Aerosol Distributions and Transport over Southern Morocco from Ground-Based and Satellite Observations (2004–2020)

The present study investigates the optical properties of aerosols on daily and seasonal scales with the use of the aerosol optical depth (AOD) and Angström exponent (AE) data retrieved from AErosol RObotic NETwork (AERONET) and collected at four stations in Southern Morocco—Saada (31.63° N; 8.16° W), Ouarzazate (30.93° N; 6.91° W), Oukaïmeden (31.21° N; 7.86° W) and Ras-El-Aïn (31.67° N; 7.60° W). An evaluation of the aerosol volumetric size distribution (AVSD) is also obtained for Saada and Ouarzazate. An AOD inter-comparison is performed between AERONET data and satellite sensors (MODerate resolution Imaging Spectroradiometer—MODIS), as well as assimilation products (Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) and Copernicus Atmosphere Monitoring Service (CAMS)), by the means of a linear regression. Regardless of site location and elevation, the results show the prevalence of the annual cycle of AOD, with a maximum in summer and a minimum in winter. In association with this seasonal variation, the variations in AE and AVSD showed an increase in coarse mode over Ouarzazate and Saada during summer (July to August), underlining that Southern Morocco is prone to the regular transport of desert dust on a seasonal basis. The inter-comparison reveals that the MERRA-2 dataset is slightly more appropriate for the study region, since it shows correlation coefficients (r) ranging from 0.758 to 0.844 and intercepts ranging from 0.021 to 0.070, depending on the study site. The statistical analysis of the back-trajectories simulated by the HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model were consistent with the observations and confirmed the dominance of desert dust aerosols during the summer over the study region. On the other hand, the winter season reveals a predominance of anthropogenic and oceanic aerosols originating from the north and the west of the study site.

Satellite-detected tropospheric nitrogen dioxide and spread of SARS-CoV-2 infection in Northern Italy

Following the outbreak of Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) last December 2019 in China, Italy was the first European country to be severely affected, with the first local case diagnosed on 20 February 2020. The virus spread quickly, particularly in the North of Italy, with three regions (Lombardy, Veneto and Emilia-Romagna) being the most severely affected. These three regions accounted for >80% of SARS-CoV-2 positive cases when the tight lockdown was established (March 8). These regions include one of Europe's areas of heaviest air pollution, the Po valley. Air pollution has been recently proposed as a possible risk factor of SARS-CoV-2 infection, due to its adverse effect on immunity and to the possibility that polluted air may even carry the virus. We investigated the association between air pollution and subsequent spread of the SARS-CoV-2 infection within these regions. We collected NO2 tropospheric levels using satellite data available at the European Space Agency before the lockdown. Using a multivariable restricted cubic spline regression model, we compared NO2 levels with SARS-CoV-2 infection prevalence rate at different time points after the lockdown, namely March 8, 22 and April 5, in the 28 provinces of Lombardy, Veneto and Emilia-Romagna. We found little association of NO2 levels with SARS-CoV-2 prevalence up to about 130 μmol/m2, while a positive association was evident at higher levels at each time point. Notwithstanding the limitations of the use of aggregated data, these findings lend some support to the hypothesis that high levels of air pollution may favor the spread of the SARS-CoV-2 infection.

Variability of PM10 in industrialized-urban areas. New coefficients to establish significant differences between sampling points

One of the main problems that arise in the assessment of air quality in an area is to estimate the number of representative sampling points of each microenvironment within it. We present a new model that reduces the variability and increases the quality of the comparison of the sampling points. The study is based on the comparison between a city in eastern Spain, Vila-real, a macro city in México, Monterrey and the Piemonte region regarding the assessment of PM10 in microenvironments. Vila-real is located in the province of Castellón. This province is a strategic area in the framework of European Union (EU) pollution control. On the other hand, Monterrey in México, located in the northern state of Nuevo León, has several problems with particulate material in the atmosphere produced by the extraction of building materials in the hill that surround the city. Finally, the Piemonte region, which is located in the north of Italy, has to be in consideration due to higher concentrations of PM10 in the Po river basin. In the case of Vila-real the PM10 samples were collected by a medium volume sampler according to European regulations. Particle concentration levels were determined gravimetrically (EN 12341:1999). In the case of Monterrey the PM10 concentrations were determined by Beta Ray Attenuation according to US-EPA regulations. In the Piemonte region, the average concentration of PM10 was also obtained by means of the Beta Ray Attenuation as well as using gravimetric instruments. The methodology carried out in this paper is a useful tool for developing future Air Quality Plans in other industrialised areas.