ABSTRACT
Air quality is assessed by determining criteria pollutant levels in the atmosphere. While the most significant measurements are ground based, satellite remote sensing is rising as a complementary technique to reveal spatial distribution of pollutants in the integrated tropospheric column. In this work we present a new CONAE's value-added monthly product of nitrogen dioxide (NO2) for South America, derived from the tropospheric NO2 column density estimated by TROPOMI/Sentinel5p (ESA) data. Dataset generation of monthly mean, median, standard deviation and quantity of data used per pixel, along with distribution formats of downloading and visualizing data, are explained in order to provide to different users their characteristics and access. In addition, a spatial and temporal analysis is made for the Buenos Aires, Santiago and Sao Paulo cities along with ground measurements, for the august 2018 to may 2021 period and on a monthly basis. For this matter, higher values of nitrogen dioxide were observed in wintertime for the three cities, due to a greater quantity of stagnation episodes. While satellite derived data follows the temporal profile of ground-based concentrations, Santiago was the city of higher levels and bigger contrast to the summer levels. COVID-19 pandemic restrictions to traffic circulation is also noticed in the diminishing of NO2 in the two datasets, as it was also reported in previous studies. The publication of this new dataset holds the objective of supporting air quality monitoring in South America, helping non specialized users to freely access to interoperational data.
ABSTRACT
The COVID-19 outbreak measures of lockdown have generated exceptional urban behavior conditions allowing the analysis of a unique scenario. We examined the atmospheric emissions in Buenos Aires, Argentina, based on urban and industrial continuous monitoring of NO2, PM10 and PM2.5, and NO2 (TROPOMI/Sentinel-5p) and AOD (MAIAC/MODIS, Aqua) satellite products, in addition with meteorological data. We considered the time intervals before and after the announcement of lockdown, including the same periods for 2019. The results showed that NO2 and PM10 concentrations fell by similar to 30% and 44%, respectively, at urban stations during lockdown compared to 2019. An increase in PM at the industrial station (64% PM2.5 and 8% PM10) could be due to the contribution of industrial sources other than vehicle traffic. Also, we observed a reduction of the tropospheric NO2 column density mean by 54% at urban stations, and AOD values decreased between 38% and 66% during 2020. Concerning the spatial distribution, the tropospheric NO2 column showed a significant reduction of NO2 for the monthly mean in the metropolitan area at lockdown. Similarly, the AOD highest values had a greater extension for 2020 during the pre-lockdown monthly period. After the strict lockdown, concentration values increased steadily, particularly in ground-based measurements. Therefore, we were able to demonstrate the complementarity of ground-based and satellite data measurements of NO2 and aerosol to identify the effects of lockdown measures on the spatial and temporal variability of pollutants.