美国印地安那南部积贮煤泥的岩石学描述与氧化作用研究(英文)     

TANG Dazhen  Colin C Harvey  Nelson D Daniel 《地学前缘》1999,6(Z1):35-44

对印地安那南部Lynnville煤泥积贮地的样品进行了详细的煤岩学研究,并就煤泥的自然氧化作用进行探讨。与原煤比较,煤泥的可见矿物体积分数增加了4～5倍,由5％改变为24％,其中黄铁矿由1％变为5％。煤泥除了黄铁矿。方解石、粘土、石英等煤系煤层的原生矿物,还含有地表土壤混入物。煤泥积贮他的入口处,沉积物自然形成高出潜水面的突起,黄铁矿在此大量富集,高粘土含量的细粒成分在煤泥地的末端富集,输入带（入口150m范围内）煤泥相应具有高硫、高灰特征。作为氧化产物,少量的褐铁矿和石膏分别在镜下和通过X射线行射分析被发现。黄铁矿比有机显微组分更易氧化并经历揭铁矿化到铁质胶体出溶变化过程。石膏主要形成于煤泥输入带。相对较强的氧化作用发生在输入带的推断得到了水化学分析结果的进一步验证。尽管如此,高潜水面及滞留水有效地限制了煤泥地内氧化作用的进行。根据煤泥入注时的自然分选效应,避开输入带,可提高煤泥回收利用率。研究成果为煤炭洗选废弃物（煤泥）的回收利用与排放环境的评价监测提供了新的方法和依据。  相似文献   

Low phase angle laboratory studies of the opposition effect: search for wavelength dependence     

Robert M Nelson  William D SmytheBruce W Hapke  Amy S Hale 《Planetary and Space Science》2002,50(9):849-856

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Sedimentary evidence of prehistoric distant-source tsunamis in the Hawaiian Islands     

Seanpaul La Selle  Bruce M. Richmond  Bruce E. Jaffe  Alan R. Nelson  Frances R. Griswold  Maria E. M. Arcos  Catherine Chagué  James M. Bishop  Piero Bellanova  Haunani H. Kane  Brent D. Lunghino  Guy Gelfenbaum 《Sedimentology》2020,67(3):1249-1273

Over the past 200 years of written records, the Hawaiian Islands have experienced tens of tsunamis generated by earthquakes in the subduction zones of the Pacific ‘Ring of Fire’ (for example, Alaska–Aleutian, Kuril–Kamchatka, Chile and Japan). Mapping and dating anomalous beds of sand and silt deposited by tsunamis in low-lying areas along Pacific coasts, even those distant from subduction zones, is critical for assessing tsunami hazard throughout the Pacific basin. This study searched for evidence of tsunami inundation using stratigraphic and sedimentological analyses of potential tsunami deposits beneath present and former Hawaiian wetlands, coastal lagoons, and river floodplains. Coastal wetland sites on the islands of Hawai΄i, Maui, O΄ahu and Kaua΄i were selected based on historical tsunami runup, numerical inundation modelling, proximity to sandy source sediments, degree of historical wetland disturbance, and breadth of prior geological and archaeological investigations. Sand beds containing marine calcareous sediment within peaty and/or muddy wetland deposits on the north and north-eastern shores of Kaua΄i, O΄ahu and Hawai΄i were interpreted as tsunami deposits. At some sites, deposits of the 1946 and 1957 Aleutian tsunamis are analogues for deeper, older probable tsunami deposits. Radiocarbon-based age models date sand beds from three sites to ca 700 to 500 cal yr bp , which overlaps ages for tsunami deposits in the eastern Aleutian Islands that record a local subduction zone earthquake. The overlapping modelled ages for tsunami deposits at the study sites support a plausible correlation with an eastern Aleutian earthquake source for a large prehistoric tsunami in the Hawaiian Islands.  相似文献   

Evaluating Uncertainties in Coronal Electron Temperature and Radial Speed Measurements Using a Simulation of the Bastille Day Eruption     

Nelson Reginald  Orville St. Cyr  Joseph Davila  Lutz Rastaetter  Tibor Török 《Solar physics》2018,293(5):82

