bluuebunny/crossref_metadata_2025 huggingface dataset:
A Cooperative Study for the Evaluation of Crack Arrest Toughness of RPV Materials in Japan
Authors: Sakai Y , Yagawa G , Ando Y
Published: February 2009

Results are presented from an investigation of crack arrest toughness Ka, on ASTM A533B Class 1 and A508 Class 3 steels using ASTM-proposed specimens and ESSO specimens. The results show that the values of Ka, measured in accordance with the ASTM test method, increased with an increase in test temperature, and that the size requirements in the method were appropriate to obtain valid values of plane-strain crack arrest toughness KIa. It was also found that the ASTM and ESSO tests lead to about the same crack arrest toughness values when applied to large specimens of the same size. The lower bound of KIa data was significantly under that of KIc data on the test materials, though both bounds were well over the American Society of Mechanical Engineers (ASME) KIR curve.
Experimental Evaluation of an Equation Applicable for Surface Cracks Under Tensile or Bending Loads
Authors: Reuter WG , Epstein JS
Published: February 2009

If a structural material behaves in a linear elastic manner, it is generally assumed that plane-strain fracture toughness (KIc) may be used with applicable solutions to predict conditions for catastrophic fracture. There have been a few instances where the adequacy of this approach has been verified, but these evaluations were conducted for specific applications. This paper evaluates an approach using specimens containing surface cracks, with substantial variations in crack size and shape, and loaded by either tension or bending. Test results are used to compare the critical stress-intensity factor (Kcrit) with KIc. Moiré interferometry is used to obtain KI at the free surface for comparison with the calculated result.
A Three-Dimensional Weight Function Method
Authors: Banks-Sills L
Published: February 2009

In this investigation, an exact three-dimensional weight function is developed for the elliptical crack family. Closed form expressions for the weight function of the penny-shaped and elliptical crack in an infinite body subjected to symmetric applied stresses are obtained. Several loadings are considered that lead to exact solutions which agree with those in the literature. Since crack-opening displacements for more complicated crack geometries do not appear in the literature, an approximate weight function is proposed. When applied to the geometries with known solutions, excellent agreement is obtained. When employed to determine the stress-intensity factor for a semielliptical and quarter-elliptical crack in a plate subjected to bending stresses, it produces results which are good for short cracks.
Constraint-Loss Model for the Growth of Surface Fatigue Cracks
Authors: Van Stone RH , Gilbert MS , Gooden OC , Laflen JH
Published: February 2009

As surface flaws grow in high-strength nickel-base superalloys, the growth along the free surface (dc/dN) can be much slower than growth in the depth direction (da/dN), even after accounting for variations in K along the crack front. This behavior reduces the crack aspect ratio (c/a) and can result in the formation of stable shear lips at the free surface during fatigue crack growth. Trantina et al. recently performed elastic-plastic finite-element analyses of surface cracks which showed that as the applied stress approached the elastic limit, a relatively large region of constraint loss was observed where the crack front intersects the free surface. This concept was used to develop a constraint-loss modification to the Newman-Raju K solution for the surface flaw problem. This model has been applied to physically small surface crack growth in the advanced nickel-base superalloy René 95. The predicted results match the dc/dN data, which are slower than and not parallel to the corresponding da/dN-K data. This model has been combined with a dual-Walker exponent approach to model nonzero stress (R) ratios. This methodology has been used to predict the residual lives of surface flaws growing in both uniform and nonuniform stress fields within a factor of two of the experimentally observed lives. This model has also been successfully applied to small surface flaws and can predict the lives of cracks with depths (a) as small as 65 μm (0.0025 in.).
Mixed-Mode Stress-Intensity Factor Solutions for Offshore Structural Tubular Joints
Authors: Rhee HC , Salama MM
Published: February 2009

Accurate calculations of the stress-intensity factors (K) are essential for assessment of the integrity of structural components containing crack-like defects. For the complex tubular joints used in the construction of offshore structures, accurate K solutions do not exist. Only limited results using empirically derived K values are available in the literature. This paper presents a methodology for the mixed-mode K solutions for a surface crack at the weld toe of tubular joints. Example solutions were developed for tubular X-joints under brace tension and in-plane bending using three-dimensional finite-element analyses. The complex finite-element mesh was generated using a special mesh generator. The K values were obtained from the displacement solutions of quarter-point crack-tip elements. The results demonstrate the validity of the solution scheme and contribute to the understanding of the crack-tip behavior of tubular joints.
Review of Pressurized-Water-Reactor-Related Thermal Shock Studies
Authors: Cheverton RD , Iskander SK , Ball DG
Published: February 2009

Flaw behavior trends associated with pressurized thermal shock (PTS) loading of pressurized water reactor (PWR) pressure vessels have been under investigation at Oak Ridge National Laboratory (ORNL) for approximately twelve years. During that time, eight thermal shock experiments with thick-walled steel cylinders were conducted as a part of the investigations. These experiments demonstrated, in good agreement with linear elastic fracture mechanics (LEFM), crack initiation and arrest, a series of initiation/arrest events with deep penetration of the wall, long crack jumps without significant dynamic effects at arrest, arrest in a rising stress-intensity-factor (KI) field, extensive surface extension of an initially short and shallow flaw, and warm prestressing with KI ⩽ 0. This information was used in the development of a fracture mechanics model that is being used extensively in the evaluation of the PTS issue.
Pressurized Thermal Shock Experiments with Thick Vessels
Authors: Bryan RH , Merkle JG , Nanstad RK , Robinson GC
Published: February 2009

