Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250°C by means of Rietveld refinement of synchrotron data

Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M₁₂(Sb,As)₄S₁₃. Measurements were performed at 25 and 250°C. For both the phases, increased Fe substitution is reflected in the increased tetrahedral ‘Cu1’–S distance (‘Cu1’ is a site of Fe substitution) and Cu2–S distances. Cu2 was refined as a split position; the Cu2–Cu2 split about the plane of the S1₂S2 triangle is about 0.56 and 0.65 Å for tetrahedrite and tennantite, respectively. Cu2–Cu2 distances in the structure cavity are 2.8–2.9 Å. Between 25 and 250°C, the lattice parameter a increased by 0.02–0.04 Å and the interatomic distances by 0.01 Å on an average. Thermal expansion coefficients of little-substituted samples are similar to those of unsubstituted samples, whereas thermal expansion appears to decrease with increasing substitution by Fe. The Cu2–Cu2 split increases at 250°C by about 0.1 Å for tetrahedrite and by more than 0.15 Å for tennantite but the cage expansion is minimal so that the Cu2–Cu2 distances in the cavity decrease with temperature. Difference Fourier maps indicate that there is little residual electron density left between the two Cu2 half-sites in tetrahedrite but this inter-site density is substantially higher in tennantite. It increases with temperature, especially in the little-substituted tennantite sample.     

Characterisation and evaluation of reference materials for black carbon analysis using elemental composition, colour, BET surface area and C NMR spectroscopy

A recent comparative exercise found that different black carbon (BC) quantification methods produced widely varying results for a set of BC reference materials that included three laboratory-produced BC-rich materials, five environmental BC matrices and four samples of non-BC organic matter. This variation was attributed to a range of physical and chemical properties of the samples that could, in various ways, result in the over- or under-detection of BC in some or all of the techniques. Here the most pertinent chemical and physical characteristics of the samples are presented, including elemental analysis, lightness measurements, BET surface area measurements and ¹³C NMR analysis. Amongst the BC-rich materials, soot and char could be distinguished from one another mainly on the basis of H/C and O/C ratios, NMR observability and BET surface area. The results indicate that the aromatic structures in the soot are more highly condensed, and this explains why some BC quantification techniques detect these two materials differently. The non-BC potentially interfering materials were shown to share properties with the BC-rich materials (high C content, low lightness values and high aromaticity) that are used for certain BC quantification methods. This may lead to overestimation of BC unless these interfering materials are removed during pre-treatment. The environmental matrices were found to have relatively high amounts of metal oxides that have the potential to catalyse or inhibit thermal and chemical reactions during BC analysis.     

Systemic vulnerabilities of the global urban-industrial network to hazards

Cities in the USA engage in action on climate change, even as the federal government remains resistant to comprehensive climate policy. While experts generally agree that local level adaptation and mitigation policies are critical to avoiding the worst climate impacts, the degree to which cities communicate climate change issues to their constituents has yet to be fully explored. In this article, we evaluate how US cities communicate climate change-related issues, problems, and policies. We use a computer-assisted approach to evaluate climate change efforts by cities by examining the full text of press releases of 82 large cities in the USA. We first identify who discusses climate change, finding that many large cities in the USA address climate change in their public communication. Second, we examine the content of these discussions. Many cities discuss weather-related concerns in conjunction with broad collaborative efforts to address global warming, while city-based policy discussions focus more on energy and transportation efforts. Third, we evaluate the local factors associated with these discussions. We find that the city’s climate vulnerability is particularly influential in shaping the level and timing of climatic communication.     

Assessing transformational change potential: the case of the Tunisian cement Nationally Appropriate Mitigation Action (NAMA)

To effectively address the root causes of carbon lock-in across developing countries, Nationally Appropriate Mitigation Actions (NAMAs) with transformational change characteristics are being supported by donors and finance mechanisms as a means to achieve ambitious nationally determined contributions (NDCs). However, there is still a scarcity of empirical studies on how transformational change policies and actions are designed and supported in practice. This article addresses such a gap in knowledge by combining theoretical insights from the multi-level perspective and transitions management literature to examine a donor-supported cement sector NAMA in Tunisia developed during 2012–2013. A narrative is constructed to analyse the adequacy of the NAMA design to promote structural shifts towards low carbon development in the cement sector. Data collection is based on semi-structured interviews and documentation gathered during field work in Tunisia 2014–2015. The study finds that the NAMA design is not likely to lead to transformational change of the cement sector, since underlying factors accounting for lock-in are not properly tackled. Although the NAMA has enabled new and promising sectoral partnerships across the cement sector, the analysis suggests that the NAMA’s transformational potential is currently limited by a number of factors not being adequately addressed. Measures are proposed to reorient the NAMA towards promoting system innovation, building on further research and experimentation with the policy entrepreneurial role of donors.

Key policy insights

• Underlying factors such as the absence of local finance institutions and the lack of reflexivity features in project design restrict the potential of the Tunisian cement NAMA to spur transformation to low carbon development.

