Quantification and modelling of on-road CO2 emissions and its impacts on ambient CO2 concentrations in an Indian coastal city

Abstract:

This paper presents the results of CO₂ emission inventory, monitoring of CO₂ concentrations and modelling of on road CO₂ emissions in an Indian coastal city. Bottom up approach was adopted for quantifying the grid wise on road CO₂ emissions of Chennai city at a finer resolution of 1Km x 1Km using the real time traffic data of 56 major roads. In addition, monitoring of ground level CO₂ concentrations and vehicular traffic were carried out at a residential site in Chennai to understand the impact of vehicular emissions on the ambient CO₂ levels. Further, AERMOD, a US EPA regulatory model, was deployed to find the spatial variation of CO₂ concentrations due to the emissions from 38 major corridors of Chennai.

Results indicated that a total emission of 0.65 Tg/year of CO₂ was emitted by the vehicular traffic from the major roads of Chennai. Cars were identified as the larger emitters of CO₂ with a contribution of 25% of the total emissions followed by three wheelers (21%), trucks (16%), buses (15%), two wheelers (13%) and Light Commercial Vehicles (9%). Ground level CO₂ concentrations at the study area were in the range 391.52 to 666.37 ppm, with a mean hourly concentration of 448 ± 33.45 ppm. It was observed that the CO₂ concentrations were high during the morning and evening peak hours and low during the afternoons and further vehicular emissions were found to have a significant effect on the ambient CO₂ concentrations during the morning peak hours (R²=0.78) and afternoons (R²=0.50). But, contrastingly, a weak correlation was observed between the vehicular emissions and CO₂ concentrations during the evening peak hours (R²=0.02). In addition, night time CO₂ concentrations were observed higher in the weekends corresponding to high vehicular traffic during the late evenings. From the modelling results, it was found that the considered 38 major corridors contribute 0.12 ppm of CO₂ per year to the ambient atmosphere.