Carpet Fibers Research Articles

RETRACTED: Durability performance of green concrete composites containing waste carpet fibers and palm oil fuel ash

Cleaner production is a pressing concern of the 21st century. Waste materials resulting from different industrial processes requires proper management to ensure a cleaner environment. The use of recycled materials in new green concrete production is very attractive due to the low-cost related to the waste materials in addition to saving required space for landfill purposes and the development as well as improvement in the concrete properties. This paper focuses on the durability properties of green concrete composite, which comprised of waste polypropylene (PP) carpet fiber and palm oil fuel ash (POFA). Properties studied include slump and VeBe time of fresh concrete as well as water absorption, sorptivity, chloride penetration, carbonation, and drying shrinkage of hardened concrete. Carpet fiber of 20 mm in length and six volume fractions of 0–1.25% were used with ordinary Portland cement (OPC). Another six concrete mixes were cast whereby OPC was replaced by 20% POFA. It was observed that the combination of PP carpet fiber and POFA decreased the slump values and increased the VeBe time of the fresh concrete mixes. In addition, water absorption, sorptivity, chloride penetration, and carbonation depth of the concrete composite for both OPC and POFA content mixtures were reduced with the addition of carpet fiber, with volume fractions of up to 0.75%. The positive interaction between carpet fibers and POFA subsequently led to the lower drying shrinkage of the concrete composite. The influences of POFA on the durability performance of concrete was observed to be more significant at longer curing periods. The findings of the study demonstrated that there is a promising future for the use of waste carpet fibers as a fibrous material in the production of a green and durable concrete. Green concrete also minimizes solid wastes, improves air quality, and leads to sustainable cement and concrete industry.

Analysis of Strip Footings on Fiber-Reinforced Slopes with the Aid of Particle Image Velocimetry

AbstractThis paper provides results of a comprehensive investigation into the use of waste carpet fibers for reinforcement of clay soil slopes. The interaction between laboratory scale model slopes made of fiber-reinforced clay soil and surface strip footing load was examined. Results for the influence of two variables, namely fiber content and distance between the footing edge and the crest of the slope, are presented and discussed. The particle image velocimetry (PIV) technique was used to study the deformation of the slope under the surface loading. The front side of the tank was made of a thick Perspex glass to facilitate taking accurate images during the loading stage. To study the stress induced in the slope under footing pressure, excess pore-water pressure and total stress increase were measured at predetermined locations within the slope. The results showed that fiber reinforcement increased the bearing resistance of the model slope significantly. For instance, inclusion of 5% waste carpet fiber ...

Effect of fiber material on ozone removal and carbonyl production from carpets

Indoor air quality is affected by indoor materials such as carpets that may act as sources and/or sinks of gas-phase air pollutants. Heterogeneous reactions of ozone with carpets may result in potentially harmful products. In this study, indoor residential carpets of varying fiber types were tested to evaluate their ability to remove ozone, and to assess their role in the production of carbonyls when exposed to elevated levels of ozone. Tests were conducted with six types of new unused carpets. Two sets of experiments were conducted, the first measured ozone removal and ozone deposition velocities, and the second measured primary carbonyl production and secondary production as a result of exposure to ozone. The tests were conducted using glass chambers with volume of 52 L each. Air exchange rates for all tests were 3 h−1. The ozone removal tests show that, for the conditions tested, the polyester carpet sample had the lowest ozone removal (40%), while wool carpet had the greatest ozone removal (65%). Most carpet samples showed higher secondary than primary carbonyl emissions, with carpets containing polypropylene fibers being a notable exception. Carpets with polyester fibers had both the highest primary and secondary emissions of formaldehyde among all samples tested. While it is difficult to make blanket conclusions about the relative air quality merits of various carpet fiber options, it is clear that ozone removal percentages and emissions of volatile organic compounds can vary drastically as a function of fiber type.

