bluuebunny/crossref_metadata_2025 huggingface dataset:
Deriving oral assessment scales across different tests and rater groups
Authors: Chalhoub-Deville Micheline
Published: March 2008

The purpose of this study is to derive the criteria/dimensions underlying learners' L2 oral ability scores across three tests: an oral interview, a narration and a read-aloud. A stimulus tape of 18 speech samples was presented to three native speaker rater groups for evaluation. The rater groups included teachers of Arabic as a foreign language in the USA, nonteaching Arabs residing in the USA for at least one year and nonteaching Arabs living in their home country (Lebanon). Each of the raters provided a holistic score for every speech sample. Holistic scores were analysed using the INDSCAL multidimensional scaling model. Results showed that the nonmetric three-dimensional solution provided a good fit to the data. Both regression and speech sample analyses were employed to identify those dimensions. Additionally, subject weights indicated that the three rater groups were emphasizing the three dimensions differentially, thus demon strating that native speaker groups with varied backgrounds perceive the L2 oral construct differently. The study contends that researchers might need to reconsider employing generic component scales. A research approach that derives scales empirically according to the given tests and audiences, and according to the purpose of assessment, is recommended. Finally, replicating this study using other languages, L2 oral ability levels, tests and rater groups is suggested.
Rater characteristics and rater bias: implications for training
Authors: Lumley Tom , McNamara T.F.
Published: March 2008

Recent developments in multifaceted Rasch measurement (Linacre, 1989) have made possible new kinds of investigation of aspects (or 'facets') of performance assessments. Relevant characteristics of such facets (for exam ple, the relative harshness of individual raters, the relative difficulty of test tasks) are modelled and reflected in the resulting person ability measures.

In addition, bias analyses, that is interactions between elements of any facet, can also be analysed. (For the facet 'person', an element is an individual candidate; for the facet 'rater', an element is an individual judge, and so on.) This permits investigation of the way a particular aspect of the test situation (type of candidate, choice of prompt, etc.) may elicit a consistently biased pattern of responses from a rater.

The purpose of the research is to investigate the use of these analytical techniques in rater training for the speaking subtest of the Occupational English Test (OET), a specific-purpose ESL performance test for health professionals. The test involves a role-play based, profession-specific inter action, involving some degree of choice of role-play material. Data are presented from two rater training sessions separated by an 18-month interval and a subsequent operational test administration session. The analysis is used to establish 1) consistency of rater characteristics over different occasions; and 2) rater bias in relation to occasion of rating. The study thus addresses the question of the stability of rater characteristics, which has practical implications in terms of the accreditation of raters and the requirements of data analysis following test administration sessions. It also has research implications concerning the role of multifaceted Rasch measurement in understanding rater behaviour in performance assessment contexts.
Is C-testing superior to cloze?
Authors: Jafarpur Abdoljavad
Published: March 2008

Several recent studies have suggested C-testing to be a highly valid and reliable measure of general language proficiency avoiding the problems with cloze testing. This study investigates the feasibility of the procedure with native and non-native speakers of English. Results of 20 C-tests constructed with different ratio and/or deletion start are analysed and discussed. The findings of the study refute the claims on C-testing. The implications of the findings are also discussed.
Investigating variability in tasks and rater judgements in a performance test of foreign language speaking
Authors: Bachman Lyle F. , Lynch Brian K. , Mason Maureen
Published: March 2008

Much of the recent debate that has surrounded the development and use of 'performance', or 'communicative' language tests has focused on a supposed trade-off between two sets of desirable qualities: correspondence between test tasks and test performance to nontest language use for content relevance; and reliability of scores derived from test performance. One area that has been of particular concern with performance tests is the potential variability in tasks and rater judgements, and this has been investigated in the language testing literature with two complementary approaches: generalizability the ory and many faceted Rasch modelling. GENOVA, which performs general izability theory analyses, estimates the relative contribution of variation in test tasks and rater judgements to variation in test scores. FACETS, which performs many faceted Rasch modelling, estimates differences in task difficulty and rater severity, and adjusts ability estimates of test takers, taking these differences into account. In this article we first discuss the design and development of a foreign language (Spanish) test battery that was designed for two purposes: first, to place University of California Education Abroad students into programmes at universities abroad that are appropriate for their level of language ability, and secondly to provide diagnostic information that will be useful for designing appropriate teaching and learning pro grammes for prospective education abroad students. The test battery consists of four subtests: reading, listening and note-taking, speaking, and writing. All subtests share a common theme or topic, and are interdependent. We then discuss the results of the GENOVA and FACETS analyses of the speaking subtest, based on a full field trial with a group of University of California undergraduate students who had been selected for participation in the Education Abroad Program. Finally, we discuss the implications of these results for the use of G-theory and many faceted Rasch modelling for the development of performance tests of foreign language ability.
Styles of thinking and learning
Authors: Sternberg Robert J.
Published: March 2008

