Environment

We deal with aerosol sampling and analysis. The sampling stations are equipped by the two-stage GENT samplers allowing the separation of PM10-2.5 and PM2.5 fractions. For proper operation an air flow of 15 l/min is required. Normally, the aerosols are deposited onto the 8 µm and 0.4 µm Nuclepore filters. If longer exposure times than 1 day are needed the PM10 dust is collected onto the quartz filters. These samplers are occasionally equipped by meteorological station, measuring the wind speed and direction, as well as the air temperature and humidity. As an option, the station commands the valve controller which directs the air flow into different samplers, according to the actual wind direction and speed and therefore allows the long-term dust sampling in correlation with the specific wind conditions.

GENT in action GENT sampling head

From the left: 1) Gent sampler in action, 2) view of the sampling head.

A fine particle size distribution can be measured by the cascade impactor which allows a collection of 9 size fractions in parallel, sorting the dust particles in the size range from 60 nm up to 16 µm. A streaker sampler is used if longer, time resolved measurements of PM10 concentrations (1 hour resolution) are required. In this case the air flow is restricted to 1 l/min.

bits of the cascade impactor A loaded streaker filter

From the left: 3) bits of the cascade impactor, 4) A loaded streaker filter.

Analysis of aerosol samples can be done by precise weighting (usually only weekly samples) or by PIXE method. Concentrations for a range of elements (Ka lines from Na to Mo, also La lines: Pb, Bi..) can be measured simultaneously by two x-ray detectors which observe the sample excited by 2 MeV protons.

Principle of PIXE method PIXE experimental station

Above from the left: 5) Principle of PIXE method, 6) PIXE experimental station @ MIC. Below: 7) An example of aerosol PIXE spectrum.

Aerosol PIXE spectrum

The spectral analysis which finally yields the elemental concentration in 1 m3 of air on the sampling site, averaged over the sampling time, is usually done with the GUPIX code. Using the ion beam with 1.5 x 1.5 µm2 beam cross section, single aerosol particles can be studied, provided they are larger than 1 µm. If in addition, the x-ray detector is equipped with collimating polycapillary optics, a sensitive microvolume is formed which allows a profiling of aerosol particles in 3 dimensions (3D tomography).

Ion microbeam set-up map of Fe in aerosol sample

From the left: 8) Ion microbeam set-up with x-ray detector equipped by polycapillary optics, 9) 100 x 100 µm2 map of Fe in aerosol sample recorded with polycapillary optics.

In this field we are recently collaborating with:

Contact person:

Dr. Matjaž Žitnik


Last updated: 01/22/2014