ALBERT

Notes: Much has been written about the development and application of quantitative methods for estimating under uncertainty the long-term radiological performance of underground disposal of radioactive wastes. Until recently, interest has been focused almost entirely on the technical challenges regardless of the role of the organization responsible for these analyses. Now the dialogue between regulators, the repository developer or operator, and other interested parties in the decision-making process receives increasing attention, especially in view of some current difficulties in obtaining approvals to construct or operate deep facilities for intermediate or high-level wastes. Consequently, it is timely to consider the options for regulators’review and evaluation of safety submissions, at the various stages in the site selection to repository closure process, and to consider, especially, the role for performance assessment (PA) within the programs of a regulator both before and after delivery of such a submission. The origins and broad character of present regulations in the European Union (EU) and in the OECD countries are outlined and some regulatory PA reviewed. The issues raised are discussed, especially in regard to the interpretation of regulations, the dangers from the desire for simplicity in argument, the use of regulatory PA to review and challenge the PA in the safety case, and the effects of the relationship between proponent and regulator. Finally, a very limited analysis of the role of PA in public hearings is outlined and recommendations are made, together with proposals for improving the mechanisms for international collaboration on technical issues of regulatory concern.

Notes: In this paper the problem of high-level nuclear waste disposal is viewed as a five-stage, cascaded decision problem. The first four of these decisions having essentially been made, the work of recent years has been focused on the fifth stage, which concerns specifics of the repository design. The probabilistic performance assessment (PPA) work is viewed as the outcome prediction for this stage, and the site characterization work as the information gathering option. This brief examination of the proposed Yucca Mountain repository through a decision analysis framework resulted in three conclusions: (1) A decision theory approach to the process of selecting and characterizing Yucca Mountain would enhance public understanding of the issues and solutions to high-level waste management; (2) engineered systems are an attractive alternative to offset uncertainties in the containment capability of the natural setting and should receive greater emphasis in the design of the repository; and (3) a strategy of “waste management” should be adopted, as opposed to “waste disposal,” as it allows for incremental confirmation and confidence building of a permanent solution to the high-level waste problem.

Notes: Physiologically-based toxicokinetic (PBTK) models are widely used to quantify whole-body kinetics of various substances. However, since they attempt to reproduce anatomical structures and physiological events, they have ahigh number of parameters. Their identification from kinetic data alone is often impossible, and other information about the parameters is needed to render the model identifiable. The most commonly used approach consists of independently measuring, or taking fom literature sources, some of the parameters, fixing them in the kinetic model, and then performing model identification on a reduced number of less certain parameters. This results in a substantial reduction of the degrees of freedom of the model. In this study, we show that this method results in final estimates of the free parameters whose precision is overestimated. We then compared this approach with an empirical Bayes approach, which takes into account not only the mean value, but also the error associated with the independently determined parameters. Blood and breath 2H8- toluene washout curves, obtained in17 subjects, were analyzed with a previously presented PBTK model suitable for person-specific dosimetry. Model parameters with the greatest effect onpredicted levels were alveolar ventilation rate QPC, fat tissue fraction VFC, blood air partition coefficient Kb, fraction of cardiac output to fat Qa/co and rate of extrahepatic metabolismVmax.p. Differences in the measured and Bayesian-fitted values of QPC, VFc and Kb were significant (p 〈 0.05), andthe precision of the fitted values Vmax.p and Qa/co went from 11 ± 5% to 75 ± 170% (NS) and from 8 ± 2% to 9 ± 2% (p 〈 0.05) respectively. The empirical Bayes approach did not result in less reliable parameter estimates: rather, it pointed out that the precision of parameter estimates can be overly optimistic when other parameters in the model, eitherdirectly measured or taken from literature sources, are treated as known without error. In conclusion, an empirical Bayes approach to parameter estimation resulted in a better model fit, different final parameter estimates, and more realistic parameter precisions.

Notes: The US Department of Transportation was interested in the risks associated with transporting Hydrazine in tanks with and without relief devices. Hydrazine is both highly toxic and flammable, as well as corrosive. Consequently, there was a conflict as to whether a relief device should be used or not. Data were not available on the impact of relief devices on release probabilities or the impact of Hydrazine on the likelihood of fires and explosions. In this paper, a Monte Carlo sensitivity analysis of the unknown parameters was used to assess the risks associated with highway transport of Hydrazine. To help determine whether or not relief devices should be used, fault trees and event trees were used to model the sequences of events that could lead to adverse consequences during transport of Hydrazine. The event probabilities in the event trees were derived as functions of the parameters whose effects were not known. The impacts of these parameters on the riskof toxic exposures, fires, and explosions were analyzed through a Monte Carlo sensitivity analysis and analyzed statistically through an analysis of variance. The analysis allowed the determination of which of the unknown parameters had a significant impact on the risks. It also provided the necessary support to a critical transportation decision even though the values of several key parameters were not known.

Notes: During the modernization of the municipal waste incinerator (MWI, maximum capacity of 180,000 tons per year) of Metropolitan Grenoble (405,000 inhabitants), in France, a risk assessment was conducted, based on four tracerpollutants: two volatile organic compounds (benzene and 1,1,1 trichloroethane) and two heavy metals (nickel and cadmium, measured in particles). A Gaussian plume dispersion model, applied to maximum emissions measured at the MWI stacks, was used to estimate the distribution of these pollutants in the atmosphere throughout the metropolitan area. A random sample telephone survey (570 subjects) gathered data on time-activity patterns, according to demographic characteristics of the population. Life-long exposure was assessed as a time-weighted average of ambient air concentrations. Inhalation alone was considered because, in the Grenoble urban setting, other routes of exposure are not likely. A Monte Carlo simulation was used to describe probability distributions of exposures and risks. The median of the life-long personal exposures distribution to MWI benzene was 3.2 · 10−5μg/m3 (20th and 80th percentiles = 1.5 · 10−5 and 6.5 · 10−5μg/m3), yielding a 2.6 · 10−10 carcinogenic risk (1.2 · 10−10 - 5.4 · 10−10). For nickel, the corresponding life-time exposure and cancer risk were 1.8 ·10−4μg/m3 (0.9 ·10−4 - 3.6 ·10−4μg/m3) and 8.6 · 10−8 (4.3 · 10−8 - 17.3 ·10−8); for cadmium they were respectively 8.3 ·10−6μg/m3 (4.0 ·10−6 - 17.6 ·10−6) and 1.5 · (7.2 · 10−9 - 3.1. · 10−8). Inhalation exposure to cadmium emitted by the MWI represented less than 1% of the WHO Air Quality Guideline (5 ng/m3), while there was a margin of exposure of more than 109 between the NOAEL (150 ppm) and exposure estimates to trichloroethane. Neither dioxins nor mercury, a volatile metal, were measured. This could lessen the attributable life-long risks estimated. The minute (VOCs and cadmium) to moderate (nickel) exposure and risk estimates are in accord with other studies on modern MWIs meeting recent emission regulations, however.

Notes: Methods of quantitative risk assessment for toxic responses that are measured on a continuous scale are not well established. Although risk-assessment procedures that attempt to utilize the quantitative information in such data have been proposed, there is no general agreement that these procedures are appreciably more efficient than common quantal dose-response procedures that operate on dichotomized continuous data. This paper points out an equivalence between the dose-response models of the nonquantal approach of Kodell and West(1)) and a quantal probit procedure, and provides results from a Monte Carlo simulation study to compare coverage probabilities of statistical lower confidence limits on dose corresponding to specified additional risk based on applying the two procedures to continuous data from a dose-response experiment. The nonquantal approach is shown to be superior, in terms of both statistical validity and statistical efficiency.

Notes: This paper discusses a successful public involvement effort that addressed and resolved several highly controversial water management issues involving environmental and flood risks associated with an electrical generation facility in British Columbia. It begins with a discussion of concepts for designing public involvement, summarizing research that indicates why individuals and groups may find it difficult to make complex choices. Reasons for public involvement, and the range of current practices are discussed. Next, four principles for designing group decision process are outlined, emphasizing decision-aiding concepts that include “value-focused thinking” and “adaptive management.” The next sections discuss the Alouette River Stakeholder Committee process in terms of objectives, participation, process, methods for structuring values and creating alternatives, information sources, and results. Discussion and conclusions complete the paper.

Notes: During the 1980s, seismic research suggested that Oregon and the City of Portland had a higher risk of a major earthquake than had previously been assumed. In 1993, the State of Oregon adopted a new version of the Oregon Structural Specialty Code, which changed the designation of western Oregon from seismic zone 2b to seismic zone 3. The City of Portland established a program and a Task Force on Seismic Strengthening of Buildings to recommend actions that would encourage upgrading of city buildings. A survey of adult city residents was conducted in April, 1996 to determine public attitudes and opinions about earthquake risks, management and mitigation of earthquake hazards, priorities for protection by strengthening buildings, evaluations of strategies for informing the public about earthquake risks, and support for specific options the city might take to protect citizens against earthquake events. Social and demographic information on individuals and households was also collected. Respondents provided ratings for a wide range of social and environmental risks, provided information on priorities for strengthening key buildings and infrastructure facilities, and answered hypothetical questions about voting for bond measures to pay for city earthquake mitigation programs. Respondents recognized significant risk from earthquakes and supported programs to protect people, especially vulnerable residents such as children and the sick. There was strong support for protecting emergency response capabilities. There was much less support for using public funds to reduce the risks associated with privately owned buildings. There were also some strong pockets of resistance to publicly funded mitigation programs in response to the hypothetical bond measures.

Notes: From a comprehensive search of the literature, the hormesis phenomenon was found to occur over a wide range of chemicals, taxonomic groups, and endpoints. By use of computer searches and extensive cross-referencing, nearly 3000 potentially relevant articles were identified. Evidence of chemical and radiation hormesis was judged to have occurred in approximately 10oO of these by use of a priori criteria. These criteria included study design features (e.g., number of doses, dose range), dose-response relationship, statistical analysis, and reproducibility of results. Numerous biological endpoints were assessed, with growth responses the most prevalent, followed by metabolic effects, reproductive responses, longevity, and cancer. Hormetic responses were generally observed to be of limited magnitude with an average maximum stimulation of 30 to 60 percent over that of the controls. This maximum usually occurred 4- to 5-fold below the NOAEL for a particular endpoint. The present analysis suggests that hormesis is a reproducible and generalizable biological phenomenon and is a fundamental component of many, if not most, dose-response relationships. The relatively infrequent observation of homesis in the literature is believed to be due primarily to experimental design considerations, especially with respect to the number and range of doses and endpoint selection. Because of regulatory considerations, most toxicologic studies have been carried out at high doses above the low-dose region where the hormesis phenomenon occurs.

Notes: As the use of digital computers for instrumentation and control of safety-critical systems has increased, there has been a growing debate over the issue of whether probabilistic risk assessment techniques can be applied to these systems. This debate has centered on the issue of whether software failures can be modeled probabilistically. This paper describes a “context-based” approach to software risk assessment that explicitly recognizes the fact that the behavior of software is not probabilistic. The source of the perceived uncertainty in its behavior results from both the input to the software as well as the application and environment in which the software is operating. Failures occur as the result of encountering some context for which the software was not properly designed, as opposed to the software simply failing “randomly.” The paper elaborates on the concept of “error-forcing context” as it applies to software. It also illustrates a methodology which utilizes event trees, fault trees, and the Dynamic Flowgraph Methodology (DFM) to identify “error-forcing contexts” for software in the form of fault tree prime implicants.

Notes: Australian state and federal agencies use a broad range of methods for setting conservation priorities for species at risk. Some of these are based on rule sets developed by the International Union for the Conservation ofNature, while others use point scoring protocols to assess threat. All of them ignore uncertainty in the data. In this study, we assessed the conservation status of 29 threatened vascular plants from Tasmania and New South Wales using a variety of methods including point scoring and rule-based approaches. In addition, several methods for dealing with uncertainty in the data were applied to each of the prioritysetting schemes. The results indicatethat the choice of a protocol for setting priorities and the choice of the way in which uncertainty is treated may make important differences to the resulting assessments of risk. The choice among methods needs to be rationalized within the management context in which it is to be applied. These methods are not a substitute for more formal risk assessment.

