ALBERT

Notes: The Susunai Complex of southeast Sakhalin represents a subduction-related accretionary complex of pelitic and basic rocks. Two stages of metamorphism are recognized: (1) a local, low-P/T event characterized by Si-poor calcic amphiboles; (2) a regional, high-P/T event characterized by pumpellyite, actinolite, epidote, sodic amphibole, sodic pyroxene, stilpnomelane and aragonite. The major mineral assemblages of the high-P/T Susunai metabasites contain pumpellyite + epidote + actinolite + chlorite, epidote + actinolite + chlorite, epidote + Na-amphibole + Na-pyroxene + chlorite-(-haematite. The Na-amphibole is commonly magnesioriebeckite. The Na-pyroxene is jadeite-poor aegirine to aegirine-augite. Application of empirically and experimentally based thermobarometers suggests peak conditions of T= 250–300C, P= 4.7–6 kbar. Textural relationships in Susunai metabasite samples and a petrogenetic grid calculated for the Fe3+-rich basaltic system suggest that pressure and temperature increased during prograde metamorphism.

Notes: In the Llano Uplift of central Texas (USA), prograde homogenization of garnet growth zoning took place during moderate-to high-pressure dynamothermal metamorphism over a narrow temperature range near the transition from the amphibolite to the granulite facies. This subtle record of early dynamothermal metamorphism survived subsequent static metamorphism at low pressures in the middle-amphibolite facies, despite the destruction of most high-pressure mineral assemblages that originated in the early metamorphic episode. Geographically systematic variations in the degree of homogenization indicate that the uplift as a whole underwent high-pressure metamorphism, in accord with emerging tectonic models for the mid-Proterozoic evolution of the southern margin of the North American continent.

Notes: Successful long-term wetland restoration efforts require consideration of hydrology and currounding land use during the site selection process. This article describes an approach to initial site selection in the San Luis Rey River watershed in southern California that uses watershed-level information on basin topography and land cover to rank the potential suitability of all sites within a watershed for either preservation of restoration. This approach requires the use of a geographic information system (GIS)to map relative wetness and land cover within a watershed. Relative potential wetness values were derived from U.S. Geological Survey (USGS) 30-m digital elevation models by calculating the flow that would potentially accumulate at all 30-m × 30-m pixels within the watershed. Land cover was derived from a Landsat scene covering the 1500 Km2 study area. We ranked sites (contiguous groups of pixels 〉 1 ha with similar land cover) in terms of their potential for restoration or preservation based on their wetness values (Iow, medium, and high), size, and proximity to existing riparian vegetation. Sites with medium or high wetness values and extant vegetation were identified as potential preservation sites. Agiricultural or barren sites with medium to high wetness were identified as potential restoration sites. Approximately 5500 ha (3.67% of the total watershed) were prioritized for preservation or resloration.

Notes: This historical and conceptual overview of riparian ecosystem restoration discusses how riparian ecosystems have been defined, describes the hydrologic, geomorphic, and biotic processes that create and maintain riparian ecosystems of the western USA, identifies the main types of anthropogenic desturbances occurring in these ecosystems, and provides an overview of restoration methods for each disturbance type. We suggest that riparian ecosystems consist of two zones: Zone I occupies the active floodplain and is frequently inundated and Zone II extends from the active floodplain to the valley wall. Successful restoration depends n understanding the physical and biological processes that influence natural riparian ecosystems and the types of disturbance that have degraded riparian areas. Thus we recommend adopting a process-based approach for riparian restoration. Disturbances to riparian ecosystems in the western USA result from streamflow modifications by dams, reservoirs, and diversions; stream channelization; direct modification of the riparian ecosystem; and watershed disturbances. Four topics should be addressed to advance the state of science for restoration of riparian ecosys-tems: (1) interdisciplinary approaches, (2) a unified framework, (3) a better understanding of fundamental riparian ecosystem processes, and (4) restoration po-tential more closely related to disturbance type. Three issues should be considered regarding the cause of the degraded environment: (1) the location of the causative disturbance with respect to the degraded riparian area, (2) whether the disturbance is ongoing or can be elim-inated, and (3) whether or not recovery will occur nat-urally if the disturbance is removed.

