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Reduced sediments: A factor in the design of subsurface oxidant delivery systems

GROUNd WATER MONITORING ANd REMEdIATION 1996年第1期16卷 100-105页

作者： Korom, SF McFarland, MJ Sims, RC Scott E Korom received his B.S. and M.S. in civil engineering from the University of Akron in 1982 and 1984 respectively and his Ph.D. in civil and environmental engineering from Utah State University in 1991. Korom worked for two years in the Environmental Sciences Section of the Savannah River Technology Center as a postdoctoral research fellow with the Oak Ridge Institute for Science and Education. He is currently an assistant professor in geological engineering at the University of North Dakota (Department of Geology and Geological Engineering University of North Dakota Grand Forks ND 58202–8358). His research interests include ground water identification and ground water contaminant transport and remediation. Korom is a licensed professional engineer in North Dakota. Michael J. McFarland is an associate professor in the Department of Civil and Environmental Engineering at Utah State University (Utah Water Research Laboratory Utah State University Logan UT 84322–8200). Dr. McFarland received his B.S. degree in chemical engineering from Yale University and an M.S. in chemical engineering and a Ph. D. in agricultural engineering from Cornell University. Dr. McFarland has authored or coauthored more than 30 technical publications. He has served as a consulting engineer for both federal and local government agencies as well as private industry. Dr. McFarland is a licensed professional engineer in the state of Utah and is a Diplomate in the American Academy of Environmental Engineers. Ronald C. Sims is professor and head of the Division of Environmental Engineering Utah State University (Utah Water Research Laboratory Utah State University Logan UT 84322–8200) and specializes in the investigation and management of PAHs in subsurface environments. Dr. Sims received his Ph.D. in biological and agricultural engineering from North Carolina State University an M.S. in environmental engineering from Washington State University and an M.S. in environmental chemistry and biology from the University of North

A preliminary field performance evaluation of in situ bioremediation of a contaminated aquifer at the Libby, Montana, Superfund site, a former wood preserving site, was conducted for the Bioremediation Field Initiative sponsored by the U.S. environmental Protection Agency (U.S. EPA). The current approach for site remediation involves injecting oxygen and nutrients into the aquifer to stimulate microbial degradation of target compounds that include polycyclic aromatic hydrocarbons and pentachlorophenol. The preliminary field evaluation determined that, in addition to the oxygen demand associated with the microbial oxidation of the organic contamination, uncontaminated aquifer sediments at the site are naturally reduced and also exert a significant oxygen demand. This conclusion is supported by three types of information: (1) analyses of ground water samples: (2) results from a field-scale tracer test;and (3) results of laboratory evaluations of oxygen use by reduced aquifer sediment samples. An estimate of the cost of supplying hydrogen peroxide to satisfy the oxygen demand of the uncontaminated reduced sediments is provided to demonstrate that the additional cost of oxidizing the reduced sediments could be significant. The presence of naturally occurring reduced sediments at a contamination site should be considered in the design of subsurface oxidant delivery systems.

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The use of invertebrates in ground water monitoring: A rising research field

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GROUNd WATER MONITORING ANd REMEdIATION 1996年第2期16卷 103-113页

