The effect of Al(OH)₄ on the dissolution rate of quartz     

Barry R. Bickmore  Kathryn L. Nagy  A. Riley Brinkerhoff 《Geochimica et cosmochimica acta》2006,70(2):290-305

The influence of Al(OH)₄⁻ on the dissolution rate of quartz at pH 10-13 and 59-89 °C was determined using batch experiments. Al(OH)₄⁻ at concentrations below gibbsite solubility depressed the dissolution rate by as much as 85%, and this effect was greater at lower pH and higher Al(OH)₄⁻ concentration. Dissolution rates increased with increasing temperature; however, the percent decrease in rate due to the presence of Al(OH)₄⁻ was invariant with temperature for a given H⁺ activity and Al(OH)₄⁻ concentration. These data, along with what is known about Al-Si interactions at high pH, are consistent with Al(OH)₄⁻ and Na⁺ co-adsorbing on silanol sites and passivating the surrounding quartz surface. The observed pH dependence, and lack of temperature dependence, of inferred Al(OH)₄⁻ sorption also supports the assumption that the acid-base behavior of the surface silanol groups has only a small temperature dependence in this range. A Langmuir-type adsorption model was used to express the degree of rate depression for a given in situ pH and Al(OH)₄⁻ concentration. Incorporation of the rate data in the absence of aluminate into models that assume a first-order dependence of the rate on the fraction of deprotonated silanol sites was unsuccessful. However, the data are consistent with the hypothesis proposed in the literature that two dissolution mechanisms may be operative in alkaline solutions: nucleophilic attack of water on siloxane bonds catalyzed by the presence of a deprotonated silanol group and OH⁻ attack catalyzed by the presence of a neutral silanol group. The data support the dominance of the second mechanism at higher pH and temperature.  相似文献   

Topographic relations: developing a heuristic device for conceptualising networked relations     

Rob Inkpen  Peter Collier  Mark Riley 《Area》2007,39(4):536-543

This paper considers whether the deployment of a topographical metaphor may add value to the recent discussion of networked relations. The paper discusses how viewing relations as part of a relational landscape may add a third dimension to the discussion by allowing an appreciation of the strength, or entrenchment, of relations, and how these entrenchments impact on the development of new relations and the resistance to watershed events. The heuristic device is explored through the case of air survey in the 1920s and 1930s. This illustrative case demonstrates how relations are held together, resisted and reformed to different degrees depending on the varying topography of the relational landscape.  相似文献   

Impact of hurricanes storm surges on the groundwater resources     

Thomas P. Van Biersel  Douglas A. Carlson  L. Riley Milner 《Environmental Geology》2007,53(4):813-826

Ocean surges onto coastal lowlands caused by tropical and extra tropical storms, tsunamis, and sea level rise affect all coastal lowlands and present a threat to drinking water resources of many coastal residents. In 2005, two such storms, Hurricanes Katrina and Rita struck the Gulf Coast of the US. Since September 2005, water samples have been collected from water wells impacted by the hurricanes’ storm surges along the north shore of Lake Pontchartrain in southeastern Louisiana. The private and public water wells tested were submerged by 0.6–4.5 m of surging saltwater for several hours. The wells’ casing and/or the associated plumbing were severely damaged. Water samples were collected to determine if storm surge water inundated the well casing and, if so, its effect on water quality within the shallow aquifers of the Southern Hills Aquifer System. In addition, the samples were used to determine if the impact on water quality may have long-term implication for public health. Laboratory testing for several indicator parameters (Ca/Mg, Cl/Si, chloride, boron, specific conductance and bacteria) indicates that surge water entered water wells’ casing and the screened aquifer. Analysis of the groundwater shows a decrease in the Ca/Mg ratio right after the storm and then a return toward pre-Katrina values. Chloride concentrations were elevated right after Katrina and Rita, and then decreased downward toward pre-Katrina values. From September 2005 to June 2006, the wells showed improvement in all the saltwater intrusion indicators.  相似文献   

Two samplers for large-volume collection of chlorinated hydrocarbons     

R. Dawson  J.P. Riley  R.H. Tennant 《Marine Chemistry》1976,4(1):83-88

Two sampling devices for the in situ extraction of chlorinated hydrocarbons from water are described. Both samplers use the macroreticular adsorbent Amberlite XAD-2. They include a “fish” sampler which has been used to collect samples for PCB analysis from waters around the British Isles. Operation of this sampler causes a minimum of interruption to a ship's cruise programme and at the same time allows a large area to be surveyed. The second sampler is a self-powered in situ pump which is cheap to construct and can be left unattended to extract large volumes of water at a fixed station. The device is serviced by divers and samples may be collected daily on a routine sampling basis.  相似文献   

