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W.W. Wood

Publications and source records attributed to W.W. Wood.

17 recordsLinked to original sources
USGS2009

Eolian transport of geogenic hexavalent chromium to ground water

A conceptual model of eolian transport is proposed to address the widely distributed, high concentrations of hexavalent chromium (Cr +6 ) observed in ground water in the Emirate of Abu Dhabi, United Arab Emirates. Concentrations (30 to more than 1000 μg/L Cr +6 ) extend over thousands of square kilometers of ground water systems. It is hypothesized that the Cr is derived from weathering of chromium-rich pyroxenes and olivines present in ophiolite sequence of the adjacent Oman (Hajar) Mountains. Cr +3 in the minerals is oxidized to Cr +6 by reduction of manganese and is subsequently sorbed on iron and manganese oxide coatings of particles. When the surfaces of these particles are abraded in this arid environment, they release fine, micrometer-sized, coated particles that are easily transported over large distances by wind and subsequently deposited on the surface. During ground water recharge events, the readily soluble Cr +6 is mobilized by rain water and transported by advective flow into the underlying aquifer. Chromium analyses of ground water, rain, dust, and surface (soil) deposits are consistent with this model, as are electron probe analyses of clasts derived from the eroding Oman ophiolite sequence. Ground water recharge flux is proposed to exercise some control over Cr +6 concentration in the aquifer.

Ground Water↗
USGS2007

Atmospheric bromine flux from the coastal Abu Dhabi sabkhat: A ground-water mass-balance investigation

A solute mass-balance study of ground water of the 3000 km2 coastal sabkhat (salt flats) of the Emirate of Abu Dhabi, United Arab Emirates, documents an annual bromide loss of approximately 255 metric tons (0.0032 Gmoles), or 85 kg/km2. This value is an order of magnitude greater than previously published direct measurements from the atmosphere over an evaporative environment of a salar in Bolivia. Laboratory evidence, consistent with published reports, suggests that this loss is by vapor transport to the atmosphere. If this bromine flux to the atmosphere is representative of the total earth area of active salt flats then it is a significant, and generally under recognized, input to the global atmospheric bromide flux.

Geophysical Research Letters↗
USGS2005

Quantifying macropore recharge: Examples from a semi-arid area

The purpose of this paper is to illustrate the significantly increased resolution of determining macropore recharge by combining physical, chemical, and isotopic methods of analysis. Techniques for quantifying macropore recharge were developed for both small-scale (1 to 10 km2) and regional-scale areas in and semi-arid areas. The Southern High Plains region of Texas and New Mexico was used as a representative field site to test these methods. Macropore recharge in small-scale areas is considered to be the difference between total recharge through floors of topographically dosed basins and interstitial recharge through the same area. On the regional scale, macropore recharge was considered to be the difference between regional average annual recharge and interstitial recharge measured in the unsaturated zone. Stable isotopic composition of ground water and precipitation was used us an independent estimate of macropore recharge on the regional scale. Results of this analysis suggest that in the Southern High Plains recharge flux through macropores is between 60 and 80 percent of the total 11 mm/y. Between 15 and 35 percent of the recharge occurs by interstitial recharge through the basin floors. Approximately 5 percent of the total recharge occurs as either interstitial or matrix recharge between the basin floors, representing approximately 95 percent of the area. The approach is applicable to other arid and semi-arid areas that focus rainfall into depressions or valleys.The purpose of this paper is to illustrate the significantly increased resolution of determining macropore recharge by combining physical, chemical, and isotopic methods of analysis. Techniques for quantifying macropore recharge were developed for both small-scale (1 to 10 km2) and regional-scale areas in arid and semi-arid areas. The Southern High Plains region of Texas and New Mexico was used as a representative field site to test these methods. Macropore recharge in small-scale areas is considered to be the difference between total recharge through floors of topographically closed basins and interstitial recharge through the same area. On the regional scale, macropore recharge was considered to be the difference between regional average annual recharge and interstitial recharge measured in the unsaturated zone. Stable isotopic composition of ground water and precipitation was used as an independent estimate of macropore recharge on the regional scale. Results of this analysis suggest that in the Southern High Plains recharge flux through macropores is between 60 and 80 percent of the total 11 mm/y. Between 15 and 35 percent of the recharge occurs by interstitial recharge through the basin floors. Approximately 5 percent of the total recharge occurs as either interstitial or matrix recharge between the basin floors, representing approximately 95 percent of the area. The approach is applicable to other arid and semi-arid areas that focus rainfall into depressions or valleys.

