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An aerosol smog chamber for testing abiotic degradation of compounds with low volatility

: Behnke, W.; Nolting, F.; Zetzsch, C.

Greenhalgh, R.:
Pesticide science and biotechnology
Oxford: Blackwell Scientific Publications, 1987
Book Article
Fraunhofer ITA ( ITEM) ()
abiotischer Abbau; aerosol; Di-2-ethylhexyl-phtalat; Fe2 O3; Flugasche; heterogene Reaktion; Hydroxylradikal; SiO2; TiO2

An aerosol smog chamber facility is described, which is used to simulate the atmospheric, abiotic degradation of gaseous chemicals in the presence and absence of airborne aerosols, and also to simulate the degradation of condensed chemicals adsorbed on the aerosols. The aerosol materials SiO2, Fe2O3, coal fly ash and NaCl are investigated in a photosmog of sun-irradiated No sub x/hydrocarbon mixtures at the ppb level. The production of OH radicals (and Cl atoms in the presence of NaCl) in the gas-phase are computed from the degradation pattern of the hydrocarbons, and a heterogeneous degradation of hydrocarbons on the surfaces of irradiated TiO2 and Fe2O3 is detected. The kinetics for the consumption of a monolayer of the organic compound di (2-ethylhexyl)-phthalate on SiO2 and Fe2O3 by reaction with gas-phase OH is studied in detail. The rate constant of this second order process, 1.4x10 -11cm 3s-1, yields a halflife for di (2-ethylhexyl)phthalate of about 1 day at the global average concentration of OH in the troposphere. (ITA)