THE METHODOLOGY FOR BURNING EFFICIENCY ESTIMATION IN
UKRAINE USING NO₂/CO RATIO

Atmospheric chemistry transport modeling and air quality decision-making rely on the input emissions data. Due to the existing uncertainties in emission inventories that come from the biases in assessment methodologies, huge efforts are made towards combining various approaches based on different data sources. Information about ratios of chemical compounds provides us with valuable knowledge about changes in fuel consumption by anthropogenic emission sources and natural air pollution releases. NO₂/CO ratio is among the most popular parameters for estimating burning efficiency that can be applied for remote sensing data. In this study we present the methodology for burning efficiency estimation relevant for Ukrainian territory.

We used seven pre-war case studies including three days for Kyiv (representing the variety of emission sources), two days for Mariupol (representing prevailing coal-fired industries), and two days for wildfires as reference cases for comparison. The methodology was developed using NO₂ and CO total columns (remote sensing by TROPOMI – Sentinel-5P), supported by the boundary layer height and wind parameters from the ERA-5 reanalysis.

The methodology consists of four main steps: (1) NO₂ and CO filtering using cloudiness and a quality assurance index; (2) meteorological data processing for obtaining the prevailing wind field at the top of the boundary layer; (3) NO₂ and CO content processing over emission sources and in the background; and (4) computation of NO₂/CO ratio.

The methodology testing reveals applicability for NO₂/CO ratio usage over Ukraine as for assessing the changes in fuel consumption, so also for further correction of emission factors. For selected case studies, NO₂/CO ratio equals 2.6 to 6.5 for wildfires, 3.1 to 4.6 for Mariupol, and 10.8 to 31.7 for Kyiv.

Keywords: nitrogen dioxide, carbon monoxide, TROPOMI, wildfire emissions, urban emissions