bluuebunny/crossref_metadata_2025 huggingface dataset:
Age Trends in Femur Stresses From a Simulated Fall on the Hip Among Men and Women: Evidence of Homeostatic Adaptation Underlying the Decline in Hip BMD
Authors: Beck Thomas J , Looker Anne C , Mourtada Firas , Daphtary Maithili M , Ruff Christopher B
Published: August 2006

Age trends in proximal femur stresses were evaluated by simulating a fall on the greater trochanter using femur geometry from hip DXA scans of 5334 white men and women in the NHANES III survey. Expansion of femur outer diameter seems to counter net bone loss so that stresses remain similar across age groups, but stresses are higher in older women than in older men.

Introduction: The age decline in hip BMD is caused by both bone loss and expansion of outer diameter that increases the region size over which mass is measured in a DXA scan. Because expansion has an opposing effect on structural strength, it may be a homeostatic adaptation to net bone loss to ensure that load stresses are kept within a narrow range.

Materials and Methods: Age trends in femur stresses were evaluated with an engineering beam simulation of a fall on the greater trochanter. Hip geometry was extracted from hip DXA scans using the Hip Structure Analysis (HSA) software on 2613 non-Hispanic white men and 2721 women from the third National Health and Nutrition Examination Survey (NHANES III). Using body weight as load, stresses were computed on the inferior-medial and superior-lateral femur neck at its narrowest point and the medial and lateral shaft 2 cm distal to the midpoint of the lesser trochanter. Stresses and the underlying geometries in men and women >50 years oaf age were compared with those 20–49 years of age.

Results: Compared with men <50 years of age, stresses in older men were 6% lower on both surfaces of the shaft, 4% lower on the inferior-medial neck, and not different on the superior-lateral neck. In women >50 years of age, stresses on the proximal shaft and inferior-medial neck remained within 3% of young values but were 13% greater on the superior-lateral neck. Neck stresses in young women were lower on the superior-lateral than the inferior-medial neck, but lateral stress increased to the level on the medial surface in older women. Stresses were higher in women than in men, with a greater gender difference in those >50 years of age.

Conclusions: We conclude that femur expansion has a homeostatic effect in men and women that opposes bone loss so that stresses change little with age. Because expansion preserves stresses with progressively less bone mass, the process may reduce structural stability in the femoral neck under fall conditions, especially in the elderly female.
Effects of Systemic and Local Administration of Recombinant Human IGF-I (rhIGF-I) on De Novo Bone Formation in an Aged Mouse Model
Authors: Fowlkes John L , Thrailkill Kathryn M , Liu Lichu , Wahl Elizabeth C , Bunn Robert C , Cockrell Gael E , Perrien Daniel S , Aronson James , Lumpkin Charles K
Published: August 2006

DO was used in an aged mouse model to determine if systemically and/or locally administered rhIGF-I improved osteoblastogenesis and new bone formation. Local and systemic rhIGF-I treatment increased new bone formation. However, only systemic delivery produced measurable concentrations of rhIGF-I in the circulation.

Introduction: Human and rodent research supports a primary role for IGF-I in bone formation. Significant roles for both endocrine and paracrine/autocrine IGF-I have been suggested for normal osteoblastogenesis and bone formation. We have assessed, using a mouse model of distraction osteogenesis (DO), the impact of continuous administration of recombinant human (rh)IGF-I, delivered either locally to the distraction site or absorbed systemically, on bone formation in an aged mouse model.

Materials and Methods: DO was performed in aged mice (18-month-old C57BL/6 male mice), which were distracted at 0.15 mm daily. At the time of osteotomy, miniosmotic pumps were inserted subcutaneously to (1) deliver vehicle or rhIGF-I subcutaneously for systemic delivery or (2) deliver vehicle or rhIGF-I directly to the newly forming bone through infusion tubing routed subcutaneously from the pump to the distraction site. Serum concentrations of mouse IGF-I, human IGF-I, and osteocalcin were determined at the end of the study.

Results: New bone formation observed in DO gaps showed a significant increase in new bone formation in rhIGF-I–treated mice, irrespective of delivery route. However, detectable levels of human IGF-I were found only in the serum of animals receiving rhIGF-I systemically. Osteocalcin levels did not differ between controls and rhIGF-I–treated groups.

Conclusions: Locally and systemically delivered rhIGF-I both produce significant increases in new bone formed in an aged mouse model in which new bone formation is normally markedly impaired, suggesting that rhIGF-I may improve senile osteoporosis. Because systemic administration of IGF-I can result in untoward side effects, including an increased risk for cancer, the findings that locally delivered IGF-I improves bone regeneration without increasing circulating IGF-I levels suggests that this delivery route may be preferable in an at-risk, aged population.
Forecasting Annual Harvests of Atlantic and Gulf Menhaden
Authors: Hanson Peter J. , Vaughan Douglas S. , Narayan Sridhar
Published: August 2006