Kernel-based methods for source identification using very small particles from carpet fibers

The objective comparison of complex signals in chemistry, and more particularly in forensic chemistry, with the view of inferring the source of a particular ‘trace’ object is an ongoing issue. In this paper, we propose a method that enables to assign a probability distribution to control material from any given source based on its chemical signal and to subsequently infer the source of a trace object using a simple Bayes classifier. Our method takes advantage of the dimension reduction and discriminative powers of kernels, and only requires the estimation of three parameters (once a kernel is chosen). We illustrate the application of our method to the inference of the source of trace objects based on very small particles (VSP) that can be found on their surfaces. VSPs are picked up in the environment(s) where the trace object has been in. These VSPs can (1) offer information about the geographic origins of the objects; (2) help discriminate between multiple mass-manufactured objects that would be otherwise identical. In this project, we use VSPs recovered from carpet fibers throughout the United States and apply our method to (1) reduce the complexity of compositional data obtained by SEM/EDS; (2) infer the source of the trace material. This method can be extended to VSPs found on other types of recovered forensic materials such as weapons, drugs, or IEDs (improvised explosive device), and to other types of chemical signals.

Green concrete production incorporating waste carpet fiber and palm oil fuel ash

With the increasing amount of waste generation from various processes, there has been a growing interest in the utilization of waste in producing building materials to achieve potential benefits. This paper highlights the results of an experimental investigation on the performance of concrete incorporating waste carpet fiber (WCF) and palm oil fuel ash (POFA) as partial replacements of ordinary Portland cement (OPC). Six volume fractions varying from 0 to 1.25% of 20-mm-long carpet fiber were used with OPC concrete mixes. Another six mixes were made that replaced OPC with 20% POFA. The specimens were cured in water and tested for fresh and hardened state properties. The combination of WCF and POFA decreased the slump values and increased the VeBe time of fresh concrete. The addition of WCF to either OPC or POFA concrete mixes did not improve the compressive strength or modulus of elasticity. At 91 days, the compressive strength was in the range of 38.1–49.1 MPa. The positive interaction between WCF and POFA, however, leads to high tensile and flexural strengths, thereby increasing the concrete ductility with higher energy absorption and improved crack distribution. The maximum increases in tensile and flexural strengths compared to those of plain concrete were achieved by the addition of 0.5% carpet fiber at the age of 91 days. The ultrasonic pulse velocity (UPV) was examined and was classified as good quality concrete. The study showed that the use of waste carpet fiber and palm oil fuel ash in the production of sustainable green concrete is feasible both technically and environmentally.

Utilization of environmentally acquired very small particles as a means of association

Very small particles (VSP) are ubiquitous in our environment and are virtually ignored by forensic science. These particles range in size from an order of magnitude smaller than conventional trace evidence, down to the molecular level. Combinations of VSP provide an extraordinary, largely untapped resource for forensic associations and source attribution. This paper describes an initial effort to exploit VSP for one specific application.An approach was developed and tested for the SEM/EDS analysis of VSP recovered from the surfaces of carpet fibers – one of the most common types of trace evidence examined in crime laboratories. Our goal was to exploit existing computer-assisted SEM/EDS methods to test whether VSP profiles could be useful to associate shed fibers with a source carpet.Particles were harvested by washing and filtration onto polycarbonate filters. An SEM/EDS analysis protocol currently employed for environmental particle analyses was used, resulting in individual particle characterization based on fitting to reference spectra of 28 elements. Target Particle Types were defined based on the most abundant elemental profiles and used to bin the results for each specimen, resulting in a Target Particle Type profile.Within-carpet variability was assessed using Target Particle Type profiles from three different areas on each of nine carpets. Area profiles, defined from sets of ten fibers, were compared to profiles from individual fibers. Between-item variation was explored using a survey of an additional 12 carpets.Hundreds to thousands of VSP were found to routinely occur on individual carpet fibers. Their quantity and character was sufficient to associate fibers with their area of origin. Within-carpet variations showed roughly even distributions for most TPTs and between-carpet variations showed wide ranges in types and quantities of VSP.Environmentally acquired VSP showed clear potential to provide quantitative means to link carpet fibers with their area of origin. This finding is noteworthy, since such particles are acquired post-manufacture and are independent of characteristics determined by manufacture. More generally, VSP are ubiquitous, present on or in virtually any item, and there is the potential for linkages among items of any type based on adhering VSP. By way of example, the present work provides impetus for a fundamental change in the way that forensic trace evidence is conceptualized. Further fundamental research is indicated to better understand the underlying variability, usefulness and limitations of this approach.

