No abstract

No abstract

This work investigates the impact of COVID-19 restrictive measures on the mass concentrations of PM 1 and PM 10 , and their chemical components (water-soluble ions, organic and elemental carbon, and major and trace metals) at an urban site in the western Mediterranean. The evolution of gaseous pollutants (NO x , O 3 and some volatile organic compounds) was also analyzed. The concentrations measured during the lockdown in 2020 were compared to those obtained during the same period over the preceding five years. The average decrease in the levels of NO x and traffic-related volatile organic compounds was higher than 50 %, while O 3 concentrations did not exhibit significant variations during the study period. Our results show that temporal variations in PM 1 and PM 10 concentrations were strongly affected by the frequency of Saharan dust events. When these episodes were excluded from the analysis period, a 35 % decrease in PM 1 and PM 10 levels was observed. Traffic restrictions during the lockdown led to important reductions in the concentrations of elemental carbon and metals derived from road dust (e.g. Ca and Fe) and break wear (e.g. Cu). Regarding secondary inorganic aerosols, nitrate showed the largest reductions as a consequence of the drop in local emissions of NO x .

No abstract

No abstract

No abstract

Real-time measurements of ozone, NO x , aerosols and radiation were performed very close to the launch area of high intensity pyrotechnic spectacles, the so-called Mascletàs, typical of celebrations in eastern Spain. During these events, a considerable number of spectators are potentially exposed to high concentrations of pollutants directly or indirectly produced by the ignition of thousands of firecrackers at ground-level. This work is focused on the mechanism of ozone formation throughout the Mascletàs. After the initial decrease in O 3 levels (minimum concentration < 10 µg m -3 ) due to the reaction with NO emitted by fireworks explosions, peak concentrations of up to ~150 µg m -3 were recorded, clearly indicating that ozone was generated during these events. The results suggest that UV light produced by fireworks displays photolyzes O 2 releasing O to form O 3 as in the stratosphere.

From May to September 2012, ozone reductions associated with 15 Saharan dust outbreaks which occurred between May to September 2012 have been evaluated. The campaign was performed at a mountain station located near the eastern coast of the Iberian Peninsula. The study has two main goals: firstly, to analyze the decreasing gradient of ozone concentration during the course of the Saharan episodes. These gradients vary from 0.2 to 0.6 ppb h(-1) with an average value of 0.39 ppb h(-1). The negative correlation between ozone and coarse particles occurs almost simultaneously. Moreover, although the concentration of coarse particles remained high throughout the episode, the time series shows the saturation of the ozone loss. The highest ozone depletion has been obtained during the last hours of the day, from 18:00 to 23:00 UTC. Outbreaks registered during this campaign have been more intense in this time slot. The second objective is to establish from which coarse particle concentration a significant ozone depletion can be observed and to quantify this reduction. In this regard, it has been confirmed that when the hourly particle concentration recorded during the Saharan dust outbreaks is above the hourly particle median values (N > N-median), the ozone concentration reduction obtained is statistically significant. An average ozone reduction of 5.5 % during Saharan events has been recorded. In certain cases, this percentage can reach values of higher than 15 %.