Indoor-outdoor relationship of submicron particulate matter in mechanically ventilated building: Chemical composition, sources and infiltration factor

To evaluate the impact of outdoor particulate pollution on indoor air quality, the chemical composition and sources of submicron aerosol particles (PM1) were studied indoors and outdoors. Measurements were carried out during the heating season from October 15, 2020, to February 8, 2021, at the Center for Physical Sciences and Technologies in Vilnius, Lithuania. Online measurements of PM1 chemical composition were performed using an Aerosol Chemical Speciation Monitor (ACSM (organics, sulfate, and nitrate)) and an Aethalometer (equivalent black carbon, BC). In parallel with the online measurements, filter-based elemental composition and C-14 analysis of PM1 were performed using a Particle-Induced broad-beam X-ray Emission (PIXE) and a Single Stage Accelerated Mass Spectrometer (SSAMS), respectively. The source apportionment results showed a dominant contribution of biomass burning to the total carbonaceous aerosol particles, including primary (30%) and secondary (40%) fractions. According to the enrichment factors, the main source of trace elements was road dust resus-pension (30%), while anthropogenic emissions accounted for only 13% of trace elements. The infiltration factor (F-inf) of all studied PM1 constituents was low (F-inf similar to 0.03). This result indicates that the three-stage building filter system (G4-F7-F9) provides high protection against particle pollution of different origins and significantly re-duces indoor exposure to PM1. The changed chemical composition of indoor PM1 can be attributed to species -specific evaporation and some minor indoor sources.

Automated summary

This study evaluated the impact of outdoor particulate pollution on indoor air quality by investigating the chemical composition and sources of submicron aerosol particles (PM1) indoors and outdoors. The results showed differences in the chemical composition and sources of PM1 between indoor and outdoor environments, with biomass burning and road dust resuspension being the primary sources. The three-stage building filter system was found to provide effective protection against indoor particle pollution.