Continuous records of annual landings and fishing effort exist in the Atlantic purse-seine fishery for Atlantic menhaden Brevoortia tyrannus since 1940 and the Gulf of Mexico fishery for Gulf menhaden B. patronus since 1946. Currently, year-ahead forecasts of landings from these species-specific fisheries separated by the Florida peninsula are provided to the industry by means of multiple-linear-regression models that relate landings and effort over the data series. Here, we compare three methods for this purpose—multiple regression, time series, and artificial neural networks—to determine whether forecast accuracy can be increased. Best-fit models were developed with each method for each fishery, and then 10-year retrospective analyses of 1-year-ahead catch forecasts were compared among the three methods. In general, multiple-regression and artificial neural network models were similar in their fit to the data series and both were better than time series models, judging from the Akaike information criterion, the correlation between observed and predicted catches, the mean prediction error, and the root mean square error of prediction. A 10-year retrospective analysis (1993–2002) of 1-year-ahead catch forecasts indicates that the three methods provided similar within-stock mean absolute forecast errors (19–21% in the Atlantic and 15–20% in the Gulf), with generally better forecasts for the Gulf fishery. Overall, multiple-regression and artificial neural network models provide lower average catch forecast errors and better fits to the fishery data, whereas similar forecast errors are provided by a univariate time series model (autoregressive integrated moving average model) in the Atlantic and a multivariate time series model (state space model) in the Gulf.
Bottlenecks to Fishery Yield for American Lobster in a Portion of the Gulf of St. Lawrence
Authors: Miller Robert J. , Mallet Manon , Lanteigne Marc , MacMillan Robert
Published: August 2006

Egg production, larval survival, and migration of large benthic stages are considered to be possible bottlenecks to fishery yields for the American lobster Homarus americanus in the eastern Northumberland Strait, southern Gulf of St. Lawrence. Egg production, measured as eggs per trap haul and stage I larval production, was high compared with that of surrounding areas with greater fishery yield. The only area that could have supplied larvae by drift supported average egg production. Low levels of postlarvae developed from this average to high egg production, implicating low larval survival as the proximal cause of low fishery yield. A scarcity of small lobsters in the catch over several decades also indicated that recruitment was low and that the fishable stock was supported by immigration. Because of this spatially variable relationship between egg production and fishery yield, we recommend setting management targets specific to an area.
Differences in Population Metrics between Bluegill and Redear Sunfish: Implications for the Effectiveness of Harvest Restrictions
Authors: Sammons Steve M. , Partridge David G. , Maceina Michael J.
Published: August 2006

Bluegills Lepomis macrochirus and redear sunfish L. microlophus were collected and aged from three reservoirs in Georgia and Alabama in 2003–2004 to describe population metrics and investigate the potential of harvest restrictions to maintain or improve the size structure of these populations. Redear sunfish grew faster and lived longer than bluegills in all three reservoirs, and estimated natural mortality was greater for bluegills than for redear sunfish; however, total annual mortality was similar between the species in two of the three reservoirs. Population dynamics models did not predict any significant benefits to bluegill size structure and yield from minimum length or bag restrictions. In contrast, redear sunfish populations in each study reservoir showed significant increases to size structure and minimal decline in yield from various harvest restriction scenarios. Because of higher mortality and slower growth in bluegills, harvest restrictions probably will not positively affect their size structure without an unacceptable decline in yield. However, our results indicated that harvest restrictions may have greater potential in managing redear sunfish populations. For redear sunfish, yield was not drastically affected by minimum length limits, but after implementation of harvest restrictions the number of larger, preferred-length (≥230-mm) fish could increase by over an order of magnitude in moderately to highly exploitative fisheries. Finally, results of this study have demonstrated that the common practice of managing sunfish as a homogenous group may not be appropriate, particularly if the fishery is composed of a diverse array of sunfish species that are targeted by anglers.
Promotion of weed species diversity and reduction of weed seedbanks with conservation tillage and crop rotation
Authors: Murphy Stephen D. , Clements David R. , Belaoussoff Svenja , Kevan Peter G. , Swanton Clarence J.
Published: August 2006

In a 6-yr study on four farms (36 fields) in Ontario, Canada, we tested the effects of tillage (moldboard, chisel plow, no tillage) and crop rotations (continuous corn, corn-soybean, corn-soybean-winter wheat) on emerged and seedbank weed species diversity and density. Aside from the imposed experimental treatments, all other management was generally consistent among farms. Tillage had the largest effect on weed diversity and density. No tillage promoted the highest weed species diversity, chisel plow was intermediate, and moldboard plow resulted in the lowest species diversity. These results are consistent with ecological succession theory. The increase in weed species diversity resulted from 20 species being associated with no tillage systems, 15 of which were winter annuals, biennials, or perennials. Emerged weed density was affected only by tillage. Over 6 yr, seedbank declined in no-tillage systems from 41,000 to 8,000 seeds m−3. Crop yields were not affected by tillage or crop rotation. In practical terms, reduced tillage in combination with a good crop rotation may reduce weed density and expenditures on weed management.
Mechanism of paraquat tolerance in cucumber leaves of various ages
Authors: Kuk Yong In , Shin Ji-San , Jung Ha Il , Guh Ja Ock , Jung Sunyo , Burgos Nilda R.
Published: August 2006

