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 chemical nature is poorly understood. Since several properties (e.g. acidity, UV–VIS absorbance, fluorescence) of this polymer were found to be very similar to those of humic substances the term humic-like substances (HULIS) was proposed. In this work size-exclusion chromatography and capillary electrophoresis are used to obtain new information about some properties of the HULIS found in fog water and aqueous extract of interstitial aerosol. Retention and migration behaviour as well as mass spectra are investigated and compared to those of reference humic substances. The capillary electrophoresis is applied for the determination of the range of protonation constants of the HULIS, as well. Scavenging ratio for the HULIS is calculated and found to be about the same as those of ammonium and sulphate. The results imply that such compounds may play a role in cloud condensation.