Ground Water↗
USGS2005

Chemical openness and potential for misinterpretation of the solute environment of coastal sabkhat

Sabkha deposits in the geologic record are commonly used to interpret the environmental conditions of deposition. Implicit in this use is the assumption that the solute system is chemically closed, that is, the authigenic minerals represent the composition of the fluids in their environment of origin. Thermodynamic and mass-balance calculations based on measurements of water and solute flux of contemporary Abu Dhabi coastal sabkha system, however, demonstrate that the system is open for sodium and chloride, where nearly half of the input is lost, but closed for sulfur, where nearly 100% is retained. Sulfur and chloride isotopes were consistent with this observation. If these sabkha deposits were preserved in the geologic record, they would suggest a solute environment rich in sulfate and poor in chloride; yet the reverse is true. In most coastal-sabkha environments, capillary forces bring solutes and water to the surface, where the water evaporates and halite, carnallite, sylvite, and other soluble minerals are precipitated. Retrograde minerals, such as anhydrite, calcite, dolomite, and gypsum, however, precipitate and accumulate in the capillary zone beneath the surface of the coastal sabkha. Because they possess relatively low solubility and are below the surface, these retrograde minerals are protected from dissolution and physical erosion occurring from infrequent but intense rainfall events. Thus, they are more likely to be preserved in the geological record than highly soluble minerals formed on the surface. ?? 2004 Elsevier B.V. All rights reserved.

Chemical Geology↗
USGS2002

Source of solutes to the coastal sabkha of Abu Dhabi

An ascending-brine model is proposed to address the observed isotope geochemistry, solute composition, and solute and water fluxes in the coastal sabkha of the Emirate of Abu Dhabi. Mass-balance measurements document that >95% of the solutes are derived from ascending continental brines; minor amounts are derived from rainfall and from groundwater entering from upgradient areas. Nearly 100% of the annual water loss is from evaporation and not lateral discharge. Direct rainfall on the sabkha and subsequent recharge to the underlying aquifer account for ~ 90% of the annual water input to the system; the remaining 10% comes from both lateral and ascending groundwater flow. Thus, the water and solutes in this system are from different sources. Solute concentrations of conservative (i.e., nonreactive) elements in the coastal, sabkha-covered aquifer are consistent with the fluid pore volumes of ascending brine calculated from hydrologic properties. Calcium to sulfate ratios and sulfur isotopes are consistent with this source of solute from the underlying Tertiary formations. Recharging rainwater dissolves halite and other soluble minerals on the surface, causing the solution to become more dense and sink to the bottom of the aquifer where it vertically mixes with less dense ascending brines. Solutes are returned to the surface by capillary forces and recycled or lost from the system by eolian or fluvial processes. Thus, the system becomes vertically mixed, consistent with the presence of tritium throughout the aquifer; but there is essentially no horizontal mixing of seawater with groundwater. The observed seawater solutes in the supratidal zone come from interstitial seawater trapped by the rapid progradation of the sediments into the Arabian Gulf and are not refluxed or laterally mixed. The ascending-brine model contrasts significantly with both the seawater-flooding and evaporative-pumping models previously proposed as a source of solutes to the coastal sabkha of the Emirate of Abu Dhabi. Use of these earlier models leads to incorrect conclusions and raises serious questions about their applicability in the evaluation of sabkhat in the geologic record.

Abu Dhabi↗
USGS1996

Chloride mass-balance method for estimating ground water recharge in arid areas: Examples from western Saudi Arabia

The chloride mass-balance method, which integrates time and aerial distribution of ground water recharge, was applied to small alluvial aquifers in the wadi systems of the Asir and Hijaz mountains in western Saudi Arabia. This application is an extension of the method shown to be suitable for estimating recharge in regional aquifers in semi-arid areas. Because the method integrates recharge in time and space it appears to be, with certain assumptions, particularly well suited for and areas with large temporal and spatial variation in recharge. In general, recharge was found to be between 3 to 4% of precipitation - a range consistent with recharge rates found in other arid and semi-arid areas of the earth.

Asir mountains, Hijaz mountains↗
USGS1995

How wet is wet? Precipitation constraints on late Quaternary climate in the southern Arabian Peninsula

It is generally recognized that the southern Arabian Peninsula has had two wet periods in the late Quaternary. To quantify ‘wet’ a 28 000 year old capillary surface associated with a paleowater-table was mapped and used as a surrogate for the water table in a ground-water model. Analysis of this model suggests 1.4 mm year −1 of recharge is necessary to support the water table at the mapped elevations during the wet period. Climatic relations between rainfall and recharge in arid areas infer that annual rainfall during this wet period was approximately 200 ± 50 mm year −1 or approximately five times the present rate.

Journal of Hydrology↗
USGS1992

Large lake basins of the southern High Plains: Ground-water control of their origin?

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 convincing arguments as to how the wind selectively erodes the thick, deflation-resistant calcrete "caprock" that is persistent over much of the southern High Plains. Furthermore, recent detailed studies on some of the basins show no significant evaporite dissolution at depth, and neither mechanism offers a satisfactory explanation as to why the basins are almost universally associated with subsurface topographic highs, or why they are absent where the High Plains aquifer thickness exceeds 60 m. We address these latter concerns and modify the deflation hypothesis by proposing that the calcrete caprock may never have been deposited in the areas now occupied by the basins. The absence of calcrete deposition is proposed to have resulted from high water tables caused by an increase in hydraulic gradient where aquifers thinned above bedrock highs. A high water table close to and/or intersecting the surface prevents deposition of calcrete, and, thus, the uncemented surface would be more susceptible to deflation than the surrounding calcrete-covered areas after decline of the water table. The rise in water table associated with bedrock highs is documented by numerical simulation using boundary conditions and hydrologic parameters representative of the southern High Plains.

