Ultrafine Particles Size Distribution, Single Aerosol Particle Morphology and Chemical Composition in Urban Air
Abstract
Atmospheric ultrafine aerosol particles (UFP) were collected in Kladno, Czech Republic, in February 2016, using copper grids for transmission electron microscopy (TEM) placed on the back-up filter of a 3DRUM impactor. Concurrently, five-minute integration time data of particle number size distributions, concentration (PNC), gaseous pollutants and meteorological parameters were also registered.
The vertical profile of temperature and humidity up to 300 m was measured with a tethered balloon. The measurements of the mixing layer height revealed frequent formation of temperature inversion layer up to 50 m.
With inversion conditions and calm air (wind speed <1m.s$_(-1)) PNC rose to 2BULLET OPERATOR10$^4 #cm $^(-3), with a maximum of 4BULLET OPERATOR10$^4 #cm$^(-3), with a peak in the ultrafine size range, at 100 nm. UFP peaks occurred simultaneously with peaks of CO and SO$_2 and PM$_(10) indicating wood and coal burning for home heating.
New particles formation events with peaks at 15 nm were observed in two clear days (06 and 14.02), in the early afternoon, but not remarkable particle growth was recognized. Several types of individual particles were observed using TEM: soot-like agglomerates and aggregates with complex morphology, composed by nanospheres with diameter between 5 and 50 nm; fly ash particles; presumably individual tar-ball particles with perfect spherical shape and diameter around 100-500 nm; and ammonium sulphate particles.
No significant shape difference was observed between the aggregates sampled during nucleation events and during air pollution events. Next steps are: the chemical analysis of the single particles with electron probe microanalyzer with field emission gun (FEG-EPMA); PAHs analysis in the UFP.