Notes: This paper describes a multi-stakeholder process designed to assess thepotential health risks associated with adverse air quality in an urban industrial neighborhood. The paper briefly describes the quantitative health risk assessment conducted by scientific experts, with input by a grassroots community group concerned about the impacts of adverse air quality on theirhealth and quality of life. In this case, rather than accept the views of the scientific experts, the community used their powers of perception toadvantage by successfully advocating for a professionally conducted community health survey. This survey was designed to document, systematically and rigorously, the health risk perceptions community members associated with exposure to adverse air quality in their neighborhood. This paper describes theinstitutional and community contexts within which the research is situated as well as the design, administration, analysis, and results of the community health survey administered to 402 households living in an urban industrial neighborhood in Hamilton, Ontario, Canada. These survey results served tolegitimate the community's concerns about air quality and tohelp broaden operational definitions of ‘health.’ In addition, the resultsof both healthrisk assessment exercises served to keep issues of air quality on the localpolitical agenda. Implications of these findings for our understanding of theenvironmental justice process as well as the ability of communitiesto influence environmental health policy are discussed.

Notes: Psychometric data on risk perceptions are often collected using the method developed by Slovic, Fischhoff, and Lichtenstein, where an array of risk issues are evaluated with respect to a number of risk characteristics, such as how dreadful, catastrophic or involuntary exposure to each risk is. The analysis of these data has often been carried out at an aggregate level, where mean scores for all respondents are compared between risk issues. However, this approach may conceal important variation between individuals, and individual analyses have also been performed for single risk issues. This paper presents a new methodological approach using a technique called multilevel modelling for analysing individual and aggregated responses simultaneously, to produce unconditional and unbiased results at both individual and aggregate levels of the data. Two examples are given using previously published data sets on risk perceptions collected by the authors, and results between the traditional and new approaches compared. The discussion focuses on the implications of and possibilities provided by the new methodology.

Notes: The use of uncertainty factors in the standard method for deriving acceptable intake or exposure limits for humans, such as the Reference Dose (RfD), may be viewed as a conservative method of taking various uncertainties into account. As an obvious alternative, the use of uncertainty distributions instead of uncertainty factors is gaining attention. This paper presents a comprehensive discussion of a general framework that quantifies both the uncertainties in the no-adverse-effect level in the animal (using a benchmark-like approach) and the uncertainties in the various extrapolation steps involved (using uncertainty distributions). This approach results in an uncertainty distribution for the no-adverse-effect level in the sensitive human subpopulation, reflecting the overall scientific uncertainty associated with that level. A lower percentile of this distribution may be regarded as an acceptable exposure limit (e.g., RfD) that takes account of the various uncertainties in a nonconservative fashion. The same methodology may also be used as a tool to derive a distribution for possible human health effects at a given exposure level. We argue that in a probabilistic approach the uncertainty in the estimated no-adverse-effect-level in the animal should be explicitly taken into account. Not only is this source of uncertainty too large to be ignored, it also has repercussions for the quantification of the other uncertainty distributions.

Notes: This research explores public judgments about the threat-reducing potential of experts, individual behavior, and government spending. The data are responses of a national sample of 1225 to mail surveys that include measures of several dimensions of public judgments about violent crime, automobile accidents, hazardous chemical waste, air pollution, water pollution, global warming, AIDS, heart disease, and cancer. Beliefs about who can best mitigate threats are specific to classes of threats. In general, there is little faith that experts can do much about violent crime and automobile accidents, moderate faith in their ability to address problems of global warming, and greater expectations for expert solutions to the remaining threats. People judge individual behavior as effective in reducing the threats of violent crime, AIDS, heart disease, and automobile accidents but less so for the remaining threats. Faith in more government spending is highest for AIDS and the other two health items, lowest for the trio of violent crime, automobile accidents, and global warming, and moderate for the remaining threats. For most threats, people are not distributed at the extremes in judging mitigators. Strong attitudinal and demographic cleavages are also lacking, although some interesting relationships occur. This relative lack of sharp cleavages and the generally moderate opinion indicate ample opportunity for public education and risk communication.

Notes: Recreational and subsistence hunters and anglers consume a wide range of species, including birds, mammals, fish and shellfish, some of which represent significant exposure pathways for environmental toxic agents. This study focuses on the Department of Energy's (DOE'S) Savannah River Site (SRS), a former nuclear weapons production facility in South Carolina. The potential risk of contaminant intake from consuming mourning doves (Zenaida macroura), the most popular United States game bird, was examined under various risk scenarios. For all of these scenarios we used the mean tissue concentration of six metals (lead, mercury, cadmium, selenium, chromium, manganese) and radiocesium, in doves collected on and near SRS. We also estimated risk to a child consuming doves that had the maximum contaminant level. We used the cancer slope factor for radiocesium, the Environmental Protection Agencies UptakeBiokinetic model for lead, and published reference doses for the other metals. As a result of our risk assessments we recommend management of water levels in contaminated reservoirs so that lake bed sediments are not exposed to use by gamebirds and other terrestrial wildlife. Particularly, measures should be taken to insure that the hunting public does not have access to such a site. Our data also indicate that doves on popular hunting areas are exposed to excess lead, suggesting that banning lead shot for doves, as has been done for waterfowl, is desirable.

Notes: Exposure duration is an important component in determining long-term dose rates associated with exposure to environmental contaminants. Surveys of exposed populations collect information on individuals' past behaviors, including the durations of a behavior up to the time of the survey. This paper presents an empirical approach for determining the distribution of total durations that is consistent with the distribution past durations obtained from surveys. This approach is appropriate where the rates of beginning and ending a behavior are relatively constant over time. The approach allows the incorporation of information on the distribution of age in a population into the determination of the distribution of durations. The paper also explores the impact of “longevity” bias on survey data. A case study of the application of this approach to two angler populations is also provided. The results of the case study have characteristics similar to the results reported by Israeli and Nelson (Risk Anal. 12, 65-72 (1992)) from their analytical model of residential duration. Specifically, the average period of time for the total duration in the entire population is shorter than the average period of time reported for historical duration in the surveyed individuals.

Notes: Information format can influence the extent to which target audiences understand and respond to risk-related information. This study examined four elements of risk information presentation format. Using printed materials, we examined target audience perceptions about: (a) reading level; (b) use of diagrams vs. text; (c) commanding versus cajoling tone; and (d) use of qualitative vs. quantitative information presented in a risk ladder. We used the risk communication topic of human health concerns related to eating noncommercial Great Lakes fish affected by chemical contaminants. Results from the comparisons of specific communication formats indicated that multiple formats are required to meet the needs of a significant percent of anglers for three of the four format types examined. Advisory text should be reviewed to ensure the reading level is geared to abilities of the target audience. For many audiences, a combination of qualitative and quantitative information, and a combination of diagrams and text may be most effective. For most audiences, a cajoling rather than commanding tone better provides them with the information they need to make a decision about fish consumption. Segmenting audiences regarding information needs and communication formats may help clarify which approaches to take with each audience.

Notes: Using exploratory data analysis, probability plots, scatterplots, and computer animations to rotate and visualize the data, we fit a trivariate Normal distribution to data for the height, the natural logarithm of body weight, and the body fat for 646 men between the ages of 50 and 80 years as reported by the medical staff of the U.S. Veterans Administration's “Normative Aging Study” in Boston, MA. Although these data do not include any children, women, or young men, the measurements represent the best data that we could find through a 4-year search. We believe that these data are well measured and reliable for men in the specified age range and that these data reveal an interesting statistical pattern for use in probabilistic PBPK models.

Notes: Significant research work has been completed in the development of risk-based inservice inspection (ISI) and testing (IST) technology for nuclear power plant applications through the ASME Center For Research and Technology Development. This paper provides technology that has been developed for these engineering applications. The technology includes risk-based ranking methods, beginning with the use of plant probabilistic risk assessment (PRA), for the determination of risk-significant and less risk-significant components for inspection and the determination of similar populations for pumps and valves for inservice testing. Decision analysis methods are outlined for developing ISI and IST programs. This methodology integrates nondestructive examination data, structural reliability/risk assessment results, PRA results, failure data, and expert opinion to evaluate the effectiveness of ISI programs. Similarly, decision analysis uses the output of failure mode and causes analysis in combination with data, expert opinion, and PRA results to evaluate the effectiveness of IST programs. Results of pilot applications of these ASME methods to actual nuclear plant systems and components are summarized. The results of this work are already being used to develop recommended changes in ISI and IST requirements by the ASME Section XI and the ASME Operation and Maintenance Code organizations. A perspective on Code and regulatory adoption is also outlined. Finally, the potential benefits to the nuclear industry in terms of safety, person-rem exposure, and costs are summarized.

Notes: Probabilistic Seismic Hazard Analysis (PSHA) is a methodology that estimates the likelihood that various levels of earthquake-caused ground motions will be exceeded at a given location in a given future time period. Due to large uncertainties in all of the geosciences data and in their modeling, multiple model interpretations are often possible. This leads to disagreements among the experts, which in the past has led to disagreement on the selection of a ground motion for design at a given site. This paper reports on a project, co-sponsored by the U.S. Nuclear Regulatory Commission, the U.S. Department of Energy, and the Electric Power Research Institute, that was undertaken to review the state-of-the-art and improve on the overall stability of the PSHA process, by providing methodological guidance on how to perform a PSHA. The project reviewed past studies and examined ways to improve on the present state-of-the-art. In analyzing past PSHA studies, the most important conclusion is that differences in PSHA results are commonly due to process rather than technical differences. Thus, the project concentrated heavily on developing process recommendations, especially on the use of multiple experts, and this paper reports on those process recommendations. The problem of facilitating and integrating the judgments of a diverse group of experts is analyzed in detail. The authors believe that the concepts and process principles apply just as well to non-earthquake fields such as volcanic hazard, flood risk, nuclear-plant safety, and climate change.

Notes: Trichloroacetic acid (TCA) is major metabolite of trichloroethylene (TRI) thought to contribute to its hepatocarcinogenic effects in mice. Recent studies have shown that peak blood concentrations of TCA in rats do not occur until approximately 12 hours following an oral dose of TRI. However, blood concentrations of TRI reach maximum within an hour and are nondetectable after 2 hours.(1) The results of study which examined the enterohepatic recirculation (EHC) of the principle TRI metabolited(2) was used to develop physiologically-based pharmacokinetic model for TRI, which includes enterohepatic recirculation of its metabolites. The model quantitatively predicts the uptake, distribution and elimination of TRI, trichloroethanol, trichloroethanol-glucuronide, and TCA and includes production of metabolites through the enterohepatic recirculation pathway. Physiologic parameters used in the model were obtained from the literature.(3.4) Parameters for TRI metabolism were taken from Fisher et al.(5) Other kinetic parameters were found in the literature or estimated from experimental data.(2) The model was calibrated to data from experiments of an earlier study where TRI was orally administered(2) Verification of the model was conducted using data on the enterohepatic recirculation of TCEOH and TCA(2) chloral hydrate data (infusion doses) from Merdink,(1) and TRI data from Templin(l) and Larson and Bull.(1)

Notes: Estimates were made of the numbers of liver carcinogens in 390 long-term bioassays conducted by the National Toxicology Program (NTP). These estimates were obtained from examination of the global pattern of p-values obtained from statistical tests applied to individual bioassays. Representative estimates of the number of liver carcinogens (90% confidence interval in parentheses) obtained in our analysis compared to NTP's determination are as follows: female rats—49 (23, 76), NTP = 30; male rats—88 (59, 116), NTP = 35; female mice—131 (105, 157), NTP = 81; male mice—100 (73, 126), NTP = 61; overall—166 (135, 197), NTP = 108. The estimator from which these estimates were obtained is biased low by an unknown amount. Consequently, this study provides persuasive evidence of the existence of more rodent liver carcinogens than were identified by the NTP.

Notes: In north-central Wopmay Orogen, syntectonic low-P(Buchan-type) suites of mineral isograds outline regional metamorphic temperature culminations that are associated, at the higher structural levels, with emplacement of early Proterozoic plutons in the west part of a deformed and eastward transported continental margin prism. The mapped isograds mark the first occurrence of biotite, staurolite, andalusite, sillimanite, sillimanite-K feldspar and K feldspar-plagioclase-quartz ± muscovite (granitic) pods in metapelites, with increasing proximity to the plutons.Microprobe analyses and field observations have resulted in the formulation of reactions for the ‘ideal’pelitic system K2O-Na2O-FeO-MgO-Al2O3-SiO2-H2O-Al2O3-SiO2-H2O, to account for the various mineral assemblages of each metamorphic zone. A P-T petrogenetic grid showing erosion surface P-T curves for the northern Wopmay Orogen pelites, compiled on the basis of the mapped isograds and the inferred reaction(s) for each metamorphic zone, documents a variation in exposed metamorphic pressure ranging between 2 and 4 kbar.The configuration of a new bathograd, based on the invariant model reaction sillimanite + K feldspar + plagioclase + biotite + quartz + vapor ± muscovite + liquid and interpolated across three metamorphic suites, is consistent with a major regional structure culmination and with independently determined pressures obtained from anorthite-grossular-quartz-Al2SiO5 geobarometry. The positive correlation between the configuration of the bathograd and the structural and pressure culmination points to the pressure-dependence of anatectic-granitic-pod mineral associations.

Notes: Variations in assemblage and composition of the constituent minerals in basic and intermediate metavolcanics encountered in the Zarouchla Group of the Phyllite-Quartzite Series are consistent with a progressive sequence, corresponding to temperature conditions estimated at 290-380°C (minimum values) under a total pressure greater than 3°5kbar and possibly as high as 5 kbar. In the absence of more critical evidence, the parageneses recorded in the metavolcanic rocks are interpreted as belonging to a prograde facies series from the lawsonite-albitechlorite facies through the pumpellyite-actinolite facies to the greenschist facies. The present distribution of mineral assemblages does not show a simple increase of metamorphic grade in a given direction but is apparently related to the tectonic evolution of the metamorphic sequence.

Notes: Abstract Mylonites from shear zones cutting Hercynian gneisses in the central Pyrenees have been studied in thin section and using the electron microprobe. The shear zones contain retrogressive greenschist facies assemblages implying introduction of an aqueous fluid during deformation in the zones. Textural evidence suggests that fluid-rock interaction occurred throughout the active life of the shear zones.Whole-rock chemical changes during deformation are documented in a variety of mylonitic lithologies and retrogressed country rocks. The overall effect was to reduce chemical differences between lithologies. Activity diagrams show that this would be expected if a hydrous fluid was circulating between different lithologies during deformation. In most cases fluid/rock ratios were relatively small resulting in gradual chemical changes and repeated recrystallization. ‘Open-system’behaviour with reduction in the number of phases is seen in some granite mylonites, suggesting focusing of fluid movement in parts of the shear zones. Continual fluid-rock interaction may have led to reaction-enhanced ductility in the shear zones over a long period of time. The source of fluid is uncertain, but may be related to underthrusting of material beneath the area investigated.

Notes: Abstract The hornblende-bearing basic gneisses in the Uvete area, central Kenya, were metamorphosed under a narrow range of P and T (6.5 ± 0.5kbar and 530 ± 40°C) of the staurolitekyanite zone in the Mozambique metamorphic belt. They show a wide variety of divariant and trivariant mineral assemblages consisting of hornblende, cumminatonite, gedrite, anthophyllite, chlorite, garnet, epidote, clinopyroxene, plagio-clase and quartz. The bulk and mineral chemistries and the graphical representation of phase relations show that each mineral assemblage approaches chemical equilibrium and defines a unique composition volume in the A′(Al + Fe3+− (13/7)Na)-F(Fe2+)-M′(Mg)-C′(Ca-(3/7)Na) tetrahedron. The composition volumes are distributed quite regularly and do not overlap each other.The phase relations in the Uvete area are in contrast with those in the staurolite-kyanite zone amphibolites in the Mt. Cube quadrangle, Vermont. The amphibolites there contain low-variance mineral assemblages formed under different values of μH2O and μCO2. These assemblages define overlapping composition volumes in the A′-F′-M′-C’tetrahedron.The mineral assemblages in the Uvete area are interpreted as having formed in equilibrium with fluid at a high and nearly constant μH2O value. Such a fluid composition was externally controlled by the supply of H2O-rich fluid expelled from the surrounding pelitic and psammitic rocks. The body size of the basic gneisses in the Uvete area (less than 400m in thickness) was small enough for the fluid to migrate completely.

Notes: Abstract Blueschist-facies rocks on the Seward Peninsula constitute a structurally coherent terrane measuring at least 100 × 150 km. Radiometric age data indicate that high-pressure metamorphism probably occurred in Jurassic rather than in Palaeozoic or Precambrian time, as previously suggested. Protolith sediments (Nome Group) are of intracontinental basin or continental margin type, and of lower Palaeozoic and possibly late Precambrian age, thus predating the high pressure metamorphism by more than 200 m.y.Blueschist-facies mineral assemblages were developed in almost all lithologies of the Nome Group, and are best preserved in FeTi-rich metabasites (glaucophane + almandine + epidote) and pelites (glaucophane + chloritoid + phengite). A lawsonite–crossite subfacies was developed in possible Nome Group rocks on the east flank of the Darby Mountains. Albite–epidote–amphibolite facies assemblages characterize Nome Group rocks in the southwestern part of the Peninsula. Metamorphism in the central zone of the terrane passed from early lawsonitic to subsequent epidote–almandine–glaucophane schist subfacies with the local development (east of the Nome River) of eclogitic assemblages.The high pressure metamorphic minerals were synkinematic with the development of mesoscopic-scale intrafolial isoclinal folds and a flattening foliation of consistent orientation. Initiation of uplift probably corresponded to the growth of barroisite rims on earlier sodic and actinolitic amphiboles, and partial post-kinematic greenschist facies replacements record later stages of decompression. Ophiolites and melange are not associated with the Seward Peninsula blueschists. The high-pressure metamorphism was caused by tectonic loading of a continental plate by an allochthon of indeterminate origin. The PT conditions of high pressure metamorphism were approximately 9–11 kbar, 400–450°C, thus falling between the PT paths of the Shuksan and Franciscan terranes.

Notes: Abstract Two periods of garnet growth (Gt1 and Gt2) have been found in the Finnmarkian nappes of north Norway. In the Kolvik Nappe (the lowest nappe) Gt1 has preserved an S2 syntectonic spiral inclusion fabric; in the Olderfjord Nappe an earlier S1 fabric and an interkinematic inter-D1–D2 fabric have been preserved in Gt1 whilst only the S1 fabric has been found in Gt1 in the Brennsvik Nappe (the highest nappe). In each nappe Gt2 overgrew a penetrative fabric (S2) wrapped around Gt1. In the Kolvik Nappe inclusion fabrics may be continuous from Gt1 into Gt2 but in the higher nappes there is a distinct break. Gt2 may have been partially syntectonic with D3 in the Brennsvik Nappe.Chemically Gt1 in the Kolvik Nappe and in parts of the Olderfjord and Brennsvik Nappes has antithetic Fe-Mn zoning. In all nappes XCa and XMg are weakly zoned in Gt1; XMg increases outwards and is greater in the higher nappes in Gt1 suggesting higher nucleation temperatures. In the Olderfjord and Brennsvik Nappes Gt2 is marked by increasing XCa, probably due to changing garnet-plagioclase equilibria, although the Fe/Mg ratio remains constant. XMg is higher in Gt2 than Gt1.Basement rocks within the nappe pile have an early pre-Finnmarkian growth (Gt1) and a later Finnmarkian growth (GtH) correlated with Gt2 on the basis of chemical zoning patterns.The diachroneity of Gt1 is ascribed to progressively earlier (compared to the structural development) cessation of overstepping of garnet-forming reactions before peak metamorphism in the higher nappes, resulting in earlier structural events being preserved.

Notes: Abstract Fluid inclusion studies of rocks from the late Archaean amphibolite-facies to granulite-facies transition zone of southern India provide support for the hypothesis that CO2,-rich H2O-poor fluids were a major factor in the origin of the high-grade terrain. Charnockites, closely associated leucogranites and quartzo-feldspathic veins contain vast numbers of large CO2-rich inclusions in planar arrays in quartz and feldspar, whereas amphibole-bearing gray gneisses of essentially the same compositions as adjacent charnockites in mixed-facies quarries contain no large fluid inclusions. Inclusions in the northernmost incipient charnockites, as at Kabbal, Karnataka, occasionally contain about 25 mol. % of immiscible H2O lining cavity walls, whereas inclusions from the charnockite massif terrane farther south do not have visibile H2OMicrothermometry of CO2 inclusions shows that miscible CH4 and N2 must be small, probably less than 10mol.%combined. Densities of CO2 increase steadily from north to south across the transitional terrane. Entrapment pressures calculated from the CO2 equation of state range from 5 kbar in the north to 7.5 kbar in the south at the mineralogically inferred average metamorphic temperature of 750°C, in quantitative agreement with mineralogic geobarometry. This agreement leads to the inference that the fluid inclusions were trapped at or near peak metamorphic conditions.Calculations on the stability of the charnockite assemblage biotite-orthopyroxene-K-feldspar-quartz show that an associated fluid phase must have less than 0.35 H2O activity at the inferred P and T conditions, which agrees with the petrographic observations. High TiO2 content of biotite stabilizes it to lower H2O activities, and the steady increase of biotite TiO2 southward in the area suggests progressive decrease of aH2O with increasing grade. Oxygen fugacities calculated from orthopyroxene-magnetite-quartz are considerably higher than the graphite CO2-O2 buffer, which explains the absence of graphite in the charnockites.The present study quantifies the nature of the vapours in the southern India granulite metamorphism. It remains to be determined whether CO2-flushing of the crust can, by itself, create large terranes of largeion lithophile-depleted granulites, or whether removal of H2O-bearing anatectic melts is essential.

Notes: Abstract There are discrete masses of un-deformed metabasite within the blueschist series of the island of Syros. Greece. Around the margins of these masses are zonal sequences through rocks showing intracrystalline deformation but without a geometric fabric, to rocks with discrete and anastomosing shear zones, and finally to penetratively foliated rocks with isolated relics of the original undeformed texture. Textural relics suggest that this spatial sequence is at least qualitatively also a temporal sequence.This progressive shear zone deformation took place concurrently with a glaucophane-epidote to eclogite reaction. The reaction pathways in the rocks that underwent the shear zone deformation can be compared with those in rocks of a similar composition that suffered a longer deformation history and show no relics of an undeformed parent. Although the final assemblages are in both cases the same, the pathways are different. These differences are in part related to reactions promoted by the change from local to bulk equilibrium on the onset of deformation in the rocks. They are also related to the crystallization and later breakdown during the sequence of progressive equilibration of a metastable phase, in this case an impure glaucophane.

Notes: Abstract The Rockley Volcanics from near Oberon, New South Wales occur within the aureole of the Carboniferous Bathurst Batholith and have been contact metamorphosed at P ∼ 100 ± 50MPa (10.5kbar) and a maximum T ∼ 565°C in the presence of a C–O–H fluid. Prior to contact metamorphism the volcanics were regionally metamorphosed and altered with the extensive development of actinolite, chlorite, plagioclase, quartz and calcite. The contact metamorphosed equivalents of these rocks have been subdivided into: Ca-poor (cordierite + gedrite), Mg-rich (amphibole + olivine + spinel), mafic (amphibole + plagioclase) and Ca-rich (amphibole + garnet + diopside; diopside + plagioclase; garnet + diopside + wollastonite) rocks.The chemistry of the minerals in the hornfelses was controlled by the bulk rock chemistry and fluid composition. Pargasites and hastingsites as well as an unusual phlogopite with blue green pleochroism, are found in Ca-rich hornfelses. A comparison of the assemblages with experimentally derived equilibria suggests that the fluid phase associated with the Ca-rich hornfelses was water-rich (Xco2= 0.1 to 0.3) while that associated with the Mg-rich hornfelses was enriched in CO2 (Xco2 〉 0.7). The different hornfels types have reacted to contact metamorphism independently in both their solid and fluid chemistries.