Obtaining reliable measurements of plasma parameters in the Sun’s corona remains an important challenge for solar physics. We previously presented a method for producing maps of electron temperature and speed of the solar corona using K-corona brightness measurements made through four color filters in visible light, which were tested for their accuracies using models of a structured, yet steady corona. In this article we test the same technique using a coronal model of the Bastille Day (14 July 2000) coronal mass ejection, which also contains quiet areas and streamers. We use the coronal electron density, temperature, and flow speed contained in the model to determine two K-coronal brightness ratios at (410.3, 390.0 nm) and (423.3, 398.7 nm) along more than 4000 lines of sight. Now assuming that for real observations, the only information we have for each line of sight are these two K-coronal brightness ratios, we use a spherically symmetric model of the corona that contains no structures to interpret these two ratios for electron temperature and speed. We then compare the interpreted (or measured) values for each line of sight with the true values from the model at the plane of the sky for that same line of sight to determine the magnitude of the errors. We show that the measured values closely match the true values in quiet areas. However, in locations of coronal structures, the measured values are predictably underestimated or overestimated compared to the true values, but can nevertheless be used to determine the positions of the structures with respect to the plane of the sky, in front or behind. Based on our results, we propose that future white-light coronagraphs be equipped to image the corona using four color filters in order to routinely create coronal maps of electron density, temperature, and flow speed.  相似文献   

印度板块俯冲到藏南之下的深反射证据   总被引：11，自引：1，他引：11  

赵文津  K·D·纳尔 《地球学报》1996,17(2):131-137

喜马拉雅和相邻的西藏高原，构成了地球上最大的高原和异常厚地壳的地区，是作为印度板块和亚洲板块新生代碰撞的结果，并被认作是典型的陆－陆碰撞［１．２．３．］地带。在此，我们报道了用深地震反射剖面方法进行本区地壳成像的第一个结果，试验的１００ｋｍ长剖面，布置在特提斯喜马拉雅（ＴｅｔｈｙａｎＨｉｍａｌａｙａ）最南端，且跨过了喜马拉雅山脊，接近高喜马拉雅（ＨｉｇｈＨｉｍａｌａｙａ）地带，剖面显示了在地壳中部有一强反射带。它可能代表了一个活动的道冲断裂，印度板块是沿此断裂俯冲到藏南之下；上地壳反射使人们联想到上地壳存在着大规模的叠瓦状结构；莫霍反射来自本区双倍正常地壳厚度的巨厚地壳的底部。这些结果对西藏南端地壳增厚，是由于印度大陆地壳整体俯冲到包括特提斯喜马拉雅地区地壳之下的观点，给予了实质性的支持。  相似文献   

Satellite and in situ observations of the bio-optical signatures of two mesoscale eddies in the Sargasso Sea   总被引：1，自引：0，他引：1  

D.A. Siegel  D.B. Court  D.W. Menzies  P. Peterson  S. Maritorena  N.B. Nelson 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1218

Satellite ocean-color imagery and field spectroradiometer observations are used to assess the bio-optical signatures of two mesoscale features, a cyclone C1 and an 18°-water anticyclone A4, in the Sargasso Sea. Field determinations of upper layer bio-optical properties, such as the diffuse attenuation coefficient and remote-sensing reflectance spectra, show little statistically significant variations with distance to the eddy center for either eddy. This contrasts field observations showing many-fold higher phytoplankton pigment biomass at depth (and for A4 higher primary production rates at depth) than is typical for this region. The cyclone C1 does show a significant decrease in the depth of the 1% photosynthetically available radiation (PAR) isolume with increasing distance from eddy center while the anticyclone A4 shows no coherent signal vs. distance. Vertical profiles of bio-optical properties show consistent patterns where subsurface maxima are displaced higher inside the core of the cyclone C1 than in the surrounding waters while the highest values of the diffuse attenuation coefficient at 443 nm are observed within the core of anticyclone A4. Satellite observations of near-surface bio-optical properties show signals consistent with eddy physical characteristics, although the magnitude of these variations is very small, barely detectable by typical field measurement protocols. Mean values of bio-optical properties are higher within the cyclone compared with its periphery but not for the anticyclone. For both eddies, significant inverse correlations are observed between time series of bio-optical properties and eddy center sea-level anomaly. Consistent response to wind speed is also noted: following strong wind events, bio-optical parameters are elevated inside the anticyclone and are reduced inside the cyclone. These observations demonstrate that a combination of physical processes, including vertical eddy uplift, eddy horizontal advection, and eddy-scale Ekman pumping, contribute to the bio-optical imprint of mesoscale eddies. The contributions of these forcing mechanisms change over the period of observation, illustrating the limitations of inferring eddy bio-optical dynamics from short-term, field observations. The present analyses provide insights into the potential as well as the drawbacks of bio-optical techniques for probing the biological and biogeochemical impacts of open-ocean eddies.  相似文献   

Chemical Weathering of New Pyroclastic Deposits from Mt. Merapi （Java）, Indonesia     

