Comparative measurement of CO₂, CH₄ and CO at two traffic interjunctions having inflated vehicular flow in Delhi

Vehicular emissions are considered one of the major anthropogenic sources of greenhouse gases and poor air quality in metropolitan cities. This study aims to see the correlation of CO₂, CH₄, and CO through monitoring over a period from December 2020 to October 2021 covering three seasons' winter, summer, and monsoon at two different traffic locations of Delhi having different traffic volumes, road patterns, and traffic management. The annual average morning concentration of CO₂, CH₄ and CO was found (533 ± 105), (7.3 ± 3.1), (10.7 ± 3.0) ppm at Najafgarh and (480 ± 70), (5.2 ± 1.8), (7.8 ± 2.8) ppm at Rajendra Place, respectively. A relationship between concentration of all three gases and meteorological parameters such as temperature, humidity, wind speed and wind direction has also been investigated using Pearson correlation coefficient and pollution rose diagram. A comparable pattern in concentration was observed for all three gases in spatial (location) and temporal (diurnal) distribution. The concentration trend of CO₂ in different seasons is winter > summer > monsoon, while in the case of CH₄ winter = summer > monsoon but not any seasonal trend was noted in CO case. It is observed that CO₂ has a good relation with CO (a tracer for vehicular emission) in terms of diurnal variation, whereas, CH₄ does not represent a relation with CO and CO₂ diurnally, suggesting that vehicles are the source of CO₂ but not much contributing to other greenhouse gases like CH_4.