Degradation of carbon tetrachloride by iron metal: Complexation effects on the oxide surface

Dehalogenation of chlorinated aliphatic contaminants at the surface of zero-valent iron metal (Fe⁰) is mediated by the thin film of iron (hydr)oxides found on Fe⁰ under environmental conditions. To evaluate the role this oxide film plays in the reduction of chlorinated methanes, carbon tetrachloride (CCl₄) degradation by Fe⁰ was studied under the influence of various anions, ligands, and initial CCl₄ concentrations ([P]_o). Over the range of conditions examined in these batch experiments, the reaction kinetics could be characterized by surface-area-normalized rate constants that were pseudo-first order for CCl₄ disappearance (k_CCl4), and zero order for the appearance of dissolved Fe²⁺ (k_Fe²⁺). The rate of dechlorination exhibits saturation kinetics with respect to [P]_o, suggesting that CCl₄ is transformed at a limited number of reactive surface sites. Because oxidation of Fe⁰ by CCl₄ is the major corrosion reaction in these systems, k_Fe²⁺ also approaches a limiting value at high CCl₄ concentrations. The adsorption of borate strongly inhibited reduction of CCl₄, but a concomitant addition of chloride partially offset this effect by destabilizing the film. Redox active ligands (catechol and ascorbate), and those that are not redox active (EDTA and acetate), all decreased k_CCl4 (and k_Fe²⁺). Thus, it appears that the relatively strong complexation of these ligands at the oxide–electrolyte interface blocks the sites where weak interactions with the metal oxide lead to dehalogenation of chlorinated aliphatic compounds.     

Framing trans-border energy transportation: the case of Keystone XL

Increasing discussion over the safety of natural resource extraction and transportation to facilitate international energy needs has given rise to controversy over the prospect of large quantities of bitumen and crude oil flowing through trans-national pipelines. This debate, incorporating the voices of industry, government and advocacy groups, has gained traction in the news media, alternately framed as an environmental, economic, trade, human rights or public safety concern. It is possible, however, that such coverage may vary substantially with regional interests and perceptions of costs and benefits, locally or nationally. To uncover how the framing of energy transportation varies with proximity considerations, regional and national media coverage in Canada and the United States of the Keystone XL pipeline from 2010 to 2014 is analyzed. National and local papers frame the pipeline according to different considerations, as do cities near to and distant from the pipeline route.     

Trace chemical partitioning in construction and demolition debris fines: process and market implications

Construction and demolition debris (CDD) fines, a residue generated from mechanized CDD recycling, can often be beneficially reused. Concentrations of chemicals of potential concern in CDD fines should be evaluated prior to being reintroduced into the environment to assess risk and make informed decisions about appropriate reuse opportunities. The distribution of trace chemicals in CDD fines as a function of particle size was measured to evaluate if concentrations in the bulk material can be reduced by removing certain particle size ranges through screening. Chemicals of potential concern, including arsenic, lead, sulfate and polycyclic aromatic hydrocarbons (PAH), were characterized in four different size fractions (19–4.8 mm, 4.8–0.84 mm, 0.84–0.3 mm, < 0.3 mm) of CDD fine samples collected from 12 US CDD recycling facilities throughout the US. Results revealed that aluminum, arsenic and chromium concentrations were distributed evenly throughout all four size fractions. As for the remaining chemicals, most samples had lower concentrations in the 19–4.8 mm size range. In some samples and for certain chemicals, removal of the finer size fractions reduced overall concentrations in CDD fines, suggesting that additional processing may be worth further investigation.     

Development of injury risk models to guide CT evaluation in the emergency department after motor vehicle collisions

Abstract

Objective: The clinical evaluation of motor vehicle collision (MVC) victims is challenging and commonly relies on computed tomography (CT) to detect internal injuries. CT scans are financially expensive and each scan exposes the patient to additional ionizing radiation with an associated, albeit low, risk of cancer. Injury risk prediction based on regression modeling has been to be shown to be successful in estimating Injury Severity Scores (ISSs). The objective of this study was to (1) create risk models for internal injuries of occupants involved in MVCs based on CT body regions (head, neck, chest, abdomen/pelvis, cervical spine, thoracic spine, and lumbar spine) and (2) evaluate the performance of these risk prediction models to predict internal injury.

