Characterization of River Natural Organic Matter by High-Performance Size Exclusion Chromatography

The molecular weight of natural organic matter from the Yeongsan and Seomjin Rivers and the discharge from the wastewater treatment plants were analyzed for seasonal characteristics by high-performance size exclusion chromatography. The distribution of molecular weights demonstrated relationships with microbial activity and seasonal variations with temperature. Dissolved organic carbon and total organic carbon for the Seomjin River were from 1.6 to 3.1mgL(-1); for the Yeongsan River system, these parameters were between 2.0 and 8.0mgL(-1). There were no significant differences between upstream and downstream organic matter. The biochemical oxygen demand (0.8-2.5mgL(-1)) for the Seomjin River was less than the chemical oxygen demand (2.9-5.0mgL(-1)). Similarly, the biochemical oxygen demand (0.9-4.6mgL(-1)) for the Yeongsan River was lower than the chemical oxygen demand (3.8-10.6mgL(-1)). The molecular weight of aromatic compounds increased as the water temperature decreased in October, whereas the molecular weights of proteins decreased as the water temperature increased. These results suggest that as microbial activity increased, natural organic matter with a smaller molecular weight may be employed as an energy source by microorganisms. As a result, seasonal variation of the water temperature may influence the distribution of organic matter in the rivers based on molecular weight and microbial activity such that the smaller natural organic matter was more readily degraded by microorganisms.