The detection system is continuously controlled by an internal calibration, performed by the addition of a standard solution containing anions and cations normally not present in ambient
Marga measures the concentration of inorganic species in aerosols and their related gas phase components in ambient air.
A mass flow controlled airpump draws 1m3 ambient air per hour through the sampling box.
The size of particulate matter (PM) could be selected by placing special designed cyclones (PM 10 or PM 2.5um) before the entrance of the sampling box.
In this box water soluble gases are quantitatively (more than 99.7%) absorbed in a wetted rotating denuder (WRD).
Based on the difference in diffusion velocity of aerosols and gases, the aerosols will pass the WRD and are trapped in the steam-jet aerosol collector (SJAC) which is connected to the WRD.
By steam injection a water supersaturated condition is created, forcing a water vapour condensation process.
By condensational growth aerosols are quantitatively (more than 99.7%) separated from the airstream in a cyclone.
The liquid streams from the WRD and SJAC are collected during exactly one hour in 25ml burettes located in the Analytical box.
These samples are degassed and mixed with an internal standard and than controlled injected in anion and cation chromatographs.
The ion chromatograph's sensitivity is sufficient to reach sub 0.1ug/m3 detection limits at a 1m3/h air sampling flow converted into a 25ml liquid sample volume.
For lower detection limits a so-called concentrator column could be applied.
