INTERCOMPARISON OF TRACE-ELEMENT DETERMINATION IN SAMPLES FROM A COAL-FIRED POWER-PLANT

The combustion of fossil fuels, e.g. coal, is one of the anthropogenic sources of hazardous trace element emissions. This interlaboratory st udy was arranged to test and improve the quality of trace element anal ysis of different types of samples from a coal-fired power plant. Samp les of coal, fly ash, by-product from flue gas desulphurisation (=FGD product, consisting mainly of CaSO3 and CaSO4), and two different abso rption media used for the sampling of vaporous metals and metalloids i n flue gases were sent to be analyzed for Al, As, Be, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, Tl, V and Zn by different Finnish laboratories usi ng mainly atomic spectroscopic methods. In addition, neutron activatio n analysis and X-ray fluorescence spectroscopy were employed. 12 labor atories took part in the analysis of a HNO3 sample, 5 in the analysis of a K2Cr2O7/HNO3 sample, 15 in the analysis of a fly ash sample, 9 in the analysis of a coal sample, and 7 in the analysis of a sample of t he by-product from flue gas desulphurisation. The results were evaluat ed both in terms of interlaboratory agreement and in comparison with d ifferent digestion and analytical methods used in the intercomparison. The magnitude of the deviations of the results clearly indicated a ne ed to develop the quality of power plant sample analysis. Considering the methods used, it was concluded that the composition of the acid mi xture used for the digestion of solid samples is more decisive than th e method of heating during the digestion.