Abstract
The rate of uptake of ozone on various mineral dust surrogates, expressed as uptake coefficient γ, has been studied employing a Knudsen flow reactor. Experiments were performed at T = 298 ± 2 K on substrates of kaolinite, CaCO~3~, natural limestone, Saharan dust, and Arizona test dust. Initially, the uptake coefficients have been calculated on the basis of the geometric surface area of the powder samples. Both initial and steady‐state uptake coefficients γ~0~ and γ~ss~ were found very similar for all the examined substrates. In addition, additional uptake experiments on marble sample have shown that γ~0~ and γ~ss~ may be overestimated between a factor of 50 and 100, respectively. Based on these considerations, we proposed initial and steady‐state uptake values of the order of 10^−4^ and 10^−5^, respectively. On kaolinite, the uptake coefficient decreased with increasing O~3~ residence time τ~g~ thus indicating a complex mechanism. In contrast, γ decreased and became independent of τ~g~ at long residence time after long exposure to O~3~. For all uptake experiments the disappearance of O~3~ was accompanied by the formation of O~2~. The different mineral dust surrogates may be more accurately distinguished by their time‐dependent O~2~ yield r(t) rather than the magnitude of γ. The heterogeneous reaction of O~3~ on mineral dust has been found to be noncatalytic and of limited importance in the atmosphere. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 407–419, 2006