共查询到20条相似文献，搜索用时 15 毫秒
1.
2008年MW7.9汶川地震导致龙门山断裂发生强烈地壳变形,同时引发的巨量同震滑坡加速了该地区的地表剥蚀和河流侵蚀.然而,目前尚缺少系统的数据定量研究滑坡物质的运移以及河流侵蚀速率随时间的演化规律,这些对理解龙门山前缘物质的再分配以及强震对活动造山带地形塑造的作用至关重要.为此,本研究在汶川地震后的6年间,对震区沱江上游3条支流湔江、石亭江、绵远河流域进行了多期次的定点现代河沙采样.通过系统测量河沙中的石英10Be浓度,并与震前已发表的数据进行对比,发现如下基本特点：（1）震后河沙10Be浓度均有明显降低,表明同震滑坡物质对河沙的稀释作用;（2）震后河流对河沙的运移量增加为震前的1.3~18.5倍,因此震后龙门山地区侵蚀速率短期显著增加;（3）初步估计得到汶川地震产生的滑坡物质被完全运移出造山带所需要的时间至少为100~4000年,接近龙门山地区强震复发周期;（4）震间和同震产生的构造变形和地表剥蚀在空间上具有互补性.考虑到地表剥蚀引起的地壳均衡反弹效应,认为类似汶川地震的强震有利于龙门山的隆升.认识震前、震时和震后的地壳变形及侵蚀过程有助于更好地理解单次强震事件对高原边界龙门山地形演化的作用. 相似文献
2.
This study proposes an efficient new cleaning procedure for measuring in situ cosmogenic 10Be in olivines and pyroxenes. This chemical routine is specially designed to decontaminate the abundant meteoric 10Be from these minerals. The method was tested on mafic minerals from basaltic flows of Mt. Etna volcano and from Hawaiian flows and moraines. A sequential dissolution test shows that 10Be concentrations decrease with the number of cleaning steps until reaching a constant value. This is a necessary condition to demonstrate the efficiency of the method in properly decontaminating samples of meteoric 10Be. Moreover, cross-calibration with cosmogenic 3He measured within the same samples yielded a sea level high-latitude production rate of 4.5±0.4 at g−1 a−1 for cosmogenic 10Be in mafic minerals. This rate is within 1σ uncertainty of empirically or model-derived rates for 10Be on the same targets. Such concordance supports the consistency of the new method. 相似文献
3.
Kazuho Horiuchi Tomoko Uchida Yuko Sakamoto Aoi Ohta Hiroyuki Matsuzaki Yasuyuki Shibata Hideaki Motoyama 《Quaternary Geochronology》2008,3(3):253-261
The cosmogenic nuclide 10Be was analyzed by using accelerator mass spectrometry on an ice core drilled at the Dome Fuji station, inland Antarctica, for 700–1900 yr CE. The measured concentration of 10Be in the Dome Fuji ice core and the derived 10Be flux show similar fluctuations, with both increasing at known solar-activity minima over the last millennium in agreement with earlier observations of 10Be and 14C. Based on the similar nature of the 10Be flux to the reconstructed 14C production rate patterns, a 10Be–14C correlation age model for the Dome Fuji ice core was successfully constructed. This age model agrees well with the initial version of the tephrochronology of the core. The 10Be-flux record contains information on variability in the amount of cosmic radiation incident on the atmosphere, which is mainly attributable to high-frequency change in solar activity and low-frequency background intensity adjustment of the geomagnetic field. High-resolution 10Be analyses of the Dome Fuji ice cores promise to provide potentially important information on the history of cosmic radiation intensity over the past several hundred thousand years. 相似文献
4.
Cosmic-ray-produced10Be (t1/2 = 1.6 × 106 years) and36Cl (t1/2 = 3.0 × 105 years) have been measured in the Apollo 15 long core for study of galactic cosmic ray production profiles using tandem accelerator mass spectrometry. From these experiments, the half-attenuation length for10Be production and36Cl production were calculated to be 120 g/cm2 and 132 g/cm2 (150–400 g/cm2 region). The measured half-attenuation length for10Be is slightly longer than that predicted by the Reedy-Arnold theoretical model. The flatter and somewhat deeper maximum seen in the36Cl profile compared to the10Be,26Al and53Mn profiles can be explained by production from secondary thermal neutrons on35Cl. 相似文献
5.
A. Matmon Y. Shaked N. Porat Y. Enzel R. Finkel N. Lifton E. Boaretto A. Agnon 《Earth and Planetary Science Letters》2005,240(3-4):803-817
In this study, we explored the spatial and temporal relations between boulders and their original in-situ locations on sandstone bedrock cliffs. This was accomplished by combining field observations with dating methods using cosmogenic isotopes (10Be and 14C) and optically stimulated luminescence (OSL). Our conclusions bear both on the landscape evolution and cliff retreat process in the hyperarid region of Timna and on the methodology of estimating exposure ages using cosmogenic isotopes.
We recognize three discrete rock fall events, at 31 ka, 15 ka, and 4 ka. In this hyperarid region, the most plausible triggering mechanism for rock fall events is strong ground acceleration caused by earthquakes generated by the nearby Dead Sea fault (DSF). Our record, however, under represents the regional earthquake record implying that ongoing development of detachment cracks prior to the triggering event might be slower than the earthquake cycle.
Cliff retreat rates calculated using the timing of rock fall events and estimated thickness of rock removed in each event range between 0.14 m ky− 1 and 2 m ky− 1. When only full cycles are considered, we derive a more realistic range of 0.4 m ky− 1 to 0.7 m ky− 1. These rates are an order of magnitude faster than the calculated rate of surface lowering in the area. We conclude that sandstone cliffs at Timna retreat through episodic rock fall events that preserve the sharp, imposing, landscape characteristic to this region and that ongoing weathering of the cliff faces is minor.
A 10%–20% difference in the 10Be concentrations in samples from matching boulder and cliff faces that have identical exposure histories and are located only a few meters apart indicates that cosmogenic nuclide production rates are sensitive to shielding and vary spatially over short distances. However, uncertainties associated with age calculations yielded boulder and matching cliff face ages that are similar within 1 σ . The use of external constraints in the form of field relations and OSL dating helped to establish each pair's age. The agreement between calculated 14C and 10Be ages indicates that the accumulation of 10Be at depth by the capture of slow deep-penetrating muons was properly accounted for in the study. 相似文献
6.
Edouard Bard Grant M. Raisbeck Franoise Yiou Jean Jouzel 《Earth and Planetary Science Letters》1997,150(3-4):453-462
For about the last 30 years it has been recognized that the high frequency component of the tree rings 14C/12C record is dominated by the modulation of the cosmic ray flux by the solar wind. In particular, it has been demonstrated that the three most recent periods of low sunspot occurrence were characterized by high values of atmospheric 14C/12C. During the last millennium other periods of high 14C/12C values were observed but their solar origin is still debatable. In the present work we compare these fluctuations with an independent record of cosmogenic 10Be measured in ice from the South Pole to check the solar origin of the observed 14C/12C variations. In order to compare quantitatively the results obtained on 10Be and 14C, it is necessary to take into account the different behaviour of these two cosmogenic isotopes, and especially the damping effect of the carbon cycle in the case of 14C. As an input to a 12-box numerical model we used the relative fluctuations of the 10Be concentrations record measured in South Pole ice and converted it into a synthetic 14C record. We took into account the fact that 10Be modulation is enhanced in polar regions due to the orientation of the geomagnetic field. As expected, the fluctuations of the modelled 14C record are much smaller (a factor of 20) than those observed for the raw 10Be record. In addition, the variations are smoother and shifted in time by a few decades. The 10Be-based 14C variations closely resemble the 14C measurements obtained on tree rings (R = 0.81). In particular, it is easy to identify periods of maximal 14C/12C which correspond to solar activity minima centred at about 1060, 1320 (Wolf), 1500 (Spörer), 1690 (Maunder) and 1820 (Dalton) yr A.D. Cross-correlation calculations suggest that there is no significant lag between the 10Be-based 14C and the tree-ring 14C records. Our study strongly suggests the dominance of the solar modulation on the cosmonuclide production variations during the last millennium. 相似文献
7.
Eric E. Small Robert S. Anderson James L. Repka Robert Finkel 《Earth and Planetary Science Letters》1997,150(3-4):413-425
We have measured the concentration of in situ produced cosmogenic 10Be and 26Al from bare bedrock surfaces on summit flats in four western U.S. mountain ranges. The maximum mean bare-bedrock erosion rate from these alpine environments is 7.6 ± 3.9 m My−1. Individual measurements vary between 2 and 19 m My−1. These erosion rates are similar to previous cosmogenic radionuclide (CRN) erosion rates measured in other environments, except for those from extremely arid regions. This indicates that bare bedrock is not weathered into transportable material more rapidly in alpine environments than in other environments, even though frost weathering should be intense in these areas. Our CRN-deduced point measurements of bedrock erosion are slower than typical basin-averaged denudation rates ( 50 m My−1). If our measured CRN erosion rates are accurate indicators of the rate at which summit flats are lowered by erosion, then relief in the mountain ranges examined here is probably increasing.
We develop a model of outcrop erosion to investigate the magnitude of errors associated with applying the steady-state erosion model to episodically eroding outcrops. Our simulations show that interpreting measurements with the steady-state erosion model can yield erosion rates which are either greater or less than the actual long-term mean erosion rate. While errors resulting from episodic erosion are potentially greater than both measurement and production rate errors for single samples, the mean value of many steady-state erosion rate measurements provides a much better estimate of the long-term erosion rate. 相似文献
8.
Study of historical earthquake is one of the important methods to understand the seismic activities and analyze the seismogenic faults. On the May 25th, 1568 AD, a destructive earthquake occurred to the northeast of the present-day city of Xi'an, Shaanxi Province. Because this earthquake happened shortly after the 1556 M8 earthquake and was regarded as an aftershock, it has received little attention in previous studies. Previous earthquake catalogue agreed in assigning a magnitude 6 3/4 to this earthquake but had different epicentral locations and seismic intensity, and the seismogenic structure remains ambiguous.
Based on textual research of historical earthquake and field investigation, the Jingyang County, Gaoling County, and Xianning County, were the worst hit area by the earthquake, and the areas, including Yongle Town, Gaozhuang Town at southeastern Jingyang County to Gaoling County and its southeastern present-day Jijia and Zhangbu, should be the mesoseismal area of this earthquake. The epicenter intensity of this earthquake is Ⅸ+(9~10 degrees), and the magnitude is estimated to be 7. The isoseismal lines were drawn to exhibit the various intensities of the areas damaged during the event, with its major axis directed NWW. Intensities reached Ⅸ+ in the zone extending west-northwest parallel to the Weinan-Jingyang Fault. This fault, characterized by a normal fault that developed during the Cenozoic extensional history of the Weihe Basin, dipping to the north at an angle of 60°~80°, is one part of the southern boundary faults in Weihe graben. There are geomorphological and geological evidences of recent activity of the fault during (180±30)a BP to (1 600±30)a BP. At T1-T2 fluvial terraces on the north bank of Weihe River, the scarps were faulted during Ming Dynasty, and sandy soil liquefaction, dense structural tensional fissures and faulted strata are noted in stratigraphic profiles and trenches. Thus, we suggest that this fault can reliably be regarded as being active during Holocene, and re-name the earthquake as the Shaanxi Gaoling earthquake. 相似文献
9.
焉耆盆地北缘和静逆断裂-褶皱带中晚第四纪变形速率 总被引：4，自引：4，他引：0
焉耆盆地为南天山内部的一个山间盆地,盆地北缘发育1排第四纪新生褶皱带,即和静逆断裂-褶皱带。中晚第四纪以来,由于和静逆断裂-褶皱带的持续活动使得在褶皱生长过程中形成的多期洪积地貌面发生反向掀斜变形。利用高精度差分GPS,对褶皱带中部哈尔莫敦背斜区内的多期变形地貌面的地形形态进行了测绘,判定背斜的生长主要以翼旋转为主。利用背斜北翼不同地貌面的反向掀斜角度,分别计算了不同期次地貌面的隆升和缩短变形量。结合原地宇宙成因核素深度剖面法和光释光测年法,对背斜区内的F4,F3b,F2洪积台地面和T1阶地面的形成年龄进行了测定,发现背斜在距今约550ka、428.3+57.6-47.2ka和354.3+34.2-34.8ka不同时段的平均隆升速率从0.31±0.24mm/a下降至0.15±0.02mm/a,同时背斜北翼的翼旋转速度也呈逐渐减小的趋势。但背斜自起始变形开始,缩短速率却大致保持恒定为约0.3mm/a。而这一恒定的缩短速率与现今横跨和静逆断裂-褶皱带所观测的GPS速率具有很好的一致性,说明在天山内部的哈尔莫敦背斜区,短尺度的GPS速率可以代表长尺度的地壳应变速率,同时反映出山体内部一系列断层和褶皱构造在吸收和调节整体变形量时也起到一定的作用。 相似文献
10.
Greg Balco John O. Stone Nathaniel A. Lifton Tibor J. Dunai 《Quaternary Geochronology》2008,3(3):174-195
We codify previously published means of calculating exposure ages and erosion rates from 10Be and 26Al concentrations in rock surfaces, and present a single complete and straightforward method that reflects currently accepted practices and is consistent with existing production rate calibration measurements. It is intended to enable geoscientists, who wish to use cosmogenic-nuclide exposure age or erosion rate measurements in their work to: (a) calculate exposure ages and erosion rates; (b) compare previously published exposure ages or erosion rate measurements on a common basis; (c) evaluate the sensitivity of their results to differences between published production rate scaling schemes. The method is available online at http://hess.ess.washington.edu. 相似文献
11.
Production of selected cosmogenic radionuclides by muons: 2. Capture of negative muons 总被引：1，自引：0，他引：1
B. Heisinger D. Lal A. J. T. Jull P. Kubik S. Ivy-Ochs K. Knie E. Nolte 《Earth and Planetary Science Letters》2002,200(3-4):357-369
We have determined the production yields for radionuclides in Al2O3, SiO2, S, Ar, K2SO4, CaCO3, Fe, Ni and Cu targets, which were irradiated with slow negative muons at the Paul Scherrer Institute in Villigen (Switzerland). The fluences of the stopped negative muons were determined by measuring the muonic X-rays. The concentrations of the long-lived and short-lived radionuclides were measured with accelerator mass spectrometry (AMS) and γ-spectroscopy, respectively. Special emphasis was put on the radionuclides 10Be, 14C and 26Al produced in quartz targets, 26Al in Al2O3 and S targets, 36Cl in K2SO4 and CaCO3 targets, and 53Mn in Fe2O3 targets. These targets were selected because they are also the naturally occurring target minerals for cosmic ray interactions in typical rocks. We also present results of calculations for depth-dependent production rates of radionuclides produced after cosmic ray μ− capture, as well as cosmic ray-induced production rates of geologically relevant radionuclides produced by the nucleonic component, by μ− capture, by fast muons and by neutron capture. 相似文献
12.
Helium and neon isotopes in the Imnaha Basalt, Columbia River Basalt Group: Evidence for a Yellowstone plume source 总被引：3，自引：0，他引：3
Allen Dodson B. Mack Kennedy Donald J. DePaolo 《Earth and Planetary Science Letters》1997,150(3-4):443-451
Helium, neon, and argon isotopic compositions were measured in two flows of the Columbia River flood basalt. The Imnaha Basalt has a 3He/4He ratio of 11.4 times atmospheric and 20Ne/22Ne and 21Ne/22Ne ratios characteristic of a plume component. The measured 3He/4He is a lower limit, due to possible preferential 3He loss and/or addition of radiogenic 4He. A Wanapum Basalt flow, erupted approximately 2 Ma later in the waning stages of volcanism, has more MORB-like noble gases. The He, Nd and Sr isotopic compositions of these lavas suggest that the Columbia River basalts were derived from the Yellowstone plume head which contained both ‘high-helium’ plume material and entrained depleted mantle. As the eruptions progressed the plume component in the melting region was gradually diluted or replaced. 相似文献
13.
Water sampling during the 1993 IV Russian–US Joint Expedition to the Bering and Chukchi Seas (BERPAC) indicates that Pacific Ocean burdens of the long-lived radionuclide 129I are relatively low in the Pacific-influenced Arctic, particularly compared to high latitude waters influenced by the North Atlantic. These low concentrations occur despite the presence of potential submerged anthropogenic sources in the East Sea (Sea of Japan), and in the northwest Pacific Ocean, east of the Kamchatka Peninsula. The concentration of 129I entering the Arctic Ocean through Bering Strait, 0.7×108 atoms kg−1, is only slightly higher than observed in deep Pacific waters. Similar concentrations (0.44–0.76×108 atoms kg−1) measured in Long Strait indicate no significant transfer of 129I eastward into the Chukchi Sea in the Siberian Coastal Current from the Siberian marginal seas to the west. However, the concentrations reported here are more than an order of magnitude higher than the Bering Strait input concentration estimated (1.0×106 atoms kg−1) from bomb fallout mass balances, which supports other existing evidence for a significant atmospheric deposition term for this radionuclide in surface ocean waters. Near-bottom water samples collected in productive waters of the Bering and Chukchi Seas also suggest that sediment regeneration may locally elevate 129I concentrations, and impact its utility as a water mass tracer. As part of this study, two deep 129I profiles were also measured in the East Sea in 1993–1994. The near-surface concentration of 129I ranged from 0.12 to 0.31×108 atoms kg−1. The 129I concentration showed a steady decrease with depth, although because of active deep water ventilation, the entire 3000 m water column exceeded natural concentrations of the radionuclide. Atom ratios of 129I/137Cs in the East Sea also suggest an excess of 129I above bomb fallout estimates, also possibly resulting from atmospheric deposition ultimately originating from nuclear facilities. 相似文献
14.
During a contamination survey in NE-Germany sediment cores were sampled at 5 locations with freeze-coring devices and conventional box-coring systems. In total more than 40 samples were analysed for several organic compounds (136 PCDD/F, 33 PCB, 39 PAH, 10 DDX, 4 HCH, 4 CB), sedimentological parameters (TOC, TC, TIC, LOI), some total trace metals (Pb, Cd, Cr, Cu, Zn) and dated by measurement of the 210Pb and 137Cs activity. The deepest segment of the cores from the Arkona Basin and the freshwater lakes were dated back to the end of the 19th century. A comparison of marine versus freshwater data is presented. The contamination levels of Arkona Basin were often lower than anthropogenically influenced freshwater sediments and more similar to a freshwater sediment core only influenced by deposition, with an additional Oder River inflow. Differences in patterns and contamination levels are discussed. 相似文献
15.
Over the last two decades, in-situ cosmogenic 14C dating has become an import tool in Quaternary geology and is recognized to geoscientists because of its potential to provide information on exposure age and process rate estimates for geomorphic studies. The in-situ cosmogenic radiocarbon has a relatively short half-life(5730 yr)and is substantially more sensitive than all the other cosmogenic nuclides used so far. It is therefore particularly useful to determine surface-exposure ages of Holocene landforms and quantify erosion rates in rapidly denuding landscapes during the past few tens of thousands of years. Moreover, in situ 14C is produced in quartz which is both highly resistant to weathering and common in nature, so it can be used in combination with other in-situ cosmogenic nuclides such as 3He, 10Be,21Ne,26Al, and 36Cl to constrain complex exposure histories involving burial and/or erosion occurring over the past 25ka.
The age and slip rate of Holocene normal fault have been undoubtedly a challenge for seismologists to be faced with as result from lack of appropriate late Quaternary sediment. Recently, the cosmogenic nuclides such as 36Cl of preserved, seismically exhumed normal fault scarps were used to identify the last few major earthquakes and recover their ages and displacements through the modeling of the content of 36Cl in the scarp rocks.
This paper mainly summarizes the development of in-situ 14C dating, including its research history, production rate estimate, production mechanism, chemical behavior and experimental method. The potential application of in-situ 14C dating to recovering past earthquakes, their timing, and the regularity of their recurrence for preserved, seismically exhumed normal fault scarps is also introduced. 相似文献
16.
Regional behaviour of the groundwater flow system in the Cochabamba Valley, Bolivia, is evaluated through the interpretation of tritium (3H) distributions in groundwater samples from wells and springs. In order to interpret groundwater 3H concentrations in Cochabamba Valley, where no historical record of 3H concentrations in rainfall exists, a reconstructed 3H precipitation record is developed. The record of 3H concentrations in precipitation is fairly extensive in the Amazon Basin and this record was extrapolated to the neighbouring Cochabamba Valley. Tritium concentrations in rainfall have been observed to increase under natural conditions with increasing latitude and with increasing distance from the ocean. By considering these trends, a linear relationship for increasing 3H concentration in precipitation is developed, based on data from the Amazon Basin, that realistically predicts regional 3H distributions from the northeast Brazilian coast to Cuzco, Peru. This 3H precipitation record is then extrapolated to the Cochabamba Valley and, after correction for radiogenic decay, is used to interpret trends in groundwater 3H concentrations within the valley.
The groundwater flow system in one of the principal alluvial fans, which serves as an important groundwater resource for the city, is studied in detail. Tritium concentrations drop from approximately 8–10 tritium units (TU) in the recharge area to concentrations below the detection limit of 0.8 TU further out in the valley. Groundwater velocities of approximately 0.3 to 0.9 m d−1 are estimated from distributions of groundwater 3H concentrations along the alluvial fan with the use of the reconstructed precipitation 3H record. Regional characteristics of the groundwater flow system are discussed with respect to future development and protection of the groundwater resources. 相似文献
17.
根据低温热年代学数据,提取岩石从深部剥露到地表的信息,对理解诸多地质问题(如造山带演化、地表过程及其相互作用等)具有重要意义.本文提出一种基于岩石温度历史(可利用古温标、热年代计等方法制约),并考虑剥露过程对地温场扰动的剥露历史反演计算方法.基于假定的与真实数据的正反演模拟和参数敏感性分析表明:热扩散率的变化对剥蚀量计算影响不大,在常规岩石热扩散率变化范围内(20～35km2/Ma),总剥蚀量变化小于10%;传统计算方法低估了剥蚀总量,对于现今地温梯度小于20℃/km、冷却速率大于2～3℃/Ma,或现今地温梯度大于30℃/km、冷却速率大于5～10℃/Ma的地区,需要考虑热平流对剥蚀量计算的影响;匀速冷却的热历史指示剥蚀速率持续减小,而非匀速剥蚀.本文将该方法应用到龙门山南段和四川盆地,反演计算显示龙门山南段15Ma以来的剥蚀总量为8km,四川盆地中部80Ma以来剥蚀总量约为3km、东部约5km. 相似文献
18.
The potentially important influence of climate change on landscape evolution and on critical zone processes is not sufficiently understood. The relative contribution of hydro-climatic factors on hillslope erosion rates may significantly vary with topography at the watershed scale. The objective of this study is to quantify the hydro-geomorphic behavior of two contrasting landscapes in response to different climate change scenarios in the Luquillo Critical Zone Observatory, a site of particular geomorphological interest, in terms of hillslope erosion and rainfall-triggered landslides. We investigate the extent to which hillslope erosion and landslide occurrence remain relatively invariant with future hydro-climatic perturbations. The adjacent Mameyes and Icacos watersheds are studied, which are underlain by contrasting lithologies. A high resolution coupled hydro-geomorphic model based on tRIBS (Triangulated Irregular Network-based Real-time Integrated Basin Simulator) is used. Observations of landslide activity and hillslope erosion are used to evaluate the model performance. The process-based model quantifies feedbacks among different hydrologic processes, landslide occurrence, and topsoil erosion and deposition. Simulations suggest that the propensity for landslide occurrence in the Luquillo Mountains is controlled by tropical storms, subsurface water flow, and by non-climatic factors, and is expected to remain significant through 2099. The Icacos watershed, which is underlain by quartz diorite, is dominated by relatively large landslides. The relative frequency of smaller landslides is higher at the Mameyes watershed, which is underlain by volcaniclastic rock. While projections of precipitation decrease at the study site may lead to moderate decline in hillslope erosion rates, the simulated erosional potential of the two diverse landscapes likely remains significant. © 2018 John Wiley & Sons, Ltd. 相似文献
19.
Impacts of domestic sewage effluent on phytoplankton from Bedford Basin, eastern Canada 总被引：2，自引：0，他引：2
The impact of domestic sewage effluent (SE) on the dynamics of phytoplankton assemblages from Bedford Basin was evaluated in the laboratory. Phytoplankton production and chlorophyll a increased proportionally with SE enrichment. Phytoplankton species composition also changed. The potentially harmful diatoms, Pseudonitzschia spp., present initially in small numbers (600 cells 1−1) in Bedford Basin seawater, and became dominant (3–5×106 cells 1−1) when the seawater was enriched with 0.5–5% untreated SE. With higher proportions of SE, other harmful species such as Fragilaria spp. and Euglena spp. became dominant (7−15×106 and 2.2×104 cells 1−1, respectively). Treatment of SE with UV light or activated charcoal seems to favour growth of benign species, such as Chaetoceros socialis, Skeletonema costatum and Thalassiosira spp., but not harmful species such as Pseudonitzschia spp. Further research on UV treatment of domestic sewage is recommended. 相似文献
20.
按照地球膨胀学说进行全球构造动力物理模拟的相似性研究，得到了膨胀地球岩石层弹性球壳力学模型的方程分析相似准则和地幔物质沿膨胀裂谷通道上涌流动的方程分析相似准则．按照各相似准则的约束，计算得到了满足与膨胀地球原型相似的模型参数：膨胀初始半径为０．４６ｍ；原始岩石层的厚度、密度分别为３×１０－３ｍ和（１．２－１．８）×１０ｋｇ／ｍ３，其强度为１０４Ｐａ；原始地球膨胀内压为４．２５×１０４Ｐａ；原始地表重力为－１．２５×１０－２Ｎ／ｋｇ；上涌物质密度、粘度分别为１．２×１０２ｋｇ／ｍ３和２×１０２Ｐａ·ｓ；原始地幔物质上涌厚度、速度和加速度分别为２．５×１０－２ｍ，２．０×１０－３ｍ／ｓ和３×１０２ｍ／s2．由此表明材料物性等条件能够较好地满足原型要求的模型条件． 相似文献