The Effects of Salinity on Nitrogen Losses from an Oligohaline Estuarine Sediment   总被引：4，自引：0，他引：4  

Anne E. Giblin  Nathaniel B. Weston  Gary T. Banta  Jane Tucker  Charles S. Hopkinson 《Estuaries and Coasts》2010,33(5):1054-1068

Benthic respiration, sediment–water nutrient fluxes, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) were measured in the upper section of the Parker River Estuary from 1993 to 2006. This site experiences large changes in salinity over both short and long time scales. Sediment respiration ranged from 6 to 52 mmol m⁻² day⁻¹ and was largely controlled by temperature. Nutrient fluxes were dominated by ammonium fluxes, which ranged from a small uptake of −0.3 to an efflux of over 8.2 mmol N m⁻² day⁻¹. Ammonium fluxes were most highly correlated with salinity and laboratory experiments demonstrated that ammonium fluxes increased when salinity increased. The seasonal pattern of DNRA closely followed salinity. DNRA rates were extremely low in March, less than 0.1 mmol m⁻² day⁻¹, but increased to 2.0 mmol m⁻² day⁻¹ in August. In contrast, denitrification rates were inversely related to salinity, ranging from 1 mmol m⁻² day⁻¹ during the spring and fall to less than 0.2 mmol m⁻² day⁻¹ in late summer. Salinity appears to exert a major control on the nitrogen cycle at this site, and partially decouples sediment ammonium fluxes from organic matter decomposition.  相似文献   

MegaZ-LRG: a photometric redshift catalogue of one million SDSS luminous red galaxies     

Adrian Collister  Ofer Lahav  Chris Blake  Russell Cannon  Scott Croom  Michael Drinkwater  Alastair Edge  Daniel Eisenstein  Jon Loveday  Robert Nichol  Kevin Pimbblet  Roberto De Propris  Isaac Roseboom  Nic Ross  Donald P. Schneider  Tom Shanks  David Wake 《Monthly notices of the Royal Astronomical Society》2007,375(1):68-76

We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range  0.4 < z < 0.7  with limiting magnitude   i < 20  . The catalogue is selected from the imaging data of the Sloan Digital Sky Survey (SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13 000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of ann z, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is  σ _z = 0.049  averaged over all galaxies, and  σ _z = 0.040  for a brighter subsample  ( i < 19.0)  . The catalogue is expected to contain ∼5 per cent stellar contamination. The ann z code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly available on the World Wide Web from http://www.2slaq.info .  相似文献   

Post miocene volcanoes on Bougainville Island,territory of Papua and New Guinea     

D. H. Blake 《Bulletin of Volcanology》1968,32(1):121-138

Seventeen post-Miocene strato volcanoes have been identified on Bougainville, the largest island of the Solomon Group. From north-west to south-east, these are the Tore, Balbi, Numa Numa, Billy Mitchell, Bagana, Reini, and Bakanovi volcanoes and the Takuan and Toroka groups of volcanoes: the Taroka group includes Loloru volcano. In addition there are several other post-Miocene volcanoes in northern Bougainville which have not been accurately delineated. Only three of the volcanoes are active or potentially active; these are Bagana, the most active volcano in the Territory of New Guinea, and the dormant Balbi and Loloru volcanoes. The volcanoes are built up of lavas and pyroclastic deposits mostly of andesitic composition, although some dacitic rocks are also present. Modal and chemical analyses show that these rocks belong to the calc-alkaline suite characteristic of orogesic regions.  相似文献   

Regional and economic geology of Pennsylvanian age coal beds of West Virginia     

T.E. Repine Jr.  B.M. Blake  K.C. Ashton  N. Fedorko III  A.F. Keiser  E.I. Loud  C.J. Smith  S.W. McClelland  G.H. McColloch 《International Journal of Coal Geology》1993,23(1-4)

West Virginia is the only place in the United States where an entire section of Pennsylvanian age (Upper Carboniferous) strata can be seen. These strata occur within a wedge of rock that thins to the north and west from the southeastern part of the State. The progressive north-northwesterly termination of older Pennsylvanian geologic units beneath younger ones prominently outlines the center of the Appalachian basin of West Virginia. Over most of West Virginia, Lower and/or Middle Pennsylvanian strata unconformably overly Upper Mississippian (Lower Carboniferous) strata. Sediment deposition was accomplished by a complex system of deltas prograding north and west from an eastern and southeastern source area.More than 100 named coal beds occur within the Lower, Middle, and Upper Pennsylvanian rocks of West Virginia and at least 60 of these have been or are currently being mined commercially. Collectively, these coal beds account for original in-ground coal resources of almost 106.1×10⁹ t (117×10⁹ tons). West Virginia ranks fourth in the United States in demonstrated coal reserves. In 1988, West Virginia produced 131.4×10⁶ t (144.9×10⁶ T) of coal, third highest in the United States. Of this annual production, 75% was from underground mines. In 1988, West Virginia led the nation in the number of longwall mining sections currently in place. West Virginia's low-volatile coal beds are known worldwide as important metallurgical-grade coals, while the higher-volatile coal beds are utilized primarily for steam production.  相似文献   

Bioaccumulation and histopathological effects of oil on a stony coral     

Esther C. Peters  Philip A. Meyers  Paul P. Yevich  Norman J. Blake 《Marine pollution bulletin》1981,12(10):333-339

Colonies of the shallow-water Caribbean coral Manicina areolata incorporated petroleum hydrocarbons into their tissues during exposure to water accommodated fractions of No. 2 fuel oil for three months. This contamination was not removed after depuration periods of up to two weeks. Although these corals remained alive, evidence of pathological responses was found which included impaired development of reproductive tissues, degeneration and loss of symbiotic zooxanthellae, and atrophy of mucous secretory cells and muscle bundles.  相似文献   