作者： Malard, F Plenet, S Gibert, J Florian Malard (Groundwater Hydrobiology and Ecology Laboratory University of Lyon I Bat. 403 43 Bd du 11 Nov. 1918 69622 Villeurbanne France) graduated from the Agricultural Engineering College of Dijon in 1989. He joined the Geography Department of Loughborough University of Technology in 1989 the Ecology Laboratory of the University of Dijon in 1991 the Hydrogeology Laboratory of the University of Montpellier in 1992 and the Groundwater Hydrobiology and Ecology Laboratory of the University of Lyon I in 1993. He received an M.Sc. degree and a Ph.D. in hydrobiology from the University of Lyon I in 1991 and 1995 respectively. His most recent work has been in the field of organic contamination of karstic aquifers as related to ground water invertebrates. Sandrine Plenet (Groundwater Hydrobiology and Ecology Laboratory University of Lyon I Bat. 403 43 Bd du 11 Nov. 1918 69 622 Villeurbanne France) received her Ph.D. in hydrobiology from the University of Lyon in 1993 where she is currently an assistant lecturer. Her research interest is the influence of environmental variables on the dynamics of invertebrate communities with special emphasis on the impact of contaminants such as heavy metals on interstitial invertebrate assemblages. From 1991 to 1993 her work involved the search for indicator species of ground water contamination within the framework of a French Water Agency environmental program. Janine Gibert (Groundwater Hydrobiology and Ecology Laboratory University of Lyon I Bat. 403 43 Bd du 11 Nov. 1918 69 622 Villeurbanne France) is a professor at the University of Lyon I. She is also head of the Freshwater and River Ecology Research Unit 1974 of the C.N.R.S. and head of the Groundwater Hydrobiology and Ecology Laboratory of the University of Lyon I. She is engaged in collaborative research projects on a wide range of issues exploring ground water ecology in the perspective of environmental sustainability. She is involved in international programs on the ecology and management of aquat

The use of invertebrates as biomonitors of ground water quality is a relatively new approach that has come of age with the development of ground water ecology. The benefits of such an approach are illustrated by four examples of field biomonitoring from several sites in various hydrogeological settings. Contamination of the interstitial zone by heavy metals in some sectors of the Rhone River (France) was shown by the scarcity of insect species;sewage pollution in the saturated zone of a karstic aquifer was indicated by the low relative abundances of stygobites as compared with those of stygophiles and stygoxenes;and enrichment with organic matter of an underflow was dearly demonstrated by the extremely high density of ground water invertebrates such as oligochaetes, ostracods, and isopods. Examination of the spatial changes in the composition and abundance of invertebrate assemblages was also useful in determining the direction and intensity of water fluxes between a river and its underflow, as well as in delineating the reduced or oxidized zones in a manganese-polluted aquifer. Finally, the selected case studies emphasized the variety of methodological approaches that could be developed in ground water contamination biomonitoring, as well as the complementary and sometimes new information provided by this innovative method in comparison with that obtained by conventional pollution monitoring techniques.

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Affordability, logistics R&d and fleet systems

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NAVAL ENGINEERS JOURNAL 1996年第3期108卷 199-213页

作者： Schulte, dP Skolnick, A He has supported the development and operation of several naval systems including advanced component selection for Trident II fire control and navigation systems. He served as branch manager of the Surface Ship ASW Combat System Branch which acted as the acquisition engineering agent for the AN/SQQ-89 Surface Ship Anti-Submarine Warfare Weapon System. He was then selected to manage the Module Engineering Department which provided engineering support to numerous naval systems including the AN/BSY-1 Submarine Combat System and the Trident II fire control and navigation system. He then served as the deputy program manager for NAVSEA Progressive Maintenance (2M/ATE). He holds a B.S. degree in Electrical Engineering from Purdue University and currently is pursuing a Maste's degree in Public Environmental Affairs at Indiana University—Purdue University Indianapolis. He served at Applied Physics Laboratory/The Johns Hopkins University in missile development then aboard USS Boston (CAG-1) and played leading roles in several weapon system developments (Regulus Terrier Tartar Talos) inertial navigation (Polaris) deep submergence (DSRV) and advanced ship designs (SES). He later was director Combat System Integration Naval Sea Systems Command and head Combat Projects Naval Ship Engineering Center. He led the Navy's High Energy Lasers and Directed Energy Weapons development efforts. He was vice president advanced technology at Operations Research Inc. and vice president maritime engineering at Defense Group Inc. before starting SSC in 1991. Dr. Skolnick holds a B.S. degree in Mathematics and Economics Queens College an M.A. degree in Mathematics and Philosophy Columbia University an M.S. degree in Electrical/Aeronautical Engineering U.S. Naval Postgraduate School and a Ph.D. in Electrical Engineering and Applied Mathematics from Polytechnic University in New York. He is the author of many published papers on engineering design issues source selection procedures and large-scale complex technology problems

