bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing for Pesticide Toxicity to Aquatic Plants: Recommendations for Test Species
Authors: Swanson SM , Rickard CP , Freemark KE , MacQuarrie P 
Published: March 2009

A literature review of pesticide toxicity to aquatic plants was conducted in order to arrive at a set of species for use in preregistration testing. Criteria used in the selection process were: (1) existing database; (2) interspecies variability in response to pesticides; (3) availability of well-characterized plant cultures; and (4) ease of culture. Freshwater and marine algae and freshwater and estuarine macrophytes were included in the study.
Results showed that the three practical criteria [1,3,4] all resulted in the selection of unicellular green algae (Chlorophyceae) for the freshwater algae tests. However, variability among freshwater species and classes was so great and so unpredictable that it became obvious that a species battery approach was required. The battery should consist of representatives of each of the major algal classes. Research into culture methods and alternative endpoints is required before species other than unicellular green algae can be routinely incorporated into species battery tests.
The studies in the marine algal database had much more consistent methodology; therefore, it was possible to include relative sensitivity and variability as well as practical considerations in the selection of marine tests species. The golden-brown algae (Chrysophyceae) were generally the most sensitive. However, because variability in response was still high, we recommend a species battery for marine algae as well. Four species of golden brown alga, two diatoms (Bacillariophyceae) and two green algae, were chosen based on the four criteria.
Macrophytes should be part of preregistration testing because they can be more sensitive than algae and because of their ecological importance. The database showed a great variety of test methods and very few laboratory methods. No species emerged as the most consistently sensitive among either freshwater or estuarine macrophytes. Lemna gibba and Lemna minor are fast growing, easy to culture, and available commercially; they are logical test species for effects of pesticide drift and surface films. However, they are not always very sensitive. Rooted macrophytes belong in a comprehensive test program; however, test methods have to be developed.
One criterion not included in this study was ecological importance. We recommend that ecological importance become part of any selection process in order to facilitate extrapolation to the field during hazard assessments.
Toxicity Testing Using a Chemostat-Grown Green Alga, Selenastrum Capricornutum
Authors: Peterson HG 
Published: March 2009

Regulatory toxicity testing with algae commonly use 72- or 96-h inhibition of growth by the green algae Selenastrum, Chlorella, or Scenedesmus. The long incubation period is sufficient for the algae to change the composition of the test medium. Organism-induced changes include the release of organics and the uptake of nutrients with accompanying pH changes. Both the released organics and the variable pH can change the chemical speciation of the toxicants; this may alter their toxicity. In addition, the competitive interactions between hydrogen ions and toxicants can affect toxicity as the pH varies. It is shown here that cadmium (Cd) toxicity to Selenastrum capricornutum increases by up to eight times for every unit of pH increase. Copper (Cu) with its different speciation pattern does not vary as much as Cd, and the pattern is different. Because the toxicity of the two metals vary differently with pH, Cd is 500 times less toxic than Cu at pH 6, but Cd is twice as toxic as Cu at pH 10.
The present regulatory protocols call for nutrient-sufficient conditions, but algae are likely to be limited by either nitrogen (N) or phosphorus (P) in nature. Here, Selenastrum has been grown in chemostats with both N and P approaching limiting levels. Inhibition of N and P uptake, rather than growth, has been used to assess toxicity in short-term experiments. The advantage of chemostat, rather than batch cultivation (as used in present regulatory tests), is the ability to produce algae of known and well-defined physiological states.
Detecting Ambient Cadmium Toxicity in an Ecosystem
Authors: Stewart-Pinkham SM 
Published: March 2009

The threshold for a toxic effect from cadmium is close to its background levels. In experimental studies, chronic low-dose exposure does not necessarily increase body burden and causes effects associated with other stressors; therefore, low-dose effects from environmental sources are hard to establish using traditional approaches. The effects of ambient cadmium have increased with the precipitous drop in lead in the atmosphere. They are manifested by increased stress responses. In a community exposed to cadmium fumes from waste incineration, one can infer cadmium effects in such observed environmental stresses as increased seeding in trees, tree injuries, and learning and behavioral problems in children.
Biochemical effects of free cadmium, rather than the levels of cadmium burden or accumulation, need to be assessed in multiple biological systems, especially trees and humans. Environmentally bioavailable cadmium can be detected more accurately by assaying multiple metals in hair, leaves, lichens, and house dust. The hypothesis that cadmium is released with stress and/or mediates the stress response should be directly tested through carefully designed scientific studies.
Response of Sago Pondweed, a Submerged Aquatic Macrophyte, to Herbicides in Three Laboratory Culture Systems
Authors: Fleming WJ , Ailstock MS , Momot JJ , Norman CM 
Published: March 2009

