Field measurement comparison of aerosol metals using aerosol beam focused laser-induced plasma spectrometer and reference methods

Several tests were conducted in July 2002 on an instrument developed by researchers at the Oak Ridge National Laboratory (ORNL) for in-situ, real-time measurement of metal-laden aerosol particles in flue gas from combustion facilities. Stock aqueous solutions of prepared metal concentrations were nebulized and injected into the flue gas to provide spikes for the instrument testing. Strengths of the solutions were designed such that a reference method (RM) was able to obtain a sufficient amount of material on filter samples in 30 min cycles; the collected filters were subsequently analyzed in an analytical laboratory using certified methods. Parallel aerosol measurements were performed by one operator using the ORNL instrument. The recorded signal of an individual element was analyzed using the Lorentzian model and the concentration calculated from a calibration curve that was established prior to the experiments. RM data were able to reflect the loads simulated in the spiked waste stream. However, data collected using the RM was unable to reflect the transient load condition in the flue gas and missed a sample containing beryllium. The possibility of bias in the RM determination of chromium could exist. With the real-time detection capability, the instrument was able to reveal the transient emission variation by making seven consecutive measurements within a 30 min cycle. The measurements for mercury by both techniques appeared to be in good agreement. Further improvement of the system includes the development of user-friendly software for modeling, data analysis tools, and packaging suitable for field transportation.