Mobilization and transport of dissolved organic matter and its biological effects in acidified, humic freshwaters

摘要

This thesis examines some of the functional properties of dissolved organic material (DOM), and the effects of acidification and liming on its hydrophobic character. The dissolved organic material (DOM) of humic freshwaters is an important ecological factor in acidified waters. DOM in acidified, humic waters has been shown to have both positive and negative effects on macro-invertebrates. In this thesis, octanol solubility was used as a measure of the potential ability of DOM to be absorbed to or absorbed in biological systems. As pH decreased, more of the DOM becomes octanol soluble. The main part of the allochthonous dissolved organic matter, transported to a peat bog lake, came through hydraulic vents. There was no strong evidence supporting the hypothesis that octanol soluble material is mobilized at the land/water interface, when allochthonous dissolved organic material passes a pH and conductivity gradient, entering this humic lake. More of the DOM in the lake water was octanol soluble, compared to the water coming from the terrestrial environment through sub-surface flow. The results indicate that the amount and concentration of this hydrophobic fraction is dependent on the source of the parent material, the season, watershed characteristics, and the biological activity of the microbial community in the water. The results of the studies of a limed humic stream indicated that the quality of the particulate organic material was altered, presumably altering the food quality for benthic invertebrates. The overall effect on the benthic community was studied in 20 streams of different pH and humic content. The results showed that the species richness in acidified streams, with a pH less than 5.5, was higher than in streams with low or high concentrations. The relationship between humic content and species richness followed a second order polynomial function, with the maximum species richness occurring in streams with a colour of about 300 mg Pt/L. 126 refs