重金属对海洋围隔生态系中初级生产力的影响   总被引：1，自引：1，他引：1       下载免费PDF全文

陈其焕  吴省三  庄亮钟  H.杜微 《海洋学报》1988,10(2):222-227

1985年4月,中国和加拿大科学家首次在厦门合作进行添加重金属(Cu,Hg,Zn,Pb,Cd)的围隔生态系实验,实验是在海边大水池内的塑料袋中进行,实验结果说明低水平(ppb)混合重金属对浮游植物的影响首先表现在对光合作用速率的抑制作用,以及在浓度较低的情况下可能引起的种群演替现象,本文还阐述了颗粒有机碳(POC)和颗粒有机氮(PON)与初级生产力的相关性.  相似文献   

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  

Gyllenhammar A  Håkanson L 《Marine environmental research》2005,60(2):211-243

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   

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  

王永锋  章军锋  金振民  H.W.Green 《矿物岩石地球化学通报》2008,27(Z1)

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   

Detection of a new interstellar molecular ion, H2COH+ (protonated formaldehyde)     

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   

A photochemical model of the martian atmosphere     

Nair H  Allen M  Anbar AD  Yung YL  Clancy RT 《Icarus》1994,111(1):124-150

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   

Evidence of ancient life at 207 m depth in a granitic aquifer     

Pedersen K  Ekendahl S  Tullborg EL  Furnes H  Thorseth I  Tumyr O 《Geology》1997,25(9):827-830

The results of electron-microscopy investigations of calcite precipitated in a water-conducting fracture in a ca. 1800 Ma granitic rock from 207 m below sea level at the island of Aspo on the southeastern (Baltic) coast of Sweden are compared with measurements of carbon, oxygen, and sulfur isotope composition of the calcite and embedded pyrite. Parts of the calcite had extremely low delta 13C values, indicative of biological activity, and contained bacteria-like microfossils occurring in colonies and as typical biofllms. X-ray microanalysis demonstrated these fossils to be enriched in carbon. Our results provide evidence for ancient life in deep granitic rock aquifers and suggest that the modern microbial life found there is intrinsic. Modeling historical and present geochemical processes in deep granitic aquifers should, therefore, preferably include biologically catalyzed reactions. The results also suggest that the search for life on other planets, e.g., Mars, should include subsurface material.  相似文献   

中国三个大地震的震源参数及讨论   总被引：1，自引：0，他引：1       下载免费PDF全文

卓钰如 Kanam.  H 《地球物理学报》1990,33(4):489-496

大地震的震源机制及地震矩、应力降等参数,不(又对认识地震的破裂过程,而且对预报强地面运动都是非常重要的。一些文章对板内地震应力降的特点、地震矩与高频源谱的关系及区域特征的讨论,使我们可直接由长周期体波或面波得出的地震矩M₀估计出不同地区中大地震的高频源谱,以供强地面运动预报参考。 由于对发生在中国板内的1976年11月6日盐源地震（M_s=6.5）和1976年11月15日宁河地震（M_s=6.3）的震源参数还没有详尽的报道;另外,对1973年7月14日  相似文献   

IGU special issue on population redistribution in Asia and the Pacific region     

Clarke JI  Kawabe H 《Population geography : a journal of the Association of Population Geographers of India》1981,3(1-2):1-120

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Dynamic analysis of city size distribution: a case study of Niigata Prefecture in Japan     

Kohsaka H 《Chirigaku hyōron》1978,51(3):223-234

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Improved reliability in the interpretation of geochemical measurements by the quantification of uncertainty from sampling     

Michael H. Ramsey Paul D. Taylor Katy A. Boon 《中国地球化学学报》2006,25(B08):209-210

All geochemical measurements require the taking of field samples, but the uncertainty that this process causes is often ignored when assessing the reliability of the interpretation, of the geochemistry or the health implications. Recently devised methods for the estimation, optimisation and reduction of this uncertainty have been evaluated by their application to the investigation of contaminated land. Uncertainty of measurement caused by primary sampling has been estimated for a range of six different contaminated land site investigations, using an increasingly recognized procedure. These site investigations were selected to reflect a wide range of different sizes, contaminants （organic and metals）, previous land uses （e.g. tin mining, railway sidings and gas works）, intended future use （housing to nature reserves） and routinely applied sampling methods. The results showed that the uncertainty on measurements was substantial, ranging from 25% to 186% of the concentration values at the different sites. Sampling was identified as the dominant source of the uncertainty （〉70% of measurement uncertainty） in most cases. The fitness-for-purpose of the measurements was judged using the optimized contaminated land investigation （OCLI） method. This identifies the optimal level of uncertainty that reduces to overall financial loss caused by the measurement procedures and the misclassification of the contamination, caused by the uncertainty. Generally the uncertainty of the actual measurements made in these different site investigations was found to be sub-optimal, and too large by a factor of approximately two. The uncertainty is usually limited by the sampling, but this can be reduced by increasing the sample mass by a factor of 4 （predicted by sampling theory）. It is concluded that knowing the value of the uncertainty enables the interpretation to be made more reliable, and that sampling is the main factor limiting most investigations. This new approach quantifies this problem for the first time, and allows sampling procedures to be critically evaluated, and modified, to improve the reliability of the geochemical assessment.  相似文献