An Automated Size and Time-resolved Aerosol Collector (STAC) and Integrated Sensors for Atmospheric Studies

ZEZHEN CHENG, Andrey Liyu, Darielle Dexheimer, Nurun Nahar Lata, Casey Michael Longbottom, Gourihar Kulkarni, Fan Mei, Swarup China, Pacific Northwest National Laboratory

     Abstract Number: 318
     Working Group: Instrumentation and Methods

Abstract
Ambient aerosols affect human health, visibility, and climate. However, our understanding of these effects of aerosols is still limited, and part of that is because of the limited knowledge of the size-dependence of aerosols properties and variation of these properties along with the vertical profile under different environmental conditions. Therefore, we present a lightweight automated Size and Time-resolved Aerosol Collector (STAC), which has been deployed on the Atmospheric Radiation Measurement (ARM) tethered balloon system (TBS) in several ARM campaigns in Alaska and Southern Great Plains. The battery-powered STAC comprises a pump (5 lpm), latched solenoid valves, a single-board computer and circuit board to control valves, and a touch screen display to program the sampling. The STAC is integrated with temperature, pressure, relative humidity, and altitude sensors along with a portable optical particle spectrometer (POPS) and a condensation particle counter (CPC) to measure the aerosol size distribution and a mini- aethalometer to measure black carbon mass concentration every second. The STAC is loaded with an array of 4-stage cascade impactors to investigate the dependence of aerosol properties on ambient conditions. Experimentally derived 50% cut off size at 3 lpm of each stage (stage A to D) for a standard impactor are 5 μm, 2.5 μm, 0.42 μm, and 0.12 μm. The impactor is adaptable to collect smaller size particles with an additional Stage E with a 50% cutoff size of 0.07 μm. At each stage, we can load three substrates to collect ambient aerosols for multi-modal analysis to probe their physical (e.g., phase state and morphology), chemical (e.g., the elemental composition of individual particles and size-resolved chemical composition), and optical (light absorption and scattering) properties. The data ensemble from the various deployment provides the vertical profile of aerosol chemical composition and can aid the multi-phase chemistry and ice nucleation study.