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IDENTIFICATION AND EVALUATION OF STRESSORS IN TOXIC SEDIMENTS AND DREDGED MATERIALS
Citation:
Ho, K T. IDENTIFICATION AND EVALUATION OF STRESSORS IN TOXIC SEDIMENTS AND DREDGED MATERIALS. Presented at MIT Conference on Options for Dredged Material Disposal Management, Cambridge, MA, December 3-6, 2000.
Description:
Identification of stressors in aquatic systems is critical to sound assessment and management of our nation's waterways for a number of reasons. Identification of specific classes of toxicants (or stressors) can be useful in designing effective sediment remediation methods and reasonable options for sediment disposal. Knowledge of which stressors affect benthic systems allows managers to link stressors to specific dischargers and prevent further release of the toxicant. In addition, identification of major causes of toxicity in sediments may guide programs such as sediment quality guidelines and pesticide registration, while knowledge of the causes of toxicity which drive ecological changes such as community structure would be useful in performing ecological risk assessments. To this end, the US Environmental Protection Agency has developed tools (Toxicity Identification and Evaluation (TIE)) that allow researchers to characterize and identify chemical causes of acute toxicity in sediments and dredged materials. Development of these methods for both interstitial waters and whole sediments is nearly complete, and a guidance document is expected by the end of 2001.
To date, most sediment TIEs have been performed on interstitial waters. Preliminary evidence from the use of interstitial water TIEs reveals certain patterns in causes of sediment toxicity. First, among all sediments tested, there is no one predominant cause of toxicity; metals, organics and ammonia all playa role in about equal amounts in c~using toxicity. Second, within a single sediment there are usually multiple causes of toxicity; not just one chemical class is present. Finally, if sediments are divided into marine or freshwater sediments, TIEs performed on freshwater sediments indicate a variety of toxicants in fairly equal proportions, while TIEs performed on marine sediments have identified only ammonia and organics as toxicants, with metals playing a minor role. However, it is necessary to keep in mind that a very small number of interstitial water TIEs have been performed, and these trends may change as larger numbers of TIEs (both interstitial and whole sediment) are performed.
Results from interstitial water TIEs will be discussed. Methodology and results from whole sediment TIEs will also be discussed along with advantages, limitations and application of these methods.