Notes: Abstract A garnet–hornblende Fe–Mg exchange geothermometer has been calibrated against the garnet–clinopyroxene geothermometer of Ellis & Green (1979) using data on coexisting garnet + hornblende + clinopyroxene in amphibolite and granulite facies metamorphic assemblages. Data for the Fe–Mg exchange reaction between garnet and hornblende have been fitted to the equation. In KD=Δ (XCa,g) where KD is the Fe–Mg distribution coefficient, using a robust regression approach, giving a thermometer of the form: with very satisfactory agreement between garnet–hornblende and garnet–clinopyroxene temperatures. The thermometer is applicable below about 850°C to rocks with Mn-poor garnet and common hornblende of widely varying chemistry metamorphosed at low aO2.Application of the garnet–hornblende geothermometer to Dalradian garnet amphibolites gives temperatures in good agreement with those predicted by pelite petrogenetic grids, ranging from 520°C for the lower garnet zone to 565–610°C for the staurolite to kyanite zones. These results suggest that systematic errors introduced by closure temperature problems in the application of the garnet–clinopyroxene geothermometer to the ‘calibration’data set are not serious. Application to ‘eclogitic’garnet amphibolites suggests that garnet and hornblende seldom attain Fe–Mg exchange equilibrium in these rocks.Quartzo-feldspathic and mafic schists of the Pelona Schist on Sierra Pelona, Southern California, were metamorphosed under high pressure greenschist, epidote–amphibolite and (oligoclase) amphibolite facies beneath the Vincent Thrust at pressures deduced to be 10±1 kbar using the phengite geobarometer, and 8–9kbar using the jadeite content of clinopyroxene in equilibrium with oligoclase and quartz. Application of the garnet–hornblende thermometer gives temperatures ranging from about 480°C at the garnet isograd through 570°C at the oligoclase isograd to a maximum of 620–650°C near the thrust. Inverted thermal gradients beneath the Vincent Thrust were in the range 170 to 250°C per km close to the thrust.

Notes: Abstract Rock fracture enhances permeability and provides pathways through which fluids migrate. During contact metamorphism, fluids contained in isolated pores and fractures expand in response to temperature increases caused by the dissipation of heat from magmas. Heat transport calculations and thermomechanical properties of water-rich fluids demonstrate (1) that thermal energy is a viable mechanism to produce and maintain pore fluid pressure (Pf) in a contact metamorphic aureole; (2) that the magnitude of Pf generated is sufficient to propagate fractures during the prograde thermal history (cause hydrofracture) and enhance permeability; and (3) that Pf-driven fracture propagation is episodic with time-scales ranging from years to thousands of years. Because Pf dissipation is orders of magnitude faster than P, f buildup, Pf oscillations and cyclical behaviour are generated as thermal heating continues. The Pf cycle amplitude depends on the initial fracture length, geometry and the rock's resistance to failure whereas the frequency of fracture depends on the rate of heating. Consequently, oscillation frequency also varies spatially with distance from the heat source.Time series of fluid pressures caused by this process suggest that cyclical fracture events are restricted to an early time period of the prograde thermal event near the intrusive contact. In the far field, however, individual fracture events have a lower frequency but continue to occur over a longer time interval. Numerous fracture cycles are possible within a single thermal event. This provides a provisional explanation for multiple generations of veins observed in outcrop. P f cycling and oscillations may explain several petrological features. If pore fluids are trapped at various positions along a pressure cycle, the large amplitude of Pf variations for small fractures may account for different pressures recorded by fluid inclusions analysed from a single sample. Pf oscillations, during a single thermal episode, also drive chemical reactions which can produce complex mineral textures and assemblages for discontinuous reactions and/or zoning patterns for continuous reactions. These can mimic polymetamorphic or disequilibrium features.Temporal aspects of fracture propagation and permeability enhancement also constrain the likely timing of fluid flow and fluid-mineral interactions. These data suggest that fluid flow and fluid-mineral reactions are likely to be restricted to an early period in the prograde thermal history, characterized by high Pf coincident with relatively high temperatures, fracture propagation and consequent increases in permeability. This early prograde hydration event is followed by diffusional peak metamorphic reactions. This relationship is evident in the complex mineralogical textures common in some metamorphosed rocks.

Notes: Abstract Andalusite-bearing veins formed during contact metamorphism in the aureole of the Vedrette di Ries tonalite. In the veins, quartz crystals that are completely armoured by andalusite or that occur in strain shadow areas contain three generations of fluid inclusions: low-salinity H2O-CO2-CH4 mixtures with CH4/(CO2+ CH4) ± 0.35 (type A); low-salinity aqueous fluids (type B); H2O-free, CO2-CH4 fluids with the same carbonic speciation as A (type C). Carbonic types A and C typically have a dark appearance, which is attributed to graphite coatings on inclusion walls. Microstructural analysis of the host quartz and calculated densities indicate that type A inclusions were likely trapped during vein formation. These inclusions underwent strain-assisted re-equilibration during cooling that resulted in density increases without change of composition. After the rocks had cooled below about 350 ° C, type C inclusions appear to have formed from one of the immiscible fractions after unmixing of the H2O-CO2-CH4 fluid mixtures. Aqueous type B inclusions, apparently trapped between 225 and 350 ° C, could represent an independent fluid, or could be the H2O-rich fraction of unmixed type A fluids. Taking account of the uncertainties, the composition and density of the complex type A inclusion fluids are in good agreement with the properties of primary fluids calculated from the petrological data. The fluid inclusion data support the model of vein formation by hydrofracturing as a result of dehydration of graphitic metapelites. These new results also demonstrate the importance of considering strain in the interpretation of metamorphic fluid inclusions.

Notes: Abstract Aqueous fluid released in metamorphism is transported upwards from depth to the Earth's surface. I propose a hydrofracturing model for the fluid transport. In the model, fluid is transported by the upward propagation of a two-dimensional vertical fluid-filled crack from a fluid reservoir (e.g. overpressured compartment under a seal) at depth to the Earth's surface; fluid is injected consecutively from the reservoir into the crack at a given (but not necessarily constant) injection rate; some of the injected fluid is lost by infiltration from the crack walls into the surrounding permeable rock. An approximate solution of the crack propagation is obtained using fluid dynamics for turbulent film flow and linear elastic fracture mechanics. The solution shows the transition from a regime in which the excess pressure of the fluid in the reservoir drives the propagation to a regime in which the buoyancy of the fluid in the crack drives the propagation. For example, if the net injection rate of H2O is 1 m2/s, the regime transition occurs when the vertical crack length becomes 280 m; after the transition, the propagation velocity and average aperture are constant: 21 m/s and 4.8 cm. If the injection rate is lower than a critical value, hydrofracturing cannot be an effective mode for the fluid transport because of the significant fluid loss by infiltration from the crack walls into the surrounding permeable rock. Assuming a fluid-saturated crust with hydrostatic pore fluid pressure, a lower limit can be estimated for the injection rate required to transport H2O by hydrofracturing without significant fluid loss. For example, the lower limit for transport from a depth of 15 km to the Earth's surface is estimated at 0.2 m2/s if the crustal permeability is 10-17 m2. The lower limit decreases with decreasing crustal permeability.

Notes: Abstract Microstructural and chemical analysis of plagioclase in 20 superficially similar amphibolite facies ductile shear zones in metagabbors and amphibolites of the Ivrea Zone in Italy reveals significant differences in An and Ba contents. Plagioclase, which was deformed at P-T conditions lower than those of the wall rocks, occurs in the following four different microstructural situations with different chemical compositions: (i) relatively undeformed porphyroclasts, (ii) dynamically recrystallized grains and subgrains rimming the porphyroclasts, (iii) infill of microcracks cross-cutting the porphyroclasts and (iv) fine-grained recrystallized grains in the matrix of the shear zones. The differences in the An and Ba contents are caused by partial chemical equilibration of plagioclase in the shear zones during and partly after deformation. Changes in An and Ba contents were caused by fluid-assisted grain-boundary migration recrystallization, as well as by solid-state diffusion, while fluid activity was high. The relation between the composition and microstructures of the plagioclase in the shear zones indicates that in the different shear zones, fluids ceased to be active during different stages in the late shear zone deformation history.The interpretation of the variations in composition and microstructures reveals that only grains that developed by grain-boundary migration recrystallization and that are not adjacent to porphyroclasts reflect P-T conditions during the dominant shear-zone deformation.

Notes: Abstract TEM and XRD techniques were used to study crystal growth characteristics of the fabric-forming phyllosilicates which developed in response to low-grade metamorphism and tectonic imbrication in part of the Southern Uplands thrust terrane. Prograde regional metamorphism, ranging from late diagenesis through the anchizone to the epizone, was accompanied by the development of a slaty cleavage which is commonly bedding-parallel. TEM-measured mean thicknesses of white mica and chlorite crystallite populations increase with advancing grade and correlate with XRD-measured crystallinity indices. Analytical TEM data show that prograde changes in composition lead to a net loss of Si, Ca and minor Fe from the fabric-forming phyllosilicates. White micas are paragonite-poor phengites with a mean b lattice parameter of 9.037 Å, and indicate an intermediate pressure series of metamorphism with a field gradient of 〈25° C km-1. Chlorite compositions evolved from diabantite (with intergrown corrensite) to ripidolite over an estimated temperature range of 150–320° C. Field gradient and temperature estimates suggest that crystal growth and fabric development occurred at burial depths ranging from 6 km to at least 13 km in the thrust terrane. During late diagenesis, crystal growth of white mica and chlorite was predominantly a consequence of polytypic and phase transitions, and resulted in similar size distributions which resemble typical Ostwald ripening curves. Under anchizonal and epizonal conditions, white mica grew more rapidly than chlorite because of its greater ability to store strain energy and recover from subgrain development; as a result crystal thickness distributions are not typical of Ostwald ripening. In contrast, chlorite crystals which grew under these conditions developed subgrain boundaries at high strain rates which were only partially recovered at low strain rates; these retained dislocations reduce the crystallite thicknesses detected by TEM and XRD, compared with those of white mica. These differences in strain-induced crystal growth indicate that white mica (illite) and chlorite crystallinity indices are likely to show significant differences where low-grade metamorphism is closely associated with tectonic fabric development.

Notes: Abstract The metamorphic history of the Archaean Superior Province crystalline basement in the Palaeoproterozoic Ungava Orogen attests to the importance of structural and geohydrological controls on a retrograde amphibolite-granulite transition. Two distinct metamorphic suites, separated in age by nearly one billion years, are recognized in extensively exposed tonalitic to dioritic metaplutonic gneisses. The older suite comprises c. 2.7-Ga granulite facies assemblages (orthopyroxene-clinopyroxene-hornblende-plagioclase-ilmenite ± biotite ± quartz) that record moderate pressures (±5 kbar) and high temperatures (±800° C). A younger, c. 1.8-Ga suite resulted from amphibolitization of the granulites and is characterized by regionally extensive amphibolite facies mineral zones that broadly parallel the basal décollement of the overlying Proterozoic Cape Smith Thrust Belt. Deformation/mineral growth relationships in the amphibolitized basement indicate that extensive hydration and re-equilibration of the Archaean granulites occurred during thrust belt deformation. The transition from granulite facies to amphibolite facies assemblages is characterized by the growth of garnet-hornblende-quartz ° Cummingtonite coronas between plagioclase and orthopyroxene-clinopyroxene, as well as titanite coronas on ilmenite. Multi-equilibrium thermobarometry on the coronitic assemblages documents re-equilibration of the granulitic gneiss to 7.7 kbar at 644° C in the south and 9.8 kbar at 700° C in the north. The variably deformed, amphibolite facies domain sandwiched between the coronitic garnet zone and the basal décollement is marked by significant metasomatic changes in major element concentrations within tonalite. These changes are compatible with equilibrium flow of an aqueous-chloride fluid down a temperature gradient. The source of fluids for basement hydration/metasomatism is interpreted to be dehydrating clastic rocks in the overlying thrust belt, with fluid flow probably focused along the basal décollement.

Notes: Sapphirine occurs in a 3-5 m wide zone between amphibole-lherzolite and garnetiferous metagabbro at Finero in the Ivrea Zone, NW Italian Alps. Layers consisting of plag + hb + sa + cpx + opx + sp + gt are interbanded with spinel pyroxenites, which may contain sapphirine replacing spinel. All minerals are very magnesian, with XMg between 0.78 and 0.92. Bulk rock analyses suggest that precursors to the sapphirine-bearing rocks were igneous cumulates of plagioclase + olivine + hornblende + spinel. Up to 16wt% CaO does not inhibit sapphirine formation and it is the unusually Mg-rich nature of the host rocks which allows sapphirine development. The early igneous assemblage was replaced by one of cpx + sa + hb +± plag at a pressure of 9 ± 1 kbar and temperatures of 900 ± 50°C. Subsequent rapid uplift caused the instability of gt, gt + hb, hb and sa + cpx to form opx + plag ± sp ± sa symplectites.

