bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Material Stress Sensitivity on Backcalculated Moduli and Pavement Evaluation
Authors: Stubstad RN , Mahoney JP , Coetzee NF
Published: March 2009

The Falling Weight Deflectometer (FWD) has become a popular device for evaluating both airfield and highway pavements. Typically, deflection tests with the FWD or HWD (Heavy Weight Deflectometer) are performed at predetermined load levels up to approximately 120 kN (27,000 Ibf) for the FWD and 240 kN (54,000 Ibf) for the HWD. This paper addresses the choice of load level for pavements exhibiting stress-sensitive behavior and the effect both on backcalculated moduli and the resulting rehabilitation designs for a number of pavement evaluation projects performed over the last few years.

It is well known that many unbound materials used in pavements exhibit non-linear behavior in laboratory tests, as discussed in the paper. The effect of such non-linear response in pavement structures suggests that deflection testing should be performed using load levels at or near the expected design loads, or in a manner which allows reasonable determination of material parameters defining the non-linear behavior.

Several pavement studies have been selected that exhibit non-linear response using various HWD test load levels, from approximately 60 kN (13,000 Ibf) to the full 240 kN (54,000 Ibf), with all tests on a given project performed on the same series of test points, at the same time. Results of backcalculation and evaluation analyses for these pavements are presented in the paper.

Analysis of deflection basins measured at the different load levels show significantly different backcalculated moduli which appear to be consistent with the stress-stiffening or stress-softening behavior exhibited by similar materials in laboratory tests. As a result, evaluation of structural capacity for a given (expected) traffic loading is significantly affected by these moduli values, and required overlay thicknesses may vary by a factor of two or more for different deflection test load levels, at a given pavement section. The analyses presented in the paper clearly illustrate the necessity for adequately defining actual material response in evaluating the pavement system response. Asphalt surfaced pavements tend to be more prone to these non-linear response characteristics, due to the significant structural contribution of the unbound layers often found in these pavements.
Phase LAG Effects on Analysis of FWD Data
Authors: Sebaaly PE , Holikatti S
Published: March 2009

The research documented in this paper examines the effect the phase lag has on the analysis of FWD data. The research examined the use of a deflection basin generated from the peak sensors' deflections, a deflection basin generated from instantaneous deflections based on peak load, and a deflection basin generated from instantaneous deflections based on the peak deflection at sensor #1. The influence of the various analyses is evaluated by comparing the material properties produced by each individual analysis and their relative impact on the recommended overlay thickness.

The analysis of the data indicated that almost all of FWD field data have instantaneous deflection basins which greatly differ from the deflection basin generated by the peak response. The backcalculation data indicated that the type of analysis may have a significant effect on the magnitudes of the moduli of the layers. Finally, the overlay analysis showed that there are significant differences among the recommended overlay thicknesses based on the different analyses. The differences were as high as 1.5 inches in some cases.
The Effect of Annular Load Distributions on the Backcalculated Moduli of Asphalt Pavement Layers
Authors: Crovetti JA , Shahin MY
Published: March 2009

A linear-elastic computer program is used to model uniform and annular loading distributions beneath the area of loading. Load distributions were selected to approximate those obtained using conventional impulse loading equipment on a variety of in-service asphalt pavement surfaces. Maximum surface deflections are computed for a factorial of pavement structures using the ELSYM5 computer program. The maximum deflections calculated under uniform load distributions are used to develop regression equations for the prediction of the asphalt layer modulus for twenty four separate pavement families. These equations are used in conjunction with deflections calculated under annular load distributions to backcalculate asphalt moduli. The errors which are introduced in asphalt layer moduli prediction due to various annular loading conditions are presented.
Effects of Pavement-Falling Weight Deflectometer Interaction on Measured Pavement Response
Authors: Boddapati KM , Nazarian S
Published: March 2009

In any linear elastic program used in backcalculation, a uniform pressure distribution is assumed for the applied load. As such, the loading system of any FWD should be designed so that the load transferred to the pavement is uniform. However, the pressure distribution is also affected by the pavement profile being impacted on.

A finite element study has been carried out to determine the cases where the imparted load would or would not yield a uniform pressure distribution and to assess its significance on the measured and backcalculated parameters. The FWD-pavement interaction has little significance when rigid pavements are tested. For flexible pavements, the deflections from the first sensor may be affected by this interaction. The softer the pavement system, the more significant this interaction will be.
Strategies for the Application of the Falling Weight Deflectomer to Evaluate Load Transfer Efficiency at Joints in Jointed Concrete Pavements
Authors: Jackson DJ , Murphy MR , Wimsatt A
Published: March 2009

The Falling Weight Deflectometer data for load transfer efficiency at joints in Jointed Concrete Pavement (JCP) must be properly analyzed and interpreted in order to prevent misleading results. Some parameters affecting pavement deflection are the pavement layer moduli, Poisson's ratios, thicknesses, and layer interaction. All of these must be considered to accurately “backcalculate” moduli from deflections. Joints add even more variables which affect the deflection measurement such as loss of support due to pumping at or near the joint. It is this parameter which will be discussed in this paper. First, a methodology for determining load transfer efficiency at a joint with subbase support will be given. Second the effects of loss of subbase support will be discussed and a methodology, with qualifications, given to determine load transfer at a joint that has loss of subbase support.
A review of Recent Developments in the Use of ASTM Standard Practice G 90 for the Testing of Nonmetallic Materials
Authors: Robbins JS
Published: March 2009

Accelerated outdoor weathering has a history which extends back at least 50 years into the early part of this century. In recent years though, this technique has matured and improved. Through standards, improvements have been made in the measurement of ultraviolet irradiance, improved reflectors, better quality water used to spray test specimens, and new cycles for improved correlation to real-time exposures. New developments recently introduced promise to allow further improvements to this test method.
Profile of Volatile Organic Chemicals in Nassau County Groundwater
Authors: Moon S , Adamski JM , Lichtman A
Published: March 2009

Statistical evaluation was conducted on the ten most common organic compounds found in Nassau County groundwater during 1987. The three most common chemicals found in the groundwater were tetrachloroethylene, trichloroethylene, and 1,1,1-trichloroethane. Few samples were found to contain chloroform in Nassau County (3% of drinking water samples, and 6% of non-drinking water samples). Surprisingly, bromoform was found more frequently than chloroform (11% of the drinking-water samples). However, the concentrations of bromoform were very low, usually less than 5 ppb, well below the allowed limits of 50 ppb in New York state. In addition to the frequency of occurrence of organic pollutants found in the water samples, the profile of concentration range was also studied. A possible source for bromoform and its related compounds is discussed.
The Impact of Particle Size on TCLP Extraction of Cement-Stabilized Metallic Wastes
Authors: Prange NE , Garvey WF
Published: March 2009

EPA has introduced the Toxicity Characteristic Leaching Procedure (TCLP) in rulemakings associated with the Hazardous and Solid Waste Amendments of 1984. Limited ruggedness testing has evaluated the method's sensitivity to some test variables but has not addressed the effect of waste particle size. The TCLP method specifies a maximum particle size (9.5 mm sieve opening) and sets no lower limit.

To evaluate the effect of particle size, the authors tested an arsenic waste and a chromium waste, each stabilized with Portland cement. Five discrete particle size fractions ranging from 9.5 mm down to 0.5 mm were extracted by the TCLP procedure. For both wastes, it was found that the metals leached more readily from the larger particle fractions. Furthermore, the pH of the extraction fluid during the first 2 hours of the extraction stayed acidic for the large particles while for the smaller particles, the pH quickly became basic. Final extract pH was lower for the larger particles than for the smaller particles.

The results of this work indicate that particle size has a strong influence on TCLP extraction results for the tested wastes. This suggests that the particle size variable needs tighter controls than presently specified in the TCLP method to ensure reproducible results for at least some wastes.
Development and Evaluation of Analytical Techniques for Total Chlorine in Used Oils and Oil Fuels
Authors: Gaskill A , Estes ED , Hardison DL , Friedman PH
Published: March 2009

A current EPA regulation prohibits the sale for burning in nonindustrial boilers of used oils and oil fuels contaminated above specified levels with total chlorine. Analytical techniques for determining total chlorine were evaluated to provide regulatory agencies and the regulated community with appropriate chlorine test methods. The techniques evaluated included oxygen bomb combustion followed by chemical titrations or ion chromatography, instrumental microcoulometry, field test kits, an instrumental furnace/specific ion electrode determinator, a device based on the Beilstein reaction, and x-ray fluorescence spectrometry. These techniques were subjected to interlaboratory testing to estimate their precision, accuracy, and sensitivity. Virgin and used crankcase oils, hydraulic and metalworking oils, oil fuels and oil fuel blends with used oils were tested. The bomb techniques, one of the test kits, microcoulometry and all but one x-ray analyzer were found to be suitable for this application. The chlorine furnace and the Beilstein device were found to be inapplicable at the levels of interest. The second test kit is being modified at this time.
Preparation of Natural Matrix Type Samples for Performance Evaluation of Resource Conservation and Recovery Act (RCRA) Contract Laboratories
Authors: Clements HA , Loebker RE , Klosterman DL
Published: March 2009

The Quality Assurance (QA) Branch develops, analyzes, and distributes natural matrix samples to evaluate the performance of laboratories conducting analyses for the Office of Solid Waste (OSW). In these studies each laboratory is requested to analyze an organic sample and an inorganic sample using the analytical methods specified by OSW.

