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Sediment Quality Assessment and Management: Insight and Progress Edited by M. Munawar© 2003 Ecovision World Monograph Series Aquatic Ecosystem Health & Management Society A tiered, weight-of-evidence approach for evaluating aquatic ecosystems G.A. Burton, Jr., C.D. Rowland, M.S. Greenberg, D.R. Lavoie, J.F. Nordstrom, L.M. Eggert Institute for Environmental Quality,Wright State University Dayton, OH 45435,U.S.A. Keywords: water quality monitoring, sediment quality management, stormwater runoff, freshwater, groundwater Introduction The traditional methods of assessing water and sediment quality have successfully identified polluted areas for decades. These approaches have been an essential component of regulatory programs that have resulted in improved water quality (USEPA, 1993). These methods include: physicochemical characterizations with comparisons to water quality criteria, benthic macroinvertebrate and fish community analyses, and laboratory toxicity testing of effluents, ambient waters, and sediments (Grothe et al., 1996). However, there continues to be controversy surrounding the accuracy and usefulness of these traditional assessment methods, as evidenced by challenges to the applicability of water quality standards and the relationship of whole effluent toxicity to receiving water quality (Burton, 1999b; Grothe et al., 1996); and failure to adopt sediment toxicity test methods and biocriteria by most environmental regulatory agencies. Some of these concern are justified, as results of these assessments have occasionally resulted in false positives (predicting adverse effects when they do not exist) or false negatives (predicting no impacts when they do exist). These confounding results are not surprising, given that every assessment approach has unique strengths and limitations and assumptions (Table 1), exposures often differ between laboratory and field, chronic effects are difficult to assess, all lines of evidence do not necessarily need to agree and ecosystems (and their characterizations) are complex. 4 Since the promotion of the “Sediment Quality Triad” by Chapman (1986), there has been the recognition that “multiple lines-of-evidence” type of approaches were not only useful, but obligatory at most sites in order to determine whether significant sediment contamination exists. Numerous studies have used variations of the “triad” approach, looking at laboratory toxicity, indigenous community structure and sediment chemistry. Other components that have been recommended, and not as readily included, are histopathology, subcellular biomarkers, habitat and grain size, tissue residues, bacterial assays, and in situ toxicity (e.g., Bombardier and Bermingham, 1999; Burton, 1999b; Burton and Stemmer, 1988; Chapman et al., 1992; Maxon et al., 1997; Porebski et al., 1999). In addition, reasonable strategies for assessing sediment contamination in a tiered manner have been recommended (Adams et al., 1992; Burton, 1999b; Chapman and Mann, 1999; Chapman et al., 1999a, 1999b; Krantzberg et al., 2000; Porebski et al., 1999) where sediment quality guidelines are used as screens and biological effects are verified with laboratory toxicity testing and investigations of indigenous community impacts. The science of ecotoxicology has advanced significantly during the past two decades, while the methods used by most regulatory agencies (e.g., water quality criteria, community indices, laboratory toxicity testing) have changed little. These agencies have, however, readily adopted new standard methods for chemical analyses, allowing for detection of priority compounds at the sub-nanogram per liter level in many cases. This has resulted in the increased detection of contamination in waters, sediments and tissues; yet the ecological significance of low level exposures is largely unknown. Ecotoxicologists have documented the importance of characterizing both natural and anthropogenic stressors and their exposures at Table 1. Strengths and Limitations of Traditional Assessment methods. 5 multiple levels of the food web. In addition, they have shown that chemical-specific criteria do not always provide predictive power when multiple contaminants and stressors are present, particularly at chronic exposure levels (Baird and Burton, 2001). Given these realities, it is apparent that more effective ecological assessment methods are needed to document exposure (e.g., use of subcellular biomarkers), characterize the magnitude, frequency and duration of exposure, and, most importantly, define when significant adverse ecological effects occur (Baird and Burton, 2001). These issues cannot be answered accurately without the addition of novel assessment approaches, in addition to those currently being used, by the regulatory agencies. One approach that improves the assessment of exposure is that of in situ testing, removing the laboratory-related artifacts (Burton et al., 1996; Burton, 1999b). In situ testing using caged organisms has been increasing around the world for the past several years (e.g., Chappie and Burton, 2000). Exposure accuracy is improved (as compared to the laboratory) allowing for natural fluctuations and interactions of suspended solids, light, temperature...


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