(136e) Optimization of Laminar Flow Ultrafine Condensation Particle Counters for the Enhanced Detection of 1 Nanometer Condensation Nuclei

Atmospheric aerosols influence climate and climate change on local to global scales by affecting the atmospheric radiation balance directly through scattering and absorbing incoming solar radiation and indirectly as cloud condensation nuclei.  New particle formation (NPF) by photochemical reactions of gas-phase precursors greatly increases the number concentrations of atmospheric aerosols, and therefore their impact on climate.  Although methods for measuring sizes and concentrations of newly formed particles of diameter greater than 3 nm are well established, measurements of nanoparticles smaller than this are needed to constrain nucleation rates and to better understand nucleation mechanisms.  A diethylene glycol-based laminar flow ultrafine condensation particle counter (DEG-UCPC) has recently been developed for sub-2 nm detection, enabling the detection of negatively charged sodium chloride with an efficiency of 2% at a mobility diameter of 1.16 nm.  By increasing the aerosol flow rate and operating temperature difference in the DEG-UCPC, this detection efficiency has been increased by a factor of 10 at the same particle size without nucleation of the working fluid.  Similar non-destructive operating modifications to a commercial butanol-based CPC (TSI 3025A) have increased the detection efficiency of 1.68 nm mobility diameter particles from less than 0.5% to over 35% for negatively charged sodium chloride.  Laboratory characterization of CPC detection efficiency as a function of particle size, charge, and composition will be presented for both instruments.  Ambient size distributions acquired with this modified DEG-UCPC will also be presented.