Exploitation of very small particles to enhance the probative value of carpet fibers

Environmentally acquired very small particles (VSP), present on the surfaces of carpet fibers, have shown potential for the association of fibers with their carpet source. To unlock this potential, research is required addressing a number of areas, including the application of methods under realistic casework conditions and the utilization of computational methods for the refinement and testing of the approach.In this work field collections of carpet fibers were conducted by crime scene practitioners under realistic casework conditions. VSP were isolated using previously developed methods, and analyses were conducted using SEM/EDS analytical protocols in an operational crime laboratory setting. Computational methods were designed, allowing sets of hundreds to thousands of VSP to be characterized. Classifiers were designed to associate and discriminate among specimens. These classifiers were applied to the VSP data for specimens collected by crime scene practitioners, as well as to a previously collected research dataset. Quantitative measures of correspondence and probative value were designed based on the classification measures and successfully applied to both sets of VSP data.Particle sets larger than 500 showed strong promise for quantitative associations with their sources. The use of larger numbers of target particle types (TPTs) showed strong promise to improve the performance of classification and association.Overall, the usefulness of VSP to provide objective, quantitative associations has been established. Because VSP are acquired post-manufacture, these methods can address fundamental limitations to probative value that arise when class characteristics, determined by manufacture, are shared among mass produced commodities.These findings are of broad significance for the future of trace evidence analysis. The results of this research are likely extendable, with minor modifications, to other trace evidence types (such as glass, tape and human hair), and are expected to contribute significantly for those types of trace evidence that have long been considered of low evidential value (such as undyed cotton and animal hairs). Furthermore, entirely new approaches to trace evidence are enabled by exploiting VSP profiles, such as comparing different types of trace evidence with one another and comparing VSP defined by crime scene or suspect environments to those on virtually any item of physical evidence.

STRENGTH, MODULUS OF ELASTICITY AND SHRINKAGE BEHAVIOUR OF CONCRETE CONTAINING WASTE CARPET FIBER

This paper presents test results on some physical and mechanical properties of concrete containing fiber from recycled carpet waste. Five concrete mixes namely plain concrete (PC) i.e. concrete without carpet fiber, as control and carpet fiber reinforced concrete (CFRC) mixes containing 0.5%, 1.0%, 1.5% and 2.0% polypropylene (PP) waste carpet fibers were made and tested for compressive, tensile and flexural strengths, modulus of elasticity and shrinkage at curing periods of 1, 7 and 28 days. It has been found that the addition of carpet fiber reduced the workability and density of concrete. Concrete containing carpet fiber exhibited lower compressive strength and modulus of elasticity than plain concrete. The carpet fibers, however, effectively improved the splitting tensile and flexural strengths of concrete. The obtained values of shrinkage revealed that the shrinkage strain of carpet fiber reinforced concrete was higher than that of plain concrete. On the basis of short-term investigation, the one-year shrinkage values of both plain concrete and concrete containing carpet fiber were also predicted by extrapolating the data obtained during this period. The results obtained in this study indicate that waste carpet fiber can suitably be used as fiber reinforcement in concrete with satisfactory performance.

