Apparent magnetic polarity reversals due to remagnetization resulting from late diagenetic growth of greigite from siderite     

Leonardo Sagnotti  rew P. Roberts  Richard Weaver  Kenneth L. Verosub  Fabio Florindo  Christopher R. Pike  Trevor Clayton  Gary S. Wilson 《Geophysical Journal International》2005,160(1):89-100

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Collocation of hydrological and biological attenuation of nitrate in an urban stream          下载免费PDF全文

Trevor Klein  Laura Toran 《水文研究》2016,30(17):2948-2957

The hydrologic and biogeochemical processes that control nutrient export in urban streams are not well understood. Attenuation can occur by tributary dilution, groundwater discharge, and biological processing both in the water column and the hyporheic zone. A wastewater treatment plant on Pennypack Creek, an urban stream near Philadelphia, PA, provided high nitrate concentrations for analysis of downstream attenuation processes. Longitudinal sampling for an 8‐km reach revealed decreases in nitrate concentration of 2 mg l^?1 at high flow and 4.5 mg l^?1 during low flow. During high flow, δ¹⁵N‐NO₃ increased from 9.5 to 10.5‰ and during low flow increased from 10.1 to 11.1‰. Two reaches were sampled at fine spatial intervals (approximately 200 m) to better identify attenuation processes. Mixing analysis indicated that groundwater discharge and biological processing both control nitrate concentration and isotope signatures. However, fine‐scaled sampling did not reveal spatially discrete zones; instead, these processes were occurring simultaneously. While both processes attenuate nitrate, they have opposite isotope signatures, which may have muted changes in δ¹⁵N‐NO₃. At high flow, a decrease in Cl/NO₃ ratios helped distinguish groundwater discharge occurring along both finely sampled reaches. At low flow, biological processing seemed to be occurring more extensively, but the δ¹⁵N‐NO₃ signature was not consistent with either a single process or a sequential combination of groundwater dilution and biological nitrate attenuation. The collocation of processes makes it more difficult to assess biological processing hot spots and predict how urbanization and subsequent stream restoration influence nitrate attenuation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

An assessment of the climate change impacts on groundwater recharge at a continental scale using a probabilistic approach with an ensemble of GCMs   总被引：1，自引：0，他引：1  

Russell S. Crosbie  Trevor Pickett  Freddie S. Mpelasoka  Geoff Hodgson  Stephen P. Charles  Olga V. Barron 《Climatic change》2013,117(1-2):41-53

This study used 16 Global Climate Models and three global warming scenarios to make projections of recharge under a 2050 climate for the entire Australian continent at a 0.05° grid resolution. The results from these 48 future climate variants have been fitted to a probability distribution to enable the results to be summarised and uncertainty quantified. The median results project a reduction in recharge across the west, centre and south of Australia and an increase in recharge across the north and a small area in the east of the continent. The range of results is quite large and for large parts of the continent encompasses both increases and decreases in recharge. This makes it difficult to utilise for water resources management so the results have been analysed with a risk analysis framework; this enables the future projections for groundwater recharge to be communicated to water managers in terms of likelihood and consequence of a reduction in recharge. This highlights an important message for water resource managers that in most areas of Australia they will be making decisions on water allocations under considerable uncertainty as to the direction and magnitude of recharge change under a future climate and that this uncertainty may be irreducible.  相似文献   

Future climate of the Caribbean from a super-high-resolution atmospheric general circulation model     

Trevor C. Hall  Andrea M. Sealy  Tannecia S. Stephenson  Shoji Kusunoki  Michael A. Taylor  A. Anthony Chen  Akio Kitoh 《Theoretical and Applied Climatology》2013,113(1-2):271-287

Present-day (1979–2003) and future (2075–2099) simulations of mean and extreme rainfall and temperature are examined using data from the Meteorological Research Institute super-high-resolution atmospheric general circulation model. Analyses are performed over the 20-km model grid for (1) a main Caribbean basin, (2) sub-regional zones, and (3) specific Caribbean islands. Though the model’s topography underestimates heights over the eastern Caribbean, it captures well the present-day spatial and temporal variations of seasonal and annual climates. Temperature underestimations range from 0.1 °C to 2 °C with respect to the Japanese Reanalysis and the Climatic Research Unit datasets. The model also captures fairly well sub-regional scale variations in the rainfall climatology. End-of-century projections under the Intergovernmental Panel on Climate Change SRES A1B scenario indicate declines in rainfall amounts by 10–20 % for most of the Caribbean during the early (May–July) and late (August–October) rainy seasons relative to the 1979–2003 baselines. The early dry season (November–January) is also projected to get wetter in the far north and south Caribbean by approximately 10 %. The model also projects a warming of 2–3 °C over the Caribbean region. Analysis of future climate extremes indicate a 5–10 % decrease in the simple daily precipitation intensity but no significant change in the number of consecutive dry days for Cuba, Jamaica, southern Bahamas, and Haiti. There is also indication that the number of hot days and nights will significantly increase over the main Caribbean basin.  相似文献   

X-ray scaling properties of early-type galaxies     

Ewan O'Sullivan  †  Trevor J. Ponman  Ross S. Collins 《Monthly notices of the Royal Astronomical Society》2003,340(4):1375-1399

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September 2004     

Thomas W. Merrill  Michael Platt  Marc D. Guerra  Ty Shaffer 《Environmental Geology》2004,46(5):683-684

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Tenerife – the big pyramid     

Trevor Greensmith 《Geology Today》2004,20(5):189-193

There is nothing like a good controversy in geology, when vehemently held conflicting opinions set the adrenaline running. The debate over hot spots or mantle plumes is developing in this way; as such it is pertinent to look at the Canary Islands archipelago where hot spot ideas have been in place for some time.  相似文献   

The X-ray emission in post-merger ellipticals     

Ewan O'Sullivan  Duncan A. Forbes  Trevor J. Ponman 《Monthly notices of the Royal Astronomical Society》2001,324(2):420-426

The evolution in X-ray properties of early-type galaxies is largely unconstrained. In particular, little is known about how, and if, remnants of mergers generate hot gas haloes. Here we examine the relationship between X-ray luminosity and galaxy age for a sample of early-type galaxies. Comparing normalized X-ray luminosity to three different age indicators, we find that L _X L _B increases with age, suggesting an increase in X-ray halo mass with time after the last major star formation episode of a galaxy. The long-term nature of this trend, which appears to continue across the full age range of our sample, poses a challenge for many models of hot halo formation. We conclude that models involving a declining rate of type Ia supernovae, and a transition from outflow to inflow of the gas originally lost by galactic stars, offer the most promising explanation for the observed evolution in X-ray luminosity.  相似文献   

FARMLAND CONVERSION: NATIONAL LESSONS FOR IOWA*     

Rutherford H. Platt 《The Professional geographer》1981,33(1):113-121

Between 1967 and 1975, United States cropland declined 30.5 million acres, of which 8 million acres were prime farmland. The rising gross farm product continues to outweigh such losses owing to short-term adjustments such as irrigation, but longer-term measures to conserve farmland are widely urged. Even Iowa, where urban growth is modest, is incurring some loss of superior farmland. Experience in other states offers certain lessons to Iowa: discourage unnecessary municipal annexations; evaluate the impact of public investments on farmland; expand tax preferences for agriculture; and assist counties to improve their land planning and regulatory efforts.  相似文献   

The group evolution multiwavelength study: the near-infrared luminosity function of nearby galaxy groups     

Trevor A. Miles  Somak Raychaudhury  Paul A. Russell 《Monthly notices of the Royal Astronomical Society》2006,373(4):1461-1469

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