A 148-mm-thick pressure vessel containing a long axial flaw was subjected to a combined loading of internal pressure and thermal shock. The experiment was performed to investigate the effects of loading sequence on initiation of brittle fracture and the behavior of a crack propagating into ductile regions. Two crack initiation and arrest episodes were generated, in addition to several phases of warm prestressing. Warm prestressing was shown to be effective in inhibiting initiation of cleavage fracture. A crack arrest was observed 88 K above the reference nil-ductility transition temperature (RTNDT) with a stress-intensity factor of 299 MPa √m.
Threshold and Nonpropagation of Fatigue Cracks Under Service Loading
Authors: Castro DE , Marci G , Munz D
Published: February 2009

New testing conditions for determination of fatigue threshold and a new interpretation of this parameter make it amenable to general fatigue life design. To distinguish between the terms, the conditions for nonpropagating fatigue cracks were called the fatigue tolerance range and denoted as ΔKT. The conditions for nonpropagating fatigue cracks were investigated on Inconel 617 alloy in the range of Kmax between 10 to 50 MPa m1/2 under four different types of fatigue loading conditions. It was found that ΔKT decreases with increasing Kmax. Furthermore, ΔKT decreases with increasing prior amplitude, ΔKpr, up to a certain amplitude, ΔKs, at which the effect of prior amplitudes reaches saturation. For Inconel 617 alloy, ΔKs is between 5 and 7 MPa m1/2 at Kmax = 10 MPa m1/2 and approximately 5 MPa m1/2 at Kmax = 35 MPa m1/2. The test result on saturation behavior at Kmax = 10 MPa m1/2 suggests an influence of closure on the effects of prior amplitudes. The results are explained by differing damage states in the near region of the crack front introduced by Kmax and ΔK of the prior fatigue cycles.
Fatigue Crack Growth Rate Properties of SA508 and SA533 Pressure Vessel Steels and Submerged-Arc Weldments in a Pressurized Water Environment
Authors: Logsdon WA , Liaw PK , Begley JA
Published: February 2009

The Stage II fatigue crack growth rate (FCGR) properties of four base materials (SA508 Class 2a; SA533 Grade A, Class 2; SA508 Class 3a; and SA533 Grade B, Class 2 steels) and two automatic submerged-arc weldments (SA508 Class 2a and SA533 Grade A, Class 2) were developed in a pressurized water environment at 288°C (550°F) and 13.8 MPa (2000 psi) at load ratios of 0.20 and 0.50. The pressurized water environment FCGR properties of these four pressure vessel steels and two submerged-arc weldments were generally conservative compared with the appropriate American Society of Mechanical Engineers (ASME) Section XI water environment reference curve. The growth rate of fatigue cracks in the four base materials, however, was considerably faster in the pressurized water environment than in a corresponding 288°C (550°F) baseline air environment. The growth rate of fatigue cracks in the two submerged-arc weldments was also accelerated in the pressurized water environment but to a lesser degree than that demonstrated by the corresponding base materials. In the air environment, fatigue striations were observed independent of the material and load ratio, while in the pressurized water environment some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials in comparison with the weldments was attributed to a different sulfide composition and morphology.
Near-Threshold Crack Growth in Nickel-Base Superalloys
Authors: Van Stone HR , Krueger DD
Published: February 2009

The influence of stress ratio on the elevated-temperature crack growth behavior of the nickel-base superalloys René 95 and Alloy 718 is discussed. The near-threshold and Region II crack growth behavior of a wide variety of microstructures for each alloy are explained using phenomenological descriptions of closure, that is, K-dependent or K-independent closure. K-dependent closure is the type of closure observed for nickel-base superalloys where increasing the R-ratio causes a uniform lateral shift of the entire fatigue crack growth curve. K-independent closure is the type commonly reported for steels and titanium alloys where increasing the R-ratio has a larger influence on near-threshold crack growth than on Region II crack growth. The existence of K-dependent closure in nickel-base superalloys results in microstructurally sensitive crack growth rates, even at high R-ratios. This permits the use of K-based crack growth prediction techniques and simplifies alloy and process development for applications having complex loading spectra.
Effect of Frequency on Fatigue Crack Growth Rate of Inconel 718 at High Temperature
Authors: Weerasooriya T
Published: February 2009

Fatigue crack growth was studied at 650°C as a function of frequency for several ratios of minimum-to-maximum stress intensity (R) and for two values of maximum stress-intensity factor (Kmax), for a nickel-base superalloy, Inconel 718. All the tests were conducted under computer control at constant Kmax. Crack lengths were monitored at low frequencies from compliance calculations based on crack-mouth opening displacement measurements. At higher frequencies, crack length was measured using a d-c electric potential system. It was found that fatigue crack growth rate can be characterized in three distinct frequency regions. These three regions represent fully cycle-dependent, mixed, and fully time-dependent crack growth behavior, and each region can be modeled by a power law function. Observation of micromechanisms support the existence of these three different modes of crack growth.
Aquatic Toxicology: Ten Years in Review and a Look at the Future
Authors: Parrish PR , Dickson KL , Hamelink JL , Kimerle RA , Macek KJ , Mayer FL , Mount DI
Published: February 2009

