Impact of SARS-CoV-2 lockdown and de-escalation on air-quality parameters.

The SARS-CoV-2 health crisis has temporarily forced the lockdown of entire countries. This work reports the short-term effects on air quality of such unprecedented paralysis of industry and transport in different continental cities in Spain, one of the countries most affected by the virus and with the hardest confinement measures. The study takes into account sites with different sizes and diverse emission sources, such as traffic, residential or industrial emissions. This work reports new field measurement data for the studied pandemic period and assesses the air quality parameters within the historic trend of each pollutant and site. Thus, 2013-2020 data series from ground-air quality monitoring networks have been analysed to find out statistically significant changes in atmospheric pollutants during March-June 2020 due to this sudden paralysis of activity. The results show substantial concentration drops of primary pollutants, including NOx, CO, BTX, NMHC and NH3. Particulate matter changes were smaller due to the existence of other natural sources. During the lockdown the ozone patterns were different for each studied location, depending on the VOCs-NOx ratios, with concentration changes close to those expected from the historical series in each site and not statistically attributable to the health crisis effects. Finally, the gradual de-escalation and progressive increase of traffic density within cities reflects a slow recovery of primary pollutants. The results and conclusions for these cities, with different sizes and population, and specific emission sources, may serve as a behavioural model for other continental sites and help understand future crises.

Fine and ultrafine particles in small cities. A case study in the south of Europe.

Ultrafine particles, PM2.5 and PM10 mass concentration, NO(x), Ozone, SO2, back-trajectories of air masses and meteorological parameters were studied in a small city over the period February, 2013 to June, 2014. The profiles of PM2.5 and PM10 particles are provided, showing averaged values of 16.6 and 21.6 µg m(-3), respectively. The average number concentration of particles in the range of diameters 5.6-560 nm was 1.2 × 10(4)#/ cm(3) with contributions of 42, 51 and 7% from the nucleation, Aitken, and accumulation modes, respectively. The average number concentration of ultrafine particles was 1.1 × 10(4)#/ cm(3). The results obtained are evidence for some differences in the pollution of ambient air by particles in the studied town in comparison to bigger cities. Nucleation events due to emissions from the city were not observed, and traffic emissions amount to a small contribution to PM2.5 and PM10 particles which are mainly due to crustal origin from the arid surroundings and long-range transport from the Sahara Desert.