Summary:
The objective of this thesis was the development of novel techniques for the
characterization of atmospheric aerosol physical properties. Particle surface
area is of significant importance for studies associated with air quality and
health impact assessment. Fuchs surface area represents the surface area that
is available for heterogeneous reactions and condensation of low-volatility
vapors on pre-existing particles. In the framework of this thesis, and based on
the principle of operation of the epiphaniometer, a methodology (Cascade
Epiphaniometer, CEPI) was developed for real time Fuchs surface area size
distribution measurements. The great advantage of this method is that the
surface area can be determined without any assumptions regarding particle
morphology. In addition, a methodology for the quantification of the effective
density in real-time was developed. The effective density is a parameter that
includes information not only about the chemical composition of aerosol
particles, but their shape as well. In order to confirm the developed
methodologies, calibration experiments were conducted by means of monodisperse
and polydisperse aerosols of known properties, under controlled conditions in
the ERL-Lab of NCSR “Demokritos”. These techniques were then applied for the
characterization of the physical (e.g. surface area, effective density) and
morphological properties (shape factor, fractal dimension and fractal
pre-factor) of carbon aggregates, generated by means of a spark discharge
ionization source. The physical properties of ambient aerosol were also
investigated. The measurement campaign was conducted in the urban background
monitoring station DEM-GAW/ACTRIS, located at the grounds of NCSR Demokritos.
The examined parameters were: number and Fuchs surface area size distributions,
effective density and Elemental (EC) and Organic Carbon (OC) mass
concentrations. The influence of atmospheric circulation patterns and the
possible local transport mechanisms were investigated by combined analysis of
standard meteorological parameters. The results arising from this study can
find a wide range of applications in aerosol nanoparticle technology, air
quality, environmental and health impact assessment.
Keywords:
Cascade Epiphaniometer, Fuchs surface area, Carbon fractals aggregates, Aerosol particle size distributions, Effective density, Elemental and Organic Carbon
