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Casteel, Mpumalanga, South Africa, occupies a geographically significant position within a region heavily influenced by both natural and anthropogenic factors impacting air quality. Situated at approximately -24.7247° latitude and 31.0201° longitude, Casteel lies within the Highveld plateau, a relatively elevated area (averaging around 1,200 meters above sea level) characterized by undulating terrain and expansive grasslands. The surrounding landscape is dominated by savanna and bushveld, transitioning into more rugged terrain further afield. While not directly adjacent to major rivers, the region receives runoff that contributes to smaller streams and drainage systems, influencing local humidity. Crucially, Casteel’s location places it within the broader Mpumalanga province, a critical hub for South Africa’s coal mining and power generation industries. This proximity to the industrial belt, particularly the numerous coal-fired power stations clustered around the Witbank-Middelburg corridor, is the primary driver of air quality challenges. The urban–rural gradient around Casteel is relatively sharp; the town itself is a small settlement, quickly giving way to agricultural land and then to the extensive mining and industrial zones. The Highveld’s topography, combined with its elevation and prevailing wind patterns, can contribute to temperature inversions, trapping pollutants close to the ground, exacerbating air quality issues. The relatively flat nature of the plateau also limits dispersion of pollutants, further compounding the problem. The regional climate, characterized by distinct wet and dry seasons, also plays a role in pollutant transport and deposition.

Casteel’s air quality experiences a pronounced seasonal cycle dictated by Mpumalanga’s climate. The drier months, typically spanning from April to September, are often associated with poorer air quality. During this period, reduced rainfall and lower humidity contribute to a build-up of particulate matter and other pollutants released from industrial sources. Temperature inversions are more frequent during these cooler months, particularly in the mornings, trapping pollutants near the ground and creating stagnant air conditions. Wind speeds tend to be lower, further hindering pollutant dispersal. October to March marks the wetter season, bringing increased rainfall and higher humidity. These conditions generally lead to improved air quality as rainfall washes pollutants from the atmosphere and increased humidity can help to settle particulate matter. However, periods of intense rainfall can also lead to localised flooding and the release of pollutants from contaminated sites. Fog, common during the cooler months, can also exacerbate air quality issues by trapping pollutants. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the drier months, particularly during periods of stagnant air or fog. Limiting outdoor exertion and avoiding areas near industrial sources are advisable. During the wetter months, while air quality is generally better, vigilance is still required, especially following heavy rainfall events, as runoff can carry pollutants into the air. Maintaining indoor air quality through proper ventilation and air filtration is always recommended.