efficiencies of thetwo particle counters. Aerodynamic size distributions reported by the APS wereconverted to mobility size distributions by applying an effective density method.Distributions measured by the RSMPS and APS were consistent in the overlap sizermge of550-700nm. A full spectrum in the size range of3nm to10jim wasdemonstrated by measuring aerosol generated using a mixture of different sizedpolystyrene latex spheres.The spectrometer was deployed for continuous atmospheric aerosol sizedistribution measurement during a field campaign in Shanghai (2012/12/4-2012/11/30). It was found that the pmlicle number concentration is mainly contributedby ultrafine particles. Particle number concentration in the range of10-100nm areotfen consistent with results reported in other cities, though during haze pollutionepisodes it was higher than those in other cities. Aerosol size distributions during cleandays and haze episodes are different from each other.