TY - CHAP

T1 - Influence of clouds on the photochemical degradation in aqueous phase - I

T2 - Wasser 2008 - Jahrestagung

AU - Palm, Wolf-Ulrich

AU - Meyer-Grünefeld, Maren

AU - Ruck, Wolfgang

PY - 2008

Y1 - 2008

N2 - In the past detailed investigations of photochemical degradation reactions of pesticidesin aqueous solution were performed[1]. Necessary parameters to determine thedegradation rate constant, kp, are well known and models are available andelaborated[2). Hence, with respect to the importance of this degradation pathway in theenvironment, determination of the quantum yield in aqueous solution as a mainparameter is regulated by law in the authorization process of pesticides. However, onthe one hand, due to the comparability of the photochemical degradation with respect tolatitude and time and, on the other hand, due to the uncertainty with respect to cloudyscenarios[31, lifetimes are calculated usually for cloud free and clear days almost alwaysin summer using quantum yields and uv-spectra obtained in the laboratory. [2]Furthermore, experiments to investigate the decrease in kp of organic compounds suchas pesticides in aqueous solution by clouds (i.e. diurnal variations) and the comparisonwith suitable models were seldom performed.Within a project to investigate the influence of clouds on the photochemical degradationin aqueous phase at highly different sites in Brazil and Germany with respect tometeorology (and therefore environmental conditions) a suitable model compound to beused as an actinometer was necessary. In addition, for reasons of practical relevanceand to be able to transfer results, the actinometer had to be a pesticide.A method was developed using the herbicide metamitron[4] as a superb actinometer dueto fundamental chemical, photochemical and analytical properties in the aqueous phase.New results with respect to the photochemical reaction and properties obtained in thelaboratory and the application of metamitron as actinometer are presented on the poster

AB - In the past detailed investigations of photochemical degradation reactions of pesticidesin aqueous solution were performed[1]. Necessary parameters to determine thedegradation rate constant, kp, are well known and models are available andelaborated[2). Hence, with respect to the importance of this degradation pathway in theenvironment, determination of the quantum yield in aqueous solution as a mainparameter is regulated by law in the authorization process of pesticides. However, onthe one hand, due to the comparability of the photochemical degradation with respect tolatitude and time and, on the other hand, due to the uncertainty with respect to cloudyscenarios[31, lifetimes are calculated usually for cloud free and clear days almost alwaysin summer using quantum yields and uv-spectra obtained in the laboratory. [2]Furthermore, experiments to investigate the decrease in kp of organic compounds suchas pesticides in aqueous solution by clouds (i.e. diurnal variations) and the comparisonwith suitable models were seldom performed.Within a project to investigate the influence of clouds on the photochemical degradationin aqueous phase at highly different sites in Brazil and Germany with respect tometeorology (and therefore environmental conditions) a suitable model compound to beused as an actinometer was necessary. In addition, for reasons of practical relevanceand to be able to transfer results, the actinometer had to be a pesticide.A method was developed using the herbicide metamitron[4] as a superb actinometer dueto fundamental chemical, photochemical and analytical properties in the aqueous phase.New results with respect to the photochemical reaction and properties obtained in thelaboratory and the application of metamitron as actinometer are presented on the poster

KW - Chemistry

M3 - Article in conference proceedings

SN - 978-3-936028-51-5

SP - 190

EP - 194

BT - Wasserchemische Gesellschaft, FG in der GDCh

PB - GDCh, Wasserchemische Gesellschaft

Y2 - 28 April 2008 through 30 April 2008

ER -