不同分子量天然溶解性有机物的光解行为研究

In this study, the photodegradation process of the size-fractionated dissolved organic matter (0.45μm~100kDa, 100 ~5 kDa, <5 kDa) at different light sources was investigated. Measurements of dissolved organic carbon (DOC) and UV254 absorbance showed that sunlight exposure led to the decrease of NOM in all the three fractions over a 6-days period of 6 h/d irradiation, and the presence of UVC light in natural sunlight can speed up NOM elimination. The parallel factor analysis (PARAFAC) of fluorescence excitation emission matrices (EEM) revealed the presence of three humic-like components (C1: UVA+UVC; C2: UVA+UVB; C3: UVC) in the NOM samples. In addition, the fluorescent components in large-size NOM fractions (>5 kDa) were not sensitive to sunlight exposure, and some of which increased upon sunlight exposure. However, the C1 and C2 in the small-size NOM fractions (<5 kDa) were much more susceptible to sunlight exposure, both of which decreased significantly after the 6-days incubation. But, the C3 components in all NOM fractions were found to be photo-produced. Also, the presence of the UVC light in sunlight can somewhat accelerate the elimination of C1 and C2 or decrease the generation of C3.