Risk assessment contaminated sediments

In Figure 6-1 (from Ahlf Munawar, 1988, after Calamari et al., 1979) the proposed strategy for risk assessment of sediment-associated pollutants is shown. The solid lines indicate the direction of increasing difficulty and specificity of each level. The dotted lines show that at each level, a risk assessment is possible when the results of the test represents either a toxic or hazardous bioconcentration of contaminants. Different types of biological tests have been applied on polluted sediments, either on liquid-phase or water-column effect, and those concerned with effects of solid-bound contaminants, which are ingested by aquatic organisms ... 

The sustainable management of sediments, in addition to water, soil and sludge environmental matrices, in relation to surfactant regulations, is also an important and relevant issue. The US EPA has recently shown concern regarding the levels of surfactants in sediments and has thus released a Draft Contaminated Sediment Science Plan. In this draft, recommendations for the development of analytical methods and evaluations of the toxicity and risk assessment of Emerging endocrine disrupters like APEOs and their metabolites in sediment samples are outlined. 

The bio availability of organic compounds in soils/sediments to microbes, plants, and animals is important from the perspective of remediation and risk assessment. Cleanup technology (ex situ or in situ) of contaminated soils and bottom sediments requires mass transport of contaminants through the solid materials, which in turn depends on sorption/desorption kinetics. 

Generally, slow sorption or desorption has made complete remediation technology difficult. However, there have recently been legitimate questions raised by some researchers [163,187] about whether we even need to be concerned about residues that desorb so slowly and thus are apparently largely bio-unavailable. At a minimum, it is important that we understand the factors which govern slow sorption/desorption rates, their kinetics and causes at the intra-particle level of different solid phase materials (e.g., surface/subsurface and aquatic sediment particles), and how these phenomena can relate to contaminant transport, bioavailability, toxicity, remediation, and risk assessment modeling. 

Van Beelen, P. Doehnann, P. Significance and apphcation of microbial toxicity tests in assessing ecotoxicological risks of contaminants in soil and sediment. Chemosphere 1997, 34, 455-499. 

Ecological Risk Assessment of Contaminated Sediments. Pacific Grove, California, 23 to 28 Apr 1995. Published by SETAC, 1997. 

This thesis focuses on the applicability of in vitro, in vivo bioassays and bioindicators as tools for evaluating the effects of complex chemical mixtures in the process of deciding whether dredged harbour sediments can be disposed of at sea without serious adverse effects on marine ecosystem and human health. It considers the North Sea delta area in order to determine a comprehensive approach for the application of both in vitro and in vivo bioassays for hazard assessment, advanced risk assessment, and location-specific ecological impact assessment for dredged harbour sediments. To aid in the selection of appropriate, robust and reliable in vitro and in vivo bioassay and bioindication methods for these specific purposes, the uneertainty, predictability and specificity of the bioassays have been explored and the applieability in eombination with other analyses is discussed. The focus of the chosen examples is on bioassays and bioindicators for the relatively well studied dioxin-like contaminants and TBT. 

The last section deals with several organic contaminants. The first chapter is an analysis of the behavior of surfactants in the context of a comprehensive risk-assessment analysis. The next two chapters examine the fate of PCBs, as influenced by algal uptake in the water column, volatilization, and weathering in sediments. 

This last equation forms the basis for the EPA s sediment quality guidelines that are used to assess the potential toxicity of contaminated sediments. The idea is to simply measure Cs and foe, look up K0w in a table, compute the predicted Cw, and compare this result to established water quality criteria for the protection of aquatic life or human life (e.g., carcinogenicity risk factors). The use of this simple equilibrium partitioning expression for this purpose is currently the subject of much debate among scientists as well as policy makers. 

The ecological risk to local benthic organisms from potential exposure to POPs through direct contact with marine sediment was also assessed. Direct contact with the contaminated sediment was the most significant pathway of exposure for benthic organisms. The use of chemical specific... 

Deniseger, J. and Kwong, Y.T.J. (1996) Risk Assessment of Copper-Contaminated Sediments in the Tsolum River Near Courtenay, British Columbia, Water Quality Research Journal of Canada 31 (4), 725-740. 

Pastorok, R.A., Peek, D.C., Sampson, J.R. and Jacobson, M.A. (1994) Ecological risk assessment for river sediments contaminated by creosote, Environmental Toxicology and Chemistry 13 (12), 1929-1941. 

The Sediment Quality Triad (SQT) is an effects-based conceptual approach that can be used to assess and determine the status of contaminated sediments based on biology (laboratory and/or in situ toxicity tests), chemistry (chemical identification and quantification), and ecology (community structure and/or function). It provides a means for comparing three different lines of evidence (LOE) and arriving at a weight of evidence (WOE) determination regarding the risk posed by contaminated sediments. Effectively, each LOE comprises an independent assessment of hazard combined and integrated, they provide an assessment of risk. 

Burton, G.A. Jr., Batley, G.E., Chapman, P.M., Forbes, V.E., Smith, E.P., Reynoldson, T., Schlekat, C., den Besten, P.J., Bailer, A.J., Green, A.S. and Dwyer, R.L. (2002b) A weight-of-evidence framework for assessing sediment (or other) contamination improving certainty in the decision-making process, Human and Ecological Risk Assessment 8, 1675-1696. 

Reynoldson, T.B., Smith, E. and Bailer, A.J. (2002a) Comparison of three weight of evidence approaches for integrating sediment contamination data within and across lines of evidence, Human and Ecological Risk Assessment 8, 1613-1624. 

Suter, G.W. III. (1997) Overview of the ecological risk assessment framework, in C.G. Ingersoll, T. Dillon and G.R. Biddinger (eds.), Ecological Risk Assessment of Contaminated Sediments, SETAC Press, Pensacola, FL, USA, pp. 1-6. 

Sahuquillo, A., Rigol, A. and Rauret, G. (2003) Overview of the use of leaching/extraction tests for risk assessment of trace metals in contaminated soils and sediments, Trends in Analytical Chemistry 22,... 

Recently, metapopulation models have been successfully applied to assess the risks of contaminants to aquatic populations. A metapopulation model to extrapolate responses of the aquatic isopod Asellus aquaticus as observed in insecticide-stressed mesocosms to assess its recovery potential in drainage ditches, streams, and ponds is provided by van den Brink et al. (2007). They estimated realistic pyrethroid concentrations in these different types of aquatic ecosystems by means of exposure models used in the European legislation procedure for pesticides. It appeared that the rate of recovery of Asellus in pyrethroid-stressed drainage ditches was faster in the field than in the isolated mesocosms. However, the rate of recovery in drainage ditches was calculated to be lower than that in streams and ponds (van den Brink et al. 2007). In another study, the effects of flounder foraging behavior and habitat preferences on exposure to polychlorinated biphenyls in sediments were assessed by Linkov et al. (2002) using a tractable individual-based metapopulation model. In this study, the use of a spatially and temporally explicit model reduced the estimate of risk by an order of magnitude as compared with a nonspatial model (Linkov et al. 2002). 

Ankley GT, Mount DR. 1996. Retrospective analysis of the ecological risk of contaminant mixtures in aquatic sediments. Human Ecol Risk Assess 2 434-440. 

Clements WH. 1997. Ecological significance of endpoints used to assess sediment quality. In Ingersoll CG, Dillon T, Biddinger GR, editors. Ecological risk assessments of contaminated sediments. Pensacola (FL) SETAC Press, p 123-134. 

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