This symposium marks the tenth time that we have gathered as a group of professional scientists who share common goals and ideas concerning the protection of our nation's aquatic resources. This tenth symposium seems like a fitting time to reflect on our origins, our successes, and our plans for the future. To that end, several people who have been instrumental in shaping the science of aquatic toxicology and hazard (risk) assessment were invited to present their views on the growth of this science and their ideas about its future. This paper is, then, a collection of those viewpoints, which are set down in writing so that others may benefit from the experience of the authors and so that newcomers to this field may benefit by knowing about the roots of aquatic toxicology and hazard assessment. The fact that the science has persisted and grown over the past ten years is a tribute to all those who have contributed their time, energy, and intellect.
Genetically Engineered Microorganisms in the Aquatic Environment: Environmental Safety Assessment
Authors: Molak V , Stara JF
Published: February 2009

The deliberate release of genetically engineered microorganisms (GEMs) into the environment is a promising approach to the amelioration of environmental problems such as pollution and pest control.

GEMs may find their way into the aquatic environment, (oceans, streams, groundwaters, lakes, wastewaters, and sludges) either by direct release into that environment or, after uses on land, via surface runoff and soil seepage into groundwaters, streams, lakes, and estuaries. Since experience with the deliberate release of GEMs is very limited, it is necessary to develop approaches for risk assessment of the potential adverse effects that could be caused by the introduction of a large number of novel microorganisms into the aquatic environment. The accepted approach to risk assessment (hazard identification, exposure, and dose-response assessment, leading to risk characterization) has been used to develop models for risk assessment of the deliberate release of GEMs into the aquatic environment. The new concept introduced in this risk assessment is that of “critical mass,” defined as the number of GEMs applied at a specific site that would result in replacement of endogenous microorganisms. This “critical mass” would depend both on the properties of GEMs and on the number and properties of endogenous microorganisms at the site of GEMs application. An experimental assessment of critical mass may be possible by using aquatic microcosms corresponding to the aquatic environment into which GEMs would be released.
Paleoecology and Environmental Analysis
Authors: Cowgill UM
Published: February 2009

A discussion is presented which shows the types of information that may be gleaned from the chemical, mineralogical, and biological analyses of lake muds. Illustrations are taken from a variety of studies carried out in various countries.

Substantial rises in the concentration of sulfur in the recently deposited mud as well as in the surface water of Linsley Pond (North Branford, Connecticut) are indicative of industrial expansion in the region over the past five decades. Similarly, stack emissions produced by the combustion of fossil fuels have caused rises in sulfur concentrations and subsequent changes in pH in unbuffered waters of Southern and Southwestern Scandinavia. These phenonmena have brought about shifts in population size and distribution among the lake plankton.

Recent technological growth has resulted in a progressive increase in mercury in the sediments of Lake Windermere, United Kingdom, Lake Huleh, Israel, and Lake Biwa, Japan. No doubt reflecting man's global activities, similar rises in concentrations of lead, cadmium, and silver have been noted in recently deposited muds in various sections of the world. The steady rise of phthalates noted in recently deposited sediments is indicative of the advent of the use of plastics in the many areas of human endeavor.

To ascertain which of the various hypotheses advanced to explain the sudden collapse of the ancient Mayan culture in Central America were valid, a series of lake cores were taken in Guatemala and subjected to chemical and biological analyses. The ecologically oriented hypothesis appears to be invalid. Furthermore, these studies showed that a high agricultural civilization developed and that under modern conditions a larger agricultural population employing indigenous methods can be supported. In addition, these investigations showed that early man changed a savanna to a tropical forest and that his activities brought about only a small increase in the erosion rate.

Additionally, paleoecological methods may be used to elucidate past climates, the advent of agriculture in a region, processes of plant selection and domestication, effects of slash and burn agriculture, the size of one time plankton populations, the chemical concentration of the atmosphere in ancient times, the history of a landscape, and the effect of road building on nearby lakes.
The Use of Subfossil Benthic Invertebrates in Aquatic Resource Management
Authors: Crisman TL
Published: February 2009

Since the beginning of this century, benthic invertebrates have been used as biotic indicators of water quality. The objective of any lake management plan is both to identify the principal watershed disturbances/practices contributing to a lake problem and to rank their importance as part of a cost-effective abatement strategy. In most cases we see only the end result of the disturbance process without having a sufficient historical data base on either the predisturbance condition or how the biota responded to the type and intensity of disturbance. Without such a data base, the paleolimnological approach is the only way to delineate past lake conditions and the response to disturbance events. Although remains of several faunal groups are preserved in lacustrine sediments, bryozoans, chaoborids, and chironomids show the greatest promise for paleolimnological reconstructions. These groups can be used to make qualitative statements on water quality, but their use in quantitative reconstructions must await construction of calibration models relating subfossil assemblages to known water chemistry and trophic state, and questions on the relationship between producing population and observed subfossil assemblage, postmortem redeposition, differential preservation, and basic ecology are addressed. It is suggested that paleolimnological reconstructions couple detailed land-use histories with multiparameter analyses from dated cores.
Two-Hundred-Year pH History of Woods, Sagamore, and Panther Lakes in the Adirondack Mountains, New York State
Authors: Davis RB , Anderson DS , Charles DF , Galloway JN
Published: February 2009