Notes: The Gran Paradiso basement complex of the French and Italian Alps is composed of metasediments, termed the gneiss minuti, and metabasic rocks, both of which are intruded by a late Hercynian granite. The Bonneval gneiss, which crops out at the western edge of the complex, is composed of highly deformed metasediments, volcanics and volcaniclastic rocks. Eclogites, now highly altered, occur in the metabasic rocks. Kyanite and blue-green amphibole are locally present in the gneiss minuti and aegirine plus riebeckite occur in the Bonneval gneiss. A moderately high pressure - low temperature metamorphic event of probable Alpine age occurred in the basement complex. This metamorphic event differs from that in the overlying Sesia unit and ophiolites of the Schistes lustrés nappe in being at lower pressures (below the ab = jd100+ qz transition) and post-dating the major (D2A) deformation. The origin of the metamorphism is discussed and interpreted as a probable consequence of the overlying nappe pile which was emplaced during the D2A event. Subsequent greenschist facies metamorphism in the basement complex is a consequence of thermal relaxation during uplift.

Notes: Abstract. A method for the quantitative analysis of the spatial relations of minerals is described. Dispersed distributions are formed by annealing and destroyed in post-tectonic migmatization. Aggregate distributions characterize solid-state differentiation, whereas leucosomes formed in systems of high fluid:rock ratio (in the examples studied, anatectic melts) show random distributions.Quantitative textural analysis can be used to indicate whether migmatization was post-tectonic or earlier, though caution is necessary if post-migmatite cooling is slow or if there is some minor deformation. More importantly, it can be used to discriminate melt-present from melt-absent leucosomes; this is exemplified by a suite of metamorphic and anatectic migmatites from the Scottish Caledonides.The textural evolution of anatexites with increasing melt percentage is traced. Initial feldspar porphyroblastesis occurs by Ostwald ripening via grain boundary melts; subsequently ophthalmites develop with fabrics and chemistry inherited from the palaeosome. At greater than 30% melt these inherited fabrics are wholly destroyed. Deformation prompts segregation into melanosome and leucosome; resultant leucosomes contain no inherited crystals. The scale of anatectic systems is fixed at the point at which segregation begins; ophthalmites provide evidence for melt and crystal transfer beyond original palaeosome boundaries. In contrast, metamorphic migmatites are necessarily small-scale systems because of diffusive constraints, and melanosomes are invariably produced.

Notes: The oligoclase-biotite zone of the Bessi area, central Shikoku is characterized by sodic plagioclase (XCa= 0.10–0.28)-bearing assemblages in pelitic schists, and represents the highest-grade zone of the Sanbagawa metamorphic terrain. Mineral assemblages in pelitic schists of this zone, all with quartz, sodic plagioclase, muscovite and clinozoisite (or zoisite), are garnet + biotite + chlorite + paragonite, garnet + biotite + hornblende + chlorite, and partial assemblages of these two types. Correlations between mineral compositions, mineral assemblages and mineral stability data assuming PH2O = Psolid suggests that metamorphic conditions of this zone are about 610 ± 25°C and 10 ± 1 kbar.Based upon a comparative study of mineralogy and chemistry of pelitic schists in the oligoclase-biotite zone of the Sanbagawa terrain with those in the New Caledonia omphacite zone as an example of a typical high-pressure type of metamorphic belt and with those in a generalized‘upper staurolite zone’as an example of a medium-pressure type of metamorphic belt, progressive assemblages within these three zones can be related by reactions such as:

Notes: An assemblage consisting of corundum, sapphirine, spinel, cordierite, garnet, biotite and bronzite is described from the Messina area of the Limpopo Mobile Belt, and consideration given to its petrogenesis. Various geothermometers and geobarometers have been applied in an attempt to determine the temperatures and pressures of metamorphism.A former coexistence of garnet and corundum is suggested to have developed during the earliest high pressure phase of the metamorphism, where temperatures exceeded 800°C and pressures as high as 10kbar may have been experienced. Subsequently, continuous retrograding reactions from medium pressure granulite facies at about 800°C and 8kbar towards amphibolite facies generated spinel, cordierite, sapphirine and possibly also bronzite. The most notable reaction was probably of the form: garnet + corundum = cordierite + sapphirine + spinel.

Notes: A review of currently available information relevant to the Basal Gneiss Complex (BGC) of Western South Norway, combined with the authors’own observations, leads to the following conclusions.1. Most of the BGC consists of Proterozoic crystalline rocks and probably subordinate Lower Palaeozoic cover.2. The last major deformation of these rocks was during the Caledonian orogeny and involved large-scale thrusting, recumbent folding and doming. The structural development of the BGC is closely tied in with that of the Caledonian allochthon.3. The whole eclogite-bearing part of the BGC has suffered a high pressure metamorphism with conditions of between 550°C, 12.5 kbar (Sunnfjord) and about 750°C, 20 kbar (Møre og Romsdal) at the metamorphic climax.4. This metamorphism was of Caledonian age, probably rather early in the Caledonian tectonic history of the BGC and is considered to have been a rather transient event.By setting these conclusions in a framework provided by geophysical evidence for the deep structure of the crust in southern Norway we have constructed a geotectonic model to explain the recorded metamorphic history of the BGC. It is suggested that considerable crustal thickening was caused by imbrication of the Baltic plate margin during continental collision with the Greenland plate. This resulted in high pressure metamorphism in the resulting nappe stack. Progradation of the suture caused underthrusting of the Baltic foreland below the eclogite-bearing terrain causing it to emerge at the Earth's surface, aided by tectonic stripping and erosion.Application of isostacy equations to the model shows that eclogites can be formed by in-situ metamorphism in crustal rocks and reappear at the land surface above a normal thickness of crust in a single orogenic episode of approximately 65-70 Ma duration.

Notes: Detailed geochronological, structural and petrological studies reveal that the geological evolution of the Field Islands area, East Antarctica, was substantially similar to that of the adjacent Archaean Napier Complex, though with notable differences in late and post Archaean times. These differences reflect the area's proximity to the Proterozoic Rayner Complex and consequent vulnerability to tectonic process involved in the formation of the latter. Distinctive structural features of the Field Islands are (1) consistent development of a discordant, pervasive S3 axial-plane foliation; (2) re-orientation of S3 axial planes to approximate to the subsequent E-W tectonic trend of the nearby Rayner Complex; (3) selective retrogression by a post-D3 static thermal overprint; and (4) relatively common development of retrogressive, E-W-trending, mylonitic shear zones.Peak metamorphic conditions in excess of 800°C at 900 ± 100 M Pa (9 kbar) were attained at one locality following, but probably close to the time of D2 folding. D3 took place in late Archaean times when metamorphic temperatures were about 650°C and pressures were about 600 MPa (6 kbar). Later, temperatures of 600 ± 50°C and pressures of 700 MPa (7kbar) were attained in an amphibolite-facies event, presumably associated with the widespread granulite to amphibolite-facies metamorphism and intense deformation involved in the formation of the Rayner Complex at about 1100 Ma. The area was subsequently subjected to near-isothermal uplift.Rb-Sr isotopic data indicate that the pervasive D3 fabric developed at about 2400–2500 Ma, and this age can be further refined to 2456+8-5 Ma by concordant zircon analyses from a syn-D3 pegmatite. All zircons were affected by only minor (〈7–10%) Pb loss and/or new zircon growth during the Rayner event at about 1100Ma. Thus the 450–850 μg/gU concentrations of these zircons were too low to cause sufficient lattice damage over the 1350 Ma (from 2450 Ma) for excessive Pb to be lost during the 1100 Ma event. The emplacement of pegmatite at 522 ± 10 Ma substantially changed the Rb-Sr systematics of the only analysed rock that developed a penetrative fabric during the 1100 Ma event. Monazite in this pegmatite contains an inherited Pb component, which probably resides in small opaque inclusions.A good correlation is found between Rb-Sr total-rock ages and rock fabric. U-Pb zircon intercepts with concordia also mostly correspond to known events. However, in one example a near perfect alignment of zircon analyses, probably developed by mixing of unrelated components, produced concordia intercepts that appear to have no direct geochronological significance.

Notes: Cool smoke treatments were applied to unmined Eucalyptus marginata (jarrah) forest soils, rehabilitated bauxite mine soils, and broadcast seed to determine if enhancement in germination could be effected with a view toward maximizng the establishment of species in bauxite mines in Western Australia.Forest sites showed a 48-fold increase in total germinants from the soil seed bank when treated with aerosol smoke. Newly returned bauxite mine soils showed a greater than threefold increase in total germinants after the same treatment. There were also significant increases in the number of species germinating in response to the aerosol smoke treatment in both the forest and the mined soils. Similarly, application of smoked water to the soil seed bank in previously mined sites elicited a significant positive germination response, increasing total germinants and species numbers by 56 and 33%, respectively.Treatment of mixed seed lots with aerosol smoke before broadcast resulted in highly significant improvement in germination when compared to untreated seed. Both total number of germinants, and number of species emerging from mined sites were positively influenced (85% and 34% increases, respectively).Ten target species were used to determine the relative effectiveness of different methods of smoke treatment on the germination of broadcast seed. Nine of the species involved displayed a promotive effect with at least two of the treatments. Generally, however, aerosol smoking of seed before broadcast proved to be the more effective approach. As a result of these findings, all broadcast seed for use in Alcoa's bauxite mined areas in the southwest of Western Australia is now routinely smoke treated before application.

Notes: Understanding Cladium jamaicense (sawgrass) seedling establishment is an important component of an Everglades restoration program because the degree of sawgrass recovery and concurrent Typha domingensis (cattail) decline will be used to evaluate restoration success. To understand sawgrass recovery at locations with increased soil nutrients, we tested the effects of transplanting sawgrass seedlings to pots at different densities and investigated how nutrient additions affect seedling growth. Survivorship of seedlings transplanted into moist commercial potting soil at three densities ranged from 61% to 95%. After 6 months, maximum survivorship (90%) occurred at medium densities (2–4 seedlings per pot 16 cm in diameter). Nutrient additions, totaling 6.5 N g/m2, 9.8 P g/m2, 6.5 g/m2, were applied approximately 4 months after seedlings were transplanted. The biomass of the plants receiving nutrient additions (pulsed) was significantly higher (by over 30%) than plants with no nutrient addition (control). Photosynthetic rates for nutrient-enriched plants (measured 6-weeks after the nutrient additions) were significantly greater (by 32–45%) than for control plants. Instantaneous leaf water use efficiency increased significantly (by more than 20%) in pulsed plants. The results suggest that preventing root damage is crucial for the success of trans planted sawgrass seedlings and that nutrient additions enhanced seedling growth.

Notes: I evaluated responses by 16 native woody species to differential soil compaction and density of ground cover. The trees and shrubs studied represent sites in southern Illinois that commonly have restrictions to root growth from soil or drainage conditions. The study site was a restored surface coal mine in southern Illinois with a rooting medium compacted by grading and a dense ground cover of pasture species. Soil compaction was alleviated in half the study area before tree planting by mechanically ripping the soil to a depth of 1.2 m. Roots of half the trees and shrubs were dipped in a Terra® slurry before planting, and the ground cover around all planting spots was afterwards sprayed with herbicide. In year 2 after planting the ground cover in half of the unripped and half of the ripped area was further controlled by repeated application of herbicides. Ripping significantly increased height growth of all trees combined and all species individually in each year of the study. Second-year control of ground cover increased height growth of all trees combined and of seven species individually. Some species were damaged by herbicides. Terra® had little evident effect on species performance. Animal damage reduced early survival and growth, especially of Acer (maple) and Cornus (dogwood) species, and later growth of Quercus rubra (red oak). Removal of ground cover with herbicides tended to increase deer browse. Soil ripping, herbicide application, and choosing tree species unattractive to deer can be recommended to increase success in planting trees for forest restoration.

