Automated size-exclusion-chromatography with UV- and organic
carbon detection (IR) was used for characterization, as described
in technical detail by Sachse et al. (2001). Four different
groups of DOC could be fractionated: polysaccharides, humic substances
(HSs), low molecular weight acids, and low molecular
weight substances. The polysaccharide fraction is high molecular
weight carbohydrates, which show no absorption in the UV range.
HSs include humic and fulvic acids and their building blocks, which
are UV active. Low molecular weight acids are defined as low
molecular weight carboxylic acids such as several metabolites in
biological and chemical processes. DOC in the low molecular
weight range after the low molecular weight acids peak was described
as other low molecular weight substances