Suitability of shredded tires for use in landfill leachate collection systems

The suitability of shredded tires or "tire chips" for use in the leachate collection drainage layer of a municipal solid waste landfill was investigated in terms of the: (1) compressibility of the tire chips and resulting changes in hydraulic conductivity under varying applied loads, and (2) effect of leachate pH on the shredded tries compressibility and hydraulic conductivity behavior. A constant head hydraulic conductivity apparatus was fabricated to measure the hydraulic conductivity of the tire shred sample under different axial strains. Further, the fabricated assembly was capable of measuring hydraulic conductivity of the sample at various sample locations at a given strain level. One aim of this study was to provide supporting information for permission to use tire chips as an alternative to crushed stone in the leachate collection system of a landfill. Shredded tires from two different sources were used in this study to investigate any differences in the sensitivity of the shredding process to compressibility and hydraulic conductivity responses under varied applied loads. Under applied vertical loads resulting in average vertical stresses of up to 440 kPa, equivalent to over 50 m of waste, the maximum normal strain recorded in each type of tire chip was observed to plateau at a strain level near or slightly greater than 0.5. The results of the permeability testing indicated average hydraulic conductivity values ranging between 0.67 and 13.4 cm/s under average applied normal stresses ranging from approximately 60 to 335 kPa and strain increments between 0.3 and 0.5. These results are one to three orders of magnitude higher than the hydraulic conductivity typically specified for drainage layers in leachate collection systems of 0.01 cm/s. Additional tests were also carried out to identify how landfill leachate and varied pH levels may affect the compressibility and hydraulic conductivity of the shredded tires. Care should be exercised in extending these results to field conditions, as the results presented are based on limited experimental testing data and a limited time frame.     

Can We Manage for Resilience? The Integration of Resilience Thinking into Natural Resource Management in the United States

The concept of resilience is now frequently invoked by natural resource agencies in the US. This reflects growing trends within ecology, conservation biology, and other disciplines acknowledging that social–ecological systems require management approaches recognizing their complexity. In this paper, we examine the concept of resilience and the manner in which some legal and regulatory frameworks governing federal natural resource agencies have difficulty accommodating it. We then use the U.S. Forest Service’s employment of resilience as an illustration of the challenges ahead.     

Soft subgrades’ stabilization by using various fly ashes

This publication presents the results of research involving different types of self-cementing fly ashes (without any other activators) for the stabilization of four different types of soft subgrades from various road sites in Wisconsin, USA. The strength approaches were applied to estimate the optimum mixture design and to determine the thickness of the stabilized layer. The stabilized soil samples were prepared by mixing fly ash at different contents at varying water contents. The performance of fly ash stabilized subbase depends both on the specific source of fly ash and the engineering properties of soils. It is suggested that the performance analysis of fly ash should be based upon the laboratory tests such as index properties, compaction, unconfined compressive strength and CBR tests of a specific site. This is suggested rather than using the study of the physical properties and chemical composition of fly ash and soil. As disclosed in the literature, the strength gain due to stabilization depends mainly upon three factors; ash content, molding water content and compaction delay. The samples were subjected to unconfined compression strength and California bearing ratio (CBR) tests after 7 days curing time to develop water content–strength relationship. To evaluate the impact of compaction delay that commonly occurs in the field during construction, the sets of samples were compacted 2 h later after mixing with water. The unconfined compression strength and CBR tests were performed and used to determine the thickness of the stabilized layer in pavement design. All of these factors were taken into account throughout this research.     

Parameter fitting in dynamic models

We consider the numerical approaches for the least squares estimation of the parameter vector p in the initial value problem y′ = g(t, y, p), y(t₀) = y₀(p) when observations are available on some or all components of the vector y(t). Special attention is paid to the development of techniques which, although not global, are less sensitive to initial parameter estimates than the standard approach employing the sensitivity equations. Experience indicates that interactive approaches can be very valuable when good starting parameter approximations are unavailable. We describe the main features of our interactive parameter fitting package PARFIT. This package contains standard techniques employing the sensitivity equations as well as special algorithms designed to improve poor parameter estimates. These special algorithms have been selected and developed with user interaction in mind. We describe in detail one special approach designed for the case when observations are not available on all state variables. An example (using computer generated observations) is presented to illustrate this approach. Finally, the power of an interactive approach is demonstrated with two examples involving attempts to model physically observed phenomena.     