Notes: A two-stage system for selecting stream reaches and riparian communities for restoration was applied to the 80-km San Luis Rey River below the Lake Henshaw dam in southern California. In the first satge, data from topographic quadrangles and aerial photographs were analyzed to define and classiy reaches. These analyses concluded that (1) 28 km of the river and adjacent floodplain were suitable for second-stage evaluation of restoration needs and (2) 32 km met criteria for reference conditions at the stream reach scale and should be protected from further impacts. The remaining 20 km of the river and floodplain were considered unsuitable for restoration to reach-scale reference conditions; individual sites may be restored under existing regulatory review. Second-stage field sampling provided data on vegetation and floodplain landforms and substrate from more thatn 3000 plots within the 28 km of river and 1120 ha of floodplain selected for further Study. Classification of floristic samples stratified by landform/substrate class indicated six primary riparian communities on the floodplain, some associated with particular floodplain landform/substrate classes and others ubiquitous. Reference conditions for these communities were interpreted from the data. There were two major departures from reference conditions: tree-dominated communities were less extensive than historic levels and exotic plants had significantly invaded some landforms and communities, displacing natural com-munities. General goals would include restoration of tree communities and removal of exotics, with further consideration of site-specific objectives. The results included estimates of the areas by community type re-quiring restoration. The approach was developed for streams in the semi-arid western United States, but it may be adapted for use elsewhere.

Notes: This study compares the results of Olson and Harris (1997) and Russell et al. (1997) in their work to prioritize sites for riparian restoration in the San Luis Rey River watershed. Olson and Harris defined reaches of the mainstem and evaluated the relative potential for restoration and protection based on cover of natural vegetation, land use, and connectivity. Then they used data on geomorphic conditions, plant species composition, and community structure to prescribe strategies for restoration. Russell et al. used a modeling approach within a geographic information system to combine data on wetness and land use/land cover to identify areas with potential for protection and restoration. They prioritized the areas based on patch size and proximity to extant riparian habitat. The main-stem and associated floodplain defined by Olson and Harris was more than twice the size of the area defined by Russell et al., because Olson and Harris considered the entire valley floor, whereas Russell et al. used a wetness index to identify saturated zones within the floodplain. For seven of the twelve management units delineated along the mainstem, the two studies agreed on a strategy of restoration or protection. They differed on two. No comparison could be made of the three units for which Olson and Harris used project review, a unique category. Agreement of the results is due to the similarity of criteria used to identify and rank sites for protection and restoration; disagreement is due primarily to the level of resolution of the data. Both approaches have potential for use in watershed-level planning. The predictive power of the two approaches may be maximized when they are used in a complementary fashion.

Notes: We present a conceptual model for identifying restoration sites for riparian wetlands and discuss its application to reaches within the Upper Arkansas River basin in Colorado. The model utilizes a Geographic Information System (GIS) to analyze a variety of spatial data useful in characterizing geomorphology, hydrology, and vegetation of riparian wetland sites. The model focuses on three basic properties of riparian wetland sites: relative soil moisture, disturbance regime, and vegetative characteristics. A relative wetness index is used to define nominal soil moisture classes within the watershed. These classes generally coincide with uplands (low), channel margins (moderate), and channels or open water (high). Vegetative conditions are characterized using color infrared aerial photographs. Land cover types are grouped into five major land cover classes: riparian, moist herbaceous, bare ground, upland, and open water. Disturbance regime is characterized by a reach-based index of specific power (ω). Preliminary results indicate that reaches within the Upper Arkansas River basin can be classified as high energy (ω≥ 8 W/m2) or low energy (ω≤ 3W/m2), using discharge estimates that reflect the 10-year flood event. Field surveys of channel and floodplain conditions show that high-energy reaches (ω≥ 8 W/m2) are characterized by sites where the channel occupies a large proportion of the valley bottom. By contrast, low-energy reaches (ω≤ 3 W/m2) are characterized by meandering channels with wide alluvial valleys. Restoration potential is evaluated as a combination of nominal scores from wetness, land cover, and disturbance indices. Application of these methods to field sites within the Upper Arkansas River basin identifies a wide range of riparian wetland sites for preservation or restoration. Potential sites within identified reaches are prioritized using size and proximity criteria.

