Influence of aquifer properties on phytoremediation effectiveness     

Matthews DW  Massmann J  Strand SE 《Ground water》2003,41(1):41-47

Recent research has shown that planting deep-rooted trees, such as poplar, can take up and degrade important ground water pollutants such as trichloroethylene (TCE) as they transpire water from the capillary fringe of shallow contaminated aquifers. The effect of hydrogeologic factors on the minimum plantation area needed to prevent downgradient migration of contaminated ground water is not well known. Accordingly, the objective of this research was to identify the hydrogeologic parameters that control phytoremediation effectiveness. We used a numerical ground water flow model to evaluate the effect that natural variations in hydrogeologic parameters and growing season duration have on the minimum plantation area required for capture. We found that the plantation area that was needed to completely capture a ground water contamination plume was directly proportional to aquifer horizontal hydraulic conductivity, saturated thickness, and ground water gradient. The plantation area needed for capture increased nonlinearly with increasing plume width, aquifer anisotropy, and decreasing growing season duration. The plantation area needed for capture was generally insensitive to aquifer-specific yield and storativity. Steady-state simulations can be used to predict the plantation area needed for capture in many applications. A particularly important finding of this work is that evapotranspiration fluxes through plantations appropriately sized to contain the plume substantially exceeded the ground water flux through the plume itself.  相似文献   

Butterfly pitch-angle distributions observed by ISEE-1     

Theodore A. Fritz  Mohamed Alothman  Jyotirmoyee BhattacharjyaDavid L. Matthews  Jiasheng Chen 《Planetary and Space Science》2003,51(3):205-219

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Meteorological monitoring of an active volcano: Implications for eruption prediction     

Jenni Barclay  Jade E. Johnstone  Adrian J. Matthews   《Journal of Volcanology and Geothermal Research》2006,150(4):241-358

Rainfall data collected on and around the Soufriere Hills Volcano, Montserrat between 1998 and 2003 were analysed to assess the impact on primary volcanic activity, defined here as pyroclastic flows, dome collapses, and explosions. Fifteen such rainfall-triggered events were identified. If greater than 20 mm of rain fell on a particular day, the probability of a dome collapse occurring on that day increased by a factor of 6.3% to 9.2%, compared to a randomly chosen day. Similarly, the probability of observing pyroclastic flows and explosions on a day with > 20 mm of rainfall increased by factors of 2.6 and 5.4, respectively. These statistically significant links increased as the rainfall threshold was increased. Seventy percent of these rainfall-induced dome collapse episodes occurred on the same calendar day (most within a few hours) as the onset of intense rainfall, but an extra 3 occurred one or two calendar days later. The state of the volcano was important, with the rainfall–volcanic activity link being strongest during periods of unstable dome growth and weakest during periods of no dome growth or after a recent major collapse.Over 50% of the heavy rain days were associated with large-scale weather systems that can potentially be forecast up to a few days ahead. However, the remaining heavy rain days were associated with small-scale, essentially unpredictable weather systems. There was significant variability in the amount of rainfall recorded by different rain gauges, reflecting topographic variations around the volcano but also the inherent small-scale variability within an individual weather system. Hence, any monitoring/warning program is recommended to use a network, rather than just a single gauge. The seasonal cycle in rainfall was pronounced, with nearly all the heavy rain days occurring in the May–December wet season. Hence, the dome was at its most vulnerable at the beginning of the wet season after a period of uninterrupted growth. Interannual variability in rainfall was related to tropical Pacific and Atlantic sea surface temperature anomalies, and holds out the prospect of some limited skill in volcanic hazard forecasts at even longer lead times.  相似文献   

Communicating academic geography—the continuing challenge     

Jon Shaw  Judith Matthews 《Area》1998,30(4):367-372

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The right to say: the development of youth councils/forums within the UK     

Hugh Matthews  Melanie Limb 《Area》1998,30(1):66-78

Summary Article 12 of the United Nations Convention on the Rights of the Child makes explicit reference to children's right to say what they think about matters relating to the quality of their lives, and to have those opinions taken into account in accordance with their levels of competence and maturity. Despite the commitment of the UK Government to this and other similar initiatives designed to empower young people, a culture of non-participation is endemic within the UK in the context of environmental planning. Young people are seemingly invisible on the landscape. This paper reviews the case for children's active involvement in their environmental future and considers attempts to engage young people through an incipient structure of youth councils and forums.  相似文献   

