排序方式： 共有117条查询结果，搜索用时 15 毫秒
51.
地层学、火山学、岩石学和流体动力学的研究结果表明，西澳大利亚与太古宙科马提岩有关的镍硫化物矿床是由于通道化熔岩流之下固结硫化物沉积物遭受热侵蚀作用而形成的。坎博尔达地区的地球化学和Ｎｄ同位素数据表明，矿化的熔岩通道所受的混染都比该岩流的周边无矿部分要轻，这是由于通道内排泄速率高和得到连续不断的补给所致。这种解释对硫化物的定位模式、它们与主岩科马提岩的平衡程度和硫化物矿石的成分有以下几种含意：１）科 相似文献
52.
53.
Downs CA Fauth JE Robinson CE Curry R Lanzendorf B Halas JC Halas J Woodley CM 《Marine pollution bulletin》2005,51(5-7):558-569
Coral reefs within the Florida Keys are disappearing at an alarming rate. Coral cover in the Florida Keys National Marine Sanctuary declined by 38% from 1996 to 2000. In 2000, populations of Montastraea annularis at four sites near Molasses Reef within the Florida Keys National Marine Sanctuary and one reef within Biscayne National Park were sampled on a quarterly basis. Anecdotal observations showed corals at Alina's Reef in Biscayne National Park appeared healthy in March, but experienced an acute loss of coral cover by August. Cellular Diagnostic analysis indicated that Alina's Reef corals were in distress: they had been afflicted with a severe oxidative damaging and protein-denaturing stress that affected both the corals and their symbiotic zooxanthellae. This condition was associated with a significant xenobiotic detoxification response in both species, reflecting probable chemical contaminant exposure. These results demonstrate that applying a Cellular Diagnostic approach can be effective in helping to identify stress and its underlying causes, providing diagnostic and prognostic biomarkers of coral health. 相似文献
54.
NUTRIENT LOAD ESTIMATION METHODS FOR RIVERS 总被引：2，自引：0，他引：2
Huai-en LI. Joseph Hun-Wei LEE Ming CM Professor Environmental Science Institute Xi''''an University of Technology. Xi''''an . Shaanxi P.R. China.Professor Department of Civil Engineering The University of Hong Kong Pokfulam Road Hong Kong.P.R. China Ph.D. student in Hydrology Water Resources. Environmental Science Institute Xi''''an University ofTechnology Xi''''an Shaanxi P.R. China 《国际泥沙研究》2003,18(4)
Pollutant load estimation is essential for watershed management and water pollution control. For most watersheds, only sparse water quality measurements (e.g. monthly data) are available. The influence of input data on the accuracy of non-point source pollution load estimation is studied using the water quality and stream flow data from a small watershed in Hong Kong. Comparison and analysis of the results using 8 different methods show that the accuracy of stream-flow runoff is the single most important factor for the calculation of pollutant load. Based on the results, the stream flow correction coefficient is advanced to provide a more reliable load estimation. The improved method of pollutant load estimation can be easily applied in practice since the stream-flow runoff can be measured by hydrological station or estimated with various hydrological methods. 相似文献
55.
Spectroscopic analyses have shown that smectites enhanced in the laboratory with additional ferric species exhibit important similarities to those of the soils on Mars. Ferrihydrite in these chemically treated smectites has features in the visible to near-infrared region that resemble the energies and band strengths of features in reflectance spectra observed for several bright regions on Mars. New samples have been prepared with sulfate as well, because S was found by Viking to be a major component in the surface material on Mars. A suite of ferrihydrite-bearing and ferric sulfate-bearing montmorillonites, prepared with variable Fe3+ and S concentrations and variable pH conditions, has been analyzed using reflectance spectroscopy in the visible and infrared regions, M?ssbauer spectroscopy at room temperature and 4 K, differential thermal analysis, and X-ray diffraction. These analyses support the formation of ferrihydrite of variable crystallinity in the ferrihydrite-bearing montmorillonites and a combination of schwertmannite and ferrihydrite in the ferric sulfate-bearing montmorillonites. Small quantities of poorly crystalline or nanophase forms of other ferric materials may also be present in these samples. The chemical formation conditions of the ferrihydrite-bearing and ferric sulfate-bearing montmorillonites influence the character of the low temperature M?ssbauer sextets and the visible reflectance spectra. An absorption minimum is observed at 0.88-0.89 micrometers in spectra of the ferric sulfate-bearing samples, and at 0.89-0.92 micrometers in spectra of the ferrihydrate-bearing montmorillonites. M?ssbauer spectra of the ferric sulfate-bearing montmorillonites indicate variable concentrations of ferrihydrite and schwertmannite in the interlaminar spaces and along grain surfaces. Dehydration under reduced atmospheric pressure conditions induces a greater effect on the adsorbed and interlayer water in ferrihydrite-bearing montmorillonite than on the water in ferric sulfate-bearing montmorillonite. Reflectance spectra of ferric sulfate-bearing montmorillonite include a strong 3-micrometers band that is more resistant to dry atmospheric conditions than the 3-micrometers band in spectra of similarly prepared ferrihydrite-bearing montmorillonites. 相似文献
56.