The phytotoxicity of atrazine, paraquat, glyphosate, and alachlor to sago pond-weed (Potamogeton pectinatus), a submerged aquatic macrophyte, was tested under three types of laboratory culture conditions. In each case, tests were conducted in static systems, the test period was four weeks, and herbicide exposure was chronic, resulting from a single addition of herbicide to the test vessels at the beginning of the test period. The three sets of test conditions employed were: (1) axenic cultures in 125-mL flasks containing a nutrient media and sucrose; (2) a microcosm system employing 18.9-L buckets containing a sand, shell, and peat substrate; and (3) an algae-free system employing 0.95-L jars containing reconstituted freshwater and a nutrient agar substrate. The primary variable measured was biomass production.
Plants grew well in all three test systems, with biomass of untreated plants increasing by a factor of about 5 to 6.5 during the four-week test period. Biomass production in response to herbicide exposure differed significantly among culture systems, which demonstrates the need for a standardized testing protocol for evaluating the effects of toxics on submerged aquatic plants.
Application of a Plant Test System in the Identification of Potential Genetic Hazards at Chemical Waste Sites
Authors: Gill BS , Sandhu SS , Backer LC , Casto BC 
Published: March 2009

In situ evaluations of biological effects of chemicals from industrial waste sites provide an assessment of potential health hazards to humans under the complexities of natural environment. For such studies, plants, being cost effective and suitable for multimedia exposure, are ideal for preliminary investigations for hazard identification. Several native plant species have been used as biomonitors for providing an integrated response to the bioavailability of chemical toxicants in the real-world environment.
We have utilized the Tradescantia micronucleus (Trad-MCN) assay for evaluating genetic hazards at a chemical waste site contaminated with agricultural insecticides scheduled for cleanup under the Superfund program. The chemical analysis of soil samples from the site indicates presence of lindane, beta BHC, and heptachlor in the subsurface samples. Tradescantia plants were planted at five locations to evaluate the mutagenic effects of the total environment, i.e., soil, water, and air. In addition, stem cuttings were also placed at these locations to sample the genetic impact of vapor phase organics in the atmosphere. Surface and subsurface samples were obtained from these locations for chemical and biological analysis in the laboratory. Concurrent laboratory and field controls were maintained in Durham, NC.
Results of Tradescantia exposures at the site showed significantly higher frequencies of micronuclei from contaminated plots before remediation, but no genetic activity was detected after the remedial action. Plants exposed to soil samples in the laboratory yielded nonsignificant results except for one subsurface sample before remediation and two surface samples after remediation. From comparison of plants exposed in the laboratory and under natural conditions, we concluded that genetically effective levels of volatile organics were present at the site before remediation. This study demonstrates the utility of simple bioassays for detecting environmental hazards at chemical waste sites.
Economical Design of Shelf Angles
Authors: Tide RHR , Krogstad NV 
Published: March 2009

General guidelines for the design and construction of shelf angles supporting masonry veneers in high-rise buildings can be found in several published documents. Examples of shelf angles in service have been found, however, where failures did not occur even though many of these guidelines were not followed. In one such case, no significant yielding or excessive deflection was observed even though the stresses in the steel predicted by traditional analysis greatly exceeded yield stresses and the computed deflection of the angle exceeded the expansion joint width.
This paper reviews the performance of shelf angles taking into account several boundary conditions and factors that are commonly overlooked in design but that have substantial effect on the actual performance. A procedure is outlined for the economical and rational design of shelf angles. Included are procedures for the sizing of shelf angles, for determining the spacing of connections, and for designing and detailing connections to the building structure. Examples are given to show how the procedure would be used in the design process.
Frictional Characteristics of Clay Brick Pavers
Authors: Trimble BE , Kulakowski BT 
Published: March 2009

The use of brick as a paving material has a long history. Over the past few years brick has again been specified in vehicular areas. Engineers are now requesting information on the skid resistance properties of brick. A research project was undertaken to determine brick's skid resistance, as well as to compare brick's frictional characteristics with those of other paving materials. It was also desired to determine if skid resistance correlated with other physical properties of brick.
Tests using the British Pendulum Tester confirmed that these brick have excellent frictional characteristics. It was also determined that skid resistance does not correlate with brick's compressive strength, abrasion index nor cold water absorption.
A Comparative Review of Various Test Meteods for Evaluating the Water Penetration Resistance of Concrete Masonry Wall Units
Authors: Driscoll ME , Gates RE 
Published: March 2009

