Measurement of expected nucleation precursor species and 3-500-nm diameter particles at Mauna Loa Observatory, Hawaii

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. It is concluded that for the conditions at Mauna Loa, H₂SO₄ was a vapor precursor of the newly formed particles, and MSA contributed little to new particle formation. -from Authors