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401.
Eric Heinen De Carlo Michael S. Tomlinson Laura E. deGelleke Sara Thomas 《Aquatic Geochemistry》2014,20(2-3):87-113
Lack of high-spatial-resolution soil and sediment arsenic data for Hawai‘i has generated substantial disagreement between researchers and regulators regarding the magnitude of natural levels of arsenic in Hawai‘i and rendered difficult the defining of areas of anthropogenically elevated arsenic. Our earlier research into the occurrence of arsenic in terrestrial and marine environments revealed widely disparate concentrations of arsenic with no apparent spatial pattern. To better understand the distribution and abundance of arsenic in soils and sediments of O‘ahu, we collected an additional 64 samples at locations chosen to represent different environments with varying degrees of human impact. We found surface arsenic values that ranged from 0.28 to 740 ppm with a median concentration of 8.1 ppm, which is above the global median of 5 ppm and US soil median of 5.2 ppm. Higher concentrations of arsenic (up to 913 ppm) were encountered at depth in soil cores. The median arsenic in streambed sediments from one of our earlier studies of 6.1 ppm was comparable to the conterminous US median of 6.3 ppm; however, we encountered arsenic concentrations as high as 43.9 ppm (median = 8.60 ppm, n = 75) in marine sediments in recent work off the leeward coast of O‘ahu. Overall, arsenic in the soils and sediments of O‘ahu is elevated relative to world and national values, but there still is no readily discernible pattern in the distribution of arsenic to explain these elevated values. 相似文献
402.
Megascopic, micropetrographic and scanning-electron microscopic investigations of fibrous coal indicate that paleo-wildfires were common occurrences in the mire which produced Highvale coals. At least 20 fibrous coal (fusain) horizons have been identified in corehole samples from the pit no. 3 locality at Highvale, in the central Alberta Plains. Thicknesses of individual horizons vary, and are not particular to any stratigraphic position within coal seams. The majority of these fibrous horizons is within the two thick economic seams, the Highvale Nos. 1 and 2, which are characteristically megascopically dull. The dullness of given lithotypes is largely related to inertinite content with fibrous coal containing 51% inertinite on average, and selected horizons comprised of as much as 85% inertinite. Semifusinite and inertodetrinite are the predominant inertinites, with a few horizons exhibiting highly reflecting fusinite. Macrinite is rare, and micrinite is absent. SEM investigations reveal that certain fibrous coals exhibit excellent preservation of the original gymnospermous (Taxodium) woody tissue. Features such as homogenization and swelling of the cell walls, elimination of the middle lamellae, and preservation of bordered pits are clearly indicative of charcoal formation as a product of paleo-wildfires. Depending upon the nature of the fire, temperatures obtained and the nature of the mire vegetation, a wide range of inertinite precursors can be produced. 相似文献
403.
Remineralization Ratios in the Subtropical North Pacific Gyre 总被引:2,自引:0,他引:2
Yuan-Hui Li David M. Karl Christopher D. Winn Fred T. Mackenzie Kathleen Gans 《Aquatic Geochemistry》2000,6(1):65-85
Based on a new mixing model of two end-members, the water column remineralization ratios of P/N/Corg - O2 = 1/13 ± 1/135 ± 18/170 ± 9 are obtained for the Hawaii Ocean Time-series (HOT) data set at station ALOHA. The traditional Redfield ratios of P/N/Corg/–O2 = 1/16/106/138 have standard deviations of more than 50%, when they are based on the average composition of phytoplankton. Apparently, the remineralization processes in the water column have smoothed out the observed large variability of plankton compositions. A new molar formula for the remineralized plankton may be written as 135H280O105N13P or C25(CH2O)101(CH4)9(NH3)13(H3PO4). Oxidation of this formula results inC25(CH2O)101(CH4)9(NH3)13(H3PO4) + 170O2 135CO2 + 132H2O + 13NO3
- + H2PO4
- + 14H+.For comparison, remineralization using Redfield's formula gives:(CH2O)106(NH3)16(H3PO4) + 138O2 106CO2 + 122H2O + 16NO3
-+ H2PO4
- + 17H+ 相似文献
404.
