Application of a sediment Toxicity Identification Evaluation in support of Total Maximum Daily Load development for the Calcasieu Estuary

Abstract

A Toxicity Identification Evaluation of sediments from various reaches of the Calcasieu Estuary in Louisiana was performed to improve the technical basis for Total Maximum Daily Loads under development for this water body. The Toxicity Identification Evaluation methodology involved manipulations of the physical/chemicalproperties of sediment pore water samples in order to sequentially remove or bind each of the major classes of contaminant compounds and confounding factors. Toxicity tests were performed in conjunction with these manipulations to directly correlate reduction in toxicity with the specifically targeted contaminant classes. Toxicity of sediment porewaters from seven locations was evaluated using the amphipod, Ampelisca abdita and the mysid, Americamysis bahia. Toxicity Identification Evaluation results demonstrated improved survival after filtration, indicating that suspended particulates and associated contaminants were a significant source of toxicity. Subsequent treatments with column extraction and ethylene diamine tetra amino acid reduced toxicity, indicating both organics and metal constituents of pore waters as contributors to toxicity. The analysis of the filters used in the Toxicity Identification Evaluation revealed that particulate copper in the porewater was above criteria values, indicating that adverse exposure potential existed from the particulate phases, and that shifts in partitioning equilibrium could mediate dissolved-phase exposures. The identification of specific contaminant classes as well as particulate effects as sources of acute toxicity from Toxicity Identification Evaluation results indicate that in place sediment contamination as well as pore water flux and resuspension are likely contributors to habitat impairment that should be considered in Total Maximum Daily Load development.

Application of toxicity identification evaluation to sediment in a highly contaminated water reservoir in southeastern Brazil

“…The recommendation of the present work agrees with the approach proposed by the U.S. Environmental Protection Agency that TIE procedures should be applied as an extra step in a regulatory measure or framework to identify the causes of toxicity in aquatic ecosystem sediments to support total maximum daily load decisions that depend on identifying types and degrees of specific (chemically speaking) loads that should be restricted in a drainage basin [33]. This statement is rather important for many countries, including Brazil, where CON‐AMA 357/05 (Brazilian National Council for the Environment), a federal environmental resolution, also requires the application of the total maximum daily load framework.…”