Simulation of the subsurface mobility of carbon nanoparticles at the field scale     

Erin Cullen  Denis M. O’Carroll  Ernest K. Yanful  Brent Sleep 《Advances in water resources》2010

The production and use of nanomaterials will inevitably lead to their disposal in the natural environment. To assess the risk that these materials pose to human and ecosystem health an understanding of their mobility and ultimate fate is essential. To date, however, relatively little research has been conducted on the fate of nanoparticles in subsurface systems. In this study the subsurface mobility of two carbon nanoparticles: nano-fullerenes (nC₆₀) and multi-walled carbon nanotubes (MWCNTs) is assessed. A two-dimensional finite element model was used to simulate the movement of these nanoparticles under a range of hydrologic and geological conditions, including a heterogeneous permeability field. The numerical model is based on colloid filtration theory (CFT) with a maximum retention capacity term. For the conditions evaluated the carbon nanotubes are much more mobile than nC₆₀ due to the smaller collector efficiency associated with carbon nanotubes. However, the mobility of nC₆₀ increased significantly when a maximum retention capacity term was included in the model. Model results also demonstrate that, for the systems examined, nanoparticles were predicted to be less mobile in heterogeneous systems compared to the homogeneous systems with the same average hydraulic properties.  相似文献   

Multi-decadal scale variability in autumn-winter rainfall in south-western Australia since 1655 AD as reconstructed from tree rings of Callitris columellaris   总被引：1，自引：0，他引：1  

Louise E. Cullen  Pauline F. Grierson 《Climate Dynamics》2009,33(2-3):433-444

We present the first tree-ring based reconstruction of rainfall for the Lake Tay region of southern Western Australia. We examined the response of Callitris columellaris to rainfall, the southern oscillation index (SOI), the southern annular mode (SAM) and surface sea temperature (SST) anomalies in the southern Indian Ocean. The 350-year chronology was most strongly correlated with rainfall averaged over the autumn-winter period (March–September; r = ?0.70, P < 0.05) and SOI values averaged over June–August (r = 0.25, P < 0.05). The chronology was not correlated with SAM or SSTs. We reconstructed autumn-winter rainfall back to 1655, where current and previous year tree-ring indices explained 54% of variation in rainfall over the 1902–2005 calibration period. Some variability in rainfall was lost during the reconstruction: variability of actual rainfall (expressed as normalized values) over the calibration period was 0.78, while variability of the normalized reconstructed values over the same period was 0.44. Nevertheless, the reconstruction, combined with spectral analysis, revealed that rainfall naturally varies from relatively dry periods lasting to 20–30 years to 15-year long periods of above average rainfall. This variability in rainfall may reflect low-frequency variation in the El Niño-Southern Oscillation rather than the effect of SAM or SSTs.  相似文献   

Silver in the subarctic northeast Pacific Ocean: Explaining the basin scale distribution of silver     

Dennis Kramer  Jay T. Cullen  James R. Christian  W. Keith Johnson  Thomas F. Pedersen 《Marine Chemistry》2011,123(1-4):133-142

Five vertical profiles of silver (Ag) in the subarctic northeast Pacific are presented. Dissolved (< 0.2 μm) Ag concentrations within the surface mixed layer range from 6–25 pM, with the highest observed values at the most coastal site. Elevated Ag concentrations at this station are most likely attributable to the estuarine circulation in the Juan de Fuca Strait. One open-ocean station (P20) exhibited a strong surface Ag maximum. The station was located at the edge of a Haida eddy which raises the possibility that such eddies transport Ag seaward from the coastal zone. Ag concentrations in the deep waters ranged from 60–80 pM. These measurements are consistent with other recent Ag data collected in the Pacific. Ag profiles throughout the Pacific Ocean yield a strong positive correlation between Ag concentration and dissolved silicic acid concentration. However, Ag is depleted relative to silicic acid at intermediate depths where dissolved O₂ concentrations are low, implying a possible removal of Ag from oxygen-depleted waters by scavenging and/or precipitation.  相似文献   

The occurrence of distal Icelandic and Italian tephra in the Lateglacial of Lake Bled,Slovenia     

Christine S. Lane  Maja Andrič  Victoria L. Cullen  Simon P.E. Blockley 《Quaternary Science Reviews》2011,30(9-10):1013-1018

