Effects Of PH On Quantum Yields Of Photo-induced Species Generated By Different Sources Of DOM

Dissolved organic matter(DOM)exists widely in surface waters.DOM can absorb sunlight to generate reactive photo-induced species(RPS),such as triplet excited DOM(3DOM*),singlet oxygen(1O2)and hydroxyl radicals(?OH).These RPS is important for degradation of organic micropollutants.It is known that variation in pH of natural waters can change the size,conformation and molecular weight of DOM.However,the relation between the variation in pH and photogeneration of RPS by DOM has been rarely investigated.Previous studies mainly bought DOM mainly from International Humic Substances Society or DOM reagent sales company.It has great challenge on the extraction of DOM from seawater because of salinity.Until now,there is little research on marine DOM.In this study,the effects of pH on the formation quantum yields of 3DOM*,1O2 and ?OH were investigated.DOM isolated from Yellow Sea(L-DOM)and two DOM purchased from international humic substances society(NAFA and SRHA)were adopted in the study.Characterized the UV spectra and fluorescence spectra,and adopted MATLAB combine PARAFAC to analysis the three dimensional fluorescence spectra.Molecular probes were employed to determine the formation of the RPS by DOM irradiated by simulated sunlight.Results revealed that the absorbance of L-DOM was significantly lower than the other two DOM,the absorbance of all DOM increased with pH increase;SRHA and NAFA mainly contain two kinds of fluorescence peak: Peak A: Humin-like and Peak B: Fulvic-like,while L-DOM contains Protein-like and simple aromatic protein.PARAFAC model analysis results show that SRHA and NAFA mainly contain component H1(320/460 nm)and component H2(260/470 nm),L-DOM contains component P1(290/300 nm).Results show the DOM has ability to photogenerate RPS,and RPS quantum yields of L-DOM are higher than those of NAFA and SRHA.Effects of pH on RPS quantum yields by different sources of DOM are different,and the influence of pH on RPS quantum yields of L-DOM was noticeable.The study is of importance to predict photodegradation kinetics of organic pollutants in water.