Characterization of Greenhouse Gas Emissions from the Territory of the St. Petersburg Agglomeration, Russia, Based on the Results of EMME-2019 and EMME-2020 Mobile Observational Campaigns

Saint Petersburg is the second most populous city in the Russian Federation and the fourth in Europe. According to official statistics, ∼5.6 million people permanently live in the city. In order to experimentally estimate greenhouse gas emissions from the territory of the St. Petersburg agglomeration, an original combined approach was developed and implemented during EMME-2019 and ЕММЕ-2020 observational campaigns. The paper summarizes the results of mobile experiments in 2019 and 2020. The period March – early May chosen for the EMME campaigns is shown to be optimal for estimating CO₂ emissions. The average anthropogenic additives caused by emissions from the territory of St. Petersburg were assessed at ∼1.07 ppmv for CO₂ and ∼6.61 ppbv for CH₄. Experimental estimates of specific greenhouse gas fluxes for the territory of the St. Petersburg agglomeration amounted to 72 kt km⁻² year⁻¹ CO₂ and 198 t km⁻² year⁻¹ CH₄ for six days of the campaign in 2020; 80 kt km⁻² year⁻¹ CO₂ and 161 t km⁻² year⁻¹ CH₄ for 15 days of the campaigns in 2019 and 2020. The CH₄/CO₂ and CO/CO₂ emission ratios for St. Petersburg in March–early May 2020 averaged 6.4 and 5.7 ppbv/ppmv, respectively. Lockdown restrictions due to COVID-19 pandemic affected the structure of emission from the territory of St. Petersburg, namely, a sharp decrease in transport activity significantly decreased CO emissions from motor vehicles.