Study of humic-like substances in fog and interstitial aerosol by size-exclusion chromatography and capillary electrophoresis

Recently, there have been implications that the bulk of the organic carbon in the atmospheric aerosol and fog is contained in an "air polymer" whose c hemical nature is poorly understood. Since several properties (e.g. acidity , UV-VIS absorbance, fluorescence) of this polymer were found to be very si milar to those of humic substances the term humic-like substances (HULIS) w as proposed. In this work size-exclusion chromatography and capillary elect rophoresis are used to obtain new information about some properties of the HULIS found in fog water and aqueous extract of interstitial aerosol. Reten tion and migration behaviour as well as mass spectra are investigated and c ompared to those of reference humic substances. The capillary electrophores is is applied for the determination of the range of protonation constants o f the HULIS, as well. Scavenging ratio for the HULIS is calculated and foun d to be about the same as those of ammonium and sulphate. The results imply that such compounds may play a role in cloud condensation. (C) 2000 Elsevi er Science Ltd. All rights reserved.