| Dissolved organic matter (DOM) widely exists as important soluble photoreactive materials in nature waters, and plays an important role in the ecological carbon cycling. DOM can generate a series of reactive species under light irradiation. 1O2 is one of important reactive species, which could exert a significant effect on the photolysis of many organic pollutants. Due to the complexity of water bodies, many factors, such as origin of DOM, pH, ion type and ionic strength, can affect the photochemical properties of DOM and its ability of generating 1O2. This study examined the photogeneration of 1O2 by DOM derived from different sources and the effect of coexisted ions on the photogeneration of 1O2 by DOM using photochemical experiments under simulated sunlight. Our findings can provide a better understanding of the photogeneration of 1O2 by DOM, and are helpful in the assessment of 1O2 contribution to the photo-transformation of pollutants.Infrared spectroscopy, UV-vis absorption and excitation-emission spectrum (EEMs) were applied to characterize the spectral characteristic of DOM originated from different sources. Simulate light experiments were conducted to measure the photogeneration of 1O2 in different DOM solutions. The results showed that the ability of producing’02 varied by the DOM origins. Abilities of photoinduced’02 by terrestrial DOM were stronger than those of aquatic originated DOM, which might be related to a relatively higher proportion of aromatic ketones and quinones in the structure of terrestrial DOM. The quantum yields of 1O2 ((?)1O2) from 27 kinds of soil-extracted DOM solution were different with significance, ranging from 0.207% to 2.49%, which were mainly due to the different compositions, pH and ionic strength of soil-extracted DOM.The effect of coexisted Fe3+, Cl- and pH on the ability of photoinduced 1O2 by DOM were investigated. Fe3+ and DOM formed complexes, and decreased the amount of the photoinduced ’02 by DOM. Using DOM analogues, it was indicated that Fe3+ could interact with aromatic ketones and quinones in DOM, which might account for the reduction in the quantum yields of 1O2 . Cl- promotedΦ1O2 for aquatic SRHA and PLFA, but Cl-inhibited Φ1O2 for terrestrial ESHA and SHA. The quantum yields of’02 increased with pH for terrestrial ESHA and SHA. Our findings suggest that Cl- and pH have different effects on DOM from different origins. |