Diatom remains in sediment cores from Woods Lake (L) (pH 4.9), Sagamore L (6.0), and Panther L (7.2) in the Adirondack Mountains, N.Y. were studied to infer lake water pH for the past 200 years. Historical studies and analyses of sedimentary 210Pb, Ca, Mg, K, pollen, and charcoal provided data for chronostratigraphy and for distinguishing the effects on inferred pH (IpH) of watershed disturbance versus acid deposition. Indications of watershed logging were found in post-1890 sediment at the three lakes, but the pH responded (increase 0.5–1.0 IpH unit) only in poorly buffered Woods L. Mean IpHs prior to anthropogenic disturbance and acid deposition were 5.1–5.2 (Woods), 6.7–7.0 (Sagamore), and 7.4–7.6 (Panther) compared to IpHs for surface-sediment of 4.8, 6.3, and 6.9, respectively, indicating an acidification but also that edaphically induced pH differences between the lakes have remained about the same. By 1940, the pH of Sagamore and Woods L had started to decrease. Despite watershed disturbances (which would tend to raise lake pH) at Woods L since 1950, the lake has continued to acidify. Acid deposition is the likely cause of acidification of the three lakes. At Panther L, however, the decrease in IpH since the 1960s is unlikely to reflect a decrease in the lake's summer pH due to the well-buffered water, but may indicate intensified depression of lake water pH restricted to periods of snowmelt.
Interstitial Water Sampling in Ecotoxicological Testing: Partitioning of a Cationic Surfactant
Authors: Pittinger CA , Hand VC , Masters JA , Davidson LF
Published: February 2009

Methods for collecting interstitial water (IW) in laboratory ecotoxicological testing were compared and used to characterize the partitioning behavior of a cationic surfactant in batch sediment/water systems. IW sampling methods included a conventional centrifugation technique, dialysis through a rayon membrane, and a novel fritted glass diffusion sampler. Dodecyl trimethyl ammonium chloride (TMAC) was the test compound monitored radiometrically in each static-renewal experiment. A 10-mg/L TMAC solution was delivered to test systems as overlying water, replenished daily; TMAC levels in sediment, interestitial water, and overlying water were monitored throughout the 20-day experiments. IW samples collected by the centrifugation procedure contained greater TMAC concentrations than samples collected by either dialysis or the fritted glass sampler. Equilibration of TMAC concentrations across the dialysis membrane was slow (>5 days), resulting in a substantial lag. Advantages of using the fritted glass sampler for ecotoxicological testing are discussed. Following rapid changes in TMAC levels in each compartment during the initial five days of each experiment, order of magnitude differences were observed in TMAC concentrations among sediments, overlying water, and interstitial waters, in decreasing order. The partition coefficient measured in separate shake-flask experiments performed at a high solids concentration was similar to the observed ratio between TMAC levels in sediments and interstitial water. Sorption of TMAC onto sediments was consistent with a first-order kinetics process.
Environmental Persistence/Degradation of Toxicity in Complex Effluents: Laboratory Simulations of Field Conditions
Authors: Degraeve GM , Clement WH , Arthur MF , Gillespie RB , O'Brien GK
Published: February 2009

A laboratory method to monitor the persistence or degradation of toxicity in complex effluent/receiving water mixtures was developed and preliminarily field-validated. The objective of this research was to develop a method for possible future use in the National Pollutant Discharge Elimination System (NPDES) effluent permitting process that recognizes differential rates of toxicity degradation in effluent/receiving water mixtures.

Initial studies were made with the toxicant 2,4-dichlorophenol (DCP) added to a natural receiving water in the laboratory. After incubation under conditions similar to the field, toxicity (as measured periodically by Microtox®) paralleled the degradation (or persistence) of the toxicant as measured chemically. Loss of DCP in the laboratory was similar to predicted field-loss rate. Receiving waters and industrial and municipal effluents were then incubated in the laboratory in proportions similar to those observed in the field. Environmentally relevant conditions of temperature, photoperiod, light intensity, humidity, and aeration were maintained. Periodically, samples were analyzed for toxicity using the Microtox® system to monitor persistence (or degradation). Following development of test protocol with the DCP and effluents, the laboratory unit was field-validated using chlorine in Mississippi River water in the field and in the laboratory. Other field validations using complex effluents are underway.

