43    UTILIZATION OF THE MICROTOX® TOXICITY
ANALYZER IN DELINEATING SIMULATED
GROUNDWATER CONTAMINANT PLUMES
Ranee T. Shields, Environmental Engineer
Oklahoma City, Oklahoma 73120
John N. Veenstra, Professor
School of Civil and Environmental Engineering
Oklahoma State University
Stillwater, Oklahoma 74078-5033
INTRODUCTION
The passage of federal laws to protect public health and the environment has generated the
rapid growth in the field of quantitative risk assessment to provide a framework for developing
the necessary information required for environmental decision-making. Risk assessment is an estimation of the severity and likelihood of harm to human health or the environment occurring
from exposure to a toxic agent.
The initial step necessary in a risk-based evaluation is to develop a general understanding of
the site. Site characterization has typically involved collecting and analyzing field data to determine the nature and extent of potential threats to human health and the environmenl and to determine characteristics of the site. The endpoint of site characterization has been the identification
of the chemicals at a particular site that, based on concentration and toxicity, are most likely to
significantly contribute to risk due to exposure.
The identification and delineation of contaminants at sites has traditionally been obtained
through the use of chemical analysis. The costs associated with chemical-based analysis are high
and include a considerable time constraint to obtain results. Another factor to consider lies in
how to assign meaning to analytical results on a site-specific basis due to the inability of chemical analysis to define environmental impact from contamination. Presently, risk calculation requires the determination of toxicity values to assist in quantifying environmental impact by measuring the potential for contaminants to cause adverse effects to test organisms.
The high cost and long turnaround time required for chemical analysis to accurately define the
extent of contamination leads to alternative analytical methods. A need exists to provide more
rapid, less expensive, environmentally meaningful methods to determine the presence of contamination and delineate the extent of contamination to support evaluation and remediation of the
environment. Our study attempts to determine if a toxicity-based approach, using the Microtox®
Toxicity Analyzer,* can be used to delineate a simulated groundwater contaminant plume.1
BACKGROUND
Toxicology is the basic science of poisons that attempts to establish the limits of safety for
chemical agents. Rand and Petrocelli1 defined toxicity as the relative property of a chemical
which determines its potential to have a harmful effect on a living organism. Toxicity testing is a
means to evaluate the adverse effects of a chemical on living organisms under standardized, reproducible conditions which permit a comparison with other chemicals tested. The standardization of aquatic toxicity tests have been established by the U. S. Environmental Protection
"Microtox® Toxicity Analyzer is a registered trademark of Microbics Corporation.
51st Purdue Industrial Waste Conference Proceedings. 1996. Ann Arbor Press. Inc.. Chelsea. Michigan 48118.
Printed in U.S.A.
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