An Automated Size and Time-resolved Aerosol Collector (STAC) Platform Integrated Sensors to Study Vertical Profile of Aerosol

Atmospheric particles affect human health, climate, and ecosystem but assessing their impacts is still challenging. Part of that is because of the limited understanding of the size-dependence of particle properties and variation of these properties along with the vertical profile under different environmental conditions. Thus, we present an automated Size and Time-resolved Aerosol Collector (STAC) platform integrated sensors, which has been deployed on the Atmospheric Radiation Measurement’s (ARM) tethered balloon system (TBS) in several ARM campaigns in Oliktok Point (Alaska), Southern Great Plains (Oklahoma), and Crested Butte (Colorado). The STAC platform is loaded with an array of 4-stages cascade impactors to collect aerosol particles within the different aerodynamic size ranges for various atmospheric research, such as the vertical profile of size-resolved aerosol chemical composition and multi-phase chemistry at up to 20 sampling points per flight. Time-resolved sampling facilitates the study of the evolution of particles in the atmosphere. The battery-powered, lightweight automated size- and time-resolved sampling system is ideal for unmanned aerial systems (e.g., TBS) and aircraft sampling. Currently, the STAC platform is integrated with a temperature and relative humidity sensor and a pressure sensor to monitor ambient conditions, an optical particle counter to measure the aerosol size distribution, and a micro-aethalometer to measure black carbon mass concentration and light-absorption coefficient of aerosols at 375, 470, 528, 625, and 880 nm wavelength every second to investigate the dependence of aerosol properties on ambient conditions. Experimentally derived 50% cut-off sizes of each stage (stage A to D) for a standard impactor are about 2.3, 0.62, 0.42, and 0.12 μm. The impactor is adaptable to collect smaller particles with an additional replaceable Stage E with a 50% cut-off size of 0.07 μm. At each stage, we can load three different types of substrates to collect ambient aerosols for multi-modal offline 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), and hygroscopic and ice nucleation properties.