Notes: A major goal of population biologists involved in restoration work is to restore populations to a level that will allow them to persist over the long term within a dynamic landscape and include the ability to undergo adaptive evolutionary change. We discuss five research areas of particular importance to restoration biology that offer potentially unique opportunities to couple basic research with the practical needs of restorationists. The five research areas are: (1) the influence of numbers of individuals and genetic variation in the initial population on population colonization, establishment, growth, and evolutionary potential; (2) the role of local adaptation and life history traits in the success of restored populations; (3) the influence of the spatial arrangement of landscape elements on metapopulation dynamics and population processes such as migration; (4) the effects of genetic drift, gene flow, and selection on population persistence within an often accelerated, successional time frame; and (5) the influence of interspecific interactions on population dynamics and community development. We also provide a sample of practical problems faced by practitioners, each of which encompasses one or more of the research areas discussed, and that may be solved by addressing fundamental research questions.

Notes: Books reviewed in this article: Biotic Interactions and Global Change P. M. Kareiva, J. G., Kingsolver, and R. B. Huey, editors Defining Sustainable Forests G.H. Aplet, N. Johnson, J. T. Olson, and V. A. Sample, editors

Notes: Despite this nation's massive effort during the past 90 years to build levees throughout the upper Mississippi Basin, mean annual flood damage in the region has increased 140% during that time. These levees exacerbate the flood damage problem by increasing river stage and velocity. Thus, rather than continuing to rely on structural solutions for flood control, it is time to develop a comprehensive flood management strategy that includes using wetlands to intercept and hold precipitation where it falls and store flood waters where they occur. History testifies to the truth of this premise: it was the rampant drainage of wetlands in the nineteenth century that gave rise to many of today's water resources management problems. The 1993 flood verifies the need for additional wetlands: the amount of excess water that passed St. Louis during the 1993 flood would have covered a little more than 13 million acres —half of the wetland acreage drained since 1780 in the upper Mississippi Basin. By strategically placing at least 13 million acres of wetlands on hydric soils in the basin, we can solve the basin's flooding problems in an ecologically sound manner.

Notes: Physiological and vegetative performances of three prairie grasses were investigated to assess their adaptation to soil conditions at two strip mine sites and a nearby railroad prairie. Additionally, rhizomes of the species were transplanted to a pot experiment and grown in both field soil and greenhouse potting medium to investigate the extent to which plants are limited under field conditions. Field measurements of photosynthetic rate and stomatal conductance to water vapor were made on the three species monthly from May to late August. Gas exchange measurements on potted plants were made biweekly from early May to mid-July. In September, vegetative and flowering characteristics were measured on both field and potted plants. Field gas exchange rates were highest at one of the mines. Sorghastrum nutans had the highest rates at the mine sites, whereas Panicum virgatum had the highest rates at the prairie site. Potted plants from the prairie site usually exhibited the highest gas exchange rates, and Sorghastrum nutans had higher rates than Panicum virgatum and Andropogon gerardii. Potted plants in field soil generally had higher gas-exchange rates than plants growing in greenhouse potting medium, and potted plants had higher gas-exchange rates than field-grown plants. Vegetative and reproductive performance of field plants was highest at one of the mine sites. Potted plants in greenhouse medium had up to twice the vegetative and reproductive output as potted plants in field soil or plants growing in the field. The physiological and vegetative performance of these species indicates that they are well adapted to the soil conditions at these strip mine sites, and that they are a viable alternative to nonnative plantings for restoration.