The Fleet continues to require high performance systems that can operate with dependability in the seas' unforgiving environments and under hostile action. Those demands are not new. What has changed is the urgent priority formerly assigned to national defense issues. The arguments for continued superpower military strength are now roiled in politics along with unsettled budgets and uncertain force level projections. Current expectations revolve about indefinite fiscal and operational issues (difficult funding constraints and broadband threats). In the actual event of ''doing more with less,'' a practical response is to apply the creative power available from sound engineering judgement and the crucible of experience to the immediate needs of the Fleet. The attempt to shorten the path between advanced development effort and Fleet use has been tried occasionally in the past, often, without exemplary results. The Sustainable Hardware and Affordable Readiness Practices (SHARP) program, is a generic R&d effort under OpNav sponsorship that has been working steadily on sensible solutions to product engineering problems. Armed today with fast-time, large-scale computation abilities and modern tools for technical problem solving coupled with specialized engineering knowledge, it has been refreshed and is underway satisfying existing Fleet needs. The relationship between fully responsive engineering services and current operational needs is always demanding. The connection between advanced engineering development (6.3 category funds) and immediate Fleet usage brings added complexity and challenge, both technical and organizational. Illustrative examples of affordable engineering solutions to ''retain, revise, replace or retire'' questions are presented within the context of both Fleet realities and budgetary limitations. The discussion covers legacy system support, civil/military considerations and Fleet maintenance issues. It describes the substantial and critical payoffs i

关键词： Warships

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A RISK-BASEd APPROACH FOR MANAGING HAZARdOUS-WASTE

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GROUNd WATER MONITORING ANd REMEdIATION 1995年第1期15卷 79-89页

作者： CHIANG, CY PETKOVSKY, Pd MCALLISTER, PM Chen Y. Chiang received his Ph.D. in environmental engineering from Rice University. He is a senior research engineer in Environmental RD&T at Shell Development Co.'s Westhollow Technology Center (3333 Hwy. 6 South Houston TX 77082 fax (713) 544–8727). He serves on the Hydrologic Science Panel of the National Science Foundation and on the Ground Water/Soil Technical Task Force of the American Petroleum Institute. He also serves on the Advisory Board of the Rutgers DARPA/ONR research program. His research interests include in situ bioremediation processes ground water/soil sampling and monitoring multiphase fluid flow phenomenon and risk/ exposure assessment. Paul Petkovsky is a senior research technician in the Groundwater Modeling Group of Environmental RD&T at Shell Development Co.'s Westhollow Technology Center. His responsibilities include site data analysis and the numerical modeling of the fate and transport of organics in ground water. He is currently pursuing a B.S. in chemical engineering with an environmental emphasis at the University of Houston. Paul McAllister received a B.S. in chemical engineering from the University of Kansas in 1987 and a Ph.D. in chemical engineering from the University of Notre Dame in 1991. He is currently an associate research engineer in Environmental RD&T at Shell Development Co.'s Westhollow Technology Center. Since joining Shell he has conducted research and provided technical support on ground water modeling and remediation issues. His research interests include in situ bioremediation of ground water and residual hydrocarbons natural attenuation of contaminants and subsurface fate and transport phenomena in the subsurface.

In 1992, the U.S. environmental Protection Agency (EPA) proposed risk-based management of hazardous waste. A major component of the proposed rule is the determination of non-site-specific screening concentration levels from waste leachate. Ground water at a downgradient exposure point must not exceed those screening levels, or more stringent requirements would apply. The screening concentration level is determined with verified models and equations that simulate the transport and attenuation of chemicals as they travel from the source area to the exposure point. A consortium of screening levels is determined in this paper by considering varying physical, chemical, and biological conditions. In addition, a method is developed for multicomponent leaching from contaminated soils in a landfill to determine the time-dependent behavior of a finite source. Finally, this paper discusses infiltration rate through the clay liner.