Linking biophysical models and public preferences for ecosystem service assessments: a case study for the Southern Rocky Mountains

Through extensive research, ecosystem services have been mapped using both survey-based and biophysical approaches, but comparative mapping of public values and those quantified using models has been lacking. In this paper, we mapped hot and cold spots for perceived and modeled ecosystem services by synthesizing results from a social-values mapping study of residents living near the Pike–San Isabel National Forest (PSI), located in the Southern Rocky Mountains, with corresponding biophysically modeled ecosystem services. Social-value maps for the PSI were developed using the Social Values for Ecosystem Services tool, providing statistically modeled continuous value surfaces for 12 value types, including aesthetic, biodiversity, and life-sustaining values. Biophysically modeled maps of carbon sequestration and storage, scenic viewsheds, sediment regulation, and water yield were generated using the Artificial Intelligence for Ecosystem Services tool. Hotspots for both perceived and modeled services were disproportionately located within the PSI’s wilderness areas. Additionally, we used regression analysis to evaluate spatial relationships between perceived biodiversity and cultural ecosystem services and corresponding biophysical model outputs. Our goal was to determine whether publicly valued locations for aesthetic, biodiversity, and life-sustaining values relate meaningfully to results from corresponding biophysical ecosystem service models. We found weak relationships between perceived and biophysically modeled services, indicating that public perception of ecosystem service provisioning regions is limited. We believe that biophysical and social approaches to ecosystem service mapping can serve as methodological complements that can advance ecosystem services-based resource management, benefitting resource managers by showing potential locations of synergy or conflict between areas supplying ecosystem services and those valued by the public.     

The Chattanooga School Children Study: Effects of Community Exposure to Nitrogen Dioxide

Elementary schools in four areas of Greater Chattanooga were selected for a study of the effects of community exposure to nitrogen dioxide. One area, in close proximity to a large TNT plant, had high NO₂ exposure, another had relatively high suspended particulate exposure, and two areas served as “clean” controls. The similarity of the economic levels of the High-NO₂ and Control areas and the moderately lower economic level of the High-Particulate area were documented. Pollutant concentrations for NO₂ gas, suspended nitrates and sulfates, total suspended particulates, and soiling index were measured at stations located within the study areas. Ventilatory performance of second-grade school children in the High-NO₂ exposure area was significantly lower than the performance of children in the Control areas. The data suggested that ventilatory performance was adversely affected only when an NO₂ threshold was exceeded but that above this threshold no further impairment of performance could be detected.     

Comparison of LLW Disposal Facilities at Major Department of Energy Sites

Near surface disposal facility design and management are examined and compared using a systems approach that defines facility performance as a function of three components (or subsystems): the disposal facility design (cover systems and bottom liners); the properties of the waste (waste composition, waste form and waste package); and the site‐specific environmental features (climate, geology, and hydrology). We report an evaluation of five DOE near surface disposal facility case studies, selected to provide a “representative” sample that included disposal sites with a range of waste and environmental characteristics across the DOE. The facilities selected were the Savannah River E‐Area Engineered Trenches, Hanford Integrated Disposal Facility, Idaho Radioactive Waste Management Complex, Oak Ridge Environmental Management Waste Management Facility, and Nevada National Security Site Area 5. ©2015 Wiley Periodicals, Inc.     

Correct prenatal diagnosis of a hurler fetus where amniotic fluid cell cultures were of maternal origin

Contamination of amniotic fluid cell cultures by maternal cells can be expected to lead to misdiagnosis of fetal genotype in 0·1 to 0·5/100 cultures, when assays are carried out directly on cultured cells. Chemical analysis of the cell-free amniotic fluid supernatant may overcome this source of error and has the added advantages of speed and independence from amniotic cell culture failure. We describe a pregnancy at risk for Hurler's disease where amniotic cells cultured at amniocentesis had a female karyotype and an α-iduronidase activity towards both phenyl and 4-methylumbelliferyl substrates at the lower end of the normal range, suggesting a heterozygous fetus. An affected fetus was predicted, however, because of a high concentration of dermatan sulphate in the amniotic fluid. The discrepancy between these findings was shown to be due to maternal cell contamination of amniotic fluid cell cultures by the birth of a male infant with Hurler's disease.     

Hydrocarbons in Sand Crabs (Emeritaanaloga) from Southern California (U.S.A.)

$\text{Emerita}$$\text{analoga}$ (Crustacea:Hippidae) from three southern California (U.S.A.) beaches contained 0.9 to 24.1 μg/g dry wt saturated hydrocarbons, and 3.6 to 21.4 μg/g dry wt unsaturated hydrocarbons. Major constituents were (in wt. % total): n-alkanes (13.1%), heneicosapentaene plus heneicosahexaene (1.0%), squalene (5.1%), and unidentified polyenes (7.8%). Crabs from beaches exposed to small boat traffic and natural oil seepage were slightly and severely tainted, respectively, with petroleum hydrocarbons. Animals from San Nicolas Island (85 km offshore) contained only biogenic compounds.