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Publications
Supervising Scientist, Darwin, 2005
ISBN 0 642 24395 6
ISSN 0 158-4030
A conceptual model of contaminant pathways from the operational phase of Ranger uranium mine is being developed to address one of the ARRTC Key Knowledge Needs. The early development of the model was reported on in the 2003–04 Supervising Scientist Annual Report. The primary purpose of the conceptual model will be to place the off-site contaminant issues at Ranger in a risk management context. Moreover, the final product, as well as being used for formal risk assessment, will serve as a communication tool for both scientists and Traditional Owners. The summary below focuses on progress towards the finalisation of the technical content of the model and an overview of the proposed involvement of, and communication with, Traditional Owners to complete the model.
To date, the development of the conceptual model has involved an internal and external technical expert panel approach to identify, and agree on, the relevant details within the following model elements:
and then for each stressor, its
Details within each of these elements have been compiled and constructed diagrammatically, as shown in Figure 3.13. For each stressor transport pathway sub-model, the relevant linkages have been made that indicate how a stressor leaves the mine site, where in the environment it is distributed, what biota (including humans) could be exposed and affected, and what monitoring is in place, or needs to be in place, to detect effects.
As an example, the sub-model for inorganic toxicant transport via one of several specific surface water transport mechanisms is shown in Figure 3.14. Amongst other pathways, inorganic toxicants can be transported off the mine site by surface water runoff and/or direct mine water discharges/overflows, and enter the nearby creeks. Depending on the nature of the toxicant, once in the creek it can partition into, and move between, various environmental compartments, most notably the water column, the sediment or the resident aquatic biota. Various biotic groups will be potentially exposed to the toxicant in these environmental compartments. For example, phytoplankton exposed directly from the water column, fish exposed directly from both the water column and from consuming prey that have taken up and accumulated the toxicant, and benthic macroinvertebrates exposed directly from the sediment. In addition, people and other terrestrial animals can consume aquatic organisms that have taken up and accumulated the toxicant. However, the extent to which the various exposure pathways are relevant and important in terms of resulting in adverse effects on receptor organisms depends on many biotic and abiotic factors (eg relative contribution of the pathway to the total exposure of the receptor organism, sensitivity/tolerance of the receptor organism to the contaminant, environmental conditions that influence the bioavailability of the contaminant). To ensure that the Supervising Scientist can meet its primary objective of ensuring the protection of the people and the environment of the Alligator Rivers Region from the effects of uranium mining (termed as assessment endpoints in the conceptual model), various physico-chemical and biological indicators or measurement endpoints are assessed and monitored, as surrogates of the assessment endpoints. As can be seen in Figure 3.14, the model indicates the relationship between the receptor organisms and the assessment endpoints (SSD objectives) and measurement endpoints (SSD monitoring and assessment programs).
Other than risk assessment, one of the key functions of the conceptual model will be as a communication tool for outlining the types, pathways and relative risks of contaminants from Ranger. Suitability of the conceptual model as a communication tool for Traditional Owners will be assessed through incorporating their views and input through a workshop facilitated by the Aboriginal Liaison Officer. Following the workshop, an iterative process of consultation will be undertaken to ensure their input is correctly presented. It is anticipated that the final communication product for Traditional Owners will be presented in DVD format.
When complete, the conceptual model will represent an iteration of previous models, having incorporated new knowledge and understanding of the relevant processes and issues. It will provide the framework for a quantitative comparison of risks and uncertainties for all stressor transport pathway sub-models. It will also enable historical and current activities and priorities to be evaluated, and future priorities to be determined. Further, it will act as a knowledge and communication management tool, within a risk management framework that links clearly to the ongoing management of mining operations.
Figure 3.13 Basic elements of a contaminant pathways conceptual model for Ranger uranium mine
Figure 3.14 Conceptual model for transport of inorganic toxicants from Ranger uranium mine via a direct surface water to surface water pathway