Composition and spectral characteristics of ambient aerosol at Mauna Loa Observatory

The spectral and the chemical characteristics of ambient aerosol at Mauna Loa Observatory (Hawaii) were determined in aerosol particles continuously sampled during an 8-day period in August 1986. During this period, the chemical species in the ambient aerosol varied considerably. During the major fraction of the sampling period, the aerosol was acidic due to predominance of (NH4)3H(SO4)2, NH4HSO4, or H2SO4. Aerosol samples showed much higher absorbance at 9.1 microns than at 10.6 microns. Moreover, changes in chemical composition from the neutral (NH4)2SO4 aerosol to more acidic sulphate forms were accompanied by substantial changes in the samples' absorbance at 9.1 microns (with lesser changes in the 10.6-micron absorptions).