Lemonade

Lemonade Daniel Riddle Rodriguez (bio) Your grandmother is on her deathbed now. She made it a long time ago. Which is to say it was made for her. Which really means she doesn’t want it but she’s going to lie down anyway. You prop her pillows for her, lace her lemonade with Demerol because she is dying and dying hurts you. She says so herself. She says: Dying hurts, You! Then she downs her lemon and painkiller cocktail. Two gulps and her eyes go gaga inside the tiny thing that you know is her head. It looks like an onion now. A piece of old fruit. A fermenting thing. She says it tastes funny sometimes. The lemonade. She makes a face like she is turning a thumbscrew but the thumbscrew is her face. Like this . . . The living room is a rest haven for white noise. The air dense, tart with the copper-coin smell of your grandmother and tv dinners. Sitting in her dusty wingback, she stabs blindly at chicken fried steak with an oyster fork, watches tv. This time it isn’t mash. Tonight is courtroom drama, a police procedural: cigarette smoke in the interrogation room, good cop bad cop. You sit next to your grandmother, finger the lace doilies, and work the remote. She coughs pieces of herself onto the floor while you explain the nuances: He’s the one who did it, Ma. Nights like these you dissolve pieces of black tar in a Visine bottle, sniff deeply to keep from nose-diving into carpet fibers. The detective on the show plays the hambone card, the perp wilting under a combination of palm strikes and police jargon: Where you’d hide the body, pervo? [End Page 133] But mostly it was mash. Hunnicutt and Hawkeye. Witty repartee. She likes to hold your hand while you watch. You don’t really like that. Her hands are scary, a pair of liver-spotted carcasses barely held by the skin that keeps them. The way twice-boiled chicken slides groaning off the bone, only to plummet back into the soup, releasing itself from itself. Your grandmother is like that—a thing awaiting release. Your grandmother is like a chicken. Does it hurt? you say to her. Being a chicken? Only when I’m thirsty, she says, pointing to the cup. You need to renew her prescription soon. No traffic on the way to the pharmacy today. Bockman Road is all pedestrians: kids playing ball, playing house, hooky. A sheriff in a blue Charger follows you for a while, riding your tail, before taking the filtering lane toward Hayward and out of the Village. San Lorenzo’s changing the way unincorporated towns are apt to: one failed mom-and-pop at a time. You reconcile, assign events monumental to the shifting landscape. There’s the strip mall that shoulders the clock tower. There’s the corner where bums converge, tweekers posing as vets and vice versa, to ply their trade: dumpster dive for bottles, for cans, a bit of copper if the cards are right. You know their trade well, were part of the same union once, paid dues. Outside the pharmacy, one of them—a man with a pushcart and a tiny dog, terrier maybe—offers you a paper cup and the chance to fill it. Just fifty cents, man, he says, shaking the cup. For the bus, man, the bus. Judging from the shallow pool of coins in the cup, the bum’ll still be swimming in garbage long after the buses stop running. Maybe even a jaunt through the city dump for loose metal to fill the cart, cap off the night. That shit has some squeaky wheels, you say. He smiles. But I push this muthafucka, right? Point A, Point B. He shakes the Dixie again. You toss him a grubby single. ‘‘Where you going to park it?’’ The bum puts a finger over his lips like wouldn’t you like to know. God bless you, boss, he says, pantomiming a priest, crossing the air between you. He pushes the cart into the street. Point B is waiting, he says, to himself but maybe not...

Storm water harvesting and reuse in Australia: enhanced sand filtration for the treatment of storm water

This study details the removal of common storm water pollutants along with heavy metals by enhanced sand filtration. Three filtration flow rates were trialled: 5, 10 and 20 m/h. The performance of each filter was rated on the ability to remove turbidity, suspended solids, dissolved solids, phosphorus, nitrogen, lead, copper and Zinc. Conventional sand filter was used as a performance benchmark, and compared with four sand filters that are enhanced with a nylon carpet fibre, polypropylene carpet fibre, Syrian carpet fibre-enhanced and alum sludge-enhanced sand filter. Carpet fibre-enhanced sand filtration was highly effective at filtering simulated storm water and in most cases performing well above the conventional sand filters. The carpet fibre-enhanced sand filters had no drop in flow rates over the 4 h filtration period with following removal rates: up to 90% total suspended solids, 70% zinc, 60% turbidity, 25% phosphorus, 15% nitrogen and 10% total dissolved solids. However, results showed that alum sludge-enhanced sand filter performed the highest, with removal rates up to 100% for total suspended solids, 80% zinc, 90% turbidity, up to 80% phosphorus, up to 40% nitrogen and 3% total dissolved solids. But the flow rates dropped approximately two-thirds of the original flow rates within the first hour.

PHYSICAL AND MECHANICAL PROPERTIES OF CONCRETE CONTAINING FIBERS FROM INDUSTRIAL CARPET WASTE

Fiber reinforcement can effectively improve the mechanical properties of concrete. Utilization of recycled fibers from post-consumer and industrial waste offer some benefits such as waste reduction and resource conservation and also low-cost materials and reduced need for landfilling. Carpets are one of the major components of waste materials around the world, which is 1-2% of all solid wastes by volume. Industrial carpets are mainly made of polymeric materials such as Nylon and Polypropylene fibers. This study was carried out on different tests of the concrete containing fibers from Malaysian industrial carpet waste following the DOE mix design for the investigation of the physical and mechanical properties of concrete. Compressive, splitting tensile and flexural tests were performed with a fiber volume fraction range of 0.5-2%. A decrease in compressive strength and workability was observed as a function of carpet fiber content. However, the addition of carpet fiber leads to enhance the splitting tensile strength, flexural strength and reducing the crack-size and a smoother mode of failure, unlike the brittle failure behavior of plain concrete. Physical and mechanical properties of concrete containing fibers from industrial carpet waste.

