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Demerval Lobão, nestled in the state of Piauí, Brazil, occupies a relatively flat portion of the semi-arid sertão region. Located at approximately -5.3578 latitude and -42.6758 longitude, the city’s geography is characterized by low elevation, contributing to limited natural air dispersion. The surrounding landscape is dominated by caatinga, a unique scrubland ecosystem adapted to prolonged droughts. The Parnaíba River lies to the north, but its influence on local air quality is indirect, primarily through humidity levels rather than direct pollutant removal. Demerval Lobão’s urban character is typical of smaller Brazilian cities, with a growing concentration of residential areas around a central commercial district. Agriculture, particularly subsistence farming and livestock raising, is prevalent in the surrounding rural areas, potentially contributing to particulate matter from land clearing and animal husbandry. The urban-rural gradient is relatively sharp, with a noticeable increase in dust and localized emissions as one approaches the city center. The lack of significant industrial belts within the immediate vicinity means that the primary air quality concerns are likely linked to vehicle emissions, biomass burning (seasonal), and dust resuspension, exacerbated by the region’s dry climate and limited rainfall for natural dust suppression. The flat terrain hinders the natural flushing of pollutants, increasing their concentration during periods of low wind speed.

Demerval Lobão experiences a distinct wet and dry season, heavily influencing air quality. The dry season, typically from June to November, is the period of greatest concern. Reduced rainfall leads to increased dust resuspension from the caatinga vegetation and agricultural lands, significantly elevating particulate matter levels. Lower humidity also means pollutants have less chance of being rained out of the atmosphere. Temperature inversions, common during the cooler nights of the dry season, trap pollutants near ground level, worsening air quality. August and September are often the most challenging months. Conversely, the wet season (December to May) brings relief. Rainfall effectively washes pollutants from the air, and higher humidity suppresses dust. However, even during the wet season, localized pollution from vehicle traffic and biomass burning for land preparation can occur. February and March, during peak rainfall, generally offer the best air quality. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit outdoor exertion during the dry season, particularly in the late afternoon and early morning when pollutant concentrations are highest. Monitoring local fire reports is crucial during the transition periods between wet and dry seasons, as agricultural burning can rapidly degrade air quality.