VIEWPOINT
Sediment Quality Values (SQVs) and Ecological Risk Assessment (ERA)

https://doi.org/10.1016/S0025-326X(99)00033-8Get rights and content

Abstract

A wide variety of sediment quality values (SQVs) have been promulgated. Ecological risk assessment (ERA) provides a framework for objectively and systematically evaluating the risks posed by environmental contamination to ecological resources. SQV application to ERA should be restricted to the initial problem formulation stage where they can be used either alone (i.e., in jurisdictions with accepted SQVs) or in a weight-of-evidence approach (i.e., multiple SQV types; in jurisdictions without accepted SQVs) to screen out contaminants posing negligible risks to ecological receptors.

Introduction

Sediments have long been recognized as a sink for many contaminants discharged into surface water bodies. Contaminated sediments can result in adverse ecological effects to sediment-associated biota (e.g., macrophytes, benthos, demersal fish) and to higher-level biota (e.g., pelagic fish and aquatic birds). Regulatory environmental protection efforts in most jurisdictions now recognize sediments as a critical portion of aquatic ecosystems, and require their evaluation for dredging activities or for other potential remediation. Assessing potential impacts of contaminated sediments has traditionally relied on comparison of sediment chemistry to sediment quality values (SQVs), and/or field and laboratory studies. Most SQVs were not intended as remediation criteria; therefore, management decisions based on their use will likely be overly conservative. While field and laboratory studies can provide valuable site-specific information on contaminant bioavailability, toxicity and ecological effects, they can be expensive and ineffective if focused too broadly. Ecological risk assessment (ERA) provides a framework for evaluating contaminated sediments, which can incorporate a range of assessment tools in a logical and cost-effective manner.

However, ERAs can also be relatively expensive; the search continues for a cost-effective “silver bullet” which will save time and money (e.g., eliminate having to do site-specific bioeffects testing), while still providing realistic clean-up goals if such are required. SQVs are particularly appealing in this regard because they could be that alternative “if only” one could determine exactly what the proper effects/no-effects threshold values are for all contaminants of potential concern (COPCs). To date this remains beyond the limits of our technical knowledge or abilities, but the search continues. While recognizing that this search might one day be successful, this paper deals with the present role of sediment quality values in ecological risk assessment.

Section snippets

Ecological Risk Assessment (ERA)

Risk assessment of sediments (and other media) consists of three major steps which may be further subdivided in some jurisdictions (US EPA, 1992): problem formulation; analysis (exposure and effects characterization); and, risk characterization. The overall intent of any ERA is to evaluate risk to populations and communities in the field (US EPA, 1997), the overall objective of sediment ERAs is generally to evaluate the risks of various sediment management strategies (e.g., dredge or leave in

Types of SQVs

Numerous types of SQVs have been developed to assist in the assessment of sediment quality (e.g., see US EPA, 1996). While there are substantial differences in derivation procedures (and hence resulting SQVs) among SQV types, no one type is necessarily better than the others for use in ERA, provided of course that such values are within the bounds of reason, e.g., not below accepted background concentrations. SQVs in common usage may be classified as conservative or non-conservative (i.e., they

Major Limitations of SQVs

The previous section touched on some of the inherent limitations of concentration-based SQVs. Understanding these limitations will help to determine how prominent a role SQVs can serve in sediment ERA. Key limitations are summarized as follows:

Degree of conservatism: As discussed above, different SQV derivation procedures have inherently different protection goals. The more conservative SQVs are skewed towards producing more false-positive results (i.e., predicting effects when none are

SQV Usage in ERA

ERA has evolved as a tool to help make sound environmental decisions. It provides a framework within which to conduct site-specific investigations geared towards assessing risks associated with present (i.e., baseline or retrospective ERA) or future (i.e., predictive ERA) conditions. The current popularity of ERA is partly based on its “common sense” approach, which incorporates site-specific information to identify the “real” risks that require managing. Minimizing Type I and II errors in

Example – Dredging

EPA/USACE (1998) detail procedures for the evaluation of dredged material which, although not based on ERA, are consistent with our recommendations above. Specifically, they suggest that SQVs, when ready for use, be applied in Tier II of a four-tier evaluation process. Tier III consists of standardized laboratory bioeffects and bioaccumulation testing; Tier IV consists of case specific evaluations to be used in the eventuality that a decision cannot be made in Tier III. Tier I consists of a

Conclusion

Notwithstanding their limitations, we suggest that SQVs should be used in the problem formulation stage of ERA to identify contaminants of potential concern by comparing sediment concentrations to SQVs in a screening process. Specifically we suggest that bioavailable sediment contaminants which will result in direct toxicity (whatever the exposure pathway, i.e., from water [interstitial or overlying] or food) can probably be predicted, to the extent necessary for hazard identification/problem

Acknowledgements

This paper benefited greatly from discussions and input with colleagues at EVS Environment Consultants. In particular we thank: Michael Johns, Joe Germano, Kathy Godtfredsen. However, the authors bear full responsibility for the opinions expressed in this paper. We also thank David Moore (US Army Corps of Engineers) for inviting one of us (PMC) to give a talk on this subject and thus stimulating us to write this paper.

References (19)

  • Barrick, R., Becker, S., Brown, L., Beller H. and Pastorok, R. (1988) Volume 1. Sediment quality values refinement:...
  • Chapman, P. M., Allard, P. J. and Vigers, G. A. (In Press) Development of sediment quality values for Hong Kong Special...
  • DiToro, D. M., Zarba, C. S., Hansen, D. J., Berry, W. J., Swartz, R. C., Cowan, C. E., Pavlou, S. P., Allen, H. E.,...
  • Environment Canada (1995) Interim sediment quality guidelines. Ecosystem Conservation Directorate, Evaluation and...
  • EPA/USACE (1998) Evaluation of dredged material proposed for discharge in waters of the US-Testing Manual. US...
  • Long, E. R. and MacDonald, D. D. (1998) Recommended uses of empirically-derived, sediment quality guidelines for marine...
  • Long, E. R., MacDonald, D. D., Smith, S. L. and Calder, F. D. (1995) Incidence of adverse biological effects within...
  • Long, E. R., Field, L. J. and MacDonald, D. D. (1998) Predicting toxicity in marine sediments with numerical sediment...
  • MacDonald, D. D., Carr, R. S., Calder, F. D. and Long, E. R. (1996) Development and evaluation of sediment quality...
There are more references available in the full text version of this article.

Cited by (85)

  • Human-induced sediment degradation of Burullus lagoon, Nile Delta, Egypt: Heavy metals pollution status and potential ecological risk

    2022, Marine Pollution Bulletin
    Citation Excerpt :

    Rodrigues et al. (2017) mentioned that the chronic toxicities of sediment-feeding organisms display a positive correlation to contaminated sediments with metals. Moreover, the contaminated sediment act as a potential source for the dissolved and particle-bound contaminants to overlying waters (Chapman and Mann, 1999; Eggleton and Thomas, 2004; Li and Cai, 2015). Accordingly, the metals may bioaccumulate in fish and shellfish tissues, causing harmful effects to consumers (e.g., pancreatic cancer cases in the northeast Nile delta region related to water pollution (Soliman et al., 2006)).

View all citing articles on Scopus
View full text