Differential sensitivity to paraquat was observed between cucumber cultivars and leaf age. Physiological responses to paraquat, including antioxidative enzyme activity, were investigated in leaf age classes of cucumber to identify mechanisms of paraquat tolerance. Leaf injury for ‘Naeseosamcheok’, ‘Daehandadagi’, ‘Baekgwangdadagi’, ‘Sangrokheukjinju’, and ‘Eunseongbaekdadagi’ cultivars was less than that of six other cultivars tested, averaged over leaf age and herbicide rate. The level of foliar injury caused by paraquat was Leaf 1 > 2 > 3 > 4 in seven of 11 cultivars used, where 4 was the youngest leaf. There was a positive correlation between leaf age and its relative susceptibility to paraquat, regardless of growth stage. Lipid peroxidation was less in the youngest leaf (Leaf 4) than in the older leaves at all herbicide concentrations. The youngest leaf had higher values for apparent photosynthesis than the oldest leaf. Differential leaf response to paraquat was partially correlated with the change in superoxide dismutase, ascorbate peroxidant, and glutathione reductase activities in treated leaves. Enzyme activity of ascorbate peroxidase (APX) was higher in Leaf 4 than in Leaves 1, 2, or 3 in untreated plants and after exposure to paraquat. APX isozymes were more abundant in treated than in untreated leaves and produced in higher amounts in younger than in older leaves. Application of ascorbate and glutathione before paraquat treatment protected cucumber leaves from paraquat injury.
Soybean row spacing and weed emergence time influence weed competitiveness and competitive indices
Authors: Hock Shawn M. , Knezevic Stevan Z. , Martin Alex R. , Lindquist John L.
Published: August 2006

Weed competitiveness can be quantified with the concept of competitive index (CI), a relative scale of weed competitiveness. Field studies were conducted in 2002 and 2003 in northeastern and southeastern Nebraska to evaluate the influence of soybean row spacing and relative weed emergence time on the competitiveness of major weed species in soybean. Ten weed species were seeded in soybean spaced 19 and 76 cm apart at the planting, emergence, and first trifoliate leaf stages of soybean. Total weed dry matter (TDM), weed plant volume, and percent soybean yield loss were arbitrarily selected as a base for determining the CI for each weed species. Soybean yield loss was the least variable parameter used to quantify weed competitiveness and rank their CIs. In general, weeds grown with soybean planted in 19-cm rows produced less TDM, plant volume, and reduced soybean yield less than weed species grown in 76-cm rows. Later-emerging weeds produced less TDM, plant volume, and reduced soybean yield less than the early-emerging ones. In general, broadleaf species were more competitive than grass weed species. Common sunflower was the most competitive weed species in this study.
Variation in postdispersal weed seed predation in a crop field
Authors: Jacob Helen Spafford , Minkey David M. , Gallagher Robert S. , Borger Catherine P.
Published: August 2006

Postdispersal weed seed predation by animals during the summer fallow period may lead to a reduction in the number of weeds that grow in the following winter cropping season. In this study, we investigated the patterns of weed seed removal, the influence of crop residue cover on seed removal, the types of granivores present and their seed preferences in a 16-ha postharvest cropping field in Western Australia during the summer months over 2 yr. Seed removal from caches was extremely variable (from 0 to 100%). Removal rates were generally highest along the edges of the field near bordering vegetation and lowest in the center of the field and within the bordering vegetation. However, there were many deviations from this general pattern. There was no change in rates of predation with different levels of residue cover. Ants or other small invertebrates were found to remove the most seeds. However, seed removal by other animals, such as rodents, was also evident. Annual ryegrass seeds were preferred over wild oat seeds, followed by wild radish pod segments. Seed harvesting was lowest in late January, peaked in February, and decreased in March. Results from this study suggest seed harvesters could reduce the number of surface seeds in the field, reducing the weed seed bank. Management options that increase the activity of the seed harvesters may lead to less variability in seed predation and could, therefore, be incorporated into an integrated weed management program.
Iron antagonism of MSMA herbicide applied to bermudagrass: characterization of the Fe2+-MAA complexation reaction
Authors: Massey Joseph H. , Taylor James M. , Binbuga Nursen , Chambers Kristen , Coats G. Euel , Henry William P.
Published: August 2006

Discoloration of bermudagrass often results from application of MSMA herbicide used to control southern crabgrass and other weeds. However, when products containing iron sulfate (FeSO4) are tank-mixed with MSMA, this discoloration is reduced. Experiments investigated the effect of tank-mixing organic arsenical herbicides with FeSO4or a chelated iron source (Sprint 330) in terms of southern crabgrass control and injury to bermudagrass. Tank-mixing MSMA with FeSO4reduced bermudagrass injury. However, southern crabgrass control was also reduced by at least 50% with the addition of ≥0.38 kg Fe2+ha−1. Neither antagonism nor safening of bermudagrass was observed when the chelated Fe2+source was used. Applying FeSO4as a separate treatment 1 to 4 d before or after MSMA application did not reduce visual burmudagrass injury 1 wk after treatment. Solution pH and FeSO4concentration controlled the extent of complexation and level of antagonism observed in the field; inorganic Fe2+reacted with MSMA to form a complex having reduced herbicidal activity. Potentiometric and spectrophotometric investigations found that methylarsonate, the parent acid of MSMA and other organic arsenical herbicides, reacts with inorganic Fe2+to form a stable 1:1 Fe2+-methylarsonic acid chelate having two points of metal coordination and a stability constant log10(β) = 2.77 ± 0.04. Tank-mixing MSMA with FeSO4to protect against bermudagrass injury negates the benefit of applying the herbicide for weed control, and therefore is not a recommendable practice for turf managers.
Weed community and corn yield variability in diverse management systems
Authors: Smith Richard G. , Gross Katherine L.
Published: August 2006

