ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01719.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractChemical and biological reaction rates are required in estimating migration rates of many reactive contaminants in ground water, and as input data for mathematical models. Reaction rates must be measured, and depend on environmental conditions that are often difficult to duplicate in the laboratory. In situ rate measurement minimizes the difficulties of controlling environmental variables such as temperature, pH, Eh, DO, solution and solid phase composition, and bacterial population.The instrument described in this paper isolates a 1.9 liter portion of an aquifer for in situ biochemical rate measurement. The device has been used successfully to measure the rate of reactions involving inorganic and organic contaminants in sandy aquifers. Two applications of the device, measurement of denitrification rates and rates of biodegradation of benzene, are presented.

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01720.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAlkalinity measurements are routinely conducted as part of standard water–quality determinations. Often, very little interpretation of the values is attempted, and the entire alkalinity is attributed to carbonate or bicarbonate. When landfill leachates are involved, this assumption could be misleading in terms of plume mapping, determining the incrustation potential of the water, or assessing the likelihood of methane generation because substances other than carbonate, for example acetate, can contribute significantly to the sample's alkalinity.A set of landfill leachate samples was collected and analyzed for alkalinity and volatile fatty acids. Acetate was the only organic acid identified. A very strong correlation was observed between acetate and alkalinity. Actual titration curves (volume of acid vs. pH) were compared with curves calculated assuming that acetate and bicarbonate were the two major species contributing the total alkalinity. Excellent agreement was observed between the experimental and theoretical data. Distinct differences in the shapes of the curves for carbonate–dominated and acetate‐dominated alkalinities make it possible to distinguish these two classes of water solely on the basis of alkalinity measurements. Water containing acetate titrates with an equivalence point which is less distinct than water containing only carb

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01721.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAquifer tests of confined aquifers in deep formations can yield inaccurate specific–storage and storage‐coefficient estimates if the distance between the pumped and observation wells is imprecisely known. The distance between the wells can be uncertain because small deviations in the vertical alignment of deep wells can markedly change the distance between the perforated intervals of the wells. Uncertain distance between wells may seriously degrade the accuracy of specific‐storage or storage–coefficient values calculated from aquifer–test data obtained from closely spaced wells.A method is proposed whereby compression of the aquifer matrix can be measured during an aquifer test and used to calculate specific‐storage and storage–coefficient values without knowledge of the distance between the pumped and observation wells. In a field trial of the method, specific–storage and storage‐coefficient values calculated from aquifercompression data were 8.16 × 10‐7and 3.04 × 10‐4, which is nearly identical to values (8.04 × 10‐7and 2.99 × 10‐4) obtained from longer–term monitoring of aquifer barometric efficiency. Additional comparison with results of a Theis analysis of drawdown data indicates that the aquifer compression data may provide a more accurate determination of specific–storage and storage–coefficient values than would be possible even if the vertical alignment of the pumped and

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01722.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe bedrock profile of an east–central Pennsylvania watershed contains a shallow weathered fracture layer. To begin quantifying the effects of this fracture layer on ground–water movement, two valley cross sections were chosen for detailed investigation. One section represents the typical upland watershed situation where the regional ground water is in contact with the stream for only part of the year, while at the other section the regional ground water is in perennial contact with the stream. Rock cores extracted from the sections reveal a pattern of extensive fracturing to approximately 50 ft directly under the stream thinning to a relatively uniform 30–ft deep fracture layer away from the channel. Limited seismic investigations support these observations. Piezometers within each cross section show that hydraulic conductivity differs between the shallow fracture layer and the relatively unfractured zone below and that there is great variability in conductivity within the fracture layer itself. Lateral flow generally occurs within the fracture layer to within approximately 50 ft of the stream; here a converging flow pattern indicates ground–water discharge to the stream. Under wet conditions, the stream in each section serves as a point of ground‐water discharge, while under dry conditions, the more upland section shows no ground–water discharge to the land surface. Rather, subsurface flow is likely occurring beneath and parallel to the channel controlled by a discharge point at some downstream location. Finally, water–quality samples from the piezometers indicate a direct effect of overlying land use on water quality within the shallow f

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01723.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractVelocity fields computed from simulated flows from a steady–state, three–dimensional numerical model of a glacialdrift/carbonate–bedrock aquifer system were used in conjunction with a particle–tracking program to delineate traveltimerelated capture areas of a municipal wellfield and to compute flow paths and advective traveltimes from hypothetical spill sites located along interstate highways and heavily traveled State routes. Results indicate the municipal wells operated by the City of Columbus, Ohio, capture flow from certain highway segments but other discharge points, including quarrydewatering systems, the Scioto River, and Big Walnut Creek, capture flow from other highway segments. Advective traveltimes from three hypothetical spill sites to the municipal wells range from 900 to 5,100 days under normal pumping rates and from 450 to 3,100 days under estimated maximum pumping rates. The 2,000–day capture area of the wellfield is approximately 30 percent larger (16 square miles) and contains approximately 4.5 more miles of highway under estimated maximum pumping rates compared to normal pump

