The role of vegetation in the retention of fine sediment and associated metal contaminants in London's rivers

Many urban rivers receive significant inputs of metal‐contaminated sediments from their catchments. Restoration of urban rivers often creates increased slack water areas and in‐channel vegetation growth where these metal‐contaminated sediments may accumulate. Quantifying the accumulation and retention of these sediments by in‐channel vegetation in urban rivers is of importance in terms of the planning and management of urban river restoration schemes and compliance with the Water Framework Directive. This paper investigates sediment properties at four sites across three rivers within Greater London to assess the degree to which contaminated sediments are being retained. Within paired restored and unrestored reaches at each site, four different bed sediment patch types (exposed unvegetated gravel, sand, and silt/clay (termed ‘fine’) sediments, and in‐channel vegetated sediments) were sampled and analysed for a range of metals and sediment characteristics. Many samples were found to exceed Environment Agency guidelines for copper (Cu), lead (Pb) and zinc (Zn) and Dutch Intervention Values for Cu and Zn. At all sites, sediments accumulating around in‐channel vegetation were similar in calibre and composition to exposed unvegetated fine sediments. Both bed sediment types contained high concentrations of pseudo‐total and acetic acid extractable metal concentrations, potentially due to elevated organic matter and silt/clay content, as these are important sorbtion phases for metals. This implies that the changed sediment supply and hydraulic conditions associated with river restoration may lead to enhanced retention of contaminated fine sediments, particularly around emergent plants, frequently leading to the development of submerged and emergent landforms and potential river channel adjustments. High pseudo‐total metal concentrations were also found in gravel bed sediments, probably associated with iron (Fe) and manganese (Mn) oxyhydroxides and discrete anthropogenic metal‐rich particles. These results highlight the importance of understanding the potential effects of urban river restoration upon sediment availability and channel hydraulics and consequent impacts upon sediment contaminant dynamics and storage. Copyright © 2014 John Wiley & Sons, Ltd.     

Resel filtering to aid visualisation within an exploratory data analysis system

Received: 18 July 1999 / Accepted: 30 December 1999     

Seasonal and diurnal variability of pressure fluctuation in the infrasound frequency range observed in the Czech microbarograph network

Infrasound environments in the Czech microbarograph network were studied. Reference Fourier amplitude spectra were calculated from data measured at three microbarograph sites of the network in May 2011-April 2012; directional analysis of infrasound arrivals in the frequency band 0.15-0.4 Hz was performed for the microbarograph array at Panská Ves in May 2014-April 2015. Diurnal, seasonal and site-to-site variability of the reference spectra was evaluated. Site-to-site variability is influenced by the location of the respective sensors in the open air and inside the observatory buildings and by local noise phenomena like wind turbines. Diurnal variability is well developed in summer with maximum ambient noise levels during the daytime and minima at night. Seasonal variability is observed at night with maxima in winter and minima in summer. Wind and wind eddies seem to be an important source of ambient noise in measurements in the Czech microbarograph network. A distinct spectral peak occurs near 0.2 Hz with amplitudes by about one order of magnitude higher in winter than in summer. Its seasonal variability is related to seasonal propagation of microbaroms from the source region in the Northern Atlantic.     

The evolution of polycyclic aromatic hydrocarbons under simulated inner asteroid conditions

Large polycyclic aromatic hydrocarbons (PAHs) are an important component of the interstellar medium. PAHs have been identified in the soluble and insoluble matter of carbonaceous chondrites (CCs). Here, we study the evolution of PAHs under conditions relevant to the interiors of asteroids and compare our results to PAHs observed in CCs. We have performed long‐term and short‐term hydrothermal experiments, in which we exposed PAH‐mineral mixture analogs of meteorites to temperature conditions representative of those predicted for asteroids interiors. Our results show that small PAHs with melting points within the aqueous alteration temperature of CCs form carbonaceous spherules in the presence of water. In this work, we describe the microstructure and morphology of these spherules. We discuss the similarities and differences compared to globules isolated from CCs.     

