Retention of arsenic on hydrous ferric oxides generated by electrochemical peroxidation

Electrochemical peroxidation (ECP), an emerging remediation technology, with direct electric current applied to steel electrode and small addition of H2O2, was used to remove As(III) from contaminated aqueous solutions. Bench scale experiments were conducted to evaluate the sorption and distribution of arsenic between the soluble and solid state hydrous ferric oxides (HFO) formed as part of the ECP process. ECP was effective in removing arsenic from the aqueous solution, with >98% of the applied As(III) adsorbed on HFO. Removal was complete within 3 min of ECP treatment and apparently independent of the initial pH of the water (3.5-9.5). In the absence of H2O2 more As(III) was adsorbed by solid state iron at pH 9.5 than at 3.5 (2600 vs. 1750 microg l(-1)). Thus H2O2 was crucial to oxidize As(III) to As(V) which is more strongly retained by HFO. Removal of As was not significantly affected by the concentration of H2O2 or by current processing time. The optimal operating conditions were pH < 6.5, H2O2 concentration of 10 mg l(-1) and current process time not exceeding 3 min. X-ray diffraction (XRD), diffuse-reflectance infrared Fourier transform (DRIFT) spectroscopy and transmission electron microscopy (TEM) were applied to study the HFO deposits. The XRD data indicated the prevalence of poorly ordered Fe minerals in the suspended ECP solids with a dominance of 5 line ferrihydrite in the absence of H2O2. At pH 3.5 and with 100 mg H2O2 l(-1), akaganeite was formed, whereas an incipient hematitic phase, reflection at 0.39 nm, occurred at pH 6.5. DRIFT data indicate that both As(III) and As(V) were specifically adsorbed onto HFO at acid and neutral pH. TEM observations indicated the presence of spherical shape ferrihydrite and provided evidence for possible formation of subrounded hematite and acicular shape goethite.     

Laboratory research in management: Misconceptions and missed opportunities

Laboratory research has long been a common method of inquiry in the behavioral sciences. In recent years, however, laboratory methodologies appear to have fallen from favor with many management researchers. This paper summarizes reasons for this trend including limited external validity and appropriateness of using laboratory methodologies. Additionally, a number of situations in which laboratory research may hold considerable promise and utility are identified such as using multiple samples or multiple studies in one paper, or when sensitive topics are the focus of research. The paper concludes with the reminder that the questions asked should dictate the methodology selected, not the preferences of a reviewer or editor.     

Sparse PCA and investigation of multi-elements compositional repositories: theory and applications

The geochemistry of floodplain sediments is fundamental to monitor environmental changes and to quantify their contribution to natural and anthropic processes. A floodplain sediment composition is a vector of positive elements which sum to a fixed constant. The analysis of high-dimensional compositions requires methods that produce results involving only a small portion of the original variables. On the other hand, the analysis must take into account the additional constraints specific to compositions. With the purpose of studying these problems, a new procedure for sparse PCA is proposed on European floodplain sediment samples.     

Mitigating Climate Change in US Cities: Opportunities and obstacles

This study examines opportunities for and obstacles to the mitigation of climate change in US cities using the example of the Cities for Climate Protection (CCP) campaign sponsored by the International Council for Local Environmental Initiatives. The CCP experience suggests a number of ways in which municipal governments can control greenhouse gas (GHG) emissions but also highlights several obstacles that make it difficult for local officials to do so. First, climate change is generally framed as a global issue. The CCP experience suggests that climate change is most likely to be reframed as a local issue when the preferred policy response (controlling GHG emissions) can be linked to issues (e.g. air quality) already on the local agenda. Secondly, even when local governments recognise that they should do something to control GHG emissions, institutional barriers make it difficult for municipalities to move from political rhetoric to policy action. Finally, it is questionable whether local initiatives can make meaningful contributions to climate change mitigation in the absence of policy changes at the state and national levels. Este estudio examina oportunidades y obstaculos para la mitigación del cambio climático en las ciudades de Los Estados Unidos usando el ejemplo de "Ciudades para la Protección del Clima" (CCP), campaña patrocinada por el Consejo Intenacional para Iniciativas Ambientales Locales (ICLEI). La experiencia del CCP sugiere un numero de formas en que los gobiernos municipales pueden controlar las emisiones de gas efecto invernadero (GEI) pero tambien resalta varios obstaculos que hacen esto difícil para los funcionarios locales. Primero, el cambio climático es generalmente enmarcado como un asunto global. La experiencia del CCP sugiere que el cambio climático es mas probable que sea renmarcado como un asunto local cuando la respuesta de politica preferida (controlar emisiones de GEI) puede ser relacionada con asuntos que ya estan en la agenda local (ej. calidad del aire). Segundo, aún cuando los gobiernos locales reconozcan que ellos deben hacer algo para controlar las emisiones de GEI, las barreras institucionales hacen difícil que las municipalidades se muevan de retórica politíca a una acción política. Finalmene, es cuestionable si las iniciativas locales puedan hacer contribuciones significativas a la mitigación del cambio climático en ausencia de cambios de política en el estado y a nivel nacional.     