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CHEMICAL MASS-BALANCE APPROACH TO FIELd-EVALUATION OF BIOREMEdIATION

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environmental PROGRESS 1995年第1期14卷 F2-F3页

作者： SIMS, RC SIMS, JL Utah State University Department of Civil and Environmental Engineering and Utah Water Research Laboratory Logan UT 84322 Professor and Head of the Division of Environmental Engineering at Utah State University. He holds degrees in biology (B.S.) environmental chemistry and biology (M.S.) environmental engineering (M.S.) and biological and agricultural engineering (Ph.D). He has worked as Director of the International Program in Industrial Development Chapel Hill NC as Supervisor of the Environmental Control Laboratory for Mobay Chemical Corporation Charleston SC and as environmental engineer with Research Triangle Institute NC. Dr. Sims currently is involved in teaching research and technology transfer in the area of contaminated soil characterization and remediation. Research Assistant Professor in the Division of Environmental Engineering at Utah State University. She holds degrees in biology (B.S.) environmental chemistry and biology (M.S.) and soil science (M.S.). She has held positions as an Associate in a private consulting firm in Raleigh NC and as Chairperson of the on-site wastewater disposal committee of the State of Utah. Judith Sims is currently involved in teaching research and technology transfer in the area of contaminated soil characterization and remediation.

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A dISTRIBUTEd MEdIA ACCESS PROTOCOL FOR PACKET RAdIO NETWORKS ANd PERFORMANCE ANALYSIS .2. NETWORK SET-UP TIME ANd dATA RATE

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international JOURNAL OF COMMUNICATION SYSTEMS 1995年第1期8卷 49-63页

作者： PONd, LC LI, VOK Communication Sciences Electrical Engineering Systems University of Southern California Los Angeles CA 90089-2565 U.S.A. Lawrence C. Pond received the M.Sc. and Ph.D. degrees in electrical engineering from the University of Southern California in 1983 and 1990 respectively. Dr. Pond is currently a scientist at Hughes Space and Communications Company having joined in 1980. He has worked in the fields of communication system design mobile communication network and spacecraft payload design. He is currently working on the development of satellite-based ATM transport and switching architectures for BISDN and Defense Information System Network amlications. Dr. Pond is a member of IEEE. Victor O. K. Li was born in Hong Kong in 1954. He received his SB SM and Sc.D. degrees in Electrical Engineering and Computer Science from the Massachusetts Institute of Technology Cambridge Massachusetts in 1977 1979 and 1981 respectively. Since February 1981 he has been with the University of Southern California (USC) LOS Angeles California where he is Professor of Electrical Engineering and Director of the USC Communication Sciences Institute. He has published 150 technical papers and has lectured and consulted extensively around the world. His research interests include high-speed communication networks personal communication networks intelligent networks distributed databases queueing theory graph theory and applied probability. Dr. Li is very active in the Institute of Electrical and Electronic Engineers (IEEE) having been a member of the Computer Communications Technical Committee since 1983 and having served as Chairman from 1987–1989. He served as Chairman of the Los Angeles Chapter of the IEEE Information Theory Group from 1983–1985. He is the Steering Committee Chair of the International Conference on Computer Communications and Networks (IC3 N) General Chair of the 1st Annual IC3N held in San Diego California in June 1992 General Chair and Technical Program Chair of the 4th IEEE Workshop on Comp

In this, the second part of a two-part paper, the required time for establishing a mobile packet radio network using the virtual circuit and time division multiple access protocol developed in Part 1 is analysed. Tools are developed to determine the virtual circuit and network set-up times in terms of the channel bandwidth allocated to establish and maintain the network. The tools are then extended to include the effects of user mobility. Then these results are combined with the network capacity results of Part 1 to analyse the trade-off between the data rate and set-up time of the network. Next a hierarchical architecture is proposed and the network data rate versus set-up time trade-off of this architecture is analysed using these tools. This architecture is shown to both provide a higher data rate and establish faster than flat networks of the same number of nodes.

