Abstract
Dissolved organic matter (DOM) in Lake Unmun (Korea) and its two inflowing rivers was fractionated using three resin adsorbents (XAD-8 resin, macroporous cation and anion exchange resins) into five classes : aquatic humic substances (hydrophobic acids), hydrophobic neutrals, hydrophilic acids, bases, and hydrophilic neutrals. The characteristics of DOM were investigated by evaluating DOM fraction distribution, ultraviolet ray absorbance of DOM fractions (UV absorbance at 260nm), and molecular size distribution of DOM. Aquatic humic substances (AHS) and hydrophilic acids (HiA) were found to be predominant in both lake and river waters. In particular, AHS were greater in percentage fraction than HiA. The UV to dissolved organic carbon (DOC) ratio (UV/DOC ratio) of AHS was two times higher than that of HiA. The UV/DOC ratios of the total DOM, AHS and HiA were 12.9-32.8, 7.2-29.4 and 5.3-17.1 [m ABS cm-1·l·g C-1], respectively. The molecular weight distribution of the lake water DOM was determined by high-pressure size exclusion chromatography and found to exhibit a relatively narrow size range and low weight-averaged molecular weights ranging from 1,010 to 1,110 g·mole-1.