Styles of thinking and learning are relevant for understanding foreign- language aptitude and for testing this aptitude. Such styles are preferred modes of thinking, of using one's abilities. This article emphasizes one particular theory of styles, the theory of mental self-government. First, the article describes what styles are. Secondly, it discusses the nature of styles in more detail. Thirdly, it gives some history of the concept of styles. Fourthly, it motivates the theory of mental self-government. Then it describes each of the styles in the theory. Fifthly, it describes measures of styles. Sixthly, it describes data we have collected on styles. Finally, it discusses the relevance of styles for assessing foreign-language aptitude.
Test theory and language-learning assessment
Authors: Mislevy Robert J.
Published: March 2008

Standard test theory is machinery for carrying out inference in a particular admixture of ideas from statistics, measurement and psychology that coa lesced in the first third of this century. Recent developments in cognitive and educational psychology, such as increased appreciation of the situated nature of learning and understanding, call for broader ranges of student models and types of data. Just as under the standard testing paradigm, however, we face such questions as: what kinds of evidence are needed to support inferences about students? How much faith can we place in the evidence, and in the statements? Are elements of evidence overlapping, redundant or contra dictory ? When must we ask different questions or pose additional situations to distinguish among competing explanations of what we see? A con ceptualization of test theory is discussed which is meant to address issues of weight and coverage of evidence for statements framed in more recent educational/psychological paradigms. Implications for language assessments built around the ACTFL guidelines are considered.
Language testing and the assessment of dementia in second language settings: a case study
Authors: Baker Rosemary
Published: March 2008

Procedures commonly used for assessing cognitive function in people with suspected dementia are of questionable validity in second language settings because of possible linguistic and cultural inappropriateness. This article reports a case study of a patient of Japanese background with suspected dementia in an English-speaking geriatric unit. The subject was thought to be able to understand and speak English sufficiently well for her daily activities, but was not engaging in communication with hospital staff. The case was further complicated by a history of schizophrenia. As part of a research project concerned with language disorder in speakers of English as a second language, the subject was tested using tasks selected on the basis of current knowledge regarding language decline and deficit in dementia of the Alzheimer type (DAT). The tasks, which the subject wished to do only in Japanese, included naming, story recall and processing by semantic category. The subject's performance in her first language did not, in general, indicate her language-processing abilities to be compromised by DAT. The results demonstrate the potential contribution of information from language-based tasks administered in the person's preferred language to screening for dementia in second language settings.
Accounting for nonsystematic error in performance ratings
Authors: Henning Grant
Published: March 2008

This analysis of simulated performance ratings on a six-point scale by two independent raters is an attempt to account for nonsystematic error in performance ratings under restrictive assumptions of classical measurement theory. Results suggest that rater agreement or covariance is not always a dependable estimate of score reliability, and that the practice of seeking additional raters for the adjudication of discrepant ratings is not equally appropriate in every evaluation decision context or at every possible rating score step. And, although nonsystematic rating error is most common at the midpoints of the rating scale, most of this midpoint error disappears when rater scores are averaged, so that the need for adjudication is most critical at the rating scale extremes, whether or not raters are in agreement.
Examining validity in a performance test: the listening summary translation exam (LSTE) - Spanish version
Authors: Lee Scott Mary , Stansfield Charles W. , Kenyon Dorry Mann
Published: March 2008

This article reports on a project undertaken by the Center for Applied Linguistics (CAL) to develop and validate a criterion-referenced perform ance test of listening summary translation ability for the Federal Bureau of Investigation (FBI).1 The listening summary translation exam (LSTE- Spanish version) is designed to assess ability to comprehend and summarize in written English recorded conversations spoken in Spanish. The language and topics of these conversations are intended to be representative of the conversations which the FBI routinely monitors.

Bachman (1991) mentions two fundamental requirements for ensuring the validity of effective language testing procedures. First, the language abilities measured by the test must correspond to those abilities needed to carry out tasks in the target-language use situation. Secondly, features of the test tasks, or test method characteristics, must correspond to critical features of target- language use tasks. Bachman (1990; 1991) has suggested that the degree to which a language test meets these requirements can be assessed by evaluating the situational and interactional authenticity of the test tasks.