Notes: This paper describes a practical technique, tested experimentally, for rehabilitating degraded semiarid landscapes in Australia. This rehabilitation technique is based on the ecological principle that semiarid landscapes are spatially organized as patchy, source-sink systems; this patchy organization functions to conserve limited water and nutrients within the system. The aim was to rebuild vegetation patchiness, lost through decades of utilization of these landscapes as rangelands. Patches were reconstructed from large tree branches and shrubs obtained locally and placed in elongated piles along contours. These piles of branches were very effective in recreating productive soil patches within the landscape, as described in part I of this study. These new patchy habitats promoted the establishment and growth of perennial grasses. Although the foliage cover of these grasses declined into a drought, which started before the end of the experiment, plant survivorship remained high. This suggests that patches also function as refugia for organisms during droughts. The patches of branches remained robust and functional, even under grazing impacts, although plant growth and survival were significantly higher within an ungrazed paddock than in a grazed paddock.

Notes: When the transportation risk posed by shipments of hazardous chemical and radioactive materials is being assessed, it is necessary to evaluate therisks associated with both vehicle emissions and cargo-related risks. Diesel exhaust and fugitive dust emissions from vehicles transporting hazardous shipments lead to increased air pollution, which increases the risk of latent fatalities in the affected population along the transport route. The estimated risk from these vehicle-related sources can often be as large or larger than the estimated risk associated with the material being transported. In this paper, data from the U.S. Environmental Protection Agency's Motor Vehicle-Related Air Toxics Study are first used to develop latent cancer fatality estimates per kilometer of travel in rural and urban areas forall diesel truck classes. These unit risk factors are based on studies investigating the carcinogenic nature of diesel exhaust. With the same methodology, the current per-kilometer latent fatality risk factor used in transportation risk assessments for heavy diesel trucks in urban areas is revised and the analysis expanded to provide risk factors for rural areas and all diesel truck classes. These latter fatality estimates may include, but are not limited to, cancer fatalities and are based primarily on the most recent epidemiological data available on mortality rates associated with ambient air PM-10 concentrations.

Notes: Risk assessors often use different probability plots as a way to assessthe fit of a particular distribution or model by comparing the plotted points to a straight line and to obtain estimates of the parameters in parametric distributions or models. When empirical data do not fall in a sufficiently straight line on a probability plot, and when no other single parametricdistribution provides an acceptable (graphical) fit to the data, the risk assessor may consider a mixture model with two component distributions. Animated probability plots are a way to visualize the possible behaviors of mixture models with two component distributions. When no single parametric distribution provides an adequate fit to an empirical dataset, animated probability plots can help an analyst pick some plausible mixture models for the data based on their qualitative fit. After using animations during exploratory data analysis, the analyst must then use other statistical tools, including but not limited to: Maximum Likelihood Estimation (MLE) to find the optimal parameters, Goodness of Fit (GoF) tests, and a variety of diagnostic plots to check the adequacy of the fit. Using a specific example with two LogNormal components, we illustrate the use of animated probability plots asa tool for exploring the suitability of a mixture model with two component distributions. Animations work well with other types of probability plots, and they may be extended to analyze mixture models with three or more component distributions.

