bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strategy for Developing Remediation Target Concentrations Based on Human Exposure Duration Considerations
Authors: Nielsen JM , Washburn ST , Keoughan KM 
Published: March 2009

A risk-based strategy for calculating remediation target concentrations (RTCs) has been developed based on (1) the toxicity of the substances of primary concern, (2) the exposure period considered when evaluating different types of potential health effects, and (3) the timeframe of potential exposures. In developing RTCs, it is important to consider the likely period of human exposure and the potential for natural attenuation to reduce residual contaminant concentrations over time. Thus, RTCs to be achieved at the completion of active site remediation may be higher than the cleanup goals that must be met, on average, during the period of potential post-remedy exposure.
This methodology for developing RTCs has received acceptance by USEPA for soil cleanup at a Superfund site. For this site, USEPA required that soils be remediated to a level that will protect ground water (i.e., residual soil concentrations that will not result in leachate concentrations that exceed specified ground water cleanup goals) and that ground water contamination be addressed using a pump and treat remedy. An important component of the remedy ultimately adopted at the site is continued monitoring of the ground water to ensure that chemical concentrations in ground water are reduced below the cleanup goals. Soil sampling at the completion of the ground water remedy may also be required to demonstrate that chemical concentrations in soil at the end of the ground water cleanup are also at acceptable levels. Using a leaching model, the soil RTCs were defined as the concentrations remaining in soil after active soil remediation that would not result in leachate concentrations that exceed the ground water cleanup goals, on average, after completion of the ground water remedy.
Current Status of Environment Canada's Guidance on Control of Test Precision Using a Spiked Sediment Toxicity Test: What to Spike and How?
Authors: Stephenson GL , Day KE , Scroggins R , Kirby RS , Hamr P 
Published: March 2009

A draft of Environment Canada's “Guidance on Control of Test Precision Using a Spiked Control Sediment Toxicity Test” was reviewed by an international technical subcommittee. Comments were received, assessed, and discussed by members of the project steering committee, at which time, it was decided that in order to accommodate the recommendations of the subcommittee members, the revision of the document would be delayed until the results of some major sediment spiking and sediment formulation research initiatives were available.
A minimum of ten critical issues were identified by the reviewers and these issues have been summarized and briefly discussed in light of the consensus reached by the subcommittee. The data published in recent months in the scientific literature have helped to resolve some of the issues, or at least provide supporting evidence for some of the decisions that have been reached. However, one of the most contentious and critical issues that has not been resolved is the type and nature of the test medium to be spiked. In order to expand the scope beyond assessment of test precision to include interlaboratory comparisons and performance evaluation, it was decided that a formulated or artificial sediment option would be recommended as an alternative to field-collected sediments. This approach appears germane to several regulatory programs and there are currently a number of on-going research initiatives that are in the process of developing and testing the use of formulated sediments. Results of some recent experiments designed to study the effects of different formulations of sediment on survival and growth of the amphipod, Hyalella azteca, the chironomid, Chironomus riparius, and the mayfly, Hexagenia spp., as well as reproduction in the oligochaete worm, Tubifex tubifex, are presented and the implications for guidance development discussed.
Determination of the Pore Size Distribution of Nonwoven Geotextiles by a Modified Capillary Flow Porometry Technique
Authors: Vermeersch OG , Mlynarek J 
Published: March 2009

The capillary flow porometry(CFP)technique, known as the bubble point method, has been applied to measure the entire pore size distribution (PSD)of nonwoven geotextiles.
The classical technique is based on the differential analysis of two test runs: a wet run, during which the specimen is saturated by a wetting fluid, and a dry run, carried out on a non-saturated specimen. In the wet run, a saturated specimen allows the passage of air through pores when the capillary attraction of the wetting fluid is exceeded by the air pressure. As the air pressure is increased, smaller and smaller pores will pass air. In the dry run, air will flow through all pores when any amount of air pressure is applied to one side of the specimen. Both runs are performed in a sealed chamber. The flow rate through the sample from zero pressure to a maximal pressure is measured during each run. Assuming a cylindrical shape of pores, the pore size distribution is then computed.
Needle-punched and heat-bonded, polypropylene continuous filament nonwoven geotextiles have been tested during the program. The geotextiles were selected based on manufacturing process and their basic physical properties, mass per unit area and thickness.
Results, in terms of indicative pore sizes obtained from the pore size distribution are compared to the selected properties of geotextile products (thickness, mass per unit area and mass per unit volume), and the filtration opening size (FOS), determined by the hydrodynamic sieving technique (CGSB 148.1, method 10–94).
Relationships between measured pore sizes and selected properties of geotextiles have been found.
Research is presently in progress to widen the application of the CFP technique to measure the pore sizes up to 300 micrometers by using a non-zero contact angle wetting fluid and to verify the CFP technique applicability for other types of geotextiles, as well.
Knowledge of the PSD will be helpful in filter design because it focuses on new structural parameters of geotextiles, not presently considered by conventional design procedures.
Wet Sieving as a European EN-Standard for Determining the Characteristic Opening Size of Geotextiles
Authors: Dierickx W , Myles B 
Published: March 2009

