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Atmospheric degradation of a semivolatile aerosol-borne pesticide

Reaction of OH with pyrifenox (an oxime-ether) adsorbed on SiO2
: Palm, W.-U.; Elend, M.; Krüger, H.-U.; Zetzsch, C.


Chemosphere 38 (1999), Nr.6, S.1241-1252
ISSN: 0045-6535
ISSN: 0366-7111
Fraunhofer ITA ( ITEM) ()
pesticide; atmosphere

The reactivity of both isomers (Z and E) of pyrifenox (2',4'-dichloro-2-(3-pyridyl)acetophenone (E,Z)-O-methyloxime), adsorbed on quartz-aerosol as an inert carrier, against OH radicals from the gas-phase was investigated in a smog chamber (2400 l) at T=299 K and 50% rel. humidity. OH-radicals were produced in the dark using hydrazine/ozone and peroxynitric acid/NO and by photolysis using methyl nitrite, hydrogen peroxide, ozone and nitrogen dioxide as OH-precursors. OH-radical concentrations (...) were determined from the simulataneous consumption of up to 6 reference compounds with well-known OH-rate constants. Using methyl nitrite, nitrogen dioxide and peroxynitric acid as OH-precursors the OH-rate constant at T=299 K for pyrifenox was found to be identical for both isomers.