Showing papers by "Harald Saathoff published in 2001"

The loss of NO2, HNO3, NO3/N2O5, and HO2/HOONO2 on soot aerosol : A chamber and modeling study

Abstract: The heterogeneous loss of NO2, HNO3, NO3 / N205, and HO2/HO2NO2 on soot aerosol was investigated in a large aerosol chamber for interaction times of up to several days. By fitting a detailed model to the measured time pro- files of the trace gas concentrations in the presence / absence of soot aerosol, the following reaction probabilities have been deduced at 294 K and <10 ppm H20 (in parentheses: at 50% r.h.)' ¾(NO2) _< 4x 10-8; ¾(HNO3---NO2) _< 3x 10-7; ¾(NO3) _< 3x 10 -4 (_<10-3); ¾(N205, hydrolysis) = (4_+2)x10 -5 ((2+1)X10-4); ¾(N205, reduction) = (4+2)X10-6; ¾(HO2) < 10-2; ¾(HO2NO2) < 10 -5. These results were adopted in a series of box model calculations for four-day summer smog episodes, probing a wide range of NO emission rates. The 2 nd day ozone maxima were reduced up to 10 % in the presence of 20 #g m -3 soot aerosol, mainly due to the heterogeneous loss of HO2.