CHANGES IN MOLECULAR-WEIGHT OF HUMIC SUBSTANCES IN THE GULF OF BOTHNIA

Humic substances were isolated in the brackish Gulf of Bothnia utilizi ng two techniques: ion exchange on DEAE-cellulose and hydrophobic inte raction on XAD-g resin. The salinity of the water resulted in differen t yields for the two adsorbents. With XAD-8 resin, 30-80% of the organ ic carbon was isolated, whereas 5-20% was isolated on the DEAE-cellulo se. The concentration of total organic carbon was rather constant but the concentration of humic substances decreased with increasing salini ty. Gel filtration was used to measure the homogeneity of the humic fr action. Humic substances isolated in December were more homogeneous th an those isolated in June, which indicates a degradation during the su mmer period which might be caused by photolysis or increased microbial degradation during the warm season.