Hydroxyl radical (HO center dot) in natural waters plays a critical role in contaminant transformation and ecosystem health. In this study, the photogeneration and steady-state concentration of HO center dot in different aquatic environments (e.g., river and lake) along the middle-lower Yangtze region, China, were evaluated. The results showed that, compared to lake samples, the river waters were characterized by lower HO center dot photoformation rate (R-HO center dot) (5.10-11.69 x 10(-11) vs. 1.10-1.82 x 10(-10) M s(-1)) and steady-state HO center dot concentration ([HO center dot]) (1.76-3.11 x 10(-17) vs. 2.50-10.33 x 10(-17) M). The contribution of nitrate and nitrite to the total R-HO center dot in river waters was generally higher than that in lake waters, and photolysis of nitrite exhibited contributions 1-2 times higher than those of nitrate (0-25% vs. 0-9%) irrespective of sample types. As a result, the photosensitization by chromophoric dissolved organic matter (CDOM) contributed more than 70% of the total R-HO center dot for all samples except for River Ganjiang. [HO center dot] among all samples was positively correlated with dissolved organic carbon (DOC) concentration, and the DOC-normalized [HO center dot] was further related to the physicochemical properties of CDOM samples (e.g., aromaticity, humification, and molecular weight). The humic-like aromatic substances with low molecular weight were the controlling factors influencing [HO center dot] in the studied surface waters. The results contributed to a deeper understanding of behaviors and fate of aquatic DOMs in terms of HO center dot formation and contaminant attenuation.
WATER RESEARCH 卷: 176 文献号: 115774 出版年: JUN 2020