Microscopic characteristics and differences of fine primary particles emitted from coal⁃fired power plant and residential coal combustion

Coal⁃fired power plants and residential coal combustion are the main contributors to the air pollution in Chi⁃ na，and the understanding of the microscopic characteristics，such as morphology，composition，and mixing state，of pri⁃ mary individual particles is crucial to analyze the sources of aerosol particles. This study employed the instruments of transmission electron microscopy and energy⁃dispersive X-ray spectrometer to obtain the microscopic characteristics of individual particles emitted from coal⁃fired power plants and residential coal combustion. The results reveal that non⁃carbonaceous particles， such as mineral particles and S - rich particles， are dominated in the emissions from coal⁃fired power plants，accounting for 93.6% of the total analyzed particles. The mineral particles are main⁃ ly composed of Si， O， and metal elements， and the S⁃rich particles are mainly composed of S element.Residential coal combustion mainly emits carbonaceous particles，including black carbon and organic particles，which is obviously different from those from coal⁃fired power plants. It was found that the individual particles from flaming and smoldering phases of residential coal combustion are different. The flaming phase emits abundant black carbon， which accounts for 96. 9% of the total analyzed particles. Black carbon is mainly composed of C element and exhibits chain⁃like or cluster⁃like shape. However，the smoldering phase mainly emits organic particle，which is main⁃ ly composed of C element and exhibits round or nearly round shape. The size distribution analysis reveals that the fine particles emitted from coal⁃fired power plants exhibit a peak at around 700 nm，which is higher than 500 nm for residen⁃ tial coal combustion. This study reveals that different combustion conditions are the key reasons why there are the huge differences between individual particles emitted from coal⁃fired power plants and residential coal combustion.