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Stable isotopic investigations of in situ bioremediation of chlorinated organic solvents. 1997 annual progress report
No full text'The author has made significant progress in developing innovative methods for investigating the mechanism and extent of in situ bioremediation of chlorinated organic solvents. These methods use precise isotopic ratio measurements of chlorine and carbon in reactant and product species in laboratory experiments and in materials from field demonstration sites. Specific tasks completed during FY 1997 include: (1) refinement and publication of a new analytical method for precise determination of chlorine and carbon isotope ratios in chlorinated volatile organic compounds; (2) laboratory experiments involving biological degradation of chlorinated solvents in liquid cultures and soil columns; and (3) use of chlorine and carbon isotope ratios to investigate natural attenuation of trichloroethene at the Paducah Gaseous Diffusion Plant. This work can have immediate impact because it will provide the fundamental basis for a new and cost-effective means of evaluating and monitoring the effectiveness of in situ bioremediation schemes for chlorinated organic solvents in soils, vadose horizons, and groundwater plumes.
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Stable isotopic investigations of in-situ bioremediation of chlorinated organic solvents. 1998 annual progress report
No full text'Contamination of soils and groundwaters with chlorinated aliphatic hydrocarbons (CAHs) is one of the most serious environmental problems in the DOE system and in the nation at large. These compounds are designated as priority pollutants by the US Environmental Protection Agency (EPA) and are known or suspected to be carcinogenic or mutagenic in humans. These compounds are readily transported by groundwater and are not reduced to acceptable concentrations for human consumption by most municipal water supply treatments; thus the compounds represent a significant hazard to a large portion of the human population. In situ bioremediation is an emerging technology that shows great promise for mitigation of CAH contamination at many sites. One of the most severe limitations of in-situ bioremediation is the difficulty of proving when it is working at a given site. The concentrations of CAHs and their degradation products in plumes may be difficult to relate to the efficiency of the remediation process because of dilution effects, but this problem is mitigated to a large extent by measuring isotope ratios. If there is a significant isotopic fractionation between CAHs and derivative chlorine-bearing products, then the fraction of CAH that is dechlorinated can be inferred from the {sup 37}Cl/{sup 35}Cl and {sup 13}C/{sup 12}C isotope ratios of the residual CAH. It is important to point out that there is currently no published information available on the magnitude of chlorine and carbon isotopic fractionation associated with biological degradation of CAHs. The authors plan to help eliminate this important gap in the knowledge with the work being performed here. This work is relevant to EMSP goals because it will provide a new and cost-effective means of evaluating and monitoring the effectiveness of in-situ bioremediation. It will employ newly developed techniques to characterize isotopic fractionation (of chlorine and carbon) associated with biotic and abiotic degradation of CAHs in laboratory microcosms. These techniques and the data acquired by using them in laboratory studies will form the fundamental basis for quantitative assessment of the mechanisms, rates, and efficiencies of various in-situ bioremediation schemes for CAHs. This report summarizes work as of 21 months into a 36-month project. First, the author has developed methods for precise measurement of stable carbon and chlorine isotope ratios of micromolar amounts of CAHs. He has also developed methods for quantitative extraction of CAHs from water and air. He has applied these methods in laboratory experiments, to investigate isotopic fractionation caused by microbial degradation and by abiotic processes such as evaporation and chemical reduction. He has also applied these methods to field investigations of contaminated groundwater aquifers at the Paducah Gaseous Diffusion Plant, Kentucky and at several manufacturing plants in the Chicago and Kansas City metropolitan areas. Results of much of this work have already been incorporated into four manuscripts that have been published, accepted for publication, or are in review.
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Stable isotopic investigations of in-situ bioremediation of chlorinated organic solvents
Get PDFThe purpose of this project was to investigate the potential applications of stable isotope ratio measurements in characterization of the source terms, the transport, and the fate of chlorinated solvents in groundwater aquifers. The approach to this research was threefold: to develop methods for the sampling and isotopic analysis of chlorinated solvents in groundwaters; to perform laboratory experiments to measure equilibrium and kinetic isotope effects associated with biological and physical transformation processes of chlorinated solvents; and to perform field investigations at well-characterized, contaminated aquifer sites to demonstrate the applicability of the isotopic approach in real-world situations. New methods were developed for the extraction and isotopic analysis of chlorinated solvents in water samples. The new methods were applied to a series of laboratory experiments assessing the isotope effects associated with biological and physical transformation processes. The authors found that a large kinetic isotope effect was caused by microbial degradation of chlorinated solvents, under both aerobic and anaerobic conditions. The evaporation of chlorinated solvents also caused a large isotope effect, but in that case the carbon isotopic fractionation was in the reverse sense. Isotopic fractionation associated with adsorption and chemical exchange of chlorinated solvents was negligible. The authors performed field investigations at five present and former industrial sites undergoing various stages of remediation. These investigations were collaborative with Lockeed-Martin Energy Systems, Inc., and ENSR, Inc., the companies responsible for the remedial work at these sites. Application of the new sampling and analytical methods at these sites showed that stable isotopic measurements yield powerful insights into underground processes. In particular, they found positive evidence for in-situ microbial degradation of chlorinated solvents at all five sites, evidence for volatilization of chlorinated solvents at three sites, and evidence for multiple sources of chlorinated solvents at two sites. At a site where six-phase heating was applied, they found evidence for increased solubilization of pure phase chlorinated solvents during heating. The general conclusion of the field investigations is that stable isotope measurements should become an essential component in site characterization and remediation of sites contaminated with chlorinated solvents
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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Radionuclide mobility in the shallow portion of an active high-temperature geothermal system
No full textAccurate knowledge of the behavior of radionuclides in natural rock-water systems is crucial for the prediction of the consequences of failure of a high-level nuclear waste repository. Work in progress at Argonne National Laboratory involves the detailed geochemical analysis of rock, mineral, and water samples from shallow drill holes in a thermal area of Yellowstone National Park. This study is designed to provide data that will increase our understanding of the behavior of a group of radionuclides in an environment similar to that of the near field of a high-level nuclear waste repository
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