An improved method for field extraction and laboratory analysis of large, intact soil cores
J.A. Tindall, K. Hemmen, J.F. Dowd
1992, Journal of Environmental Quality (21) 259-263
Various methods have been proposed for the extraction of large, undisturbed soil cores and for subsequent analysis of fluid movement within the cores. The major problems associated with these methods are expense, cumbersome field extraction, and inadequate simulation of unsaturated flow conditions. A field and laboratory procedure is presented that...
Pesticide residues in ground water of the San Joaquin Valley, California
Joseph L. Domagalski, N. M. Dubrovsky
1992, Journal of Hydrology (130) 299-338
A regional assessment of non-point-source contamination of pesticide residues in ground water was made of the San Joaquin Valley, an intensively farmed and irrigated structural trough in central California. About 10% of the total pesticide use in the USA is in the San Joaquin Valley. Pesticides detected include atrazine,...
A systematic approach to modelling the dynamic linkage of climate, physical catchment descriptors and hydrologic response components
A.J. Jakeman, G.M. Hornberger, I.G. Littlewood, P.G. Whitehead, J. W. Harvey, K.E. Bencala
1992, Mathematics and Computers in Simulation (33) 359-366
No abstract available....
Modeling transport in transient ground-water flow: An unacknowledged approximation
Daniel J. Goode
1992, Ground Water (30) 257-261
During unsteady or transient ground-water flow, the fluid mass per unit volume of aquifer changes as the potentiometric head changes, and solute transport is affected by this change in fluid storage. Three widely applied numerical models of two-dimensional transport partially account for the effects of transient flow by removing terms...
A reconnaissance study of herbicides and their metabolites in surface water of the midwestern united states using immunoassay and gas chromatography/mass spectrometry
E. Michael Thurman, D. A. Goolsby, M. T. Meyer, M. S. Mills, M.L. Pomes, Dana W. Kolpin
1992, Environmental Science & Technology (26) 2440-2447
Preemergent herbicides and their metabolites, particularly atrazine, deethylatrazine, and metolachlor, persisted from 1989 to 1990 in the majority of rivers and streams in the midwestern United States. In spring, after the application of herbicides, the concentrations of atrazine, alachlor, and simazine were frequently 3-10 times greater than the U.S. Environmental...
Effect of water saturation in soil organic matter on the partition of organic compounds
D.W. Rutherford, G.T. Chlou
1992, Environmental Science & Technology (26) 965-970
No abstract available. ...
Laboratory investigations on the role of sediment surface and ground water chemistry in transport of bacteria through a contaminated Sandy Aquifer
M. A. Scholl, R.W. Harvey
1992, Environmental Science & Technology (26) 1410-1417
No abstract available. ...
Enzymatic uranium precipitation
Y.A. Gorby, Derek R. Lovley
1992, Environmental Science & Technology (26) 205-207
No abstract available....
Riparian vegetation recovery patterns following stream channelization: A geomorphic perspective
Cliff R. Hupp
1992, Ecology (73) 1209-1226
Hundreds of kilometres of West Tennessee streams have been channelized since the turn of the century. After a stream is straightened, dredged, or cleared, basinwide ecologic, hydrologic, and geomorphic processes bring about an integrated, characteristic recovery sequence. The rapid pace of channel responses to channelization provides an opportunity to document...
U-Pb dating of uranium deposits in collapse breccia pipes of the Grand Canyon region
K.R. Ludwig, K. R. Simmons
1992, Economic Geology (87) 1747-1765
Two major periods of uranium mineralization are indicated by U-Pb isotope dating of uranium ores from collapse breeeia pipes in the Grand Canyon region, northern Arizona. The Hack 2 and 3, Kanab North, and EZ 1 and 2 orebodies apparently formed in the interval of 200 + or - 20...
Mixed-mode isolation of triazine metabolites from soil and aquifer sediments using automated solid-phase extraction
M. S. Mills, E.M. Thurman
1992, Analytical Chemistry (64) 1985-1990
No abstract available. ...
Influence of soil organic matter composition on the partition of organic compounds
D.W. Rutherford, C. T. Chiou, D.E. Klle
1992, Environmental Science & Technology (26) 336-340
No abstract available. ...
Classifying and mapping wetlands and peat resources using digital cartography
Cornelia C. Cameron, David A. Emery
1992, Conference Paper, ASTM Special Technical Publication
Digital cartography allows the portrayal of spatial associations among diverse data types and is ideally suited for land use and resource analysis. We have developed methodology that uses digital cartography for the classification of wetlands and their associated peat resources and applied it to a 1:24 000 scale map area...
Solution of the advection-dispersion equation by a finite-volume eulerian-lagrangian local adjoint method
R. W. Healy, T.F. Russell
1992, Conference Paper, Finite Elements in Water Resources, Proceedings of the International Conference
A finite-volume Eulerian-Lagrangian local adjoint method for solution of the advection-dispersion equation is developed and discussed. The method is mass conservative and can solve advection-dominated ground-water solute-transport problems accurately and efficiently. An integrated finite-difference approach is used in the method. A key component of the method is that the integral...