The sample designs and reference values are established by multiple analyses in the QA Branch laboratory and contract referee laboratories. These data are evaluated statistically and must be judged acceptable before samples are distributed to the 50–60 RCRA contract laboratories. These data are also furnished to OSW for use in evaluating the results reported by the contract laboratories.
Data Consolidation and Reporting for the Analytical Laboratory
Authors: Low N
Published: March 2009

Automation of laboratory instrumentation has significantly increased the rate at which samples could be analyzed. However, productivity in some other processes have not made the same gains due to the human decisions and operations involved. The personal computer, combined with the capabilities of the analytical data system, can be used in new ways to atuomate some of these processes. As a result, significant improvements can be made in throughput and quality of reports.
An Analytical Comparison of Short Crack and Deep Crack CTOD Fracture Specimens of an A36 Steel
Authors: Sorem WA , Dodds RH , Rolfe ST
Published: March 2009

The effect of crack-depth to specimen-width ratio on crack tip opening displacement (CTOD) fracture toughness is an important consideration in relating the results of laboratory tests to the behavior of actual structures. Deeply cracked three-point bend specimens with crack-depth to specimen-width ratios (a/W) of 0.50 are most often used in laboratory tests. However, to evaluate specific weld microstructures or the behavior of structures with shallow surface cracks, specimens with a/W ratios much less than 0.50 often are required. Laboratory tests reveal that three-point bend specimens with short cracks (a/W = 0.15) exhibit significantly larger critical CTOD values than specimens with deep cracks (a/W = 0.5) up to the point of ductile initiation.

In this study, finite element analyses are employed to compare the elastic-plastic behavior of square (cross-section) three-point bend specimens with crack-depth to specimen-width ratios (a/W) ranging between 0.50 and 0.05. The two-dimensional analysis of the specimen with an a/W ratio of 0.15 reveals a fundamental change in the deformation pattern from the deep crack deformation pattern. The plastic zone extends to the free surface behind the crack concurrent with the development of a plastic hinge. For shorter cracks (a/W= 0.10 and 0.05), the plastic zone extends to the free surface behind the crack prior to the development of a plastic hinge. For longer cracks (a/W > 0.20), a plastic hinge develops before the plastic zone extends to the free surface behind the crack.

These results prompted further study of specimens with an a/Wratio of 0.15 using three-dimensional, elastic-plastic finite element analyses. Results of the short crack (a/W = 0.15) analysis are compared to the results of the deep crack (a/W = 0.50) analysis reported previously by the authors. In the linear-elastic regime (characterized by small-scale plastic deformation) the relationship of stress ahead of the crack tip to CTOD is identical for the short crack and the deep crack specimens. At identical CTOD levels in the elastic-plastic regime (large-scale plasticity, hinge formation), the crack tip stress is significantly lower for specimens with a/W = 0.15 than for specimens with a/W = 0.50. Correspondingly, at equivalent stress levels, the CTOD for the short crack is approximately 2.5 times the CTOD for the deep crack. This observation has considerable significance in the application of CTOD results to failure analysis or specification development where the fracture mechanism is cleavage preceded by significant crack tip plasticity.
Application of J-Integral and Modified J-Integral to Cases of Large Crack Extension
Authors: Joyce JA , Davis DA , Hackett EM , Hays RA
Published: March 2009

The J-integral is widely accepted as a measure of elastic-plastic fracture toughness of engineering alloys. Specimen size and geometry dependence were first noted in fracture toughness measurements using the ASTM E 813 calculation of the deformation J-integral (Jd) by McCabe and Landes [1] in 1983. The modified J-integral (Jm) was introduced by Ernst [2] to attempt to minimize or eliminate size and geometry dependence. Since Jm was introduced, questions have arisen regarding the proper parameter to describe the response of a flawed body to loading. The objective of this research task is to investigate the crack growth and specimen J capacity limitations of Jd and to verify the accuracy and specimen independence of the current Jm formulation. This research is expected to affect decisions concerning the use of small laboratory specimens to predict elastic-plastic crack growth resistance in engineering structures.

The J-R curve tests have been conducted on ½T, 1T, and 2T compact specimens of materials having critical fracture toughness values ranging from JIc = 140 to 455 kJ/m2. These materials include HSLA-80 steel, A106 steel, 3-Ni steel, and two A533B steels. These tests were conducted in accordance with ASTM E 1152 except that specimen loading was continued until large crack extensions were present, in many cases exceeding 50% of the initial uncracked ligament (b). All specimen data were then analyzed using the equations of ASTM E 1152 for the standard deformation J-integral (Jd) resistance curve. Additional analysis was conducted as well in terms of the modified J-integral (Jm) using equations proposed by Ernst and Landes [3]. This latter quantity was possibly useful to larger crack extensions. The test procedure was directed towards finding the useful limits of the two J quantities for the materials listed above or for materials of equivalent strength and toughness.
Adhesive Fracture Testing
Authors: Mecklenburg MF , Arah CO , McNamara D , Hand H , Joyce JA
Published: March 2009

The need for lightweight materials for a variety of applications has resulted in the use of structural adhesives to bond prototype structures. Adhesives developed to accommodate the stringent requirements of these high-technology applications are usually deficient in one or two of three very crucial properties: strength, moisture resistance, and toughness. So far, advances in adhesive formulation that have ameliorated one of these deficiencies have generally adversely affected the others. Hence a considerable amount of effort is being expended in the search for strong, moisture resistant, and tough adhesives.

