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Environ Sci Technol. 2019 May 21;53(10):5778-5786. doi: 10.1021/acs.est.9b00538. Epub 2019 May 3.

Mechanistic Insight into the Effect of Metal Ions on Photogeneration of Reactive Species from Dissolved Organic Matter.

Author information

1
School of Environmental Science and Engineering , Huazhong University of Science and Technology , Wuhan , Hubei 430074 , People's Republic of China.
2
Program for the Environment and Sustainability, Department of Environmental and Occupational Health, School of Public Health , Texas A&M University , College Station , Texas 77843 , United States.
3
University of Massachusetts Dartmouth , 285 Old Westport Road , North Dartmouth , Massachusetts 02747-2300 , United States.

Abstract

The photogeneration of reactive species (RS) from dissolved organic matter (DOM) exhibits a great impact on the attenuation of pollutants in natural waters. However, the effect of metal ions on the photogeneration of excited triplet-state DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radical (OH) by effluent organic matter (EfOM), fulvic acid (FA), and humic acid (HA) is poorly understood. Here, we provided the first evidence that the quenching of 3DOM* was positively correlated with the complexation capacity of metal ions with DOM. Generally, the paramagnetic metal ions (Cr3+, Mn2+, Fe3+, and Cu2+) exhibited higher conditional stability constants (log KML) with DOM and stronger inhibition for RS than the others (Mg2+, Ca2+, Al3+, and Zn2+). For DOM of different sources, the metal binding capacity increased in the order of EfOM < HA < FA and the humic substances were more susceptible to metal ions. The inhibition was attributed to both static and dynamic quenching of 3DOM* by metal ions. The dynamic quenching rate constants of metal ions for 3DOM* were estimated as ∼109 M-1 s-1, which was positively related to the corresponding log KML. These findings highlight crucial links between metal-DOM complexation and 3DOM* quenching and, consequently, the inhibition of RS.

PMID:
31021612
DOI:
10.1021/acs.est.9b00538

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