Effect of dissolved organic compounds on the photodegradation of the herbicide MCPA in aqueous solution.
This work shows that the addition of phenol and 2-propanol as model organic compounds significantly decreases the direct photolysis quantum yield of 4-chloro-2-methylphenoxyacetic acid (MCPA) upon UVB irradiation in aqueous solution. Laser flash photolysis data suggest that 2-propanol is able to decrease the formation of the MCPA excited states under irradiation. A decrease from 0.54 to 0.34 of the photolysis quantum yield of the anionic form of MCPA (which prevails over the undissociated one in surface waters) could have a considerable impact on the MCPA lifetime in ecosystems where the direct photolysis is the main phototransformation pathway. In surface water bodies where the direct photolysis has comparable kinetics as the reaction with OH, a decrease of the quantum yield would enhance the relative importance of the OH pathway, which yields considerably less toxic intermediates than the direct photolysis.
Vione
Davide
D
Dipartimento di Chimica Analitica, Università di Torino, Via P. Giuria 5, 10125 Torino, Italy. davide.vione@unito.it
Khanra
Swapan
S
Das
Radharani
R
Minero
Claudio
C
Maurino
Valter
V
Brigante
Marcello
M
Mailhot
Gilles
G
D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D010782:Photolysis / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D006540:Herbicides; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D008456:2-Methyl-4-chlorophenoxyacetic Acid