As adhesives become tougher and less brittle, evaluating their performance in terms of fracture parameters becomes more complicated. Linear elastic fracture mechanics (LEFM), which is widely used to characterize these materials, does not fully describe adhesive performance as more and more ductility or plastic deformation is introduced. In the study reported here, we introduce the energy separation method for characterizing the fracture resistance of adhesives and compare it with currently used elastic and plastic fracture parameters such as G and the J integral. Both neat and bonded ½ CT plan specimens were tested and compared in this work.
Effect of Dynamic Strain Aging on Fracture Resistance of Carbon Steels Operating at Light-Water Reactor Temperatures
Authors: Marschall CW , Landow MP , Wilkowski GM
Published: March 2009

This paper reviews the phenomenon of dynamic strain aging in carbon steels and considers its effects on the fracture behavior of carbon-steel pipes and pressure vessels in lightwater reactors operating at elevated temperatures near 290°C (550°F).

Dynamic strain aging is a phenomenon in which aging occurs simultaneously with plastic straining. It occurs over a range of temperatures that depends on strain rate. In tensile tests, it is manifested by increased tensile strength, increased strain-hardening rate, serrated stress-strain curves, and decreased ductility.

Evidence is presented to show that the occurrence of dynamic strain aging can significantly lower the fracture resistance of carbon steels. This lowering of fracture resistance may be manifested in several ways: (1) JIc is lower at light-water reactor (LWR) temperatures than at room temperature, (2) the tearing modulus is lower at LWR temperatures than at room temperature, and (3) stable ductile crack growth may be interrupted by unstable ductile fracture at LWR temperatures but not at room temperature.

The paper examines probable causes of dynamic strain aging and describes methods for identifying which steels are susceptible to it.
Microstructure and Fracture Toughness of Cast and Forged Ultra-High-Strength, Low-Alloy (UHSLA) Steels
Authors: Zeman J , Rolc S , Buchar J , Pokluda J
Published: March 2009

This paper describes the fracture toughness and microstructure relations for ultra-high-strength, low-alloy (UHSLA) steels corresponding to AISI 4340 composition. The steels were either cast or forged, heat treated at austenitizing temperatures from 840 to 1100°C, oil quenched and tempered at 180 and 650°C. Fracture toughness, tensile, and Charpy impact toughness tests, and testing of apparent fracture toughness under the influence of notch root radius, were performed simultaneously. Investigation of microstructures and corresponding mechanical properties, as well as fractographic examinations and evaluation of chemical heterogeneity, made it possible to elucidate the alteration of fracture behavior.

It was found that cast low-tempered steel has higher fracture toughness (KIc) than forged steels, though its conventional mechanical properties are lower. Increasing KIc caused by the higher austenitizing temperature of forged steel was also observed. The coarsened prior austenite grains and decreased grain boundary cohesive strength are mainly responsible for the intergranular crack initiation and the related modification of the crack path, the consequence of which may be a change in the effective stress intensity factor.

The proposed model, based on assumed average probable crack path angle deflection controlled by the grain boundary, has yielded satisfactory agreement with experimental results. The mechanical properties of the more heterogeneous cast steel can be elucidated in the same sense. It has been concluded that there exists some uncertainty in the determination of “valid” plane strain fracture toughness, particularly in the case of ultra-high-strength steels, along with their more pronounced macro/microstructure heterogeneity. Due to this effect, the recommended procedure of KIc measurement can provide undesirable overestimation of the material quality being tested.
Treatment of Singularities in a Middle-Crack Tension Specimen
Authors: Shivakumar KN , Raju IS
Published: March 2009

A three-dimensional finite-element analysis of a middle-crack tension (M-T) specimen subjected to Mode I loading was performed to study the stress singularity along the crack front. The specimen was modeled using 20-node isoparametric elements with collapsed non-singular elements at the crack front. The displacements and stresses from the analysis were used to estimate the power of singularities, by a log-log regression analysis, along the crack front. Analyses showed that finite-sized cracked bodies have two singular stress fields of the form σ = C0(θ,z)r-½ + D0(θ,ϕ)Rλσ. The first term is the cylindrical singularity with the power -½ and is dominant over the middle 96% of the crack front and becomes nearly zero at the free surface. The second term is a vertex singularity that exists at the intersection of the crack front and the free surface. Because of two singular stress fields near the free surface and the classical square root singularity elsewhere, the strain energy release rate (G) appears to be an appropriate parameter all along the crack front.
A Review of Polymer Test Methods Applicable to Geosynthetics for Waste Containment
Authors: Mores M , Cassidy PE , Kerwick DJ , Koeck DC
Published: March 2009

The study of the environmental degradation of geosynthetic materials used in hazardous waste facilities has generated much interest in recent years. Analytical methods are used to supplement conventional structure changes and mechanisms of failure associated with the polymer. Any changes in the base polymer caused by chemical exposure may result in severe changes in strength, durability and serviceability of the geosynthetic. Chemical and physical analytical methods are used in evaluation of chemical compatibility and long-term durability of geosynthetics for several purposes: 1) to verify that geosynthetics tested in advance of landfill construction are essentially the same as those procured for the actual installation, 2) to identify and monitor changes in molecular structure caused by chemical attack, and 3) to provide accelerated assessment of the effects of long-term aging, an especially difficult and as yet, not thoroughly researched topic. These factors can be reviewed by studying the oxidation and solvation properties as well as the change in crystalline structure of the plastics.