Although the Bachman framework was not available to us at the time we developed this test (1988-89), we employ the framework here to present the test and to provide evidence of its validity. Evidence of the situational and interactional authenticity of the LSTE-Spanish is offered, as well as for convergent/divergent validity through comparisons of correlations with cri terion measures.
Interlocutor support in oral proficiency interviews: the case of CASE
Authors: Lazaraton Anne
Published: March 2008

Despite a considerable amount of research on oral proficiency testing over the last 20 years, little is understood about the interview process itself and the spoken interaction that takes place in it. This article presents a qualitative analysis of one aspect of interviewer-candidate interaction, namely, the types of linguistic and interactional support that the native speaker interlocutor provides to the non-native speaker candidate in a one-on-one interview. Results indicate that eight types of interlocutor support are prevalent in the corpus of 58 transcribed Cambridge Assessment of Spoken English (CASE) interviews studied. It is suggested that these are positive findings in the sense that documented conversational practices are present in this assessment context; there is also reason for concern since the effect of such support on outcome ratings of proficiency remains unclear.
A comparison of recall and summary protocols as measures of second language reading comprehension
Authors: Riley Gail L. , Lee James F.
Published: March 2008

The purpose of this study was to examine the effect of test method on the reading performance of two levels of early-stage L2 readers of French. L2 reading research examining test methods has focused primarily on discrete- point modes of response. This study compared two global response modes, the summary and the recall protocol. Half of the 80 subjects were asked to read a passage and to write a summary of the passage and the other half were asked to read the passage and to recall it. The written protocols were analysed for total number of idea units as well as the number of main ideas, supporting ideas and details. The total number of idea units was submitted to a two-way analysis of variance. The three levels of idea units were submitted to separate two-way analyses of variance. Results indicate a significant qualitative difference in the performance on the two tasks. The summaries contained significantly more main ideas than the recall protocols. Fur thermore, the summaries contained a higher percentage of main ideas than details whereas the recall protocols contained a higher percentage of details than main ideas. The results have research and pedagogical implications.
A text-driven method for the deletion procedure in cloze passages
Authors: Farhady H. , Keramati M.N.
Published: March 2008

This article proposes a text-driven method for the deletion procedure in cloze passages. Contrary to the previous methods, the deletion rate suggested in this study is based on the number of the linguistic and discourse structures of a passage. After determining the proficiency level of the subjects, a passage of appropriate length and difficulty with the deletion rate of 7 was developed. Along with this standard cloze, eight different versions were also constructed. The deletion rate of the eight versions was based on the number of linguistic and discourse clues. Following a counterbalanced design, the cloze test forms were administered to 403 subjects majoring in English at different academic levels. The results sug gested that the text-driven method is superior to the fixed-ratio deletion method on some grounds. It was also revealed that the differences among the subjects' performance on different versions of cloze tests were significant. It is concluded that the random deletion method may lead to a paradox between the difficulty and the reliability of cloze tests.
Test impact revisited: washback effect over time
Authors: Shohamy Elana , Donitsa-Schmidt Smadar , Ferman Irit
Published: March 2008

In countries with centralized educational systems national tests are used as primary devices through which changes in the educational system are introduced. This article examines the impact over time of two national tests which have been in operation for a number of years: one in Arabic as a second language (ASL) and one in English as a foreign language (EFL) through questionnaires, interviews and document analysis from a sample of teachers, students and language inspectors. Results showed different washback patterns for the two tests. Slight modifications in the ASL test created no effect in classroom activities, test preparation, or the status and prestige of the subject tested, yet, the inspectors expressed satisfaction and wished to continue the administration of the test as they feared that without the tests proficiency levels would drop. Slight modifications in the EFL test, on the other hand, created major impact in terms of teaching activities, time devoted for test preparation, production of new teaching material, etc. Although negative attitudes were expressed by teachers regarding the quality of the test, they would like it to continue. Inspectors believe that the test creates a meaningful change and is powerful enough to trigger changes without a need to provide training and a new curriculum. The study shows that washback varies over time, owing to many factors such as the status of the language and the uses of the test.
Does grammar translation come from the entrance examination? Preliminary findings from classroom-based research
Authors: Watanabe Yoshinori
Published: March 2008

It is often argued that the Japanese university entrance examinations dominate the whole educational process, including the practice of EFL. However, this type of argument has rarely been tested empirically. This research attempts to cast some light on this issue, with special reference to the relationship between university entrance examinations and the use of the grammar-translation approach to teaching in the years leading up to the examination. Classroom observations indicate that teacher factors, such as educational background, personal beliefs and teaching experience may outweigh the possible effect of the entrance examinations. The article concludes with several suggestions for future research.
An English language placement test: issues in reliability and validity
Authors: Fulcher Glenn
Published: March 2008

This report describes a reliability and validity study of the placement test which is used at the University of Surrey as a means of identifying students who may require English language support whilst studying at undergraduate or postgraduate levels. The English Language Institute is charged with testing all incoming stu dents, irrespective of their primary language or subject specialization. Fair and accurate assessment of student abilities, and referring individuals to appropriate language support courses (the in-sessional programme), is an essential support service to all academic departments. The goal of placement testing is to reduce to an absolute minimum the number of students who may face problems or even fail their academic degrees because of poor language ability or study skills. This study looks at the administrative and logistic constraints upon what can be done, and assesses the usefulness of the placement test developed within this context.
Examining the test-taking process: a cognitive perspective on the discourse cloze test
Authors: Storey Peter
Published: March 2008

