Co-benefit potential of urban CO₂ and air quality monitoring: A study on the first mobile campaign and building monitoring experiments in Seoul during the winter

For the first time, mobile campaign and building monitoring experiments were conducted in downtown Seoul, Korea during the 2018/2019 winter period to assess the possibility of the co-benefit of CO₂ emission reduction and air quality improvement. Given that CO₂ and air pollutants in cities both originate from fossil fuel combustion, monitoring urban CO₂ concentrations using a mobile vehicle and from the top of tall buildings can be a potentially effective approach for diagnosing the air quality. The local enhancement values (△species) related to urban emission sources were estimated by eliminating baseline concentrations. The results obtained showed high correlation coefficients between △CO₂ and △air pollutants (i.e., 0.753, 0.505, and 0.525 for △CO, △NO_X, and △NO₂), confirming the applicability of CO₂ as an indicator of air pollutant sources in downtown Seoul. The evaluation of the air quality in the study area using air pollutant ratios, including the ratios of CO and NO_X/NO₂, relative to CO₂ showed that the ratios of △CO, △NO_X, and △NO₂ relative to △CO₂ were 5.76, 1.89, and 0.21 ppb ppm⁻¹. The estimated △NO₂/△NO_X ratio (11%) and a comparison of the △NO_X/△CO₂ ratios obtained with those reported for other cities in different countries suggested the possibility of a relationship between the current air quality in downtown Seoul and the use of diesel vehicles. Results suggest that the development of municipal policies aimed at mitigating climate change should consider the co-benefit of air quality improvement so as to ensure the effective reduction of CO₂ and air pollutant emissions.