This paper discusses “fingerprinting” methods used to characterize geosynthetics. These methods fall into four major categories of analytical techniques: thermal analysis, spectroscopy, chromatography and microscopy. The advantages of these analytical techniques are their precision, accuracy, and small sample size requirements. The methods discussed in this paper can detect small changes in molecular structure that often are not observed with traditional bulk properties testing after short aging times.
Pyramid Puncture Test for Evaluating the Protection Function of Geotextiles
Authors: Pühringer G
Published: March 2009

At present, there are inadequate recommendations to guide the design engineer in the selection of protection geotextiles in association with geomembranes. Current recommendations generally rely on elaborate field experiments or costly laboratory studies. A relieable engineering assessment method that will yield useful puncture values is not currently available. With the pyramid puncture test, however, testing is possible on geomembranes and protective nonwoven geotextiles to determine the magnitude of the protection provided by geotextiles.

The test apparatus consists mainly of a pyramid piston, an underlaying media and a test press. The test specimens can be tested unclamped or clamped between rings. An electric circuit is applied between the piston and the underlying media to indicate the puncture force at the point of perforation.
Multispecies Methods of Testing for Toxicity: Use of the Rhizobium-Legume Symbiosis in Nitrogen Fixation and Correlations Between Responses by Algae and Terrestrial Plants
Authors: Garten CT
Published: March 2009

Responses of the Rhizobium-legume symbiotic relationship to long-term (5- to 7-week) and short-term (2-week) exposures of copper sulfate, 2,4-dichlorophenoxyacetic acid, and streptomycin sulfate were examined in bush beans and clover. Toxic effects were evaluated by comparing plant biomass (yield), nodulation success, nitrogen fixation rate as indicated by acetylene reduction, and plant nitrogen content in controls and in plants exposed to various concentrations of the chemicals. Plants with long-term continuous root exposure were affected more than plants with short-term exposure, as indicated by reductions in nitrogen fixation rates and plant growth. Although rates of acetylene reduction (nitrogen fixation) were depressed, plant biomass and the numbers of root nodules produced were simpler, less expensive indices of exposure.

In a second test, the responses of algae (Selenastrum capricornutum and Chlorella vulgaris) and terrestrial plants (radishes, barley, bush beans, and soybeans) to 21 different herbicides were compared to evaluate the use of a short-term (96-h) algal growth inhibition test for identifying chemicals potentially toxic to terrestrial plants. Two test end points were evaluated: (1) the highest concentration resulting in no statistically significant reduction in the growth rate of algae or terrestrial plants, and (2) the concentration at which algal growth or terrestrial plant biomass was reduced by 50%. Test results were correlated for the two algae and for all pairs of vascular plants. However, results of the algal tests did not correlate with those of the terrestrial plants. Furthermore, according to tests with Selenastrum capricornutum, there was only a 50% chance of successfully identifying herbicide levels that reduced terrestrial plant biomass. For the herbicides and species examined, short-term toxicity tests with algae were not good indicators of toxicity to terrestrial plants.
Bioaccumulation of Mercury Compounds in Two Aquatic Plants (Elodea densa and Ludwigia natans): Actions and Interactions of Four Abiotic Factors
Authors: Ribeyre F , Boudou A
Published: March 2009

The research presented is based on an experimental study of bioaccumulation of two mercury compounds (HgCl2 and CH3HgCl) by two species of rooted macrophytes (Elodea densa and Ludwigia natans). Contamination of the experimental model (water, natural sediment, and macrophytes) is carried out by introducing contaminants into the water column. The actions and interactions of four abiotic factors (temperature, pH, photoperiod, and light intensity) are studied by setting up a complete experimental design corresponding to 72 different experimental conditions. Results relate to the evolution of mercury concentrations in the water over 28 days' exposure, plant growth (weight and stem length), and quantification of total mercury bioaccumulation (concentration and content) in the whole plants.
Ecological Effects Evaluation of Two Phosphorus Smoke-Producing Compounds Using Terrestrial Microcosms
Authors: Tolle DA , Arthur MF , Duke KM , Chesson J
Published: March 2009

An intact soil-core microcosm and static exposure system were used to evaluate the potential ecological effects of two obscurant smokes, red phosphorus/butyl rubber (RP/BR) and white phosphorus/felt (WP/F), used in the field during U.S. Army training exercises. The terrestrial microcosm technique differed from the test protocol prepared for the U.S. Environmental Protection Agency by using a preliminary plant stress-ethylene test to help select the dose range for microcosm testing, and by combining aspects of traditional range-finding and definitive tests into a single microcosm test.

