Mobility of some potentially toxic trace elements in the coal of Guizhou, China

 The mobility of 10 potentially toxic trace elements (PTTE), As, Cd, Cr, Cu, Hg, Ni, Pb, Se, Tl, and Zn from 32 coals of the Longtan Group formed in Permian Period in Guizhou Province, China was investigated using sequential extraction procedures. The results demonstrate that PTTEs such as Hg, As, Se, Cd, Cu, and Pb have the highest mobility at surface conditions, and the average extractable fractions of them are 86%, 95%, 79%, 76%, 69%, and 69% of the total amount in coal, respectively. The elements in coal with the lowest leachability include Tl, Cr, and Ni, and the average extractable fractions of them are 30%, 20%, and 29% of the total amount in coal respectively. Zinc has an intermediate behavior, and the average leachable fraction of it accounts for 46% of the total amount in coal. The results demonstrate that mobility of PTTE in coal depends on the speciation of these elements. The elements associated with sulfates, carbonates, sulfides and some organic matter in coal show the highest extraction rates during the weathering process, while elements with silicate affinities are inert at surface conditions. Received: 29 December 1998 · Accepted: 10 November 1998     

Mobilizing research on Africa's development corridors

Across Africa, development corridors – networks of roads, railways, pipelines and ports that facilitate the movement of commodities between landlocked production areas, processing zones and global markets – are being built at an unprecedented pace. In mainstream development discourse, these mega-infrastructure projects have been framed as an effective way of creating conditions that are attractive to investors while simultaneously driving inclusive economic growth and development. Yet, recent geographic research on new development corridors has revealed certain tensions and inconsistencies in this win–win narrative, drawing attention to cases where the spatial reorganization of land that has accompanied corridor development has introduced new patterns of spatial exclusion and immobility. This article shows how approaching the study of development corridors using the new mobility paradigm – paying attention to uneven and conflicting mobilities along new corridor routes – stands to generate important empirical and theoretical insights about peoples' lived experiences with corridors, as well as about the trajectories of power enacted through corridor development. Ultimately, it is argued that applying the new mobilities paradigm in future research on development corridors may help researchers to better understand emergent forms of spatial exclusion and immobility created by new corridors.     

The roads of the Sayan Mountains: Theorizing remoteness in eastern Siberia

The Sayan crossroads is a distinct cultural and economic region in the mountains of eastern Siberia. It spans three federal units in the Russian Federation: the national republics of Tyva (Todzha kozhuun) and Buryatia (Okinskii raion), as well as Irkutsk oblast (Tofalarskoe municipality). Attempts at integration by the state during the Soviet period and afterwards have privileged the construction of roads in a variety of forms to connect these areas economically with regional centers and, in turn, the rest of the country. Yet this process has been uneven and led to divergences in the economic regimes in each of the three regions that make up the crossroads. The evolution of subsistence economies, exploitation by extractive industries, and the development of tourism as an alternative source of income all differ across the three federal subunits. In turn, these divergences within the crossroads as a region point to variation in the condition of remoteness. Remoteness is an instance of relative immobility, determined by physical geography, environment, and ethnicity. And remoteness influences the function that roads play in integrating state spaces both economically and politically. In turn, this article argues for the foregrounding of the remote in the literature on mobilities in human geography, considering what the condition of remoteness allows for and forecloses in the articulation of state power and the integration of hard-to-reach areas.     

Seasonal fluctuation of riverine navigation and accessibility in Western Amazonia: An analysis combining a cost-efficient GPS-based observation system and interviews

Accessibility and transportation possibilities are key factors influencing societal conditions and land use patterns in rural areas. Thus, information on the spatial patterns of accessibility and transportation can be of paramount importance in understanding regional differences in development, human livelihood and land use patterns. Analysing spatio-temporal transportation patterns is particularly challenging in areas where everyday transportation is based on unscheduled public transportation and a naturally controlled seasonal transportation network, such as rivers. Here, our aim is to provide information on the seasonal dynamics of riverine transportation and its effects on accessibility patterns in Peruvian Amazonia. We analysed riverine transportation speeds using a low-cost GPS-based riverboat observation system. Spatio-temporal accessibility patterns were generalised from the GPS-observations that were classified according to seasons into the high water season, intermediate season and low water season. We show that navigation along the rivers has a clear seasonal and directional (upstream/downstream) variation, which varies with different types of rivers based on channel morphology. In addition, we conducted interviews with local people to study their perceptions of the seasonal changes in navigation and the accuracy of transportation schedules. As the travel distances in Peruvian Amazonia are generally long, seasonal and directional differences have clear impacts on the overall accessibility patterns in the area and on the livelihoods of riverine inhabitants. Furthermore, the lack of clearly scheduled transportation causes considerable uncertainty about transportation options for local communities. The baseline information of the seasonal and directional variation of riverine transportation and travel speeds provided by our work is usable in further accessibility and livelihood analyses for Peruvian Amazonia, but it may also be useful in other areas relying on riverine transportation.     

Metal sorption onto soils loaded with urban particulate matter

The potential effect of urban particulate matter (PM) accumulation on metal sorption onto two contrasting soils (Chernozem and Fluvisol) was investigated in a batch sorption experiment. While the Freundlich isotherms did not indicate any effect of PM addition to the soils, the Langmuir isotherm allowed us to estimate the potential behaviour of the PM in the soil. The PM added to the Chernozem did not lead to substantial changes in sorption of Cd, Cu, Mn, Ni, Pb, and Zn. On the contrary, the presence of PM in the Fluvisol increased the number of potential sorption sites in the soil. However, the results of the approximation showed a lower affinity of Cd, Mn and Ni for the Fluvisol and a better stability and a lower bioavailability of these elements in the Chernozem. In the case of Pb and Cu, no significant changes were observed in PM-enriched soils regardless of the soil properties.     

