Urban characteristics and its influence on resuspension of road dust, air quality and exposure

The present study examines the impact of urban attributes such as heterogeneous traffic, land use activities and meteorological factors on road dust resuspension and ambient particulate matter (PM) concentrations at urban roads. Silt load (SL) and PM emission rates from urban roads were quantified for 18 locations in Chennai and compared with 10 locations in Delhi city. Further, a detailed analysis was carried out for Chennai city alone to understand the size distribution of road dust, seasonal variation of SL, ambient PM concentrations and meteorological factors. Results indicated that the highest silt load values were observed on roads close to construction sites (Chennai = 34 g/m2 day and Delhi = 40 g/m2 day). Further, seasonal variation observations depicted that water stagnation on roads and poor drainage conditions during monsoon led to high silt load concentrations and subsequent PM emissions during post-monsoon season. Due to fugitive emissions and heavy-duty commercial vehicular (HCV) movement at construction sites, the 24-h average PM concentrations and total mass exposures (MET) were found to be highest compared to other locations (PM10 = 183.3 ± 25 μg/m3, PM2.5 = 80.7 ± 6.7 μg/m3 and MET = 2.66 μg/min). The PM2.5 and PM10 emission rates were also found to be higher at construction sites (PM2.5 = 6.65 and PM10 = 27.525 g/VKT) followed by the dumpsite (PM2.5 = 6.52 and PM10 = 26.96 g/VKT). The higher proportion of HCVs at dumpsite has led to higher PM emission rates. Further, the size distribution analysis of silt load showed that on average, 13–18% of dust deposited on roads is finer than 10 microns, 6–9% dust is finer than 2.5 microns and 4–6% of particulates is finer than 1 micron. The observations of the present study imply that traffic, land use and seasonality have a significant impact on road dust deposition and resuspension.