The effects of crop rotation and management system on annual variability in weed communities and crop yields were assessed in a 4-yr study in Michigan. Variability of the weed community and corn yields were assessed using the coefficient of variation (CV) and a multivariate dissimilarity index (Bray-Curtis) that accounted for changes in both weed species abundance and composition. The treatments included two rotations: continuous corn and a corn–corn–soybean–wheat rotation, and two management systems: conventional (CONV) and organic-based (ORG). Weed biomass was significantly higher in the ORG system; however, there was no effect of crop rotation on weed biomass or number of weed species in a treatment (species richness). Annual variability in weed community composition and structure was affected by both crop rotation and management system and was highest in the ORG rotation. In contrast to the weed community, variability in corn yield was highest in the least-diverse cropping system (CONV monoculture), despite that system having a more constant weed community. Corn yield in the ORG rotation was not significantly different from that in the CONV monoculture. Results of this study suggest that management aimed at increasing cropping system diversity may have additional effects on weed communities and crop yields beyond those commonly reported, and these may have important implications for the development of more efficient and sustainable weed and crop management practices.
Planting date affects phenology of London rocket (Sisymbrium irio) and interaction with beet leafhopper (Circulifer tenellus)
Authors: Ray Jarren , Schroeder Jill , Creamer Rebecca , Murray Leigh
Published: August 2006

London rocket is a common winter annual weed in southern New Mexico that can host beet curly top virus and its insect vector, the beet leafhopper. Experiments were conducted in southern New Mexico to determine if London rocket could serve as a host for overwintering beet leafhopper. Field experiments were carried out from 2002 to 2003 and from 2003 to 2004 to compare the impact of three London rocket planting dates on plant emergence and life history and leafhopper survival. Emergence was highest in October-planted London rocket, low in January/February plantings, and did not occur for August plantings. The life cycle was 185 d and 125 d for October- and January-planted London rocket, respectively, and growth of the plant (including height and rosette base diameter) was greater for London rocket that was planted in October. October-planted London rocket survived from late October through mid to late April, the period of time needed to serve as an overwintering host for beet leafhoppers. Caging the plants to assess beet leafhopper survival did not affect rate of plant growth, but it reduced the time to flowering for October-planted London rocket and increased the height and weight of plants. Beet leafhoppers were able to survive for approximately 2 mo in early winter or spring on caged London rocket plants.
Annual weed competitiveness as affected by preemergence herbicide in corn
Authors: Liphadzi Konanani B. , Dille J. Anita
Published: August 2006

Competitiveness of weeds that survive a PRE herbicide application (escaped weeds) might be altered because of herbicide injury. As a result, potential crop yield loss may be reduced. Field experiments were conducted at Ashland Bottoms, KS, in 2001 and 2002 and at Rossville, KS, in 2002. The objectives were to quantify corn growth and yield response to Palmer amaranth or velvetleaf competition, with or without isoxaflutole (0.03 kg ha−1) or flumetsulam (0.04 kg ha−1) application, and to determine seed production of Palmer amaranth or velvetleaf as affected by PRE herbicide. Palmer amaranth and velvetleaf densities ranged from 0 to 6 and 0 to 32 plants m−1of corn row, respectively. At Ashland Bottoms in 2002, corn height at tasseling decreased with increasing Palmer amaranth (1.58 cm weed−1m−1) and velvetleaf (1.32 cm weed−1m−1) density when no herbicide was applied. With flumetsulam application, each increase in velvetleaf density reduced corn height by 0.4 cm. Escaped Palmer amaranth and velvetleaf were shorter than untreated plants at corn tasseling. At Rossville in 2002, Palmer amaranth that escaped isoxaflutole or flumetsulam application caused 13% corn yield loss (YL) at a density of 3 plants m−1. In contrast, corn YL from untreated Palmer amaranth at the same density was 30%. At Ashland Bottoms in 2002, velvetleaf that escaped flumetsulam caused 3% corn YL at a density of 3 plants m−1compared with 38% YL caused by untreated velvetleaf at the same density. Seed production of Palmer amaranth was independent of density or herbicide treatment, whereas production of velvetleaf seed increased with density, with or without flumetsulam. The study showed that corn YL from both Palmer amaranth and velvetleaf that escaped a PRE herbicide was less than from untreated weeds, but seed production by escaped weeds was similar to that of untreated weeds.
Decision-support tools for sustainable drainage
Authors: Scholz M.
Published: August 2006

The contribution of sustainable drainage systems (Suds) to the overall catchment dynamics of Glasgow and Edinburgh was studied. Seventy-nine sites in Glasgow and 103 sites in Edinburgh were identified for initial investigation, including a site feasibility assessment and a desk study relating to planning issues that may be relevant for subsequent future development, regeneration and retrofitting options. Detailed design guidelines were drafted for representative demonstration areas in both cities. Glasgow and Edinburgh are dominated by regeneration and retrofitting sites, respectively. Combinations of swales or infiltration trenches with ponds or below-ground storage cells were the most likely Suds options for the majority of the demonstration areas. Practical Suds decision-support tools (key, matrix and model) were developed to help identify appropriate Suds techniques for potential Suds sites. A decision-support model was developed by the author, his research team and senior planners, and provides the civil engineer with a novel practical tool to assess the suitability of different Suds techniques for a particular site with and without applying his or her own judgement. The Suds model (latest draft version on http://www.see.ed.ac.uk/research/IIE/research/environ/uw12.html ) should be applied to other urban sites with similar characteristics to those in Glasgow and Edinburgh.
Creating walkable urban environments
Authors: Barnett S.
Published: August 2006