Testing consists of making a generalization about a population on the basis of what can be observed in a sample. This principle underlies not only the composition of the sample of individuals to be tested but also the selection of content for the testing instrument itself. Careful attention to the content of assessment tasks is needed to ensure that they are representative of the domain of tasks about which generalizations are to be drawn. However, content representativeness extends beyond mere attention to the problems posed and materials provided in the test. What is more crucially important is the manner in which test tasks are performed. Attention to test-taking process is especially crucial and problematic in the testing of cognitive processing skills. The sample will only be representative if the cogni tive processes involved in task performance are representative of those involved in performance of the domain of tasks in the real world. Thus the validation of tests involving cognitive processes will not be complete unless it includes some examination of the processes by which solutions to test tasks are reached. This line of thinking was propounded 40 years ago by Lennon but has only recently been taken up with the application of ethnographic methods to the study of the test-taking process.

This article looks at the findings of a study of the processes employed by sub jects engaged in a discourse cloze test. Think-aloud protocols obtained from test- takers give indications of the reasoning employed in selecting items to complete gaps in the cloze passage and of the strategies employed in doing so. From these indications, cognitive processes are inferred. Comparing observed behaviours and inferred processes with those predicted in a model of ideal performance gives a measure of the construct validity both of the items and of the discourse cloze procedure in general. This introspective validation procedure reveals the test-tak ing behaviour of subjects engaged in cloze tasks and provides a cognitive perspec tive on the vexed question of what cloze actually measures.
Book reviews: Street-Perrott, A., Beran, M. and Ratcliffe, R. 1983: Variations in the global water budget. Dordrecht: D. Reidel. xiv + 518 pp. US $69.50, Dfl. 160
Authors: Dury G.H.
Published: March 2008

Gregory, K.J. editor, 1983: Background to palaeohydrology. Chichester: John Wiley.
Short-term climatic change: evidence, causes, environmental consequences and strategies for action
Authors: Thompson Russell D.
Published: March 2008

The last two decades have been dominated by extreme weather events worldwide, which are generally regarded as good indicators of distinctive climatic change. This paper examines the evidence for short-term climatic change provided by atmospheric observations and environmental indicators over the past century or so and accounts for this change in terms of current (if conflicting) theories, particularly those associated with dust veils, the greenhouse effect and ozone depletion. It also discusses the predicted impact of these changes on a wide range of environmental factors, including sea level, agriculture and human health. It concludes with an analysis of a number of strategies for action which are required urgently to minimize the severity of the predicted impact.
Landforms and ground ice as evidence of the source of H2O in permafrost
Authors: Harris Stuart A.
Published: March 2008

Selected landforms and the ice in permafrost may be used as indicators of the direction of moisture input into perennially frozen ground. Accumulation of ice from meteoric sources from above may be the most widespread process, being dominant in the palsas, peat plateaus, and near-slope rock glaciers studied so far. It is also the main source of ice accumulation in permafrost. Pingos and seasonal frost mounds are the result of injection of ground water from below. The resulting ice content usually exceeds 90% by volume and some massive icy beds in Arctic Canada may also form in this way. Glacial ice is also proven as a source for some massive icy beds and may represent an Arctic form of ice stagnation. Segregation of ice by water moving to the freezing plane is very important in active layer processes and the initial formation of peat plateaus and palsas, but is probably of secondary importance thereafter. More work is needed to confirm these relationships and to prove the origin of near-glacier rock glaciers. However, if these relationships prove reliable, then the landforms can be used as indicators of potential sources of ice so that foundation designs can be modified to minimize heaving problems.
Linear dunes - forms and formation
Authors: Tsoar H.
Published: March 2008

Most geomorphologists and geologists do not differentiate the various types of linear dune and refer to them as one dune type mainly in the terms of linear, longitudinal or seif dunes. In recent morphodynamic and genetic classifications of dunes, all types of linear dunes are lumped under the heading of longitudinal dunes (Wasson and Hyde, 1983; Hunter et al., 1983). This review, however, substantiates three different simple linear dunes - lee dunes, seifs and vegetated- linear - each of which has a different shape and mechanism of formation and elongation.
Coastally trapped disturbances in the lower atmosphere: dynamic commonalities and geographic diversity
Authors: Reason C.J.C. , Steyn D.G.
Published: March 2008