Impacts of tuna industries on coastal communities in Pacific Island countries

Tuna fishing and processing industries have brought both a range of economic development and cultural contact opportunities to coastal communities in Pacific Island countries, and a variety of social and environmental challenges. This article outlines the main trends in the tuna industries of the region, examines the aspirations of coastal communities towards these industries, and traces actual experiences of their operations.     

Past and future evolution in the Thames Estuary

In order to manage estuaries effectively, it is important to be able to predict how they are likely to change in the future, both to natural and anthropogenic forcing. This paper looks at historical morphological development of the Thames Estuary, taking into account the effect of human intervention, and uses the ASMITA morphological model to predict the long-term evolution of the estuary into the future, assuming either historic rates of sea-level rise or accelerated sea-level rise. The historical sediment budget for the Thames Estuary was examined and source and sink terms, including fluvial sediment supply and historical dredging rates, were included in the ASMITA model. ASMITA predictions showed good overall agreement with the historical data, highlighting the benefits of detailed historical review and the inclusion of anthropogenic effects in the model. Future ASMITA predictions for the period 2000 to 2100 suggest that, under both historical and accelerated sea-level rise scenarios, the estuary will experience accretion, but, for the accelerated sea-level rise scenario, accretion will be at a slower rate than sea level rise. With accelerated sea-level rise, intertidal profiles were predicted to be up to 0.5 m lower with respect to high water.     

Reflections on use of participatory research for disaster risk reduction

Participatory research approaches are increasingly popular with academic researchers and development organisations working to facilitate change in collaboration with local communities. This paper contributes to recent debates over the use of participatory approaches by examining the use of participatory research within disaster risk reduction. Drawing on research in Papua New Guinea in which participatory techniques were used with indigenous communities to determine strategies for dealing with environmental hazards, the value of such techniques is critiqued. Finally the significance of participatory research as a research methodology is discussed as is its possible contribution to disaster risk reduction policy.     

Witches, children and Kiva-the-research-dog: striking problems encountered in the field

This paper examines how power, privilege and vulnerability can surface in unexpected ways during fieldwork. Drawing from my experiences working with indigenous women and children who beg and sell on the streets of Ecuador, I suggest that researchers do not always hold as much power as we might assume. By positioning myself within stories about witches and children, I discuss how multiple research identities can shift power dynamics in unsettling and unexpected ways. In this paper, I also reflect upon a particularly unorthodox research method: using my dog as a research assistant. My dog inadvertently became instrumental in providing access to children's life stories; however, her presence also highlighted some of the dramatic incongruities between their life experiences and my own.     

Sun,sea, sand and tsunami: examining disaster vulnerability in the tourism community of Khao Lak,Thailand

The impact of the 2004 Indian Ocean tsunami on coastal tourism communities highlights the vulnerability of tourism destinations to external shocks. Based on fieldwork conducted in Thailand in the wake of this disaster, this paper addresses one fundamental question: what sociopolitical and environmental conditions contributed to the vulnerability of the affected tourism community of Khao Lak in the southern Phang Nga Province. We argue that an understanding of the root causes of destination vulnerability is vital not only for the successful implementation of regional recovery plans, but also for building long‐term resilience against future shocks. In the absence of an appropriate tourism vulnerability framework, this paper analyzes Khao Lak's vulnerability through an innovative theoretical framework comprised of the sustainability vulnerability framework, relational scale and place. The findings reveal that Khao Lak's vulnerability is shaped by 13 interlinked factors. These are the complex outcomes of social norms and developmental and dynamic governance processes driven by the competing agendas and scaled actions of key government and industry stakeholders. The identification and understanding of the drivers of Khao Lak's vulnerability and a strong vulnerability framework have significant implications for the wider tourism community. First, the empirical findings provide tourism communities with a blueprint for understanding the foundations of their vulnerability to external shocks. Second, the tourism vulnerability framework presented here provides destination communities and government stakeholders with an analytical tool through which to analyze their unique sociopolitical conditions. Together, these empirical and theoretical contributions bring us closer to securing sustainable livelihood futures for tourism dependent communities.