Exploring the effect of the first lockdown due to covid-19 to atmospheric NO2 using Sentinel 5P satellite data, Google Earth Engine and Geographic Information Systems

Abstract

Air pollution is a phenomenon that plagues modern societies, causing serious impacts on both the natural and man-made environment. Air pollution is linked to specific substances which, when their concentration exceeds certain limits, become harmful and are called pollutants. Such pollutants include carbon monoxide (CO) and carbon dioxide (CO2), particulate matter (PM10), nitrogen oxides (NOX), ozone (O3), and sulfur dioxide (SO2). Fluctuations in pollutant emissions are affected by various events. An example is the first lockdown implemented on March 23, 2020 as a result of the Covid-19 disease in an effort to protect citizens. The period of lockdown was characterized by the complete suspension of various types of activities, the reduction in transport means, as well as the decrease in industrial operations, activities that significantly contribute to increased emissions. The aim of the present study is to determine the distribution and changes in the concentration specifically of nitrogen dioxide (NO2) in the prefecture of Thessaloniki, Greece. The study period is defined as the corresponding time period 04 May–04 April 2019/2020, that is, one year before and during the first lockdown. More specifically, the correlation between the lockdown and atmospheric NO2 is investigated. As part of the analysis, area characteristics such as population density and land uses are also correlated with the distribution of NO2 concentrations. To satisfy the study objectives, the technologies of satellite remote sensing and Geographic Information Systems (GIS), which are a major pillar of geoinformatics, are used. More specifically, data recording NO2 concentrations are used, which have been collected via the Sentinel 5P satellite. Based on the results obtained, it is found that the month of 2020 during which the lockdown was applied showed a very small decrease in NO2 values (4.03%) compared to the corresponding month of 2019. © 2024 Elsevier Inc. All rights reserved.