Exposure to ultrafine particles, black carbon and particulate matters in Yangtze River Delta: A case from suburb Nanjing

This study assessed the exposure of commuters to ultrafine particulate matter (UFP), black carbon (BC), and particulate matter (PM) concentrations in a diverse traffic microenvironment over a 3-km, high-traffic section in suburban Nanjing, China. We evaluated the mean exposure concentration difference between distinct special cases (peak and off-peak hours, weekdays and weekends, severe dust days and holidays) in five traffic microenvironments of subway, bus, taxi, e-bike (electric motorbike) and bicycle. The bicycle commuters were exposed to the highest PM (PM1, PM2.5, PM10) concentration, the bus commuters to the highest BC concentration in the morning peak hours (3.4±3.0 μg/m3), and the bus and taxi commuters to the highest UFP number concentration. The subway (metro) commuter had the lowest mean exposure concentration of PM, BC, and UFP number during the rides. Regarding the total inhaled dose of PM2.5, it was highest to the bicycle commuters (16.25 μg/km) followed by e-bike (1.98 μg/km), bus (1.28 μg/km), taxi (0.69 μg/km), and subway commuters (0.45 μg/km). The exposure levels of PM2.5 (114.6 μg/m3) and BC (1826 ng/m3) on weekdays were higher than those on weekends (170% and 158%, respectively). PM2.5, PM10 and BC concentrations on dust days were significantly higher than those on weekdays and holidays, with the mean exposure concentration of PM10 (1299.2±1285.8 μg/m3) in the evening peak of dust days was 803% and 994% higher than the mean concentrations on weekdays and holidays, respectively.