Three plant species (white sweetclover, perennial ryegrass, and wheat) were used for both preliminary and microcosm tests. The stress-ethylene tests indicated that extremely high doses of either smoke would be required to elicit a response in the microcosm test. This information guided selection of microcosm test concentrations. Microcosms were exposed to either RP/BR or WP smoke at target concentrations of 0, 100, 300, 600, and 1500 mg/m3. These concentrations bracket typical field concentrations.

Minor ecosystem-level effects were detected in microcosms only at the highest smoke concentration and included increased nutrient (Ca) loss in leachate, increased (wheat) or decreased (sweetclover) biomass yield, and increased element (Al, As, Pb, and P) uptake in plant tissue. No negative ecological effects of either smoke were detected at smoke concentrations equal to or below 600 mg/m3, even for 16 semiweekly exposures over an 8-week period.

It was concluded that: (1) deployment of these two smokes at typical field concentrations is unlikely to cause significant problems to most terrestrial systems; (2) the terrestrial microcosm system appears to be appropriate for evaluating the static, long-term, particle-deposition effects of other aerosols; and (3) the test design produces input for hazard assessment at considerable savings in cost and time compared to the more traditional range-finding plus definitive test strategy.
Seed Germination and Root Elongation Toxicity Tests in Hazardous Waste Site Evaluation: Methods Development and Applications
Authors: Linder G , Greene JC , Ratsch H , Nwosu J , Smith S , Wilborn D
Published: March 2009

Techniques modified from methods originally developed in the plant and weed science disciplines have yielded short-term tests that assess toxic chemical effects on plants. The seed germination and root elongation bioassays are laboratory toxicity tests that evolved to assess the direct and indirect soil toxicity of hazardous waste sites. These assessment tools are part of a collection of single-species toxicity tests that evaluate toxicity endpoints (seed germination and root elongation) pertinent to ecological assessments for terrestrial hazardous waste sites. Seed germination tests measure toxicity associated with soils directly, while root elongation tests consider the indirect effects of water-soluble constituents that may be present in site samples. In the seed germination toxicity test, site soil is mixed with a reference soil to yield a logarithmic series of exposure concentrations into which test seeds are planted. Germination is evaluated after a five-day exposure, and effective concentrations associated with a 50% reduction in seed germination are calculated. Contrasted to this direct test of soil toxicity, the root elongation test evaluates soil eluates that are prepared from site samples and contain watersoluble soil constituents potentially available to plants on-site and off-site. For the root elongation test, seeds are placed onto moistened filter paper that lines petri dish exposure chambers. Then, the exposure chambers are covered and incubated in complete darkness for five days; inhibition of root elongation is calculated as an EC50 (exposure concentration that yields a 50% reduction in root length relative to controls) upon termination of the test. By using a variety of plant species and developing a comparative toxicity database, both seed germination and root elongation toxicity tests may be applied on a site-specific basis and contribute to the toxicity assessment required as part of an ecological assessment for a hazardous waste site.
Effects of Chromium in Freshwater Algae and Macrophytes
Authors: Bassi M , Corradi MG , Favali MA
Published: March 2009

We have tried to assess the effects of chromium(VI) in four freshwater green algae (Coccomyxa minor, Scenedesmus armatus, S. dimorphus, and Haematococcus lacustris) and two freshwater macrophytes (Lemna minor and Pistia stratiotes). The algae were kept in liquid or solid culture medium containing 1, 2, 5 and 10 mg/L of chromium (VI) supplied as K2Cr2O7. Lemna and Pistia were grown in nutrient solution to which chromium was added as K2Cr2O7 to give final concentrations of Cr(VI) from 0.1 to 20 mg/L.

Coccomyxa and S. dimorphus seem to be less tolerant than the other algae because 1 mg/L Cr(VI) is sufficient to induce alterations of chloroplasts and cell wall. S. armatus and the quiescent spores of Haematococcus show alterations if Cr(VI) concentration is at least 5 mg/L. With 10 mg/L spore germination is completely inhibited. All the algae show loss of chlorophyll and other pigments and cell vacuolation. The chloroplasts appear damaged, and electronopaque deposits are visible in the cytoplasm and vacuoles.

In Lemna and Pistia the main macroscopical effects are retardation of growth, chlorosis, and wilting. Ultrastructural alterations consist in convolution and retraction of the plasma membrane, thylakoid disarrangement and swelling, transient increase of the number of mitochondria. Chlorophyll content diminishes, while protein content at first increases, then returns to average control values. These alterations are caused by even low doses of the metal (0.1 mg/L in Lemna and 1 mg/L in Pistia).
Evaluation of Protocols for the Assessment of Phytotoxicity
Authors: Sirois DL
Published: March 2009