The dynamics of coastally trapped disturbances in the lower atmosphere are considered. These disturbances are trapped by the existence of a subsidence inversion at a height below the crests of barrier-like coastal mountains and propagate alongshore with the coast on the right (left) in the Northern (Southern) Hemisphere. Favourable areas on the Earth for the existence of the disturbances are California, southeastern Australia and southern Africa. It is shown that the fundamental dynamics of the disturbances is in each case governed by the hydrostatic and semigeostrophic approximations. The latter implies that a geostrophic balance exists between the alongshore velocity of the motion and the across-shore pressure gradient. Although the fundamental dynamics are identical, it is shown that regional differences in forcing and boundary conditions lead to the observed diversity in the manifestation of the disturbances in each area. These differences include variations in the width of the coastal mountains, the strength and height of the inversion, in the scale of the forcing and whether this forcing leads to on- or offshore flow in the generation region of the disturbance.
Pans
Authors: Goudie A.S.
Published: March 2008

Closed desert depressions, called pans, have an extensive distribution in the world's dry lands, particularly on certain types of susceptible surface, which include shales, fine-grained sandstones and unconsolidated materials. They also occur in certain characteristic geomorphological situations, including interdunal areas, old river channels, and deflated lake beds. Pans often, but not invariably, have lunette dunes on their lee sides. Aridity is an important predisposing factor for pan development, and permits deflation, salt weathering, and disruption of drainage systems, all of which contribute to pan formation. Large numbers of hypotheses for pan development have been proposed, including animal activities and solution, but all these can be incorporated in a general model of pan development.
Holocene palynology: I principles, population and community ecology, palaeoclimatology
Authors: MacDonald Glen M. , Edwards Kevin J.
Published: March 2008

The latter half of the past decade witnessed important progress in elucidating the principles of fossil pollen analysis and in the application of palynology to the study of palaeoecology and palaeoclimatology. Areas with particularly notable efforts include: 1) the theoretical consideration of the spatial representation of fossil pollen records and the relationships of pollen proportions to the abundance of contributing plant populations; 2) the quest for palynological data with increasingly fine temporal and spatial resolution; 3) the development of large databases of modern and fossil pollen data for macroscale palaeoecological and palaeoclimatic studies; 4) the application of palynology to questions of plant population biology, most notably the study of plant invasion and implications for invading and pre-existing plant populations; 5) the demonstration of the relatively ephemeral nature of major vegetation types; 6) the refinement and development of techniques for providing quantitative estimates of past climate and testing climate reconstructions. Despite this progress important uncertainties remain regarding the relationship between plant abundance and pollen representation and the nature of climate-vegetation relationships, particularly at the meso- and microscales. Resolution of these questions is particularly important for plant population and climatic studies based on fossil pollen data.
Gas Enhancement Techniques in Landfill Simulators
Authors: Kinman Riley N. , Nutini David L. , Walsh James J. , Vogt W. Gregory , Stamm James , Rickabaugh Jannet
Published: March 2008

Techniques to enhance landfill gas production from landfills were tested using 16 landfill simulators. These techniques included: accelerated moisture infiltration; elevated moisture content; leachate recycle; buffer (calcium carbonate), nutrient (ammonium phosphate), and/or sewage sludge additions; and elevated refuse temperature. Each test cell contained 380 kg (836 1b) of ground municipal solid waste. All simulators were constructed in February 1980. Reloading of some of the cells with the nutrient (ammonium phosphate), buffer (sodium carbonate) or anaerobic sewage sludge took place in January 1983. The simulators were operated until January 1985. Over this operating period, various physical and chemical parameters were measured to determine gas and leachate quantity and quality. Results indicated that sewage sludge additions, buffer additions, and nutrient additions were useful enhancement techniques of gas production from municipal solid waste. Moisture infiltration and elevated moisture content have shown some beneficial effects.
Bentonite Liners for Isolation of Waste Disposal Sites
Authors: Hoeks J. , Glas H. , Hofkamp J. , Ryhiner A.H.
Published: March 2008

The applicability of bentonite as a lining material for isolation of waste disposal sites was investigated on laboratory and field scale. The permeability of sand-bentonite mixtures depends on the type of bentonite, the bentonite content in the mixture and the dry bulk density. In laboratory experiments the saturated conductivity decreased at low hydraulic head gradients, indicating that water flow in these mixtures does not obey Darcy's law. The swelling of the bentonite, which is responsible for the low permeability, is a time-dependent process. The permeability decreased with time and even after two months the permeability had not reached a constant level. In sand-bentonite mixtures with 5% (w/w) bentonite, the saturated conductivity ultimately reached a level below 1 x 10-10 m s-1, which is sufficiently low for surface capping of waste disposal sites. The sand-bentonite mixtures were 10-100 times more permeable for landfill leachate than for clean water. Bottom liners should, therefore, contain considerably more bentonite to prevent infiltration of leachate in the subsoil. Water-balance studies on experimental fields showed that there was no leakage at all through bentonite liners used for surface capping of a waste disposal site over a two-year period.
Heating Value of Municipal Solid Waste
Authors: Finet C.
Published: March 2008

