AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
O3-initiated Heterogeneous Oxidation of Fatty Acids
Chunbo Leng, Guang Zeng, Hai Pham, Yunhong Zhang, YONG LIU, University of Colorado Denver
Abstract Number: 36 Working Group: Aerosol Chemistry
Abstract Despite recent extensive studies towards heterogeneous oxidation of unsaturated organics initiated by ozone, our current knowledge about effects of ambient temperature, physical state, relative humidity, ozone concentration, particle size, and structural isomerism on chemical transformation of organic aerosols, in particular reaction kinetics is still scarce. In this work, we used ATR-IR flow reactor and a variety of unsaturated fatty acids including oleic acid, linoleic acid, linolenic acid and erucic acid as proxies for atmospheric unsaturated organics to investigate their heterogeneous oxidation by ozone, aiming at better understanding the effects of ambient temperature, physical state, relative humidity, ozone concentration, particle size, and structural isomerism on the heterogeneous reaction and overall reactive uptake. In the work, pseudo-first order rate constants and overall reactive uptake coefficients were acquired from absorbance changes in peak located near 1710 cm-1 which can be assigned to C=O in carboxylic acid. Experimental results showed that heterogeneous loss of ozone onto fatty acids could have very strong temperature dependence, depending on species and their physical states. Particle size and ozone concentration appeared to play important roles in reaction kinetics; in contrast, the effects of relative humidity and structural isomerism were seemingly less significant. Results also showed that heterogeneous reactions proceeded via Langmuir-Hinshelwood mechanism.