ENVIRONMENTAL CONTAMINATION BY COBALT IN THE VICINITY OF A CEMENTED TUNGSTEN CARBIDE TOOL GRINDING PLANT

Surface soil and dust samples have been collected from the vicinity of a hard metal (cemented tungsten carbide) tool grinding factory. As a result of poor waste management practices, dusts generated by the grin ding operation were, for the most part, swept from the interior of the building onto open ground at the rear of the plant. The potential for contamination of the local environment with cobalt, tungsten, and oth er metals as a result of dust being either resuspended from the result ing uncontrolled mound of debris or emitted from the factory vents was considerable. Levels of cobalt in local soils were found to be as hig h as 12,700 mg kg(-1); almost 2000 times higher than the average value for in the United States. Scanning electron microscopy and energy dis persive X-ray microanalysis examination of the waste dust particles re vealed that the individual particles were, in general, composites cont aining variable quantities of tungsten, cobalt, calcium, titanium, and iron. Individual particles in soil samples collected at some distance from the plant were less heterogenous, and fewer particles contained detectable quantities of cobalt. This would suggest that a degree of d isassociation had occurred in the soil environment resulting in a mobi lization of the cobalt. (C) 1995 Academic Press, Inc.