Society is looking for increasingly technological answers to solve imminent transport crises, yet walking is often overlooked as a viable alternative for short trips. A complex matrix of factors affects the decision of whether or not to walk. Providing a street environment and public realm that encourages walking will, however, start to create a better balance in our villages, towns and cities, making it easier to choose to walk. Urban environments that have high levels of walking benefit the local community in many ways, in terms of health, social capital and local economic stability. Delivering high-quality walking environments requires an understanding of generic pedestrian issues such as accessibility for all users, designing out crime and connectivity. But delivery also requires specific local knowledge. Utilising local knowledge at the start of any scheme helps avoid costly mistakes and ensures that any improvements actually meet the needs of local people. In situ consultation reinforces ideas and helps local people express and explain the issues. Living Streets has applied this approach in different urban environments including London and Preston and also through the Walkability Project.Working in four similar district centre sites has allowed the identification of ten recurring issues faced by pedestrians.
Banked realignment: a case study from the Humber Estuary, UK
Authors: Pontee N. I. , Hull S. C. , Moore J. R.
Published: August 2006

The majority of realignment schemes undertaken in the UK to date have involved breached realignment. However, banked realignment schemes can offer benefits in terms of creating habitats that have greater physical and biological connectivity with the wider estuary. These benefits are illustrated through a case study of a scheme at Welwick in the Humber Estuary, which is one of the few recent managed realignment schemes to involve the wholesale removal of the fronting flood embankment rather than the creation of breaches. In this example, the scheme design was heavily influenced by the requirement to create a compensatory mudflat habitat and, in this regard, the methods used to assess the future evolution of the scheme are described. The paper goes on to discuss the generic design issues relevant to managed realignment schemes at other locations, including the target habitat to be created. It is suggested that the benefits of banked realignment schemes, in terms of delivering more sustainable estuary morphologies, merit increasing consideration by developers in the future.
Soil Biodegradation of Propylene Glycol Based Aircraft Deicing Fluids
Authors: Bausmith David S. , Neufeld Ronald D.
Published: August 2006

The discharge of untreated aircraft deicing fluid (ADF) wastes to surface water and stormwater collection systems is largely prohibited in the U.S., and many airports are searching for alternative methods for managing ADF wastes. A series of soil pan studies were conducted to examine soil biodegradation as a treatment for managing ADF wastes on site. The soil pan studies were designed to evaluate system operating conditions and surface application rates required to enhance biotreatment kinetics and propylene glycol removal. Results indicate that biodegradation of propylene glycol in soil followed first‐order kinetics. Soil aeration, lime amendment, and sludge amendment increased the “base level” first‐order loss coefficient by as much as a factor of 4. Degradation of propylene glycol to practical quantitation levels (10 to 17 mg/kg soil; dry weight basis) was observed in soils receiving ADF solutions of 5, 10, and 20% by weight at corresponding initial propylene glycol concentrations of 7016, 14 032, and 28 064 mg/kg. Biodegradation was severely inhibited when a 40% by weight ADF solution was applied to the soil. A reduced lag phase and increased rate of propylene glycol degradation occurred when ADF solutions in the range of 5 to 10% by weight were reapplied to soils.
Activated‐Sludge Yield Reduction Using Chemical Uncouplers
Authors: Strand Stuart E. , Harem Greg N. , Stensel H. David
Published: August 2006

To determine whether chemical additions can be used to reduce sludge production in biological wastewater treatment, uncouplers of respiratory adenosine triphosphate production were added to activated‐sludge cultures. Effects of 12 uncoupling chemicals on cell yields in batch cultures were compared. The most effective of these chemicals, 2,4,5‐trichlorophenol (TCP), was tested in a continuous‐flow, bench‐scale, completely mixed activated‐sludge system treating simulated municipal wastewater. Initially, TCP addition reduced average yield by approximately 50%. After 80 days, sludge yield increased as TCP levels in the reactor decreased. Specific oxygen use rates were good indicators of sludge yields, increasing from 8 g O2/g volatile suspended solids (VSS)·d without TCP addition to approximately 20 g O2/g VSS·d, when sludge yield was lowest. These results suggest that addition of chemical uncouplers to biological wastewater treatment systems can significantly reduce sludge production, but long‐term bioacclimation can eventually negate the effects of uncoupler addition.
Retention of Sulfate‐Reducing Bacteria in Expanded Granular‐Sludge‐Blanket Reactors
Authors: De Smul Andy , Verstraete Willy
Published: August 2006