Small-strain properties of soft clay treated with fibre and cement

ABSTRACT: To improve the dynamic properties of soft soil, the cement treatment technique combined with fibre reinforcement can be employed. In this study, the effects of two types of fibres (polypropylene and recycled carpet) on the hardening process and small-strain properties of cement-treated kaolinite and bentonite clays are investigated. Cement-treated clay specimens were prepared using cement contents of 5%, 10% and 15% by weight of dry soil for the kaolinite samples, and 30%, 40% and 50% for the bentonite samples. To investigate and understand the influence of different fibre types and contents, three different percentages of fibre content were adopted: 0.1%, 0.2% and 0.5% polypropylene fibres, and 0.5%, 0.75% and 1% carpet fibres. The results of bender element tests on 126 cylindrical samples of cement-treated clay with various cement and fibre contents were analysed to discern the relationships between fibre and cement content and the small-strain mechanical properties, including the shear wave velocity and maximum small-strain shear modulus of the treated soil. The influence of fibres and cement contents on the hardening time of treated soil has also been investigated.

Shrinkage Properties of Soft Clay Treated with Cement and Geofibers

In this study, effects of two types of geofibers, namely polypropylene and recycled carpet, on three dimensional shrinkage properties of cement treated kaolinite and bentonite clays are investigated. Cement treated clay specimens were prepared with cement contents of 5, 10, and 15 % by weight of dry soil for kaolinite samples, and 30, 40 and 50 % for bentonite samples. To investigate and understand the influence of different fiber types and contents, three different percentages of fiber content (i.e. 0.1, 0.2 and 0.5 % polypropylene fibers; and 0.5, 0.75 and 1 % carpet fibers) were adopted. The results of shrinkage tests on 126 cylindrical samples of cement treated clay with various cement and fiber contents were analysed to understand the relationships between these parameters and the shrinkage percentage of treated soil. Results of this study indicate that combination of cement and fiber is effective in reducing the volume change of clayey soils undergoing drying process. In the applied ranges of cement and fiber contents, the influence of cement addition on the shrinkage reduction is more significant than the addition of fibers for the treated kaolinite. However, addition of fibers in curtailing the shrinkage of bentonite clay is more significant than the cement addition.

Fluorochemical concentration and distribution analysis using portable XRF instrument in carpet industry

This article introduces the use of a portable X‐ray fluorescence (XRF) instrument as a non‐destructive tool to rapidly determine fluorochemical concentration on carpet fibers. Most portable XRF instruments are not capable of detecting the primary element in fluorochemicals, fluorine (F) directly. However, fluorochemicals may be combined with chemical taggants, which are measurable. When properly calibrated, the taggant concentrations are a proxy for the F level on carpet fibers, which in turn represents fluorochemical concentration. Results in this research showed that an accuracy of 150 ± 50 ppm of F can be achieved using a portable XRF instrument. This level and accuracy range is specified by manufacturers as an acceptable fluorochemical concentration on carpet fibers. Therefore, a portable XRF instrument can be used in place of the certified chemical burn test, thereby reducing the response time to obtain test results from hours for the chemical burn test to less than 5 min when using the portable XRF technology. This online measurement system for fluorochemical concentration can also be used as a practical means of determining fluorochemical distribution profiles across carpet samples. Copyright © 2013 John Wiley & Sons, Ltd.