The 7C survey of radio sources at 151 MHz: 33 regions in the range 7h < RA < 17h, 30° <Dec. <58°     

J. M. W. Riley  E. M. Waldram  J. M. Riley 《Monthly notices of the Royal Astronomical Society》1999,306(1):31-34

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Hotspot position as an orientation indicator in FR II radio sources     

G. M. Gilbert  J. M. Riley 《Monthly notices of the Royal Astronomical Society》1999,309(3):681-684

We show that for a sample of radio sources with z <0.5 from the complete LRL data set the broad-lined radio galaxies (BLRGs) have hotspots that are very much more recessed than their narrow-lined counterparts. The asymmetry in the amount by which the hotspots are recessed in the two lobes of a source is also greater in the BLRGs. Assuming the standard unified model these results indicate that the position of the hotspots in the lobes is orientation-dependent. The most plausible interpretation is that the hotspots do not always coincide with the termination point of the beam but are sometimes other, relativistically beamed, features internal to the lobes.  相似文献   

Probabilistic Solar Wind and Geomagnetic Forecasting Using an Analogue Ensemble or “Similar Day” Approach     

M. J. Owens  P. Riley  T. S. Horbury 《Solar physics》2017,292(5):69

Effective space-weather prediction and mitigation requires accurate forecasting of near-Earth solar-wind conditions. Numerical magnetohydrodynamic models of the solar wind, driven by remote solar observations, are gaining skill at forecasting the large-scale solar-wind features that give rise to near-Earth variations over days and weeks. There remains a need for accurate short-term (hours to days) solar-wind forecasts, however. In this study we investigate the analogue ensemble (AnEn), or “similar day”, approach that was developed for atmospheric weather forecasting. The central premise of the AnEn is that past variations that are analogous or similar to current conditions can be used to provide a good estimate of future variations. By considering an ensemble of past analogues, the AnEn forecast is inherently probabilistic and provides a measure of the forecast uncertainty. We show that forecasts of solar-wind speed can be improved by considering both speed and density when determining past analogues, whereas forecasts of the out-of-ecliptic magnetic field [\(B_{\mathrm{N}}\)] are improved by also considering the in-ecliptic magnetic-field components. In general, the best forecasts are found by considering only the previous 6?–?12 hours of observations. Using these parameters, the AnEn provides a valuable probabilistic forecast for solar-wind speed, density, and in-ecliptic magnetic field over lead times from a few hours to around four days. For \(B_{\mathrm{N}}\), which is central to space-weather disturbance, the AnEn only provides a valuable forecast out to around six to seven hours. As the inherent predictability of this parameter is low, this is still likely a marked improvement over other forecast methods. We also investigate the use of the AnEn in forecasting geomagnetic indices Dst and Kp. The AnEn provides a valuable probabilistic forecast of both indices out to around four days. We outline a number of future improvements to AnEn forecasts of near-Earth solar-wind and geomagnetic conditions.  相似文献   

The Whole Heliosphere Interval in the Context of a Long and Structured Solar Minimum: An Overview from Sun to Earth     

S. E. Gibson  G. de Toma  B. Emery  P. Riley  L. Zhao  Y. Elsworth  R. J. Leamon  J. Lei  S. McIntosh  R. A. Mewaldt  B. J. Thompson  D. Webb 《Solar physics》2011,274(1-2):5-27

Throughout months of extremely low solar activity during the recent extended solar-cycle minimum, structural evolution continued to be observed from the Sun through the solar wind and to the Earth. In 2008, the presence of long-lived and large low-latitude coronal holes meant that geospace was periodically impacted by high-speed streams, even though solar irradiance, activity, and interplanetary magnetic fields had reached levels as low as, or lower than, observed in past minima. This time period, which includes the first Whole Heliosphere Interval (WHI 1: Carrington Rotation (CR) 2068), illustrates the effects of fast solar-wind streams on the Earth in an otherwise quiet heliosphere. By the end of 2008, sunspots and solar irradiance had reached their lowest levels for this minimum (e.g., WHI 2: CR 2078), and continued solar magnetic-flux evolution had led to a flattening of the heliospheric current sheet and the decay of the low-latitude coronal holes and associated Earth-intersecting high-speed solar-wind streams. As the new solar cycle slowly began, solar-wind and geospace observables stayed low or continued to decline, reaching very low levels by June??C?July 2009. At this point (e.g., WHI 3: CR 2085) the Sun?CEarth system, taken as a whole, was at its quietest. In this article we present an overview of observations that span the period 2008??C?2009, with highlighted discussion of CRs 2068, 2078, and 2085. We show side-by-side observables from the Sun??s interior through its surface and atmosphere, through the solar wind and heliosphere and to the Earth??s space environment and upper atmosphere, and reference detailed studies of these various regimes within this topical issue and elsewhere.  相似文献   

