Assessment of environmental consequences of hostilities: Tropospheric NO2 vertical column amounts in the atmosphere over Ukraine in 2019–2022

Abstract

The invasion of Ukraine by Russia started on 24 February 2022. The armed conflict has been accompanied by atmospheric and soil pollution, deterioration of fresh water, and the creation of irreversible changes in ecosystems. This study focuses on the effects of hostilities on tropospheric pollution. It comprises an analysis of the spatiotemporal tropospheric NO distribution over Ukraine for the period 24 February–06 May 2022 from the TROPOMI satellite instrument. We compared the tropospheric columns of NO during the first 72 days of hostilities to values for three pre-hostilities periods: pre-COVID-19, COVID-19 lockdown and adaptive lockdown, to differentiate the effects of COVID-19 restrictions and active hostilities on NO emissions over Ukraine. We used VIIRS satellite instrument data to study fire distribution and its intensity and confirm their influence on the tropospheric NO level as well as investigate the extent to which the hostilities affect fire frequency. Additionally, we analyzed the transborder and regional air mass transport from the origin of the fires using the HYSPLIT model version 5.2 and supported it with the analysis of near-surface weather charts. The results indicate that hostilities in Ukraine have a direct impact on atmospheric pollution processes. Hostilities resulted in an unprecedented reduction in economic activity, comparable to the COVID-19 pandemic lockdown, and correspondingly, reduced NO emission in industrial areas, which equals about 2–4 × 1015 molec cm−2, whereas the NO concentration locally increased in the areas of conflict. While we detected temporal NO decline, hostilities negatively affected air quality in Ukraine due to the significant increase in frequency and intensity of fires, especially in conflict-related areas. Air pollution, in the case of one-off strikes, tends to be a short-term phenomenon, but frequent attacks on large military targets cause atmospheric consequences on local as well as on regional levels. During the first 72 days of hostilities, we linked bursts of fires with significant air pollution over northern (Kyiv and Zhytomyr regions), southern (Odesa, Kherson regions), and eastern (Donetsk region) parts of Ukraine. Based on the TROPOMI and VIIRS data, it was figured out that forest fires over the Kyiv region and Chornobyl Exclusion Zone, driven by military actions on 19–23 March 2022, caused the NO content increase from 3 to 17.5 × 1015 molec cm−2, which is comparable to the most polluted Ukrainian industrial cities during the pre-hostilities period. As a result, the most affected territories were located within 50 km of active fires, but air quality deterioration was observed at a distance of about 200 km downwind. HYSPLIT version 5.2 forward trajectories simulation showed that a smoke-particle-included air mass, related to the fires in the Chornobyl Exclusion Zone was extended to Romania, Serbia, Kosovo, and Albania towards the Mediterranean Sea at the height of 530 m. At 1.5–3 km altitudes, the air parcels were transported to Poland and countries of the Baltic region. At 3 km height, the air mass reached the Russian Federation in 72 h.