Groundwater toxicity assessment using bioassay, chemical, and toxicity identification evaluation analyses

Abstract

Contaminated groundwater from a pesticide production facility was assessed using whole-organism and in-vitro bioassays to determine the potential for these tests to replace or augment traditional chemical analyses being employed at this site. The groundwater, which is contaminated with a variety of pesticides (organochlorine, organophosphorus, and carbamate insecticides) and pesticide adjuvants (spreading agents, emulsifiers, etc.) was sampled from an activated-carbon-based on-site remediation system before, during, and after the cleanup procedure. Toxicity was evaluated at each point using whole-organism (96-h acute Pimephales promelas, chronic 3-brood Ceriodaphnia dubia) and in-vitro [submitochondrial particle (SMP) and Microtox®] bioassays. Chemical indicator parameters [pentachlorophenol, gasoline-range organics (GROs), and benzene, toluene, ethylbenzene, and xylenes (BTEX)] were also measured to compare with bioassay responses. 50% effective concentrations (EC 50 ) s from the different tests indicate that the whole-organism assays were slightly more sensitive than the in-vitro assays: the order of sensitivity was C. dubia > P. promelas > SMP > Microtox®, but responses were quite similar. All assays showed decreasing toxicity as cleanup progressed, mimicking the concomitant decrease in chemical concentration parameters. A toxicity identification evaluation (TIE) analysis, conducted using the in-vitro bioassays, identified pentachlorophenol as the major contributor to toxicity in the samples with additional contributions likely from other less-prevalent compounds. Results suggest that these in-vitro tests can be credible alternatives to whole-organism bioassays for monitoring remediation of system effluents and that they can complement chemical analyses with useful effects-based toxicity data.