UNDERGROUND OIL RECOVERY     

Steven B. Blake  Richard W. Lewis 《Ground Water Monitoring & Remediation》1983,3(2):40-46

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Volcanoes of the Cape Hoskins area,New Britain,territory of Papua and New Guinea     

D. H. Blake  P. Bleeker 《Bulletin of Volcanology》1970,34(2):385-405

One active and ten extinct Quaternary volcanoes are described from the Cape Hoskins area, on the north coast of New Britain. They are mostly strato volcanoes built up of lava flows, lava domes, pyroclastic flows, lahars, tephra, and derived alluvial sediments. The volcanic products range in composition from basalt to rhyolite, but basaltic andesite and andesite predominate. Much of the area is covered by tephra, several metres thick, consisting mainly of rhyolitic pumice. The active volcano, Pago, is built up of several glacier-like lava flows, the last of which was formed during an eruption in 1914–18. Pago lies within a well-preserved caldera forming the central part of a broad low-angle cone, named Witori, which consists largely of welded and unwelded pyroclastic flow deposits. C-14 dates obtained on charcoal indicate that the caldera eruption occurred about 2500 years B. P. Another caldera of similar age lies south of Witori. Of the other eight volcanoes described four are relatively well-preserved steep-sided cones formed mainly of lava flows, one is a remnant of a low-angle cone with a caldera, and three are deeply eroded cones which have none of their constructional surfaces preserved.  相似文献   

Seasonal trends in the uranium-series istopic signatures of lake waters and sediments: Hawes Water, north-west England     

William H. Blake  Andrew J. Plater  John F. Boyle 《Journal of Paleolimnology》1998,20(1):1-14

Potential seasonal variation in the U-series radioisotopic signatures of lake and input waters was investigated in Hawes Water, north-west England, and the sedimentary record was examined to establish whether any observed seasonality is preserved in the sediment U and Th radioisotopic activity ratios. U-series disequilibrium in the waters is indicative of both surface and shallow sub-surface origins for the dissolved U, and that this supply is influenced by changes in the prevailing hydrological regime. However, the lake is buffered from this seasonality in that the ²³⁴U/²³⁸U activity ratio remains constant during the year, and the U content undergoes only a marginal decrease during summer. The change in the mechanism of lake sedimentation from allochthonous organic input during winter to autochthonous carbonate formation during summer has a more significant influence on the U-series radioisotopic characteristics of sedimentary record in that the proportion of organic and carbonate material both exhibit a strong control on the²³⁴U/²³⁸U activity ratio and U content. In addition, significant proportions of sediment U and Th are associated with ferromanganese oxyhydroxides. Given this seasonality, it is of some significance that the ²³⁴U/²³⁸U activity ratios of the bottom sediments preserve a reasonable record of lake U-series disequilibrium and are, therefore, potential indicators of long-term changes in catchment hydrology.  相似文献   

Molecular orbital models of aqueous aluminum-acetate complexes     

J.D. Kubicki  G.A. Blake  S.E. Apitz 《Geochimica et cosmochimica acta》1996,60(24):4897-4911

Molecular orbital calculations with HF/3-21G^∗∗, HF/6-311+G^∗∗, and MP2/6-311+G^∗∗ basis sets (HF = Hartree-Fock approximation; MP2 = 2nd-order Møller-Plesset perturbation theory) have been performed on molecular clusters in the system acetate-aluminum-water. The results model the structures, energetics, and vibrational spectra of Al³⁺ and Al³⁺-acetate complexes in the aqueous phase. An octahedral to tetrahedral coordination change is predicted in the species Al³⁺ (OH)_m⁻ · n (H₂O) [where m + n = 6) as m increases from two to three. Calculated reaction energetics for aqueous Al³⁺-acetate complexation compare favorably with experimental enthalpies. In addition, the possible existence of more than one configuration for each Al` -acetate species was investigated. Theoretical vibrational spectra of the Al³⁺-acetate complexes provide predictions for the identification of Al³⁺-acetate species in aqueous solutions.  相似文献   

High-Latitude Springtime Photochemistry. Part Ii: Sensitivity Studies of Ozone Production     

John a. Herring  Daniel a. Jaffe  Harald J. Beine  Sasha Madronich  Donald R. Blake 《Journal of Atmospheric Chemistry》1997,27(2):155-178

A seven-year record of surface ozone measurements from Denali NationalPark, Alaska shows a persistent spring maximum. These data, combined withmeasurements of NO_x, hydrocarbons, O₃, and PANfrom a continental site in Alaska during the spring of 1995 are used as thebasis for a sensitivity study to explore tropospheric photochemistry in thisregion. Because of the relatively high concentrations of NO_x(mean of 116, median of 91 pptv), the net tendency was for photochemicalozone production. The range of net O₃ production for averageconditions measured at this site during spring is between 0.96–3.9ppbv/day depending on the assumptions used; in any case, this productionmust contribute to the observed springtime maximum in O₃.Model calculations showed that of the anthropogenic ozone precursors, onlyNO_x had a strong effect on the rate of ozone production; themeasured concentrations of anthropogenic hydrocarbons did not significantlyaffect the ozone budget. Naturally produced biogenic hydrocarbons, such asisoprene, may also have a significant effect on ozone production, even atconcentrations of a few 10's of pptv. An observed temperature-isoprenerelationship from a boreal site in Canada indicates that isoprene may bepresent during the Alaskan spring. Measurements of isoprene taken duringthe spring of 1996 suggest that reactive biogenic hydrocarbon emissionsbegin before the emergence of leaves on deciduous trees and that theconcentrations were sufficient to accelerate ozone production.  相似文献