HR: 0830h
AN: H41D-1033    [PDF]
TI: Barium and High Explosives in a Semiarid Alluvial System, Ca\~{n}on de Valle, New Mexico.
AU: * Reid, K D
EM: kreid@pmctecnologies.com
AF: Shaw Environmental \& Infrastructure, 335 Central Park Square, Los Alamos, NM 87544 United States
AU: Hickmott, D D
EM: dhickmott@lanl.gov
AF: Hydrology, Geochemistry, \& Geology Group, MS-D462 Los Alamos National Laboratory, Los Alamos, NM 87545
AU: Reneau, S L
EM: sreneua@lanl.gov
AF: Environmental Geology \& Risk Analysis Group, MS-D462 Los Alamos National Laboratory, Los Alamos, NM 87545
AU: Newman, B D
EM: bnewman@lanl.gov
AF: Atmospheric Climate \& Environmental Dynamics Group, MS-J495 Los Alamos National Laboratory, Los Alamos, NM 87545
AU: Gram, P E
AF: PMC Technologies, 2237 Trinity Bldg #2, Los Alamos, NM 87544
AU: Heikoop, J M
AF: Hydrology, Geochemistry, \& Geology Group, MS-D462 Los Alamos National Laboratory, Los Alamos, NM 87545
AU: Alcon, E D
AF: Shaw Environmental \& Infrastructure, 335 Central Park Square, Los Alamos, NM 87544 United States
AU: Herrell, K A
AF: Shaw Environmental \& Infrastructure, 335 Central Park Square, Los Alamos, NM 87544 United States
AU: Jercinovic, D E
AF: Shaw Environmental \& Infrastructure, 335 Central Park Square, Los Alamos, NM 87544 United States
AU: Lawler, D S
AF: Shaw Environmental \& Infrastructure, 335 Central Park Square, Los Alamos, NM 87544 United States
AU: Pietz, J M
AF: Shaw Environmental \& Infrastructure, 335 Central Park Square, Los Alamos, NM 87544 United States
AB: Barium and RDX (a military high explosive compound) were evaluated from 1998 to 2002 within a semiarid alluvial system, Ca\~{n}on de Valle (CdV), New Mexico. A high explosive (HE) machining facility discharged effluent containing these analytes to the canyon from 1951 to 1996. Surface water, alluvial groundwater, active channel sediments, and floodplain sediments were characterized along a 2 km long reach of canyon. Barium concentrations were higher in the alluvial groundwater than the surface water with the highest concentration centered approximately 500 m downgradient from the HE facility. Of the 21,000 kg of Ba estimated to be in CdV sediment in 1999, about 65% is estimated to have been contained in fine-grained floodplain deposits, 10% in the active channel, and 25% in coarse-grained deposits below the floodplains. The ratio of Ba concentration in fine grained deposits to the active channel increases downstream and increased over time. These data indicate that Ba from the effluent was first stored in the active channel where it could preferentially bind to fine sediment particles, and then was redistributed onto floodplains following scour and suspension during floods. The Ba residing within the floodplain sediments appears relatively stable, and remains isolated from surface water and alluvial groundwater. Approximately 5 kg of RDX was estimated to reside in CdV sediment, also preferentially in fine-grained sediment. RDX concentrations in groundwater were highest (up to 759 ug/L) during high flow snowmelt runoff. The highest average RDX concentration was from an alluvial well approximately 1000 m down gradient. There was a positive correlation between saturated thickness in CdV alluvial wells and RDX concentration. The strong correlation between RDX concentration and saturated thickness suggests that RDX resides in the vadose zone and mobilizes during wet periods when the effective saturated area increases. RDX and Ba show markedly different transport pathways through the alluvial system. Barium is readily sorbed and transported with the sediment fraction. In contrast, RDX is unbuffered and conservative. Thus as the alluvial system wets up, the RDX mobilizes. Knowledge of the distribution of Ba and RDX is critical to design and implementation of corrective measures for this system.
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
DE: 1871 Surface water quality
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting