The Australian and New Zealand Environment and Conservation Council (ANZECC) and the Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) have announced that the 1997 review of the Australian Water Quality Guidelines will include for the first time, consideration of sediment quality guidelines. For this reason, it is timely to review the methods for establishing such guidelines, and the manner in which they could be used in managing the quality of sediments in Australian rivers, lakes and drainage systems. In this thesis, the problem of the development of sediment quality guidelines is introduced and basic questions relating to the development of such guidelines are addressed. The importance of sediment monitoring and sediment quality assessment in aquatic ecosystem management is demonstrated, and the role of sediment quality guidelines in the process of sediment quality assessment is discussed. The arguments considered in this thesis are illustrated by specific reference to the setting and use of sediment quality guidelines for heavy metal contamination. A number of physico-chemical factors (grain size distribution, pH, redox potential, alkalinity and hardness, salinity, organic matter) can affect the bioavailability and toxicity of contaminants in sediments, and these factors may vary spatially and temporally within and between sediment deposits. Changes in physico-chemical conditions as a result of natural or anthropogenic processes may lead to major changes in bioavailability of sediment contaminants. The variability of these physico-chemical factors has ramifications for the way in which sediment quality guidelines are derived and used. Factors affecting the way in which toxicity is measured (test species chosen, toxicological end-point measured, duration of test relative to life-cycle), and toxicity data is interpreted, are also important to the development of useful sediment quality guidelines. All of these factors must be taken into account in deriving sediment quality guidelines for Australian conditions. The large number of factors affecting the sensitivity and efficiency of sediment quality guidelines means that a simple set of numerical guidelines, as has been used in the past, is not appropriate. A multi-step assessment procedure will be required. Methods of setting sediment quality guidelines that have been used by authorities in overseas jurisdictions were reviewed. Advantages and disadvantages of the various methods were compared. None of the methods used overseas has been shown to be applicable to Australian conditions. In the absence of a suitable method for deriving Australian sediment quality guidelines in the short term, the adoption of the Canadian Interim Sediment Quality Guidelines as interim sediment quality guidelines for Australia is recommended. Sediment quality guidelines need to be viewed in the context of the overall environmental management process, of which they form an integral part. The policy background to environmental management in Australia, and the management frameworks that have been put in place to implement the policy, are outlined. The AS/NZS/ISO 14000 series of standards for environmental management systems provides a framework which is consistent with the principles and objectives of environmental management in Australia. It therefore provides an appropriate framework within which to develop and use sediment quality guidelines. Within the broad AS/NZS/ISO 14000 policy, a framework for the development and use of sediment quality guidelines is proposed, which will provide a technically and legally defensible basis for the management of aquatic sediments in Australia, in the short term and long term. The proposed framework involves the setting of Interim Sediment Quality Guidelines for Australia, based on the best scientific knowledge currently available. The framework recognises that the factors affecting the bioavailability and toxicity of sediment contaminants are complex, and that the current level of knowledge of sediment processes is incomplete. Therefore, a conservative approach to setting guidelines is taken, and a highly sensitive guideline based on that used in Canada, is proposed. The framework further recognises that this approach will lead to over protection of the environment in some cases, so a “Decision Tree” approach is taken. The “decision tree” allows the consideration of more complex interactions than can be incorporated into simple numeric guidelines, while attempting to simplify the assessment process. In keeping with the ISO 14000 series of standards for environmental management, the framework also explicitly includes steps designed to ensure that monitoring data are regularly collated, and analysed, and where necessary, guidelines are able to be updated in light of new knowledge gleaned from the review process. The proposed framework is appropriate to, and supportive of, the principles of environmental management as set out in Australian Government policy documents, inter-governmental and international agreements, and legislation. It provides a basis for the on-going collection of data suited to increasing our understanding of the factors influencing the behaviour of contaminants in sediments, and thereby lead to continual improvement in sediment quality guidelines for use in Australian conditions.
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