Three different sieving methods were put forward by national delegations to determine the characteristic opening size of geotextiles. A comparison of these methods was carried out by laboratories in Europe together with laboratories in China and North America.
The interlaboratory trials showed that wet sieving gave results with good agreement within narrow limits in all involved laboratories. The dry sieving procedure showed a larger spread of results, mainly due to several laboratories not respecting the rules laid down in the test procedure, moreover dry sieving is not appropriate for very fine textured geotextiles (O90 less than 100 μm). The results of the inter-laboratory hydrodynamic sieving showed a somewhat larger variation than the wet sieving procedure although sets of results were more or less of the same order.
The main constraints of the hydrodynamic sieving procedure were that before any results are available one or more days must pass (sieving time is 24 hours) and the apparatus which is not commercially available, is expensive and non-standard. As a result apparatus used for the hydrodynamic sieving all had slightly different constructions while for the wet sieving complying sieve apparatus was used by most laboratories.
Wet sieving has therefore been put forward as the preferred method for a European EN-standard. A detailed description of the advantages and some constraints of the wet sieving procedure and analysis will be given. Also the acceptance of the O90 as the determination criteria for pore size rather than the O95 is discussed.
Permeameter Research to Evaluate Geotextile Performance
Authors: Dierickx W 
Published: March 2009

The evaluation of the hydraulic performance of geotextiles from field experiments is not an easy task as it takes a long time before conclusions can be drawn. Laboratory research is the only possibility to evaluate the performance of various geotextiles in a relatively short period.
Permeameters with upward flow are used to achieve that purpose. As the flow of water through a soil is not a static process, an increasing hydraulic gradient is applied. Tests normally last three weeks. They allow the prediction of the risk of particle passage as well as the risk of blocking and clogging. However, results cannot be expressed as a gradient ratio only. The gradient ratio just gives an overall picture of the behavior of soil and envelope. To evaluate the hydraulic performance of the envelope, a comparison must be made between the evolution of the hydraulic gradient in the soil and the hydraulic gradient across the geotextile.
Permeameter tests designed to evaluate the performance of geotextiles require careful preparation and accurate execution. Not only soil types but also soil conditions may influence the final results. The experience with permeameter research is described and results are presented.
Evaluation of Geotextile Filter in a Collection System at Fresh Kills Landfill
Authors: Corcoran BW , Bhatia SK 
Published: March 2009

The New York City Department of Sanitation has retained consultants to design a leachate collection system for the Fresh Kills Landfill in New York City. Fresh Kills Landfill is regarded as the world's largest landfill. Because of an Order on Consent the landfill is required to have a leachate collection system by 1996. Design of the collection system includes a trench backfilled with granular material wrapped in a geotextile filter. The geotextile filter will be a critical component of the collection system and will be designed to meet soil retention and permeability requirements for the system. An existing leachate collection trench with a non-woven geotextile filter was constructed at the landfill in 1988. This collection trench and geotextile filter were exhumed, sampled and analyzed in 1993 to determine the effectiveness of the geotextile filter. Information gained from this study was utilized for the design of future leachate collection systems. Results of this study will be the subject of this paper.
This study was unique in the sense that a geotextile filter was used for the first time in the collection trench at the Fresh Kills Landfill. In addition an evaluation of its performance had not been investigated before. The geotextile filter was analyzed to determine the impacts of burial and filtration of leachate in a landfill environment on the hydraulic and mechanical properties of the material. Also, the potential for biological growth on the geotextile filter was investigated. Results of this study identified minor clogging of the geotextile filter due to soil particle retention within the pores of the non-woven material. A slight reduction in permittivity was observed due to particulate clogging.
Results of the Lifetime Round Robins Done in the Framework of the Semi M6 Solar Silicon Standardization Task Force
Authors: Schönecker AG , Koch W 
Published: March 2009