Notes: Woodlands dominated by Eucalyptus spp. in temperate southeastern and southwestern Australia have been extensively cleared for agriculture and are often badly degraded by livestock grazing. This has resulted in the loss of biodiversity and widespread land degradation. The continuing decline of these woodlands has become a concern for the conservation of biodiversity, and there is a growing interest among farmers, land managers, and researchers in developing techniques for restoring them. Currently few scientific guidelines exist for undertaking woodland restoration programs. We use a state and transition model to develop hypotheses on restoration strategies for salmon gum (Eucalyptus salmonophloia) woodlands. We consider that this approach provides a suitable framework for organizing knowledge and identifying areas where further information is needed, and hence provides a useful starting point for a restoration program. The model has the potential to provide a tool for land managers with which they can assess the action and effort needed to undertake woodland restoration in agricultural landscapes.

Notes: Most of the world's forest has been cleared, cultivated, and then often abandoned. In many instances these areas have changed to successionally arrested grasslands, shrublands, or fernlands maintained by frequent fires and high herbivore populations. Many studies have shown that various herbaceous, nitrogen-fixing legumes can protect soil surfaces, retain soil moisture, improve soil fertility, and retard ground fires. Our objective was to ascertain if some of these species can potentially inhibit herbivory and satisfactorily establish in these arrested grassland areas to serve as sites for reforestation. We evaluated the potential for four species of nitrogen-fixing legumes (Calapogonium mucunoides, Centrosema pubescens, Desmodium ovalifolium, and Pueraria phaseoloides) to establish on exposed soil within successionally arrested grasslands of Panicum maximum and Cymbopogon nardus in the central hills of Sri Lanka. Four different sites within rectangular grassland areas were cleared of graminoids and sown with seed of each legume. Half of each clearing was protected from browsing rabbits and porcupines, and half was not protected. After 6 months, certain plots were destructively sampled to determine dry biomass gain for each species and treatment. Analyses of variance were performed to test for differences among sites, treatments, and species. All three factors revealed differences, indicating that species must be matched to site. On sites with high amounts of herbivory, D. ovalifolium had the greatest dry biomass gain after 6 months of growth, possibly because of its relatively low nitrogen and moisture content. Where herbivory was absent, P. phaseoloides and C. muconoides had the greatest dry biomass gain. Dry biomass gain of all four legume ground covers was low on sites with lowest pH and nutrient concentrations. Under conditions of low relative fertility and low pH, establishment of the tested legumes failed. Though soil moisture availability was not measured, we speculate that these low fertility sites were also prone to drought. Findings support the site-specific establishment of legume species for purposes of reforestation and watershed protection in central Sri Lanka. This work is applicable to other regions particularly dominated by successionally arrested grasslands with similar circumstances in other parts of south and southeast Asia.

Notes: Oyster cultch was added to the lower intertidal fringe of three created Spartina alterniflora marshes to examine its value in protecting the marsh from erosion. Twelve 5-m-wide plots were established at each site, with six randomly selected plots unaltered (non-cultched) and cultch added to the remaining (cultched) plots. Within each cultched plot, cultch was placed along the low tide fringe of the marsh during July 1992, in a band 1.5 m wide by 0.25 m deep. Marsh-edge vegetation stability and sediment erosion were measured for each plot from September 1992 to April 1994. Significant differences (p 〈 0.05) in marsh-edge vegetation change were detected at the only south-facing site after a major southwester storm. Significantly different rates of sediment erosion and accretion also were observed at this same site. Areas upland of the marsh edge in the cultched areas showed an average accretion of 6.3 cm, while noncultched treatment areas showed an average loss of 3.2 cm. A second site, with a northern orientation, also experienced differential sediment accretion and erosion between treatment type, caused instead by boat wakes that were magnified by the abutment of a dredge effluent pipe across the entire front fringe of the site. During this period we observed significant differences in sediment accumulation, with the areas upland of the marsh edge in the cultched treatment having an average accretion of 2.9 cm and the noncultched an average loss of 1.3 cm.

Notes: Books reviewed in this article: The Significance and Regulation of Soil Biodiversity. Harold P. Collins, G. Philip Robertson, and Michael J. Klug, editors

Notes: Aggressive growth by legumes may restrict the diversity of species-rich meadows recreated on sites restored after mineral extraction. We investigated the ability of mineral nitrogen (N) applications and spring grazing to control the legume component of such meadows. The use of N suppressed Trifolium repens but had no effect on other legume species or on the species richness, diversity, or equitability of the meadow community. Spring grazing significantly reduced the yield from the legume component of the meadow. This was accompanied by an increase in the equitability index of the community, suggesting that the aggressive nature of the legumes had been checked. Spring grazing may therefore provide a means of controlling aggressive legume growth and may maintain the diversity of species-rich meadows established on restored sites.

Notes: Dogway Fork, West Virginia, is a second–order stream affected by acid precipitation. One goal of the Acid Precipitation Mitigation Program was to determine if the composition or population levels of benthic macroinvertebrates were affected by limestone neutralization of the acidic waters (pH 4.5). Two techniques were used to determine any effects: seasonal Surber samples and in situ bioassays with selected genera. Prior to treatment, macroinvertebrate densities were low but represented a diverse group of acidtolerant taxa. During treatment, fewer macroinvertebrates were collected in the treated segment than in the untreated control. This appears to be a result of a number of factors, including substrate, flows, drift, fish predation, accumulation of limestone fines, and changes in water chemistry. Bioassays suggest that the limestone fines were not directly detrimental to the organisms but may have limited available habitat in the mixing zone. Limestone treatment affected the species composition of Dogway Fork. During four years of treatment, several new acid-sensitive taxa were collected in the treated segment. Data suggest that, with continued treatment, populations of these taxa can be expected to increase.

Notes: Thrush Lake, Minnesota, was treated with limestone in 1988 to evaluate the efficacy of protective base addition against the loss of sport fisheries in a sensitive, mildly acidic lake. Prior to treatment, the lake was stressed (pH 6.46, ANC 64 μeq/L) but not severely degraded by acidic deposition and had a macrophyte community typical of lakes in northeastern Minnesota with low acid-neutralizing capacity (ANC). This paper describes the changes observed in aquatic plant communities during the 5 years after treatment, as pH and ANC slowly returned to pretreatment levels. Sphagnum platyphyllum, intolerant of non-acid conditions, was completely eliminated from the lake. The charo-phyte, Nitella, that originally shared dominance in the deep littoral zone with S. platyphyllum, decreased in importance during the first 2 years after treatment. Two vascular plants, Potamogeton pusillus and Najas flexilis, were first found in the lake the year after treatment and were abundant for 2 years after liming, probably in response to a combination of more neutral pH and reduced cover of Nitella. As the ANC and pH slowly returned to pretreatment conditions, Nitella again increased in coverage and depth range, with a concomitant decrease in P. pusillus and N. flexilis. The moss, S. platyphyllum, had not reinvaded the lake by 1993, 2 years after its dramatic decline.

Notes: This paper reviews the events leading to the channelization of the Kissimmee River, the physical, hydrologic, and biological effects of channelization, and the restoration movement. Between 1962 and 1971, in order to provide flood control for central and southern Florida, the 166 km-long meandering Kissimmee River was transformed into a 90 km-long, 10 meter-deep, 100 meter-wide canal. Channelization and transformation of the Kissimmee River system into a series of impoundments resulted in the loss of 12,000–14,000 ha of wetland habitat, eliminated historic water level fluctuations, and greatly modified flow characteristics. As a result, the biological communities of the river and floodplain system (vegetation, invertebrate, fish, wading bird, and waterfowl) were severely damaged. Following completion of the canal, the U.S. Geological Survey released a report documenting the environmental concerns associated with channelization of the river. This action led to the 1971 Governor's Conference on Water Management in South Florida that produced a consensus to request that steps be taken to restore the fish and wildlife resources and habitat of the Kissimmee basin. In 1976, the Florida Legislature passed the Kissimmee River Restoration Act. As a result, three major restoration and planning studies (first federal feasibility study [1978–1985], the Pool B Demonstration Project [1984–1990], and the second federal feasibility study [1990-present] were initiated (1) to evaluate measures and provide recommendations for restoring flood-plain wetlands and improving water quality within the Kissimmee basin, (2) to assess the feasibility of the recommended dechannelization plan, and (3) to evaluate implementation of the dechannelization plan. The recommended plan calls for the backfilling of over 35 km of C-38, recarving of 14 km of river channel, and removal of two water-control structures and associated levees. Restoration of the Kissimmee River ecosystem will result in the reestablishment of 104 km2 of river-floodplain ecosystem, including 70 km of river channel and 11,000 ha of wetland habitat, which is expected to benefit over 320 species of fish and wildlife.

Notes: Two groups of waterbirds have been chosen to assist in measuring the success of restoration of the traditional channel configuration, hydrologic regimes, and floodplain wetlands of the Kissimmee River: waterfowl (Anseriformes) and waders (Ciconiiformes). Waterfowl are dominant, swimming omnivores that use seeds, foliage, and invertebrates; waders are mainly walking predators that eat fish of various sizes. Both can be censused by well-established air and ground techniques, and both can be used to compare post-restoration with channelized or pre-channelization population data (waterfowl) or bird use of channelized versus restored wetlands (waders). In addition to use of population data, species richness and regularity of occurrence should provide a basis for assessing restoration of biological integrity. Conceptual models of avian habitat use for nesting and feeding demonstrate patterns of segregation that will aid assessments for some species. Other species show high overlap in foods and habitats and will require additional measures of response. To understand these patterns and reasons underlying waterbird use, measurements of habitat type, vegetation structure, and food resources will be essential. Integration of these high trophic-level guilds with evaluations of other system components will ensure an ecosystem perspective. Predicted responses to restoration suggest an increase in species richness and number of individuals of many species.

Notes: Survival and height growth of tree seedlings and rooted cuttings introduced into artificially shaded and unshaded plots in a degraded dry forest were measured at intervals for nine months. Ten tree species were selected to represent a range of ecological characteristics of the dry–forest plant community on St. John, U.S. Virgin Islands. Of three propagule types – seeds, seedlings, and rooted cuttings – introduced to field plots, seedlings survived best (52%) over the initial nine-month period. Cuttings of six species rooted successfully in a shadehouse, but only two of these species survived the nine–month field experiment. Seed germination was low, under 11% for eight of ten species tested, and four species did not germinate. Subsequent mortality of seedling recruits was moderately high. Plumeria alba was the only species for which seedling height growth was not significantly greater than cutting height growth. Shading treatment (25% of full sun) significantly increased seedling survivorship (p= 0.03) but suppressed growth slightly for some species. Shading enhanced survival of seedlings produced from broadcast seeds, but not seed germination. Mortality occurred during dry periods, apparently from drought stress. Results suggest (1) that seedling introductions are the preferred propagule type (over seeding or rooted cuttings) for ecological restoration of degraded tropical dry forests, and (2) that some level of shading is required to increase the survivorship of many dry-forest species or to avert complete mortality of some species. This study suggests that early secondary dry forest may be best restored by underplanting within the existing vegetation. Sufficient shading suitable for growth of native dry-forest trees may be attained using a nurse crop of fast-growing leguminous trees.

Notes: 〈blockFixed type="quotation"〉Restoration ecology… is far more than merely the development of restoration protocols. It has much to offer the rest of ecology in the very fundamental matter of clarity of definition.Allen & Hoekstra (1987)

Notes: The rehabilitation program conducted by Richards Bay Minerals (RBM) of areas exposed to opencast surface mining of sand dunes north of Richards Bay (28°43'S, 32°12'E) on the coast of northern KwaZulu-Natal Province commenced 16 years before this study and has resulted in the development of a series of known-aged stands of vegetation. By assuming that these spatially separated stands develop along a similar pathway over time, instantaneous sampling should reveal successional or other changes usually associated with aging and should provide an opportunity to evaluate the success of rehabilitation. We compare relative densities of pioneer and secondary species, species richness, and a similarity index of the herbaceous layer, tree, beetle, millipede, bird, and small-mammal communities of rehabilitating areas of known age with those of 30-year-old unmined forests and unmined forests of unknown age adjacent to the rehabilitating area. Species richness for all but the mammalian taxa increased with increasing age of rehabilitating stands. For all taxa but the mammals and herbaceous layer, the unmined stands harbored more species than the mined rehabilitating stands. The relative densities of pioneer species of all the taxa decreased with an increase in the age of rehabilitating stands, whereas those of the secondary species increased with an increase in habitat age. Similarity between unmined stands and rehabilitating stands of different ages increased with increasing regeneration age of rehabilitating stands, suggesting that rehabilitating communities, in terms of species composition and relative densities, are developing towards the status of unmined communities. Rehabilitation based on RBM's management program of limited interference is occurring and may result in the reestablishment of a coastal dune forest ecosystem. But rehabilitation resulting from succession depends on the availability of species sources from which colonization can take place. In the Richards Bay mining operation the present mining path is laid out so that such refuges are present.

