A reactive condensation particle counter for measuring atmospherically relevant concentrations of sulfuric acid

Atmospheric aerosol particles play an important role in the Earth’s radiative balance through cloud droplet formation and scattering solar radiation. Numerous studies have shown that sulfuric acid-driven nucleation is a major global source of atmospheric aerosol particles and cloud condensation nuclei. However, measurements of sulfuric acid concentration are challenging to perform at the high spatial and temporal resolution needed to constrain climate models, as the current instruments are power-intensive, expensive, and heavy. This study presents the Sulfuric Acid Dimethylamine-Reactive Condensation Particle Counter (SAD-RCPC), a portable and more economical instrument to measure sulfuric acid vapor. Comparison of the SAD-RCPC with a chemical ionization mass spectrometer (CIMS) demonstrates that the SAD-RCPC can measure sulfuric acid concentrations from ∼4 × 10⁶ to 2 × 10⁹ molecules cm⁻³ in a particle-free sample gas with similar uncertainty as a CIMS. Methods are also proposed to improve the SAD-RCPC measurements for ambient air containing background aerosol particles with one method tested using ambient air samples. The SAD-RCPC could significantly decrease the barriers in measuring sulfuric acid and provide the higher resolution measurements needed to reduce uncertainty in climate models.