Journal of Radioanalytical and Nuclear Chemistry, Articles, VoL 167, No. 2 (1993) 259-269 STUDY OF SIZE-FRACTIONATED COAL-COMBUSTION AEROSOLS USING INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS W. MAENHAUT,* E. I. KAUPPINEN,** T. M. LIND** "Institute for Nuclear Sciences, Proeftuinstraat 86, B-9000 Ghent (Belgium) **TechnicalResearch Center of Finland (VTT), Laboratory of Heating and Ventilation (L VI), Tekniikantie 4, SF-02150 (Finland) (Received September 22,1992) The chemical composition of aerosols emitted during coal combustion was studied as a function of particle size down to 0.01 Ixm.The aerosol collections were carried out in a 81 MW capacity boiler that burned Venezuelan coal in a circulating fluidized bed combustion chamber. The samples were collected upstream of the electrostatic precipitator using a Bemer low-pressure impactor, which was equipped with a cyclone pre-eutter to avoid overloading of the first impaction stages. The samples were analyzed by INAA for up to about 40 dements. The elemental coneentratious in the particulate matter for each impaction stage were plotted as a function of stage number (particle size). For the dements Na, A1, K, Ca, So, Ti, V, Ga, La and Sin, the concentration variation was limited to a factor of 2 to 4, and the concentrations of these elements were lower for the initial and final impactor stages than for the intermediate particle sizes. The variations were also limited to a factor of 2-4 for Mn, Fe, As, Sb and Th, but all these elements showed increasingconcentrations with decreasing particle size. Still other elements, such as Ni, Cr, Co, Zn, W, Mo and the halogens, were highly enriched (up to 20-100 fold) in the fine particles when compared with the coarse particles. Ia~odagtion The chemical composition of particles emitted during coal combustion has been the subject of many studies since the early seventies. In several of these studies, the composition of aerosol particles formed in power plant scale combustion processes has been investigated as a function of particle size. Such measurements usually relied on bulk analysis of size-fractionated samples. 1-10 Occasionally, also techniques such as electron probe microanalysis (EPMA), which allow the analysis of individual particles, have been applied, 11"13 using then either size-segregated or total particulate samples. Especially the submicrometer particles, which are believed to be formed by nuclea- tion of vaporized ash components and growth through coagulation and heterogeneous condensation, have received a lot of attention. Such particles are enriched in several potentially toxic constituents, have long residence times in the atmosphere and ate able to penetrate into the alveoli of the lungs when inhaled. The composition of fine combustion aerosols may vary considerably, though, depending upon the composition of the parent coal and on the combustion process. The great majority of studies have concentrated on pulverized coal boilers. Further- more, few multielement data sets have been reported for size-fractionated particles ElsevierSequoia S. A., Lausanne AkaddmiaiKiadr, Budapest