Susan E. Powers

Bio: Susan E. Powers is an academic researcher from Clarkson University. The author has contributed to research in topics: Literacy & Curriculum. The author has an hindex of 32, co-authored 92 publications receiving 3927 citations.

An experimental investigation of nonaqueous phase liquid dissolution in saturated subsurface systems: Transient mass transfer rates

Abstract: This work focuses on the experimental measurement and mathematical modeling of processes affecting the dissolution of nonaqueous phase liquids (NAPLs) entrapped in sandy porous media. Results of a series of laboratory-scale one-dimensional column dissolution experiments indicate that the length of time required to dissolve NAPLs and substantially reduce aqueous phase effluent concentrations is many times greater than predicted by equilibrium calculations. Experimental measurements clearly show an influence of both grain size and grain size distribution on the evolution of effluent concentrations. The longer cleaning times associated with coarse or graded media are attributed to the larger and more amorphous NAPL blobs associated with these media. A general correlation for transient dissolution rates is proposed which incorporates porous medium properties, Reynolds number, and volumetric fraction of NAPL. The model is calibrated with results from styrene dissolution experiments and is shown to adequately predict trichloroethylene dissolution rates in the same sandy media over the period of time required to dissolve the NAPL.

The water footprint of biofuels: a drink or drive issue?

Abstract: The water consumption and agrochemical use during biofuel production could adversely impact both availability and quality of a precious resource.

Theoretical Study of the Significance of Nonequilibrium Dissolution of Nonaqueous Phase Liquids in Subsurface Systems

Abstract: The objective of this work is to assess the potential significance of deviations from local equilibrium for the exchange of mass between residual nonaqueous phase liquids and the aqueous phase in the saturated groundwater zone. A one-dimensional convection-dispersion mass balance equation incorporating a first-order interphase mass transfer rate relationship and temporal changes in blob configuration is used to model this system. Analytical and numerical methods are employed to examine the steady state and transient behavior of the system under a variety of hypothetical aquifer conditions and pumping remediation schemes. Sensitivity of the model to several parameters including mass transfer coefficient, blob size and shape, and Darcy velocity is explored. Results of the theoretical assessment indicate that nonequilibrium effects could play a significant role in some contamination scenarios, primarily for large blob sizes and relatively high velocities. Design of soil flushing techniques will be impacted by these conclusions. Uncertainty in several parameter values used in this analysis indicate the need for further experimental investigation of this process.

The Transport and Fate of Ethanol and BTEX in Groundwater Contaminated by Gasohol

Abstract: Ethanol is used a component in all gasoline in Brazil, and its use could increase significantly in the U.S. to meet the requirements of the Clean Air Act Amendments. Recent problems with ground water contamination by methyl tert-butyl ether (MTBE) have made policymakers more cognizant of the need to consider the overall impact of gasoline oxygenates in the environment. Therefore, a thorough understanding of the impact of incorporating ethanol as a gasoline component on the fate and transport of gasoline releases is required. This article provides a comprehensive review of the transport of ethanol and monoaromatic hydrocarbons (BTEX) in the subsurface following a gasohol spill. Two mechanisms related to the presence of ethanol are generally considered to impact BTEX transport. Ethanol can increase the aqueous concentration of BTEX compounds due to a cosolvent effect, and it can inhibit BTEX biodegradation by preferentially consuming electron acceptors and nutrients. Our review illustrates that cosolvent ef...

经验与教育 = Experience and education

Abstract: Experience and Educationis the best concise statement on education ever published by John Dewey, the man acknowledged to be the pre-eminent educational theorist of the twentieth century. Written more than two decades after Democracy and Education(Dewey's most comprehensive statement of his position in educational philosophy), this book demonstrates how Dewey reformulated his ideas as a result of his intervening experience with the progressive schools and in the light of the criticisms his theories had received. Analysing both "traditional" and "progressive" education, Dr. Dewey here insists that neither the old nor the new education is adequate and that each is miseducative because neither of them applies the principles of a carefully developed philosophy of experience. Many pages of this volume illustrate Dr. Dewey's ideas for a philosophy of experience and its relation to education. He particularly urges that all teachers and educators looking for a new movement in education should think in terms of the deeped and larger issues of education rather than in terms of some divisive "ism" about education, even such an "ism" as "progressivism." His philosophy, here expressed in its most essential, most readable form, predicates an American educational system that respects all sources of experience, on that offers a true learning situation that is both historical and social, both orderly and dynamic.

Educational Research: Competencies for Analysis and Application:

Abstract: to many, however, it constantly appears as an instructional problem. The final two chapters serve as excellent summary statements. Chapter 13 emphasizes the application of previous text material to the classroom situation. Of great significance is the author's discussion of commonly defined independent, dependent, and moderator variables. The final chapter focuses on evaluation in the overall sense, particularly as it relates to programs of study. The principles of measurement and research design are applied to the evaluation process through several ex-

The Water Footprint Assessment Manual: Setting the Global Standard

Abstract: This manual presents a scientifically rigorous method to help companies understand their dependency and impact on global water resources, and offers guidance on response strategies that conserve water for industry, communities, and nature. It contains the global standard for water footprint assessment as developed and maintained by the Water Footprint Network. It covers a comprehensive set of definitions and methods for water footprint accounting. It shows how water footprints are calculated for individual processes and products, as well as for consumers, nations, and businesses. It also includes methods for water footprint sustainability assessment and a library of water footprint response options. The water footprint of a product is the volume of freshwater used to produce the product, measured over the fully supply chain. It is a multidimensional indicator, showing water consumption volumes by source and polluted volumes by type of pollution; all components of a total water footprint are specified geographically and temporally.

Beneficial Biofuels—The Food, Energy, and Environment Trilemma

Abstract: Recent analyses of the energy and greenhouse-gas performance of alternative biofuels have ignited a controversy that may be best resolved by applying two simple principles. In a world seeking solutions to its energy, environmental, and food challenges, society cannot afford to miss out on the global greenhouse-gas emission reductions and the local environmental and societal benefits when biofuels are done right. However, society also cannot accept the undesirable impacts of biofuels done wrong.