The US-EPA has signed a long-term contract for the supply of up to 40 Marga systems for its Castnet measurement network across the US.
There are an additional nine Marga systems located in Scotland, South Korea, the Netherlands and China.
Marga (monitor for aerosols and gases in ambient air) is an ambient air monitoring system that is capable of measuring the gas phase concentrations of NH3, HNO3, HCl, HNO2 and SO2, as well as the particulate matter (aerosol) concentrations of NO3-, Cl-, SO42-, NH4+, Na+, K+, Ca2+ and Mg2+.
This instrument, developed by Applikon Analytical in cooperation with the Dutch Energy Research Institute (ECN), draws in a 1m3 volume of air each hour.
The gases are then quantitatively (more than 99.7 per cent) absorbed in a wetted rotating denuder (WRD) and the aerosols, which pass through the WRD, are trapped in the steam-jet aerosol collector (SJAC).
The trapped aerosols are quantitatively (more than 99.7 per cent) separated from the air stream cyclone using condensational growth with supersaturated steam.
The liquid streams from the WRD (dissolved gases) and SJAC (dissolved aerosols) are degassed and mixed with an internal standard before controlled injection into an anion and a cation ion chromatograph, both from Metrohm.
The determinations are continuously controlled by an internal calibration, performed by the addition of a standard solution (Li and Br).
The instrument can operate for seven days unattended and can be controlled via an internet connection.
The size of particulate matter (PM) can be selected by placing special designed cyclones (for example, PM10, PM2.5 or PM1.0) before the entrance of the sampling system.