Modelling the dynamics and thermodynamics of volcanic degassing     

David S. Stevenson  Stephen Blake 《Bulletin of Volcanology》1998,60(4):307-317

 The rates of passive degassing from volcanoes are investigated by modelling the convective overturn of dense degassed and less dense gas-rich magmas in a vertical conduit linking a shallow degassing zone with a deep magma chamber. Laboratory experiments are used to constrain our theoretical model of the overturn rate and to elaborate on the model of this process presented by Kazahaya et al. (1994). We also introduce the effects of a CO₂–saturated deep chamber and adiabatic cooling of ascending magma. We find that overturn occurs by concentric flow of the magmas along the conduit, although the details of the flow depend on the magmas' viscosity ratio. Where convective overturn limits the supply of gas-rich magma, then the gas emission rate is proportional to the flow rate of the overturning magmas (proportional to the density difference driving convection, the conduit radius to the fourth power, and inversely proportional to the degassed magma viscosity) and the mass fraction of water that is degassed. Efficient degassing enhances the density difference but increases the magma viscosity, and this dampens convection. Two degassing volcanoes were modelled. At Stromboli, assuming a 2 km deep, 30% crystalline basaltic chamber, containing 0.5 wt.% dissolved water, the ∼700 kg s^–1 magmatic water flux can be modelled with a 4–10 m radius conduit, degassing 20–100% of the available water and all of the 1 to 4 vol.% CO₂ chamber gas. At Mount St. Helens in June 1980, assuming a 7 km deep, 39% crystalline dacitic chamber, containing 4.6 wt.% dissolved water, the ∼500 kg s^–1 magmatic water flux can be modelled with a 22–60 m radius conduit, degassing ∼2–90% of the available water and all of the 0.1 to 3 vol.% CO₂ chamber gas. The range of these results is consistent with previous models and observations. Convection driven by degassing provides a plausible mechanism for transferring volatiles from deep magma chambers to the atmosphere, and it can explain the gas fluxes measured at many persistently active volcanoes. Received: 26 September 1997 / Accepted: 11 July 1998  相似文献   

From subduction to transform motion: a seabeam survey of the Hellenic trench system     

Xavier Le Pichon  Jacques Angelier  Jean Aubouin  Nicolas Lyberis  Serge Monti  Vincent Renard  Henri Got  Ken Hsu¨  Yossi Mart  Jean Mascle  Drummond Matthews  Dimitri Mitropoulos  Pandelis Tsoflias  Georges Chronis 《Earth and Planetary Science Letters》1979,44(3):441-450

Preliminary results of a multi-narrow beam survey of the Hellenic trench system, in the Eastern Mediterranean, are presented. The southwestern Ionian branch is divided in small basins, partly filled with Pleistocene sediments. The morphology suggests that the basins are deformed by a compressional stress acting roughly perpendicularly to the trench along N50°E. This direction is the direction of the regional slip vector of the shallow thrust-type earthquakes. The structure of the southeastern Pliny-Strabo branch is quite different. Narrow en-e´chelon slots, oriented N40°E, have been mapped within the main troughs oriented N60°E. The regional earthquake slip vector is also oriented along N40°E. We conclude that the Hellenic trench system is an active subduction system, dominated by thrust along the Ionian branch and by transform motion along the Pliny-Strabo branch.  相似文献   

Quaternary sea level fluctuations on a tectonic coast: New ${}^{230}\text{Th}{}^{234}\text{U}$ dates from the Huon Peninsula,New Guinea     

A.L. Bloom  W.S. Broecker  J.M.A. Chappell  R.K. Matthews  K.J. Mesolella 《Quaternary Research》1974,4(2):185-205