Notes: We studied the effects of soil handling operations during bauxite mining and restoration on the numbers and depth distribution of seed stored in the surface soil of the jarrah forest. Germinable seed stores were determined in four sites of undisturbed forest, these same sites after clearing and burning of forest residues, in the soil immediately following the construction of topsoil stockpiles, in the respread topsoil and then after deep ripping of the respread topsoil. Average density of germinable seed at four sites prior to disturbance was 352 m−2. After clearing and burning, the seed store had decreased to a mean 74% of the original forest soil seed store density. When the top-soil was stockpiled prior to respreading, the seed content was further reduced to 31% in freshly constructed stockpiles and had declined to 13% after 10 months in the stockpiles. After ripping of the respread topsoil the seed content was 16% of the original forest seed store density. In one site where the topsoil was directly stripped and respread with no period of stockpiling but with a period of fallow, the seed store was 32% after respreading and then increased to 53% of the original forest store after ripping. This increase may have been caused by an underestimate of the reserves due to insufficient heating of the samples to break dormancy in fire-requiring species. In the forest topsoils seed was concentrated in the upper few centimeters of the soil profile, whereas after the mining and restoration operations seed was evenly distributed throughout the returned soil profile to a depth of 20 cm. Small-seeded annual species, which were common in the forest seed store, were more sensitive to the soil handing operations and declined to very low numbers, whereas hard-seeded plant species such as Acacia spp. were less affected by the soil handling operations. Implications for bauxite mine revegetation operations include the recommendation that direct return of topsoil should be carried out wherever possible with a minimum delay between clearing, stripping, respreading, and ripping.

Notes: Remote sensing provides a complementary approach to field sampling to assess whether restored wetland areas provide suitable habitat for the Light-footed Clapper Rail (Rallus longirostris levipes). Habitat requirements for the clapper rail are specified by the composition of vegetation species and their spatial extent in its nesting home range. A major salt marsh construction project has been completed at the Sweetwater Marsh National Wildlife Refuge (“the refuge”), San Diego County. In this paper we describe the application of image classification techniques to high-spatial-resolution digital video imagery (0.8-m pixels) to delimit patches of different marsh vegetation at the refuge. Using maps of vegetation types derived from multi spectral imagery, we estimated the area occupied by each vegetation type in potential clapper rail home ranges. Preliminary field-checking results indicate that this approach is an accurate, noninvasive and cost-efficient means of providing ecological information for restoration monitoring in southern California's remnant wetlands.

Notes: Research was conducted to determine the efficiency and effects of chemically treating Dogway Fork, a West Virginia stream acidified by acid precipitation. We report on the water-powered rotary drum system used to apply calcium carbonate slurry to the stream. Two companion papers cover the biological and chemical effects of this treatment. The rotary drums provided near-continuous treatment over a 4–year period. Limestone aggregate (1.3–3.8 cm) high in calcium carbonate was ground within the drums into slurry form. The relatively low cost of aggregate and its ease of storage permitted economical treatment. The system compared favorably to other types of slurry dosers. Limestone particles deposited in the stream sediment continued over time to be dissolved. They were significant in the overall dissolution efficiency of the limestone treatment. This sediment calcite also provided supplementary neutralization when high flow requirements exceeded the drum station's dosing capability.

Notes: Laurel Branch (Tennessee, U.S.A.), an acid-sensitive stream in the southern Appalachian Mountains, was limed as a part of the Acid Precipitation Mitigation Program funded by the U.S. Fish and Wildlife Service. Objectives were (1) to evaluate the effectiveness of stream liming by means of a hydropowered doser design, and (2) to monitor stream response(s) to increased pH and alkalinity. Precipitation in the region was documented to be acidic, with a mean pH of 4.54 in 1987. Preliming evaluations conducted from 1986 through 1988 depicted Laurel Branch as soft (hardness less than 5 mg/L CaCO3, pH 6.2–6.6), dilute (ionic strength less than 400 μeq/L), and lightly buffered (alkalinity less than 100 μeq/L). Because of the apparent relationship between flow and water chemistry, Laurel Branch was considered susceptible to episodic acidification caused by storms. In June 1989, a hydro–powered limestone doser was installed to treat the lower 3 km of the stream. Approximately 8.2 tonnes of crushed limestone were added during an 18–month treatment phase that concluded in December 1990. Technical and design problems with the doser reduced efficiency and limited the scale of liming through much of the first 6 months of operation. Design modifications and equipment upgrades in late 1989 corrected most of the problems and improved doser performance in 1990. No substantial chemical or biological changes were detected within the treated reach of Laurel Branch as a result of liming. Time–series statistical analyses showed small but significant changes in total alkalinity (10 μeq/L average increase) and dissolved calcium at all limed sites. pH (as hydrogen ion) increased 0.16 and 0.13 units at two limed sites that were 1 km and 2 km below the doser, respectively. At the lowermost limed site 3 km below the doser, a significant decrease in pH was detected which was probably flow-related. Mean length of age–0 (juvenile) and age-1 rainbow trout increased marginally during liming, suggesting improved fish growth, but increases were not significant. Densities of an acid-sensitive macrobenthic taxon (Baetis spp.) increased during liming, whereas densities of an acid-tolerant taxon (Leuctra spp.) remained unchanged. In general, observed biological changes were considered minimal; they were judged unrelated to liming but rather of seasonal and/or spatial origin. The regional drought of 1987 and 1988 was considered a confounding factor. With most of the baseline data collected during these years, vastly differing hydrology in 1989 and 1990 (“wet” years regionally) became problematic and may have distorted some responses and masked others. It is also possible that biological responses may have been delayed because of the small magnitude of chemical changes, particularly pH and alkalinity. A calcium mass budget estimated that up to 62% of the calcium added was accounted for in chemistry data from limed sites, with increases most visible in the spring and summer of 1990. Results indicated that, although the Laurel Branch watershed does receive acidic precipitation, current biological communities show high levels of integrity and little apparent degradation related to acidification. If watershed buffering capabilities are depleted from continued acidic deposition, however, stream biota may be at risk in the future.

Notes: We evaluated 50-year-old bottomland forests in southwestern Kentucky restored from agriculture by planting and natural regeneration in terms of their development toward mature forests. We described and compared the structure and composition of the plant communities of three stands of each type (planted, naturally regenerated, and mature). Increment cores were analyzed to reconstruct developmental trends. Future trends were predicted from analyses of the midstory and understory composition. Both planting and natural regeneration adequately replaced the structural attributes of the historical bottomland forest. The existing structural differences are expected to diminish over time. Neither regeneration method replaced the wildlife value of the mature bottomland forests due to insufficient establishment and subsequent ingrowth of heavy mast species (particularly oaks and hickories). There was evidence that the understory species compositions of the restored forest types were similar to that of the mature stand type. All forests, including the mature stands, appeared to be succeeding from hydric to mesic species compositions as a result of human-altered hydrology and natural floodplain processes. We speculate that the historical bottomland species composition will probably not persist on any of the study sites in the long term.

Notes: The semidesert grassland in southern Arizona has changed from a native grassland to a scattered Prosopis juliflora var. velutina (mesquite) woodland with an understory of African Eragrostis lehmanniana (Lehmann lovegrass) on many sites. To determine native grass restoration potential, seven species were direct seeded into E. lehmanniana stands that were left alive, burned, sprayed with an herbicide and then either left standing, or mowed. Initial native grass establishment was limited in the live standing treatment but was successful for all other treatments when either June or August sowing was followed by consistent summer precipitation and soil water availability. Four species, Bothriochloa barbinodis (cane beardgrass), Bouteloua curtipendula (sideoats grama), Digitaria californica (Arizona cottontop), and Leptochloa dubia (green spangletop) initially established most successfully, while only Muhlenbergia porteri (bush muhly) had consistently limited or no establishment. E. lehmanniana establishment from the seed bank was increased by canopy removal associated with burning. Densities of native grasses one year after successful initial establishment were much lower than that of E. lehmanniana. A possible revegetation strategy would be to spray emergent E. lehmanniana seedlings and surviving plants with an herbicide during the summer rainy season after spring burning. Native grasses could then be established by sowing in early August of that year or June and August of subsequent years until consistent precipitation produces a native grass stand.

Notes: Books reviewed in this article: Land Ecology: An Introduction to Landscape Ecology as a Base for Land Evaluation, Land Management, and Conservation. Isaac S. Zonneveld

Notes: Density, age structure, and growth rates of wild brook trout (Salvelinus fontinalis)and brown trout (Salmo trutta)in Whetstone Brook in northcentral Massachusetts were monitored for 4 years before and 3 years during limestone treatment to mitigate acidic conditions. The population density of brook trout increased significantly during treatment. Liming did not have any significant effects on the growth rates of brook trout or brown trout. Actual survival rates of brook trout and brown trout were not calculated due to the low density of both species, but more older individuals of both species were captured during the treatment period. Fulton condition factors (an index of fish condition) increased significantly for both brook trout and brown trout during treatment. Seven-day in situ bioassays of brown trout and rainbow trout demonstrated that liming improved the chemical environment for fish in Whetstone Brook. During a pretreatment bioassay in 1987, 100% rainbow trout mortality was observed at both the control and treatment stations in Whetstone Brook. Brown trout mortality was 67% in the control station and 70% in the treatment station. The pH during the 1987 bioassay averaged 4.90 in the control station and 4.99 in the treated station. During a bioassay conducted in 1990 after treatment began, rainbow trout mortality was 100% in the control station and 0% in the treatment station. Brown trout mortality was 17% in the control station and 0% in the treatment station. The pH during the 1990 bioassay averaged 5.23 in the control station and 6.60 in the treatment station. Analysis of total aluminum in the gills of fish from the 1990 bioassay revealed higher levels in fish from the control station than in those from the treatment station.

Notes: We monitored the invertebrate fauna in Whetstone Brook for 3 years before and after limestone treatment to mitigate low pH conditions caused by acid precipitation. Sampling was conducted during the spring, summer, and fall by both qualitative and quantitative methods. The fauna in Whetstone Brook in the control and treatment sections was dominated by chironomids (Diptera), simuliids (Diptera), Leuctra (Plecop-tera) and Hydropsyche (Trichoptera) in both pretreatment and treatment periods. The acid-sensitive mayfly genera Epeorus increased during liming in the treated section of the stream but also declined during the same period in the control section. Annelida increased during the treatment period in both sections of the stream. The chironomid and black fly populations were not affected by liming. The lack of impact to the black fly population was surprising because larvae are obligate filter-feeders and feed on suspended seston in the same size range as the limestone slurry that was used to treat Whetstone Brook. Treatment did not change species diversity and taxa richness in the treated section of Whetsone Brook, but both indices declined during the treatment period in the control section of Whetstone Brook. This decline was attributed to the poorer water quality of the untreated section of Whetstone Brook during the treatment period, which was due to higher-than-average precipitation. Percent community similarity analysis indicated that the community composition changed more in the treated section of Whetstone Brook than in the control section as a result of treatment. We conclude that the invertebrate fauna in the treated section of Whetstone Brook was not negatively affected by liming, but that population density and diversity did not increase.