Notes: For carcinogens, this paper provides a quantitative examination of the roles of potency and weight-of-evidence (WOE) in setting permissible exposure limits (PELs) at the U.S. Occupational Safety and Health Administration (OSHA) and threshold limit values (TLVs) at the private American Conference of Governmental Industrial Hygienists (ACGIH). On normative grounds, both of these factors should influence choices about the acceptable level of exposures. Our major objective is to examine whether and in what ways these factors have been considered by these organizations. A lesser objective is to identify outliers, which might be candidates for further regulatory scrutiny. Our sample (N=48) includes chemicals for which EPA has estimated a unit risk as a measure of carcinogenic potency and for which OSHA or the ACGIH has a PEL or TLV. Different assessments of the strength of the evidence of carcinogenicity were obtained from EPA, ACGIH, and the International Agency for Research on Cancer. We found that potency alone explains 49% of the variation in PELs and 62% of the variation in TLVs. For the ACGIH, WOE plays a much smaller role than potency. TLVs set by the ACGIH since 1989 appear to be stricter than earlier TLVs. We suggest that this change represents evidence that the ACGIH had responded to criticisms leveled at it in the late 1980s for failing to adopt sufficiently protective standards. The models developed here identify 2-nitropropane, ethylene dibromide, and chromium as having OSHA PELs significantly higher than predicted on the basis of potency and WOE.

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: 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: 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.

Notes: This article describes an application of a method for assessing risks associated with the introduction of an organism into a new environment. The test organism was a binucleate Rhizoctonia fungal isolate that has potential for commercial development as a biological control agent for damping-off diseases in bedding plants. A test sample of host plant species was selected using the centrifugal phylogenetic host range principles, but with an emphasis on economic species. The effect of the fungus on the plant was measured for each species and expressed on a logarithmic scale. The effects on weights of shoots and roots per container were not normally distributed, nor were the effects on the number of plants standing (those which survived). Statements about the effect on the number standing and the shoot weight per container involved using the observed (empirical) distribution. This is illustrated with an example. Problems were encountered in defining the population of species at risk, and in deciding how this population should be formally sampled. The limitations of the method are discussed.

Notes: The heuristic-systematic information processing model (HSM) holds that individuals will use one or both of these modes of information processing when attempting to evaluate information in order to arrive at a judgment. Systematic processing is defined by effortful scrutiny and comparison of information, whereas heuristic processing is defined by the use of cues to amve more easily at a judgment. Antecedents to the two processing modes include information sufficiency, motivation, and self-efficacy. Structural equation modeling is used to examine competing configuration of this model and to evaluate the model as appropriate for predicting risk judgment. The model also is evaluated across three groups that vary with respect to their level of concern. These analyses are executed within a case study involving an epidemiological investigation of a suspected cancer cluster. The analysis confirms the HSM's theoretically proposed structure and shows it to be a useful vehicle for evaluating risk judgment. In the overall analysis, antecedent variables generally function as specified by theory. Systematic processing is predicted by greater motivation. Heuristic processing is predicted by information sufficiency. Self-efficacy is a significant predictor of both processing modes. And heuristic processing is shown to be associated with judgment of less risk. However, when the analysis is contrasted across three groups (those concerned about cancer, not concerned and uncertain) it is shown that the model is significantly more robust for the uncertain group. This finding may have implications for the use of the HSM in risk research specifically, and in field research generally.

Notes: South Carolina has issued fish consumption advisories for the Savannah River based on mercury and radionuclide levels. We examine differences in fishing rates and fish consumption of 258 people interviewed while fishing along the Savannah River, as a function of age, education, ethnicity, employment history, and income, and test the assumption that the average consumption of fish is less than the recreational value of 19 kg/year assumed by risk assessors. Ethnicity and education contributed significantly to explaining variations in number of fish meals per month, serving size, and total quantity of fish consumed per year. Blacks fished more often, ate more fish meals of slightly larger serving sizes, and consumed more fish per year than did Whites. Although education and income were correlated, education contributed most significantly to behavior; people who did not graduate from high school ate fish more often, ate more fish per year, and ate more whole fish than people who graduated from high school. Computing consumption of fish for each person individually indicates that (1) people who eat fish more often also eat larger portions, (2) a substantial number of people consume more than the amount of fish used to compute risk to recreational fishermen, (3) some people consume more than the subsistence level default assumption (50 kglyear) and (4) Blacks consume more fish per year than Whites, putting them at greater risk from contaminants in fish. Overall, ethnicity, age, and education contributed to variations in fishing behavior and consumption.

