Evolution in physicochemical properties of fine particles emitted from residential coal combustion based on chamber experiment

Abstract Fine particles (PM2.5) emitted from residential coal combustion play an important role in atmospheric geochemistry and have adverse effects on human health. Three types of residential coal, i.e., raw-bituminous coal (RBC), raw-anthracite coal (RAC) and honeycomb briquette (HB), were burned using a simulation burning system, and the freshly emitted particles were collected. The mass concentration of PM2.5 emitted from raw coal combustion was higher than HB, and the geochemical composition in PM2.5 varied according to coal types. The fraction of total carbonaceous components in PM2.5 emitted from RBC combustion was the highest (57.0–65.2%), followed by HB (9.6–22.2%) and RAC (11.0–17.6%). SO42− was the dominant water-soluble inorganic ion, accounting for 27.9–35.7% in the total detected water-soluble ions. In order to control sulfate emissions, priority should be given to HB, followed by RBC and RAC. Fe, As and Ba were the major trace elements in emitted PM2.5, accounting for 76.2–83.4% of the total detected trace elements. The freshly emitted individual fresh particles were treated with reactive gases (SO2 and NOX) under high relative humidity (85 ± 5%) in an environmental simulation chamber (ESC). The evolution in the physicochemical properties were tested by electron microscopes. Compared to fresh particles emitted from RBC, RAC and HB combustion, aged particles became more spherical with their average sizes increased by 70.6%, 133.3% and 91.7%, respectively. The relative mass fraction of S element in the particles increased by 13.1%. These results suggest that fresh particles emitted from coal combustion could be aged via aqueous-phase reactions with reactive gases under high humidity. The changes in the particles could negatively impact air quality, and consequently influence the regional climate.