Measurements of Indoor and Outdoor Fine Particulate Matter during the Heating Period in Jinan, in North China: Chemical Composition, Health Risk, and Source Apportionment

Fine particulate matter (PM2.5) was simultaneously collected from the indoor and outdoor environments in urban area of Jinan in North China from November to December 2018 to evaluate the characteristics and sources of indoor PM2.5 pollution. The concentrations of indoor and outdoor PM2.5 were 69.0 ± 50.5 µg m−3 and 128.7 ± 67.9 µg m−3, respectively, much higher than the WHO-established 24-h standards for PM2.5, indicating serious PM2.5 pollution of indoor and outdoor environments in urban Jinan. SO42−, NO3−, NH4+, and organic carbon (OC) were the predominant components, which accounted for more than 60% of the PM2.5 concentration. The total elemental risk values in urban Jinan for the three highly vulnerable groups of population (children (aged 2–6 years and 6–12 years) and older adults (≥70 years)) were nearly 1, indicating that exposure to all of the elements in PM2.5 had potential non-carcinogenic risks to human health. Further analyses of the indoor/outdoor concentration ratios, infiltration rates (FINF), and indoor-generated concentration (Cig) indicated that indoor PM2.5 and its major chemical components (SO42−, NO3−, NH4+, OC, and elemental carbon) were primarily determined by outdoor pollution. The lower indoor NO3−/SO42− ratio and FINF of NO3− relative to the outdoor values were due to the volatility of NO3−. Positive matrix factorization (PMF) was performed to estimate the sources of PM2.5 using the combined datasets of indoor and outdoor environments and revealed that secondary aerosols, dust, cement production, and coal combustion/metal smelting were the major sources during the sampling period.