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Macomb, Illinois, situated in the western part of the state at coordinates 40.4709° N, 90.6807° W, occupies a gently rolling landscape within the glaciated till plains of the Midwest. The city’s elevation is approximately 784 feet (239 meters) above sea level, contributing to good regional drainage but also influencing local weather patterns. Macomb is firmly positioned within a predominantly agricultural zone, surrounded by expansive corn and soybean fields, typical of the Corn Belt. This agricultural dominance significantly impacts air quality through seasonal particulate matter from tilling and harvesting, as well as ammonia emissions from fertilizer application. The city itself is a regional hub, serving as a commercial and educational center for McDonough County. While not directly on a major waterway, Macomb is influenced by the broader Mississippi River watershed. The urban-rural gradient is relatively sharp; transitioning quickly from the city’s core to open farmland. Limited heavy industry within Macomb itself means that long-range transport of pollutants from larger industrial centers to the east and north (like Chicago and the industrial areas of Indiana) plays a crucial role in its air quality profile. Prevailing winds generally move from the southwest, potentially carrying pollutants from agricultural operations and distant urban areas.

Macomb’s air quality follows a distinct seasonal pattern. Spring (March-May) often sees elevated particulate matter due to agricultural activities – plowing, planting, and the application of fertilizers. Winds can be highly variable, sometimes trapping pollutants near the surface. Summer (June-August) generally offers the best air quality, with prevailing winds dispersing pollutants and rainfall acting as a natural scrubber. However, ozone formation can be a concern during hot, stagnant periods. Autumn (September-November) brings harvest season, again increasing particulate matter from field work and leaf decomposition. Temperature inversions become more frequent, trapping pollutants close to the ground, particularly in October and November. Winter (December-February) typically experiences the lowest levels of ozone but can suffer from increased particulate matter from residential wood burning and road salt application. Cold, calm conditions exacerbate pollution build-up. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during spring and autumn, and be mindful of wood smoke exposure in winter. Monitoring local forecasts and adjusting activity levels accordingly is crucial for protecting respiratory health throughout the year.