Development of a Portable Aerosol Collector and Spectrometer (PACS)

Area of Science:

• Atmospheric Science
• Environmental Monitoring
• Instrument Development

Background:

• Accurate characterization of airborne aerosols is crucial for understanding climate, air quality, and health impacts.
• Existing methods often lack the capability for simultaneous, continuous measurement of multiple aerosol properties across a wide size range.
• There is a need for portable instrumentation for versatile aerosol sampling and analysis.

Purpose of the Study:

• To develop and validate a Portable Aerosol Collector and Spectrometer (PACS) for comprehensive airborne aerosol characterization.
• To enable continuous measurement of particle number, surface area, and mass concentrations from 10 nm to 10 µm.
• To facilitate simultaneous chemical analysis of collected aerosol samples.

Main Methods:

• The PACS instrument integrates a six-stage particle size selector (impactor and diffusion stages), a condensation particle counter for number concentration, and a photometer for mass concentration.
• Particle penetration and collection efficiency were experimentally determined for each stage.
• A data inversion algorithm employing adaptive grid-search and constrained linear least-square fitting was used to determine aerosol size distributions.

Main Results:

• The PACS demonstrated effective particle size selection, with measured 50% cutoff diameters closely matching design specifications.
• Low pressure drop across stages allowed operation with portable air pumps.
• The instrument achieved good agreement for aerosol size distributions, with R² values from 0.90 to 1.00 when assuming standard density spheres.
• Fitted number and mass concentration biases remained within ±10% despite variations in particle density and shape.

Conclusions:

• The developed Portable Aerosol Collector and Spectrometer (PACS) is a novel instrument capable of simultaneously assessing airborne aerosol composition and concentration by number, surface area, and mass.
• PACS provides a versatile and portable solution for detailed aerosol characterization over an extensive size range.
• The instrument's performance is robust regarding uncertainties in particle density and shape for number and mass concentration measurements.