In the framework SEMI standardization activities the SEMI M6-85 “Specification for Silicon Wafers for Use in Photovoltaic Solar Cells” is revised by an European task force. After more than four decades of silicon solar cell development there is still no reliable and strong correlation between the achievable cell efficiency and the electronic bulk material of unprocessed silicon wafers. The minority carrier lifetime of unprocessed bulk material is considered to have the potential to deliver this correlation. Therefore, similar to solar cell efficiency measurements, an easily applicable, instrument independent measurement for minority carrier lifetime under realistic photovoltaic conditions is desirable.
Four lifetime round robins were finished until now and a fifth one is going on at the moment. Many lessons, like how to perform these round robins, what are the sample characteristics, what is the influence of measurement conditions and surface passivation, were learned. But although there is a steady progress in defining more accurate measurement and sample preparation conditions, there is still no general carrier lifetime measurement procedure available that could be used in the above mentioned standard.
Effect of Load Excursions and Specimen Thickness on Crack Closure Measurements
Authors: McMaster FJ , Smith DJ 
Published: March 2009

The effects of simple load excursions on fatigue crack growth and crack closure measurements in aluminum alloy 2024-T351 are presented. The crack closure loads were measured local to the crack tip in 6-mm and 14-mm-thick specimens, using an Elbert-type gage for measuring crack-tip opening displacement (CTOD). All specimens were manufactured from a single lot of 15.7-mm-thick plate. Preliminary tests to establish the level of crack closure for a given level of remote constant-am- plitude loading were also undertaken, with consistently different levels of crack opening and closing loads observed. Crack opening and closing stresses obtained from the Elber-type (CTOD) gage, when compared with those from a (global) clip gage, showed identical results for opening stresses, but crack closing stresses were approximately 15% to 20% higher in the CTOD measurements. The results apparently contradict many analytical closure models, which have crack closing stresses lower than crack opening stresses.
Simple overload, underload and over/underload cycles were performed. Differences in the number of post-overload retardation cycles for the two thicknesses, in the single overload test, were obtained. It was found that the 6-mm-thick specimen's fatigue life was two times larger than for the 14-mm-thick specimen. The measured opening stresses were found to be in general agreement with the trends obtained for the fatigue crack growth results. Greater fatigue lives were obtained in the overload tests, with subsequent higher crack opening stresses measured. After a certain number of cycles following an overload, constant-amplitude crack growth rates were restored. However, the crack opening stresses did not return to the preoverload constant-amplitude values, but increased relative to the preoverload constantamplitude crack opening stresses.
Effect of Periodic Compressive Overstrain Excursions on Crack Closure and Crack Growth Rates of Short Fatigue Cracks—Measurements and Modeling
Authors: Varvani-Farahani A , Topper TH 
Published: March 2009

A comparison of the growth of fatigue cracks under constant-amplitude straining and under strain histories having periodic compressive overstrains revealed that the fracture surface near the crack tip and the crack growth rate changed dramatically with the application of compressive overstrains. When the magnitude of compressive overstrains was increased, the height of the fracture surface irregularities was reduced as the increasing overstrain progressively flattened fracture surface asperities near the crack tip. The reduced asperity height was accompanied by a lower crack closure stress and a higher crack growth rate.
The fatigue strength was reduced by a factor that ranged from 1.24 at short lives (104 cycles) to 3.37 at long lives (107 cycles) when periodic compressive overstrains of near yield point magnitude were applied in uniaxial tests. The corresponding reductions in the fatigue strength for shear tests varied from 1.40 to 1.70.
A model of the plastic deformation of the fracture surface asperities at the crack tip (under periodic compressive overstrains) was developed to relate the crushing of the asperities to crack closure and crack growth rate. The model correlates the magnitude of the periodic compressive overstrain, the fracture surface asperity height, and the plastically flattened area to the fully effective strain intensity factor range (ΔKeff) and its ratio to the range of strain intensity factor (ΔK(ε)) obtained from constant-amplitude straining, U =ΔKeff/ΔK(ε).
For both uniaxial and shear fatigue straining, the strain range at a fatigue life of 107 cycles for constant-amplitude straining (Δεfl) and the effective strain range, (Δεeff.fl) at 107 cycles in the strain-equivalent life curve, obtained from strain histories containing periodic compressive overstrains, were used to calculate the U ratio (U= Δεeff.fl /Δεfl). These values were close to those obtained from the model.
The Development of Acoustic Emission for Leak Detection and Location in Liquid-Filled, Buried Pipelines
Authors: Miller RK , Pollock AA , Finkel P , Watts DJ , Carlyle JM , Tafuri AN , Yezzi JJ 
Published: March 2009