This simple laboratory method can be used to predict the persistence (degradation) of effluent toxicity in natural receiving waters. Ultimately, one may be able to model effluent toxicity behavior in natural systems by tracking toxicity degradation in the laboratory, which could result in a cost-effective, toxicity-based method for use in the NPDES permitting process.
Partitioning Between Dissolved Organic Macromolecules and Suspended Particulates: Effects on Bioavailability and Transport of Hydrophobic Organic Chemicals in Aquatic Systems
Authors: McCarthy JF , Black MC
Published: February 2009

Hydrophobic organic contaminants in aquatic systems bind to sediments or to suspended particles, and these associations affect the transport and bioavailability of contaminants and thus alter the exposure received by biota. We present evidence demonstrating the importance of another less obvious natural sorbent—dissolved organic macromolecules (DOM), such as dissolved humic materials—in altering the environmental fate of contaminants. Binding of a polycyclic aromatic hydrocarbon, benzo[a]pyrene, to DOM and to particles was measured for each sorbent and in a mixed system containing both sorbents. DOM competed with particles for binding of the dissolved contaminant and reduced the amount bound to particles. Binding to each sorbent was independent and noninteractive. Based on these results, equations were developed to indicate those environments and ecosystems for which failure to account for the role of DOM as a sorbent would result in 50 or 90% errors in steady state predictions about the exposure of aquatic organisms to contaminants.
An Integrated Fates and Effects Model for Estimation of Risk in Aquatic Systems
Authors: Bartell SM , Gardner RH , O'Neill RV
Published: February 2009

An integrated fate and effects model was developed to mathematically simulate the toxic effects of naphthalene on the growth of interacting populations in an aquatic system. Daily effects on biomass production were calculated for each model population as a function of its dynamic body burden of naphthalene. Separate simulations using constant environmental loading rates of 0.0001, 0.001, 0.01, and 0.10 g m−2 d−1 demonstrated changes in production that could not be extrapolated directly from naphthalene toxicity measured for related laboratory populations of aquatic organisms. Estimated risks of 50% reduction in fish production ranged from 0.08 to 0.65 for naphthalene loading rates of 0.000025 to 0.10 g m−2 d−1. Examination of naphthalene flux through the model system indicated that the combined effects of photolysis and volatilization were more important than biological processes in determining the fate of naphthalene for the 0.10 loading rate. This relative importance of physicochemical versus biological processes reversed for the 0.0001 loading rate. At intermediate loading rates, the relative importance of these processes varied seasonally. The integrated model demonstrated potential contributions of population-specific rates of naphthalene uptake and depuration and naphthalene toxicity to estimation of possible ecological risks posed by naphthalene in aquatic systems.
Evaluating Ecosystem Response to Toxicant Stress: A State Space Approach
Authors: Johnson AR
Published: February 2009

Ecosystems can be regarded as complex biogeochemical systems maintained in a state of thermodynamic nonequilibrium by the flow of materials and energy. The state of such a system at any given time is generally assumed to be characterized by a finite set of measurable quantities. If these variables are taken to be the components of a vector, the instantaneous state of an ecosystem can be represented by a single point in an abstract multidimensional space. As an ecosystem undergoes changes in state, changes in the position of the corresponding vector will result, tracing out a state trajectory over time.

Within a state space representation, the response of an ecosystem to a perturbing influence, such as a toxicant, can be viewed as a displacement of the state vector away from its unperturbed trajectory. Such an approach was used to analyze data from a study of the response of experimental ponds and microcosms to chronic additions of a coal-derived synthetic oil. Ecosystem-level response surfaces and dose-response curves were derived based upon the average separation (distance of displacement) of exposed ecosystems relative to controls. The results exhibited patterns analogous to those observed in classical toxicology based on organismal response and could be used to define acceptable exposure conditions. The state space approach described here provides a coherent and objective framework for summarizing a large multivariate data set, and it should be of general use in providing both qualitative and quantitative descriptions of the behavior of perturbed ecosystems.
Ventilatory and Movement Responses of Bluegills Exposed to 1,3,5-Trinitrobenzene
Authors: van der Schalie WH , Shedd TR , Zeeman MG
Published: February 2009

TNB (1,3,5-trinitrobenzene) is a by-product of the TNT (2,4,6-trinitrotoluene) manufacturing process and is also formed by the photolysis of TNT in natural waters. The effects of TNB on the ventilatory patterns and whole-body involvement rates of bluegills (Lepomis macrochirus) were determined. Fish were exposed for six days to concentrations of TNB ranging from 6% (0.03 mg/L) to 108% (0.61 mg/L) of the 96-h LC50. The lowest TNB concentrations causing significant changes in the parameters monitored were 0.13 mg/L (ventilatory depth) and 0.61 mg/L (cough rate and body movement). These responses occurred within the first 4 h of exposure. No effects on ventilatory rate were found. The large differences is sensitivity between the parameters monitored indicate that automated water or wastewater toxicity monitoring systems that utilize fish ventilatory or movement responses should use several end points to determine the presence or absence of toxicity. The most sensitive, short-term ventilatory changes measured in this test occurred at concentrations near the estimated chronic toxicity levels of TNB for fish. The range between the highest TNB concentration causing no responses and the lowest concentration causing short-term ventilatory responses was 0.06 to 0.13 mg/L. This is comparable to reported no effect/effect ranges for TNB in early life stage tests of 0.08 to 0.12 mg/L for fathead minnows and 0.08 to 0.17 mg/L for rainbow trout.
Uninduced Rat Liver Microsomes as a Metabolic Activation System for the Frog Embryo Teratogenesis Assay—Xenopus(FETAX)
Authors: Bantle JA , Dawson DA
Published: February 2009

