Investigation on the geometric and matrix effects and quantitative determination of K, Cl and S atomic fraction for biomass burning particles by Monte Carlo simulation

Using Monte Carlo simulation, the geometric and matrix effects on intensity and intensity ratio measured by EPMA were investigated for both synthetic particles and biomass burning particles. Three particulate standards, KCl, KSO4, KHSO4. were prepared and measured along with biomass burning particles. The modified CASINO program (University of Sherbrooke, Quebec, Canada) at the University of Antwerp, Belgium was used. The relative intensities obtained by the UA version of the CASINO program appear to be in line with those from experiments. The CASINO program and iterative procedures were applied to quantitatively determinate the atomic fraction of K, Cl and S in particulate standard and real samples. After correcting the geometric and matrix effects, the atomic fraction ratio of K to Cl in KCl sample was found to be 1.007 +/- 0.025, 0.996 +/- 0.013 and 1.011 +/- 0.019 for experiments with high voltages of 15, 20 and 25 keV, respectively. The same procedure was also applied to K2SO4 and KHSO4 standard particle sample. The atomic fraction ratio of K to S was 1.945 +/- 0.049 (25 keV) for K2SO4 and 1.014 +/- 0.072 (20 keV) for KHSO4. These ratios obtained are close to the theoretic values 1 or 2. Reasonable data were obtained for biomass burning particles, indicating that it is possible to perform chemical speciation. (C) 2002 Elsevier Science B.V. All rights reserved.