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Arroio do Tigre, nestled in the heart of Rio Grande do Sul, Brazil, occupies a geographically significant position within the broader Gaucho landscape. Located approximately 60 kilometers northwest of Porto Alegre, the state capital, it sits within a transitional zone between the pampas biome and the foothills of the Serra Geral mountain range. This location dictates a gently undulating terrain, characterized by fertile plains historically dedicated to cattle ranching and agriculture, particularly soybean and rice cultivation. The city’s coordinates (-29.3328, -53.0928) place it within a region experiencing a subtropical climate, influencing both its vegetation and atmospheric conditions. The Guaíba River, a vital waterway, flows nearby, impacting local humidity and potentially influencing pollutant dispersion patterns. While Arroio do Tigre itself is a relatively small municipality, its proximity to Porto Alegre and the broader industrial belt along the Gravataí River introduces a degree of regional air pollution influence. The urban–rural gradient is relatively sharp; the city transitions quickly into agricultural land, meaning agricultural practices and occasional controlled burns can contribute to localized air quality events. Elevation is relatively low, averaging around 40 meters above sea level, which can exacerbate temperature inversions, trapping pollutants closer to the ground. The surrounding landscape, dominated by grasslands and scattered forests, plays a role in absorbing some pollutants, but also contributes to particulate matter through natural sources like dust storms during drier periods. The regional geography, therefore, presents a complex interplay of natural and anthropogenic factors affecting air quality.

Arroio do Tigre’s subtropical climate dictates a distinct seasonal pattern in air quality. The summer months (December to February) are typically characterized by high temperatures and humidity, often leading to stagnant air conditions and increased ozone formation, particularly during periods of intense sunshine. This can be exacerbated by agricultural activities, including the use of pesticides and fertilizers. Conversely, the autumn months (March to May) often bring more frequent rainfall, which helps to cleanse the atmosphere and reduce particulate matter. However, the transition period can also see the occurrence of fog, especially in the mornings, trapping pollutants and reducing visibility. Winter (June to August) is generally the most challenging period for air quality. Cold, stable air masses frequently lead to temperature inversions, where a layer of warm air sits above cooler air near the ground, preventing vertical mixing and trapping pollutants. This effect is amplified by the relatively low elevation of the region. Spring (September to November) sees a gradual improvement in air quality as temperatures rise and wind patterns become more dynamic, dispersing pollutants. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter months and hot, still summer days. Avoiding strenuous outdoor activity during peak pollution episodes is advisable. Agricultural workers should be particularly mindful of pesticide drift and respiratory protection during spraying operations. Monitoring local weather forecasts for temperature inversions and stagnant air conditions is crucial for informed decision-making regarding outdoor exposure.