A Decision‐Making Framework for Sediment Contamination

Abstract

A decision-making framework for determining whether or not contaminated sediments are polluted is described. This framework is intended to be sufficiently prescriptive to standardize the decision-making process but without using ''cook book'' assessments. It emphasizes 4 guidance ''rules'': (1) sediment chemistry data are only to be used alone for remediation decisions when the costs of further investigation outweigh the costs of remediation and there is agreement among all stakeholders to act; (2) remediation decisions are based primarily on biology; (3) lines of evidence (LOE), such as laboratory toxicity tests and models that contradict the results of properly conducted field surveys, are assumed incorrect; and (4) if the impacts of a remedial alternative will cause more environmental harm than good, then it should not be implemented. Sediments with contaminant concentrations below sediment quality guidelines (SQGs) that predict toxicity to less than 5% of sediment-dwelling infauna and that contain no quantifiable concentrations of substances capable of biomagnifying are excluded from further consideration, as are sediments that do not meet these criteria but have contaminant concentrations equal to or below reference concentrations. Biomagnification potential is initially addressed by conservative (worst case) modeling based on benthos and sediments and, subsequently, by additional food chain data and more realistic assumptions. Toxicity (acute and chronic) and alterations to resident communities are addressed by, respectively, laboratory studies and field observations. The integrative decision point for sediments is a weight of evidence (WOE) matrix combining up to 4 main LOE: chemistry, toxicity, community alteration, and biomagnification potential. Of 16 possible WOE scenarios, 6 result in definite decisions, and 10 require additional assessment. Typically, this framework will be applied to surficial sediments. The possibility that deeper sediments may be uncovered as a result of natural or other processes must also be investigated and may require similar assessment.

Sediment contact tests as a tool for the assessment of sediment quality in German waters

“…Therefore, thorough sediment characterization is essential. At present, weight-of-evidence approaches, such as the sediment quality triad [4,5], are widely accepted to assess the ecological risk of sediment-bound contaminants [6]. In addition to chemical analysis and in situ benthic community assessment, toxicity testing with single species forms the third part of the sediment quality triad.…”

“…Despite broad consensus in the scientific community that whole-sediment exposure protocols are indispensable for realistic scenarios simulating in situ exposure conditions [5,7], the respective environmental regulations and guidelines in Germany predominantly demand aquatic bioassays for testing aqueous extracts or porewater obtained from the sediments. For example, a successful battery of standardized bioassays using aquatic organisms from the three trophic levels (algae [green algae; ISO 8692], bacteria [luminescent bacteria; ISO 11348], and invertebrates [Daphnia magna; ISO 6341]) is part of the guideline for the assessment of dredged material in German Federal Waterways [8,9].…”

The Effect of Organism Density on Bioaccumulation of Contaminants from Sediment in Three Aquatic Test Species: A Case for Standardizing to Sediment Organic Carbon

“…An assessment of the potential for the biomagnification of contaminants is one of the four lines of evidence currently used in decisionmaking frameworks for the assessment of sediments (Chapman and Anderson 2005;Grapentine et al 2002). Laboratory methods to assess the toxicity (i.e., impact on growth, survival, and reproduction) of sediments have been standardized (e.g., Environment Canada 1997a, b; United States Environmental Protection Agency [USEPA] 2000).…”

Validation of Ontario's new laboratory‐based bioaccumulation methods with in situ field data

“…However, the assessment of the potential for bioaccumulation and/or biomagnification of contaminants has been identified as crucial to this process [1,2] and is now an important and routine part of environmental assessments [3,4]. Several approaches are available for determining the bioaccumulation of contaminants in biota, which includes field monitoring, laboratory tests, and the use of models.…”