Measurement of Expected Nucleation Precursor Species and 3–500-nm Diameter Particles at Mauna Loa Observatory, Hawaii

Abstract

Abstract Atmospheric measurements of expected homogeneous nucleation precursors and aerosols were made at the Mauna Loa Observatory, Hawaii, from 28 June to 27 July 1992. Large molecular clusters and gas phase species including sulfuric acid (H2SO4), methane sulfonic acid (MSA), and OH were measured with a mass spectrometer. Aerosol measurements consisted of ultrafine particle concentrations (∼3–4 nm diameter) and fine particle size distributions (15–500 nm diameter). The altitude of the observatory (average pressure 680 mb) and the presence of mountain–valley winds permitted sampling of both up- and downslope air. Downslope air was found to have the highest concentrations of MSA but low ultrafine concentrations, whereas, upslope air had the highest H2SO4 and ultrafine concentrations. Episodes of substantial increase in ultrafine particles were observed during periods of rapid increase in H2SO4 concentrations. Total aerosol surface area and H2SO4 concentrations had the strongest influence on ultrafine par...