Photodegradation of hydroxyfluorenes in ice and water:A comparison of kinetics, effects of water constituents, and phototransformation by-products

Ge, L. and Cao, S. and Halsall, C. and Niu, J. and Bai, D. and He, G. and Zhang, P. and Ma, H. (2023) Photodegradation of hydroxyfluorenes in ice and water:A comparison of kinetics, effects of water constituents, and phototransformation by-products. Journal of Environmental Sciences (China), 124. pp. 139-145.

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Abstract

The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry. Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs, 2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL), which are newly recognized contaminants in the wider environment including colder regions. Interestingly, their photodegradation kinetics were clearly influenced by whether they reside in ice or water. Under the same simulated solar irradiation (λ > 290 nm), OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing. Furthermore, the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in ‘seawater’ ice (k = (11.4 ± 1.0) × 10−2 min−1) followed by ‘pure-water’ ice ((8.7 ± 0.4) × 10−2 min−1) and ‘freshwater’ ice ((8.0 ± 0.7) × 10−2 min−1). The presence of dissolved constituents (specifically Cl−, NO3−, Fe(III) and humic acid) influences the phototransformation kinetics, either enhancing or suppressing phototransformation, but this is based on the quantity of the constituent present in the matrixes, the specific OHFL isomer and the matrix type (e.g., ice or aqueous solution). Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry. Ice phototransformation exhibited fewer by-products and ‘simpler’ pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice. These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice.

Item Type:
Journal Article
Journal or Publication Title:
Journal of Environmental Sciences (China)
Additional Information:
This is the author’s version of a work that was accepted for publication in Journal of Environmental Sciences. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Environmental Sciences, 124, 2022 DOI: 10.1016/j.jes.2021.11.002
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2300/2305
Subjects:
ID Code:
166220
Deposited By:
Deposited On:
16 Feb 2022 15:25
Refereed?:
Yes
Published?:
Published
Last Modified:
04 May 2022 02:43