Pollution characteristics of bioaerosols in PM2.5 during the winter heating season in a coastal city of northern China

Frequent heavy air pollution occurred during the winter heating season of northern China. In this study, PM₂.₅ (particles with an aerodynamic diameter less than 2.5 μm) was collected from a coastal city of China during the winter heating season from January 1 to March 31, 2018, and the soluble ions, organic carbon (OC), elemental carbon (EC), bacterial, endotoxin, and fungal concentration in PM₂.₅ were analyzed. During the winter heating season, PM₂.₅ and bioaerosols increased on polluted days, and the secondary inorganic ions, including NO₃⁻, NH₄⁺, and SO₄²⁻, increased significantly. Meteorological factors, such as wind direction and wind speed, had major impacts on the distributions of PM₂.₅ and bioaerosols. Pollutant concentration was high when there was a westerly wind with the speed of 3–6 m/s from inland area. Using the air mass backward trajectories and principal component analysis, we elucidate the potential origins of bioaerosol in PM₂.₅. The backward trajectory suggested that air mass for polluted samples (PM₂.₅ > 75 μg/m³) commonly originated from continent (9.62%), whereas air masses for clean samples (PM₂.₅ < 35 μg/m³) were mainly from marine (56.73%). The interregional transport of pollutants from continental area contributed most to PM₂.₅. Principal component analysis of the water-soluble ions and bioaerosol indicated that air pollution of the coastal city was greatly affected by coal combustion, biomass burning, and regional transmission of high-intensity pollutants from continent. Among that, interregional transport, biomass burning, and dust from soil and plants were main sources of bioaerosol. Our findings provide important insights into the origins and characteristics of bioaerosol in PM₂.₅ during the winter heating season of the coastal city in northern China.