Photochemical and Nonphotochemical Transformations of Cysteine with Dissolved Organic Matter

Cysteine (Cys) plays numerous key roles in the biogeochemistry of natural waters. Despite its importance, a full assessment of Cys abiotic transformation kinetics, products and pathways under environmental conditions has not been conducted. This study is a mechanistic evaluation of the photochemical...

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Bibliographic Details
Published in:Environmental science & technology 2016-06, Vol.50 (12), p.6363-6373
Main Authors: Chu, Chiheng, Erickson, Paul R, Lundeen, Rachel A, Stamatelatos, Dimitrios, Alaimo, Peter J, Latch, Douglas E, McNeill, Kristopher
Format: Article
Language:English
Subjects:
Acidity
Analytical chemistry
Biogeochemistry
Cysteine
Dissolution
Kinetics
Photochemical Processes
Photochemistry
Photolysis
Reaction kinetics
Solutions
Sunlight
Temperature effects
Ultraviolet radiation
Water Pollutants, Chemical
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Summary:Cysteine (Cys) plays numerous key roles in the biogeochemistry of natural waters. Despite its importance, a full assessment of Cys abiotic transformation kinetics, products and pathways under environmental conditions has not been conducted. This study is a mechanistic evaluation of the photochemical and nonphotochemical (dark) transformations of Cys in solutions containing chromophoric dissolved organic matter (CDOM). The results show that Cys underwent abiotic transformations under both dark and irradiated conditions. Under dark conditions, the transformation rates of Cys were moderate and were highly pH- and temperature-dependent. Under UVA or natural sunlight irradiations, Cys transformation rates were enhanced by up to two orders of magnitude compared to rates under dark conditions. Product analysis indicated cystine and cysteine sulfinic acid were the major photooxidation products. In addition, this study provides an assessment of the contributions of singlet oxygen, hydroxyl radical, hydrogen peroxide, and triplet dissolved organic matter to the CDOM-sensitized photochemical oxidation of Cys. The results suggest that another unknown pathway was dominant in the CDOM-sensitized photodegradation of Cys, which will require further study to identify.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.6b01291