RESPONSE OF MICROTOX ORGANISMS TO LEACHATES OF AUTOCLAVED CELLULAR CONCRETE

The MICROTOX bioassay, a toxicity test involving bioluminescent microo rganisms, was conducted on aqueous leachates derived from a constructi on material made using coal fly ash as the key siliceous ingredient. T he material is known as autoclaved cellular concrete (ACC). The test i ndicated an absence of toxic effects attributable to soluble species, which included the priority heavy metals in the filtered leachates. To xic or inhibitive effects on the test bacteria were observed for the t oxicity characteristic leaching procedure (TCLP) leachates, but this w as probably due to acetic acid in the extractant rather than the solub ilized metals. The ASTM (distilled-deionized water extractant) and sim ulated acid rain leachates, by comparison, produced a repeatable stimu lative effect. Stimulation observed in the form of enhanced light oupu t may be a manifestation of hormesis, a phenomenon reportedly caused b y exposure to extremely low concentrations (part-per-billion range) of otherwise toxic agents such as heavy metals.