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Zhangshu, situated in central Jiangxi province at coordinates 28.0546°N, 115.5462°E, occupies a strategic position in China's Gan River basin, approximately 60 kilometers south of Nanchang, the provincial capital. The city's urban character blends traditional pharmaceutical manufacturing—earning it the nickname 'Medicine Capital of China'—with modern urban development, creating a distinctive industrial-residential landscape. Zhangshu lies within the Poyang Lake Plain, characterized by relatively flat terrain with an average elevation of 30-50 meters above sea level, which significantly influences its air quality dynamics. The Gan River flows through the city, providing some natural ventilation, while the proximity to Poyang Lake, China's largest freshwater lake about 100 kilometers northeast, creates microclimatic effects that can trap pollutants under certain conditions. Zhangshu is embedded within Jiangxi's agricultural heartland, surrounded by rice paddies and tea plantations, creating an urban-rural gradient where agricultural burning occasionally contributes to particulate matter. The city's location in the Yangtze River Delta's extended industrial belt means it experiences regional pollution transport from major industrial zones, particularly during northerly winds. Its position in a basin-like topography, flanked by low hills to the west and south, can lead to temperature inversions that trap pollutants, especially during winter months. The combination of local pharmaceutical manufacturing, regional industrial influence, and agricultural activities creates a complex air quality profile unique to this Jiangxi city.

Zhangshu's air quality follows a distinct seasonal pattern shaped by East Asian monsoons and local meteorological conditions. During spring (March-May), increasing temperatures and frequent frontal systems bring moderate pollution levels, though occasional dust storms from northern China can elevate particulate matter in April. The summer monsoon (June-August) provides the cleanest air, as southerly winds from the South China Sea disperse pollutants, and abundant rainfall washes particulate matter from the atmosphere—July and August are ideal for outdoor activities. Autumn (September-November) sees a gradual deterioration as monsoon winds retreat, with October often experiencing the year's first significant pollution episodes due to stable atmospheric conditions and increased agricultural burning after harvests. Winter (December-February) brings the worst air quality, with January typically being the peak pollution month due to temperature inversions that trap pollutants in the shallow boundary layer, combined with increased heating emissions and calm winds. Sensitive groups—particularly those with respiratory conditions, children, and the elderly—should limit prolonged outdoor exposure during winter mornings when inversions are strongest and during autumn haze episodes. The city's location in the Gan River valley exacerbates winter pollution through cold-air pooling, while summer offers relief through convective mixing. Fog, common in winter mornings, often combines with pollutants to create dense haze that reduces visibility and increases health risks.