This paper describes the processes that are used to calculate the heating value of municipal solid waste in France. The calculation can be done either by using the thermal-balance method of a furnace or a furnace-boiler unit, or by sorting the refuse and calculating the heating value of the homogeneous components. Both methods are described in this paper. The first method measures the heating value of the refuse that is injected into the furnace; the furnace becomes a calorimeter in which thermal balance is achieved on measuring the input and output heats. The second method consists of sorting a 100 kg refuse sample into piles that are as homogeneous as possible so that it can be considered as unchanging. The heating value is determined for each component and the lower heating value of the whole sample is calculated. The advantages and drawbacks of both methods are discussed.
Assessment of Non-Regulated Hazardous Wastes in the Seattle Area
Authors: Savage George M. , Sharpe Henry
Published: March 2008

The results of a quantitative study to assess the extent and degree of non-regulated hazardous waste present in municipal solid waste generated in King County, Washington State, U.S.A., are reported. A major objective of the study was to ascertain the health and environmental impacts of non-regulated hazardous waste within the County's collection, transport, and disposal systems and to formulate policies for managing non-regulated hazardous waste within the context of the County's solid waste management master plan. The study sampled municipal waste disposed at seven transfer stations in the County for the purpose of identifying the types and concentrations of non-regulated hazardous waste. Subsequent to the field sampling work and the conduct of the laboratory analyses, a risk assessment was performed to determine the types and degree of risk associated with the levels of non-regulated hazardous waste found in the waste stream. The assessment included the areas of occupational health and safety, of public health, and of environmental impact.
Applications of Risk Assessment Techniques To Hazardous Waste Management
Authors: Scott Michael P.
Published: March 2008

Applications of risk assessment techniques to hazardous waste management are brief ly discussed in terms of selecting appropriate waste management technologies, assessing operating sites, setting priorities for clean up of problem sites, determining the appropriate level of clean up and planning new facilities. A specific case history involving risk assessment for the siting of a waste management facility in the Province of Ontario, Canada is described in more detail. Risk estimates are provided for exposure via inhalation and ingestion of potentially contaminated local water, crops, meat and milk. The predicted risk are compared to risks of death from selected voluntary and involuntary exposures.
PCDD and PCDF Emissions and Possible Health Effects: Report On a Who Working Group
Authors: Suess Michael J.
Published: March 2008

An international group of experts, convened by the WHO Regional Office for Europe, discussed the health risks of PCDD and PCDF emissions from the incineration of municipal sewage sludge (MSS) and municipal solid waste (MSW) at a meeting in Naples, Italy, held 17-21 March 1986. A detailed analysis of emission data has shown that old and badly operated incinerators will emit up to many thousand ng Nm -3 of PCDD and PCDF, while most modern, highly controlled and carefully operated plants will emit them at a very low level. It is still not known what contribution municipal incinerator emissions make to the overall environmental load and, consequently, human exposure. For modern incineration plants this contribution was estimated to be in the range of about a tenth to a few percent of the total background daily body burden [assumed to be 1-5 pg of 2,3,7,8-TCDD (dioxin) equivalents per kilogram bodyweight and day]. The Working Group nevertheless recommended that efforts should be made to reduce further the PCDD and PCDF emissions from municipal incinerators.
Recent Findings On the Formation and Decomposition of PCDD/PCDF in Municipal Solid Waste Incineration
Authors: Vogg H. , Metzger M. , Stieglitz L.
Published: March 2008

The thermal formation of PCDD/PCDF in fly ashes of refuse incineration plants preferably in the low-temperature region of the boiler at 300°C is fully confirmed. Important parameters for the reaction of formation are the oxygen content and the water vapor in the offgas. Elemental carbon in the fly ash acts as an adsorbent to the precursor compounds. The oxidation of carbon may serve as a basis for the mechanism of PCDD/PCDF formation. Both reactions proceed by the Deacon process scheme. The catalytic action of CuCl2 can be counteracted by the addition of NH3.
Validation of Sampling and Analysis of Dioxins
Authors: Rappe Christoffer , Marklund Stellan , Tysklind Mats
Published: March 2008

During 1985 and 1986 the PCDD and PCDF emissions from MSW incinerators have been carefully studied in Sweden. The use of 13C-labelled compounds shows that sampling and analysis should be validated by the use of such compounds. Corrections should be made for losses during sampling and analysis. Isomer-specific analytical methods should be used. Minor differences were found in isomeric patterns and congener profiles between different incinerators. Emission levels were found to vary greatly.
The Origin and Health Risks of PCDD and PCDF
Authors: Commoner Barry , Shapiro Karen , Webster Thomas
Published: March 2008