Notes: The association between daily fluctuations in ambient particulate matter and daily variations in nonaccidental mortality have been extensively investigated. Although it is now widely recognized that such an association exists, the form of the concentration-response model is still in question. Linear, no threshold and linear threshold models have been most commonly examined. In this paper we considered methods to detect and estimate threshold concentrations using time series data of daily mortality rates and air pollution concentrations. Because exposure is measured with error, we also considered the influence of measurement error in distinguishing between these two completing model specifications. The methods were illustrated on a 15-year daily time series of nonaccidental mortality and particulate air pollution data in Toronto, Canada. Nonparametric smoothed representations of the association between mortality and air pollution were adequate to graphically distinguish between these two forms. Weighted nonlinear regression methods for relative risk models were adequate to give nearly unbiased estimates of threshold concentrations even under conditions of extreme exposure measurement error. The uncertainty in the threshold estimates increased with the degree of exposure error. Regression models incorporating threshold concentrations could be clearly distinguished from linear relative risk models in the presence of exposure measurement error. The assumption of a linear model given that a threshold model was the correct form usually resulted in overestimates in the number of averted premature deaths, except for low threshold concentrations and large measurement error.

Notes: Facility-specific information on pollution was obtained for 36 coke plants and 46 oil refineries in the United States and matched with information on populations surrounding these 82 facilities. These data were analyzed to determine whether environmental inequities were present, whether they were more economic or racial in nature, and whether the racial composition of nearby communities has changed significantly since plants began operations. The Census tracts near coke plants have a disproportionate share of poor and nonwhite residents. Multivariate analyses suggest that existing inequities are primarily economic in nature. The findings for oil refineries are not strongly supportive of the environmental inequity hypothesis. Rank ordering of facilities by race, poverty, and pollution produces limited (although not consistent) evidence that the more risky facilities tend to be operating in communities with above-median proportions of nonwhite residents (near coke plants) and Hispanic residents (near oil refineries). Over time, the racial makeup of many communities near facilities has changed significantly, particularly in the case of coke plants sited in the early 1900s. Further risk-oriented studies of multiple manufacturing facilities in various industrial sectors of the economy are recommended.

Notes: We investigated the way results of human health risk assessments are used, and the theory used to describe those methods, sometimes called the “NAS paradigm.” Contrary to a key tenet of that theory, current methods have strictly limited utility. The characterizations now considered standard, Safety Indices such as “Acceptable Daily Intake,”“Reference Dose,” and so on, usefully inform only decisions that require a choice between two policy alternatives (e.g., approve a food additive or not), decided solely on the basis of a finding of safety. Riskis characterized as the quotient of one of these Safety Indices divided by an estimate of exposure: a quotient greater than one implies that the situation may be considered safe. Such decisions are very widespread, both in the U. S. federal government and elsewhere. No current method is universal; different policies lead to different practices, for example, in California's “Proposition 65,” where statutory provisions specify some practices. Further, an important kind of human health risk assessment is not recognized by this theory: this kind characterizes risk as likelihood of harm, given estimates of exposure consequent to various decision choices. Likelihood estimates are necessary whenever decision makers have many possible decision choices and must weigh more than two societal values, such as in EPA's implementation of “conventional air pollutants.” These estimates can not be derived using current methods; different methods are needed. Our analysis suggests changes needed in both the theory and practice of human health risk assessment, and how what is done is depicted.

