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Jieshang, nestled within Guizhou Province in southwestern China, occupies a geographically complex and strategically important position. Located at approximately 25.6989° N, 107.6481° E, the city sits within a karst landscape, characterized by dramatic limestone formations, sinkholes, and underground river systems. This terrain significantly influences local air circulation patterns; the undulating topography can trap pollutants, particularly during periods of low wind. Jieshang’s elevation, averaging around 800 meters above sea level, contributes to cooler temperatures and, at times, the formation of temperature inversions, a meteorological phenomenon that exacerbates air pollution by preventing vertical mixing. The surrounding landscape is a mosaic of steep hills, dense subtropical forests, and terraced agricultural fields, reflecting Guizhou’s predominantly rural character. While Jieshang itself is a relatively small urban center with a population of approximately 35,238, it serves as a regional hub for agricultural processing and light industry. The urban–rural gradient is sharp, with agricultural zones dominating the immediate periphery. The city’s proximity to the Wujiang River, though not directly adjacent, influences local humidity and can impact the dispersion of pollutants. Further afield, Guizhou’s broader industrial belt, concentrated in larger cities to the north and east, can contribute to transboundary air pollution events, impacting Jieshang’s air quality, particularly during unfavorable meteorological conditions. The karst geology also affects rainwater runoff and potential for dust resuspension, further complicating air quality management.

Jieshang’s air quality exhibits a distinct seasonal pattern dictated by the region’s subtropical monsoon climate. The wet season, typically spanning from April to September, brings frequent rainfall and higher humidity, generally leading to improved air quality as precipitation washes away particulate matter and dilutes gaseous pollutants. However, periods of prolonged rainfall can also increase mold and fungal spore concentrations, impacting respiratory health. The dry season, from October to March, presents a more challenging scenario. Reduced rainfall, coupled with cooler temperatures and increased frequency of temperature inversions, often results in stagnant air and pollutant accumulation. November and December frequently experience the poorest air quality, with fog and mist further trapping pollutants near the ground. Wind patterns during this period are often light and variable, hindering dispersion. Spring (March-April) sees a gradual improvement as temperatures rise and rainfall increases, but dust storms originating from the north can occasionally impact air quality. Summer (June-August) is generally the cleanest period, although intense convective thunderstorms can briefly elevate ozone levels. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should exercise caution during the dry season, particularly during periods of fog or mist. Limiting outdoor exertion and wearing appropriate respiratory protection are advisable. Agricultural burning, a common practice in surrounding rural areas during the transition periods (autumn and spring), can also contribute to localized air pollution spikes.