Current validation studies of FETAX (Frog Embryo Teratogenesis Assay—Xenopus) suggest that fewer than 15% of test compounds will prove to be false negatives or positives in this in vitro teratogenesis screening assay. We have developed a metabolic activation system employing uninduced rat liver microsomes to convert proteratogens, thus reducing the number of potential false negatives. Microsomes were prepared by homogenizing livers and centrifuing the homogenate first at 600 and then at 9000 × g avg. The supernatant from these centrifugations was then centrifuged twice at 120 000 × g avg. By not inducing the rat liver with Aroclor 1254, toxicity from Aroclor metabolites was avoided. Xenopus blastulae were exposed to different concentrations of cyclophosphamide together with the microsomes, generating system, and antibiotics for a period of 96 h. Activation reduced the 96-h LC50 by 4-fold from >11.0 to 2.8 mg/mL. The EC50 malformation was reduced 3.4-fold from 6.8 to 2 mg/mL. The severity of malformation was also increased by activation. Activation of cyclophosphamide also caused a decrease in growth. Uninduced rat liver microsomes can be used as an acceptable in vitro metabolic activation system for FETAX.
Behavioral Responses to Low Levels of Toxic Substances in Rainbow Trout (Salmo Gairdneri, Rich)
Authors: Hadjinicolaou J , LaRoche G
Published: February 2009

An avoidance apparatus was designed with a 10-m-long channel to obtain time-lapsed, three-dimensional display of fish positioning. With this new apparatus, effects of the toxicant dodecyl sodium sulfate (DSS) and two different polymers and monomers were tested on rainbow trout. The results show that four types of avoidance-preference, dose-response curves may be observed and that at low concentrations (0.01 to 0.08 mg/L for the DSS and in a range of 0.4 to 4 mg/L for different monomers and polymers) some toxicants may attract rather than repel certain organisms. This response is interpreted as representing behavioral extension of hormesis, the name given to the stimulatory effects caused by low levels of potentially toxic agents. An interpretation of unexplained literature data presents findings that endorse the concept of behavioral hormesis.
What Constitutes Field Validation of Predictions Based on Laboratory Evidence?
Authors: Cairns J
Published: February 2009

The term validation has appeared in the literature with great regularity in the last few years, but the process has yet to be explicitly stated. Most of the predictions of environmental hazard are based primarily, and sometimes entirely, on laboratory toxicity tests involving single species. While this may change over the years, it will remain true for the immediate future. Therefore, the validation process must start with an explicit statement of the types of predictions being made on the basis of single species laboratory toxicity tests. Unfortunately, the terms no-adverse-biological-effects concentration or biologically safe concentration, or no-observable-effects level might lead the unwary to believe that all possible adverse effects were unlikely to occur at concentrations below the one stated. In fact, I have never seen a body of evidence in a scholarly professional journal that would convince reviewers that these assertions had been confirmed in a scientifically sound way. Some more modest but more explicit predictions and validation criteria, for illustrative purposes only, follow. 1. Only the test species is expected to be protected fully in natural systems, and validation means confirming this assumption in the field. 2. Other species than the one(s) actually tested are thought to be protected at the no-observable-effects concentration, and a list of these species inhabiting the natural systems in question is included. Validation is carried out with field observations on all of these species. 3. No adverse effects at the community level of biological organization will occur, and the characteristics used to validate this assumption are listed. Validation may be carried out in microcosms or mesocosms under certain circumstances but should be based on field observations whenever possible. 4. No adverse effects will occur at the ecosystem level of organization, and the characteristics at the ecosystem level used to validate this assumption are listed. Validation in field enclosures or natural systems should probably be mandatory.

By coupling the explicit predictions being made with the explicit end points being used to validate these predictions, a more systematic and orderly process of validation will ensue. Until more hypothesis testing is carried out in the field of hazard evaluation than is in place presently, it is unlikely that the field will get the recognition it deserves.
Interlaboratory Testing of a Standardized Aquatic Microcosm
Authors: Taub FB , Kindig AC , Conquest LL
Published: February 2009

The “Standardized Aquatic Microcosm” (SAM) Protocol is being tested in three laboratories as well as in the laboratory where it was developed (University of Washington). Each laboratory has used a control and three concentrations of copper sulfate and has completed at least one experiment.

The successional sequence in the controls has consistently included nitrate depletion and an early algal bloom terminated by increases in grazer populations, especially Daphnia. In all experiments analyzed to date, low copper sulfate concentrations were associated with temporary reduction in Daphnia and concurrent algal blooms; at higher concentrations, the algae were inhibited to a greater extent and for a longer duration.

