Seasonal influences on surface ozone variability in continental South Africa and implications for air quality

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http://hdl.handle.net/10138/262542

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Laban , T L , van Zyl , P G , Beukes , J P , Vakkari , V , Jaars , K , Borduas-Dedekind , N , Josipovic , M , Thompson , A M , Kulmala , M & Laakso , L 2018 , ' Seasonal influences on surface ozone variability in continental South Africa and implications for air quality ' , Atmospheric Chemistry and Physics , vol. 18 , no. 20 , pp. 15491-15514 . https://doi.org/10.5194/acp-18-15491-2018

Title: Seasonal influences on surface ozone variability in continental South Africa and implications for air quality
Author: Laban, Tracey Leah; van Zyl, Pieter Gideon; Beukes, Johan Paul; Vakkari, Ville; Jaars, Kerneels; Borduas-Dedekind, Nadine; Josipovic, Miroslav; Thompson, Anne Mee; Kulmala, Markku; Laakso, Lauri
Contributor: University of Helsinki, Department of Physics
Date: 2018-10-29
Language: eng
Number of pages: 24
Belongs to series: Atmospheric Chemistry and Physics
ISSN: 1680-7316
URI: http://hdl.handle.net/10138/262542
Abstract: Although elevated surface ozone (O-3) concentrations are observed in many areas within southern Africa, few studies have investigated the regional atmospheric chemistry and dominant atmospheric processes driving surface O-3 formation in this region. Therefore, an assessment of comprehensive continuous surfaceO(3) measurements performed at four sites in continental South Africa was conducted. The regional O-3 problem was evident, with O-3 concentrations regularly exceeding the South African air quality standard limit, while O-3 levels were higher compared to other background sites in the Southern Hemisphere. The temporal O-3 patterns observed at the four sites resembled typical trends for O-3 in continental South Africa, with O-3 concentrations peaking in late winter and early spring. Increased O-3 concentrations in winter were indicative of increased emissions of O-3 precursors from household combustion and other low-level sources, while a spring maximum observed at all the sites was attributed to increased regional biomass burning. Source area maps of O-3 and CO indicated significantly higher O-3 and CO concentrations associated with air masses passing over a region with increased seasonal open biomass burning, which indicated CO associated with open biomass burning as a major source of O-3 in continental South Africa. A strong correlation between O-3 on CO was observed, while O-3 levels remained relatively constant or decreased with increasing NOx, which supports a VOC-limited regime. The instantaneous production rate of O-3 calculated at Welgegund indicated that similar to 40 % of O-3 production occurred in the VOC- limited regime. The relationship between O-3 and precursor species suggests that continental South Africa can be considered VOC limited, which can be attributed to high anthropogenic emissions of NOx in the interior of South Africa. The study indicated that the most effective emission control strategy to reduce 03 levels in continental South Africa should be CO and VOC reduction, mainly associated with household combustion and regional open biomass burning.
Subject: VOLATILE ORGANIC-COMPOUNDS
IMPACT ASSESSMENT PROJECT
BURNED-AREA PRODUCT
TROPOSPHERIC OZONE
FORMATION EVENTS
CARBON-MONOXIDE
TRACE GASES
SAVANNA
POLLUTION
TRENDS
114 Physical sciences
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