In acetate‐fed, expanded granular‐sludge‐blanket reactors with a liquid upflow velocity between 3.5 and 4.5 m/h and pH 8.0 to 8.5, calcium‐containing tap water tended to select for sulfate‐reducing bacteria, whereas demineralized tap water promoted methane production. In a formate‐fed, sulfate‐reducing, expanded granular‐sludge‐blanket reactor operated at pH 8.25 to 8.65, maximum sulfate removal rate was 9.5 g sulfur/L·d at the slowest liquid upflow velocity tested (3.0 m/h). The latter was only possible if methane‐producing bacteria were repressed by two consecutive doses of 3.85 g/L 2‐bromo‐ethane sulfonate. These laboratory‐scale experiments confirm the presumed limited capacity of sulfate‐reducing bacteria to multiply to high biomass densities in upflow reactor systems.
Food Chain Organisms in Hypersaline, Industrial Evaporation Ponds
Authors: Tanner René , Glenn Edward P. , Moore David
Published: August 2006

Evaporation ponds are becoming widely used by industry and agriculture for the disposal of brines as a result of increasingly strict regulations pertaining to off‐site disposal methods. Migratory waterfowl and other wildlife can become reliant on such ponds, which can present biological hazards depending on the chemicals they receive. This study examined the algae, invertebrates, and chemistry of two large, hypersaline, industrial wastewater ponds near Phoenix, Arizona, at which waterfowl die‐offs (primarily eared grebes, Podiceps nigricollis) were reported. The objectives were to determine what attracted birds to the ponds and whether the ponds were directly responsible for bird deaths. High levels of total salts and nitrate were detected in both ponds, but selenium (16 to 41 μg/L) was the only potentially toxic element that reached levels of concern in the water column. Dominant algae were diatoms, Chaetoceros sp. and Nitzschia frustrulum (Kurtz.) Grun. (up to 6.5 × 105 cells/mL), and cyanobacteria. Synechococcus Nageli 1849 (up to 8.8 × 106 cells/mL). These are normal components of hypersaline ponds and natural salt lakes. However, Chaetoceros levels were negatively correlated with salinity levels in the ponds and a species turnover is expected as ponds age. Primary aquatic fauna were Artemia franciscana (brine shrimp), a filter feeder that consumes algae, and Trichocorixa sp. (waterboatman), a carnivorous insect that presumably feeds on brine shrimp. Brine shrimp were the primary attractant of birds; they were harvested by numerous resident and migratory waterfowl. Selenium levels in brine shrimp (2 to 10 mg/kg) were above recommended levels for food chain organisms in aquatic ecosystems but were well below levels that can cause acute toxicity. Brine shrimp fed to zebra danios fish (Brachydanio refio) in a bioassay were nontoxic. As at other locations where grebe mortality events have been reported in recent years, the cause of death of birds visiting these evaporation ponds is unknown. Therefore, it is concluded that these ponds may not be directly toxic to visiting wildlife, but that evaporation ponds such as these are attractants for wildlife and may pose a long‐term hazard through the accumulation of selenium in the food chain. Zero‐discharge evaporation ponds may be useful as an interim solution to the brine disposal problem but do not represent a safe, permanent solution.
Benthic Ecosystem Changes Associated with Wastewater Treatment at Marseille: Implications for the Protection and Restoration of the Mediterranean Coastal Shelf Ecosystems
Authors: Bellan Gérard , Bourcier Michel , Salen‐Picard Chantal , Arnoux André , Casserley Stella
Published: August 2006

Since 1965, macrobenthic communities have been studied in the area surrounding the sewer outfall of Marseille, France. The polluted zone increased by a factor of 3 and the subnormal zone increased by a factor of 10 between 1970 and 1980. After construction of a primary treatment plant in 1987, the macrobenthos of the polluted zone decreased significantly in terms of number of individuals. This decrease was apparently caused by a reduction of organic matter discharged to the sea and was particularly notable near the discharge. However, composition of communities began to change in 1992 to 1993. Benthic samples taken at depths of 35, 39, and 51 m in July 1994 and January 1995 indicated a recovery of parts of a polluted zone to a community resembling the subnormal zone. Most notable is the disappearance of species indicative of the polluted zone at stations H3 and H4 and the decrease at station I7 (nearest the outfall). Also, sentinel species of the subnormal zone and species characteristic of the unpolluted zone increased in number. The study demonstrated a complete change of communities at stations I7 and H4 between 1990 and 1994. Communities at these two stations, both near the sewer outfall, are characteristic of the subnormal zone. The community at station H3 that belonged to the subnormal zone displayed a degree of structural stability. These changes in benthic populations indicated that construction of the primary treatment plant reduced contamination in the area and may lead to recovery of the benthos in this region.
Granular Activated Carbon and Biological Activated Carbon Treatment of Dissolved and Sorbed Polychlorinated Biphenyls
Authors: Ghosh Upal , Weber A. Scott , Jensen James N. , Smith John R.
Published: August 2006

