I n f i l t r a t i o n of brine i n t o the McMurdo Ice Shelf i s dominated by wave-like intrusions of sea-water triggered by periodic break-outs of the ice f r o n t . Observations of a brine step 4.4 m i n height in the McMurdo Ice Shelf show that i t has migrated about 1.2 km i n four years. The present brine wave i s overr i d i n g an older brine-soaked layer. This migration i s proof of the dynamic nature of the step, which is the leading edge of a brine wave that originated at the ice f r o n t a f t e r a major break-out of the McMurdo Ice Shelf. The inland boundary of brine penetration i s characterized by a series of descending steps that are believed to represent terminal positions of separate intrusions of brine of s i m i l a r o r i g i n . The inland boundary of brine percolation i s probably cont r o l l e d largely by the depth at which brine encounters the f i r n / i c e t r a n s i t i o n (43 m). However, t h i s boundary is not f i x e d by permeability considerations alone, since measurable movement of brine i s s t i l l occurring at the inland boundary. Freeze-fractionation of the sea-water as i t migrates through the ice shelf precipitates v i r t u a l l y a l l sodium s u l f a t e , and p r e f e r e n t i a l l y concomitant removal of water by freezing i n the pore spaces of the i n f i l t r a t e d f i m produces residual brines approximately seven times more concentrated than the o r i g i n a l sea-water.

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The goal of the DARPA "Dog's Nose" program is to develop a sensor capable of detecting explosives contained in all buried landmines. In support of the DARPA program, the purpose of the Explosives Fate and Transport (EF&T) experiments is to define in detail the accessible trace chemical signature produced by the explosives contained in buried landmines. We intend to determine the partitioning (soil, air, water), composition, and quantity of explosive related chemicals (ERC) which emanate from different kinds of landmines (predominantly plastic-cased with TNT as the main charge) buried in multiple soil types and exposed to various climatic events. We are also developing a computer model that will enable us to predict the composition and quantity of ERC under a much wider range of environmental conditions than we are able to test experimentally.In our systematic quest to define the signature of a buried mine we have divided our efforts into the following categories:1 . Chemical analysis of the main explosive charge from several sources of TNT and the equilibrium vapor associated with TNT from these sources. 2. The amount and composition of ERC that are found on the exterior of landmines. 3. Determination of the rate at which ERC permeate the casing materials of both plastic and metallic landmines. 4. The effect that different soils have on the transport and fate of ERC as they move through the soil/pore matrix to the surface.5. The effect of environmental factors on ERC, i.e., climate, time since burial, depth of burial, soil properties, sunlight, near surface air movement, and vegetation.

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