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Morros, Maranhão, nestled within the Brazilian Cerrado biome, presents a unique geographic profile significantly influencing its air quality. Located at approximately -2.8639° latitude and -44.0389° longitude, the city sits on a gently undulating plateau, averaging around 150 meters above sea level. The surrounding landscape is dominated by the characteristic savanna vegetation of the Cerrado, a mosaic of grasslands, woodlands, and gallery forests along the Pindaré River, which flows nearby. This riverine influence moderates temperatures but also introduces potential sources of humidity and, occasionally, particulate matter from agricultural runoff. Morros’ position within Maranhão state places it within a transitional zone between the Amazon rainforest to the northwest and the drier Northeast region. This creates a complex interplay of climate patterns. While not directly adjacent to major industrial belts, the region supports agricultural activities, particularly soybean and maize cultivation, which can contribute to dust and ammonia emissions, especially during planting and harvesting seasons. The urban–rural gradient around Morros is relatively gradual, with small agricultural settlements and scattered rural communities extending outwards. The city’s compact urban footprint, with a population of 18,554, means that localized pollution sources, such as vehicle emissions and small-scale industries, can have a disproportionate impact on air quality within the city limits. Topography, with its gentle slopes, can sometimes trap pollutants, particularly during periods of low wind speed, exacerbating localized air quality issues.

Morros experiences a tropical climate characterized by distinct wet and dry seasons, profoundly impacting its air quality dynamics. The dry season, typically spanning from August to November, is often associated with elevated particulate matter concentrations. Reduced rainfall leads to drier soil conditions, increasing the potential for windblown dust from agricultural fields and unpaved roads. Furthermore, the lack of precipitation limits the natural cleansing effect of rainfall, allowing pollutants to persist longer in the atmosphere. Temperature inversions, common during the cooler, drier nights, can trap pollutants near the ground, further degrading air quality. Conversely, the wet season, from December to July, brings increased rainfall and higher humidity, generally leading to improved air quality as pollutants are washed from the atmosphere. However, intense rainfall events can occasionally mobilize soil particles, temporarily increasing particulate matter levels. The months of September and October often present the most challenging air quality conditions due to a combination of dry conditions, agricultural activity, and potential temperature inversions. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during these periods, limiting outdoor exertion and monitoring for any adverse health effects. During the wet season, while overall air quality is generally better, periods of heavy fog can reduce visibility and potentially trap pollutants, requiring similar precautions. Maintaining well-maintained roads and promoting sustainable agricultural practices are crucial for mitigating air quality challenges throughout the year.