• To tackle underlying causes of carbon lock-in and reorient policies and actions for transformational design, the promotion of feedback loops and self-contemplation needs to be based on a long-term vision, experimentation, social learning and information gathered during implementation.

• Donors need to re-think their existing modalities to better support unpredictable and highly political changes for sustainability transitions in developing countries.

     

The complex decision-making of climate-induced relocation: adaptation and loss and damage

Climate change is increasingly challenging the ability of millions of people to sustain livelihoods as the places where they live become uninhabitable. The relocation of populations as individuals, households, and communities within countries and across international borders demonstrates the complexity of climate change impacts. Looking at the literature, some researchers argue that relocation caused by climate change can be an effective strategy to adapt to localized changes, whereas others argue that the movement away from ones' homeland is more neatly captured in the climate change lexicon as ‘loss and damage’. We argue here that the relocation of people as a result of the impacts of climate change can be both adaptation and loss and damage. Drawing on examples from Alaska and Kiribati, we show that dividing this issue between the two concepts is unhelpful in resolving key issues around the types of appropriate support for these transitions to sustain and protect livelihoods and to open up possibilities for self-determined futures.

Policy Relevance

Climate-induced relocation poses a significant challenge for the populations affected as well as the government agencies tasked with providing technical assistance and funding. At present, policies and institutional frameworks have not yet been developed to accommodate these challenges, despite the urgent need to do so. When the relocation of populations can be planned, participatory, and people centred, then it can be an adaptation strategy that will protect people from the permanent loss of land and livelihoods. If these movements are decided, driven, managed, and undertaken by those affected, then there is the potential for the relocation to also be a transformative opportunity for people to respond to the impacts of climate change, and sustain their livelihoods and possibly even improve certain livelihood outcomes. However, these relocations also cause significant loss and damage. The extent of the loss and damage will partly depend on the ability to have these relocations planned and ensure that human rights protections are embedded in institutional frameworks. The article shares a series of lessons and learnings that are of policy relevance at a variety of scales.     

“There is No Program Without Farmers”: Interactive Radio for Forest Landscape Restoration in Mount Elgon Region,Uganda

Increase in ownership and use of radios and mobile phones in Uganda may present opportunities for interactive and efficient agricultural extension services. Yet the impact of interactive radio on rural development has rarely been evaluated. In a participatory project, the International Union for the Conservation of Nature together with Farm Radio International and stakeholders from local government, radio, and community-based organizations promoted the increased use of forest landscape restoration activities though interactive rural radio programs, including innovative methods to reach populations not covered by radio. An evaluation found that 98% of people who listened to most or all of the broadcasts carried out one of the practices, whereas 84% of those who had listened to only one episode had used one of the practices. Inclusion of a wide range of community stakeholders from project inception was vital for presenting the project and embedding it within local institutional contexts.     

Exploring the Benefits of Field Trips in a Food Geography Course

University students often cite field experiences as some of their most important and memorable. Yet research shows that field trips are on the decline in many colleges and universities; this shift may impact geography courses that are traditionally field based. Often cited is the problem of instructor time, increased enrollment, and concerns over liability. However, field experiences give students opportunities to develop competencies, forge community connections, and provide tangible experiences that encourage deep learning. This project employs survey data from a food geography course to understand how field experiences combined with classroom discussion help students internalize and reexamine course content.     

Determination of the Optimum Sampling Intervals in Sediment Pore Waters Using the Autocovariance Function

An approach to scaling that has found considerable utility inthe field of physical oceanography is based on theauto-covariance function (ACF). It is demonstrated to alsobe useful in determining the characteristic length scale of thedominant variance of dissolved sulfide and ferrous iron inanoxic pore waters. The method begins with the analysisof a data series in which the measurement sampling intervalis smaller than the expected length scales. A least squarespolynomial fit to the data representing a background field isthen removed from the data series making possible the analysisof the variability superimposed on the background field. Thecharacteristic length scale is then defined as the distancein which the measurements become uncorrelated. This usuallyoccurs at a significance-level or zero-crossing of the ACF.Characteristic lengths obtained for sediments from a varietyof coastal environments are not distinguishable betweensecond and third order polynomial fits with average valuesand standard deviations of, respectively, 7.0 ± 2.7 mm and6.1 ± 2.3 mm. These values are close to the typical burrowdiameter of 7.5 mm used by Aller (1978) in his bioirrigationmodel for sediment diagenesis. These results indicate thatmacrofauna dwelling in the sediment are probably responsiblefor the variability, although in the seagrass meadow rhizomesmay also play a role.     

Mapping vulnerability to multiple stressors: climate change and globalization in India

There is growing recognition in the human dimensions research community that climate change impact studies must take into account the effects of other ongoing global changes. Yet there has been no systematic methodology to study climate change vulnerability in the context of multiple stressors. Using the example of Indian agriculture, this paper presents a methodology for investigating regional vulnerability to climate change in combination with other global stressors. This method, which relies on both vulnerability mapping and local-level case studies, may be used to assess differential vulnerability for any particular sector within a nation or region, and it can serve as a basis for targeting policy interventions.