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Elvas, nestled in the Portalegre district of Portugal, occupies a strategically significant position on the border with Spain. The city is situated on a gently undulating plain, part of the larger Alentejo region, at an elevation of approximately 146 meters. This relatively low altitude, combined with its inland location, influences its air quality dynamics. The surrounding landscape is predominantly agricultural, characterized by extensive olive groves, cork oak forests, and cereal crops. While not heavily industrialized, the proximity to Spanish industrial areas and transport corridors presents a potential source of transboundary pollution. The Guadiana River flows nearby, but its distance from the city centre means it has limited direct impact on local air circulation patterns. Elvas’s urban character is defined by its remarkably well-preserved fortifications, a UNESCO World Heritage site, which create a complex urban morphology. The urban-rural gradient is relatively sharp, transitioning quickly to open countryside. This gradient affects dispersion of pollutants; rural areas act as sinks or sources depending on agricultural practices, while the city itself experiences localized concentrations due to traffic and domestic heating. The Alentejo’s generally dry climate and prevailing wind patterns further shape air quality, often leading to stagnant conditions during certain periods.

Elvas experiences a Mediterranean climate, with distinct seasonal variations impacting air quality. Summers (June-August) are typically hot and dry, with low wind speeds. This can lead to the build-up of ozone and particulate matter from agricultural activities and long-range transport. August, particularly, can see elevated levels due to heatwaves and increased solar radiation. Autumn (September-November) brings increased rainfall, which helps to cleanse the atmosphere, improving air quality. However, the onset of heating systems in October can introduce localised pollution from wood burning. Winters (December-February) are mild but can experience temperature inversions, trapping pollutants near the ground, especially during calm, clear nights. January and February are often the months with the poorest air quality. Spring (March-May) sees a gradual improvement as temperatures rise and rainfall increases, though pollen from local vegetation becomes a significant allergen. Sensitive individuals, such as those with respiratory conditions, should be particularly cautious during summer heatwaves and winter inversions. Avoiding strenuous outdoor activity during peak pollution periods and staying informed about local conditions is crucial for protecting health.