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When crude oil or petroleum products are released to the marine environment, immediate alterations in chemical and physical properties occur as a result of a variety of weathering processes. A three-year oil weathering study of Prudhoe Bay crude oil has been completed under ambient subarctic conditions at the National Oceanic and Atmospheric Administration's lower Cook Inlet field laboratory in Kasitsna Bay, Alaska. Quantitative data from outdoor wave-tank and flow-through aquaria systems were collected on seasonal and time-series measurements of compositional changes in the oil and water column due to evaporation, dissolution, and water-in-oil emulsification, as well as alterations in rheological properties of the slick. These data are used for mathematical model development and verification of computer-predicted oil weathering behavior from a variety of spill scenarios. The oil-weathering mathematical models developed in this program are based on measured physical properties data, and they generate material balances for both specific compounds and pseudo-compounds (distillation cuts) in crude oil. These models are applicable to open-ocean oil spills, spills in estuaries and lagoons where the water column is finite, and spills on land. The oil weathering processes included in the mathematical model are evaporation, dispersion of oil into the water column, dissolution, water-in-oil emulsification (mousse formation), and oil slick spreading. In most cases, very good agreement is obtained between predicted and observed weathering behavior. The material balance and weathered-oil composition predictions generated as a function of time have been very useful in providing information for contingency planning, estimating potential damage assessments and preparing environmental impact reports for outer continental shelf drilling activities.

Outdoor flow-through seawater wave tank studies and model predictions on the chemical and physical fate of Prudhoe Bay crude oil in subarctic waters are compared with field observations from the Exxon Valdez oil spill in Prince William Sound, Alaska. Excellent agreement is obtained between predicted and observed parameters, including evaporative loss of lighter distillate cuts, water content in mousse, density, viscosity, oil/water and oil/air interfacial surface tension, and chemical composition. As predicted from wave tank studies, water column samples of dispersed and dissolved oil and suspended particulate material collected from several heavily oiled sheltered coves and bays in Prince William Sound indicate that little oil reached the near-shore benthic environment during the first few weeks after the spill.

The policy of the United States is to dispose of high-level nuclear waste underground in geologic repositories. The U.S. Department of Energy (DOE) has been developing plans for a repository to be located at Yucca Mountain, Nevada, and intends to submit a license application to the U. S. Nuclear Regulatory Commission (NRC) for that repository in June 2008.This paper discusses DOE's bases for and approach to modeling the localized and general corrosion aspects of the Alloy 22 outer shell of the container that DOE plans to use for encapsulating the waste in the repository. The modeling is necessary to predict the corrosion behavior for the container's extraordinarily long "service period" -more than a million years.

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