Susan B. Norton

The effects of mountaintop mines and valley fills on the physicochemical quality of stream ecosystems in the central Appalachians: a review.

This review assesses the state of the science on the effects of mountaintop mines and valley fills (MTM-VF) on the physicochemical characteristics of streams in the central Appalachian coalfields of West Virginia, Kentucky, Virginia and Tennessee, USA. We focus on the impacts of mountaintop removal coal mining, which involves removing all - or some portion - of the top of a mountain or ridge to expose and mine one or more coal seams. Excess overburden is disposed in constructed fills in small valleys adjacent to the mining site. MTM-VF leachate persistently increases the downstream concentrations of major ions. Conductivity is a coarse measure of these ions, which are dominated by a distinct mixture of SO(4)(2-), HCO(3)(-), Ca(2+) and Mg(2+), that reflects their source, the oxidation of pyrite to form acid followed by neutralization of the acidity by carbonate minerals within the valley fills. This results in neutral to alkaline pHs, a range at which many metals are relatively insoluble. Other compounds within coal or overburden are solubilized and occur at elevated albeit lower concentrations, including K(+), Na(+), Cl(-), Se and Mn. In terms of physical characteristics, the valley fills act like headwater aquifers, baseflows increase in streams below valley fills and water temperatures exhibit reduced seasonal variation. Peak discharges may be increased in response to intense precipitation events, because of compaction of base surfaces of the MTM-VF areas, but newer approaches to reclamation reduce this compaction and may ameliorate these peak flows. Although the sedimentation pond is intended to capture fine particles that wash downstream from the valley fill, some studies found increased fine sediments in streams downstream from valley fills. However, a proportion of these fines may be eroded from stream banks rather than the valley fills. This is probably a result of the alterations in stream flows.

Algae–P relationships, thresholds, and frequency distributions guide nutrient criterion development

Abstract We used complementary information collected using different conceptual approaches to develop recommendations for a stream nutrient criterion based on responses of algal assemblages to anthropogenic P enrichment. Benthic algal attributes, water chemistry, physical habitat, and human activities in watersheds were measured in streams of the Mid-Atlantic Highlands region as part of the Environmental Monitoring and Assessment Program of the US Environmental Protection Agency. Diatom species composition differed greatly between low- and high-pH reference streams; therefore, analyses for criterion development were limited to a subset of 149 well-buffered streams to control for natural variability among streams caused by pH. Regression models showed that TP concentrations were ∼10 μg/L in streams with low levels of human activities in watersheds and that TP increased with % agriculture and urban land uses in watersheds. The 75th percentile at reference sites was 12 μg TP/L. Chlorophyll a and ash-free dry mass increased and acid and alkaline phosphatase activities decreased with increasing TP concentration. The number of diatom taxa, evenness, proportion of expected native taxa, and number of high-P taxa increased with TP concentration in streams. In contrast, the number of low-P native taxa and % low-P individuals decreased with increasing TP. Lowess regression and regression tree analysis indicated nonlinear relationships for many diversity indices and attributes of taxonomic composition with respect to TP. Thresholds in these responses occurred between 10 and 20 μg/L and helped justify recommending a P criterion between 10 and 12 μg TP/L to protect high-quality biological conditions in streams of the Mid-Atlantic Highlands.

Comparing responses of macroinvertebrate metrics to increasing stress

Metrics characterizing the benthic macroinvertebrate assemblages in wadeable streams in the Mid-Atlantic region of the United States were analyzed to explore the relative responses of the metrics to different types of anthropogenic stress. The data used in our study were collected by the US Environmental Protection Agency Environmental Monitoring and Assessment Program from 1993 to 1996. Regression models were developed relating metric values at reference sites to natural sources of variability. These models were then used to predict reference values at test sites. Test site metric observations were scaled by subtracting the predicted reference value and dividing by the standard deviation of residuals at reference sites. Stressor–response relationships for each scaled metric were then estimated using generalized additive models. Metric responses to 4 groups of stressors (nutrient enrichment, habitat degradation, elevated metals concentrations, and elevated ion concentrations) were different. The proportional abundance of tolerant taxa was the most sensitive indicator of nutrient enrichment and habitat degradation, whereas Ephemeroptera richness was the most sensitive indicator of elevated metals or ion concentrations.

CADDIS: The Causal Analysis/Diagnosis Decision Information System

Biological monitoring and assessment methods have become indispensable tools for evaluating the condition of aquatic and terrestrial ecosystems. When an undesirable biological condition is observed (e.g., a depauperate fish assemblage), its cause (e.g., toxic substances, excess fine sediments, or nutrients) must be determined in order to design appropriate remedial management actions. Causal analysis challenges environmental scientists to bring together, analyze, and synthesize a broad variety of information from monitoring studies, models, and experiments to determine the probable cause of ecological effects. Decision-support systems can play an important role in improving the efficiency, quality and transparency of causal analyses.