Geology↗
USGS1991

Brine evolution and mineral deposition in hydrologically open evaporite basins

A lumped-parameter, solute mass-balance model is developed to define the role of water outflow from a well-mixed basin. A mass-balance model is analyzed with a geochemical model designed for waters with high ionic strengths. Two typical waters, seawater and a Na-HCO3 ground water, are analyzed to illustrate the control that the leakage ratio (or hydrologic openness of the basin) has on brine evolution and the suite and thicknesses of evaporite minerals deposited. The analysis suggests that brines evolve differently under different leakage conditions. -from Authors

American Journal of Science↗
USGS1990

Ground-water control of evaporite deposition

Topographically closed basins may be hydrologically open as a result of seepage losses to underlying or surrounding ground-water systems. In such cases, these losses can have a substantial control over the suite and the thicknesses of evaporite minerals formed in the basin. The ratio of ground-water outflow to inflow (flux ratio) in hydrologically open basins is as important in determining the mineralogy and thicknesses of evaporite deposits as the solute composition of the inflow water. Attainment of steady state flux ratios permits large thicknesses of two or three minerals to form rather than thin veneers of many minerals. The presence or absence of glauberite, mirabilite, halite, bloedite, polyhalite, and hexahydrite, caused by subtle changes in the ground-water seepage is illustrated using an example from the Southern High Plains of Texas and New Mexico. However, the model is general and is applicable with any solute composition including that of seawater and the use of surface rather than ground water. An analytical, lumped parameter, solute mass balance model is developed to define the concept of a ground-water flux ratio as it applies to topographically closed basins in which evaporation exceeds precipitation. Diffusion, advection, and density-driven flow are proposed as mechanisms by which solutes can escape to the ground water from these closed basins. The geochemical reaction computer program PHRQPITZ is used to document the effects of various flux ratios on the mineralogy and thickness of deposits. Solute analyses used in conjunction with the model can be used to screen prospective basins as well as to provide insights for exploratory drilling program.

Texas, New Mexico↗
USGS1987

Playa-lake basins on the Southern High Plains of Texas and New Mexico: Part II. A hydrologic model and mass-balance arguments for their development.

Hydrologic, geologic, geomorphic, and mass-balance data suggest that most of the ∼30,000 playa lake basins on the Southern High Plains have developed by a combination of dissolution of caliche and piping of surface material into the unsaturated zone rather than by eolian processes as has generally been stated. A conceptual model suggests that particulate organic material, much of which is sorbed on smectite clays, is carried downward from the surface into the unsaturated zone by recharging water. The organic material is oxidized to CO 2 , which dissolves in the water, forms carbonic acid, and dissolves lithologic carbonates. Because organic material is transported and oxidized deep in the unsaturated zone, CO 2 concentrations are much higher at depth than in the soil zone, and recharging water remains thermodynamically subsaturated with respect to carbonates and thus able to dissolve them throughout the unsaturated zone. Dissolution promotes lithologic instability, leading to piping and eluviation of material within the unsaturated zone. Playa basins expand laterally as recharge is concentrated at the edge of the playa floor because of lowered permeability in the center that results from accumulation of clays and other fine sediment. Mass-balance calculations of gas, liquid, and solid fluxes beneath a playa basin suggest that sufficient mass is transported to account for the volume of the depression. Particulate flux is estimated by relating it to the CO 2 flux out of the unsaturated zone. Solute flux is estimated from the difference between input values from the playa lake water and that observed in ground water. Gas flux is measured directly from gas samples at specific depths below the: surface.

Geological Society of America Bulletin↗
USGS1985

Origin of caves and other solution openings in the unsaturated (vadose) zone of carbonate rocks: A model for CO2 generation

The enigma that caves and other solution openings form in carbonate rocks at great depths below land surface rather than forming from the surface downward can be explained by the generation of CO2 within the aquifer system. In the proposed model, CO2 is generated by the oxidation of particulate and/or dissolved organic carbon that is transported from the land surface deep into the unsaturated zone by recharging ground water. The organic material is oxidized to CO2 by aerobic bacteria utilizing oxygen that diffuses in from the atmosphere. Because gas transport in the unsaturated zone is controlled largely by diffusion, steady-state generation of even minute amounts of CO2 deep in the unsaturated zone results in the creation of large concentrations of CO2 at depth as it establishes a concentration gradient to the surface or other sink.

Geology↗
USGS1981

Preliminary data from a series of artificial recharge experiments at Stanton, Texas

A series of artificial recharge experiments was conducted by the U.S. Geological Survey at an experimental site located in Stanton, Texas. Five tests were performed from March 1977 through December 1978 to: (1) Evaluate the hydraulic properties of the aquifer; (2) test sampling and monitoring equipment; (3) compare tracers for future use in hydrologic investigations; and (4) determine the radial and vertical distribution of hydraulic properties at the site. Suites of inorganic, and both volatile and nonvolatile organic tracers were used in the tests, and comparative data were obtained from sampling points at several radial distances and depths from the injection well. Hydraulic data from aquifer tests and geologic data from core material also were obtained during the investigation.

Texas↗