Changes in ambient particulate matter during the COVID-19 and associations with biomass burning and Sahara dust in northern Colombia

The restriction of mobility due to preventive social isolation has improved air quality in many regions of the world. At the same time, global and regional atmospheric phenomena such as biomass burning or dust transport from Sahara can exacerbate particulate matter (PM) mass. In this study, PM(10) and PM(2.5) concentrations were evaluated in industrial and urban areas during the lockdown period due to COVID-19 in northern Colombia. Aerosol Optical Depth (AOD) observations obtained from the spaceborne MODIS (MOD04-3k) and the active fire data was obtained from VIIRS Active Fire. We measured surface contamination at several stations to quantify the PM(10) and PM(2.5) changes associated with the general closure of anthropogenic and industrial activities driven by COVID-19 and by the macroscale and/or mesoscale contributions. In the industrial zone, a slight decrease in daily concentrations was detected at the stations located near the mining operations. In the urban area, the decrease is more salient in COVID-19 lockdown. A reduction rate in the daily averages of PM10 of 23.3%, 6.0%, and 19.0% was observed in the SCa, SBi, and SUn stations, respectively. The biomass burning episode has contributed 52% to the daily average of PM(10) and 45% to the daily average of PM(2.5). The episode due to the passage of Saharan dust through the Caribbean Sea has contributed 79% to the daily average of PM(10) (150.75 μg/m(3)) and on 57% to the daily average of PM(2.5).