Acoustic Emission leak detection and location for liquid-filled, buried pipelines was studied using various leak sources and laboratory reference standards.These standards provided significant data that have contributed to the development of test procedures for generating two-phase flow and a better understanding of the leak mechanism. Results are discussed for leak signal enhancement due to two-phase flow, leak orientation and the presence of backfill surrounding the pipe.
Field studies were performed on buried pipes to demonstrate that small leaks (less than 0.1 gallons/hour or 0.1 mL/second) can be detected under the right test conditions and that the location of these small leaks can be determined using a variety of location methods. Among the different location methods examined was a location technique referred to as “tuned” linear location. In addition, a modification to the conventional Signal Difference location technique is discussed.
Comparison of a Lognormal and Normal Distribution in Calculating Concentrations for a Superfund Risk Assessment
Authors: Mahoney LA , Batey JC , Pintenich JL 
Published: March 2009

A baseline risk assessment (RA), was conducted for a Superfund site in the Southeast. The site is a former landfill, with associated localized soil and groundwater contamination. There was concern for the potential for the landfill to contaminate groundwater which is used as the regional drinking water supply source.
During the baseline RA, 95 percent upper confidence limits (UCLs) on the arithmetic mean were calculated for groundwater assuming both a normal and lognormal distribution. The UCLs were then used to estimate potential risks associated with the worst-case exposure scenario.
The purpose of this paper is to illustrate how the assumption of the data distribution can influence the results of the calculation of statistics of measured concentrations, and subsequently, associated risk estimates. Groundwater was the medium which was evaluated for this study, however, the process and results could be applicable to any environmental medium.
The Role of Orchex® 796 in Pesticide Applications
Authors: Chambers GV 
Published: March 2009

A renewed interest in improving the application of chemical pesticides has prompted additional application research on utilizing spray adjuvants for enhancing ground or aerial pesticide applications. This renewed interest is producing additional findings on the role of Orchex® 796 in pesticide applications, as well as research leads for improving pesticide formulations. This paper reviews these additional findings, primarily from published research.
While Orchex® 796 was initially developed for tree pests, its general surface chemistry and other lipid-like properties provide improved spreadability and coverage on biological surfaces. Further, both plant and insect surfaces are modified in a beneficial manner for the application of many pesticides. In addition to providing a temporary modification of the target surface, other properties improve rainfastness. These features provide a greater benefit in ultra low volume application including nonaqueous application, but still retain benefits when applied with even high rates of water, such as in chemigation. Specific crop and pest examples are presented from both temperate and tropical agriculture. These examples illustrate how Orchex 796 properties can provide a multiple role in the formulation or application of pesticides.
Phosphate Ester Compositions by Design
Authors: Reierson RL 
Published: March 2009

A fundamental mechanistic study of the alcohol phosphation process has provided a basis for development of a phosphation system which can be systematically varied to produce alkyl phosphate mixtures of predetermined composition. Conventional phosphation with either polyphosphoric acid or phosphoric anhydride typically produces the compositional extremes in terms of the ratio between the monoalkyl and dialkyl phosphate products. Use of both reagents will produce intermediate products in terms of the monoalkyl to dialkyl phosphate (MAP:DAP) ratio which vary as a function of the process. Parameters can be adjusted to produce MAP : DAP molar ratios from about 50 : 50 to 90 : 10 with low residual phosphoric acid and unreacted alcohol levels.
In this preliminary communication, examples of the range of accessible compositions and limits of the technology are presented.
Suspoemulsions with Improved Stability and Correlation of Long Term Stability with the Zeta Potential
Authors: Memula S , Berger P , Chellappa C 
Published: March 2009

The word stability is ambiguous in colloidal science and means different things for different people. In suspoemulsions or concentrates it is possible to identify at least three different physical processes which may lead to instability in a particulate system. For example change in particle size may be due to Ostwald's ripening, particle aggregation and particle sedimentation. Therefore an understanding of behavior of fine particles, and their interactions with the inert ingredients in a suspoemulsion or suspension formulation is necessary to develop a stable formulation. The behavior of these fine particles in aqueous suspoemulsion is a cumulative function of electrostatic, steric and hydrophobic interactions with the inert ingredients and other physical processes.
This paper discusses the processes and techniques involved in the stabilization of suspoemulsion / suspension concentrates. A Model pesticidal formulations was chosen to study the effect of surfactant system on the stability of the formulation and its dilution performance. Further attempts were made to correlate the physical long term stability of the formulation with change in particle size, distribution and Zeta potential measurements.