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Barium and High Explosives in a Semiarid Alluvial System, Cañon de Valle, New Mexico

^a TerranearPMC, 1911 Central Ave., Los Alamos, NM 87544
^b Environmental Geology and Spatial Analysis Group, MS-D452, Los Alamos National Laboratory, Los Alamos, NM 87545
^c Atmospheric Climate and Environmental Dynamics Group, MS-J495, Los Alamos National Laboratory, Los Alamos, NM 87545
^d Hydrology, Geochemistry, and Geology Group, MS-D462, Los Alamos National Laboratory, Los Alamos, NM 87545

View larger version (66K): [in a new window]   Fig. 1. Location of the study area within LANL, New Mexico, and the locations of the TA-16-260 outfall, stream monitoring stations, alluvial wells, and springs in Cañon de Valle.

View larger version (137K): [in a new window]   Fig. 2. Cañon de Valle main channel looking downstream. Channel is approximately 0.5 m wide. Photograph was taken in June 2000 following a 16-mm rainstorm.

View larger version (25K): [in a new window]   Fig. 3. (A) RDX and (B) Ba concentration results for the four alluvial groundwater wells from 1998 to 2002.

View larger version (16K): [in a new window]   Fig. 4. (A) RDX and (B) Ba concentrations as a function of water height in alluvial well, AW-4, 1998 to 2002.

View larger version (25K): [in a new window]   Fig. 5. Concentrations of RDX in surface water, alluvial groundwater, and spring water during high flow (A, 27 Mar. 2001) and low flow (B, 18 Sept. 1998) conditions.

View larger version (25K): [in a new window]   Fig. 6. Concentrations of Ba in surface water, alluvial groundwater, and spring water during high flow (A, 27 Mar. 2001) and low flow (B, 18 Sept. 1998) conditions.

View larger version (35K): [in a new window]   Fig. 7. Alluvial groundwater and surface water average (A) RDX and (B) Ba concentrations for the study reaches from 1998 to 2002.

View larger version (31K): [in a new window]   Fig. 8. Concentrations of (A) RDX and (B) Ba in sediment. Samples were collected in 1996, 1999, and 2002.

View larger version (24K): [in a new window]   Fig. 9. Average inventories in canyon sediments of (A) RDX and (B) Ba, normalized by reach length to units of kilograms per kilometer.

View larger version (165K): [in a new window]   Fig. 10. Scanning electron micrographs: (A) back-scattered electron image of witherite showing dissolution textures; (B) secondary electron image showing a dissolution rim surrounding the relic core of a witherite grain; (C) close-up secondary electron image of a barite precipitation rim on quartz grain; and (D) back-scattered electron image of barite precipitation rim.

View larger version (39K): [in a new window]   Fig. 11. (A) During wet conditions, such as spring snowmelt or prolonged precipitation events, residual RDX is flushed through the vadose zone and alluvial system. RDX is stored in fine-grained sediments in the canyon bottom and in the tuff matrix, surge beds, and fractures. More flow paths are active during wet periods, and some of these flow paths may bypass the alluvial groundwater and enter the stream channel directly. Barite will remain insoluble while witherite can dissolve following influx of fresh water. (B) Under dry conditions RDX is isolated in unsaturated fine-grained sediments and the vadose zone. As the alluvium dries, witherite and barite precipitate.