Industrial chemicals and waste substances were tested in laboratory and growth chamber tests for toxicity to terrestrial and aquatic plants. Protocols for these tests were outlined in the 18 December 1978 and 16 March 1979 issues of the Federal Register. Tests on terrestrial plants included effects on seed germination and seedling growth as criteria of injury. Potential toxicity or stimulation of algae was assessed using Anabaena flos-aquae, Chlorella vulgaris, Skeletonema costatum, and Selenastrum capricornutum. Duckweed, Lemna minor, was used to assess potential phytotoxicity to higher aquatic plants. Evaluation of the results of tests showed that problems were encountered in implementing the test protocols. Unexplained variation in the data obstructed the calculation of confidence limits of the EC50 for the test substance with some species in the seedling growth test. The criteria for calculating the EC50 in Lemna and some algal tests were not met. Alternative use of analysis of variance (ANOVA) was hampered by heterogeneity of the variance in the test on Anabaena. In the algal tests chlorophyll appeared to respond differently than dry weight to the test substance. Although the protocols for these tests appear adequate, improvement is possible.
Tradescantia Sister-Chromatid-Exchange (SCE) Bioassay for Environmental Mutagens
Authors: Peng Y , Ma T-H
Published: March 2009

Tradescantia paludosa (spiderwort) has been one of the classical materials for cytogenetic studies since the late 1930s, and it possesses a number of endpoints to measure genotoxicity. Cytogenetic and genetic endpoints include chromosome/chromatid aberrations in its mitotic cells of microspores, root meristems, pollen tubes; meiotic pollen mother cells and gene mutation in the cells of staminal hairs. Although sister chromatid exchange (SCE) was first discovered in the plant root meristem of Allium cepa, the SCE technique has not yet been developed for Tradescantia root tip cells. Based upon the principles and technical procedures to measure SCEs in other plant systems, a standard SCE protocol was developed for Tradescantia in this study. Unlike the other plant system, Tradescantia roots developed from stem cuttings were used for SCE analysis. The major steps of this protocol include: root initiation, 5-bromodeoxyuridine (5-BrdU) treatment, thymidine chasing, colchicine treatment, fixation, pectinase digestion, squashing the meristematic cells under the coverglass, removal of coverglass, treatment with Hoechst and sodium salt solutions, UV-light treatment, staining with Giemsa. Well prepared slides were photographed under 400X magnification and analyzed for SCE frequencies. In addition, the spontaneous SCE frequency of Tradescantia was compared with those of Vicia and Allium.
Some Approaches to Rapid and Pre-Symptom Diagnosis of Chemical Stress in Plants
Authors: Velagaleti RR , Kramer D , Marsh SS , Reichenbach NG , Fleischman DE
Published: March 2009

The usefulness of ion accumulation patterns, leaf chlorophyll content, and delayed fluorescence of plant leaves as indicators of toxicity due to chemical stress is illustrated in this paper. Using plants as bioassay tools, these parameters can often be used to detect plant stresses rapidly and in advance of visible symptoms (pre-symptom diagnosis). They can also be used to distinguish and define the type and nature of chemical toxins present in a given substrate. Central to the use of plants as bioassay tools for toxicity assessment is the selection of appropriate species. The data presented here for the ion accumulation patterns and the chlorophyll content illustrate the genotypic variation in soybean indicated by the tolerance of the variety Manchu and the sensitivity of the Williams variety to sodium chloride (NaCl) and potassium chloride (KCl) stresses. Electrical conductivity measurements of leaf extracts have shown highly significant differences between Manchu and Williams; conductivity of leaf extracts in Manchu was significantly lower than Williams within the range of 10 to 40 mM of NaCl. Varietal and salt concentration differences were also highly significant for the concentration of chloride in the leaves beginning with stress levels of 20 mM NaCl or KCl. In Williams, chlorophyll concentration in leaves of two-week old plants declined significantly with increase in NaCl or KCl stress, the decline being concentration dependent. Highly significant differences in leaf chlorophyll were noticed between Williams and Manchu at various salt concentrations. The data presented for the delayed fluorescence technique show distinct patterns of leaf images under different stresses. The differences between stressed and nonstressed plants was evident for all the four parameters (conductivity, chlorophyll, chloride, delayed fluorescence), at certain stress levels, at a time when visible symptoms of chloride or sodium toxicity were not apparent, indicating the potential for pre-symptom diagnosis of chemical stresses in plants using these measures.
Monitoring Electron Beam Welding Process Using Electro-Magnetic Acoustic Transducers (EMAT's)
Authors: Crostack HA , Storp HJ , Bohm P
Published: March 2009

This paper describes the use of acoustic emission analysis (AEA) to monitor and control an electron beam welding process. For this to be successful requires that the signals emitted during the welding process be detected and that a good correlation can be established between the welding parameters and the acoustic signals. Weld monitoring applications place special requirements on both the electronic system as well as the sensor used to detect the AE signals. These requirements include a good directional selectivity and a capability for operation at high-temperatures which limits the use of piezoelectric sensors. In this paper the application of non-contact, electromagnetic acoustic transducers is described. The operation of such a sensor to detect the acoustic emissions accompanying an electron beam welding process is demonstrated and their application in a weld-monitoring system is described.
Structural Integrity Evaluation Using AE Techniques
Authors: Wood BRA , Harris RW
Published: March 2009