Fredric L. Prikle Thomas R. Bement Jo Ann Howell Charles D. Koch Newton K. Stablein Richard J. Beckman Gary L. Tietjen 《Journal of Geochemical Exploration》1983,18(3):175-187
Throughout the aerial radiometric reconnaissance survey portion of the U.S. Department of Energy's National Uranium Resource Evaluation (NURE) program, the identification of outliers (anomalies) was an important approach to locating regions with radio-element concentrations that are either higher or lower than expected. The method introduced herein to locate such regions involves three steps: selection of a high (or low) threshold for the variate of interest; use of the sample percentile to identify all points of interest; and movement of a window over the selected data to locate significant clusters of observations. These steps, applied to aerial radiometric 214Bi (equivalent uranium) data collected over the Copper Mountain area in Wyoming, resulted in the identification of areas enriched in that variate. 相似文献
405.
Potential of High-Resolution Satellite Data in the Context of Vulnerability of Buildings 总被引:1,自引:2,他引:1
High-resolution space-borne remote sensing data are investigated for their potential to extract relevant parameters for a
vulnerability analysis of buildings in European countries. For an evaluation of large earthquake scenarios, the number of
parameters in models for vulnerability is reduced to a minimum of relevant information such as the type of building (age,
material, number of storeys) and the geological and spatial context. Building-related parameters can be derived from remote
sensing data either directly (e.g. height) or indirectly based on the recognition of the urban structure type in which the
buildings are located. With the potential of a fully- or semi-automatic inventory of the buildings and their parameters, high-resolution
satellite data and techniques for their processing are a useful supporting tool for the assessment of vulnerability. 相似文献
406.
Ewald Lüschen Daniela Borrini Helmut Gebrande Bernd Lammerer Karl Millahn Franz Neubauer Rinaldo Nicolich TRANSALP Working Group 《Tectonophysics》2006,414(1-4):9
The TRANSALP consortium, comprising institutions from Italy, Austria and Germany, carried out deep seismic reflection measurements in the Eastern Alps between Munich and Venice in 1998, 1999 and 2001. In order to complement each other in resolution and depth range, the Vibroseis technique was combined with simultaneous explosive source measurements. Additionally, passive cross-line recording provided three-dimensional control and alternative north–south sections. Profits were obtained by the combination of the three methods in sectors or depths where one method alone was less successful.The TRANSALP sections clearly image a thin-skinned wedge of tectonic nappes at the northern Alpine front zone, unexpected graben or half-graben structures within the European basement, and, thick-skinned back-thrusting in the southern frontal zone beneath the Dolomite Mountains. A bi-vergent structure at crustal scale is directed from the Alpine axis to the external parts. The Tauern Window obviously forms the hanging wall ramp anticline above a southward dipping, deep reaching reflection pattern interpreted as a tectonic ramp along which the Penninic units of the Tauern Window have been up-thrusted.The upper crystalline crust appears generally transparent. The lower crust in the European domain is characterized by a 6–7 km thick laminated structure. On the Adriatic side the lower crust displays a much thicker or twofold reflective pattern. The crustal root at about 55 km depth is shifted around 50 km to the south with respect to the main Alpine crest. 相似文献
407.
Georg Houben Nadege Niard Torge Tünnermeier Thomas Himmelsbach 《Hydrogeology Journal》2009,17(3):665-677
Shallow groundwater represents the main source for water supply in Kabul, Afghanistan. Detailed information on the hydrogeology of the Kabul Basin is therefore needed to improve the current supply situation and to develop a sustainable framework for future groundwater use. The basin is situated at the intersection of three major fault systems of partially translational and extensional character. It comprises three interconnected aquifers, 20–70 m thick, consisting of coarse sandy to gravely detritus originating from the surrounding mountains. The aquifers were deposited by three rivers flowing through the basin. The coarse aquifer material implies a high permeability. Deeper parts are affected by cementation of pore spaces, resulting in formation of semi-diagenetic conglomerates, causing decreased well yields. Usually the aquifers are covered by low-permeability loess which acts as an important protection layer. The main groundwater recharge occurs after the snowmelt from direct infiltration from the rivers. The steadily rising population is estimated to consume 30–40 million m3 groundwater per year which is contrasted by an estimated recharge of 20–45 million m3/a in wet years. The 2000–2005 drought has prevented significant recharge resulting in intense overexploitation indicated by falling groundwater levels. 相似文献
408.