PCDD/PCDF are ubiquitous in the emissions of trash-burning incinerators. They are synthesized in the cooler parts of the incinerator, and emissions are not reduced by controlling combustion conditions. Estimates of maximum lifetime risks of PCDD/ PCDF emissions range over two orders of magnitude from a minimum of one per million. This risk is greater than that which has triggered regulatory procedures against airborne carcinogens by U.S. EPA. Computations based on PCDD/PCDF in adipose tissue of a representative sample of the U.S. population indicate a national lifetime cancer risk of 330-1400 per million depending on the choice of equivalence methodology. In comparison, U.S. EPA has regulated environmental exposure to benzene based on a national lifetime cancer risk of 71.4. Because waste-burning incinerators contribute significantly to this risk, it is the authors' opinion that their PCDD/PCDF emissions should be reduced if U.S. EPA is to be consistent in its regulatory practice.
Crack Formation in Soil Landfill Covers Due To Thermal Contraction
Authors: Andersland Orlando B. , Al-Moussawi Hassan M.
Published: March 2008

Soil landfill covers in the northern United States experience ground freezing to depths of 2 m or more. During periods of decreasing winter temperatures, thermal contraction will increase tensile stresses creating the potential for crack formation. If elastic soil behaviour is assumed, a drop of only 2 or 3°C will generate significant tensile stresses. Climatological data examined for three locations, along with computed ground temperatures, show larger drops in temperature. Frozen cover soils are comparatively weak in tension. Cracks, once initiated, can propagate unstably through the frozen soil, and may extend deeper than the tensile stresses to which they owe their growth. Simple elastic soil behaviour used with thermal strains does not provide adequate information for predicting thermal contraction and crack formation. Information is needed on the thermal contraction behaviour of frozen soils, on the extent to which soil creep will reduce the tensile stresses, and on criteria suitable for preventing crack formation.
Natural Attenuation Mechanisms of Landfill Leachate and Effects of Various Factors On the Mechanisms
Authors: Bagchi Amalendu
Published: March 2008

The paper identifies mechanisms by which landfill leachate is attenuated by soil and aquifer. The mechanisms are: adsorption, biological action, cation and anion exchange reactions, dilution, filtration, and precipitation reactions. Each mechanism is discussed separately. The major attenuation mechanism is identified for many municipal landfill leachate constituents. Effects of leachate velocity, degree of saturation, organic and inorganic matter in soil, clay type, soil fabric and soil stratigraphy on attenuation is discussed.
The Mountain View Controlled Landfill Project Field Experiment
Authors: Haivadakis C.P. , Findikakis A.N. , Papelis C. , Leckie J.O.
Published: March 2008

The Mountain View controlled landfill project was undertaken in response to the need to optimize energy recovery from landfills, accelerate stabilization, and control gas migration and explosion hazards in the vicinity of landfills. The major objectives of the project were (1) to test the hypothesis that both yield and rate of landfill methanogenesis can be increased by controlling specific conditions within a landfill bioreactor, and (2) to quantify landfill gas production in a field-scale experiment with complete gas recovery so that a measure of landfill gas recovery efficiency can be established. Of particular importance for the design of the field experiment were the synergistic effects of moisture content, seed, and buffer additions on methanogenesis in landfilled municipal solid wastes. The experiment included six landfill cells considered as representative of actual landfills. The effect of moisture content, seed, and buffer was studied in terms of the water content of the refuse additions mixture on a total weight basis, the ratio of organic sludge dry solids to refuse dry solid (seed/nutrient), and the ratio of buffer solids to water present in the refuse/additions mixture.
Modelling Gas Production in Managed Sanitary Landfills
Authors: Findikakis A.N. , Papelis C. , Halvadakis C.P. , Leckie J.O.
Published: March 2008

Gas production and recovery from managed sanitary landfills can be simulated by describing the time and space variation of the total pressure and composition of the mixture of gases (CH4, CO2, and N2) in the landfill. The variation of the total pressure and the composition of the gas mixture is described by the equations for mass conservation for each component (including a generation term for CH4 and CO2), the equation of motion, and the equation of state. Simulations of gas production compare well with field data from the Mountain View controlled landfill project field experiment. The function used to approximate the shape of the methanogenesis curve (based on equations describing the biochemical processes) consists of a rising hyperbolic branch and a decaying exponential branch. The conceptual framework of the model has been designed to incorporate equations describing the physics, biology, and chemistry of gas production in landfills.
Effect of Landfill Leachate Spraying On Soil Respiration and Microbial Biomass in a Northern Hardwood Forest Ecosystem
Authors: Gordon Andrew M. , McBride Raymond A. , Fisken Avril J. , Voroney R. Paul
Published: March 2008

