Estimation of greenhouse gas emission factors based on observed covariance of CO2, CH4, N2O and CO mole fractions

Background Covariances among major anthropogenic greenhouse gases were studied during three cold-air pool episodes in the Pannonian Basin to better constrain their emission factors for Europe. Results On the base of observed covariance between carbon dioxide, methane, carbon monoxide and nitrous oxide atmospheric dry air mole fraction in a region of the Pannonian (Carpathian) Basin during three cold-air pool episodes in January-February 2017, emission factors relative to carbon dioxide were determined. For the determination of the emission of carbon dioxide, a simple boundary-layer budget model was compiled. The model gave 6.3 g m(-2) day(-1) carbon dioxide emission for the footprint area of the measurements on average for the period of the episodes. The 6.7-13.8 nmol mu mol(-1), 0.15-0.31 nmol mu mol(-1) and 15.0-25.8 nmol mu mol(-1) ratios for CH4:CO2, N2O:CO2 and CO:CO2, respectively, correspond to 15.3-31.7 mg m(-2) day(-1) methane, 0.9-2.0 mg m(-2) day(-1) nitrous oxide and 60.0-103.4 mg m(-2) day(-1) carbon monoxide emissions for the region. These values are somewhat higher than the officially reported bottom-up annual national averages for Hungary, which are explained by the winter conditions and intensive domestic heating. Conclusions The study indicated the high share of biomass burning in residential heating in rural environment that results in high carbon monoxide emission relative to that of carbon dioxide. It also indicated that the actual emission factor for nitrous oxide may exceed the range given in the guidelines for inventory compilation, which should be taken into account in reporting. It is shown that even a simple boundary-layer budget model might give realistic emission estimation under cool-air pool episodes.