Hubert Engelbrecht Karl B. Föllmi Ursula Baumer Johann Koller 《Swiss Journal of Geoscience》2010,103(1):3-13
A resin nodule was found in glauconite-rich detrital sediments of the Cretaceous Garschella Formation (Aptian to Albian) outcropping at Langer Köchel (Bavaria, S Germany). Gas chromatographic and mass spectrometric analyses of the fossil resin revealed dealkylation and the total defunctionalisation of its polycyclic constituents. Besides many unspecific components a specific one, agathalene, has survived. Agathalene also presents a strongly degraded product, but may have been derived from its natural precursor agathic acid, which is a very specific constituent (biomarker) of recent and fossil kauri resin. Although agathalene is a far less specific secondary biomarker, it indicates the botanic origin of the fossil resin nodule. Besides other potential producers of agathic acid, precursors of the present-day conifer species Agathis dammara and A. australis were distributed in a wider palaeophytogeographic range than today and might have been the botanical source of kauri resin. In view of the east–west directed Early Cretaceous surface current system of the Tethys ocean, the palaeogeographic provenance of the Werdenfels resin nodule probably was a mainland positioned further to the east or southeast of the Helvetic shelf, to where it was transported probably by driftwood of the resin-producing Agathis sp. 相似文献
409.
Mechanism and geochemical implications of the Late Holocene organic carbon burial event: an example from the southwest coast of India 总被引:1,自引:0,他引:1
B. Ajaykumar Mahesh Mohan M. S. Shylesh Chandran K. K. Jayasooryan K. S. Unni A. P. Thomas 《Environmental Earth Sciences》2010,59(7):1409-1416
Carbonaceous clay found in the palaeo-deposits of Meenachil River basin was analysed for the total organic carbon, nitrogen
and textural characters. Radiocarbon dating of this clay formation and the embedded carbonized wood fragments was also done.
The values obtained for the organic carbon, nitrogen and C/N ratio of the carbonaceous clay exhibited a very remarkable range,
suggestive of different environmental conditions of formation. It is evident from the present study that since the lignin
and cellulose are the dominant components of terrestrial higher plants, allochthonous and submerged organic matter have high
C/N ratio. The radio carbon dating of the sediment and wood samples suggested that the palaeo-deposits of Meenachil River
basin were formed as result of many transgrassive–regressive episodes, which had started even before the formation of Vembanad
Lake. The formation of carbonaceous clay, as found sandwiched in palaeo-deposits, was due to the global eustatic sea-level
fluctuations and tectonism. 相似文献
410.
By the example of the Orlovka massif of Li-F granites in Eastern Transbaikalia, the major- and trace-element (Li, Be, B, Ta,
Nb, W, REE, Y, Zr, and Hf) compositions of the parental melt and the character of its variations during the formation of the
differentiated rock series were quantitatively estimated for the first time on the basis of electron and ion microprobe analysis
and Raman spectroscopy of rehomogenized glasses of melt inclusions in quartz. It was shown that the composition of the Orlovka
melt corresponded to a strongly evolved alumina-saturated granitoid magma (A/CNK = 1.12–1.55) rich in normative albite, poor
in normative quartz, and similar to ongonite melts. This magma was strongly enriched in water (up to 9.9 ± 1.1 wt %) and fluorine
(up to 2.8 wt %). Most importantly, this massif provided the first evidence for high B2O3 contents in melts (up to 2.09 wt %). The highest contents of trace elements were observed in the melt from pegmatoid bodies
in the amazonite granites of the border zone: up to 5077 ppm Li, 6397 ppm Rb, 313 ppm Cs, 62 ppm Ta, 116 ppm Nb, and 62 ppm
W. Compared with the daughter rock, the Orlovka melt was depleted at all stages of formation in SiO2 (by up to 6 wt %), Na2O (by up to 2.5 wt %), and, to a smaller extent, in Ti, Fe, Mg, Sr, and Ba, but was enriched in Mn, Rb, F, B, and H2O. 相似文献