A methodology for estimating indoor sources contributing to PM_2.5

Area of Science:

• Environmental Science
• Air Quality Research
• Indoor Environmental Quality

Background:

• Accurate quantification of indoor particulate matter (PM_2.5) sources is crucial for public health.
• Traditional chemical speciation analyses are costly and limit source apportionment studies.
• A cost-effective methodology is needed to estimate indoor PM_2.5 source contributions.

Purpose of the Study:

• To develop and apply a novel methodology for estimating indoor PM_2.5 source contributions.
• To identify and characterize spatiotemporal patterns (STPs) of indoor and outdoor PM_2.5.
• To differentiate between outdoor-influenced and indoor-generated PM_2.5 in school classrooms.

Main Methods:

• Application of FUzzy SpatioTemporal Apportionment (FUSTA) to indoor/outdoor PM_2.5 data and meteorological variables.
• Identification of dominant STPs for both outdoor and indoor PM_2.5.
• Cluster-wise indoor-outdoor PM_2.5 regression to estimate STP-specific infiltration factors (F_inf).

Main Results:

• Four dominant STPs were identified in outdoor PM_2.5 (regional, overnight mix, traffic, secondary).
• An additional STP characteristic of indoor-generated PM_2.5 was identified, with peaks during school activities.
• Indoor-generated PM_2.5 contributed an average of 5.7 μg m^-3 (17% of total), rising to 22% during school hours.

Conclusions:

• The FUSTA methodology provides a cost-effective means to estimate indoor PM_2.5 source contributions.
• The study successfully differentiated indoor-generated PM_2.5 from outdoor sources in classrooms.
• This approach enables the assessment of temporal variability in indoor air pollution sources.