Aerosol particle measurements in Uccle
RMI operates at its site in Uccle, a municipality of the Brussels region, two particle measurement instruments: an aethalometer and a nephelometer. The location can be characterised as an urban background site.
In addition to these two instruments, RMI will install, in the framework of ACTRIS, an aerosol in-situ National Facility. In this context, there will be in the near future, a mobility particle sizer (10-800 nm particle size distribution), an aerodynamic particle sizer (500 nm to 10 µm) and a total particle counter (> 7 nm).
The multi-wavelength aethalometer (Magee Sci. AE31) measures the aerosol absorption coefficient (m-1) at seven wavelengths (370, 450, 520, 590, 660, 880, 950 nm) and the mass concentration (nanogram/m3) of light-absorbing aerosol (at the 7 wavelengths). The aethalometer technique uses light-transmission through a quartz fibre filter to derive the attenuation caused by the aerosol particles. From the difference of the attenuation between two measurement intervals, the absorption coefficient and the mass concentration can be derived.
Installation: The aethalometer is installed inside an air-conditioned chamber with stable temperature and humidity conditions, under the roof of our neighbour institute, the Royal Belgian Institute for Space Aernomy. The inlet is a 3 m long, vertical, flexible conductive tubing, with the outside air intake on the top of a terrace with mainly radiation measurement instrumentation. The terrace is at around 10m height above ground with unobstructed upstream flow. There is no specific size-cut-off and the inlet is not heated. The aethalometer has been installed mid-2013 and operates since then.
The nephelometer (TSI model 3563) measures the intensity of light scattered by aerosol particles at 450, 550 and 700 nm. The instrument uses a halogen lamp as light source. The measured variables are the total scattering coefficient (m-1) and the backscatter coefficient (m-1). Calibrations with a pure reference gas (CO2) are done regularly.
Installation: At the moment, the nephelometer is not in operation due to necessary repairs. It has been installed at RMI since March 2014 during distinct time periods. After repair it will be installed at the same location as the aethalometer.