199 MAIN AIR POLLUTION SOURCES CORRELATED WITH THE TROPOSPHERIC NO 2 CONCENTRATION IN ROMANIA AS OBSERVED BY THE TROPOSPHERIC MONITORING INSTRUMENT (SENTINEL-5P) Kamill Dániel KOVÁCS * 1 , Ionel HAIDU 1 ABSTRACT. Using high-resolution Sentinel-5P satellite data, this study investigates the relationship between the main sources of air pollution and the concentration of NO 2 gas in the tropospheric column during the period 2018-2021 in Romania. NO 2 data, both raster and time series obtained through remote sensing techniques by the TROPOMI sensor were used for this analysis. Kernel density estimation (KDE) was chosen as a technique to determine the magnitude of the spatial densification of the main sources of NO 2 pollution (KDE PS). Hotspot-Coldspot analysis of the NO 2 concentration based on Local Indicators of Spatial Association (LISA) was performed using Getis-Ord Gi* statistic. Besides, a correlation and regression analysis was conducted based on a statistical T-test between KDE PS, elevation above sea level, and mean tropospheric NO 2 concentration during 2018-2021. The results evidenced that traditional air pollution sources continue to determine the NO 2 pollution levels in Romania, these levels aside being also conditioned by the elevation above sea level. We conclude that NO 2 pollution can only be reduced in polluted areas if green energy is favored and measures are taken to mitigate polluting traffic in cities. Keywords: tropospheric NO 2 , Sentinel-5P, air pollution sources, elevation, Romania 1. INTRODUCTION The aim of the new environmental policies of the European Union is to create healthier living spaces from the local to the country level (European Comission, 2017; Heinelt et al., 2018; Jordan & Adelle, 2012). A key issue in this initiative is air pollution and its anthropogenic sources (Koolen & Rothenberg, 2019; Piotrowicz & Ciaranek, 2014; Suciu et al., 2018). To achieve compliance with the air pollution reduction standards, it is necessary to know not only the magnitude but also the 1 Université de Lorraine, Laboratoire LOTERR-EA7304, Île du Saulcy, 57045 Metz, France ; Corresponding author, First author : Kamill Dániel Kovács * (email : kamill-daniel.kovacs@univ- lorraine.fr) ; Co-author(s) : Ionel Haidu (email : ionel.haidu@univ-lorraine.fr) How to cite: Kovács, K.D., Haidu, I. (2022) Main Air Pollution Sources Correlated with the Tropospheric No2 Concentration in Romania as Observed by the Tropospheric Monitoring Instrument (Sentinel-5P). 2022 ”Air and Water – Components of the Environment” Conference Proceedings, Cluj-Napoca, Romania, p. 199-216, DOI: 10.24193/AWC2022_19. DOI: 10.24193/AWC2022_19