Ecotoxicology, bioavailability

As seen further on in this chapter, individual PEEP index values express a condensed portrait of an effluent s hazard potential which takes into account several important ecotoxicological notions (toxic intensity and scope in terms of biotic levels impacted, bioavailability, persistence of toxicity and effluent flow). Unlike wastewater investigations limited to chemical characterization, this bioassay-based scale reflects the integrated responses of several representative toxicity tests to all interaction phenomena (antagonistic, additive and/or synergistic effects) that can be present in effluent samples. 

Brezonik, P.L., King, S.O. and Mach, C.E. (1991) The influence of water chemistry on trace metal bioavailability and toxicity to aquatic organisms. In Metal Ecotoxicology. Concepts and Applications (eds Newman, M.C. and McIntosh, A.W.). Lewis Publications, Chelsea, MI, pp. 1-31. 

Chapman P.M., Wang F.Y., Janssen C., Persoone G., Allen H.E. (1998) Ecotoxicology of metals in aquatic sediments binding and release, bioavailability, risk assessment, and remediation. Canadian Journal of Fisheries and Aquatic Sciences 55(10) 2221-2243. 

A decision whether or not the substance be classified will be made by comparing aquatic toxicity data and solubility data. If the L(E)Cso is exceeded, irrespective of whether the toxicity and dissolution data are at the same pH and if this is the only data available then the substance should be classified. If other solubility data are available to show that the dissolution concentration would not exceed the L(E)C5o across the entire pH range then the substance should not be classified on its soluble form. This may involve the use of additional data either from ecotoxicological testing or from applicable bioavailability-effect models. 

Gochfeld M (2003) Gases of mercury exposure, bioavailability, and absorption. Ecotoxicology and Environmental Safety 56 174-179. 

Rudel H (2003) Case study Bioavailability of tin and tin compounds. Ecotoxicology and Environmental Safety 56(1) 180-189. 

Successful implementation of a Triad approach is dependent on the availability of a suitable set of instruments chemical, toxicological (bioassays) and ecological. Without doubt, substance-oriented approaches have received a lot of attention in ecotoxicology and the available techniques are relatively mature (Posthuma et al., 2002). The current focus in this field of research is on improvement of bioavailability considerations, the effect of mixtures and the indirect effects of substances. 

A preponderance of toxicity data reported to date was generated in studies using artificial soil (similarly formulated Organization for Economic Cooperation and Development [OECD] artificial soil or U.S. Environmental Protection Agency [USEPA] standard artificial soil). These investigations did not consider the effects of soil physical and chemical properties, which can vary widely at contaminated sites, on the bioavailability and subsequent toxicity of EM. Ecotoxicological data established in such studies may have limited relevance for site-specific ERAs. Therefore,... 

The ecotoxicological data reviewed in this section show that TNT contamination of soil can disrupt the ecological functioning of a soil system and inhibit natural attenuation processes. This occurs because TNT can destroy a portion of the soil microbial community involved in OM decomposition and reduces the amount of soil Corg produced by this community. Consequently, the amount of bioavailable TNT is relatively high and it interferes with colonization of impacted areas by plants, resulting in toxicity of TNT to soil invertebrates and adversely affecting site remediation and... 

Direct toxicity assessment (DTA) can also be used to account for the combined effects of contaminants. Measurements taken from biological and ecotoxicological tests are more directly related to ecological risk, because they measure the biological effects from a mixture of contaminants and, in doing so, provide an implicit indication of the bioavailability of the contaminants. Some tests can be simple and cost-effective in comparison to screening for multiple chemical... 

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