Molecularchanges in dissolved organic matter during photodegradation

The high-performance-size exclusion chromatograph (HPSEC) separated dissolved organic matter (DOM) of lake Biwa andriver water into three major peaks of apparent molecular weight of 1200 (peakl) 800 (peak2) and 300 Da (peak3). Mimic pbotodegradation experiments on DOM in Lake Biwa showed that solar irradiation caused a decreaseinthe both UV and fluorescence intenslty. The decreaslng trends of the ratio between peak area of peak2 and peak3 With photodegradtion process indicated that large photo sensitive molecules are fragmented into small molecules dming photodegradation, The flrStl0rder reaction kinetics was applied toanalyze the photodegradation of DOM. Two-step photodegradation was suggested forthefluorescent DOM with different rate constant values, Results obtained in the present study suggested that fluorescent DOM is susceptible to photodegradation and fragmented to relatively smaller size molecllles with the progress of photodegradation,