Tailpipe on-road emissions of carbonaceous aerosols and gaseous pollutants from light-duty and heavy-duty vehicles for Indian on-road conditions

Emissions from road transport sector plays vital role in urban air pollution, climate change and human health risk. Diesel exhaust emissions are the primary source of carbonaceous aerosols including particulate matter (PM) and black carbon. Emissions of particulate and gaseous pollutants from vehicles depend on technology, fuel type, road type and driving behaviour. In present study, the real-world tailpipe emission factors of pollutants fromgoods and heavy-duty vehicles are presented for the first time from on-road operation of vehicles in India. A versatile source sampling system (VS3) has been designed, evaluated, and was used for emission measurement to collect the fine aerosol (PM2.5) mass on filters from tailpipe exhaust and near real-time characterization of its optical properties as aerosol absorption and scattering coefficients. The sampler comprises of an inlet system, portable dilution system, PM sampler, real-time particle characterizing instruments and power supply. The dilution tunnel was evaluated for particle loss at different dilution ratios and was found insignificant particle losses inside the tunnel at 40 to 60 dilution ratio. The on-road emission measurement of Tractors, LMV-goods and HDV-trucks were conducted in Nalanda districts, Bihar, India for determining emission factors of climate relevant pollutants PM2.5, elemental carbon (EC), organic carbon (OC), and water-soluble inorganic ions (WSIIs) and trace elements along with gaseous pollutants including CO, CO2 and NOx. The PM2.5 mass collected on Teflon filters were utilised for gravimetric and trace elements analysis, while tissue quartz filters were used for EC-OC analysis, and nylosorb filters for WSIIs. PM2.5 emission factors obtained in present study were in the range of 2.0 – 2.5 gkg-1, 0.8 – 1.5 gkg-1 and 0.8 – 2.6 gkg-1 for Tractors, LMV-goods and HDV-trucks respectively which were found to be significantly different from previous laboratory based chassis dynamometer studies. These new on-road emission factors would be helpful in emission inventories improvement which has implications in climate change assessment. The emission factors (gkg-1) of other climate relevant pollutants and total nationalemissions of pollutants from road transport sector will be discussed in this paper.