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Disparate effects of DOM extracted from coastal seawaters and freshwaters on photodegradation of 2,4-Dihydroxybenzophenone

Author:
Wang, Jieqiong, Chen, Jingwen, Qiao, Xianliang, Zhang, Ya-nan, Uddin, Misbah, Guo, Zhongyu
Source:
Water research 2019 v.151 pp. 280-287
ISSN:
0043-1354
Subject:
absorption, coastal water, dissolved organic matter, hydroxyl radicals, models, moieties, photobleaching, photolysis, pollutants, singlet oxygen
Abstract:
Dissolved organic matter (DOM) plays an important role in degradation of organic pollutants by photochemically-produced reactive intermediates (RIs), such as excited triplet-states of DOM (3DOM*), singlet oxygen (1O2) and hydroxyl radical (·OH). However, it is not clear whether DOM extracted from coastal seawaters (CS-DOM) and DOM derived from freshwaters (FW-DOM) exhibit similar effects on photodegradation of organic micropollutants. Herein, 2,4-dihydroxybenzophenone (BP-1) was adopted as a model compound to probe the effects of different DOM on photodegradation kinetics of organic micropollutants. Results show that the CS-DOM promotes the photodegradation of BP-1 mainly via the pathway involving 3DOM*; while 3DOM*, 1O2 and ·OH are responsible for BP-1 photodegradation in the presence of the FW-DOM. Compared with the FW-DOM, the CS-DOM undergoes more photobleaching, and contains less aromatic C=C and C=O functional groups. Although 3DOM* formation quantum yields for the CS-DOM are relatively higher than those for the FW-DOM, the CS-DOM has lower rates of light absorption, leading to lower steady-state RI concentrations for the CS-DOM. BP-1 photodegradation in the presence of the CS-DOM is faster than in the presence of the FW-DOM, due to higher second-order reaction rate constants between BP-1 and CS-3DOM* and fewer antioxidants contained in the CS-DOM.