A thesis submitted to the Faculty of Geography, Archaeology, and Environmental Studies University of the Witwatersrand, Johannesburg, in fulfilment of the requirements of the degree of Doctor of Philosophy. 2015.An imaging DOAS instrument, along with in situ trace-gas and aerosol instrumentation
was deployed on board a research aircraft over the Highveld
region of South Africa, to make regional-scale measurements of nitrogen dioxide
(NO2). The presence of a “hotspot” of NO2 over the Highveld is confirmed.
Case-study estimates of NO2 emission flux were made downwind of
a power station (10 tons.hr−1), a petrochemical plant (36 tons.hr−1) and the
entire Highveld region (395 tons.hr−1).
Vertical profile measurements were used to develop scenarios for a radiative
transfer sensitivity study. From this, suitable air-mass factors for the DOAS
measurements were determined. Comparisons between the airborne DOAS
and satellite instruments show a good agreement where the spatial scales of
the satellite ground pixels and the features in the two-dimensional trace-gas
distribution are matched.
A long-term record of satellite data was analysed. Analysis of radiative
transfer revealed a possible artefact in the adjacent positive and negative
trends evident on the Highveld. A correction to the satellite record for a
seasonal bias was made, and found to be important over biomass burning
regions in Angola and Zambia.
Spatial features in a seasonal model of the satellite record are shown to
correspond with known urban, industrial and biomass burning sources in the
region. Signatures of soil emissions are also detected
