In front of the recent sanitary emergency, due to the Covid-19 pandemic, great emphasis has been placed on the determination of a possible correlation between air pollution and respiratory viral infections. During respiratory events, a bioaerosol of droplets, made mostly by water, is produced; these droplets can interact with air pollutants, enhancing their lifetime and hindering their natural evaporation process. In this study, the evaporation rate of water droplets has been evaluated in terms of particle size distribution at different residence times. Exhausts emitted by internal combustion engines were bubbled in demineralized water; the resulting solutions, after an absorption spectra analysis, were aerosolized and sent to a specially designed flow reactor to estimate droplets evaporation rates in polluted environments. Subsequently, diluted exhausts from selected vehicles were sent directly to the reactor along with an aerosol of demineralized water droplets. Using demineralized water solution as reference, the first results showed in both cases an important delay in the evaporation process after 4 seconds; the strongest effect was detected when the emissions directly invested the water droplets. According to the experimental results, average evaporation rate constants were evaluated following the classical d2 law and corrective factors were estimated to apply the law in the case of a polluted environment. The study indicated that in the presence of combustion related products an increase of water droplets lifetime can be observed; in particular, for the system of diesel engine emissions and water droplets the effect of the presence of pollutants can be detected after 1 second and a global delay of 2 seconds in the evaporative process is observed compared to the reference.
THE EFFECT OF POLLUTANTS ON WATER DROPLETS EVAPORATION
M Commodo;
2021
Abstract
In front of the recent sanitary emergency, due to the Covid-19 pandemic, great emphasis has been placed on the determination of a possible correlation between air pollution and respiratory viral infections. During respiratory events, a bioaerosol of droplets, made mostly by water, is produced; these droplets can interact with air pollutants, enhancing their lifetime and hindering their natural evaporation process. In this study, the evaporation rate of water droplets has been evaluated in terms of particle size distribution at different residence times. Exhausts emitted by internal combustion engines were bubbled in demineralized water; the resulting solutions, after an absorption spectra analysis, were aerosolized and sent to a specially designed flow reactor to estimate droplets evaporation rates in polluted environments. Subsequently, diluted exhausts from selected vehicles were sent directly to the reactor along with an aerosol of demineralized water droplets. Using demineralized water solution as reference, the first results showed in both cases an important delay in the evaporation process after 4 seconds; the strongest effect was detected when the emissions directly invested the water droplets. According to the experimental results, average evaporation rate constants were evaluated following the classical d2 law and corrective factors were estimated to apply the law in the case of a polluted environment. The study indicated that in the presence of combustion related products an increase of water droplets lifetime can be observed; in particular, for the system of diesel engine emissions and water droplets the effect of the presence of pollutants can be detected after 1 second and a global delay of 2 seconds in the evaporative process is observed compared to the reference.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
