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Baozhong, nestled in Yunlin County, southwestern Taiwan (23.6956° N, 120.3117° E), occupies a geographically significant position within the island’s coastal plain. The city’s terrain is predominantly flat, characteristic of the low-lying alluvial plains formed by the Erren River and its tributaries. This flatness, while beneficial for agriculture, contributes to air quality challenges as it limits natural dispersion of pollutants. Baozhong sits within a region heavily reliant on agriculture, particularly rice cultivation and aquaculture, which, while vital to the local economy, can introduce localized sources of ammonia and particulate matter. The surrounding landscape is a patchwork of rice paddies, fruit orchards (especially pomelos and mangoes), and small-scale farming operations, creating a distinct urban–rural gradient. The proximity to the Taiwan Strait influences local weather patterns, bringing in maritime air masses and occasional sea breezes. However, the prevailing westerly winds, common across Taiwan, can also transport pollutants from industrial areas further inland. Baozhong’s elevation is relatively low, averaging around 15 meters above sea level, further hindering vertical mixing and potentially trapping pollutants close to the ground. While not directly adjacent to major industrial belts, its location within Yunlin County means it’s susceptible to transboundary pollution from nearby manufacturing hubs and the greater Chiayi industrial zone. The lack of significant topographic barriers exacerbates this vulnerability, making Baozhong’s air quality intrinsically linked to regional industrial activity and agricultural practices.

Baozhong’s air quality experiences a distinct seasonal cycle driven by Taiwan’s subtropical climate and monsoon patterns. The warmer, drier months (April to September) often see a gradual increase in particulate matter concentrations. Reduced rainfall and increased solar radiation contribute to stagnant air conditions, particularly during periods of high pressure. Temperature inversions, where a layer of warm air traps cooler air near the ground, are more frequent during these months, severely limiting vertical mixing and concentrating pollutants. Agricultural burning, though regulated, can still occur in the late summer months, adding to the particulate load. Conversely, the wetter months (October to March) generally bring improved air quality due to frequent rainfall, which effectively ‘washes’ pollutants from the atmosphere. Stronger northeasterly monsoon winds also enhance dispersion, carrying pollutants away from the city. Fog, common during the winter months, can temporarily trap pollutants, leading to localized episodes of reduced visibility and elevated concentrations. The spring months (March-April) can be particularly challenging as agricultural activity ramps up, and the transition from the monsoon season to drier conditions creates unstable atmospheric conditions. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the warmer, drier months, limiting outdoor exertion during peak pollution periods. Maintaining awareness of regional air quality reports and avoiding strenuous activity on days with visibly hazy conditions is advisable.