Semiempirical model of soil water hysteresis
J. R. Nimmo
1992, Soil Science Society of America Journal (56) 1723-1730
In order to represent hysteretic soil water retention curves accurately using as few measurements as possible, a new semiempirical model has been developed. It has two postulates related to physical characteristics of the medium, and two parameters, each with a definite physical interpretation, whose values are determined empirically for a...
Large lake basins of the southern High Plains: Ground-water control of their origin?
W.W. Wood, W. E. Sanford, C.C. Reeves Jr.
1992, Geology (20) 535-538
The origin of the ∼40-50 topographically large lake basins on the southern High Plains of Texas and New Mexico has been an enigma. Previous workers have considered deflation or evaporite dissolution at depth and subsequent collapse as the most probable mechanisms. However, the eolian hypotheses have been unable to provide...
Determination of selenium bioavailability to a benthic bivalve from particulate and solute pathways
S. N. Luoma, C. Johns, N.S. Fisher, N.A. Steinberg, R.S. Oremland, J.R. Reinfelder
1992, Environmental Science & Technology (26) 485-491
No abstract available. ...
Improved apparatus for measuring hydraulic conductivity at low water content
J. R. Nimmo, K.C. Akstin, K.A. Mello
1992, Soil Science Society of America Journal (56) 1758-1761
A modification of the steady-state centrifuge method (SSCM) for unsaturated hydraulic conductivity (K) measurement improves the range and adjustability of this method. The modified apparatus allows mechanical adjustments to vary the measured K by a factor of 360. In addition, the use of different flow-regulating ceramic materials can give a total K range covering...
Bioremediation of uranium contamination with enzymatic uranium reduction
Derek R. Lovley, Elizabeth J.P. Phillips
1992, Environmental Science & Technology (26) 2228-2234
Enzymatic uranium reduction by Desulfovibrio desulfuricans readily removed uranium from solution in a batch system or when D. desulfuricans was separated from the bulk of the uranium-containing water by a semipermeable membrane. Uranium reduction continued at concentrations as high as 24 mM. Of a variety of potentially inhibiting anions and...
Atrazine mineralization potential of alluvial-aquifer sediments under aerobic conditions
P.B. McMahon, F. H. Chapelle, M.L. Jagucki
1992, Environmental Science & Technology (26) 1556-1559
No abstract available....
D4Z: A new renumbering for iterative solution of ground-water flow and solute-transport equations
K.L. Kipp, T.F. Russell, J.S. Otto
1992, Conference Paper, Finite Elements in Water Resources, Proceedings of the International Conference
D4 zig-zag (D4Z) is a new renumbering scheme for producing a reduced matrix to be solved by an incomplete LU preconditioned, restarted conjugate-gradient iterative solver. By renumbering alternate diagonals in a zig-zag fashion, a very low sensitivity of convergence rate to renumbering direction is obtained. For two demonstration problems involving...
Comparison of purge and trap GC/MS and purgeable organic chloride analysis for monitoring volatile chlorinated hydrocarbons
Larry B. Barber, E. Michael Thurman, Yoshi Takahashi, Mary C. Noriega
1992, Ground Water (30) 836-842
A combined field and laboratory study was conducted to compare purge and trap gas chromatography/mass spectrometry (PT‐GC/MS) and purgeable organic chloride (POC1) analysis for measuring volatile chlorinated hydro‐carbons (VCH) in ground water. Distilled‐water spike and recovery experiments using 10 VCH indicate that at concentrations greater than...
Evaluation of methyl fluoride and dimethyl ether as inhibitors of aerobic methane oxidation
Ronald S. Oremland, Charles W. Culbertson
1992, Applied and Environmental Microbiology (58) 2983-2992
Methyl fluoride (MF) and dimethyl ether (DME) were effective inhibitors of aerobic methanotrophy in a variety of soils. MF and DME blocked consumption of CH4 as well as the oxidation of 14CH4 to 14CO2, but neither MF nor DME affected the oxidation of [14C]methanol or [14C]formate to 14CO2. Cooxidation of ethane and propane by methane-oxidizing...
Humic substances and trace metals associated with Fe and Al oxides deposited in an acidic mountain stream
Diane M. McKnight, R.L. Wershaw, K.E. Bencala, G. W. Zellweger, G. L. Feder
1992, Science of Total Environment (117-118) 485-498
Hydrous iron and aluminum oxides are deposited on the streambed in the confluence of the Snake River and Deer Creek, two streams in the Colorado Rocky Mountains. The Snake River is acidic and has high concentrations of dissolved Fe and Al. These metals precipitate at the confluence with the pristine,...
Patterns and rates of ground-water flow on Long Island, New York
Herbert T. Buxton, Edward Modica
1992, Groundwater (30) 857-866
Increased ground-water contamination from human activities on Long Island has prompted studies to define the pattern and rate of ground-water movement. A two-dimensional, fine-mesh, finite-element model consisting of 11,969 nodes and 22,880 elements was constructed to represent ground-water flow along a north-south section through central Long Island. The model represents...
