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  • Articles  (8)
  • Blackwell Publishing Ltd  (7)
  • Oxford University Press  (1)
  • American Geophysical Union
  • 2005-2009
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  • 1994  (8)
  • Energy, Environment Protection, Nuclear Power Engineering  (7)
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  • Articles  (8)
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  • 2005-2009
  • 1990-1994  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 32 (1994), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 14 (1994), S. 0 
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Nonparametric prediction limits can be useful statistical tools for ground water monitoring at facilities regulated under RCRA Subtitle C. Subtitle D. and similar regulations. New, exact tables arc presented for both “1 of m” plans (m chances to gel one observation inbounds at each of r monitoring wells to avoid a statistically significant increase) and “California” plans (first or all of the next m-1 observations inbounds at each well). The tables provide per-constituent significance levels (false positive rates) as a function of the background sample size n. m. r, the prediction limit (the largest or the next to largest, background observation), and the confirmatory resampling plan selected.When used in a monitoring program, future observations from several wells are compared with a prediction limit obtained from a common background sample. The table significance levels therefore depend critically on having IID (independent and identically distributed) observations. In particular, the false positive rate computations are not valid, and the procedures should not be used, with constituents whose measurements exhibit inherent spatial or systematic temporal variability.Recent U.S. EPA guidance explicitly encourages controlling facility-wide false positive rates over both constituents and wells. Nonparametric prediction limits, particularly with California resampling plans, will have greater difficulty in meeting the new. lower per-constituent false positive rate goals than previous ones, especially if many constituents are involved. Nonetheless, nonparametric prediction limits remain superior to other commonly used procedures for dealing with data with high proportions of nondctects.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 32 (1994), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 32 (1994), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Subsurface unsaturated soils and ground water directly beneath a manufacturing site have been shown to contain benzene. The vadose zone appears to be the current source for benzene to the aquifer. Although the ground water contains several mg/1 of contamination in the area immediately beneath the source, benzene was not detected in monitoring wells approximately 400 feet downgradient. Based upon the length of time benzene has been present in the ground water, as well as the permeability of the aquifer, physical processes alone such as adsorption and advection/dispersion are unlikely to account for the observed attenuation. Results from this investigation indicated the attenuation was primarily due to the natural biological processes occurring within the aquifer.Evidence for the natural bioremediation of benzene from the ground water included: (1) analysis of ground-water chemistry, (2) laboratory studies demonstrating benzene biodegradation in aquifer samples, and (3) computer simulations examining contaminant transport. Laboratory studies indicated that under conditions similar to those encountered in the ground water, benzene was degraded to carbon dioxide by the naturally occurring microorganisms. The aerobic degradation of benzene in aquifer samples was quite rapid, with the time for 50% disappearance of the parent compound ranging from 4 to 14 days. In situ analyses of the ground water indicated significant levels of dissolved oxygen throughout the aquifer. Thus, the availability of oxygen should not limit the aerobic biodegradation of benzene. However, benzene was also shown to degrade under anaerobic conditions in microcosms prepared with aquifer material. Computer model simulations were also conducted to examine the processes influencing the transport of benzene in the aquifer. Results from the model simulations indicated biodegradation was the dominant process influencing attenuation of the contaminant.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: This communication describes novel methods to measure site-specific sorption data, and to determine if biodegradation of pentachlorophenol (PCP) in complex technical-grade formulations occurs at industrial facilities. Ground-water slurry samples containing between 0.012 and 230 mg/l PCP were collected from a former wood treating site, the liquid and solid fractions separated, and both fractions analyzed for PCP using selective ion monitoring to determine sorption coefficients (Kd(PCP)). Although field sorption coefficients could not be represented by simple Freundlich and Langmuir isotherms, an empirical hyperbolic function (Kd(PCP)) = 0.054 + 0.086/Caq) fit the isotherm (r 〉 0.99), demonstrating that for PCP 〉 10 mg/l, no measurable retardation occurred in the aquifer. Biodegradation of PCP in ground water was apparent when PCP concentrations were 〈 20 mg/1, while at higher concentrations, PCP in the technical-grade formulation appeared to break down less readily. The results imply that, at the plume periphery, PCP in the subsurface will be attenuated and degrade, while at higher concentrations (i.e., at the source), PCP is mobile, and more recalcitrant to degradation.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 32 (1994), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Measurements of air-permeability in outcrops provide a means of obtaining numerous spatially distributed measurements for statistical analysis and subsequent parameterization of ground-water flow and transport modeling. The air-minipermeameters previously used for such studies generally consist of a compressed air source, rotameters, and diaphragm gauges. We present a lightweight syringe-based air-minipermeameter (LSAMP) design that is significantly more portable than previous instruments. The prototype model is contained in a 12.7 × 15.2 × 23 centimeter (5 × 6 × 9 inch) electrical box and weighs approximately 2 kilograms. The prototype LSAMP has a sampling range of 0.5 to 200 darcys. Individual measurements in this range require less than one minute. Permeability measured with the LSAMP closely correspond to permeability measured with a traditional minipermeameter and those measured on cores. Measurement error caused by soil moisture is less than 5 percent for volumetric water contents less than 5 percent. An analysis of variance on 38 triplicate measurements indicates that the variability associated with measurement error is much less than the range of measured values. Repeated permeability measurements under field conditions on two standard cores indicate that while the measurement error is greater under field conditions, the prototype device field performance is consistent with laboratory calibration results.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water monitoring & remediation 14 (1994), S. 0 
    ISSN: 1745-6592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Current federal ground water monitoring statistical regulation dates from the revised RCRA Subtitle C Final Rule of 1988. That rule was a considerable advance over previous RCRA statistical rules. However, two major problem areas remained: facility-wide false positive rate (FWFPR) control and spatial variability. Progress has been made in the 1991 Subtitle D Final Rule and in guidance: the 1992 Addendum to Interim Final Guidance in particular includes a substantial conceptual advance toward resolving the FWFPR problem. Other areas of improvement include normality testing and distribution assumptions, dropping the four independent samples per monitoring period requirement, allowing a preliminary evaluation short of a 40 CFR Part 258 Appendix II assessment upon finding a statistically significant increase, and suggesting superior alternatives to analyses of variance (ANOVAs) and tests of proportions.The problem of dealing with natural spatial variability remains. Although certain techniques listed in the regulations can control for inherent spatial variability and the performance standards require doing so “when necessary,” little attention has been paid to the ubiquity of such spatial variation. Moreover, regulatory traditions favoring upgradient-downgradient comparisons often make control of natural spatial variation difficult and ineffective. With new. lined facilities easily implemented statistical solutions are available; however, dealing with the several existing solid waste facilities which will now be regulated under Subtitle D will present major challenges.In short, the 1988 revision of the Subtitle C rules made it more possible to provide statistically sound monitoring programs, and there has been steady progress since then. Challenges remain, however. These vary from slate to slate, particularly with regard to controlling false positives and false negatives in the presence of natural spatial variability.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 1994-01-01
    Print ISSN: 0955-792X
    Electronic ISSN: 1465-363X
    Topics: Computer Science , Mathematics
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