Nitrate-Induced Photolysis in Natural Waters:  Controls on Concentrations of Hydroxyl Radical Photo-Intermediates by Natural Scavenging Agents

The importance of the principal natural scavenging agents for hydroxyl radicals (•OH) was evaluated, and a general framework was developed to predict the significance of nitrate-induced, •OH-mediated degradation of aquatic contaminants. Rate constants for •OH scavenging by dissolved organic matter (...

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Bibliographic Details
Published in:Environmental science & technology 1998-10, Vol.32 (19), p.3004-3010
Main Authors: Brezonik, Patrick L, Fulkerson-Brekken, Jennifer
Format: Article
Language:English
Subjects:
ACETOCHLOR
ACETOCHLORE
ACETOCLOR
AGUA
Chemistry
Earth sciences
Earth, ocean, space
EAU
Exact sciences and technology
FOTOLISIS
FREE RADICALS
Geochemistry
Hydrology
Hydrology. Hydrogeology
Mineralogy
NITRATE
NITRATES
NITRATOS
PHOTOLYSE
PHOTOLYSIS
RADICAL LIBRE
RADICALES LIBRES
Silicates
WATER
Water geochemistry
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Summary:The importance of the principal natural scavenging agents for hydroxyl radicals (•OH) was evaluated, and a general framework was developed to predict the significance of nitrate-induced, •OH-mediated degradation of aquatic contaminants. Rate constants for •OH scavenging by dissolved organic matter (DOM) from five surface water sources were in a narrow range (2.3 ± 0.77 × 104 (mg of C/L)-1 s-1), which is similar to previously reported values and suggests that the importance of DOM as a •OH sink can be estimated simply from the dissolved organic carbon (DOC) concentration of a water. Scavenging of •OH by carbonate and bicarbonate is generally less important, but these ions can be the major cause of •OH scavenging in low DOC, high alkalinity waters. Use of the framework is illustrated by predicting levels of •OH and half-lives of the corn herbicide acetochlor in waters ranging from pristine to highly influenced by agricultural activities.
ISSN:0013-936X
1520-5851
DOI:10.1021/es9802908