On-line monitoring of chromium aerosols in industrial exhaust streams by laser-induced plasma spectroscopy (LIPS)

Ultrafine heavy metal aerosols can have severe toxic and carcinogenic effects when inhaled in higher concentrations. The objective of this work was to develop a mobile continuous emission monitor (CEM) based on laser-induced plasma spectroscopy (LIPS) for an on-line analysis of chromium aerosols. The LIPS emission sensor was installed in an electroplating facility for a fast monitoring of particulate emissions to provide instantaneous feedback for process control. The prototype was tested in cooperation with an independent laboratory, which determined the total chromium content and the Cr(VI)/Cr(III) ratio in the exhaust stream by conventional filter analysis. The system provided both the necessary time-resolution and detection limits (14 mu g m(-3)) for emission monitoring below the legal threshold (1 mg m(-3)) values. A good correlation was found between the on-line LIPS measurement and the independent reference analysis.