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San Lorenzo, nestled in the province of Santa Fe, Argentina, occupies a strategically important position within the Paraná River basin. Located at approximately -32.75° latitude and -60.73° longitude, the city’s geography is fundamentally shaped by its proximity to the Paraná River, a major waterway and transportation artery. The surrounding landscape is characterized by the fertile pampas, a vast expanse of low-lying grasslands historically dedicated to agriculture, primarily soybean and wheat cultivation. This agricultural intensity contributes to regional dust and potential pesticide drift, impacting air quality. San Lorenzo itself sits on relatively flat terrain, with an elevation of around 23 meters above sea level, which can exacerbate the trapping of pollutants, particularly during periods of calm weather. The urban fabric is a mix of residential areas, commercial zones, and industrial activity, with a noticeable urban–rural gradient extending outwards towards the agricultural fields. While not directly adjacent to a major industrial belt, San Lorenzo serves as a logistical hub for the region, facilitating the transport of agricultural products and raw materials, leading to truck traffic and associated emissions. The city’s location within the humid subtropical climate zone means it experiences distinct wet and dry seasons, influencing local wind patterns and the dispersion of pollutants. The Paraná River itself, while providing a vital resource, can also contribute to localized humidity and fog formation, further impacting air quality dynamics.

San Lorenzo’s air quality experiences a distinct seasonal cycle dictated by its subtropical climate. The warmer months, typically December to February, are often characterized by stagnant air and increased temperatures, frequently leading to temperature inversions. These inversions trap pollutants near the ground, resulting in periods of poorer air quality. Agricultural activities intensify during this period, with increased machinery use and potential for fertilizer application, contributing to particulate matter and ammonia emissions. Conversely, the cooler months (June to August) generally see improved air quality due to increased wind speeds and more frequent rainfall, which naturally cleanses the atmosphere. However, cold, clear nights can also lead to ground-level ozone formation as sunlight interacts with precursor pollutants. The transitional seasons – spring (September to November) and autumn (March to May) – present a mixed picture. Spring can be prone to dust storms originating from the surrounding agricultural lands as soil dries out. Autumn often brings calmer conditions and increased humidity, potentially leading to localized fog and reduced visibility. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the warmer months, particularly on days with stagnant air. Limiting outdoor exertion and monitoring local air quality reports are advisable. During periods of agricultural activity, minimizing exposure to fields and wearing appropriate respiratory protection may be beneficial. The Paraná River’s influence can also contribute to localized humidity, which, while generally beneficial, can sometimes exacerbate respiratory issues for those with sensitivities.