de Oliveira-Costa A Tegmark M Gutiérrez CM Jones AW Davies RD Lasenby AN Rebolo R Watson RA 《The Astrophysical journal》1999,527(1):L9-L12
The recent discovery of dust-correlated diffuse microwave emission has prompted two rival explanations: free-free emission and spinning dust grains. We present new detections of this component at 10 and 15 GHz by the switched-beam Tenerife experiment. The data show a turnover in the spectrum and thereby support the spinning dust hypothesis. We also present a significant detection of synchrotron radiation at 10 GHz, which is useful for normalizing foreground contamination of cosmic microwave background experiments at high galactic latitudes. 相似文献
57.
沉积于中中新世到上新世的浊积砂体是第三纪Ｎｉｉｇａｔａ弧后盆地的主要油气储层之一,该盆地是日本列岛最富产石油的盆地。我们对这些浊积体的重矿物进行了详细和系统地分析,首先,作者展示了将重矿物分析和沉积作用分析相结合,从而得出有关沉积过程的全新观点的实例,沿着位于盆地东缘的世早期的浊积砂岩体的垂向和横向取样分析表明,砂全东半部重矿物的成分和西半部重矿物的成分不同。重矿物和沉积分析结果表明,发育在东半部的浅海陆架浊积砂岩和发育在西半部的深海水下浊积全在上新世早期是相互叠置的。其次,作者检验了用重矿物成分作为指标来表征某个特定浊积体的有效性,为此目的选重位于Ｎｉｉｇａｔａ盆地中部的许多浊积砂岩分析研究,得出以下结论。（１）基于主要重的,比如蛋白石、普通角闪石、紫苏辉石和普通辉石的定量综合分析,至少可将研究区的浊砂岩划分 相似文献
58.
This article reviews the literature involving benthic invertebrates that are cited in association with hull fouling, reporting the species that occur on the Brazilian coast and evaluating the importance of this vector for the introduction of nonindigenous and cryptogenic invertebrates in Brazil. It discusses some of the strategies that were used by the species that allowed for their overseas transport and made it easier to cross natural barriers that otherwise would have been obstacles to their dispersion. The compiled data list 343 species (65% nonindigenous and 35% cryptogenic), mainly from the northwestern Atlantic Ocean. The traveling fauna, composed mostly of cosmopolitan species (70.3%), is primarily euryhaline and marine stenohaline, with sessile and sedentary habits. After delineating the shipborne species’ ecological profiles and traveling strategies and evaluating their overlapping vectors, we concluded that hull vessels were the main vector of introduction to the Brazilian coast for 89.8% of the compiled species. 相似文献
59.
Lemkau KL Peacock EE Nelson RK Ventura GT Kovecses JL Reddy CM 《Marine pollution bulletin》2010,60(11):2123-2129
Understanding the fate of heavy fuel oils (HFOs) in the environment is critical for sound decisions regarding its usage and spill cleanup. To study weathering of HFOs, we examined the M/V CoscoBusan spill (November 2007; San Francisco Bay, CA, USA). In this baseline report, we identified which ruptured tank (port tank 3 or 4) was the source of the spilled oil and characterized changes in the oil composition across location and time. Samples from three impacted shorelines, collected within 80 days of the spill, were analyzed using one- and two-dimensional gas chromatography (GC and GC × GC, respectively). Weathering varied across sites, but compounds with GC retention times less than n-C16 were generally lost by evaporation and dissolution. Changes in n-C18/phytane and benz[a]anthracene/chrysene ratios indicated some biodegradation and photodegradation, respectively. 相似文献
60.
The prevalence of toxicopathic liver lesions in English sole (Pleuronectes vetulus) was determined along a presumed gradient of chemical contamination in Vancouver Harbour, Canada. Fish were captured from five sites in or near Vancouver Harbour, British Columbia, Canada. No toxicopathic lesions were observed in fish examined at the reference site (Howe Sound outside Vancouver Harbour), or at the outer harbour site. In contrast, 20-23% of the fish from three sites located in the central harbour, Indian Arm and Port Moody Arm had one or more types of toxicopathic lesions. Likewise, aromatic hydrocarbon (AH) metabolites measured in bile exhibited a gradient in levels from lower concentrations at the reference site to significantly higher levels in fish from Indian Arm and Port Moody Arm harbour sites. The occurrence of toxicopathic liver lesions was statistically associated with concentrations of AHs measured in sediment and AH metabolite levels measured in bile. 相似文献