Modeling long-term risk to environmental and human systems at the Hanford Nuclear Reservation: scope and findings from the initial model.

The Groundwater Protection Project at the US Department of Energy Hanford Site in Washington State is currently developing the means to assess the cumulative impact to human and ecological health and the regional economy and cultures from radioactive and chemical waste that will remain at the Hanford Site after the site closes. This integrated system is known as the System Assessment Capability (SAC). The SAC Risk/Impact Module discussed in the article uses media- and time-specific concentrations of contaminants estimated by the transport models of the integrated system to project potential impacts on the ecology of the Columbia River corridor, the health of persons who might live in or use the corridor or the upland Hanford environment, the local economy, and cultural resources. Preliminary Monte Carlo realizations from the SAC modeling system demonstrate the feasibility of large-scale uncertainty analysis of the complex relationships in the environmental transport of contaminants on the one hand and ecological, human, cultural, and economic risk on the other. Initial impact results show very small long-term risks for the 10 radionuclides and chemicals evaluated. The analysis also helps determine science priorities to reduce uncertainty and suggests what actions matter to reduce risks.

METAL REGULATION AND MOLTING IN THE BLUE CRAB, CALLINECTES SAPIDUS: METALLOTHIONEIN FUNCTION IN METAL METABOLISM.

We recently demonstrated that zinc, copper, and hemocyanin metabolism in the blue crab varies as a function of the molt cycle. To extend these observations, and better delineate metal metabolism in marine crustaceans, we have conducted experiments to determine if environmental temperature and season of the year affect concentrations of hemocyanin and copper in the hemolymph and copper and zinc in the digestive gland. Overwintering, cold water crabs (6°C) had decreased hemocyanin and copper in the hemolymph and normal zinc and copper in the digestive gland with respect to summer crabs collected at 20-30°C. When these crabs were warmed to 20°C and fed fish for three weeks, they showed increases in the concentrations of copper in the digestive gland, and copper and hemocyanin in the hemolymph. In addition, a change from a zinc to a copper-dominated metallothionein was found in a majority of the warmed crabs, suggesting the involvement of copper metallothionein in the resynthesis of hemocyanin. Based on these observations and previous data (Engel, 1987) a conceptual model of copper and zinc partitioning in the blue crab has been constructed. In this model, metallothionein has an important role in metal regulation both during molting and in the changes related to season of the year. Metallothionein-bound copper and zinc appear to be regulated at the cellular level for the synthesis of metalloproteins, such as hemocyanin (copper) and carbonic anhydrase (zinc), both of which are necessary for normal growth and survival. Finally, we present evidence showing that copper metallothionein can directly transfer its metal to the active site of apohemocyanin. Copper insertion seems to precede the formation of viable oxygen binding sites.