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961.
Biotransformation of Benzene by Denitrification in Aquifer Sand 总被引:9,自引:0,他引:9
962.
963.
7000 years of paleostorm activity in the NW Mediterranean Sea in response to Holocene climate events
Pierre Sabatier Laurent Dezileau Christophe Colin Louis Briqueu Frédéric Bouchette Philippe Martinez Giuseppe Siani Olivier Raynal Ulrich Von Grafenstein 《Quaternary Research》2012,77(1):1-11
A high-resolution record of paleostorm events along the French Mediterranean coast over the past 7000 years was established from a lagoonal sediment core in the Gulf of Lions. Integrating grain size, faunal analysis, clay mineralogy and geochemistry data with a chronology derived from radiocarbon dating, we recorded seven periods of increased storm activity at 6300–6100, 5650–5400, 4400–4050, 3650–3200, 2800–2600, 1950–1400 and 400–50 cal yr BP (in the Little Ice Age). In contrast, our results show that the Medieval Climate Anomaly (1150–650 cal yr BP) was characterised by low storm activity.The evidence for high storm activity in the NW Mediterranean Sea is in agreement with the changes in coastal hydrodynamics observed over the Eastern North Atlantic and seems to correspond to Holocene cooling in the North Atlantic. Periods of low SSTs there may have led to a stronger meridional temperature gradient and a southward migration of the westerlies. We hypothesise that the increase in storm activity during Holocene cold events over the North Atlantic and Mediterranean regions was probably due to an increase in the thermal gradient that led to an enhanced lower tropospheric baroclinicity over a large Central Atlantic–European domain. 相似文献
964.
Gregory D. Price Elizabeth Harwood 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(3):479-485
Cretaceous brachiopods (Moutonithyris dutempleana) and belemnites (Neohibolites minimus) from the (Albian) Hunstanton Red Chalk Formation (Hunstanton, UK) were isotopically analysed with the aim of identifying palaeoecological and palaeotemperature trends. Shell preservation was assessed via thin section petrography and geochemical analyses. Oxygen isotopic compositions (and corresponding temperature interpretations) of well-preserved belemnites are similar in comparison to the brachiopod shells. Assuming calcite precipitation in isotopic equilibrium, they are interpreted to have occupied the same or similar warm (15–19 °C) shallow marine environment. Further, these findings indicate that the belemnites mineralised in relatively warm waters and not in deep and cool waters as suggested for some belemnite species. The isotope data are thus inconsistent with the belemnites being associated with a cool water pulse, contrasting with events associated with the Cenomanian chalks. A difference δ13C between the belemnites and brachiopods is interpreted to originate from differences in metabolic rates. 相似文献
965.
Paired watersheds are used to develop a deciduous nutrient uptake stoichiometry. The watersheds are those of the House Rock Run and the Brubaker Run located in the Pennsylvania Appalachian Piedmont, USA. These two watersheds are nearly identical with respect to bedrock, regolith, climate, geomorphology, morphometry, baseflow hydrology, and type and successional stage of forest vegetation. They only differ by the percentage of deciduous forest cover, with House Rock Run having 59% and Brubaker Run having 76%. From differences in their stream chemistries the biomass nutrient uptake stoichiometry of K1.0Mg1.0Ca1.4 was determined. This stoichiometry applies to an aggrading deciduous biomass and differs from those previously used which were derived from net primary production (NPP) data. The difference may reflect that macronutrients in plant tissue may also originate from atmospheric inputs and/or decomposing biomass. Although this stoichiometry may not be applied to all deciduous forest-covered watersheds, it is likely an improvement over a stoichiometry determined from NPP data. 相似文献
966.
Amartya K. Saha Christopher S. Moses René M. Price Victor Engel Thomas J. SmithIII Gordon Anderson 《Estuaries and Coasts》2012,35(2):459-474
Water budget parameters are estimated for Shark River Slough (SRS), the main drainage within Everglades National Park (ENP)
from 2002 to 2008. Inputs to the water budget include surface water inflows and precipitation while outputs consist of evapotranspiration,
discharge to the Gulf of Mexico and seepage losses due to municipal wellfield extraction. The daily change in volume of SRS
is equated to the difference between input and outputs yielding a residual term consisting of component errors and net groundwater
exchange. Results predict significant net groundwater discharge to the SRS peaking in June and positively correlated with
surface water salinity at the mangrove ecotone, lagging by 1 month. Precipitation, the largest input to the SRS, is offset
by ET (the largest output); thereby highlighting the importance of increasing fresh water inflows into ENP for maintaining
conditions in terrestrial, estuarine, and marine ecosystems of South Florida. 相似文献
967.