Methods: All Abbreviated Injury Scale (AIS) 2008 injury codes were classified based on which CT body region would be necessary to scan in order to make the diagnosis. Cases were identified from the NASS-CDS. The NASS-CDS data set was queried for cases of adult occupants who sought medical care and for which key crash characteristics were all present. Forward stepwise logistic regression was performed on data from 2010–2014 to create models predicting risk of internal injury for each CT body region. Injury risk for each region was grouped into 5 levels: very low (<2%), low (2–5%), medium (5–10%), high (10–20%), and very high (20%). The models were then tested using weighted data from 2015 in order to determine whether injury rates fell within the predicted risk level.

Results: The inclusion and exclusion criteria identified 5,477 cases in the NASS-CDS database. Cases from 2010–2014 were used for risk modeling (n?=?4,826). Seven internal injury risk models were created based on the CT body regions using data from 2010–2014. These models were tested against data from 2015 (n?=?651). In all CT body regions, the majority of occupants fell in the very low or low predicted injury rate groups, except for the head. On average, 57% of patients were classified as very low risk and 15% as low risk for each body region. In most cases the actual rate of injury was within the predicted injury risk range. The 95% confidence interval overlapped with predicting injury risk range in all cases.

Conclusion: This study successfully demonstrated the ability for internal injury risk models to accurately identify occupants at low risk for internal injury in individual body regions. This represents a step towards incorporating telemetry data into a clinical tool to guide physicians in the use of CT for the evaluation of MVC victims.     

Knowledge,experience and the circus: academic perspectives on the processes of communicating the environmental and health impacts of electric vehicles

The translation of research findings into public realms has important implications for alternative technologies, such as electric vehicles (EVs). Much existing science communication research focuses on the agency of different publics in processes of scientific knowledge uptake. This study uses research related to the environmental and health impacts of EVs as a case study to explore how the individual agency of academic researchers can influence communication. Challenges to communication and opportunities to enhance the agency of researchers to engage in public dialogue are identified, with a focus on academics at different stages of their careers. This paper proposes a new way of understanding how these individualised nuances impact the communication of a particular researcher’s findings. These nuances are built through the researcher’s agency; a construct of their past experiences, professional and personal relationships with other actors and previous practices of communicating to publics. Communication models have previously concentrated on the heterogeneity of other actors and publics with the huge assumption that academics work consistently, homogenously, in a neutral way to the benefit of society. EVs were chosen as an appropriate case study as they are a contemporary technology that relies on the communication of knowledge and the public understanding of this knowledge to cater for future needs. The responses elicited from the interviews highlight the individual geographies of knowledge. Hence, a reflexive understanding of their role as an individual can provide valuable insights into how a researcher may distribute knowledges more effectively in their geographies to publics     

Does the canopy mixing layer model apply to highly flexible aquatic vegetation? Insights from numerical modelling

Vegetation is a characteristic feature of shallow aquatic flows such as rivers, lakes and coastal waters. Flow through and above aquatic vegetation canopies is commonly described using a canopy mixing layer analogy which provides a canonical framework for assessing key hydraulic characteristics such as velocity profiles, large-scale coherent turbulent structures and mixing and transport processes for solutes and sediments. This theory is well developed for the case of semi-rigid terrestrial vegetation and has more recently been applied to the case of aquatic vegetation. However, aquatic vegetation often displays key differences in morphology and biomechanics to terrestrial vegetation due to the different environment it inhabits. Here we investigate the effect of plant morphology and biomechanical properties on flow–vegetation interactions through the application of a coupled LES-biomechanical model. We present results from two simulations of aquatic vegetated flows: one assuming a semi-rigid canopy and the other a highly flexible canopy and provide a comparison of the associated flow regimes. Our results show that while both cases display canopy mixing layers, there are also clear differences in the shear layer characteristics and turbulent processes between the two, suggesting that the semi-rigid approximation may not provide a complete representation of flow–vegetation interactions.     