An Obesogen over Time: Transgenerational Impact of Tributyltin

Vol. 121, No. 3 News | Science SelectionsOpen AccessAn Obesogen over Time: Transgenerational Impact of Tributyltin Wendee Nicole Wendee Nicole Search for more papers by this author Published:1 March 2013https://doi.org/10.1289/ehp.121-a96Cited by:2View Article in:中文版AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit The term “obesogen” describes a chemical that promotes excessive weight gain by increasing adipocyte (fat cell) size or number, changing metabolism to favor fat storage, or altering the control of appetite and satiety. Previous studies have suggested that prenatal exposure to obesogens can alter metabolism in mice and predispose multipotent mesenchymal stem cells (MSCs) to become fat cells, but whether these changes last through subsequent generations was unknown. A team of researchers investigating this question exposed pregnant mice to tributyltin (TBT) and found impacts on adipogenesis through the third generation [EHP 121(3):359–366; Chamorro-Garcia et al.].TBT, which has been used as a biocide in marine paints and in textile products such as carpets, is a persistent organic pollutant that is ubiquitous in the environment. Exposure to TBT is thought to occur through many sources, including food, house dust, and consumer products.In the current study, male offspring (i.e., the F1 generation) of mice exposed to TBT during pregnancy showed marked increases in the number and size of white fat cells and significant but less pronounced increases in the weight of white fat deposits (or “depots”) around the kidney and under the skin. The two subsequent generations (F2 and F3) also showed increases in fat cell size and number and, at the two higher TBT doses, in fat depot weight. Females showed more modest differences following TBT prenatal exposure, including both increases and decreases in cell numbers, depending on location.Once used to fight mites and fungi in carpets and other textiles, TBT has been found in house dust, which is thought to be a major source of human exposure. This dust sample—which was not tested for TBT—is made up of carpet fibers (blue), cotton fibers (green), synthetic fibers (yellow), small stones (gray), dirt particles (dark brown), skin flakes (beige), and a feather.© Eye of Science/Science SourceThe team also found that F3 animals in the TBT group showed substantially increased expression of adipogenic markers in bone marrow–derived MSCs and decreased expression of osteogenic (bone lineage) markers—in other words, the stem cell population appeared reprogrammed to create fat instead of bone. The shift was more pronounced in males in all generations, and especially in the F3 generation.When the team looked at accumulation of lipids in the livers of each generation, they found that TBT-exposed F1 males and females showed marked increases in lipid accumulation; F2 and F3 generations also showed less pronounced increases in liver lipids. The investigators also found significant increases in the expression of hepatic genes related to fat creation and storage in males and females from all three generations of mice.F1 animals were exposed to TBT as fetuses, and F2 animals were potentially exposed as germ cells within the F1 fetuses. F3 animals were not exposed to TBT, yet they exhibited signs characteristic of exposure. This is the first known study to show that prenatal exposure to low, environmentally relevant concentrations of an obesogen led to transgenerational effects on white fat volume, altered stem cell programming, and liver fat accumulation in multiple generations of mice.FiguresReferencesRelatedDetailsCited by Badr El Dine F, Nabil I and Dwedar F (2017) The effect of Tributyltin on thyroid follicular cells of adult male albino rats and the possible protective role of green tea: a toxicological, histological and biochemical study, Egyptian Journal of Forensic Sciences, 10.1186/s41935-017-0012-z, 7:1, Online publication date: 1-Dec-2017. Brtko J and Dvorak Z (2015) Triorganotin compounds - ligands for “rexinoid” inducible transcription factors: Biological effects, Toxicology Letters, 10.1016/j.toxlet.2015.02.009, 234:1, (50-58), Online publication date: 1-Apr-2015. Vol. 121, No. 3 March 2013Metrics About Article Metrics Publication History Originally published1 March 2013Published in print1 March 2013 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Indoor Residence Times of Semivolatile Organic Compounds: Model Estimation and Field Evaluation

Indoor residence times of semivolatile organic compounds (SVOCs) are a major and mostly unavailable input for residential exposure assessment. We calculated residence times for a suite of SVOCs using a fugacity model applied to residential environments. Residence times depend on both the mass distribution of the compound between the "mobile phase" (air and dust particles settled on the carpet) and the "non-mobile phase" (carpet fibers and pad) and the removal rates resulting from air exchange and cleaning. We estimated dust removal rates from cleaning processes using an indoor-particle mass-balance model. Chemical properties determine both the mass distribution and relative importance of the two removal pathways, resulting in different residence times among compounds. We conducted a field study after chlorpyrifos was phased out for indoor use in the United States in 2001 to determine the decreases in chlorpyrifos air concentrations over a one-year period. A measured average decrease of 18% in chlorpyrifos air concentrations indicates the residence time of chlorpyrifos is expected to be 6.9 years and compares well with model predictions. The estimates from this study provide the opportunity to make more reliable estimates of SVOCs exposure in the indoor residential environment.

