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 effec ts 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. Th e LIPS emission sensor was installed in an electroplating facility for a fa st monitoring of particulate emissions to provide instantaneous feedback fo r process control. The prototype was tested in cooperation with an independ ent laboratory, which determined the total chromium content and the Cr(VI)/ Cr(III) ratio in the exhaust stream by conventional filter analysis. The sy stem provided both the necessary time-resolution and detection limits (14 m u g m(-3)) for emission monitoring below the legal threshold (1 mg m(-3)) v alues. A good correlation was found between the on-line LIPS measurement an d the independent reference analysis.