Fluvial Geochemistry through a Short-Duration, Tropical-Cyclone Induced Discharge event in the Burdekin River and Hann Creek, North Queensland, Australia     

Jan Alexander  Chris R. Fielding  Simon J. Wakefield  Mark T. George  Clare F. Cottnam 《Aquatic Geochemistry》2001,7(4):275-293

The chemical composition of river water integrates a number of factors such as weathering, land use, climate, vegetation cover and human activity that individually affect its chemistry. Short term variations may also be significant. The Burdekin River, NE Australia, is an example of a class of tropical streams which experiences two to four orders of magnitude variation in discharge in response to seasonal but erratic monsoonal and cyclonic rainfall. In these systems individual discharge events last for days to weeks. Given the inherent difficulty sampling these events published data on water chemistry (and thus calculated fluxes and global budgets) may tend to be biased to low flow conditions. One such discharge event in February 1996 has been investigated for its impact on the chemistry of the water. Major cations (Na, Mg, K, Ca) all decreased in concentration as the water level rose, as did the minor elements Sr, Ba and U. Some other trace elements, notably Rb, Cr, Pb and REE were enriched in the peak flow waters. The flux of all measured elements increased substantially during the seven days of the discharge event. Such short term but significant events will have a major impact on the annual fluxes of elements delivered to the oceans from the land and global discharge budgets may need to take them into account when refining databases in the future.  相似文献   

Neocratonic magmatic-sedimentary basins of post-Variscan Europe and post-Kanimblan eastern Australia generated by right-lateral transtension of Permo-Carboniferous Pangaea     

J. J. Veevers  A. Clare  H. Wopfner† 《Basin Research》1994,6(2-3):141-157

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Experimental determination of the partitioning of gallium between solid iron metal and synthetic basaltic melt: Electron and ion microprobe study     

Michael J. Drake  Horton E. Newsom  Stephen J.B. Reed  M.Clare Enright 《Geochimica et cosmochimica acta》1984,48(8):1609-1615

The distribution of Ga between solid Fe metal and synthetic basaltic melt has been investigated experimentally at two temperatures over a limited range of oxygen fugacities. Reversal experiments were conducted, indicating a close approach to equilibrium. Analysis of run products was performed using an electron and an ion microprobe. At 1 bar total pressure, the solid metal/silicate melt partition coefficient. D(Ga), is given by: 1190°C: logD(Ga) = ?0.92 logfO₂ ? 11.91330°C: logD(Ga) = ?0.77 logfO₂ ? 8.8. For the common assumption of a valence state for Ga of 3 in silicates and assuming ideal solution of Ga in both phases, a slope of ?0.75 is predicted. The slope obtained at 1300°C (?0.77) is indistinguishable from this value, while the slope at 1190°C (?0.92) is somewhat higher. Henry's law is obeyed over the concentration range 0.007 wt.% to 0.15 wt.% Ga in metal, a factor of 20 in concentration. These partition coefficients may be utilized to evaluate metal/silicate fractionation processes in the Earth, Moon and Eucrite Parent Body. The lunar mantle appears to be depleted in Ga by a factor of 20–40 relative to CI abundances. This depletion is consistent with extraction of Ga into a geophysically plausible lunar core if Ga was initially present at a subchondritic concentration. A similar explanation probably accounts for the depletion of Ga in the Eucrite Parent Body. The upper mantle of the Earth appears to be depleted in Ga by a factor of 4– 7 relative to CI abundances. This depletion is far smaller than would be expected as a result of core formation, but is consistent with two quite different hypotheses: (i) a small amount of solid metal and sulfur-bearing metallic liquid was retained in the mantle after core formation; or (ii) addition of a late-stage chondritic component involving 5% to 10% of the upper mantle following core formation.  相似文献   

Tracking deepwater oxygen recovery using sedimentary chironomid assemblages: Peninsula Lake revisited     

Jeziorski  Adam  Nelligan  Clare  Corrigan  Dara  Meyer-Jacob  Carsten  Paterson  Andrew M.  Smol  John P. 《Journal of Paleolimnology》2021,66(4):371-387

Journal of Paleolimnology - Peninsula Lake, Ontario, Canada, is a Precambrian Shield lake that has experienced many environmental stressors since European settlement of the watershed in the...  相似文献   

Temporal and spatial variability of biogenic particles fluxes during the JGOFS northeast Atlantic process studies at 47°N, 20°W     

Philip P. Newton  Richard S. Lampitt  Timothy D. Jickells  Penny King  Clare Boutle   《Deep Sea Research Part I: Oceanographic Research Papers》1994,41(11-12)

Particle fluxes to 3100 m depth at 45°50′N, 19°30′W were measured using time-series sediment traps during a 17 month period encompassing 1989 and 1990 JGOFS spring bloom process studies in the northeast Atlantic. There was a marked intra-annual variability in fluxes of mass, particulate inorganic carbon (PIC), particulate organic carbon (POC) and opal, appearing as two major flux events in each year. In 1989, the first flux event represented the settlement of spring bloom-type material, whereas the second, in autumn, was heavily enriched in mucopolysaccharides. In 1990, in contrast, the two flux events comprised spring bloom-type material and arrived at depth at different times relative to the 1989 events. The intra- and interannual variability evident for all three biogenic components was most notable for POC: (i) the autumn 1989 event supplied twice as much POC to 3100 m as the earlier spring bloom settlement—a quite unexpected observation—and (ii) the annual average POC flux in 1989 was 3–4 times more than in 1990. A synthesis of process study datasets with sediment trap data enables an evaluation of the coupling of deep fluxes with surface-water events. Spatial variability of the 1989 deep flux events is assessed by comparing the sediment trap data reported here with those from a second site 100 km away (Honjo and Manganini,Deep-Sea Research II,40, 587–607, 1993). The timing and magnitude of the 1989 spring bloom settlement was indistinguishable in the two datasets, indicating no spatial variability in flux between these sites. In contrast, the autumn 1989 flux event was barely recorded at the second site. Given the biogeochemical importance of this latter event to deep waters, most notable in terms of its contribution to POC flux, this observation of deep-water mesoscale flux variability indicates a significant problem in determining regional carbon budgets. Construction of basin-scale budgets is a central goal of JGOFS and for this to be achieved further studies of mesoscale variability of particle flux are essential.  相似文献   

