Real-world vehicular emissions in the Indian megacity: Carbonaceous, metal and morphological characterization, and the emission factors

Abstract

This study develops real-world vehicular fleet emissions factors (EFs) through twin-site measurements for the first time in India. Real-time PM2.5, black carbon (BC), CO, and CO2, and gravimetric PM2.5 and PM10 were simultaneously measured at the kerbside and a background location in Mumbai. Particulate matter was further characterized for metals, carbonaceous constituents and morphology. The measured fleet average (±SD) EFs of PM2.5, PM2.5–10, and PM10 were 435 (±312), 774 (±259), and 1028 (±403), while for BC and CO it was 184 (±48) and 15,000 (±2000) mg (kg of fuel)−1, respectively. The EFOC and EFEC were 182 (±116) and 137 (±54) mg (kg of fuel)−1, while the EFmetals in PM2.5 and PM10, were 57 and 96 mg (kg of fuel)−1, respectively. The EFcoarse PM was ~1.8 times higher than EFPM2.5, suggesting the dominance of non-exhaust vehicular sources. The estimated uncertainties for the measured vehicular EF of CO, PM, and its chemical constituents ranged 44–128%. Traffic composition, temperature and humidity significantly affect the measured EFs which likely contributed to the uncertainty. These EFs would be useful for building a more accurate vehicular emission inventory and thus helping in urban air quality management, and also as inputs to climate models and policymaking.