The concept of a “days-weighted-by-variable” statistic (DWV) is introduced to assess variation between experiments. The DWV, as a measure of the center of gravity of a microcosm time trace, is useful to detect shifts in timing under increased copper concentrations.
Evaluation of the Indicator Species Procedure for Deriving Site-Specific Water Quality Criteria for Zinc
Authors: Parkerton TF , Stewart SM , Dickson KL , Rodgers JH , Saleh FY
Published: February 2009

The indicator species procedure enables modification of a national water quality criterion to account for differences in the biological availability/toxicity of a chemical introduced into site waters. To evaluate this procedure, a case study was conducted with zinc using the Trinity River near Denton, Texas as an example site.

Acute and chronic toxicity tests were performed with Pimephales promelas and Daphnia pulex in both natural river and reference waters. Toxicity results were expressed as a function of both total and soluble metal.

An acute water effects ratio (WER) was used to calculate the site-specific criterion maximum concentration. The site-specific value showed excellent agreement with the national water quality criterion adjusted for the site water hardness when based on total zinc. These findings were altered when toxicity results from a different reference water were used in calculations, but were unaffected if test organisms were not acclimated in site water prior to testing. Three different methods were used to calculate the site-specific criterion continuous concentration, which was found to be up to four times lower than the national criterion. Toxicological differences observed between lab and site waters were reduced when expressed in terms of mean soluble metal.

Additional experiments demonstrated that particulate zinc was not biologically available under test conditions and that soluble zinc may vary in its toxicity. Data also suggest that kinetic factors influence zinc toxicity. The implications of this research for the development of site-specific metal criteria are discussed.
Drilling Fluid Bioassays Using Pacific Ocean Mysid Shrimp, Acanthomysis sculpta, a Preliminary Introduction
Authors: Machuzak MJ , Mikel TK
Published: February 2009

The toxicity evaluation of drilling fluids using Gulf Coast mysid shrimps has become well developed during the past several years and is used by the Region II EPA to evaluate discharges from offshore platforms in the mid-Atlantic. Development of a method to utilize native mysid shrimps for Pacific Ocean platforms, however, is still in its infancy. A new preliminary acute toxicity method has been developed using Acanthomysis sculpta, a mysid shrimp commonly found associated with central California kelp forests. The new method is similar to mid-Atlantic procedures but has been modified to accommodate the life-style of the Pacific Coast species and to be in compliance with the specifications of EPA, Region IX. A slurry is prepared by combining one part of drilling fluid with nine parts of filtered natural seawater. This solution is mixed on a stir plate while being vigorously aerated for 30 min. The slurry is then allowed to settle for 1 h, and the supernatant is decanted and used directly in the toxicity test. Six 1-L concentrations of the extract solution (usually 100, 56, 32, 18, 10, and 0%) to seawater are prepared in triplicate and placed in a cooling bath maintained at 15.0 ± 1.0°C. Concentrations are aerated as needed to maintain 65% of oxygen saturation, and then 20 previously collected and similar-sized (6 to 8 mm) mysid shrimp are randomly placed in each container. The test continues for 96 h, after which the live organisms are counted and the LC50 interpolated from averaged percent mortality.
In Vitro Cytotoxicity of Polychlorinated Biphenyls (PCBs) and Toluenes to Cultured Bluegill Sunfish BF-2 Cells
Authors: Babich H , Borenfreund E
Published: February 2009

An in vitro cytotoxicity methodology, initially developed for use with mammalian cells to evaluate the relative acute toxicities of chemical agents, has been adapted for aquatic ecotoxicity studies by using cultured fish cells as the bioindicator system. This methodology, termed the neutral red assay, was applied to evaluating the comparative in vitro cytotoxicities of a series of polychlorinated biphenyl mixtures and substituted toluenes to bluegill sunfish BF-2 cells in culture. Although comparatively small differences were noted in the in vitro cytotoxicities of the polychlorinated biphenyl mixtures, their differential potency to the BF-2 cells was Aroclor 1248 ≃ 1016 ≃ 1254 ≃ 1242 > 1221 ≃ 1232 > 1260 > 1262. For the toluene series, the sequence of comparative potency was α,α,2,6-tetrachlorotoluene > 2,3-dinitrotoluene > 2,4-dichlorotoluene, 6-chloro-3-hydroxytoluene > 2,6-dinitrotoluene, 2,4-dinitrotoluene, o-, m-, and p-chlorotoluene >>> toluene. The in vitro cytotoxicities of the chlorinated toluenes, but not of the nitro-containing toluenes, were correlated with their log octanol/water partition coefficients. These data are in accord with published studies on the in vivo acute toxicities (LC50 assays) to fish of chloro- and nitro-containing toluenes. The greater in vitro cytotoxicity of 2,3-dinitrotoluene than of the two other dinitrotoluene analogs was also in agreement with published in vivo acute toxicity studies with freshwater fish. This present study, in conjunction with previous in vitro cytotoxicity assays with BF-2 cells, has demonstrated the potential usefulness of the neutral red assay for predicting the in vivo response of fish to acute exposures of chemicals and for establishing structure-activity relationships among groups of related chemicals.
A Method for Evaluating Effects of Toxic Chemicals on Fish Growth Rates
Authors: Crossland NO
Published: February 2009

Provided that environmental factors and the food supply are not limiting, the growth rate of fish is more or less constant from the fry stage until the onset of maturity. It is independent of the initial size of the fish and the duration of the period between measurements. This paper describes a method which uses the growth rate of juvenile rainbow trout as a sensitive response for evaluating chronic toxicity.

