Investigation of the intense wildfire events and NH3 levels over the Eastern Mediterranean

South eastern Mediterranean region of Türkiye is well known with intense industrialization, shipping activities, agriculture and livestock production in addition to urban emission sources, thus struggle with significant air pollution problems. In addition to criteria pollutants, combination of these sources also results in high ammonia (NH₃) levels in the region.

NH₃ is released into the atmosphere mainly from agriculture, including nitrogen-based fertilizer applications and livestock farming as well as from several industries and from biomass burning. Atmospheric NH₃ plays a significant role in the formation of secondary inorganic particulate matter (PM), which negatively impacts on human health and ecosystems and indirectly influences climate change by altering radiative forcing. Climate change has increased the frequency and intensity of wildfires globally, which became another significant source of NH₃ over the Eastern Mediterranean, because the region is among the most sensitive regions. Besides wildfires, agricultural residue burning, although prohibited, also contributes to overall NH₃ levels.

Biomass burning contributes to atmospheric pollutants, as the combustion process emits nitrogen and carbon compounds from organic matter. In this study, multi-satellite derived retrievals were utilized, including IASI Level-2 NH₃ and CO, TROPOMI Level-2 NO₂, CO, and HCHO along with VIIRS S-NPP Fire Radiative Power product to investigate biomass burning related NH₃ levels. Products were processed at a 1x1km² gridded resolution to analyse spatio-temporal variations from 2019 to 2023, especially focusing on intense fire time intervals. While NH₃ levels were generally high during the summer over the region, the 2021 summer stood out with exceptionally high levels, coinciding with intense wildfires recorded that year. Similarly, CO levels revealed elevated levels during the same period, further strengthening the common impact of these extreme events. Further, fires detected over some areas by the VIIRS product were associated with residue-burning practices, as the area predominantly consists of agricultural lands.

The aim of the study is to investigate the impacts of fire-related NH₃ levels and quantify NH₃ enhancements during these fire events in the region. In this context, NH₃ to other pollutant ratios will be examined and temporal variation between different biomes will be classified. Air quality and climate change impact studies over the Mediterranean are critically important, with the absence of ground-based NH₃ measurements, satellite retrievals have to be utilized more to investigate the sensitivity of the region to extreme biomass burning events with the growing impacts of climate change.

Keywords: ammonia, carbon monoxide, nitrogen dioxide, biomass burning, wildfires

Acknowledgements: IASI is a joint mission of EUMETSAT and the Centre National d'Etudes Spatiales (CNES, France). The authors acknowledge the AERIS data infrastructure for providing access to the IASI data in this study and ULB-LATMOS for the development of the retrieval algorithms. This study was supported by the Scientific and Technological Research Council of Türkiye under the grant number 123Y364.