Emerged coral reef terraces on the Huon Peninsula in New Guinea were reported in a reconnaissance dating study by Veeh and Chappell 1970. Age definition achieved was not good for several important terraces, and we report here a series of new ${}^{230}\text{Th}{}^{234}\text{U}$ dates, which further clarify the history of late Quaternary eustatic sea level fluctuations. More than 20 reef complexes are present, ranging well beyond 250,000 yr old: we are concerned with the seven lowest complexes. Major reef-building episodes dated by ${}^{30}\text{Th}{}^{234}\text{U}$ are reef complex I at 5–9 ka (kilo anno = 1000 yr), r.c. IIIb at 41 ka (four dates), r.c. IV at 61 ka (four dates), r.c. V at 85 ka (two dates), r.c. VI at 107 ka (two dates), and r.c. VII at 118–142 ka. Complex II was previously dated by ¹⁴C at 29 ka: this age has not yet been confirmed, and may be only a lower limit. The reef crests were built during or immediately before intervals of sea level maxima, when rates of rising sea level and tectonic uplift briefly coincided. The culmination of each reef-building episode was only a few thousand years in duration, and multiple dates from the same reef complex generally group within the statistical errors of the individual dates.Several methods can be used to estimate the altitude of each sea level maximum relative to present sea level. The least complicated is to calculate mean tectonic uplift rate for each profile of the terraces, and use the mean rate to calculate the tectonic displacement of each dated reef complex on that profile. The difference between the present altitude of a reef complex and its calculated tectonic uplift gives the paleosea level at the time the reef grew. We estimate uplift rates for six surveyed sections by calibrating against published paleosea level estimates from Barbados and elsewhere, viz 125 ka, paleosea at +6 m; 103 ka, ?15 m; 82 ka, ?13 m. For each section the individual uplift rates for reefs V, VI, and VIIb are within 5% of their section means. Using the mean rates. paleosea level estimates for reef crests II, IIIB, and IV are made for each section. Consistency of estimates between sections is good, giving ?28 m for the 60 ka paleosea level, around ?38 m for the 42 ka level and ?41 m for the 28 ka level (if the age is older the paleosea level would be lower. Using the mean uplift rates, the 82 ka and 103 ka paleosea levels are also estimated for each section: all individual estimates are plotted graphically, and a sea level curve drawn. The reef stratigraphy indicates sea level lowerings between each dated reef crest: the crests probably represent the interstadials of the Wisconsin (Würm, Weichsel) Glaciation, and intervening lower levels correspond to stadials. Since the last time of eustatic sea level higher than the present (about 125 ka), five sea level maxima occurred at roughly 20-ka intervals, none being as high as the present.  相似文献   

High-resolution imaging of the anomalous flux ratio gravitational lens system CLASS B2045+265: dark or luminous satellites?     

J. P. McKean  L. V. E. Koopmans  C. E. Flack  C. D. Fassnacht  D. Thompson  K. Matthews  R. D. Blandford  A. C. S. Readhead  B. T. Soifer 《Monthly notices of the Royal Astronomical Society》2007,378(1):109-118

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The environments and clustering properties of 2dF Galaxy Redshift Survey selected starburst galaxies     

Matt S. Owers  Chris Blake  Warrick J. Couch  Michael B. Pracy  Kenji Bekki 《Monthly notices of the Royal Astronomical Society》2007,381(2):494-510

We investigate the environments and clustering properties of starburst galaxies selected from the 2dF Galaxy Redshift Survey (2dFGRS) in order to determine which, if any, environmental factors play a role in triggering a starburst. We quantify the local environments, clustering properties and luminosity functions of our starburst galaxies and compare to random control samples. The starburst galaxies are also classified morphologically in terms of their broad Hubble type and evidence of tidal merger/interaction signatures. We find the starburst galaxies to be much less clustered on large (5–15 Mpc) scales compared to the overall 2dFGRS galaxy population. In terms of their environments, we find just over half of the starburst galaxies to reside in low to intermediate luminosity groups, and a further ∼30 per cent residing in the outskirts and infall regions of rich clusters. Their luminosity functions also differ significantly from that of the overall 2dFGRS galaxy population, with the sense of the difference being critically dependent on the way their star formation rates are measured. In terms of pin-pointing what might trigger the starburst, it would appear that factors relating to their local environment are most germane. Specifically, we find clear evidence that the presence of a near neighbour of comparable luminosity/mass within 20 kpc is likely to be important in triggering a starburst. We also find that a significant fraction (20–30 per cent) of the galaxies in our starburst samples have morphologies indicative of either an ongoing or a recent tidal interaction and/or merger. These findings notwithstanding, there remain a significant portion of starburst galaxies where such local environmental influences are not in any obvious way playing a triggering role, leading us to conclude that starbursts can also be internally driven.  相似文献