Heterogeneous Reactions of Nitric Acid and Dinitrogen Pentoxide on Mineral Dust Surfaces: A Knudsen Reactor Study

The heterogeneous reactions of nitric acid and dinitrogen pentoxide with various authentic dust, mineral and clay mineral surfaces has been investigated my means of the Knudsen reactor techique at room temperature. Authentic dust surfaces from the Saharan, the Chinese and the Arizona dust regions were used as substrates, as were the minerals and clay minerals: aluminium oxide, calcite, dolomite, feldspar; kaolinite, chlorite, illite, smectite, montmorillonite and palygorskite. The uptake of both trace gases was investigated at concentrations as low as 10^9 cm^-3 (HNO3) and 10^10 cm^-3 (N2O5) and found to be large and irreversible. For HNO3 uptake coefficients of the order of 0.1 werde determined. Uptake coefficients of N2O5 were between 0.02 and 0.001. Water was found to have some influence onto the uptake coefficient, though this depended on the substrate used. It was observed that diffusion into the pores of the sample bulk can be relevant for N2O5; this has to be considered in the calculation of the uptake coefficient. For HNO3 pore diffusion is unimportant. These results strongly suggest that mineral aerosol can redistribute nitrate from the gaseous to the particulate phase, modifying tropospheric photochemical cycles involving NOx and NOy.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2001

Author dc:creator

• Hanisch, Friedrich

Contributors dc:contributor

• Platt, Ulrich

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/1620

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:1620