关键词： PACKET RAdIO NETWORK EPLRS dISTRIBUTEd NETWORK TdMA VIRTUAL CIRCUITS MULTIHOP NETWORK BOUNdEd dELAY MOBILITY NETWORK SET-UP TIME HIERARCHICAL NETWORK NETWORK dATA RATE

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PERFORMANCE OF A PRIORITIZEd ON-BOARd BASEBANd SWITCH FOR A MULTISERVICE MULTIBEAM SATELLITE

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international JOURNAL OF SATELLITE COMMUNICATIONS 1994年第3期12卷 283-297页

作者： BOHM, S ELHAKEEM, AK HACHICHA, M Department of Electrical and Computer Engineering Concordia University 1455 De Maisonneuve Blvd. West Montreal H3A 1M8 Canada Was born in Montreal Canada on 14 September 1966. He received the B. Eng. degree in electrical engineering from Concordia University Montreal Canada in 1989. He is at present completing the M.A.Sc. degree in electrical engineering at Concordia University. (S'75–S'79–M'79–SM'86) received the Ph.D. degree from Southern Methodist University Dallas TX in 1979. He spent the next two years working as a Visiting Professor in Egypt after which he moved to Ottawa Canada in 1982. He assumed teaching and research positions in Carleton and Manitoba Univerities and later moved to Concordia University Montreal Canada in 1983 where he is now a Professor in the Electrical and Computer Engineering Department. He has published numerous papers in IEEE and international journals in the areas of spread spectrum and networking. He is a well-known expert in these areas and serves as a consultant to many companies. His current research interests include wide-band metropolitan networks switching architectures and performance of on-board multibeam satellites acquisitionless CDMA networks code distribution and orthogonalization of CDMA signals responsive congestion control for ATM-based networks ARQ techniques and investigation of the novel SUGAR CDMA systems in fading channels. Dr. Elhakeem is a Senior Member of the Canadian Electrical Engineering Society and Armed Forces Association. He has chaired numerous technical sessions in IEEE Conferences was the Technical Program Chairman for IEEE Montech 1986 Montreal Canada. Dr. Elhakeem is the key guest editor of theIEEE Journal of Selected Areas in Communicationsfor the May June issues 1993 covering CDMA networks. Advanced Technology & Networks VISTAR Telecommunications Inc. Ottawa Ontario K1G 3J4 Canada An Associate Director of Advanced Technology & Networks Group VISTAR Telecommunications Inc. Ottawa Canada. He is also an Adjunct Pr

In this paper, we study the performance of a prioritized on-board baseband switch in conjunction with a multibeam satellite handling integrated services. The services considered for the analysis include voice, video, file transfer and interactive data. The prioritized switch uses both input and output buffering, switch speed-up as well as a two-phase head-of-line resolution algorithm, in order to reduce the buffer loss while maintaining acceptable user delays. The minimum required buffer capacity and switch speed-up for each service in a prioritized environment are found under uniform traffic conditions. It is shown that under uniform traffic conditions, only minimal buffering and switch speed-up are needed even for the lowest priority users. The performance dependence on the switch size is also substantially reduced with head of line resolution and buffering even in a prioritized environment.

关键词： SWITCH ON-BOARd BASEBANd MULTIBEAM PRIORITIZEd HEAd-OF-LINE UNIFORM LOAd SPEEd-UP

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THE CALLING(SM) NETWORK - A GLOBAL WIRELESS COMMUNICATION-SYSTEM

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international JOURNAL OF SATELLITE COMMUNICATIONS 1994年第1期12卷 45-61页