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01724.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractHydrological investigations were conducted to determine the aquifer characteristics, recharge boundary location, and the amount of ground water which can be withdrawn safely in order to minimize potential ground–water contamination from open pit coal mining. Analysis of data obtained from bore holes drilled in the study area has revealed two aquifers: (1) an unconfined composed of medium–grained sandstone, and (2) confined composed of medium– to coarse–grained sandstone.A pumping test was conducted in Jayant block study area on the confined aquifer. Accordingly, the values for the transmissivity (T), storage coefficient (S), and hydraulic conductivity (k) obtained are 84.14 m2/day, 4.076 × 10‐4, and 4.2 × 102m /day, respectively. The results of the pumping tests indicated that a recharge boundary is located at a distance of 163 m. The recharge boundary was determined to be a stream trending N–S and situated at about 200 meters from the pumping well, closely corroborating the field situation with pump test data.From these studies it is concluded that water–supply wells should be completed in the confined aquifer. The impact of surface mining of coal on the ground–water system in Singrauli Coalfield, Central India has been investigated. Surface–water and hydrogeologic analyses were conducted in Jayant block. Field studies measured the infiltration characteristics of surface‐mined land, determined surface–water runoff, and analyzed the hydrogeologic impacts of surface mining. This study provides the framework for three–dimensional analysis of such problems as the hydrogeology, risk of potential contamination, mine flooding, highwall stability, a

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01725.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAquifer heterogeneities defined by mapping and correlating lithofacies derived from existing geologic and borehole geophysical data at the U.S. Department of Energy's (DOE) Hanford Site (south–central Washington) were compared to tritium migration trends within the unconfined aquifer. Lithofacies percentage maps proved useful in defining large–scale (on the order of miles) tritium migration pathways at Hanford but were not sufficiently detailed to serve as unambiguous predictors of these pathways. Results suggest that: (1) incorporation of geologic parameters more closely related to hydraulic properties (e.g., quantified grain size and sorting, degree of cementation, packing arrangement, sedimentary structures, and grain shape), and (2) conscientious integration of all hydrogeologic data at the Hanford Site (and elsewhere) will allow definition of three‐dimensional aquifer elements termed “hydrofacies” and enhance reliable prediction of contaminant migration pathways. Strict reliance on standard fluvial models in the evaluation of lithofacies at Hanford is not appropriate for predicting plume migration because of the complex depositional and erosional history of the sediments comprising the unconfined aquifer. Use of “hydrofacies” ultimately may serve as the appropriate conceptual framework for predicting pl

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01726.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe potential for and variables affecting enhanced aerobic biodegradation of14C‐labeled trichloroethene (TCE) and 1,2‐dichloroethane (1,2‐DC A) were evaluated using laboratory columns packed with fully saturated sandy aquifer material. The column fluids were exchanged weekly to simulate the growth of native microorganisms capable of biotransforming halogenated aliphatics. The exchange solutions for seven columns, one of which served as a control, contained dissolved oxygen as the electron acceptor. The electron donor, or primary substrate, for another column was dissolved propane, and the remaining five columns were fed varying concentrations of dissolved methane.Propane was not consumed, and TCE degradation did not occur in this column. However, methane was utilized in other columns, and the resulting stimulated populations mineralized both TCE and 1,2‐DCA to CO2. Little or no TCE degradation occurred when the methane concentration was 4.5 mg/1, but when the methane was reduced to 1.5 mg/1, degradation occurred. TCE degradation was greatest when either a low methane concentration (1.5 mg/1) or an alternating pulse of methane (4.5 mg/1 or 1.5 mg/1) with oxygen one week followed by oxygen only the next was used. Nutrient supplements (NH4+and PO42‐) did not conclusively enhance TCE degradation.When TCE addition was stopped and methanotrophic bacteria stimulation was continued, half of the14C from previously sorbed TCE that was subsequently eluted by exchange was present as nonvolatile compounds and CO2, and the other half as TCE. With a caution that the results obtained are site‐specific, they do suggest that the addition of methane and oxygen to water circulated through a ground‐water system to remove TCE by aboveground treatment can, in some cases at least, result in a doubling of the rate of removal and affect mineralization of about one‐half of

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01727.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSoil and ground‐water contamination by petroleum products, such as gasoline and oils, is widespread. A laboratory study was conducted to evaluate the relative suitability of 10 commercial surfactants for washing residual levels of automatic transmission fluid (ATF) from sandy material. The surfactants included at least one example for each of four main groups of commercial surfactants: (1) ethoxylated alcohols (nonionic), (2) ethoxylated nonylphenols (nonionic), (3) sulfates (anionic), and (4) sulfonates (anionic).Several properties of aqueous solutions of the surfactants (0.00001 to 5.0% v/v) were measured and used in evaluating their suitability. The extent of dispersion of soil colloids was measured as the turbidity (in formazin turbidity units, FTU) of soil/surfactant solution mixtures. The detergency of the surfactant solutions and the extent to which they solubilized the ATF were measured. The critical micelle concentration, which ranged from 0.05 to 5.0 percent, was measured and used to select the aqueous concentration of the surfactants in washing experiments. The amount of ATF removed from the sand ranged from about 23% by washing with water to more than 80% by washing with ethyoxylated alcohol surfactants. ATF was best removed from the soil by washing with a 0.5% aqueous solution of either alkoxylated alcohol ether, ethoxylated alcohol, or nonylphenol ether sulfate. An ethoxylated alcohol surfactant was selected for scale‐up laboratory and field tests because this surfactant caused low soil‐colloid dispersion and high ATF dispersion and solubilization, and was effective in washing ATF from th

ISSN:0017-467X    

DOI:10.1111/j.1745-6584.1990.tb01728.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY