噪声HVSR法在OBS探测中的应用——以珠江口外海OBS台阵为例

噪声谱比法(horizontal-to-vertical spectral ratio, HVSR)通常用于确定沉积层的厚度, 而应用于海底地震仪(OBS)以获取海底沉积厚度的研究较少.本文将HVSR法应用于珠江口外海域OBS台阵中, 验证了该方法用于OBS探测中的可靠性.通过对珠江口外海27台OBS收集的三分量地震噪声记录进行处理, 得到了所有台站的HVSR曲线.有23台OBS的HVSR曲线可获取与沉积层厚度相关的峰值频率, 通过经验公式可以计算得到沉积层厚度.结果显示, 珠江口外海域沉积层(新生代地层)厚度范围为100~3500 m, 研究区东南部沉积层远厚于西北部, 且沉积厚度受到NEE向滨海断裂带控制.本文获得的结果与以往依靠反射地震剖面和钻井等获得的沉积层厚度结果基本一致.进一步分析发现研究区新生代地层具有多层结构, 大部分HVSR曲线在5~12 Hz存在振幅最大的波峰, 认为是与第四系厚度相关的峰值频率, 继而确定第四系厚度为20~50 m.本研究拓展了HVSR法的应用领域, 为获取海底沉积层厚度提供了一种新的可靠方法.

     

Determination of Cyanuric Acid in Swimming Pool Water and Milk by Differential Pulse Polarography

Cyanuric acid is a suspected gastrointestinal or liver toxicant in humans. Therefore, determination of trace cyanuric acid is very important, in this work a novel, sensitive, and reliable method was developed using differential pulse polarography. Optimum conditions for analytical determination were found to be at a pH of 9.5, Britton–Robinson at a reduction potential of ?105 mV. Experimental results indicate an excellent linear correlation between the peak current and the concentration in the range of cyanuric acid from 0.5 to 27.0 µM (0.06–3.5 µg mL^?1) with a correlation coefficient of 0.997. The limit of detection and limit of quantification were obtained as 0.15 and 0.5 µM (0.02–0.06 µg mL^?1), respectively. The proposed method was successfully applied to the determination of cyanuric acid in pool water and in spiked milk. Cyanuric acid level in swimming pool water was found as 2.54 ± 0.47 µg mL^?1 (19.7 ± 2.29 µM) in swimming pool water for N = 4 and 95% confidence interval. The recoveries were found to be sufficient. Also, the standard deviation of the data was low which shows high accuracy and precision of proposed differential pulse polarographic method. The influences of some other commonly found inorganic salts on the determination of cyanuric acid were also examined. Some interfering species were eliminated using complexing agents, e.g., EDTA.     

A Molecular Ring in the Liner Ngc 5218

High resolution OVRO CO 1–0 observations of the inner 30 in the LINER galaxy NGC 5218 reveal the presence of a double centrally peaked molecular concentration with extensions out to a radius of 12. The molecular mass detected is 2.4 × 10⁹ M and the gas surface density is high, 3000 M pc square in the inner 500 pc. The SFR is 2–3 M yr^–1 and the SFE is 13, which are low or moderate values for that gas surface density. We interpret the inner feature as a rotating molecular ring with a radius of 200 pc. We furthermore suggest that the LINER activity in NGC 5218 is not caused by an aging starburst, but by a buried AGN.     

Lateglacial vegetation and palaeoenvironment in W Norway,with new pollen data from the Sunnmøre region

Krüger, L. C., Paus, A., Svendsen, J. I. & Bjune, A. E. 2011: Lateglacial vegetation and palaeoenvironment in W Norway, with new pollen data from the Sunnmøre region. Boreas, 10.1111/j.1502‐3885.2011.00213.x. ISSN 0300‐9483. Two sediment sequences from Sunnmøre, northern W Norway, were pollen‐analytically studied to reconstruct the Lateglacial vegetation history and climate. The coastal Dimnamyra was deglaciated around 15.3 ka BP, whereas Løkjingsmyra, further inland, became ice‐free around 14 ka BP. The pioneer vegetation dominated by snow‐bed communities was gradually replaced by grassland and sparse heath vegetation. A pronounced peak in Poaceae around 12.9 ka BP may reflect warmer and/or drier conditions. The Younger Dryas (YD) cooling phase shows increasing snow‐bed vegetation and the local establishment of Artemisia norvegica. A subsequent vegetation closure from grassland to heath signals the Holocene warming. Birch forests were established 500–600 years after the YD–Holocene transition. This development follows the pattern of the Sunnmøre region, which is clearly different from the Empetrum dominance in the Lateglacial interstadial further south in W Norway. The Lateglacial oscillations GI‐1d (Older Dryas) and GI‐1b (Gerzensee) are hardly traceable in the north, in contrast to southern W Norway. The southern vegetation was probably closer to an ecotone and more susceptible to climate changes.     

Strike-Slip Faults and Their Control on Differential Hydrocarbon Enrichment in Carbonate Karst Reservoirs: A Case Study of Yingshan Formation on Northern Slope of Tazhong Uplift,Tarim Basin

正Objective Oil and gas are abundant in the Ordovician Yingshan Formation carbonate karst reservoirs on the northern slope of Tazhong uplift in the Tarim Basin,and have extremely complicated oil-gas-water distribution,however.The     

QUARTZ WEATHERING IN FREEZE–THAW CYCLES: EXPERIMENT AND APPLICATION TO THE EL'GYGYTGYN CRATER LAKE RECORD FOR TRACING SIBERIAN PERMAFROST HISTORY

The object of this study is to test the assumption that cryogenic weathering (here understood as in‐situ disintegration of rock under cold‐climate conditions including ice as a weathering agent) preferentially breaks up quartz grains. We apply the results of laboratory tests to a Quaternary sediment record. The combination of silt production, relative quartz enrichment in the silt fraction, and quartz grain micromorphology is traced in a multi‐100‐kyr lake sediment archive as indicator data for cryogenic weathering. Constant cryogenic weathering conditions are inferred for at least the last 220 000 years from a lake sediment core of El'gygytgyn Crater, northeast Russia. This is the longest continuous terrestrial archive currently known for the continental Arctic. Quartz enrichment in the fines evolves from seasonal freeze–thaw weathering as demonstrated in laboratory testing where over 100 freeze and thaw cycles crack quartz grains preferentially over feldspar. Microscopic grain features demonstrate that freeze–thaw cycling probably disrupts quartz grains along mineral impurities such as bubble trails, gas–liquid inclusions, or mineralogical sub‐grain boundaries. Single‐grain micromorphology (e.g. angular outlines, sharp edges, microcracks, brittle surfaces) illustrates how quartz becomes fragmented due to cryogenic cracking of the grains. The single‐grain features stemming from the weathering dynamics are preserved even after a grain is transported off site (i.e. in mobile slope material, in seasonal river run‐off, into a lake basin) and may serve as first‐order proxy data for permafrost conditions in Quaternary records.     

Geochemistry of Pliocene/Pleistocene basalts along the Central Anatolian Fault Zone (CAFZ), Turkey

Abstract

Pliocene-Pleistocene volcanism accompanied strike-slip-related transtensional deformation along the K?z?l?rmak fault segment of the Central Anatolian fault zone (CAFZ) in the west of ?ark??la (Sivas-central Turkey). These volcanic rocks are represented by alkali olivine basalts. They can be divided into four different sub-groups on the basis of their Zr, Nb, TiO₂ contents. A primitive mantle-normalized incompatible trace element diagram for four subgroups shows close similarity to typical OIB pattern. Some of the incompatible trace element ratios (Ce/Y, Zr/Nb, La/Ba, La/Nb) are also akin to OIB values. Highly fractionated REE patterns (La/Yb_N=24.7–9.2) with no Eu anomaly are the main features of the alkali basalts and are comparable to alkaline volcanism in continental rift zones. On the basis of Al₂O₃/TiO₂, Nb/Y, Zr/Y Zr/Nb ratios, the geochemical differences among four sub-groups can be explained by variable degrees of partial melting of compositionally similar mantle source. Th/Nb, Th/Y, Nb/Y ratios and the primitive mantle-normalized trace element diagram suggests significant amount of crustal involvement for most of the alkali olivine basalts erupted along the CAFZ. Rupture of the continental lithosphere by strike-slip-related transtensional deformation might have caused decompressional partial melting of the asthenospheric mantle and generating alkali olivine basalts in this region. © 2001 Éditions scientifiques et médicales Elsevier SAS.     

1980-2019年青藏高原积雪深度时空差异性分析北大核心CSCD

积雪是地表特征的重要参数,其对辐射收支、能量平衡及天气和气候变化有重要影响。利用1980-2019年被动微波遥感积雪深度资料对青藏高原积雪时空特征进行分析,在此基础上将高原划分为东部、南部、西部及中部4个区域,并分区域讨论了多时间尺度积雪的变化特征及其与气温、降水的相关关系。结果表明:不同区域积雪深度在不同时间尺度的变化特征存在差异,高原东部积雪深度累积和消融的速率比西部快,南部积雪深度累积和消融速率比中部快。季节尺度上,冬季积雪高原东部最大,中部最小;春季积雪高原东部消融速率最大,西部积雪消融较慢但积雪深度最大;夏季高原西部仍有积雪存在。年际尺度上,各区域积雪深度在1980-2019年均呈现缓慢下降趋势,但东部积雪减少不显著;高原东部积雪深度在1980-2019年呈现出增加-减少-增加-减少的变化,其余3区均呈现出减少-增加-减少-增加-减少的变化。不同区域积雪深度对气温、降水的响应不同,高原东部和中部积雪深度与气温相关性较好;各区域积雪深度与降水呈不显著的正相关关系。