Demonstration and evaluation of commercial and municipal equipment for urban biological decontamination

Large-scale biological contamination incidents pose unique yet significant challenges to remediation operations. Previous incidents have demonstrated the utility of readily available commercial and municipal equipment for conducting remediation tasks. Preidentification and evaluation of such equipment could reduce lag time for response initiation and enhance overall response effectiveness and efficiency. The current study aimed to identify commercial and municipal equipment that could be beneficial in wide-area biological remediation operations. Equipment were identified by market research, their utility was assessed by a group of subject matter experts, and a subset of those equipment was observed under operational conditions in a realistic urban environment. Observations and feedback from demonstration participants are presented within the article. This information is intended to support rapid decision-making following large-scale biological incidents, broaden the universe of potentially useful equipment to support the response, enhance response operations, and reduce the impact on the public.     

Comparing carbon substrates for denitrification of subsurface drainage water

Nitrate in water from tile drained corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields in the U.S. Midwest contributes to nitrate contamination of surface waters. Denitrification-based biofilters are a promising strategy for reducing nitrate concentrations, but these systems require an external carbon supply to sustain denitrification. The ability of four organic materials to serve as carbon substrates for denitrification biofilters was evaluated in this laboratory study. Wood chips, wood chips amended with soybean oil, cornstalks, and cardboard fibers were mixed with subsoil (oxidized till) and incubated anaerobically for 180 d. Periodically, 15NO3-N was added to maintain nitrate N concentrations between 10 and 100 mg L-1. All of the materials stimulated NO3-N removal and the degree of removal from highest to lowest was: cornstalks, cardboard fibers, wood chips with oil, and wood chips alone. Analysis of 15N showed that immobilization and dissimilatory nitrate reduction to ammonium accounted for <4% of NO3-N removal in all treatments, therefore denitrification was the dominant NO3-N removal process. Cardboard fibers, wood chips and oil, and wood chips alone did not support as much denitrification as cornstalks, but their rates of NO3-N removal were steady and would probably continue longer than cornstalks. The addition of soybean oil to wood chips significantly increased denitrification over wood chips alone.     

Evolution of building façade road traffic noise levels in Flanders

The evolution of daytime fa?ade noise levels by road traffic at 250 dwellings in Flanders is assessed. Three identical man-operated measurement campaigns have been conducted in the years 1996, 2001 and 2009, during fall. A practical methodology has been developed, based on short time noise measurements and context observations at these locations. The uncertainty introduced by short-term sampling has been quantified as a function of the noise level. Furthermore, a correction is proposed for measuring at a random moment during daytime. Analysis of the data showed that road traffic noise levels hardly changed globally over this period of 13 years. The distribution of changes in noise level at corresponding measurement locations is nevertheless rather wide-all improvements are equally compensated by increases in noise levels at other locations. The percentage of the dwelling fa?ades exposed to daytime noise levels above 65 dBA has increased slightly between 1996 and 2001, but seems to stagnate in 2009. In spite of the increased interest and actions of policy makers during the past decades, noise exposure caused by road traffic at dwelling fa?ades is a persistent problem.     

Seasonal and spatio-temporal distribution of faecal-indicator bacteria in Tyume River in the Eastern Cape Province, South Africa

We assessed the incidence of faecal-indicator bacteria in Tyume River over a 12-month period between August 2010 and July 2011. Total coliforms, faecal coliforms and enterococci were determined by the membrane filtration method. Total coliforms were detected in counts ranging from 2.1?×?10² to 3.4?×?10⁴?CFU/100 ml. Faecal coliform counts ranged from 1?×?10² to 1.6?×?10⁴?CFU/100 ml while enterococci counts were in the range of 3.3?×?10¹ to 5.1?×?10³?CFU/100 ml. Indicator bacteria counts increased from upstream to downstream sampling sites. Counts of indicator bacteria at all sites were significantly affected by seasonal changes. The bacteriological qualities of the river water were poor, exceeding the guideline of 200 CFU/100 ml and 33 CFU/100 ml for faecal coliforms and enterococci, respectively, for recreational water. Faecal coliform counts also exceeded the 1,000 CFU/100 ml guideline for water used in fresh produce irrigation. Microbial source tracking results showed that faecal pollution was predominantly of human origin during spring at all sampling sites. During other seasons, human faecal pollution was largely confined to midstream and downstream sampling sites. Generally, the presence of faecal-indicator bacteria in the river water samples suggests faecal pollution of this freshwater resource, raising the possibility of the presence of pathogenic microorganisms in the water and a threat to public health.