The effect of municipal solid waste (MSW) landfill leachate application upon soil respiration and microbial biomass was investigated in a northern hardwood forest of sugar maple (Acer saccharum Marsh.) and beech (Fagus grandifolia Ehrh.). One-way analysis of variance and multiple range testing of soil respiration estimates indicated that the lightly sprayed area had significantly higher respiration rates than the unsprayed control. Soil respiration in the heavily sprayed area did not differ from the lightly sprayed area or the control. The application of landfill leachate had a negative effect on the total microbial biomass present in the soil. Microbial biomass decreased significantly in those areas which were spray-irrigated in comparison to those which were not, with the areas receiving the highest application yielding the lowest biomass-carbon estimates. Also notable was a decrease in microbial biomass with increasing soil depth and with time during the latter part of the season.
Emission of Mutagenic Substances From Waste Incineration Plants
Authors: Victorin Katarina , StÅhlberg Margareta , Ahlborg Ulf G.
Published: March 2008

Combined filter-, condensate- and XAD-extracts of flue gas samples from four different municipal solid waste (MSW) incineration plants were tested for mutagenic activity in the Ames Salmonella/microsome assay. The mutagenic activity in samples from two of the incinerators was relatively high, whereas the emission from the other two was in the same order of magnitude as from oil- or coal-fired plants of equivalent size. Generally, the material collected did not require metabolic activation for mutagenic activity. The emission of mutagenic substances was statistically correlated to the emission of carbon monoxide and polyaromatic hydrocarbons (PAH). Thus, the amount of mutagenic material can be modulated by the combustion process. Fractionation studies showed that there is not only a quantitative but also a qualitative difference in mutagenic activity between samples representing different combustion conditions.
Laboratory Evaluation of Slurry Wall Materials of Construction To Prevent Contamination of Groundwater From Organic Constituents
Authors: Davis Ken E.
Published: March 2008

The installation of earthen liners and slurry wall trenches constructed of soils treated with bentonite and/or bentonite/cement mixtures are frequently used today as a means of retarding or controlling the flow of contaminants from surface impoundments and landfill disposal areas. Although effective in reducing the rate of flow of water and some contaminants, standard bentonite treatment is not always effective in controlling some types of contaminants, such as chlorinated hydrocarbons. Past handling and disposal of liquid chlorinated hydrocarbon waste in earthen impoundments and a landfill at an existing plant resulted in shallow ground water and soil contamination over a broad area. Following field investigations, extensive laboratory tests were conducted to investigate the feasibility of confining the plume of contamination through the installation of a slurry trench barrier. Specially designed methods of testing were used during the investigation. Standard bentonite soil mixtures using up to 6% or more bentonite were shown to be ineffective in restricting the flow of the concentrated wastes found in the subsurface strata. However, a 12%/12% bentonite/ cement dust/soil mixture was shown to restrict completely the flow or movement of the concentrated waste while reducing the flow of ground water and contaminated leachate.
Heavy Metal Leachability From Solid Waste Incinerator Ashes
Authors: Sawell S.E. , Bridle T.R. , Constable T.W.
Published: March 2008

The leachability of heavy metals in municipal solid waste (MSW) incinerator residues was evaluated using equilibrium leach tests and the sequential chemical extraction procedure. Incinerator bottom ash, boiler and economizer fly ashes were sampled from a full-scale two-stage combustion facility without pollution-control devices. Fly ashes were also collected from a pilot-plant scale, lime-based flue-gas scrubber system, connected to a mass burning incinerator facility. Generally, bottom ashes contained low to moderate concentrations of cadmium, copper, lead and zinc which are relatively insoluble under normal landfill leaching conditions. Fly ashes contained relatively moderate concentrations of cadmium and copper and much higher concentrations of lead and zinc which are readily available for leaching under normal landfill conditions. Metal leachability appears to be dependent upon metal speciation, the pH of the leaching medium and ash particle size.
Behaviour and Opinions Concerning a Mandatory Newspaper Recycling Programme: a Statistical Correlation Analysis
Authors: Mersky Ronald L.
Published: March 2008

Source-separation recycling of municipal waste is becoming increasing popular in the USA and Canada, but little is known concerning the behaviour and opinions of residents subject to recycling programmes. Residents of a Pennsylvania county subject to a mandatory newspaper recycling programme in 1985 were surveyed in 1986 concerning their behaviour and opinions with respect to that programme. Survey responses were analysed by Pearson correlation and other statistical methods. Among the conclusions of that analysis are the following: The use of drop-off sites did not decrease recycling rates; Newspaper publicity can increase recycling rates; Larger households required more time than smaller for recycling compliance; Willingness to recycle additional materials decreases as time spent on current recycling activities increases.