Water damage to masonry either directly or indirectly as a result of freeze-thaw action has long been a concern to the construction industry. Over the years, the industry has developed a number of tests to measure leakage in masonry walls. However, little attention has been given to the correlation between these tests and the factors that contribute to water penetration and leakage. The forces that compel liquid water from the outside of a masonry wall into the interior of the building are: capillary forces - the propensity for water to “wick” in porous materials or through hairline cracks kinetic forces - the kinetic energy of a wind-driven rain will force it into the depth of the wall pressure differential - net pressure differentials caused by ventilation and air conditioning systems may cause the water to pass through small defects in the wall gravity - under gravity water can drip in through imperfections in flashing and parapet walls surface tension - water will tend to follow an easily wet surface, even turning around corners and edges such as in soffits, shelf angles, and loose laid metal flashing.
This paper reviews the effectiveness of existing water penetration and leakage tests such as the ASTM E 514 Test Method for Water Permeance of Masonry, RILEM tube test, AAMA 501.2-83 and other similar tests in predicting the resistance of masonry walls to water penetration caused by one or more of these forces. The authors further suggest a simple test method to complement the existing ones. A theoretical treatment of these forces and their effects upon water penetration is discussed in a separate paper.
Comparison of Laboratory Freeze-Thaw Procedures
Authors: Vickers MA 
Published: March 2009

The failure modes of three laboratory freeze-thaw procedures are compared with field failures. Sets of fifteen plant-fired brick were selected. Five brick from each set were subjected to each procedure.
Two omni-directional procedures were used: The Standard Method as set forth in ASTM C67, Standard Methods of Sampling and Testing Brick and Structural Clay Tile (with a 4-h cold water saturation), and a modified ASTM (with a 5-h boil saturation).
One uni-directional method was used: The Face Freeze-Thaw Procedure. This procedure was developed in the Acme Brick Company Research Laboratory, Denton, Texas, and utilizes the 5-h boil saturation. After each freeze cycle, only the face of the brick is thawed while the body remains frozen. The test specimens are withdrawn after 100 cycles, or when a specimen has failed. A sample is considered to have failed when a laminar crack develops parallel to the brick face. The crack usually develops 10–15 cycles before the face comes off.
A Theoretical Model of Water Penetration into Concrete Masonry Units
Authors: Barkofsky PR , Driscoll ME 
Published: March 2009

The effect of water damage on masonry walls is well known, and a variety of test methods have been developed to measure the susceptibility of masonry to the forces that drive water within wall systems. Several test methods and their correlation to these forces are discussed in a separate paper.
This paper offers a qualitative model of water penetration that relates the inherent properties of masonry and the external conditions to which it is exposed to its ability to resist water leakage.
Darcy's equation of flow through porous media describes the resistance to flow offered by the tortuous networks of channels in a permeable material and quantifies the force necessary to overcome this resistance. Considering the environmental conditions that a wall is exposed to, we can modify Darcy's equation and use it to characterize masonry's propensity for water transmission driven by the forces of rain velocity, capillary pressure, differential air pressure, and gravity based on masonry material properties. In addition, with data typical of environmental exposure characteristics, the singular and additive effects of these forces can be computed and compared.
Innovative Aspects of Leachate Containment with Composite Slurry Walls: A Case History
Authors: Manassero M , Viola C 
Published: March 2009

The main technological and construction features of a composite cement-bentonite slurry wall carried out for containment of subsoil pollution due to a chemical plant located in the northern part of Italy, are presented.
The subsoil profile shows a high permeability sand and gravel layer, 3 to 15 m thick, underlined by a natural low permeability stratum of overconsolidated and cemented clay, more than 150 m thick.
The solution adopted for remedial works was aimed to gain advantage from subsoil conditions which were nearly ideal for cut-off barrier effectiveness.
Design approach, preliminary and final checks are also described in the paper.
Deep Foundation Elements Installed by Slurry Wall Techniques
Authors: Johnson EG , Johnson KE , Erikson CM 
Published: March 2009

Deep foundation units, installed using slurry wall techniques, are generally referred to as Barrettes or Load Bearing Elements (LBEs). This paper reviews examples and applications of this foundation type, and describes two case studies in which these units were utilized in Boston.
Current design issues and construction installation details are presented. The design discussion focuses on the selection of foundation type and load transfer into the bearing stratum. Issues related to construction include excavation equipment and stabilization, bottom cleanup, installation of reinforcement, tremie concrete placement, and quality control during installation. for both case studies, the LBEs were installed for projects constructed by the “up/down” method, which is described in the paper. Although there are some unique advantages when used with this construction method, the selection of LBEs should be considered for conventional construction as well.
Construction of Diaphragm Wall at Wells Dam East Embankment
Authors: Roberts DL , Ho D-M 
Published: March 2009