Groups of 16 fish per 40-L aquarium were anesthetized, weighed, measured, and individually marked using freeze brands. Fish were fed a ration of pelleted food equivalent to 4% of wet body weight per day, given in two feeds per day. They were exposed under flow-through conditions to 3,4-dichloroaniline (DCA) at concentrations of 0, 19, 39, 71, 120, and 210 μg/L for a period of 20 days. Effects on length, weight, and growth rates were determined after 14 and 28 days exposure to DCA.

After 14 days there were no significant effects (P > 0.05) on length or weight, but there was a highly significant depression of growth rate (P < 0.01) among fish exposed to the highest concentration of DCA (210 µg/L). After 28 days there were statistically significant effects on length and growth rate at all concentrations between 39 and 210 µg/L, and there was a clear relationship between concentration and response. Growth rate was affected to a greater extent than length, and overall it proved to be a much more sensitive response than either weight or length.
The Aquatic Toxicity and Fate of Brass Dust
Authors: Haley MV , Johnson DW , Muse WT , Landis WG
Published: February 2009

A series of environmental bioassays and fate studies have been performed on brass dust. The standardized aquatic microcosm (SAM) was used as the long term, ecosystem assay.

Short-term bioassays using Daphna magna and green algae were conducted. The 48-h EC50 of the brass dust to D. magna ranged from 0.016 to 0.026 mg/L. Microscopic investigations indicated that the daphnia filter and ingest the material. Green algae were not as affected by the brass dust as the daphnids. The 96-h IC50 for Ankistrodesmus falcatus is 0.316 mg/L and for Selenastrum capricornutum, 0.056 mg/L. At very low concentrations of the brass, algal growth was stimulated.

Fate studies indicate that brass disassociation in water varies with pH. At low pHs the material rapidly disassociates into Cu++ and Zn++ ions. At pHs above neutrality the disassociation is markedly slower.

The short-term bioassays and fate studies were used to set the concentrations of brass for the SAM (the SAM is standardized protocol containing algae, invertebrates, bacteria, and a protozoan inoculated in 3 L of medium). A study using CuSO4 served as a positive control for the brass microcosm. In both microcosms the concentration of available copper slowly decreased until an equilibrium was reached. In addition, both microcosms demonstrated a dose response relationship with an increase in algal biomass correlated with an increase in toxicant dose. The cause is likely to be the elimination of the primary grazers, daphnia, because of the test chemical's toxicity. Recovery as measured by positive population growth of the daphids also demonstrated a dose-response relationship.
How Clean Is Clean? A Use of Hazard Assessment in Groundwater for Evaluation of an Appropriate Formaldehyde Spill Remedial Action Endpoint
Authors: Staples CA
Published: February 2009

A spill of formaldehyde from a pipe was discovered in October 1983 at a manufacturing site. Groundwater investigation revealed that much of the formaldehyde was trapped within a clay till layer 8 ft below the surface at a concentration of up to 9% by weight. The formaldehyde was leaching out of the unsaturated zone and moving into the saturated zone. A remedial action plan was begun that involved the oxidation of formaldehyde with injection of hydrogen peroxide coupled with pumping withdrawal and reuse of surrounding contaminated groundwater.

In the development of any hazardous waste site/groundwater remedial program, one issue that must be addressed is “When is the remediation finished?” or “How clean is clean?” In the case of the above formaldehyde spill, the specific question was how much formaldehyde can remain in the clay till such that leaching of the formaldehyde to groundwater with subsequent degradation, dispersion, and transport to a down gradient surface water with dilution would result in toxicologically safe concentrations for both humans and aquatic life? A remedial action endpoint of 100 ppm formaldehyde was predicted to achieve these human and environmental health goals using classical hazard assessment methodologies. These hazard assessment procedures are discussed in terms of their relative contribution and usefulness in the overall remedial action process.

Two-dimensional solute transport groundwater modeling was used to predict concentrations that may discharge into a down gradient river. Hydrogeologic features, including water level gradients, dispersivities, hydraulic conductivities, porosity, and aquifer material density, were measured with a calculated leaching rate and formaldehyde biodegradation rates for estimating down gradient solute transport times and concentrations. Formaldehyde entering surface waters would be diluted by appropriate stream flows to yield instream formaldehyde exposure concentrations. Resultant formaldehyde brook concentrations were combined with the conservative no impact concentration of 40 ppb to yield a margin of safety (MS). The instream formaldehyde concentration yielding an MS < 1.0 was used to back calculate the formaldehyde level that could be left in groundwater for dispersion and biodegradation by natural processes (here, 100 ppm). These modeling calculations were used to guide the appropriate choice of the target remedial action endpoint by using conservative assumptions and parameter values. Model results were considered sufficiently valid by local regulatory personnel to be of use as guidance for setting the remedial action target endpoint while the model predictions are still being fully verified. Final verification by measuring formaldehyde instream concentrations is part of the longer term remediation plan (<3 years).