This study explores methods of characterising experimental and modelling data to see if trace gas measurements at the Cape Point GAW station could improve our understanding of sources from the continent. Selection criteria have been defined which make it possible to divide the samples into categories with predominant transport to Cape Point from one of four source regions: City (greater Cape Town); close rural (within about 150 km of Cape Point); distant rural (from 150 to about 500 km) and very distant rural covering the rest of southern Africa. For species with fairly uniform source such as radon or CO, this regional selection worked well, but for CO2 the respiration and photosynthesis cycle from very close vegetation usually overwhelmed the input from other sources. It was only in winter that the draw-down by wheat growing in the close rural zone was clearly evident in the Cape Point CO2 data.
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This report was originally puslished as Whittlestone, S, Kowalczyk, E, Brunke, E-G and Labuschagne, C, Source regions for CO2; at Cape Point assessed by modelling, 222Rn and meteorological data, Pretoria, South Africa, Southern Weather Service, 2009. Copyright South African Weather Service, 2009. Original publisher information here