Acute toxicity screening of Hanford Site waste grouts using aquatic invertebrates

Waste grouts prepared by mixing a simulated nonradioactive liquid waste with a dry solids blend consisting of cement, fly ash, and clay were screened for their acute toxicity using aquatic invertebrates (D. magna, D. pulex, and C. dubia) as test organisms and a fluorogenic substrate (4-methylumbelliferyl b-d galactoside) as the toxic stress indicator. After one hour of exposing juvenile daphnids to grout extracts of varying concentrations, followed by a 15-minute reaction with the fluorogenic substrate, the degree of in vivo enzymatic inhibition was measured by the number of resulting fluorescent daphnids. The effective concentration at which 50% of the daphnids were adversely affected (EC50) values calculated by probit analysis were 2,877 mg/L, 2,983 mg/L, and 3,174 mg/L for D. pulex, D. magna, and C. dubia, respectively. The results indicated that the grout extracts studied are nonhazardous and not dangerous to daphnids