Notes: The prominent role of animal bioassay evidence in environmental regulatory decisions compels a careful characterization of extrapolation uncertainties. In noncancer risk assessment, uncertainty factors are incorporated to account for each of several extrapolations required to convert a bioassay outcome into a putative subthreshold dose for humans. Measures of relative toxicity taken between different dosing regimens, different endpoints, or different species serve as a reference for establishing the uncertainty factors. Ratios of no observed adverse effect levels (NOAELs) have been used for this purpose; statistical summaries of such ratios across sets of chemicals are widely used to guide the setting of uncertainty factors. Given the poor statistical properties of NOAELs, the informativeness of these summary statistics is open to question. To evaluate this, we develop an approach to “calibrate” the ability of NOAEL ratios to reveal true properties of a specified distribution for relative toxicity. A priority of this analysis is to account for dependencies of NOAEL ratios on experimental design and other exogenous factors. Our analysis of NOAEL ratio summary statistics finds (1) that such dependencies are complex and produce pronounced systematic errors and (2) that sampling error associated with typical sample sizes (50 chemicals) is nonnegligible. These uncertainties strongly suggest that NOAEL ratio summary statistics cannot be taken at face value; conclusions based on such ratios reported in well over a dozen published papers should be reconsidered.

Notes: We compare the regulatory implications of applying the traditional (linearized) and exact two-stage dose-response models to animal carcinogenic data. We analyze dose-response data from six studies, representing five different substances, and we determine the “goodness- of-fit” of each model as well as the 95% confidence lower limit ofthe dose corresponding to a target excess risk of 10-5 (the target risk doseTRD). For the two concave datasets, we find that the exact model gives a substantially better fit to the data than the traditional model, and that the exact model gives aTRD that is an order of magnitude lower than that given by the traditional model. In the other cases, the exact model gives a fit equivalent to or better than the traditional model. We also show that although the exact two-stage model may exhibit dose-response concavity at moderate dose levels, it is always linear or sublinear, and never supralinear, in the low-dose limit. Because regulatory concern is almost always confined to the low-dose region extrapolation, supralinear behavior seems not to be of regulatory concern in the exact two-stage model. Finally, we find that when performing this low-dose extrapolation in cases of dose-response concavity, extrapolating the model fit leads to a more conservative TRD than taking a linear extrapolation from 10% excess risk. We conclude with a set of recommendations.

Notes: The characterization and treatment of uncertainty poses special challenges when modeling indeterminate or complex coupled systems such as those involved in the interactions between human activity, climate and the ecosystem. Uncertainty about model structure may become as, or more important than, uncertainty about parameter values. When uncertainty grows so large that prediction or optimization no longer makes sense, it may still be possible to use the model as a “behavioral test bed” to examine the relative robustness of alternative observational and behavioral strategies. When modelsmust be run into portions of their phase space that are not well understood, different submodels may become unreliable at different rates. A common example involves running a time stepped model far into the future. Several strategies can be used to deal with such situations. The probability of model failure can be reported as a function of time. Possible alternative “surprises” can be assigned probabilities, modeled separately, and combined. Finally, through the use of subjective judgments, one may be able to combine, and over time shift between models, moving from more detailed to progressively simpler order-of-magnitude models, and perhaps ultimately, on to simple bounding analysis.

Notes: In any model the values of estimates for various parameters are obtained from different sources each with its own level of uncertainty. When the probability distributions of the estimates are obtained as opposed to point values only, the measurement uncertainties in the parameter estimates may be addressed. However, the sources used for obtaining the data and the models used to select appropriate distributions are of differing degrees of uncertainty. A hierarchy of different sources of uncertainty based upon one's ability to validate data and models empirically is presented. When model parameters are aggregated with different levels of the hierarchy represented, this implies distortion or degradation in the utility and validity of the models used. Means to identify and deal with such heterogeneous data sourcesare explored, and a number of approaches to addressing this problem is presented. One approach, using Range/confidence Estimates coupled with an Information Value Analysis Process, is presented as an example.