作者： TUCK, EF PATTERSON, dP STUART, JR LAWRENCE, MH Calling Communications Corporation. 1900 West Garvey Ave South. Suite 200 West Covina CA 91790 USA. Chairman of Calling Communications Corporation. He is also the Managing Director of Kinship Venture Management Inc. the general partner of Kinship Partners 11 and a General Partner of Boundary the general partner of The Boundary Fund. As a venture capitalist he has founded or participated in founding several telecommunications companies including Calling Communications Corporation Magellan Systems Corporation manufactures of Global Positioning System receivers Applied Digital Access manufacturer of DS-3 test access and network performance monitoring equipment Endgate Technology Corporation specialists in satellite phased array antennas and Poynting Systems Corporation. now a division of Reliance Corporation manufacturers of fibre optic transport equipment. He was a founder of Kebby Microwave Corporation where he invented the first solid-state. frequency-modulated commercial microwave link system. The company was acquired by ITT Corporation where he rose to the position of V.P. and Technical Director of ITT North America Telecommunications Inc. Subsequently he was V.P. of Marketing and Engineering at American Telecommunications Inc. (ATC). He was founding Director of American Telecom Inc. a joint venture between ATC and Fujitsu and has served on more than 20 boards of directors including those of three public companies. He has authored articles on microwave engineering and telephone signalling and was a contributor to Reference Data For Radio Engineers. He is a graduate of the University of Missouri at Rolla where he was later awarded an honorary Professional degree and serves on its Academy of Electrical Engineering. Mr Tuck is a Senior Member of the IEEE a Fellow of the Institution of Engineers (Australia) a Professional Member of the AIAA and a registered professional engineer in three states. More than 25 years of experience in the telecommunications industry where he has been responsibl

There is a very large demand for basic telephone service in developing nations, and remote parts of industrialized nations, which cannot be met by conventional wireline and cellular systems. This is the world's largest unserved market. We describe a system which uses recent advances in active phased arrays, fast-packet switching technology, adaptive routeing, and light spacecraft technology, in part based on the work of the Jet Propulsion Laboratory and on recently-declassified work done on the Strategic defense Initiative, to make it possible to address this market with a global telephone network based on a large low-Earth-orbit constellation of identical satellites. A telephone utility can use such a network to provide the same modern basic and enhanced telephone services offered by telephone utilities in the urban centres of fully-industrialized nations. Economies of scale permit capital and operating costs per subscriber low enough to provide a service to all subscribers, regardless of location, at prices comparable to the same services in urban areas of industrialized nations, while generating operating profits great enough to attract the capital needed for its construction. The bandwidth needed to support the capacity needed to gain these economies of scale requires that the system use K(alpha)-band frequencies. This choice of frequencies places unusual constraints on the network design, and in particular forces the use of a large number of satellites. Global demand for basic and enhanced telephone service is great enough to support at least three networks of the size described herein. The volume of advanced components, and services such as launch services, required to construct and replace these networks is sufficient to propel certain industries to market leadership positions in the early 21st Century.

关键词： LOW EARTH ORBIT SATELLITE COMMUNICATIONS FAST PACKET SWITCHING EARTH FIXEd CELLS AdAPTIVE ROUTEING LIGHT SPACECRAFT K(A) BANd phASEd-ARRAY ANTENNAS

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SCIENTIFIC ANd TECHNOLOGICAL RESPONSES TO STRUCTURAL AdJUSTMENT - HUMAN-RESOURCES ANd RESEARCH ISSUES IN HUNGARY, TURKEY, ANd YUGOSLAVIA

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technology IN SOCIETY 1993年第3期15卷 281-299页

作者： WEISS, C [&lowast ]Dr. Charles Weiss Jr. is President of Global Technology Management Inc. an independent research firm specializing in science and technology and environmental policy in Eastern Europe and the developing world. He was the first Science and Technology Adviser to the World Bank and served in that capacity from 1971 through 1986. Dr. Weiss has been Adjunct Professor at the University of Pennsylvania and Visiting Lecturer at both the Woodrow Wilson School of Public and International Affairs (Princeton University) and the School of Advanced International Studies (The Johns Hopkins University). He received his B.A. in chemistry and physics summa cum laude and his Ph.D. in biochemistry and chemical physics from Harvard University.