The most widely practiced treatment method for polychlorinated biphenyls (PCBs) in aqueous wastes is activated carbon adsorption. However, the presence of particulates in aqueous wastes may affect treatment processes primarily designed to treat dissolved PCBs because PCBs tend to partition strongly to solid surfaces. In this research, bench‐scale studies were conducted to investigate the performance of granular activated carbon (GAC) and biological activated carbon (BAC) processes for treating aqueous wastes containing dissolved and sorbed PCBs. When all influent PCBs were dissolved, influent PCBs of approximately 175 μg/L were removed to approximately 0.2 μg/L in the BAC column, compared to approximately 0.8 μg/L in the GAC column. A reduction in the extent of PCB removal was observed for both GAC and BAC processes when 10 mg/L of 0.5μm polystyrene particles were added to the influent. In the presence of influent particulates, PCB removal was significantly better in the BAC column and equaled 99% compared to 62% in the GAC column. Performance differences between the GAC and BAC columns were attributed to higher particulate capture efficiency of the biological film covering the activated carbon in the BAC column. Biological activated carbon columns thus seem to offer advantages to conventional GAC processes for aqueous wastes containing either dissolved or sorbed PCBs.
Emission of Reduced Malodorous Sulfur Gases from Wastewater Treatment Plants
Authors: Devai Istvan , DeLaune Ronald D.
Published: August 2006

The emission of malodorous gaseous compounds from wastewater collection and treatment facilities is a growing maintenance and environmental problem. Numerous gaseous compounds with low odor detection thresholds are emitted from these facilities. Sulfur‐bearing gases represent compounds with the lowest odor detection threshold. Using solid adsorbent preconcentration and gas chromatographic methods, the quantity and composition of reduced malodorous sulfur gases emitted from various steps of the treatment process were determined in wastewater treatment plants in Baton Rouge, Louisiana. Hydrogen sulfide, which is a malodorous, corrosive, and potentially toxic gas, was the most dominant volatile reduced sulfur (S) compound measured (concentration range: 0.017 to 446.9 μg S/L). Concentrations were not only more than the odor detection threshold of hydrogen sulfide, but above levels that may affect health during long‐term exposure. The concentrations of methanethiol (0.008 to 8.7 μg S/L), dimethyl sulfide (0.003 8 to 26.4 μg S/L), carbon disulfide (0.006 to 3.70 μg S/L), and carbonyl sulfide (0.005 to 7.30 μg S/L) were significantly less than hydrogen sulfide. However, even though emissions of reduced sulfur gases other than hydrogen sulfide were low, previous studies suggested that long‐term exposure to such levels may cause respiratory problems and other symptoms.
Characterization and Treatment of Runoff from Highways in the Netherlands Paved with Impervious and Pervious Asphalt
Authors: Berbee Rob , Rijs Gerard , de Brouwer René , van Velzen Load
Published: August 2006

This paper presents the results of a study to assess the effects of impervious and pervious (or porous) asphalt on the quality of runoff from highways in the Netherlands. Furthermore, the effects of settling and filtration on the quality of runoff of both types of asphalt have been elaborated. This study has been performed to support decisionmaking on how to deal with polluted runoff from highways in the Netherlands. The results show that runoff from well‐maintained pervious asphalt contains a relatively low concentration of pollutants such as heavy metals, mineral oil, polynuclear aromatic hydrocarbons, and suspended solids compared to runoff from impervious asphalt. In runoff from both types of asphalt, copper, lead, and zinc are the prevailing heavy metals. The impression exists that especially the hard shoulders along highways provided with pervious asphalt act as a sink for suspended solids, soil particles, and other pollutants. To maintain its permeability and filter action, the hard shoulders should be regularly cleaned. Water treatment tests in the laboratory revealed that treatment of runoff from pervious asphalt results in lower efficiencies in the removal of heavy metals, compared with the treatment of runoff from impervious asphalt. This is probably because of the lower concentration of suspended solids and the difference in partitioning of the metals in the soluble and particle‐bound phase. However, despite encouraging findings, long‐term research on the continued permeability of pervious asphalt is lacking. As a result, its long‐term performance with and without aggressive maintenance cannot be predicted at this time. The results of this study show that the current switch from impervious to pervious asphalt on Dutch highways has certain environmental benefits. The combination of low concentrations of pollutants, poor treatment efficiencies, and high costs makes it questionable whether additional treatment of runoff from pervious asphalt by means of settling basins or sand filtration is meaningful. Despite other positive properties of pervious asphalt such as noise abatement and less spray and skid resistance during wet weather, the rather moderate behavior of pervious asphalt with respect to slipperiness in winter should always remain an important point of attention when choosing this type of pavement.
Effects of adsorbed natural organic matter on the erosion of kaolinite sediments
Authors: Dennett Keith E. , Sturm Terry W. , Amirtharajah Appiah , Mahmood Talat
Published: August 2006

The erosion of kaolinite sediments with various concentrations of adsorbed natural aquatic organic matter was studied. Experiments were conducted in a recirculating flume under uniform flow conditions. The erosion rates were generally lower at the lowest and highest concentrations of adsorbed natural organic matter (NOM) tested. The erosion rates for the intermediate concentrations of adsorbed NOM were slightly higher. As the concentration of adsorbed NOM increased, the water content of the sediment decreased dramatically. This was probably the result of the reorientation of the sediment particles from mostly edge‐to‐face associations at lower NOM concentrations to mostly face‐to‐face associations at higher NOM concentrations. The erosion rates increased linearly as bed shear stress increased for all concentrations of adsorbed NOM. The critical shear stress generally decreased as the concentration of adsorbed NOM increased. This result is significant because sediments with higher concentrations of organic matter may be more reactive with environmental contaminants and may also be more susceptible to erosion.
A new approach for estimating volatile organic compound emissions from sewers: methodology and associated errors
Authors: Olson David A. , Varma Sunil , Corsi Richard L.
Published: August 2006

