A New Methodology for Indoor PM2.5 Source Apportionment
Shiva Nourani, HECTOR JORQUERA, Pontificia Universidad Catolica de Chile
Abstract Number: 360
Working Group: Indoor Aerosols
Abstract
Quantifying source contributions to indoor PM2.5 has been limited by monitoring costs (Othman et al, 2022). Here we propose a new, cost-effective methodology. We apply FUSTA — FUzzy SpatioTemporal Apportionment (Jorquera and Villalobos, 2023)— to a database of indoor and outdoor PM2.5 concentrations in classrooms of 19 schools, measured using low-cost sensors, to find the main spatiotemporal patterns (STP) in PM2.5. We find four dominant STP in outdoor PM2.5: regional, overnight mix, traffic, and secondary PM2.5; indoor PM2.5 has these same STP as counterparts plus another STP characteristic of indoor generated PM2.5. These indoor STP show concentration peaks during activity hours due to housekeeping and children’s activities.
On average, the overnight mix source contributes to indoor PM2.5 with 11.5 μg/m3, followed by secondary (9.9 μg/m3), traffic (6.3 μg/m3) and regional (4.8 μg/m3) sources, respectively; indoor-generated contributions are 5.8 μg/m3. A cluster wise indoor-outdoor PM2.5 regression is applied to estimate STP-specific infiltration factors (Finf) per school. Median and IQR for Finf are 0.7 [0.62-0.9], 0.83 [0.7-0.89], 0.72 [0.64-0.81] and 0.76 [0.68-0.84] for regional, overnight mix, traffic, and secondary sources, respectively.
This cost-effective methodology can identify the indoor-generated contributions to indoor PM2.5 —including their temporal variability — and estimate a source apportionment of the major sources contributing to indoor PM2.5 concentrations. In the context of classroom environments, it allows to estimate children’s exposure per source during school hours.
References:
[1] M. Othman et al., Children's exposure to PM2.5 and its chemical constituents in indoor and outdoor schools urban environment, Atmospheric Environment, Volume 273,2022,118963, https://doi.org/10.1016/j.atmosenv.2022.118963.
[2] Jorquera H., Villalobos A.M. (2023) A new methodology for source apportionment of gaseous industrial emissions. Journal of Hazardous Materials, 443 B, 130335 https://doi.org/10.1016/j.jhazmat.2022.130335.