MICROBIAL BIOASSAYS TO ASSESS THE TOXICITY OF SOLID-ASSOCIATED CONTAMINANTS

Due to the effects that sediment or soil matrices have on the bioavail ability of compounds, it has been difficult to screen toxicity of soli d-associated contaminants. The majority of microbial assays for testin g toxicity of soils and sediments have been performed on water or solv ent extracts. These procedures lead to a fractionation of the toxicity , which may underestimate or overestimate exposure routes and conseque ntly potential adverse environmental effects. Recently, a solid-phase Microtox assay which eliminates the need for soil extracts and utilize s whole sediments or soils has been developed. This report describes a toxicity testing procedure using the inhibition of dehydrogenase enzy me activity of Bacillus cereus as test parameter. Studies with soil sa mples and a synthetic sediment spiked with organic contaminants and co pper indicate the higher sensitivity of both solid-phase bioassays com pared to water extract testing. A comparison of the results demonstrat es that the B. cereus contact test is more sensitive for copper than t he Photobacterium phosphoreum solid-phase test. (C) 1995 Academic Pres s, Inc.