The accumulation of fallout radionuclides (FRNs) from nuclear weapons testing and nuclear accidents has been evaluated for over half a century in natural environments; however, until recently their ...distribution and abundance within glaciers have been poorly understood. Following a series of individual studies of FRNs, specifically 137Cs, 241Am and 210Pb, deposited on the surface of glaciers, we now understand that cryoconite, a material commonly found in the supraglacial environment, is a highly efficient accumulator of FRNs, both artificial and natural. However, the variability of FRN activity concentrations in cryoconite across the global cryosphere has never been assessed. This study thus aims to both synthesize current knowledge on FRNs in cryoconite and assess the controls on variability of activity concentrations. We present a global database of new and previously published data based on gamma spectrometry of cryoconite and proglacial sediments, and assess the extent to which a suite of environmental and physical factors can explain spatial variability in FRN activity concentrations in cryoconite. We show that FRNs are not only found in cryoconite on glaciers within close proximity to specific sources of radioactivity, but across the global cryosphere, and at activity concentrations up to three orders of magnitude higher than those found in soils and sediments in the surrounding environment. We also show that the organic content of cryoconite exerts a strong control on accumulation of FRNs, and that activity concentrations in cryoconite are some of the highest ever described in environmental matrices outside of nuclear exclusion zones, occasionally in excess of 10,000 Bq kg−1. These findings highlight a need for significant improvements in the understanding of the fate of legacy contaminants within glaciated catchments. Future interdisciplinary research is required on the mechanisms governing their accumulation, storage, and mobility, and their potential to create time-dependent impacts on downstream water quality and ecosystem sustainability.
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•Accumulation of fallout radionuclides is commonplace in cryoconite on glaciers around the world.•There is large inter-regional variability in fallout radionuclide activity concentrations in cryoconite.•Fallout radionuclides concentrations can be orders of magnitude higher than found in other environmental matrices.•The organic content of cryoconite plays a central role in its ability to accumulate fallout radionuclides.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The kinetics of Cu, Cd and Pb accumulation by the macroalga, Fucus ceranoides, was studied under simulated estuarine conditions. Accumulation of Cu and Pb proceeded via a pseudo-first-order reaction ...that was reversible, suggesting desorption or efflux of accumulated metal, with forward rate constants on the order of 0.1 h−1. For both metals, reaction reversibility increased and the equilibrium constant decreased with increasing salinity (from 1 to 33.5) and system response times were <10 h throughout. Accumulation of Cd proceeded via a first-order reaction that was irreversible, suggesting little desorption or efflux of metal, with rate constants that decreased with increasing salinity (from 0.023 to 0.015 h−1) and reaction half-lives ranging from approximately 30–50 h. Inorganic equilibrium speciation calculations suggest that interactions of Cu, Cd and Pb principally involve the respective free ions, but that additional ions (e.g. CdCl+) and biotic processes may also be significant.
•Accumulation of Cu, Cd and Pb by the estuarine macroalga, Fucus ceranoides, decreases along a salinity gradient.•Accumulation of Cu and Pb proceeds via a reversible pseudo-first-order reaction.•In contrast, accumulation of Cd proceeds via an irreversible first-order reaction.•Differences in reaction mechanisms are attributed to differences in the ability of metals to be internalised.
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The fractionation of platinum group elements (PGE) rhodium(III), palladium(II), and platinum(IV), has been studied after their addition in aqueous form to unfiltered river water samples (Tugela ...river, South Africa) and to mixtures of river water and seawater. The particulate fraction of PGE averaged about 70 (Rh), 50 (Pd), and 25% (Pt) of total metal and was dependent on both particle concentration and salinity. The aqueous (<0.45 µm) pool of PGE was dominated by entities of less than 0.1 µm in diameter, and for Pd and Rh hydrophobic complexes of metal, operationally defined by their retention on a C-18 column, were significant. Distribution coefficients, based on the w/w concentration of metal on particles relative to the corresponding concentration in the aqueous pool, either increased (Rh and Pd) or declined (Pt) with increasing salinity. These observations are interpreted in terms of a number of general and metal-specific mechanisms. Thus, the behavior of Pd appears to be controlled by its association with relatively small (<0.1 µm) dissolved organic ligands, a significant fraction of which is hydrophobic and is subject to salting out upon estuarine mixing. Rhodium may also be partly subject to this mechanism of removal, but kinetic considerations and results of X-ray analysis of filter-retentates suggest that adsorption of cationic hydroxychlorides and the destabilization and precipitation of hydroxy-complexes induced by the rise in pH across the estuarine gradient are more important. Unlike Pd, the binding of Pt by organic ligands is kinetically hindered. Thus, in contrast to Pd, particle–water reactivity of Pt is controlled by electrostatic interactions between the particle surface and inorganic aqueous species. The results of this study improve our understanding of and ability to predict the transport and fate of PGE in estuaries where these metals are mobilized or discharged.
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Particle sorption/de-sorption did not play a major role in metal dynamics in the water column of an estuary in Spain.