Performance of dust allergen carpet samplers in controlled laboratory studies

Allergens and other pollutants in house dust are collected using a variety of dust samplers that are assumed to operate similarly. This factorial design study compared sampler performance under controlled environmental conditions. House dust with known particle sizes (212-90, 90-45, and <45 μm) and allergen concentrations were sampled from new carpet squares with varying denier, pile height and pile densities. Dust mass and allergen recovery for total dust mites (Der p 1 and Der f 1), cat (Fel d 1) and cockroach allergen (Bla g 1) were assessed using the Eureka Mighty Mite (EURK), the High Volume Small Surface Sampler (HVS), or the American Industrial Hygiene Association (AIHA) method. Allergen concentrations were quantified using enzyme-linked immunosorbent assays, and dust mass results were corrected for carpet fiber shedding. Samplers were compared by exploring mass collection efficiency (CE=fiber corrected dust mass/applied dust mass) and concentration ratio (CR=allergen concentration in collected sample/allergen concentration in test dust). Test dust allergen concentrations varied by particle size fraction due to varying laboratory performance over time. The EURK and HVS samplers had CEs of 41-63% in the small and medium particle size fractions, and collected less than 20% of the available dust from the large size fraction. The AIHA CE ranged from 10% to 17% in the medium and small particle size fractions, but collected little dust in the largest particle size fraction. The AIHA and HVS samplers were more likely to acquire more representative and less variable allergen CRs compared with the EURK method. Health studies that use allergen concentration as an exposure metric need to consider the implications of sampler performance when interpreting links to health outcomes and development of health-based standards for allergens in house dust.

Mechanical characteristics of soft clay treated with fibre and cement

ABSTRACT: In this study, the influence of three types of fibre – polypropylene, recycled carpet and steel – on the mechanical properties of cement-treated clay is investigated. Cement-treated clay specimens were prepared with cement contents of 5%, 10% and 15% by weight of dry soil, and cured for 14 days. To investigate and understand the influence of different fibre types and contents, three different percentages of fibre content were adopted. The results of unconfined compression tests on 90 cylindrical samples of cement-treated clay with varied cement and fibre contents are analysed to discern the relationships between these parameters and the key mechanical properties, including unconfined compressive strength and stiffness of treated soil. Furthermore, indirect tension test results of a further 90 treated soil samples have been used to determine the influence of fibre and cement content on the tensile strength of the treated soil. The fibre reinforcement increases the peak compressive strength. The addition of fibres increases the residual strength and changes the brittle behaviour of the cement-treated clay to that of a more ductile material. The tensile strength of the cement-treated clay is increased by adding carpet and steel fibres, but small quantities of polypropylene fibres do not influence the tensile strength.

Floating treatment wetlands for domestic wastewater treatment

Floating islands are a form of treatment wetland characterized by a mat of synthetic matrix at the water surface into which macrophytes can be planted and through which water passes. We evaluated two matrix materials for treating domestic wastewater, recycled plastic and recycled carpet fibers, for chemical oxygen demand (COD) and nitrogen removal. These materials were compared to pea gravel or open water (control). Experiments were conducted in laboratory scale columns fed with synthetic wastewater containing COD, organic and inorganic nitrogen, and mineral salts. Columns were unplanted, naturally inoculated, and operated in batch mode with continuous recirculation and aeration. COD was efficiently removed in all systems examined (>90% removal). Ammonia was efficiently removed by nitrification. Removal of total dissolved N was ∼50% by day 28, by which time most remaining nitrogen was present as NO(3)-N. Complete removal of NO(3)-N by denitrification was accomplished by dosing columns with molasses. Microbial communities of interest were visualized with denaturing gradient gel electrophoresis (DGGE) by targeting specific functional genes. Shifts in the denitrifying community were observed post-molasses addition, when nitrate levels decreased. The conditioning time for reliable nitrification was determined to be approximately three months. These results suggest that floating treatment wetlands are a viable alternative for domestic wastewater treatment.

Utilization of recycled post consumer carpet waste fibers as reinforcement in lightweight cementitious composites

Purpose – A large amount of post‐consumer carpet waste is discarded into landfills. The need to recycle this waste is increasing due to the lack of available landfill spaces in many parts of the world, environmental concerns, and resource conservation. The purpose of this paper is to explore the use of this waste for a low‐cost, high‐volume application.Design/methodology/approach – Fibers from carpet waste have been successfully used as reinforcement in concrete, typically at 0.1‐1 per cent volume fraction (fractions by weight are even lower), for enhanced toughness. In this study, lightweight cementitious composites were fabricated that were reinforced with recycled carpet fibers at up to 20 per cent fiber to cement weight ratios. Flexural, toughness, and impact properties of the lightweight cementitious composites were characterized.Findings – The density of the composites decreases with the increase of fiber content. In the three‐point bending test, lightweight cementitious composites exhibited a ducti...