ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01704.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA new computational methodology for capture zone design for contaminated ground‐water remediation is described. This method has been implemented in a computer model which utilizes both simulation and optimization techniques. The procedure determines the well locations and pump rates which will produce a desired ground‐water flow field at minimum cost. In this paper, the design procedure is described along with an example of its use on a hypothetical aquifer system. Numerical experiments are presented which determine the effect on remediation cost of alternate well locations. It is found that different well locations can have a major impact on the overall cost of remediat

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01705.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractGround water in the Pampa del Tamarugal basin part of the desert of Northern Chile is the main water resource for cities and agricultural activities in the region. As the area received virtually no precipitation, the source of the ground water is rains in the high Andes. Aquifer recharge has been linked to a drainage system associated with this part of the Andes. Ground‐water flow is from northeast to southwest, and a flow component from east to west is also observed in some parts of the basin. In general, the water becomes very saline towards the western part of the basin, giving rise to salt lakes (salares) in ground‐water discharge areas. However, isotopic, chemical, and geological evidence plus ground‐water temperatures distribution, suggest the existence of a different recharge mechanism linked to a regional ground‐water flow system. It is suggested that low‐salinity water emerges from ground water recharged in the high Andes through a basement fault system underneath the basin. This model has implications for the future exploration for new fresh‐wate

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01706.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe best locations for water wells in crystalline terrains of semiarid lands are narrow, densely fractured and altered belts, normally associated with fault zones and folding axes. A simple electrical procedure, based on vertical soundings and multiple resistivity profiling, has been successfully applied for the structural mapping of these two‐dimensional aquifers in northeast Brazil. The apparent resistivity sections constructed from partial electrical sounding measurements taken at a closely spaced interval along a traverse were interpreted using a finite‐difference algorithm. This scheme allowed detailed description of the lateral and vertical extent of fractured aquifers and some of their hydrogeophysical characteristics. The results of a selected case study from Bahia state compare satisfactorily with available geophysical logs and production data of existing we

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01707.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA laboratory study was undertaken to evaluate the flow of the following organic solvents and their aqueous solutions through bentonite and kaolin clays: benzene, toluene, p‐xylene, nitrobenzene, trichloroethylene, tetrachloroethylene, ethyl acetate, 2‐butanone, and phenol. In each experiment, one pore volume of a 0.005 N CaSO4solution (water) flowed through the clays, followed by several pore volumes of an aqueous solution of one of the organic solvents, and then by about three pore volumes of the neat organic solvent. The hydraulic conductivity for the aqueous organic solutions was not significantly different from those for water, and ranged from 4.6 × 10‐7to 14.4 × 10‐7and from 0.6 × 10‐7to 0.8 × 10‐7cm/sec through the kaolin and bentonite clays, respectively. The flow of the neat solvents through either the bentonite or kaolin clay increased by up to two orders of magnitude. The aqueous solutions did not change the physical appearance of the clays. In general, the more hydrophobic solvents caused the clays to shrink, producing distinct large vertical cracks. The hydrophilic solvents typically caused the clays to aggregate and fracture, forming a network of cracks. The kaolin clay appeared to aggregate more readily than the bentonite clay. The higher swelling of the clays in water than in the neat organic solvents likely caused the physical changes in the clays and the rapid flow of the neat solven

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01708.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractGround water in the immediate vicinity of an area previously used for the disposal of charcoal manufacturing wastes has been shown to contain low levels of phenolic and polycyclic compounds. Based on the analysis of samples obtained from monitoring wells, the levels of the organic contaminants are reduced to near or below the detection limit within a distance of 100 meters downgradient of the fill. Examination of the ground‐water chemistry indicated that the aquifer is essentially aerobic across the site, except in the immediate vicinity of the fill. At this point, dissolved oxygen is apparently depleted due to the biodegradation of organic contaminants introduced into the ground water, with a concomitant increase in the inorganic carbon concentration. Laboratory microcosm experiments demonstrated that the naturally occurring microorganisms can readily degrade a mixture of the predominant organic contaminants. Half‐lives for biodegradation were in the range of 3 to 8 days for phenolic substrates, and 11 to 18 days for naphthalene. Computer model simulations indicated that the attenuation observed in the aquifer cannot be explained in terms of physical processes such as adsorption or dispersion, but is consistent with biological degradat

