Source apportionment of ambient PM_2.5 in an industrialized city using dispersion-normalized, multi-time resolution...

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Public Health

Background:

• Hamilton, Ontario's lower city experiences complex air pollution due to topography.
• Fine particulate matter (PM2.5) poses significant health risks.
• Understanding PM2.5 sources is crucial for air quality management.

Purpose of the Study:

• To identify and quantify sources of ambient fine particulate matter (PM2.5) in Hamilton, Ontario.
• To investigate the influence of local meteorology and topography on PM2.5 apportionment.
• To assess the health implications of identified PM2.5 sources, particularly during air quality guideline exceedances.

Main Methods:

• Collected ambient fine particulate matter (PM2.5) data over an 18-month period.
• Employed dispersion-normalized, multi-time resolution factor analysis (DN-MT-FA) to reduce meteorological influence.
• Apportioned PM2.5 contributions to factors including secondary organic aerosols (SOA_1, SOA_2), particulate nitrate (pNO3), particulate sulfate (pSO4), primary traffic organic matter (PTOM), and steel/metal processing and mobile emissions (Steel & Mobile).

Main Results:

• Local sources (PTOM, Steel & Mobile, SOA_2) contributed up to 17% of average PM2.5 mass.
• Mixed local/regional factors (pNO3, pSO4) accounted for 43% of average PM2.5 mass.
• Secondary organic aerosols type 1 (SOA_1) drove summer exceedances (wildfires), while particulate nitrate (pNO3) dominated winter exceedances (local traffic).
• Local industrial factors, though minor in mass, are rich in toxic species, posing health risks.

Conclusions:

• Local and regional sources significantly contribute to PM2.5 in Hamilton.
• Targeting local sources offers potential for reducing harmful PM2.5 concentrations.
• Industrial emissions and traffic are key contributors to PM2.5, with significant health implications, especially during pollution events.