Notes: Variability arises due to differences in the value of a quantity among different members of a population. Uncertainty arises due to lack of knowledge regarding the true value of a quantity for a given member of a population. We describe and evaluate two methods for quantifying both variability and uncertainty. These methods, bootstrapsimulation and a likelihood-based method, are applied to three datasets. The datasetsinclude a synthetic sample of 19 values from a Lognormal distribution, a sample of nine values obtained from measurements of the PCB concentration in leafy produce, and asample of five values for the partitioning of chromium in the flue gas desulfurization system of coal-fired power plants. For each of these datasets, we employ the two methods to characterize uncertainty in the arithmetic mean and standard deviation, cumulative distribution functions based upon fitted parametric distributions, the 95th percentile of variability, and the 63rd percentile of uncertainty for the 81st percentile of variability. The latter is intended to show that it is possible to describe anypoint within the uncertain frequency distribution by specifying an uncertainty percentile and a Variability percentile. Using the bootstrap method, we compare results based upon use of the method of matching moments and the method of maximum likelihood for fitting distributions to data. Our results indicate that with only 5-19 data pointsas in the datasets we have evaluated, there is substantial uncertainty based upon random sampling error. Both the boostrap and likelihood-based approaches yield comparable uncertainty estimates in most cases.

Notes: Evaluating alternatives for restoring the Everglades involves analysis of a complex ecological and economic system for which current knowledge is limited. Uncertain benefits and impacts are analyzed probabilistically in this paper, following otherwise accepted principles of net present value (NPV) analysis. Ecological benefits and impacts were considered in monetary terms. Probabilities for selected uncertain parameters were found by maximizing entropy. The first ecological risk conceptual model for the Everglades ecosystem was developed to show ecological interactions. “Current Plans” for restoration involve discharge of phosphorus-enriched water from artificial wetlands to relatively pristine Everglades marshes for 3–10 years, risking conversion of the ecosystem to a eutrophic cattail marsh. For two of the three areas studied, alternative “Bypass Plans” were shown to avoid the loss of up to 3000 acres of sawgrass marsh at a cost that is probabilistically justified by the value of the ecosystem preserved. Sensitivity of the results to projected ecological changes, eutrophic marsh valuation, natural marsh valuation, and future values as represented in the discount rate, was examined.

Notes: The motivation of the present work is to provide an auxiliary tool for the decision-maker (DM) faced with predictive model uncertainty. The tool is especially suited for the allocation of R&Dresources. When taking decisions under uncertainties, making use of the output from mathematical or computational models, the DM might be helped if the uncertainty in model predictions be decomposed in a quantitative-rather than qualitativefashion, apportioning uncertainty according to source. This would allow optimal use of resources to reduce the imprecision in the prediction. For complex models, such a decomposition of the uncertainty into constituent elements could be impractical as such, due to the large number of parameters involved. If instead parameters could be grouped into logical subsets, then the analysis could be more useful, also because the decision maker might likely have different perceptions (and degrees of acceptance) for different kinds of uncertainty. For instance, the decomposition in groups could involve one subset of factors for each constituent module of the model; or one set for the weights, and one for the factors in a multicriteria analysis; or phenomenological parameters of the model vs. factors driving the model configuratiodstructure aggregation level, etc.); finally, one might imagine that a partition of the uncertainty could be sought between stochastic (or aleatory) and subjective (or epistemic) uncertainty. The present note shows how to compute rigorous decomposition of the output's variance with grouped parameters, and how this approach may be beneficial for the efficiency and transparency of the analysis.

Notes: The concept of vulnerability of complex industrial systems is defined and discussed in relation to risk and system survivability. The discussion is illustrated by referring to a number of previous industrial accidents. The various risk factors, or threats, influencing an industrial system's vulnerability are classified and discussed. Both internal and external threats are covered. The general scope of vulnerability analysis is compared to traditional risk analysis approaches and main differences are illustrated. A general procedure for vulnerability analysis in two steps, including building of scenarios and preparation of relevant worksheets, is described and discussed.