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21.
太平洋西南部铁锰矿化的矿物学特征A.H.Kan等在对克马德克和新赫布里底岛弧—海沟构造系不同地貌构造的地质采样过程中(1990年科学考察船“AHecMHoB院士”号第17航次),在一系列测站上采集到不同的铁锰形成物(MO)。详细研究这些形成物具有特殊... 相似文献
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Environmental consequence analyses of fish farm emissions related to different scales and exemplified by data from the Baltic--a review 总被引:3,自引:0,他引:3
The aim of this work is to review studies to evaluate how emissions from fish cage farms cause eutrophication effects in marine environments. The focus is on four different scales: (i) the conditions at the site of the farm, (ii) the local scale related to the coastal area where the farm is situated, (iii) the regional scale encompassing many coastal areas and (iv) the international scale including several regional coastal areas. The aim is to evaluate the role of nutrient emissions from fish farms in a general way, but all selected examples come from the Baltic Sea. An important part of this evaluation concerns the method to define the boundaries of a given coastal area. If this is done arbitrarily, one would obtain arbitrary results in the environmental consequence analysis. In this work, the boundary lines between the coast and the sea are drawn using GIS methods (geographical information systems) according to the topographical bottleneck method, which opens a way to determine many fundamental characteristics in the context of mass balance calculations. In mass balance modelling, the fluxes from the fish farm should be compared to other fluxes to, within and from coastal areas. Results collected in this study show that: (1) at the smallest scale (<1 ha), the "footprint" expressing the impact areas of fish cage farm often corresponds to the size of a "football field" (50-100 m) if the annual fish production is about 50 ton, (2) at the local scale (1 ha to 100 km2), there exists a simple load diagram (effect-load-sensitivity) to relate the environmental response and effects from a specific load from a fish cage farm. This makes it possible to obtain a first estimate of the maximum allowable fish production in a specific coastal area, (3) at the regional scale (100-10,000 km2), it is possible to create negative nutrient fluxes, i.e., use fish farming as a method to reduce the nutrient loading to the sea. The breaking point is to use more than about 1.1 g wet weight regionally caught wild fish per gram feed for the cultivated fish, and (4) at the international scale (>10,000 km2) related to the Baltic Proper, the contribution from fish farms to the overall nutrient fluxes are very small. We have also given two case-studies at the local scale where the impact of the fish farm emissions are greatest and the idea is to identify coastal areas unsuitable and suitable for fish cage farms and the reasons why. It should also be stressed that the results presented here are exemplified using emissions from fish farms, but that the underlying principles to evaluate the ecosystem effects of nutrient discharges from point source emissions are valid in a wider and more general perspective. 相似文献
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太平洋西南部铁锰矿化的地球化学特征A.H等对克马德克和新赫布里底岛弧-海沟系不同地貌构造采集了海底样品(1990年科学考察船“A.H”院士号第17航次),在一系列测站上采集到不同的铁锰形成物(жMO)。在采自8个测站的38个样品分析资料的基础上研究了... 相似文献
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金秋季节,中原大地硕果累累。国家土地督察济南局张振国副督察专员一行于9月8日至10月22日在河南开展了学习贯彻落实《违反土地管理规定行为处分办法》和土地利用管理形势巡回宣讲报告活动,历时1个多月,取得了良好效果。 相似文献
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下地壳基性麻粒岩流变强度实验研究 总被引:3,自引:0,他引:3
镁铁质基性麻粒岩被认为可能是大陆下地壳的主要组成岩石[1,2],涉及当前地球动力学研究中地壳变形和高原隆升,壳幔边界的力学耦合与拆离,底侵和拆沉作用等一系列地球动力学问题阳[3,4],具有重要的地球动力学意义.大陆下地壳的流变学性质是我们深入认识这些地球深部过程的关键点之一. 相似文献
28.
Ohishi M Ishikawa SI Amano T Oka H Irvine WM Dickens JE Ziurys LM Apponi AJ 《The Astrophysical journal》1996,471(1):L61-L64
A new interstellar molecular ion, H2COH+ (protonated formaldehyde), has been detected toward Sgr B2, Orion KL, W51, and possibly in NGC 7538 and DR21(OH). Six transitions were detected in Sgr B2(M). The 1(1,0)-1(0,1) transition was detected in all sources listed above. Searches were also made toward the cold, dark clouds TMC-1 and L134N, Orion (3N, 1E), and a red giant, IRC + 10216, without success. The excitation temperatures of H2COH+ are calculated to be 60-110 K, and the column densities are on the order of 10(12)-10(14) cm-2 in Sgr B2, Orion KL, and W51. The fractional abundance of H2COH+ is on the order of 10(-11) to 10-(9), and the ratio of H2COH+ to H2CO is in the range 0.001-0.5 in these objects. The values in Orion KL seem to be consistent with the "early time" values of recent model calculations by Lee, Bettens, & Herbst, but they appear to be higher than the model values in Sgr B2 and W51 even if we take the large uncertainties of column densities of H2CO into account. We suggest production routes starting from CH3OH may play an important role in the formation of H2COH+. 相似文献
29.
皖南变质岩中的疑源类、孢粉化石组合及其地质意义 总被引:9,自引:0,他引:9
皖南变质岩区地层原被认为属江南古陆的一部分,时代定为中、晚元古代。本文根据其中所含的Asperatopsophosphaera?sp.,Trachysphaeridium sp.,Nucellosphaeridium sp.,Lophosphaeridium sp.,Leiosphaeridia sp.,Baltisphaeridium spp.,Micrhystridium spp.和scolecodonts等疑源类和其它微体化石及笔者等以前发现的Lingulacea总面貌反映的时代,判断其中部分变质地层的时代应为晚元古代—早古生代和早古生代。同时还根据Crassispora sp.,Kraeuselisporites sp.和Lueckisporites ef.virkkiae Potonie & Klaus,Triquitritessp.等孢粉化石组合面貌反映的时代,推断其中尚有一部分为晚古生代地层。因此认为本区是一个从晚元古代—早古生代开始到中生代结束的碰撞型造山带,而不是一个古陆。 相似文献
30.
The factors governing the amounts of CO, O2, and O3 in the martian atmosphere are investigated using a minimally constrained, one-dimensional photochemical model. We find that the incorporation of temperature-dependent CO2 absorption cross sections leads to an enhancement in the water photolysis rate, increasing the abundance of OH radicals to the point where the model CO abundance is smaller than observed. Good agreement between models and observations of CO, O2, O3, and the escape flux of atomic hydrogen can be achieved, using only gas-phase chemistry, by varying the recommended rate constants for the reactions CO + OH and OH + HO2 within their specified uncertainties. Similar revisions have been suggested to resolve discrepancies between models and observations of the terrestrial mesosphere. The oxygen escape flux plays a key role in the oxygen budget on Mars; as inferred from the observed atomic hydrogen escape, it is much larger than recent calculations of the exospheric escape rate for oxygen. Weathering of the surface may account for the imbalance. Quantification of the escape rates of oxygen and hydrogen from Mars is a worthwhile objective for an upcoming martian upper atmospheric mission. We also consider the possibility that HOx radicals may be catalytically destroyed on dust grains suspended in the atmosphere. Good agreement with the observed CO mixing ratio can be achieved via this mechanism, but the resulting ozone column is much higher than the observed quantity. We feel that there is no need at this time to invoke heterogeneous processes to reconcile models and observations. 相似文献