Research
Tropospheric Ozone Concentrations and Meteorological Parameters
- In this study the Environment SA 41 m UV photometric ozone analyzer was used to determine tropospheric ozone levels. The concentrations were correlated to meteorological parameters. The daily and hourly ozone concentrations ranged between 21.07 and 50.02 ppb, and 0.08 and 96.91 respectively for Marikana; and between 4.03 and 52.04 ppb, and 6.31 and 61.76 ppb for Botsalano Game reserve. The measured hourly ozone concentrations were below the one hour ozone standard for South Africa and the World Health Organization (WHO). An ‘ozone bell’ behavior with daily diurnal peaking between 12:00 and 16:00 hours and a low from evening to early morning was observed; thus suggesting anthropogenic activities as a possible source of tropospheric ozone in Botsalano and Marikana. A negative correlation between ozone and relative humidity, and a positive correlation between ozone and temperature, and wind speed was also observed at the two study sites.
Seasonal Variations of Tropospheric Ozone Concentrations
This study shows strong seasonality of ground level ozone concentrations with spring (September and October) maximum and winter (May and June) minimum levels. The levels were observed in decreasing order per season as: spring>summer>autumn>winter. The Johannesburg ozone levels were much lower than Botsalano and Marikana levels. The monthly levels for the 2007 to 2008 period were determined in order of decreasing abundance as Marikana (21.07 – 50.02 ppb), Botsalano (28.17 – 37.94 ppb), Buccleuch (2.03 – 23.42 ppb), Delta (5.76 – 17.32 ppb) and Newtown (1.73 – 17.19 ppb). The precursors of ozone (NOx, NO2, and NO) also showed peaks in winter (May-June). Anti- correlation of ozone and its precursors (NOx, NO2, and NO) were also observed. The authors also conclude that the formation of ozone in Johannesburg occurs under the VOC-sensitive regime, and that the possible sources of ozone in the city are vehicular and industrial and businesses.