Gregory R. Koch Daniel L. Childers Peter A. Staehr René M. Price Stephen E. Davis Evelyn E. Gaiser 《Estuaries and Coasts》2012,35(1):292-307
Using high-resolution measures of aquatic ecosystem metabolism and water quality, we investigated the importance of hydrological
inputs of phosphorus (P) on ecosystem dynamics in the oligotrophic, P-limited coastal Everglades. Due to low nutrient status
and relatively large inputs of terrestrial organic matter, we hypothesized that the ponds in this region would be strongly
net heterotrophic and that pond gross primary production (GPP) and respiration (R) would be the greatest during the “dry,”
euhaline estuarine season that coincides with increased P availability. Results indicated that metabolism rates were consistently
associated with elevated upstream total phosphorus and salinity concentrations. Pulses in aquatic metabolism rates were coupled
to the timing of P supply from groundwater upwelling as well as a potential suite of hydrobiogeochemical interactions. We
provide evidence that freshwater discharge has observable impacts on aquatic ecosystem function in the oligotrophic estuaries
of the Florida Everglades by controlling the availability of P to the ecosystem. Future water management decisions in South
Florida must include the impact of changes in water delivery on downstream estuaries. 相似文献
968.
Laxmi Kant Kachhwal Ernest K. Yanful Colin D. Rennie 《Environmental Earth Sciences》2012,66(3):823-834
Wind-driven waves and currents exert shear stress on the bed of a tailings pond. A semi-empirical approach for estimating this bed shear stress is presented in this paper. For the first time in a mine tailings storage facility, the current-induced component of the bed shear stress was obtained using 1,200-kHz acoustic Doppler current profiler measurements of in situ currents and a log-law fit to the mean velocity profiles, while the wave-induced portion was calculated using empirical wave hindcasting equations. The total bed shear stress was obtained by non-linear addition of wave and current components using a wave–current interaction approach. The study was conducted in the middle cell of the Shebandowan tailings storage facility, northern Ontario, Canada. The measured currents facilitated the visualization of the complex near-bed circulatory flow pattern in the pond. The estimated combined wave–current bed shear stress varied from 0.0006 to 0.16 Pa with an average value of 0.028 Pa. The results also showed that linear addition of bed shear stresses due to waves and currents could underestimate the total bed shear stress. A comparison of the results of the present work to those of previous studies suggests that it is more reliable to obtain current-induced bed shear stress from field measurements than to estimate it from empirical equations. 相似文献
969.
Sepideh Saeidi Seyed Hamed Mirkarimi Marjan Mohammadzadeh Abdolrassoul Salmanmahiny Colin Arrowsmith 《国际地球制图》2013,28(12):1381-1397
AbstractThis study demonstrates the integration of landscape aesthetic quality and probable urban growth patterns in urban landscape modelling. This was performed using SLEUTH as a scenario-based urban growth model in Gorgan City of Iran. Future urbanization was predicted under developing three different scenarios including historical, managed and aesthetically sound urban growth up to the year 2030. Multi-Layer Perceptron neural network model was conducted for mapping the aesthetic suitability of the study area. The aesthetic suitability layer was used in the third scenario of SLEUTH model as the excluded layer to protect the scenic patches in future. The results showed that by correct implementation of urban growth policies, 323 ha in the second scenario and 650 ha in the third scenario would be saved. This integrated model would help the planners for a better management of urban landscapes as a Spatial Decision Support System. 相似文献
970.
Edward A. Bryant Robert W. Young David M. Price David J. Wheeler Mark I. Pease 《自然地理学》2013,34(5):440-459
The Jervis Bay area offers a diversity of landforms that do not fit within contemporary views of coastal evolution. Field evidence indicates that catastrophic tsunami have had a significant impact on the coast and its hinterland both within and outside the embayment. Runup has overtopped cliffs 80 m above sea level and deposited chevron-shaped ridges to elevations of 130 m on the southern headland. Boulders, up to 6 m in diameter, have been deposited in an imbricated fashion against cliffs, on clifftops, and along shoreline ramps. Bed-form features and the size of transported material indicate flow depths up to 10 m and velocities around 8 m s-1. While significant Pleistocene material has been swept onto the coastline, mainly in the form of barriers, radiocarbon dating indicates that tsunami have occurred repetitively throughout the Holocene. The most recent event occurred just before European settlement over 200 years ago. [Key words: barrier beaches, coastal geomorphology, tsunami, Jervis Bay, Australia.] 相似文献