Challenges of Urban and Regional Carbon Management and the Scientific Response

Abstract

How urbanization unfolds in the text few decades and which urban development path we choose are potentially critical to the efforts aimed at stabilizing greenhouse gas emissions. However, our understanding of urban, as a unit or system, and its cross-scale linkages in the context of carbon management is at infancy state. In this context, this article outlines, the key challenges and introduces a new scientific initiative - Urban and Regional Carbon Management Initiative of the Global Carbon Project, which has raised key scientific questions with the aim to find reasonable answers. This article mainly showcases key science questions, past activities and future outlook with the aim to reach out to the related scientific and policy communities.     

Thermal effects on swimming activity and habitat choice in juvenile Pacific cod (Gadus macrocephalus)

The behavioral responses of fishes to temperature variation have received less attention than physiological responses, despite their direct implications for predator–prey dynamics in aquatic ecosystems. In this paper, we describe the temperature dependence of swimming performance and behavioral characteristics of juvenile Pacific cod (Gadus macrocephalus; 75–125 mm total length). Maximum swimming speeds increased with temperature and body size. Routine swimming speeds of Pacific cod in small groups of similarly sized fish (N = 6) increased with body size and were 34 % faster at 9 °C than at 2 °C. The response to temperature was opposite that previously described for juvenile walleye pollock (Theragra chalcogramma), reflecting species-specific differences in behavioral responses. In a separate experiment, we demonstrated the effect of temperature on habitat selection of juvenile Pacific cod: Use of an artificial eelgrass patch in a 5-m-long laboratory tank was significantly greater at 9 °C than at 2 °C. These results illustrate that temperature affects a range of behavioral traits that play important roles in determining the frequency and outcomes of predator–prey interactions.     

Streamwise velocity profiles in coastal currents

The ability to model marine currents can be a powerful device for many planning activities, for which the knowledge of the velocity field is of pivotal importance, such as the evaluation of current-induced loading on maritime structures or the diffusion and dispersion of polluted flow discharges. Observations of time-averaged velocity profiles, taken with a vessel mounted acoustic Doppler current profiler during a monitoring survey program in the seas of Southern Italy, are analysed in this paper. The measurements were taken under non-breaking conditions, offshore the surf zone, with the aim of reproducing the vertical trends of the streamwise velocity by means of standard theoretical laws. To evaluate also the possible influence of stratification on the current velocity profile shape, together with velocity measurements water temperature and salinity were also measured at the same time and locations, by means of a CTD recorder. The examined surveys referred to different time periods and sites, to guarantee a general validity of deductions. On the basis of the experiments, we verified the actual existence of a log-layer and concluded that the upper limit of the region in which the log law is applicable extends well beyond the inner region. Moreover, the deviations of the measured velocity from the logarithmic profiles above the height of the log layer is consistent with the effects of stratification. The parameters of the log law were estimated, depending on both flow dynamics and stratification in the target area. As a second step, in the most superficial and stratified layer, the velocity profiles were modelled by means of a power law, which fitted the measured data well. According to previous studies, the power law parameters result Reynolds number dependent by means of a new proposed formulation. Finally, the bottom stress and the bottom drag coefficient were investigated.