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Journal of Environment Pollution and Human Health. 2018, 6(3), 96-109
DOI: 10.12691/jephh-6-3-3
Open AccessArticle

Trace Components, Tropospheric Interactions and Their Influence on Air Quality Composition over Southern Africa

Modise Wiston1, , Lesolle Director Sebitla1 and Godiraone Tatolo2

1Department of Physics, University of Botswana P/Bag UB00704, Gaborone, Botswana

2Department of Chemistry, University of Botswana P/Bag UB00704, Gaborone, Botswana

Pub. Date: July 10, 2018
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Cite this paper:
Modise Wiston, Lesolle Director Sebitla and Godiraone Tatolo. Trace Components, Tropospheric Interactions and Their Influence on Air Quality Composition over Southern Africa. Journal of Environment Pollution and Human Health. 2018; 6(3):96-109. doi: 10.12691/jephh-6-3-3

Abstract

Southern Africa is now a significant source of atmospheric pollution, having transformed from a rural to a developing region. The sub-continent is a source of atmospheric pollutants, including particulates, liquid and gaseous species produced from both natural and anthropogenic sources. Prominent hotspots for nitrogen oxide (NOx), particulate matter (PM) and biomass burning (BB) emissions can be seen on global maps and satellite retrievals. The seasonality of chemical transport mainly results from the seasonal swing of the Hadley circulation, the intertropical convergence zone (ITCZ) and subtropical westerlies along the transport pathways. The anticyclone induces strong subsidence motion, preventing vertical mixing of pollutants, hence capping high concentrations over land as they are transported across. This is manifested through temperature changes, cloud microphysical dynamics, atmospheric stability, the biosphere-atmosphere interactions as well as the oxidation processes. Once emitted chemical species show differences -either in the nearby or lower- and upper atmospheric levels in their dispersion, concentration, reaction rate, lifetime and/or oxidation capacity. Aerosols affect gas-phase chemistry via their light extinction potential and affect the photolysis rates of trace gases. Changes may occur through loss of gas-phase reactions, gas-to-particle partitioning or aerosol chemical modification. As part of efforts to understand chemical trace components and their atmospheric influence, this study highlights on the status of such species, their interactions and influence on air quality (AQ) composition over southern Africa. We propose an overview of gas- and particulate concentrations over several African localities, especially where daily WHO AQ threshold limits could be exceeded. The paper also aims to draw attention to African scientists and policy makers concerning pollution monitoring network in order to define national standards, to better control pollutant emissions and perhaps address impacts on AQ issues, pertaining to the growing African population and development.

Keywords:
trace components atmospheric composition interactions oxidation photolysis troposphere

Creative CommonsThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

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