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01709.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe cause of soil salinization in a 21‐ha area of gently rolling topography in Alberta was investigated. The geology of the basin consists of lenticular Cretaceous sediments overlain by tills and lacustrine deposits. Interpretation of vertical hydraulic‐head data showed that regional discharge of ground water from bedrock is not a cause of salinization in the study area. Results of stream‐function modeling suggested that most of the water causing salinization is not derived from local topographic highs. Modeling results also suggested that the direction of ground‐water flow throughout the area is vertically downward through unconsolidated Quaternary deposits and into bedrock. Tritium analyses of pore water distilled from core samples confirmed that the ground water causing salinization was not derived from the local topographic highs, nor from deeper geologic deposits. Hydrograph analysis indicated that the salinization was derived from evaporation from seasonally high water tables caused by ponded surface water and spring snowmelt in localized depressiona

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01710.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractDelineating ground‐water flow paths is difficult to accomplish in desert terranes because paucity of wells and boreholes yields little data to construct hydrologic interpretations based upon physical parameters. This is especially true in the Big Bend National Park where, in a study area encompassing over 500 km2, there are only four wells and six perennial springs. These wells and springs were sampled and analyzed for major‐element chemistry as well as for stable and naturally occurring radioactive isotopes to identify sources of recharge for the springs which discharge along banks of arroyos incised in alluvial pediment lying about 900 meters below the uplands of the Chisos Mountains.The springs recharge could be from three sources: (1) infiltration of precipitation falling on the desert floor to discharge at nearby arroyos; (2) infiltration of water at the onlap of the alluvial fan with the crystalline rock of the Chisos uplands and subsequent flow within the fan toward lowland springs; and (3) upward migration of deep‐seated water. Of these, the third scenario is least compatible with respect to temperature, dissolved oxygen, and isotopic data.The waters total dissolved solids and calcite saturation indices increase with decreasing altitude, suggesting recharge from the Chisos uplands. However, temperature, dissolved oxygen, δ18O, tritium, and Carbon‐14 data indicate a significant recharge component to springs occurs by infiltration of infrequent precipitation falling on the arid alluvial lowlands. This water percolates through the soil zone to aquitards (essentially calcitic hardpans) which function as horizons which channel the water laterally toward discharge in springs. The springs recharge‐to‐discharge paths are short with flow being slow enough to reflect seasonal temperature differences of greater than 12°, yet recent enough to contain post‐bomb spikes of tritiu

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01711.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe median‐polish statistical method was used to test and quantify chloride (Cl‐), electrical conductivity (EC), pH, and fluorescence of laundry detergent optical brighteners as indicators of ground‐water pollution from septic systems. The septic systems were located in coarse‐textured soils over a high water table close to discharge areas in south‐central Wisconsin. Parameters were measured monthly for two years in septic tank effluent samples and in water samples collected downgradient from 17 septic systems and from upgradient background samples. The median‐polish technique was excellent for comparing hydrochemical data: Cl‐was a conservative tracer and the most suitable indicator of contaminant plumes; EC was semiconservative and EC and pH were only acceptable; and fluorescence was unacceptable. Fluorescence as an optical brightener in septic tank effluents ranged between 0.14 and 0.98 mg/1 with an average value of 0.40 ± 0.16 mg/l. In ground water downgradient from the septic systems, fluorescence levels were within the background levels. Natural substances such as humic and fulvic acids were probably the sources of fluorescence in ground water, not optical brighteners, because optical brighteners did not pass through septic systems drainfields. Fluorescence of naturally occurring compounds in ground water was between>0.01 and 260 μ/1 with a mean of ≤51± 14 μ/1 expressed as optical brightener. Nitrification in the soil below the drainfields caused ground‐water pH values to decrease within a few mete

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01712.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSixteen Wenner and Schlumberger array electrical soundings were made over portions of the Mallard North landfill in DuPage County, Illinois, to map the gross layered structure of a closed landfill. Sounding curves were fit to standard type curves and values inverted in a least‐squares procedure to yield multilayer geoelectrical models. Wood, newspaper, cloth, glass, plastic, and metal refuse interspersed with soil exhibited resistivities of 9–19 ohm‐m (unsaturated) and 2–7 ohm‐m (leachatesaturated). Mature unfractured clay‐till cover material exhibited a resistivity of about 30 ohm‐m, and its thickness was estimated to within 27% of its true thickness. Larger errors were encountered over fractured and freshly emplaced cover. Soundings were also inverted to yield accurate leachate levels and refuse thicknesses (errors for both averaged about 30%). While Schlumberger and Wenner soundings produced models with comparable accuracy, Schlumberger soundings were less sensitive to cover heterogeneities and easier to deploy. Moore's cumulative resistivity interpretation method was found to be unreliable in interpreting this type of resistivity data. Fractures present in the cover material, lateral changes in leachate level, and variations in cover thickness and resistivity contributed to errors in interpretation. Despite these limitations, models generated from electrical resistivity soundings are reasonably accurate in their depictions of internal conditions in this type of landfill. Such soundings could be used to map internal structure in other layered landfills that lack construction and operat

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01713.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY