共查询到20条相似文献，搜索用时 109 毫秒
1.
Self-diffusion of oxygen in a natural phlogopite mica (annite 4%) has been measured under hydrothermal conditions at 2000 bars pressure and from 500 to 800°C using water enriched in18O. Diffusional transport is dominantly parallel to the c crystallographic axis. A linear Arrhenius plot was obtained with a pre-exponential term = (1.03 ± 0.38) × 10?9cm2sec?1 a and an activation energy of 29 ± 2kcal/g-atom O. The difference in transport rate between oxygens in the OH groups and those in tetrahedral sites is small to non-existent unless the OH oxygens diffuse much more slowly than the other oxygens, which we consider unlikely. A typical phlogopite crystal, 0.2 mm thick by 1 mm across will lose radiogenic argon faster than it will exchange oxygen at temperatures above 435°C, but the reverse holds at lower temperatures if the diffusion mechanism can be extrapolated to temperatures below 500°C. Such a crystal will lose only 5% of its argon if held at 380°C for 1 m.y., but could exchange 27% of its oxygen in that time. The rate at which phlogopite will undergo deformation by diffusional creep does not appear to be controlled by oxygen diffusion. 相似文献
2.
S. A. K. Nasar 《洁净——土壤、空气、水》1980,8(6):569-581
A one year study from October 1972 to September 1973 in four freshwater fishponds of Bhagalpur (87° 02' E long, and 25° 15'N lat.), India, has shown that a high phytoplankton primary production occurred twice during the annual cycle. There were seasonal variations in the production rate with a great fluctuation in the maximum and minimum values (3 … 4 times). Amongst the ponds studied, the highest daily production recorded was 6.93 g C/m2/day in Pond I and the minimum was 0.82 g C/m2/day in Pond II. The highest annual gross production was estimated to be 1611.98 g C/m2/y in Pond I, next in the order was 1543 g C/m2/y in Pond IV and then 1155.7.5 g C/m2/y in Pond I and the minimum was 641.75 C/m2/y in Pond II. It has also been observed that in certain months the net:gross ratio recorded was zero, while the community respiration as percentage of the gross production value reached 100% in few months. A comparison has been made in the annual production of temperate and tropical freshwater systems and this indicates that tropical waters are more productive than the temperate waters. Various physico-chemical factors such as rainfall, light, temperature and alkalinity may regulate or limit production. 相似文献
3.
Petroleum Hydrocarbon Bioventing Kinetics Determined in Soil Core, Microcosm, and Tubing Cluster Studies 总被引：2，自引：0，他引：2
Ellen E. Moyer David W. Ostendorf Robin J. Richards Steve Goodwin 《Ground Water Monitoring & Remediation》1996,16(1):141-153
Aerobic biodegradation of vapor-phase petroleum hydrocarbons was evaluated in an intact soil core from the site of an aviation gasoline release. An unsaturated zone soil core was subjected to a flow of nitrogen gas, oxygen, water vapor, and vapor-phase hydrocarbons in a configuration analogous to a biofilter or an in situ bioventing or sparging situation. The vertical profiles of vapor-phase hydrocarbon concentration in the soil core were determined by gas chromatography of vapor samples. Biodegradation reduced low influent hydrocarbon concentrations by 45 to 92 percent over a 0.6-m interval of an intact soil core. The estimated total hydrocarbon concentration was reduced by 75 percent from 26 to 7 parts per million. Steady-state concentrations were input to a simple analytical model balancing advection and first-order biodegradation of hydrocarbons. First-order rate constants for the major hydrocarbon compounds were used to calibrate the model to the concentration profiles. Rate constants for the seven individual hydrocarbon compounds varied by a factor of 4. Compounds with lower molecular weights, fewer methyl groups, and no quaternary carbons tended to have higher rate constants. The first-order rate constants were consistent with kinetic parameters determined from both microcosm and tubing cluster studies at the field site. 相似文献
4.
Shekhar B. Jadhav Snehal M. Yedurkar Swapnil S. Phugare Jyoti P. Jadhav 《洁净——土壤、空气、水》2012,40(5):551-558
Acid violet 19 (AV) belongs to the triphenylmethane (TPM) class of dyes which are potentially mutagenic or carcinogenic. However, very little studies on biodegradation of AV were reported as compared to other TPM dyes such as malachite green and crystal violet. In this study, AV was decolorized up to 98% within 30 min by Pseudomonas aeruginosa BCH. The decolorization depends on the initial dye concentration, pH, and temperature. However, the dye was decolorized under wide pH and temperature ranges with an optimum of pH 7 and 30°C. Up to 250 mg L?1 of dye was found to be tolerated and decolorized by this strain. It showed decolorization ability for seven repeated dye addition cycles. The effect of additional carbon sources on dye decolorization was studied in which mannitol containing medium showed decolorization in 15 min. Induction in the enzyme activities of laccase, NADH‐DCIP reductase, and veratryl alcohol oxidase (VAO) indicates their involvement in AV degradation. Various analytical studies viz. UV–VIS, HPTLC, HPLC, and FTIR confirmed the biodegradation of AV by the bacterium. Based on GC‐MS analysis, a possible degradation pathway for AV was proposed. The phytotoxicity studies using Phaseolus mungo and Sorghum vulgare revealed the less toxic nature of metabolites formed after AV degradation. 相似文献
5.
利用分形方法对微观尺度下矿物微观组构及变化进行研究是目前的热点.本文以个旧芦塘坝矿段不同高度的硫化物矿石中广泛发育的黄铜矿为研究对象.建立起微观条件下的黄铜矿矿物的面积-周长(P-A)分形模型,并研究黄铜矿矿物的大小、不均匀性及空间分布特征.探讨黄铜矿这一标志性矿物在不同高度中的变化情况.结果显示随着深度从1758 m... 相似文献
6.
浙江大桥坞矿床是赣杭火山岩铀成矿带重要的铀矿床之一。本文通过对大桥坞铀矿床铅、氢和氧同位素及前人资料的综合研究,探讨了矿床成矿流体和成矿物质来源。结果表明花岗斑岩、凝灰岩、辉绿岩、矿石中黄铁矿、蚀变围岩中黄铁矿的Ph同位素组成变化较小,可能指示它们具有相似的源区。在铅同位素构造环境判别图解中,铅同位素投影点分布范围较广,但多数集中于地幔和造山带演化线之间,偏向造山带,反映了铅的来源与岩浆活动有关。氢、氧同位素组成显示,成矿流体主要来自大气降水。成矿物质来源于壳幔混合源。 相似文献
7.
The dual frequency SCINDA NovAtel GSV 4004B GPS receiver installed at the Ile-Ife (low-latitude station) has been in operation since December 2009. Data records for the year 2010 were processed to obtain Total Electron Content (TEC) and S 4 index. These were interpreted to analyze the ionospheric condition during low geomagnetic activity period (when Dst is from ?40 to 0 nT) and during geomagnetic storm events (with Dst about ?100 nT). Seasonal variations of the TEC and S 4 index were also investigated. The occurrence of scintillations is closely linked to the peak value of TEC during the daytime; this is very evident during the equinox months when TEC ≥ 30 TECu. When the maximum TEC value is below 30 TECu, as shown by most of the days in the summer months, the scintillation phenomenon does not occur. During geomagnetic storms, the daytime segment of the TEC plot experiences fluctuations (even bifurcations) in values with the peak TEC value of about 40 TECu. From the interpreted data, the occurrence of geomagnetic storm does not necessarily suggest an increase in the level of scintillations at a low-latitude region. Also, there is a remarkable difference between the IRI 2007 model and the observed TEC values, as the daytime TEC peak differs in magnitude and time of occurrence from the observed TEC. 相似文献
8.
9.
A limnological study was carried out in the subtropical Lake Sattal (Kumaun Himalaya) during 1979. The lake was thermally stratified during warm months and a low percentage saturation of dissolved oxygen occurred in the bottom waters. Two maxima of phytoplankton occurred in the Eastern basin in contrast to only one in the Western basin. The peak in the latter developed more than a month (October) after the second peak in the former (August). Bacillariophyceae contributed highest in the Western basin (43.2%) whereas the Dinophyceae had the least share in the Eastern basin (8.0%). Most of the dominant phytoplankters were: Synedra ulna, Fragilaria, Gymnodinium, Crucigenia and Closteridium siamensis. Interestingly, blue-green alga Nostoc, dominated for some time in autumn. A total of 12 genera of rotifers, 6 genera of cladocerans and 1 genus of copepods were found in Lake Sattal basins. Dominant zooplankters included Keratella, Cyclops, Anuraeopsis, Polyarthra and Trichocerca, and there is a high ratio of rotifers to copepods and cladocerans. On comparing the averaged values of both the basins, the Eastern basin showed a 64% larger population of zooplankton than the Western basin. A comparison is made with the plankton of the other subtropical lake-systems of this region. 相似文献
10.
本文对国际、国内在地壳上地幔介质各向异性研究领域的发展历史及研究现状进行了简单回顾,交待了宁夏地区的构造环境,阐述了本文所采用的上地幔各向异性分析方法的原理,介绍了地壳各向异性产生的机理并选择了适当的分析方法,首次系统得到了较好的宁夏地区地壳上地幔各向异性测量参数,并进行了解释。 相似文献
11.
Geoelectromagnetic Exploration For Natural Resources: Models, Case Studies And Challenges 总被引：6，自引：1，他引：6
Maxwell A. Meju 《Surveys in Geophysics》2002,23(2-3):133-206
This paper presents a tutorial review of electrical and electromagnetic(herein collectively called geoelectromagnetic) methods as applied in the search for natural resources. First, the paper discusses the technical problems and advances in geoelectromagnetic methods in the last decade. A scheme for integrating electrical and electromagnetic depth sounding data is suggested.Then, for natural resources exploration, it focuses on three themes: (1) understandinggeological models of resource targets, their physical properties, and the development of conceptual geoelectromagnetic exploration models, (2) overview of geoelectromagnetic case studies in resourceexploration, and (3) outstanding challenges in exploration. For brevity, model development is restricted to groundwater, geothermal and hydrocarbon resources, metallic ore-bodies (exemplified byvolcanogenic massive sulphides, porphyry coppers, and epithermal and Archaean greenstone belt gold deposits) and diamonds. In the treatment of resource exploration in this paper, the unifying themeis that geochemical processes of weathering and hydrothermal alteration form clayey products that may render natural resource targets directly or indirectly detectable by their resistivity characteristics.Since hydrated clays are an important feature of most resource types and are major causes of low resistivity anomalies in geoelectromagnetic exploration, they may be taken as providing detectable marker horizons or pathfinders and a basis for developing a consistent investigative approachfor natural resources. However, it is recognised that no single resource model or standard approach may be universally applicable. Natural resource systems are inherently 3D and require large numbers of depth soundings at high station densities to image adequately. Thus, developing methodsof increasing the productivity of data acquisition, the development of better 3D software tools and lowering costs are seen as the major challenges facing the use of geoelectromagnetic methods for naturalresource exploration. 相似文献
12.
—?Induced microseismicity data from a large volume fluid injection into sedimentary rock was analyzed to study the fracture system, fluid pathways, and state of stress in the lower Frio formation in east Texas. Seismicity data are from two arrays of 25 3-component geophone packages sited in two monitoring boreholes. From a total of 2,894 event triggers, a subset of 54 microearthquakes was chosen for their high quality seismograms and clear P and S arrivals. Arrival times were picked with a precision of 0.5 to 1.0?ms, and microearthquakes were located with hypocentral uncertainties estimated as less than 10–20?m. Hypocenters farthest from the injection well define a nearly horizontal tube of seismicity approximately aligned in the direction of the injection well. A simultaneous inversion of arrival times for transverse isotropic velocity structure and hypocenters yielded P-wave anisotropy of ?14% and S-wave anisotropy of ?2%. Thus, velocities along vertical ray paths are higher than those along horizontal paths, probably because of lithologic differences. Single-event focal mechanisms were determined for 47 events, and many of them are normal fault type. The minimum principal stress derived from the focal mechanisms is nearly horizontal and trends approximately north-south, consistent with the regional stress state. An imaging analysis of the seismograms shows the presence of strong seismic scatterers at positions that correlate with boundaries seen in the hypocenters; both features probably result from a similar set of heterogeneities. This study demonstrates the abundance of information that can be extracted from induced seismicity data and underscores the value of induced seismicity monitoring for studying the fluid and fracture systems created by fluid injections. 相似文献
13.
14.
湖北武湖日本沼虾的生长特性 总被引：13，自引：0，他引：13
从1998年9月至1999年9月对人工养殖湖泊——武湖日本沼虾生长特性作了研究. 以月龄来研究日本沼虾的生长,研究结果表明日本沼虾在7-1月份(1-7月龄)呈等速生长,在2-6月份(8-12月龄)呈异速生长.日本沼虾体重(W)与体长(L)呈幂函数相关,但在7-1月份时其b值接近于3,而在2-6月份时其b值明显小于3,其关系式如下: 1-7月龄:W♂=0. 0148L3. 2419(r=0. 9978,n=390),W♀=0. 0206L3. 0117(r=0. 9968,n=372); 8-12月龄:W♂=0. 0857L2. 1788(r=0.9854,n=188),W♀=0. 1450L1. 8165(r=0. 9974,n=278). 1-7月龄雄虾的生长规律符合Von Bertalanffy方程,雌虾的生长规律符合Logistic方程;8-12月龄雌雄虾的生长规律都符合Logistic方程. 相似文献
15.
The 2.5-D gravity-magnetic models of the upper crustal structures of Sahl El Qaa Area, Southwestern Sinai were constructed along seven profiles, focusing on the uppermost crustal layers to a depth of 4–5 km. In addition separation filtering process; spectral analysis and trend analysis were used to investigate the Bouguer and total intensity aeromagnetic field maps qualitatively and quantitatively. The study showed that the regional structures consist of tilted blocks in the form of a major NW-synclinal feature with an axis dipping northward. This feature is dissected by the NE trending cross faults forming horsts, grabens and step-fault structures. The tilted blocks are controlled by a major normal fault system and are greatly modified in the dip regime from north to south. They show a regional NW dip regime in northern and southern parts, where the depth to the basement reaches about 2–3 km in the down dip. In the central portion, the basin is dipping steeply to the east, with maximum depths attaining about 4–5 km. 相似文献
16.
太湖梅梁湾水动力及相关过程的研究 总被引：56，自引：13，他引：43
太湖是位于长江下游的一个大型水湖泊,水动力过程和要素对浅水湖泊的环境演化有着复杂和深远的影响,本文基于１９９８年开展的有关太湖梅梁湾的水动力过程的野外调查结果,总结了梅梁湾在夏季盛行风向条件下湖流特征,发现了梅梁湾在夏季偏南风条件下,表层湖流以顺时针环流为主要特征,但在湾内靠近梁溪河口地区,流场受地形影响而有所不同,反映在叶绿素浓度和总磷、总氮浓度分布上,因受湖流影响较大而富集在梁溪河口周转,即偏 相似文献
17.
18.
M. A. H. Saad 《洁净——土壤、空气、水》1978,6(6):529-539
Some physical and chemical investigations of the lower reaches of Tigris and Euphrates as well as the upper reaches of Shatt al-Arab in Iraq were studied. The transparency showed local and seasonal variations. The Secchi values were markedly low due to the relative turbidity of Tigris and the maximum Secchi-disc values observed coincide with more sedimentation in Euphrates. The lowest Secchi values registered in April are attributed to the considerable increase in the amounts of suspended matter carried by the floods of the rivers. The slight decrease of water temperature with depth is related to the mixing processes. Considerable seasonal variations of air and water temperatures were observed. The lowest temperatures were recorded in January (winter) and the highest in August (summer). The temperatures gave considerably high values in April and October, since the region studied lies within an arid climate. Seasonal variations of pH were recorded and attributed to physical and biological changes in the region studied. The relatively high average pH values found in August and October give a good evidence for the phytoplankton abundance under better environmental conditions. The increase of the chlorosity content at the stations A, B, II and IV is mainly due to the effect of the brackish water from Hor Hammar on these localities. The dissolved oxygen showed remarkable seasonal variations and gave the highest average values in January and the lowest in August. It was concluded that the source of dissolved oxygen in the region studied is more related to the atmosphere than the photosynthetic activity, and the mixing processes as well as the water temperatures are the main factors affecting its concentration and distribution. The results obtained show strongly that the water characteristics at the stations I, II and III were different. This is a clear evidence that Tigris joins Euphrates at Qurna forming Shatt al-Arab. 相似文献
19.
20.
在国外前苏联学者尼可拉也夫曾提及地震后有的河流形成地震坝,其后再超覆沉积细粒物质,并称为"地震沉积相",显然这是指的地震堵塞湖形成后的沉积.国内最著名的地震堰塞湖是1933年四川省茂汶北的迭溪7.5级地震,这次强震不仅使迭溪全城及周围60余城镇、村寨全部毁灭,并且四山普遍崩溃,迭溪台地大规模崩塌、堵塞岷江,形成四个地震堵塞湖.大震后45天湖水溃决,造成下游水灾.类似这种地震堵塞湖是地震导致山地,丘陵或台地崩塌堵塞溪流,是地震导致的重力作用堵塞,应为地震重力堰塞湖.本文论及的地震堰塞湖即前港湖、龙湖、虺湖、丙州西侧小湖位于福建省晋江市龙湖镇西南侧,处晋江半岛中部,4个湖沿着控制深沪湾地堑北西边缘的衙口-丙洲断裂呈NE60°线状展布.该断裂与其东侧的深沪-金井断裂共同构成了全新世深沪湾地堑,卫星照片中有清晰的显示.这两条断裂及其所夹的活动地堑同属于区域性的常乐-诏安断裂带中段部份. 相似文献