The discovery of sites preserving tephra layers from multiple volcanic centres is key to constructing a single European tephrostratigraphic framework for the Late Quaternary. Until now, the tephrostratigraphy of Europe has been divided into two halves: sites in the North Atlantic and northern Europe regions link the Icelandic, Eifel, and the Massif Central volcanic histories; whilst sites in southern Europe record the sequence of tephra layers produced by circum-Mediterranean volcanic provinces. The missing link, able to tie together these two halves, is found in the tephrostratigraphic record of Lake Bled, Slovenia.Lake Bled, in the Julian Alps, Slovenia, holds a high resolution multi-proxy palaeoenvironmental archive for the Lateglacial of south-central Europe. Cryptotephra investigations have revealed three tephra layers: two closely spaced within Younger Dryas stadial sediments and one shortly after the start of the Bølling-Allerød interstadial warming. Two of the tephra layers (Bld_T120 and Bld_T240) are of Campanian origin and are correlated to deposits of the Pomici Principali (PP) and Neapolitan Yellow Tuff (NYT) eruptions, respectively. The third layer (Bld_T122) correlates to the Icelandic Vedde Ash (VA), extending the known fallout of this widespread marker layer farther to the southeast.The Lake Bled record also allows the stratigraphic relationship and relative ages of the VA and the PP eruption to be discerned for the first time. Whilst existing numerical age estimates for these two deposits are indistinguishable within errors, their close occurrence in the same lacustrine sediment sequence shows that the VA was erupted shortly prior to the PP eruption.The tephrostratigraphy of Lake Bled developed here helps us to tie together regional volcanic stratigraphies into a broader, continental-scale lattice of sites, with the potential to allow the transfer of dates between remote sequences and the construction of relative chronologies, beneficial in particular for environmental and archaeological research.  相似文献   

Systematic errors in weak lensing: application to SDSS galaxy–galaxy weak lensing     

Rachel Mandelbaum  Christopher M. Hirata  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Michael R. Blanton  Robert Lupton  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2005,361(4):1287-1322

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The hot, warm and cold gas in Arp 227 – an evolving poor group     

R. Rampazzo  P. Alexander  C. Carignan  M. S. Clemens  H. Cullen  O. Garrido  M. Marcelin  K. Sheth  G. Trinchieri 《Monthly notices of the Royal Astronomical Society》2006,368(2):851-863

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Evidence for Holocene Aeolian Activity at the Close of the Middle Bronze Age in the Eastern Carpathian Basin: Geoarchaeological Results from the Mureş River Valley,Romania     

Sarah C. Sherwood  Jason D. Windingstad  Alex W. Barker  John M. O'Shea  W. Cullen Sherwood 《Geoarchaeology》2013,28(2):131-146

While extensive Pleistocene loess deposits have been identified across Eurasia, Holocene age loess (typically nonglaciogenic) is rarely recognized. We explore possible loess deposits in the Mureş River Valley of western Romania, providing a regional signal of increased aridity during the mid‐late Holocene. This proposed aridity may be responsible for the abandonment of Middle Bronze Age tell settlements along the major drainages of the eastern Carpathian Basin (Pannonian plain). This hypothesis centers on a proposed aeolian deposit (the “Pecica deposit”), a ca. 50–80 cm thick, relatively homogeneous, gray layer blanketing the top of the Bronze Age tell of Pecica—Şanţul Mare. Comparing the morphological, geochemical, and physical characteristics of this specific tell deposit with two representative profiles near the site containing glaciogenic calcareous loess and potential Holocene loess deposits developed in Chernozems, we find significant similarities to support this hypothesis. We then review various forms of proxy data published from elsewhere in Central and Eastern Europe suggesting a warming trend during this period. The temporal placement of the Pecica deposit is bracketed using diagnostic artifacts, radiocarbon dates, and the degree of soil development, suggesting a period of increased aridity likely occurring soon after the 17th century B.C.  相似文献   

Journal review     

David J. Cullen 《新西兰海洋与淡水研究杂志》2013,47(3):619-620

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The age of glauconite from the Chatham rise,east of New Zealand     

David J. Cullen 《新西兰海洋与淡水研究杂志》2013,47(4):399-406

Radiometric analysis indicates that a granular variety of glauconite, widespread on the Chatham Rise, is derived from late Tertiary sediments. Other forms of glauconite, associated with pumice, phosphorite nodules, and glacially‐transported erratic blocks, are of Quaternary age. These are quantitatively unimportant, and may have originated as a result of redistribution of components from the older glauconite.  相似文献   

Compton scattering of Fe Kα lines in magnetic cataclysmic variables     

A. L. McNamara  Z. Kuncic  K. Wu  D. K. Galloway †  J. G. Cullen 《Monthly notices of the Royal Astronomical Society》2008,383(3):962-970

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