LB 19-169 - Greenhouse gas concentration and carbon isotope ratio of atmospheric CO2 and CH4 in an urban area were influenced by anthropogenic emissions and natural processes: A case study in plateau city

Atmospheric concentration of carbon dioxide (CO2), methane (CH4), and its carbon isotope characteristic (δ13C-CO2 and δ13C-CH4) in the urban area will better understand the role of anthropogenic emissions and natural ecosystem in carbon sources and sinks from the regional to the global carbon cycle. However, the effects of human activities change and climate on carbon emissions remain under-investigated and desideratum, on account of complex urban emissions and natural environmental heterogeneity. In this study, we conducted a seasonal vehicle monitoring to explore these qualities in an Asia plateau city, using a high-resolution wavelength-scanned cavity ringdown spectrometer (WS-CRDS). Potential sources regions and transport pathways of greenhouse gas (GHG) were studied in association with meteorological conditions. The results indicated that the average CO2 and CH4 concentrations for the area were 460.84 and 2.00 parts per million by volume (ppm) with significant spatial heterogeneity in summer, respectively, which were higher than those at global and regional background observatories. The grid map of carbon emissions obtained from the experiment and the international carbon emission database (Emissions Database for Global Atmospheric Research, EDGAR V6.0) both showed a trend of decreasing urban carbon emission intensity from urbanized areas to suburbs, but there was a carbon sink effect in areas where urban forests and university campuses gather. Isotope surveying of the GHG revealed that the CO2 and CH4 emission was highly correlated to human activity (e.g., gasoline combustion, landfill, steel forging, and natural gas burning). Cluster analysis of back trajectories model (TrajStat) was used to study the transport of atmospheric gases, the results explored the possibility that carbon emissions from the Yuxi and Mengzi industrial areas in the south may also be transported by air masses to increase the carbon concentration in Kunming. The findings of this study might help to build a better understanding of the mechanism of GHG emission and evaluate the potential influencing factors, confirming the importance of urban carbon neutrality in the context of global change.