Previous studies have indicated the potential for emissions of volatile organic compounds (VOCs) from industrial and municipal sewers. However, existing estimation methods can significantly overestimate emissions of VOCs over a wide range of sewer operating conditions. This paper reviews three methods for estimating emissions from sewer reaches: equilibrium, open trench, and cocurrent ventilation. A new methodology is presented that combines both equilibrium and open‐trench approaches. The maximum error associated with this combined model is shown mathematically to be 58% and independent of flow and reach characteristics.
An evaluation of geotextiles for temporary sediment control
Authors: Barrett Michael E. , Malina Joseph F. , Charbeneau Randall J.
Published: August 2006

The performance of geotextiles for sediment control was evaluated in the field and laboratory. Runoff samples collected in the field indicated that essentially no sediment removal was attributable to filtration by the fabric. Silt fences also had little influence on the turbidity of the discharged runoff. Total suspended solids removals of 68 to 90% were found in flume tests in which silt fences were installed. The removal efficiency was correlated with the average detention time of the impounded runoff behind the fence. Flow rates through the fences under field conditions were two orders of magnitude less than would be calculated using standard ASTM index characteristics of the fabrics. This discrepancy resulted from clogging of the fabric with sediment and from the turbulent flow through the fabric openings at the hydraulic heads on the fabrics when used as silt fences.
Oxygen‐transfer efficiency of fine‐pore diffused aeration systems: energy intensity as a unifying evaluation parameter
Authors: Newbry Brooks W.
Published: August 2006

Assessing the clean‐water oxygen‐transfer characteristics of aeration devices is a critical step in the design and operation of aeration systems for activated‐sludge processes. A fundamental model has been developed for assessing the clean‐water oxygen‐transfer characteristics of fine‐bubble (fine‐pore) aeration devices. This model is based on a proposed fundamental parameter, energy intensity (EI; kW/m3), which is the energy required to deliver air to the aerated volume per unit of aerated volume. The standard oxygen transfer rate (SOTR, g/m3 · s) is shown to be related to EI through a second‐degree equation: SOTR = −11.5 EI2 + 2.27 EI (r2 = 0.951). The model applies over a wide range of diffuser types, diffuser densities, tank dimensions, and specific air flows. The results suggest that opportunities for increasing oxygen‐transfer efficiencies of fine‐bubble aeration systems remain, particularly by reducing mean bubble sizes and reducing EI requirements.
Composting of polycyclic aromatic hydrocarbons in simulated municipal solid waste
Authors: Joyce Jerome F. , Sato Chikashi , Cardenas Raul , Surampalli Rao Y.
Published: August 2006

A laboratory‐scale, batch‐type, in‐vessel composter was charged with simulated municipal solid waste deliberately contaminated with a mixture of 3‐ and 4‐ringed polycyclic aromatic hydrocarbons. The extent of their biodegradation was monitored over a 2‐month period (30 days of active composting and 30 days of compost curing) by use of soxhlet extraction and gas chromatography analysis. The results indicated that most of biodegradation occurred in the active composting phase and very little occurred during the curing phase of the composting process. Fluorene was too volatile for this type of bioremediation, and benz[a]anthracene was persistent in the compost throughout both phases of the experiment. Anthracene, phenanthrene, and pyrene showed excellent reduction in the actively composting phase, in contrast to their mercuric chloride–poisoned controls, indicating that biodegradation (not abiotic mechanisms) was the removal process from the composting mass.
Effect of operating conditions on biological phosphorus removal
Authors: Stephens Heather L. , Stensel H. David
Published: August 2006

Biological phosphorus‐removal processes incorporate a sequence of anaerobic and aerobic contact tanks to select for phosphorus‐storing bacteria and provide them with necessary substrates. Acetate consumption and phosphorus release during anaerobic contacting is followed by phosphorus uptake and storage during aerobic contacting. Bench‐scale studies were conducted in this research to examine the transient effects of longer anaerobic contact time, longer aerobic contact time, and decreased influent chemical oxygen demand (COD) feed concentration on phosphorus release, phosphorus uptake rate, and net phosphorus removal in a sequencing batch reactor (SBR) system enriched for biological phosphorus removal. Batch tests were also performed with sludge from a continuous‐flow anaerobic–anoxic–aerobic biological phosphorus‐removal system to determine the effect of increased anaerobic contact time on phosphorus release and uptake. Both systems were fed a complex synthetic feed, but the SBR system was fed only acetate as its carbon source during the transient effects study. During steady‐state operation of the SBR, the ratio of acetate COD consumed to phosphorus removed averaged 16.5:1, and the molar ratio of acetate used to phosphorus released in the anaerobic period was 0.75:1. In all cases when anaerobic contacting occurred without acetate consumption, phosphorus release rates were lower than normal. Only 40 to 60% of the phosphorus released under acetate‐deficient conditions was taken up under subsequent aeration. Transient effects of longer aeration time and lower influent feed acetate concentration in the SBR experiments resulted in lower phosphorus release and a significant decrease in phosphorus‐removal efficiency in the SBR cycle following the transient change.