Tropospheric NO2 changes in Ukraine (2019&#8211;2022) amidst the Russian-Ukrainian conflict and consequent transboundary effects
Authors: Malytska Liudmyla , Galytska Evgenia , Ladstätter-Weißenmayer Annette , Burrows John P. , Moskalenko Stanislav 
Published: March 2024

Apart from the loss of life and property, the hostilities, which started on February 24, 2022, with the invasion by Russian armed forces into Ukraine, are altering Ukraine&#8217;s environment. In this study, we will present the major findings of Malytska et al., 2024, discussing the changes in tropospheric pollution, specifically nitrogen dioxide (NO2), as a consequence of military activities. This study uses the TROPOspheric Monitoring Instrument (TROPOMI) and Visible Infrared Imaging Radiometer Suite (VIIRS) satellite observations, Global Fire Assimilation System (GFAS) wildfire emission inventory, European Centre for Medium-Range Weather Forecasts (ECMWF) daily ERA5 reanalysis data, and the Hybrid Single-Particle Lagrangeian Integrated Trajectory analysis model (HYSPLIT) 5.2 to quantify the spatiotemporal distribution of tropospheric NO2, its changes and transport during the first three months of the armed conflict in Ukraine. This provides insights into the impact of hostilities on local air quality, as well as regional and transborder pollution.We discuss NO2 variability with a particular emphasis on comparing periods before and during hostilities to differentiate the effects of COVID-19 restrictions and the hostilities on NO2 emissions over Ukraine. The retrieved emissions show a temporal reduction in NO2 emission in industrial areas, comparable to the COVID-19 pandemic lockdown, whereas the NO2 tropospheric vertical column locally increased in the areas of conflict. Based on the TROPOMI and VIIRS data, we linked the major fires caused by the conflict to air pollution and found that hostilities led to more frequent and intense fires in conflict zones deteriorating air quality in the region. To investigate the impact of the hostilities on atmospheric pollution, we analysed nitrogen oxide (NOx) emission and injection altitude of fire, using the GFAS data. It was found that fires in conflict-affected areas exhibit greater intensity, characterized by larger plume top heights and higher rates of emission, in comparison to fires located far from the front line or resulting from isolated strikes. To demonstrate that increased fire activities contribute to pollution at both local and regional levels, we provide a case study of the fire episode of March 19-23, 2022, in the Kyiv region, coinciding with the active stage of the conflict and the defense of the capital, Kyiv. The simulations of HYSPLIT version 5.2 forward trajectories model showed that a smoke-particle-included air mass, related to the fires in the Chornobyl Exclusion Zone, was transported to Poland and countries of the Baltic region at the height of 1.5-3 km within 72 hours. A plume of NO2, which originated from fires in the Chornobyl Exclusion Zone on March 20, 2022, was observed in Poland the following day.References:Malytska L., Ladst&#228;tter-Wei&#223;enmayer A., Galytska E, and. Burrows J.P. Assessment of environmental consequences of hostilities: Tropospheric NO2 vertical column amounts in the atmosphere over Ukraine in 2019&#8211;2022. Atmospheric Environment 318 (2024) 120281, DOI: https://doi.org/10.1016/j.atmosenv.2023.12028