Nuances of neighbourhood: Children’s perceptions of the space between home and school in Auckland, New Zealand

This paper examines primary school children’s experiences of travelling between home and school within three neighbourhoods. Our investigation is set in Auckland, New Zealand, where parental practices such as chauffeuring are commonplace, yet are increasingly recognised as limiting children’s physical fitness and environmental awareness. Drawing on children’s voices, writing and photographs, we investigate how children currently travel to school, how they would like to travel, and how their perspectives on neighbourhood space vary by age, socio-economic status and school location. Findings reveal that over half of the participants did not like the way they travelled to school. Most desire to travel independently within public space, but are limited in their ability to do so, given the fears and obstacles that prevail within their neighbourhoods. We contend that restricted use of public space diminishes children’s agency in inner suburbs. Our analysis reveals that children favour ‘active travel’ for many of the same reasons as health professionals and transport planners. We conclude that as long as children are seen as innocents in need of protection, they will have limited agency in travel decisions and highly contingent access to public space.     

Mobilization, redistribution and bioavailability of potentially toxic elements in Shidiya phosphorites, Southeast Jordan

Shidiya Phosphorites, Southeast Jordan, provide a typical example of natural geological materials depleted with potentially toxic elements as compared to other phosphate deposits from all over the World. Nevertheless, the environmental concern as to whether processing and fertilizer production might affect the potentially toxic element concentrations in these phosphates positively or negatively has to be avoided. In order to do so, this study was designed to provide information on the redistribution pathways of the measured toxic elements during the several processing steps, including crushing, screening, washing, flotation and drying processes. It aimed also at providing information on the redistribution pathways during the different phosphate fertilizer production steps. The bioavailability of potentially toxic elements in acidic and alkaline environments has also been assessed.     

Depicting urban boundaries from a mobility network of spatial interactions: a case study of Great Britain with geo-located Twitter data

Existing urban boundaries are usually defined by government agencies for administrative, economic, and political purposes. However, it is not clear whether the boundaries truly reflect human interactions with urban space in intra- and interregional activities. Defining urban boundaries that consider socioeconomic relationships and citizen commute patterns is important for many aspects of urban and regional planning. In this paper, we describe a method to delineate urban boundaries based upon human interactions with physical space inferred from social media. Specifically, we depicted the urban boundaries of Great Britain using a mobility network of Twitter user spatial interactions, which was inferred from over 69 million geo-located tweets. We define the non-administrative anthropographic boundaries in a hierarchical fashion based on different physical movement ranges of users derived from the collective mobility patterns of Twitter users in Great Britain. The results of strongly connected urban regions in the form of communities in the network space yield geographically cohesive, nonoverlapping urban areas, which provide a clear delineation of the non-administrative anthropographic urban boundaries of Great Britain. The method was applied to both national (Great Britain) and municipal scales (the London metropolis). While our results corresponded well with the administrative boundaries, many unexpected and interesting boundaries were identified. Importantly, as the depicted urban boundaries exhibited a strong instance of spatial proximity, we employed a gravity model to understand the distance decay effects in shaping the delineated urban boundaries. The model explains how geographical distances found in the mobility patterns affect the interaction intensity among different non-administrative anthropographic urban areas, which provides new insights into human spatial interactions with urban space.     

Spatial and social transformations in a secondary city: the role of mobility in Sekondi-Takoradi,Ghana

Abstract

Existing research on urban Ghana mainly focuses on processes occurring within the country’s major cities, thereby reproducing a trend within the social sciences to overlook the role of intermediate and secondary cities. This paper aims to address this shortcoming by exploring spatial and social transformations in Sekondi–Takoradi, one of Ghana’s secondary cities and the metropolitan area serving the region’s emerging rubber industries as well as the country’s oil and gas economy. Using qualitative interviews conducted with residents in five of the city’s neighbourhoods, and a modified version of Kaufmann’s typology of mobility, we examine migration into Sekondi–Takoradi, residential mobility within the city and the daily mobility of the city’s residents. The paper highlights how these diverse forms of mobility interact with processes taking place both within and outside Sekondi–Takoradi, most notably influencing and being influenced by livelihood strategies. It is argued that the city and its hinterlands can best be envisaged as a mobile networked whole, rather than consisting of disconnected and compartmentalized locales. The paper thus contributes to broader debates on how mobility shapes urbanization by providing new empirical data on events unfolding in Africa’s secondary cities, and extends existing research by providing a counter-narrative to literature that examines the city and its surrounding rural areas separately.     

Governing people on the move in a warming world: Framing climate change migration and the UNFCCC Task Force on Displacement

Different ways of framing the nexus between climate change and migration have been advanced in academic, advocacy and policy circles. Some understand it as a state-security issue, some take a protection (or human security) approach and yet others portray migration as an adaptation or climate risk management strategy. Yet we have little insight into how these different understandings of the ‘problem’ of climate change-related migration are beginning to shape the emergence of global governance in the climate regime. Through a focus on the UNFCCC Task Force on Displacement we argue that these different framings of climate change migration shape how actors understand the appropriate role of the TFD, including the substantive scope of its mandate; its operational priorities; the nature of its outputs and where it should be situated in the institutional architecture. We show that understanding the different framings of the nexus between climate change and migration – and how these framings are contested within the UNFCCC – can help to account for institutional development in this area of climate governance.