A concrete diaphragm wall was constructed at the Wells Dam east embankment to cutoff seepage. Sinkholes were observed on the embankment crest in early 1990, more than 20 years after the construction of the embankment dam. After extensive investigations a diaphragm wall was adopted to positively cutoff seepage and to stop internal erosion.
The wall was excavated in vertical panels with clam shell bucket through the embankment core and riverbed deposits overlying bedrock to a maximum depth of 70 m (230 ft). A total of 11,600 sq m (125,000 sq ft) of diaphragm wall was constructed. The success of the wall was evaluated based on core drilling, water tests, piezometer data and geophysical survey after the construction.
This paper presents a brief description of the project and sinkhole investigations, with the main emphasis placed on the construction of the concrete diaphragm wall, including procedure, quality control and verification, and difficulties.
Infrastructure: The Battlefield of Corrosion
Authors: Fasullo EJ 
Published: March 2009

Our nation's decaying infrastructure and its associated cost have put the engineering community on the alert. All responsible parties must cooperate to save and extend the life expectancy of these vital structures. Innovative ideas for the accurate prediction and determination of the condition of the various structures is needed badly. New testing techniques that use state-of-the-art, computerized equipment need to be developed.
Time is running out. We can no longer postpone the maintenance of our infrastructure. Thus, new financial ways and means have to be developed to pay the cost. The public and private sectors have to join forces to get the job done quickly and at an affordable cost.Our educational institutions also have to take a very active role to educate future generations and engrave in their minds the importance of preserving and maintaining existing structures. New approaches to educating engineers may be needed. Innovation in engineering design solutions must be encouraged by dealing with the issues of professional liability and establishing an engineering fee structure that rewards new ideas.
A New Approach to Power-Model Regression of Corrosion Penetration Data
Authors: McCuen RH , Albrecht P , Cheng J 
Published: March 2009

Corrosion penetration data have traditionally been fit with the power model using a log transformation of both the exposure time and the penetration. The transformation has several disadvantages, including (1) the resulting model gives biased estimates of the penetration, (2) the sum of the squares of the errors in penetration are not minimized even though the sum of the squares of the logarithmic errors are minimized, and (3) the logarithmic transformation results in greater emphasis being placed on the penetration for the shorter exposure times.
An alternative method of fitting power models is discussed. The numerical calibration method is shown to produce better fitting and more rational power models than is provided with a logarithmic transformation. Unbiased power models can also be fitted. The fitting procedure is more complex than that for the log transform method.
The two fitting methods were compared using 32 sets of corrosion penetration data. The average standard error ratio for the numerical procedure was 58 percent of that for the logarithmic analyses, which suggests that the numerical procedure consistently produced better penetration estimates for the largest measured exposure time. Thus, more accurate 75-year projections of penetration should be expected with the numerical model. Analyses of the records suggest that record lengths of at least 10 years are necessary to produce accurate model coefficients.
Performance of Rehabilitated/Protected Concrete Bridge Decks
Authors: Babaei K , Hawkins NM 
Published: March 2009

This paper is based on a research study aimed at determining the relative effectiveness of three bridge deck protective systems (i.e., latex-modified concrete (LMC) overlay, low-slump dense concrete (LSDC) overlay, and cathodic protection (CP) in preventing or halting reinforcing steel corrosion and corrosion-induced deterioration in salt-contaminated concrete. The paper documents the results of testing five LMC, five LSDC, and two CP bridge decks. The test bridges had experienced severe corrosion-induced deterioration and/or severe salt contamination before protection. At the time of testing the average age of both the LMC and LSDC overlays was about seven years, and the average age of the CP installations (slotted system) was five years. Also, among the concrete overlaid decks, seven had been subjects of previous similar investigations. Thus, the study determined changes in the effectiveness of concrete overlay protective systems with time.
The mode of internal concrete fracture caused by reinforcing steel corrosion and its magnitude were determined. Performance information was expressed in terms of corrosion-induced deterioration as well as rate of corrosion-induced deterioration. A criterion was established for the condition beyond which deterioration impairs deck serviceability. Accordingly, the effective service lives of the rehabilitated/protected decks were estimated. Also, the performance information was analyzed for factors affecting the condition of a rehabilitated/protected deck. Overlay surface cracking and overlay thickness were found to affect the corrosion-induced deterioration in the concrete overlaid decks. Correlations were made between those factors and the deterioration. In CP decks various types of concrete deterioration were found, their magnitudes were measured, and their causes were identified. Those types of deterioration, generally, were not related to corrosion of reinforcing steel. The cost-effectiveness of concrete overlay and cathodic protection strategies were determined on the basis of bridge deck life-time costs and compared.