The concentrations of dissolved and suspended particulate Cd, Cu and Zn have been ...determined in water samples obtained during two axial transects of the Rio Tinto-Huelva Ria system in south-west Spain, which is severely impacted by acid mine drainage. Although the metal concentrations in both phases were elevated, dissolved metals were dominant and, in the upper estuary, constituted >99% of total metal in the water column. Dissolved metals behaved non-conservatively on each transect, with maximum concentrations in the low salinity region. There was no evidence of metal adsorption within the turbidity maximum zone, despite the high specific surface areas of resuspending particles. Measurements of electrophoretic mobility showed that the suspended particulate matter (SPM) had a positive surface charge in the salinity range 0–4, where the waters had a pH<3. Desorption experiments were carried out in which SPM from the turbidity maximum zone was resuspended in coastal seawater. The desorption of the metals was monitored for 24 h, using anodic stripping voltammetry (ASV) to detect the variation in total dissolved Cd, Cu and Zn and the species of Cu and Zn. Total dissolved Cd concentrations doubled during the incubation period, whereas the concentration of total dissolved Cu declined and that of Zn remained rather constant. The ASV-labile fraction of dissolved Cu and Zn showed an initial sharp release followed by a slower uptake. However, desorption was shown to be a minor source of dissolved metals and made little contribution to the non-conservative behaviour in the low salinity zone. The results are used to predict the effects of acid mine drainage on estuarine ecology.
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This paper provides a foreword to a special edition of
Science of the Total Environment concerned with land–ocean interaction from a UK perspective as linked to processes, functioning and ...environmental management. The volume structure is presented together with an outline of the nature of the individual papers. The areas covered are: (1) freshwater chemistry, (2) riverine sedimentology, (3) tidal river, estuarine and coastal chemistry, (4) estuarine and coastal sediments and (5) shelf-sea-ocean linkages. The foreword provides as an introductory link to the broader perspectives of contemporary UK research in this area, which comes in a conclusions paper at the end of the volume.
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The hydrochemical and physical functioning of UK river basins, estuaries and coastal waters through to the open sea are outlined in relation to British environmental research over the last ten or ...more years. An overview of a considerable body of published work is presented in the context of current findings and future research challenges. This is linked to this special issue of Science of the Total Environment ‘Land Ocean Interaction: processes, functioning and environmental management: a UK perspective’ for which this contribution provides a conclusion.
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The applicability of environmental scanning electron microscopy (ESEM; imaging of hydrated samples) and conventional high vacuum scanning electron microscopy (SEM; imaging of dried samples at high ...vacuum) for the observation of natural aquatic colloids and particles was explored and compared. Specific attention was given to the advantages and limitations of these two techniques when used to assess the sizes and morphologies of complex and heterogeneous environmental systems. The observation of specimens using SEM involved drying and coating, whereas ESEM permitted their examination in hydrated form without prior sample preparation or conductive coating. The two techniques provided significantly different micrographs of the same sample. SEM provided sharper images, lower resolution limits (10 nm or lower), but more densely packed particles, suggesting aggregation, and different morphological features than ESEM, suggesting artefacts due to drying. ESEM produced less easily visualised materials, more complex interpretation, slightly higher resolution limits (30-50 nm), but these limitations were more than compensated for by the fact that ESEM samples retained, at least to some extent, their morphological integrity. The results in this paper show that SEM and ESEM should be regarded as complementary techniques for the study of aquatic colloids and particles and that ESEM should be more widely applied to aquatic environmental systems than hitherto.
Central Asia and Xinjiang – the far north-western province of China – are of increasing international importance. The United States, having established military bases in Central Asia after September ...2001, has now become a force in what was previously predominantly a Russian sphere of influence; whilst China, Russia and Iran all continue to exert strong influence. These external, international influences have had a significant impact on local politics, with the overthrow of a long-standing regime in Kyrgyzstan, continued unrest and opposition to the current regime in Uzbekistan and the intensification of Chinese control in Xinjiang.
This book explores the effect of global and local dynamics across the region: global influences include the ‘War on Terror’ and international competition for energy resources; local dynamics include Islamic revival, Central Asian nationalism, drugs trafficking; economic development and integration. The authors argue that these multiple challenges, in fact, unite Xinjiang and Central Asia in a common struggle for identities and economic development.
This book provides a comprehensive overview of the region’s historical significance, the contemporary international forces which affect the region, and of current political, economic and cultural developments.
Colin Mackerras is Professor Emeritus at Griffith University, Australia. His main works on ethnic minorities include China's Minorities: Modernization and Integration in the Twentieth Century and China's Ethnic Minorities and Globalisation . He has written a paper on the Tibetans in contemporary China for the United Nations High Commissioner for Refugees, 2005. Michael Clarke is a Research Fellow at the Griffith Asia Institute at Griffith University, Australia. He has published numerous articles on the history and contemporary politics of Xinjiang in such journals as Asian Security, Asian Studies Review, Issues & Studies and Terrorism & Political Violence .
1: China, Xinjiang and Central Asia – ‘Glocality’ in the Year 2007 - Donald H. McMillen . 2: The ‘Centrality’ of Central Asia in World History, 1700–2007: From pivot to periphery and back again? - Michael Clarke . 3: Positioning Xinjiang in Eurasian and Chinese History: Differing Visions of the ‘Silk Road’ - James A. Millward . 4: ‘Failed States’ on the ‘Perilous Frontier’: Historical Bases of State Formation in Afghanistan and Central Asia - Geoff Watson . 5: Xinjiang and Central Asia: Interdependency – Not Integration - Ann McMillan . 6: Uyghurs in the Central Asian Republics: Past and Present - Ablet Kamalov . 7: Xinjiang and Central Asia since 1990: Views from Beijing and Washington and Sino–American Relations - Colin Mackerras . 8: Central Asia’s Domestic Stability in Official Russian Security Thinking under Yeltsin and Putin: from Hegemony to Multilateral Pragmatism - Kirill Nourzhanov . 9: ‘Glocality’, ‘Silk Roads’ and New and Little ‘Great Games’ in Xinjiang and Central Asia - Michael Clarke
'This is a worthy book that should be read by all students of international relations with an interest in Central Asia' - L.J.Newby, University of oxford, The China Journal, No. 63
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