Hungary, Yugoslavia, and Turkey once were inward-looking economies in which a lack of competition suppressed demand for improved technology. With the exception of the export-oriented portion of Hungarian industry, the investments in civilian science and technology in all three countries led to the development of enclaves of technological capacity that were largely cut off from the rest of the economy When Turkey emerged from this situation in the early 1980s, it expanded rapidly, a situation similar to that of present-day Malaysia or Thailand. A decade later, Turkey's private and public sectors are contemplating substantial investments to make up for lost time. Hungary and pre-civil-war Yugoslavia inherit from the previous regimes an extensive scientific and technological establishment with pockets of first-class performance that could become the basis of long-run competitive advantage. This capability will require careful management and major investments if it is to be sustained during the difficult transition to a competitive market economy.

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HYdROCARBON VAPOR dIFFUSION IN INTACT CORE SLEEVES

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GROUNd WATER MONITORING ANd REMEdIATION 1993年第1期13卷 139-150页

作者： OSTENdORF, dW MOYER, EE XIE, YF RAJAN, RV David W. Ostendorf (Civil Engineering Department University of Massachusetts Amherst MA 01003) is an associate professor in the Environmental Engineering Program of the Civil Engineering Department of the University of Massachusetts at Amherst. His research interests include unconfined aquifer contamination hazardous waste site remediation and analytical modeling of problems in environmental fluid mechanics. Ostendorf is a Registered Professional Engineer in Massachusetts and a member of the American Geophysical Union American Society of Civil Engineers Soil Science Society of America Water Pollution Control Federation and Association of Environmental Engineering Professors as well as the National Ground Water Association. Ellen E. Moyer (Civil Engineering Department University of Massachusetts Amherst MA 01003) is a doctoral candidate in the Environmental Engineering Program of the Civil Engineering Department of the University of Massachusetts at Amherst with an M.S. degree in environmental engineering from that institution. Her research interests include subsurface investigation soil venting bioremediation and analytical modeling of subsurface contamination. She has six years of professional experience managing hazardous waste site investigation and cleanup projects and is a member of the National Ground Water Association and the American Society of Civil Engineers. Yuefeng Xie (Civil Engineering Department University of Massachusetts Amherst MA 01003) is a postdoctoral research associate in the Environmental Engineering Program of the Civil Engineering Department of the University of Massachusetts at Amherst. His research interests include environmental analyses drinking water treatment and the chemical characterization and removal of disinfection by-products. A graduate with a Ph.D. and an M.S. in environmental engineering and a B.S. in chemistry and chemical engineeering from Tsinghua University Beijing China Xie is a member of the American Water Works Association and the Water Poll

The diffusion of 2,2,4-trimethylpentane (TMP) and 2,2,5-trimethylhexane (TMH) vapors out of residually contaminated sandy soil from the U.S. environmental Protection Agency (EPA) field research site at Traverse City, Michigan, was measured and modeled. The headspace of an intact core sleeve sample was swept with nitrogen gas to simulate the diffusive release of hydrocarbon vapors from residual aviation gasoline in and immediately above the capillary fringe to a soil-venting air flow in the unsaturated zone. The resulting steady-state profile was modeled using existing diffusivity and air porosity estimates in a balance of diffusive flux and a first order source term. The source strength, which was calibrated with the observed flux of 2,2,4-TMP leaving the sleeve, varied with the residual gasoline remaining in the core, but was independent of the headspace sweep flow rate. This finding suggested that lower soil-venting air flow rates were in principle as effective as higher air flow rates in venting LNAPL vapors from contaminated soils. The saturated vapor concentration ratio of 2,2,4-TMP to 2,2,5-TMH decreased from 6.6 to 3.5 over the duration of the experiments in an expression of distillation effects. The vertical profile model was tested against sample port data in four separate experiments for both species, yielding mean errors ranging from 0 to -24 percent in magnitude.

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