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Herenfa, nestled within the Chlef province of Algeria, occupies a geographically significant position approximately 120km west of Algiers. Located at coordinates 36.2453°N, 1.0458°E, the city sits on the plains bordering the Tell Atlas mountain range, a landscape characterized by rolling hills and fertile valleys. The terrain is predominantly flat, gradually ascending towards the mountains to the south, influencing local wind patterns and pollutant dispersion. Herenfa’s proximity to the Mediterranean Sea, roughly 50km to the north, introduces maritime influences, moderating temperatures but also potentially contributing to humidity and fog formation, which can trap pollutants. The surrounding area is a mix of agricultural land, primarily dedicated to cereal crops and olive groves, and smaller industrial zones focused on food processing and light manufacturing. This blend of activity introduces both biogenic and anthropogenic emissions. The urban-rural gradient is relatively sharp, with the city centre densely populated and transitioning quickly to agricultural fields. This proximity means pollutants generated within Herenfa can readily impact surrounding rural communities, and conversely, agricultural practices like seasonal burning can contribute to localised air quality issues. The city’s location within a natural bowl-shaped valley can exacerbate pollution build-up during periods of stagnant air.

Herenfa experiences a Mediterranean climate, with distinct wet and dry seasons heavily influencing air quality. Winter (November to February) often sees increased particulate matter concentrations due to residential heating using wood and coal, coupled with temperature inversions trapping pollutants near ground level. Fog, common during these months, further exacerbates this. Spring (March to May) brings a temporary improvement as rainfall washes away accumulated pollutants and vegetation begins to absorb some emissions. However, agricultural burning of crop residue can cause localised spikes in particulate matter. Summer (June to August) is typically the clearest period, with strong winds dispersing pollutants and high temperatures promoting atmospheric mixing. However, prolonged drought conditions can lead to dust storms originating from the Sahara, impacting air quality. Autumn (September to October) sees a return to more stagnant conditions, with decreasing rainfall and increasing use of heating systems. Sensitive individuals – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during winter and autumn months. Monitoring wind direction is crucial; winds from the south can bring Saharan dust, while calm conditions exacerbate local emissions. Avoiding peak hours near industrial areas is also advisable.