Prior to 2005:
The chemical composition of the regional atmospheric aerosol loading was determined using weekly bulk sampling. These samples were analysed for major inorganic and organic ion species:
- Inorganic and organic major ions:
(Cl- , NO3- , SO42-, HCO3- , CO32-, Na+, NH4+, K+, Mg2+, Ca2+, HCOOH, CH3COOH, C2H5COOH)
Aerosol samples are size discriminated using two Rupprecht and Patashnick impactors (for PM2.5 and PM10). These samples are analysed for:
- major inorganic and organic ion species (using ion chromatography)
- carbonaceous compounds (organic and black carbon; using thermooptical analyses)
- total mass (using gravimetric measurements)
- trace metals
Aerosol samples are collected using a system specifically developed for the IDAF network. Bulk particles are collected on Teflon Millipore filters, 37mm in diameter and with 1µm pores. Sampling is performed at 10m above ground level with an autonomous, mobile pumping unit composed of a 12v pump, battery and gasmeter using an average sampling duration of 24 hours. The bulk aerosol sampler operates at a flow rate of 500l/h-1.
Enough millipore Teflon filters are sent to each station for one year, in clean, individual closed containers. Bulk particle samples are collected once a week and the filters preserved by refrigeration before being sent back to the Laboratoire od’Aérologie for analysis.
In order to determine the water-soluble inorganic ion content of the aerosol, samples are extracted in 15ml of 18 MW water by ultrasonic stirring (15 min).
As for rainwater, the ion chromatography analyses carried out for aerosol samples are submitted to the WMO for quality control (see Measurement Standards).