Spatial and temporal assessment of gaseous pollutants in the Highveld of South Africa

Abstract

Diverse natural and anthropogenic activities in the Highveld of South Africa contribute to elevated levels of inorganic and organic gaseous pollutant species. The primary aims of this investigation were to determine spatial and temporal distributions of nitrogen dioxide (NO 2 ), sulphur dioxide (SO 2 ) and ozone (O 3 ), as well as benzene, toluene, ethylbenzene and xylene (BTEX) in this area. Sampling was conducted on a monthly basis for a year at eight strategically selected sites. The highest NO 2 , SO 2 and BTEX concentrations were measured at sites with significant local sources and/or sites impacted by more remote sources, as indicated by overlay back trajectories. O 3 concentrations were found to be lower at sites with high levels of NO 2 , SO 2 and BTEX. NO 2 and SO 2 peaked during winter, while O 3 peaked in spring. NO 2 and SO 2 temporal concentration variations were ascribed to differences in seasonal meteorological conditions, as well as additional sources in winter. The O 3 peak coincided with a seasonal CO peak, which was identified as an important precursor for O 3 formation. No distinct seasonal trend was observed for BTEX. The annual average concentrations for SO 2 , NO 2 , O 3 and benzene were below the South African annual standards at all sites.

A pilot study of gaseous pollutants' measurement (NO<sub>2</sub>, SO<sub>2</sub>, NH<sub>3</sub>, HNO<sub>3</sub> and O<sub>3</sub>) in Abidjan, Côte d'Ivoire: contribution to an overview of gaseous pollution in African cities

“…The average concentration of NO 2 at the Abidjan suburban site (7 ppb) is more than 2 times higher in comparison with that measured at the Amersfoort suburban site (2.5 and 2.9 ppb), respectively reported by Martins et al (2007) and Lourens et al (2011). The concentrations of SO 2 in Abidjan (2.2 ppb) are lower than those measured at Amersfoort suburban site in South Africa (2.8-5.5 ppb).…”

“…Measurements in Cotonou (Benin) have been performed at the crossroads of Dantokpa market, characterized by a large circulation of two-wheeled vehicles. Daily average concentrations range between 784.8 and 3662.4 µg m −3 (Mama et al, 2013). These concentrations are 39 to 183 times higher than the threshold value.…”

“…Eight studies were conducted on a daily basis. Average 24 h concentrations ranged from 0.1 µg m −3 along Juja Road in Nairobi (Kaboro, 2006) to 752 µg m −3 on the traffic site of Dantokpa market in Cotonou (Mama et al, 2013). Only three studies measuring NO 2 on a weekly scale were identified.…”

“…Through some research programs and projects such as AMMA (African Monsoon Multidisciplinary Analysis), IN-DAAF (International Network to study Deposition and Atmospheric chemistry in AFrica) and POLCA (POLlution des Capitales Africaines), some experimental studies have been carried out in certain African capitals and rural areas such as in Bamako, Dakar, Yaoundé, and Amersfoort (Adon et al, 2016;Conradie et al, 2016;Liousse and Galy-Lacaux, 2010;Lourens et al, 2011;Val et al, 2013). The DAC-CIWA (Dynamics-Aerosols-Chemistry-Clouds Interactions in West Africa) European program follows the framework of the above-mentioned programs.…”

Ambient aromatic hydrocarbon measurements at Welgegund, South Africa

“…For this reason, Africa is one of the least studied regions with respect to air quality (Laakso et al, 2006). South Africa has the largest industrialised economy in Africa and is known for its diverse anthropogenic pollutant sources, which include agriculture, metallurgical and mining operations, coal-fired power generation, petrochemical operations, coal dumps and transportation (Lourens et al, 2011). Unique meteorological conditions are prevalent in South Africa, which include relatively high atmospheric temperatures and solar radiation, which increases photochemical activity in the atmosphere, and dominant anticyclonic climatology and the presence of low-level inversion layers in winter cause trapping of pollutants (Tyson et al, 1996).…”