MARGA (Monitor for AeRosols and Gases in ambient Air) has been developed by Metrohm Applikon in cooperation with the Energy Research Centre of the Netherlands. The instrument offers a new approach in which gases and aerosols sampled from the same air mass are separated from each other by selectively dissolving them in water. The resulting solutions are then analysed using ion chromatography with conductivity detection. Separating the two fractions from each other, allows the detection of important precursor gases and ionic species found in the aerosols.
Gases HCl, HNO3, HNO2, SO2, NH3
Aerosols Cl–, NO3–, SO42–, NH4+, Na+, K+, Ca2+, Mg2+
MARGA – the concept
Air to be analysed enters into a Sample Box via an appropriate inlet, typically with a cut-off of PM10 or PM2.5 (particle sizes less than 10 μm or 2.5 μm). The airflow is maintained at a constant 1 m3hr–1 by a mass flow controlled air pump. In the Sample Box water-soluble gases are quantitatively absorbed in a dilute (10 mgL–1) solution of hydrogen peroxide by using a wet rotating denuder (WRD). Aerosols pass through the WRD and are subsequently collected in a steam jet aerosol collector (SJAC).
The liquid samples from the WRD and SJAC are continuously collected during one hour by syringe pumps. After degassing and mixing with an internal standard (lithium bromide), the samples are analysed by two ion chromatographs for determination of anions and cations, respectively.
The entire instrument is controlled by a single software that runs on an integrated industrial PC.
• Simultaneous measurements of gases and aerosols
• Results every hour from same air mass
• High sensitivity for key parameters
• Unattended online operation
• Single software controls instrument and processes data
• Continuous calibration with internal standard
• All results validated by automated checks
• Results flagged with user-readable comments
• Results and all operation details recorded in easily accessible form
• Remote control and access of results possible
• Automated restart in case of temporary line power failure
The U.S. EPA Environmental Technology Verification Program (ETV) provides objective, third-party data to the environmental marketplace about the performance of new environmental technologies.
The MARGA instrument from Metrohm Applikon has been verified by this program. The full report can be found here.
Watch a video of a MARGA system operated by the Institute of Tropical and Marine Meteorology in Guangzhou, China.