Acoustic Emission structural integrity evaluation tests rely on the validity of the detected acoustic emission data and the ability of the practitioner to both analyze and interpret the data to make a correct decision on the future use of the structure tested. Unfortunately with acoustic emission surveillance testing, it is not possible to know that all the available data has been assessed properly. The equipment sensitivity, threshold settings, and event capture capacity, when combined with the operator's decision making ability in real time, make it very difficult to achieve reliable integrity evaluation. The main problem is to interpret the data and so any monitoring programs should involve Expert Systems in conjunction with both acoustic emission and other operational monitoring data to maximise the utilization of the large amounts of information now available from operating plants and structures.
Characterisation of Dust Impact Process at Low Velocity by Acoustic Emission
Authors: Buttle DJ , Scruby CB
Published: March 2009

An acoustic emission (AE) technique is developed for monitoring hard particle impact for eventual use as an on-line erosion rate sensor. In a preliminary study the elastic impact of bronze and glass particles (size range 50 – 100 μm, velocities 2.5 – 7.1 m/s) on a aluminium target was investigated. The plate Green's function and system response were deconvolved from AE signals due to impact at epicentre. The velocity and time dependence and the absolute values of the peak impact force and impact time thus obtained compared well with predicted theoretical values. The quantitative technique developed was also used to size the particles, giving the correct mean particle size to within 4%. This fundamental approach provides a framework for later extension to plastic particle impact.
Delineation of Lithology and Groundwater Quality in a Complex Fluvial Estuarine Depositional Zone
Authors: Kuhlmeier PD , Sturdivant TE
Published: March 2009

In the development of a shallow subsurface investigation design strategy, a fundamental objective is the quantification of pollutants both vertically and horizontally within the subsurface. The dilemma produced in the design phase is one of a tradeoff between study costs and sufficient data collection to meet the study objectives. A novel application of two devices normally used in geotechnical engineering was tested at Naval Air Station Moffett Field for their ability to provide low cost, and timely hydrogeologic and chemical data.

The first device, a cone penetrometer, is capable of determining variations in soil media physical properties, both in saturated and unsaturated media, by measuring friction and pore water pressure. It provides a continuous log of unconsolidated materials through depth thus allowing for delineation of aquifer and aquitard zones. The second device, a hydropunch, is similar in nature to a well point and is capable of collecting in-situ pore water samples from depths up to 250 feet. A volume of 500 ml may be retrieved through a porous stainless steel tip and removed by closing upper and lower check valves.

Over 130 such CPT/Hydropunch measurements were used to characterize the mixed rivertine and estuarine sediments at the Mountain View, California Naval Air Station. The base which is on the National Priorities List contains numerous sites where pollutants have been identified. The study described in this paper focuses on the methods and results obtained from comprehensive use of the CPT/Hydropunch™ screening methodology in variably saturated media, to a depth of 60 feet.
Methodology for the In-Field Design of Monitoring Wells in Heterogeneous Fine-Grained Formations
Authors: Reynolds SD , Zemo DA
Published: March 2009

As part of the remedial investigation for a southern California Superfund site, clusters of depth-staggered monitoring wells were installed in heterogeneous unconsolidated alluvium. It was imperative that filter packs and well screens be properly designed such that ground-water samples and hydraulic head data would be suitable for use in litigation. The highly variable geometry and texture of the sediments precluded the use of a generic well design and suggested the need for a method of in-field design of monitoring wells.

In order to provide timely well design parameters, representative core samples of intervals to be screened were analyzed on-site. Simultaneous with the geophysical logging of the core boring, samples were sieved and the grain-size distribution data were used to design the filter packs and well screens. This approach provided a means by which each individual well could be tailored to the specific zone of interest, without delaying the pace of drilling and well construction or incurring costs above those normally associated with the more conventional approach employing a generic well design.
A Review of Fiber Optic and Related Technologies for Environmental Sensing Applications
Authors: Griffin JW , Olsen KB
Published: March 2009

Realization of most fiber optic chemical sensor (FOCS) concepts is the result of numerous recent developments in fiber optic, optoelectronic, and computer technologies. For the most part, these developments have been motivated and funded by the communications industry. This paper provides a review of current technologies and an overview of FOCS concepts currently under development for environmental sensing and monitoring applications.
Model of Aerosol Protection Offered by Permeable Protective Garments
Authors: Fedele PD
Published: March 2009

Hazardous airborne particulates exist in many industrial and military situations where personnel wear permeable clothing. The amount of protection that an individual receives from their clothing has been modeled using fluid dynamic and aerosol transport processes. This model evaluates the protective capacity of clothing systems from clothing material characteristics measurable in bench-top, laboratory-scale experiments. With appropriate representations of clothing geometry, hydrodynamic pressure distributions, aerosol penetration efficiencies and aerosol deposition velocities, aerosol deposition within the garment system and on the body beneath the garment system are calculated. By comparing the anticipated deposition levels with toxic effects doses, the effectiveness of permeable protective systems can be estimated. This model illustrates the processes of protective system performance and can provide a system assessment based on bench-scale experimental measurements.