The Shock Doctrine: The Rise of Disaster Capitalism - By Naomi Klein     

David  Nally  Karenjit  Clare  Gerry    David  Nally  E E Watson    Philippa  Williams 《The Geographical journal》2008,174(3):284-287

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Lower-crustal earthquakes caused by magma movement beneath Askja volcano on the north Iceland rift     

Heidi Soosalu  Janet Key  Robert S. White  Clare Knox  Páll Einarsson  Steinunn S. Jakobsdóttir 《Bulletin of Volcanology》2010,72(1):55-62

The lower crust of magmatically active rifts is usually too hot and ductile to allow seismicity. The Icelandic mid-Atlantic rift is characterized by high heat flow, abundant magmatism generating up to 25–30 km thick crust, and seismicity within the upper 8 km of the crust. In a 20-seismometer survey in July-August 2006 within the northern rift zone around the Askja volcano we recorded ~1700 upper-crustal earthquakes cutting off at 7–8 km depth, marking the brittle-ductile boundary. Unexpectedly, we discovered 100 small-magnitude (M_L <1.5) earthquakes, occurring in swarms mostly at 14–26 km depth within the otherwise aseismic lower crust, and beneath the completely aseismic middle crust. A repeat survey during July-August 2007 yielded more than twice as many lower-crustal events. Geodetic and gravimetric data indicate melt drainage from crustal magma chambers beneath Askja. We interpret the microearthquakes to be caused by melt moving through the crust from the magma source feeding Askja. They represent bursts of magma motion opening dykes over distances of a few meters, facilitated by the extensional setting of the active rift zone.  相似文献   

Lost in the field: ensuring student learning in the 'threatened' geography fieldtrip   总被引：1，自引：0，他引：1  

Clare Herrick 《Area》2010,42(1):108-116

As a result of its importance to the discipline's identity and epistemology, the nature of fieldwork and the fieldtrip itself have recently come under close scrutiny in the education and geographical literature. Moreover, not only is their pedagogical importance being debated, but also their future viability at a time of increasing pressure on institutions to minimise potential risk situations in the field, offer value for money to students as well as following the increasingly common and popular trend of long-haul fieldtrips. This paper therefore critically interrogates the role and use of fieldwork within geographical teaching and learning in the light of its changing and increasingly contested status within the discipline in three parts. First, it outlines and reflects upon the current debate surrounding the threat to the primacy of fieldtrips in geography at a time of ongoing upheaval in higher education. Second, through the empirical example of personal experiences teaching on second-year undergraduate urban geography fieldtrips to San Francisco in December 2007 and 2008, the paper engages with the current discussions of the pedagogical importance of fieldtrips. Third, the paper asks, to what extent teaching in 'the field' might foster the 'experiential' or 'active' learning needed to inspire the kind of 'deep learning' approaches that hold the kind of 'transformative' potential envisaged as a key goal of education more broadly. Through exploring these ideas with reference to recent and relevant experience, the paper aims to critically interrogate the role and value of fieldtrips at a time when their potential demise is being cast as a fundamental assault on geography's founding identity and pedagogical traditions. The paper concludes that despite the threats it faces, the pedagogical significance of fieldwork means that it must remain a fundamental tenet of the geographical educational experience.  相似文献   

Realtime Conferencing in GIS   总被引：1，自引：0，他引：1  

Clare Churcher  & Neville Churcher 《Transactions in GIS》1999,3(1):23-30

Most GIS applications support multi-user facilities only to the extent that many people can access the same data as if they were each the only user. For collaborative work, it is beneficial for participants to be able to browse, annotate and query the data with full awareness of each other. Groupware or Computer Supported Cooperative Work (CSCW) provides support for groups of people to participate in virtual conferences from different locations. We demonstrate the advantages to be gained by applying CSCW to GIS and describe GroupARC, an application enabling GIS data to be simultaneously browsed, queried and annotated by many participants.  相似文献   

Eutrophication and warming-driven green tides (Ulva rigida) are predicted to increase under future climate change scenarios     

Guang Gao  Anthony S. Clare  Craig Rose  Gary S. Caldwell 《Marine pollution bulletin》2017,114(1):439-447

The incidence and severity of extraordinary macroalgae blooms (green tides) are increasing. Here, climate change (ocean warming and acidification) impacts on life history and biochemical responses of a causative green tide species, Ulva rigida, were investigated under combinations of pH (7.95, 7.55, corresponding to lower and higher pCO₂), temperature (14, 18 °C) and nitrate availability (6 and 150 μmol L^? 1). The higher temperature accelerated the onset and magnitude of gamete settlement. Any two factor combination promoted germination and accelerated growth in young plants. The higher temperature increased reproduction, which increased further in combination with elevated pCO₂ or nitrate. Reproductive success was highest (64.4 ± 5.1%) when the upper limits of all three variables were combined. Biochemically, more protein and lipid but less carbohydrate were synthesized under higher temperature and nitrate conditions. These results suggest that climate change may cause more severe green tides, particularly when eutrophication cannot be effectively controlled.  相似文献