Notes: A protective limestone treatment was applied to an acid-sensitive lake in northeastern Minnesota as part of the Acid Precipitation Mitigation Program. This 6–year study evaluated the impact of that treatment on lakes in the upper Midwest that experience episodes of acid stress but have not lost basic species integrity and community structure. Several changes in the fish community can be directly or indirectly attributed to the addition of 4.6 tonnes of calcium carbonate early in the third year of the study. An almost 30–fold increase in the population of Pimephales promelas(fathead minnow) a year after liming, based on mark-recapture estimates from trap netting and snorkeling, was attributed to a pH increase and a three-fold increase in the calcium concentration of the epilimnion. After the initial increase, the abundance of fathead minnows declined in subsequent years, as did the elevated pH and calcium concentrations. The Salvelimis fontinalis(brook trout) population also increased in the lake following application of limestone, but this was due in part to closing the lake to fishing. An increase in survival of stocked brook trout to age 1+ and an increase in growth of older brook trout after liming were attributed to the increased forage that the fathead minnows provided. Fathead minnows may have also reduced predation pressure on young brook trout by older brook trout. This study demonstrated that liming of a slightly acidic lake did not adversely affect the integrity of the fish community, and in fact may have increased the abundance and biomass of the forage fish community and indirectly increased the survival, abundance, and growth of brook trout.

Notes: Seedling emergence of 12 selected northern jarrah (Eucalyptus marginata Donn ex Smith) forest species were investigated to assist Alcoa of Australia Ltd. in maximizing the establishment of topsoil species in rehabilitated bauxite mining sites. The species, which encompassed a range of seed weights (0.024 mg to 87 mg), plant families, seed-storage types, life forms, and germination requirements, were placed on the soil surface and at depths of 1, 2, 5, 10, and 15 cm under controlled conditions in a glasshouse. Ability to emerge from deep burial was found to depend on seed size for species that annually release their seed to the topsoil but not for species that store their seed on the plant. All selected species were capable of emerging from 2 cm depth of burial, but eight of the 12 species were either unable to emerge from 5 cm or showed a significant reduction in emergence from 5 cm depth of burial compared to optimally buried seed. This group included two small-seeded species, Stylidium calcaratum and Chamaescilla corymbosa; the major forest dominant, Eucalyptus marginata; the serotinous canopy-borne seed of Hakea amplexicaulis; and the wind-dispersed seed of Xanthorrhoea gracilis. A few seeds of the legume species Kennedia coccinea, Acacia pulchella, and Bossiaea aquifolium established seedlings from depths of 15 cm. Currently, Alcoa removes the upper 15 cm of topsoil separately from the underlying soil prior to the commencement of mining. This topsoil is respread at a similar depth following mining as part of the rehabilitation procedure. It is recommended that Alcoa continue to strip topsoil to a depth of 15 cm but investigate the option of re-spreading topsoil onto rehabilitated pits at a shallower depth to maximize establishment via the soil seed bank.

Notes: We summarize the findings of a two-year study of vegetation and streambank erosion on incised streams. We conducted the first year of the research during the sixth year of a drought. During the second year of study, precipitation totals ranged from normal to 200% of normal. The focus of the study was to determine if vegetation established on a bank affects the erosion of or deposition on that bank. During the drought year, most banks showed relatively little change. During the high water year, 27% of all vegetated and 32% of all bare lower banks retreated more than 250 mm. This similarity between vegetated and unvegetated banks indicates that, on the streams studied, vegetation had little effect on bank erosion. Bank retreat was not related to near-bank velocities or to bank steepness. It is possible that herbaceous vegetation showed no effect on the incised streams because the streams were too far from a new dynamic equilibrium. The energy of the hydraulic system may have been greater than the vegetation could withstand.

Notes: We examine the nature of incentive schemes between the principal and the risk-neutral agent in the presence of the agent's limited liability and ex ante action choice. We consider alternative schemes when a simple rental contract is infeasible due to the limited liability of the agent and study the effectiveness of a performance bonus scheme in achieving the first-best outcome. We also discuss some implications of such schemes in real practices.

Notes: Recent theories of vertical integration based on incomplete contracts assume perfect competition on at least one side of the market. As a result, the make-or-buy choice has no redistributive effect and will reflect efficiency considerations only. This paper introduces imperfect competition into an otherwise standard model of a vertical relationship with noncontractable specific investments. We assume that there are a finite number of potential input suppliers with private information about their costs. We first show that a monopoly buyer of such inputs will often prefer to own the seller's assets even though it would be more efficient for the seller's assets not to be so owned. We then show that an increase in the number of potential partners on either side of the market reduces this inclination towards vertical integration. With perfect competition on either side of the market, the make-buy decision will reflect only efficiency considerations.

Notes: The paper studies managerial incentives in a model where managers choose product market strategies and make takeover decisions. The equilibrium contract includes an incentive to increase the firm's sales, under either quantity or price Competition. This result contrasts with previous findings in the literature, and hinges on the fact that when managers are more aggressive, rival firms earn lower profits and thus are willing to sell out at a lower price. However, as a side effect of such a contract, the manager might undertake unprofitable takeovers.

Notes: For U.S. futures exchanges, controlling costs while maintaining market performance is an ongoing, difficult challenge. New market realities have made that challenge even more daunting in recent years as costs have escalated, competition has expanded, and the role of information technology has expanded. It is always difficult for regulatory statutes to keep pace with ever-changing markets. Futures markets are no exception. The basic statutory framework represented by the Commodity Exchange Act (CEA) was enacted in 1922, over seventy years ago. In order to maintain appropriate regulatory balance, periodic review and reform has been essential over the years. Our current federal regulatory systems were built for different markets with different competitive realities than we face today. Reforming the CEA to take into account those new market realities is vital to the survival of U.S. futures exchanges.

Notes: We develop a game-theoretic version of the right-to-manage model of firm-level bargaining where strategic interactions among firms are explicitly recognized. Our main aim is to investigate how equilibrium wages and employment react to changes in various labor and product market variables. We show that our comparative statics results hinge crucially on the strategic nature of the game, which in turn is determined by the relative bargaining power of unions and managers.

Notes: We develop a simple model in which there is both interfirm (or intraproduct) and intrafirm (or interproduct) competition. The purpose is to develop a classificatoy framework in order to understand product-range or diversification decisions alongside conventional competition. The equilibrium outcomes commonly involve a limited range of the available goods being produced. Deterrence equilibria and other strategic actions are also examined.

Notes: DeGraba and Postlewaite (1992) show that the seller of a durable input can solve the time inconsistency problem by offering most-favored-customer (MFC) protection to buyers. McAfee and Schwartz (1994) show that if a supplier sells inputs to competing firms using two-part tariffs, MFC protection that allows a firm to replace its contract with a contract executed by any other firm will not solve the commitment problem, and argue this implies managers cannot use MFCs as a strategic commitment device in complex contracting situations. This paper shows that if the profits of the seller and the buyers are monotonic in each term of the contract, then applying MFC protection to each term of a contract allows a manager to solve his commitment problem in complex contacting situations. We show that “standard” contract arrangements (two-part tariffs, declining block tariffs, and royalties as a percentage of sales) meet this condition.

Notes: Food-related illness in the United States is estimated to affect over six million people per year and cost the economy several billion dollars. These illnesses and costs could be reduced if minimum infectious doses were established and used as the basis of regulations and monitoring. However, standard methodologies for dose-response assessment are not yet formulated for microbial risk assessment. The objective of this study was to compare dose response models for food-borne pathogens and determine which models were most appropriate for a range of pathogens. The statistical models proposed in the literature and chosen for comparison purposes were log-normal,(19) log-logistic,(17) exponential,(7,9,17)ß-Poisson(7,9,18) and Welbull-Gamma.(3) These were fit to four data sets also taken from published literature, Shigella fiexneri,(9,12,13)Shigella dysenteriae,(9,11)Campylobacter jejuni,(15,16) and Salmonella typhosa,(7,14) usingthe method of maximum likelihood. The Weibull-gamma, the only model with three parameters, was also the only model capable of fitting all the data sets examined using the maximum likelihood estimation for comparisons. Infectious doses were also calculated using each model. Within any given data set, the infectious dose estimated to affect one percent of the population ranged from one order of magnitude to as much as nine orders of magnitude, illustrating the differences in extrapolation of the dose response models. More data are needed to compare models and examine extrapolation from high to low doses for food-borne pathogens.

Notes: Environmental managers are increasingly charged with involving the public in the development and modification of policies regarding risks to huma health and the environment. Involving the public in environmental decision making first requires a broad understanding of how and why the public perceives various risks. The Savannah River Stakeholder Study was conducted withthe purpose of investigating individual, economic, and social characteristics of risk perceptions among those living near the Savannah River Nuclear Weapons Site. A number of factors were found to impact risk perceptions among those living near the site. One's estimated proximity to the site and relative river location surfaced as strong determinants of risk perceptions among SRS residents. Additionally, living in a quality neighborhood and demonstrating a willingness to accept health risks for economic gain strongly abated heightened risk perceptions.

Notes: Five atmospheric transport models were evaluated for use in Phase I1 ofthe Historical Public Exposures Studies at the Rocky Flats Plant. Models included a simple straight-line Gaussian plume model (ISCST2), several integrated puff models (RATCHET, TRIAD, and INPUFF2), and a complex terrain mode (TRAC). Evaluations were based on how well model predictions compared with sulfur hexafluoride tracer measurements taken in the vicinity of Rocky Flats in February 1991. Twelve separate tracer experiments were conducted, eac lasting 9 hr and measured at 140 samplers in arcs 8 and 16 km from the release point at Rocky Flats. Four modeling objectives were defined based on the endpoints of the overall study: (1) the unpaired maximum hourly average concentration, (2) paired time-averaged concentration, (3) unpaired time-averaged concentration, and (4) arc-integrated concentration. Performance measures were used to evaluate models and focused on the geometric mean and standard deviation of the predicted-to-observed ratio and the correlation coefficient between predicted and observed concentrations. No one model consistently outperformed the others in all modeling objectives and performance measures. About 75% of the maximum hourly concentration predictions were within a factor of 5 of the observations. About 64% of the paired and 80% of the unpaired time-averaged model predictions were within a factor of 5 of theobservations. The overall performance of the RATCHET model was somewhat better than the other models. All models appeared to experience difficulty defining plume trajectories, which was attributed to the influence of multilayered flow initiated by terrain complexities and the diurnal flow patterns characteristic of the Colorado Front Range.

Notes: Calculation of accident dose-risk estimates with the RADTRAN code requires input data describing the population likely to be affected by the plumeof radioactive material (RAM) released in a hypothetical transportation accident. In the existing model, population densities within 1/2 mile (0.8 km)of the route centerline are tabulated in three ranges (Rural, Suburban, andUrban). These population densities may be of questionable validity since the plume in the RADTRAN analysis is assumed to extend out to 120 km from thehypothetical accident site. We present a GIs-based population model which accounts for the actual distribution of population under a potential plume, and compare accident-risk estimates based on the resulting population densities with those based on the existing model. Results for individual points along a route differ greatly, but the cumulative accident risks for a sample route of a few hundred kilometers are found to be comparable, if not identical. We conclude, therefore, that for estimation of aggregate accident risks over typical routes of several hundred kilometers, the existing, simpler RADTRAN model is sufficiently detailed and accurate.

Notes: This paper discusses a number of the key challenges to the acceptance and aplication of probabilistic risk analysis (PRA). Those challenges include:(a) the extensive reliance on subjective judgment in PRA, requiring the development of guidance for the use of PRA in risk-informed regulation, and possibly the development of “robust” or “reference” prior distributions to minimize the reliance on judgment; and (b) the treatment of human perfor-mance in PRA, including not only human errorperse but also management and organizational factors more broadly. All of these areas are seen as presentinginteresting research challenges at the interface between engineering and other disciplines.

Notes: Rational decision making requires that the total uncertainty about a variate of interest (a predictand) be quantified in terms of a probability distribution, conditional on all available information and knowledge. Supposethe state-of-knowledge is embodied in a deterministic model, which is imperfect and outputs only an estimate of the predictand. Fundamentals are presented of two Bayesian methods for producing a probabilistic forecast via anydeterministic model. The Bayesian Processor of Forecast (BPF) quantifies the total uncertainty in terms of a posterior distribution, conditional on model output. The Bayesian Forecasting System (BFS) decomposes the total uncertainty into input uncertainty and model uncertainty, which are characterized independently and then integrated into a predictive distribution. The BFS is compared with Monte Carlo simulation and “ensemble forecasting” technique, none of which can alone produce a probabilistic forecast that quantifies the total uncertainty, but each can serve as a component of the BFS.