Exploring PM2.5 pollution in a representative Northern Chinese county: Insights for air quality management

Abstract

Counties have served as fundamental administrative units in China since the Qin Dynasty (221–206 BC), a tradition that continues today with hundreds of millions of residents living in county-level cities. Unlike higher-level cities such as municipalities and prefecture-level cities, counties differ significantly in size, development level, and development model, which can lead to distinct PM_2.5 pollution patterns. This study focuses on Yishui County, a representative county in northern China, to explore its PM_2.5 pollution characteristics and source contributions over a one-year period. Furthermore, the study compares Yishui's pollution profile with those of higher-level cities to provide insights into the relationship between development models and air quality. The annual average PM_2.5 concentration in Yishui was 67.8 μg/m³. Source apportionment using Discretized Normalized Positive Matrix Factorization (DN-PMF) identified six primary sources: dust (28.3%), secondary inorganic aerosols and residential coal combustion (SIA/RCC, 25.7%), vehicle emissions (24.6%), coal combustion (10.3%), industrial processes (9.1%), and biomass burning (2.0%). Dust was the dominant contributor, a notable divergence from patterns in higher-level cities. This disparity is likely attributed to Yishui's heavy reliance on real estate development as a primary economic driver, which significantly increases construction dust emissions. These results emphasize the impact of urbanization and economic structure on PM_2.5 pollution, indicating that other counties in northern China undergoing similar development stages may face comparable air quality challenges.