Dian Fiantis  Malik Nelson  Eric Van Ranst  Jusop Shamshuddin  Nikolla P. Qafoku 《山地科学学报》2009,6(3):240-254

The Java Island, Indonesia with abundant amount of pyroclastic deposits is located in the very active and dynamic Pacific Ring of Fires. Studying the geochemical weathering indices of these pyroclastic deposits is important to get a clear picture about weathering profiles on deposits resulting from the eruption of Mt. Merapi. Immediately after the first phase of the eruption （March to June 2006）, moist and leached pyroclastic deposits were collected. These pyroclastic deposits were found to be composed of volcanic glass, plagioclase feldspar in various propoitions, orthopyroxene, clinopyroxene, olivine, amphibole and titanomagnetite. The total elemental composition of the bulk samples （including trace elements and heavy metals） was determined by wet chemical methods and X-ray fluorescence （XRF） analyses. Weathering of the pyroelastic deposits was studied using various weathering indices. The Ruxton ratio, weathering index of Parker, Vought resudual index and chemical index of weathering of moist pyroclastic deposits were lower than those of the leached samples, but the alteration indices （chemical and plagioclase） were slightly higher in the moist compared to the leached pyroelastic deposits.  相似文献   

Turkey Lakes Watershed,Ontario, Canada: 40 years of interdisciplinary whole-ecosystem research     

Kara L. Webster  Jason A. Leach  Paul W. Hazlett  Robert L. Fleming  Erik J. S. Emilson  Daniel Houle  Kara H. Y. Chan  Fariborz Norouzian  Amanda S. Cole  Jason M. O'Brien  Karen E. Smokorowski  Stephanie A. Nelson  Shelagh D. Yanni 《水文研究》2021,35(4):e14109

The Turkey Lakes Watershed (TLW) study is a federal, interdepartmental study established in 1979 to investigate the effects of acid rain on terrestrial and aquatic ecosystems. The 10.5 km² watershed, located in the Eastern Temperate Mixed Forest on the Canadian Shield, has been the site of multidisciplinary studies on biogeochemical and ecological processes conducted across plot to catchment scales. The whole-ecosystem investigative approach was adopted from the outset and has allowed research to evolve from its original (and continuing) acidification focus to include investigations on the effects of climate change, forest harvesting and other forest ecosystem perturbations. The extensive scientific and support infrastructure allows for collection of a comprehensive data record essential for understanding long-term environmental trends. Data include atmospheric deposition, meteorology, stream hydrology and chemistry, soil, pore and ground water properties, understory and overstory vegetation, lake and outflow physical and chemical properties, and aquatic macroinvertebrate and fish community composition and abundance. These data have contributed to over 400 published research papers and graduate theses. The watershed has also figured prominently in many continent-wide comparisons advancing fundamental watershed theory. The knowledge gained at TLW has influenced pollutant emission and natural resource management policies provincially, nationally and internationally.  相似文献   

An analog period method for gap-filling of latent heat flux measurements     

Lucas Emilio B. Hoeltgebaum  Nelson Luís Dias  Marcelo Azevedo Costa 《水文研究》2021,35(4):e14105

Practically all records of eddy-covariance flux measurements are affected by gaps, caused by several reasons. In this work, we propose analog period (AP) methods for gap-filling, and test them for filling gaps of latent heat flux at five AmeriFlux sites. The essence of the methods is to look for periods in the record that bear a strong resemblance, in the variable to be filled, to the periods immediately before and after the gap. Similarity between periods is gauged by the coefficient of determination, and the search for similar periods and their ranking is straightforward. The methods are developed in a univariate version (that uses only the latent heat flux data series itself) and several multivariate ones, that incorporate sensible heat flux, ground heat flux and net radiation data. For each set of independent variables used for gap-filling, the methods are tested against an existing gap-filling procedure with similar data requirements. Thus, the univariate version is tested against the mean diurnal variation method, and the multivariate versions are tested against corresponding simple and multiple linear regression techniques that use energy-budget data, and in one case the evaporative fraction as well. In our tests, the proposed univariate version performs better than the mean diurnal variation method, and the multivariate versions perform better than simple/multiple linear regression methods. An often used available computer package, REddyProc, was also tested as a basis of comparison. In general, the proposed methods (in univariate and multivariate versions) and simple/multiple linear regressions performed better than REddyProc. For the datasets analysed, gap filling via the evaporative fraction method performed poorly.  相似文献   

Multi‐proxy reassessment of the paleolimnology of Lake Bonneville (western USA) as observed in the restricted Pilot Valley sub‐basin          下载免费PDF全文

S. T. Nelson  K. A. Rey 《第四纪科学杂志》2018,33(2):177-193

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