Expert assessment of vulnerability of permafrost carbon to climate change     

E. A. G. Schuur  B. W. Abbott  W. B. Bowden  V. Brovkin  P. Camill  J. G. Canadell  J. P. Chanton  F. S. Chapin III  T. R. Christensen  P. Ciais  B. T. Crosby  C. I. Czimczik  G. Grosse  J. Harden  D. J. Hayes  G. Hugelius  J. D. Jastrow  J. B. Jones  T. Kleinen  C. D. Koven  G. Krinner  P. Kuhry  D. M. Lawrence  A. D. McGuire  S. M. Natali  J. A. O’Donnell  C. L. Ping  W. J. Riley  A. Rinke  V. E. Romanovsky  A. B. K. Sannel  C. Schädel  K. Schaefer  J. Sky  Z. M. Subin  C. Tarnocai  M. R. Turetsky  M. P. Waldrop  K. M. Walter Anthony  K. P. Wickland  C. J. Wilson  S. A. Zimov 《Climatic change》2013,119(2):359-374

Approximately 1700 Pg of soil carbon (C) are stored in the northern circumpolar permafrost zone, more than twice as much C than in the atmosphere. The overall amount, rate, and form of C released to the atmosphere in a warmer world will influence the strength of the permafrost C feedback to climate change. We used a survey to quantify variability in the perception of the vulnerability of permafrost C to climate change. Experts were asked to provide quantitative estimates of permafrost change in response to four scenarios of warming. For the highest warming scenario (RCP 8.5), experts hypothesized that C release from permafrost zone soils could be 19–45 Pg C by 2040, 162–288 Pg C by 2100, and 381–616 Pg C by 2300 in CO₂ equivalent using 100-year CH₄ global warming potential (GWP). These values become 50 % larger using 20-year CH₄ GWP, with a third to a half of expected climate forcing coming from CH₄ even though CH₄ was only 2.3 % of the expected C release. Experts projected that two-thirds of this release could be avoided under the lowest warming scenario (RCP 2.6). These results highlight the potential risk from permafrost thaw and serve to frame a hypothesis about the magnitude of this feedback to climate change. However, the level of emissions proposed here are unlikely to overshadow the impact of fossil fuel burning, which will continue to be the main source of C emissions and climate forcing.  相似文献   

The Corwen Outlier and its implications for the Mid Mississippian palaeogeography of North Wales,UK     

Jeremy R. Davies  Nick J. Riley  David Wilson 《Geological Journal》2014,49(3):303-326

The isolated outlier of Visean (Mid Mississippian) limestones and sandstones near Corwen, North Wales, UK, provides a critical constraint on regional tectonic and palaeogeographical models. The late Asbian to Brigantian succession comprises a series of shoaling‐upwards cycles (parasequences). These were the product of forced, glacioeustatic regressions and have boundaries that testify to emergence, karstic dissolution and soil formation on a low gradient carbonate platform prior to flooding and the resumption of marine deposition. The recognition of two of the main marker beds within the North Wales Visean succession (Main Shale and Coral Bed) together with a newly applied foraminiferal and algal biozonation allow the outlier succession to be correlated with other Visean outcrops in the region and more widely throughout the British Isles. In revealing regional thickness and facies variations, these comparisons show that the outlier succession was deposited landward of the early Asbian shoreline in a region of enhanced subsidence localized along the Bala Lineament. The Corwen Outlier suggests that, within narrow gulfs associated with the region's major tectonic lineaments, Mississippian carbonate facies extended farther south into the contemporary hinterland of older rocks and that, in response to Brigantian climate change, these topographic features likely also influenced fluvial catchments supplying siliciclastic sediment to the platform's landward margin and, subsequently, Namurian deltas. Contrary to earlier suggestions, Visean outcrop patterns, facies distributions and thicknesses in the vicinity of the Bala Lineament can be explained without the need to invoke extensive post‐depositional lateral displacements. BGS © NERC 2013. Geological Journal © John Wiley & Sons Ltd.  相似文献