The Science and Philosophy of a Method for Assessing Environmental Causes

ABSTRACT When an environmental impairment has been identified, it becomes necessary to identify the cause so that an appropriate action can be planned. However, causation is difficult to establish—both conceptually and in practice. To ensure that the U.S. Environmental Protection Agencys (USEPAs) method for causal assessment is appropriate and defensible, we reviewed concepts of causation from philosophers, statisticians, epidemiologists, and others. This article summarizes the results of that review and explains how it relates to the USEPAs method. We include a five-step process: (1) identify alternative candidate causes; (2) logically eliminate when possible; (3) diagnose when possible; (4) analyze the strength of evidence for remaining candidate causes; and (5) identify the most likely cause. We also encourage three practices: (1) use a consistent process; (2) do not claim proof of causation; and (3) document the evidence and inferences. This approach allows assessors to identify the most likely cause or, failing that, to reduce the set of possible causes and identify information needs for another iteration of causal assessment.

Causal characteristics for ecoepidemiology.

ABSTRACT We suggest that there are six fundamental characteristics of causation: time order, co-occurrence, preceding causation, sufficiency, interaction, and alteration. The cause precedes the effect (time order). The cause co-occurs with the unaffected entity in space and time (co-occurrence). Causes and their effects are the result of a web of causation (preceding causation). The intensity, frequency, and duration of the cause are adequate and the susceptible entity can exhibit the type and magnitude of the effect (sufficiency). The cause effectively interacts with the entity in a way that induces the effect (interaction). And, the entity is changed by the interactions with the cause (alteration). In contrast to Hills criteria, the causal characteristics are distinct from the: (1) evidence that is used to document causal characteristics, (2) sources of information used to develop the evidence, and (3) qualities used to evaluate evidence of causal characteristics and body of evidence for the causal relationship. Evidence of causal characteristics can form the basis for assessments of epidemiological studies and can structure an explanatory narrative that is causally relevant and substantive. Six core characteristics may be easier to organize, evaluate, communicate, and for decision-makers to assimilate, remember, and inspire action.

The Evolution of Frameworks for Ecological Risk Assessment from the Red Book Ancestor

The risk assessment framework presented in the National Research Council (NRC) Red Book played a key role in the development of ecological risk assessment (ERA). ERA frameworks have, however, developed along their own pathway and have significantly extended concepts that were introduced in the Red Book. When the U.S. Environmental Protection Agency (EPA) commissioned the Oak Ridge National Laboratory (ORNL) in 1981 to develop and apply methods for ERA, the work focused on probabilistic analysis, since that seemed to be the essence of risk. When the Red Book appeared, it suggested that the use of a logical framework to guide the process was also an important aspect of risk assessment. Therefore, the ORNL investigators developed a framework similar to the Red Book framework but more suited to ERA. When EPA initiated a project to develop an official EPA framework for ERA, the ORNL framework was presented in a colloquium intended to obtain input from scientists outside EPA. Later, the NRC sponsored a workshop on ecological risk assessment that was attended by the leaders of the EPA framework project. The report produced from the workshop endorsed the concept of an ERA framework and proposed an integrated framework that included both human health and ecological risk assessment. The framework ultimately adopted by EPA extended the NRC and ORNL frameworks by providing a detailed description of the process and showing how the process could be applied to a broad range of situations. Since then, various ERA frameworks have been developed for use in other countries and for specific situations.

Ecological risk assessment: A scientific perspective

Abstract Ecological risk assessment is becoming an increasingly important tool for ranking, assessing, reducing, and managing environmental risks. To pro- vide Agency-wide guidance in this area in the U.S., EPAs Risk Assessment Forum has begun a multi-year guidelines development program. The first step in this program was the publication of the report “Framework for Ecological Risk Assessment” which describes the principles, concepts, terminology, and structure of ecological risk assessments.

Minimizing Cognitive Errors in Site-Specific Causal Assessments

Interest in causal investigations in aquatic systems has been a natural outgrowth of the increased use of biological monitoring to characterize the condition of resources. Although biological monitoring approaches are critical tools for detecting whether effects are occurring, they do not identify the cause of the observed effects. Formal approaches to causal evaluation can provide a mechanism to build on expert knowledge, increasing the likelihood that remedial efforts will achieve the desired environmental improvement. This paper examines how formal approaches to causal investigations minimize common errors. We reviewed common cognitive errors reported in the literature, and compared them with considerations suggested for strength-of-evidence approaches. Many of the causal considerations are directed toward distinguishing spurious correlations from true causal relationships. However, this is only one type of error; others include hypothesis dependence, confirmation bias, hypothesis tenacity and anchoring. We suggest three general principles for minimizing error in site-specific investigations: (1) Conduct the causal evaluation as a fair, transparent comparison among alternatives; (2) Carefully describe and quantify the conjunction of cause and effect; and (3) Consider that conjunction between cause and effect is spurious, or that a real conjunction was masked.

The U.S. Environmental Protection Agency's Stressor Identification Guidance: A Process for Determining the Probable Causes of Biological Impairments

The United States Environmental Protection Agency (USEPA) has ongoing programs to encourage the evaluation of stream conditions based on biological indicators. Bioassessments reveal impairments but do not identify causes of impairments, a necessary step in the restoration of aquatic life. Furthermore, changes in biological condition are often caused by multiple stressors (chemical, physical, biological). To address this need, the USEPA has developed guidance to identify probable causes of biological impairments in aquatic ecosystems and to provide a structure for organizing the scientific evidence to make a credible case. The concepts and organizational structure of the process have potential applications to most ecoepi-demiological investigations.