排序方式： 共有17条查询结果，搜索用时 114 毫秒
1.
Molybdenum disulfide (MoS2), a layered transition-metal dichalcogenide, has been of special importance to the research community of geochemistry, materials
and environmental chemistry, and geotechnical engineering. Understanding the oxidation behavior and charge-transfer mechanisms
in MoS2 is important to gain better insight into the degradation of this mineral in the environment. In addition, understanding the
insertion of metals into molybdenite and evaluation of charge-transfer mechanism and dynamics is important to utilize these
minerals in technological applications. Furthermore, a detailed investigation of thermal oxidation behavior and metal-insertion
will provide a basis to further explore and model the mechanism of adsorption of metal ions onto geomedia. 相似文献
2.
Anomalies found in the isotope ratios of ozone are traceable to the ozone formation process. Metastable electronic states may be responsible for the preferred production of the heavy molecules. While laboratory isotope data and first tropospheric results agree well in the magnitude of isotope enrichments, stratospheric measurements show often higher values. Only through the collection of ozone samples can sufficiently large amounts of gas be obtained to analyze the three isotopes 48O3, 49O3, and 50O3. Collector systems have been developed and successfully operated in the troposphere and in the stratosphere. They will play in the future an important role in atmospheric oxygen isotope studies. 相似文献
3.
BO Husφy 《极地研究(英文版)》2002,13(1)
1 ＩｎｔｒｏｄｕｃｔｉｏｎＡｔｌａｔｉｔｕｄｅｓａｒｏｕｎｄ 80°Ｎａｎｄｉｎｔｈｅｍｅｓｏｓｐｈｅｒｅ /ｌｏｗｅｒｔｈｅｒｍｏｓｐｈｅｒｅ (ＭＬＴ) ,ｔｈｅｒｅｈａｖｅｂｅｅｎｆｅｗｍｅａｓｕｒｅｍｅｎｔｓｏｆｎｅｕｔｒａｌｄｙｎａｍｉｃｓ.ＡｒｅｑｕｉｒｅｍｅｎｔｗａｓｓｅｅｎｆｏｒｌｏｎｇｔｅｒｍｃｏｎｔｉｎｕａｌｍｏｎｉｔｏｒｉｎｇａｎｄａＶＨＦｍｅｔｅｏｒｒａｄａｒｗａｓｉｄｅｎｔｉｆｉｅｄａｓｂｅｉｎｇａｍｏｓｔｓｕｉｔａｂｌｅｉｎｓｔｒｕｍｅｎｔ.ＲａｄａｒｓｌｉｋｅｔｈｅＥＩＳＣＡ… 相似文献
4.
白云鄂博碳酸岩的方解石-白云石地质温度计 总被引：6，自引：2，他引：4
利用方解石-白云石地质温度计对白云鄂博地区碳酸岩的平衡温度进行了测定。出露于东矿下盘的白云岩质火山岩和出露于尖山的方解石-白云石型火山岩获得了较高的温度,分别为681℃和648℃。这些样品中的方解石呈二十微米左右晶形较完整的小片,被稍大粒度的白云石颗粒包裹,未受交代作用影响,推测这种碳酸岩在快速冷却的情况下保存下了其岩浆侵位时的成分特点,从而指示出接近碳酸岩浆侵位时的温度。但本区多数碳酸岩的平衡温度在400～500℃之间,有下列三种情况:(1)具有自形-半自形中粗粒粒状变晶结构的碳酸岩最后的平衡温度为415～496℃;(2)产自东矿的其余样品(火山岩),所测最后平衡温度为431～485℃,在测温的微区范围内可见极细粒白云石方解石与稀土等矿物共生的现象;(3)为交代重结晶结构的碳酸岩明显受到后期热液流体的交代,在流体的作用下共生方解石和白云石在成分上达到新的平衡,平衡温度为432～507℃。本文所分析的样品多数结果(371～507℃)与用白云石(方解石)和磁铁矿氧同位素温度计对白云鄂博碳酸岩的计算结果(360～546℃)十分一致。虽然有研究者对方解石-白云石温度计用于火成碳酸岩表示过质疑,但本文资料表明火成碳酸岩最后的平衡温度是可以运用方解石-白云石温度计法来计算的。 相似文献
5.
安徽巢湖凤凰山剖面石炭系微相和层序地层特征 总被引：9，自引：1，他引：9
应用露头层序地层学基本原理和方法 ,对巢湖凤凰山石炭系剖面进行重新研究。巢湖凤凰山石炭系总厚度为79.0 2 m ,在这个剖面中可以识别出 6种主要岩相、18种微相和 11个三级沉积层序 ,其中六个三级沉积层序属于 I型沉积层序 ,三个属于 II型沉积层序 ,缺失第 9和第 10沉积层序。三级沉积层序在不同的古地理单元和不同的沉积环境中可以进行对比。根据各微相特征和成因 ,揭示了沉积间断面上存在的多期古岩溶现象。阐述了三级层序及其对应的三级海平面升降旋回的特征 相似文献
6.
Alberto Araneda Patricia Jana Carolina Ortega Fernando Torrejón Sébastien Bertrand Patricia Vargas Nathalie Fagel Denisse Alvarez Alejandra Stehr Roberto Urrutia 《Journal of Paleolimnology》2013,50(1):41-56
Patagonia is commonly seen as an exceptionally pristine area because of its wildlife and practically unpolluted waters. However, during the twentieth century the burning of natural forests was one of the most important human activities in Northern Chilean Patagonia. Some estimations indicate that three million hectares were burned during the first three decades of the century. Hence the objective of this study was to evaluate the impacts of the historical fires in Lake Burgos (45º42′S) and Lake Thompson (45º38′S) in Chilean Patagonia. The impact was measured by evaluating chironomid assemblage since they are sensitive enough to be used as an indicator of aquatic ecosystem health. Fires have a direct and drastic effect on a lake watershed but also indirectly affect a lake ecosystem, changing sedimentation patterns or increasing nutrient inputs. In the studied lakes the periods with higher prevalence of fires were identified by charcoal analysis, while organic matter and magnetic susceptibility allowed the confirmation of pre-fire and post-fire periods. The chironomid composition was evaluated through a PCA and an analysis of similarity (ANOSIM) to test the significance among periods while a Detrended Correspondence Analysis was applied to the chironomid assemblage downcore to assess compositional structure and taxa turnover. In Lake Burgos the ANOSIM test indicated significant differences between the pre-fire and fire periods (p < 0.05), while in Lake Thompson differences were not significant. However, in Lake Thompson the PCA clearly separated the pre-fire from the fire period but not the fire from the post-fire periods. In both lakes chironomid composition changed in relation to the period of higher prevalence of fires, which in turn implies catchment changes, pollution, and other anthropogenic impacts. Particularly a marked change in mesotrophic/eutrophic taxa was detected, reflecting an increase in nutrient input due to deforestation. Our findings point out that the lacustrine ecosystems are still affected by the impact of fires and the subsequent increase in nutrient supply that occurred almost 50 years ago. No sign of reverting to pre-disturbance conditions was observed, which makes these lakes highly sensitive to current human-induced impacts. 相似文献
7.
Anthropogenic Climate Change: A Reason for Concern Since the 18th Century and Earlier 总被引：1，自引：0，他引：1
During the last 20 years the concept of anthropogenic climate change has left academic circles and become a major public concern. Some people consider ‘global warming’ as the major environmental threat to the planet. Even though mostly considered a novel threat, a look into history tells us that claims of humans deliberately or unintentionally changing climate is a frequent phenomenon in Western culture. Climate change, due to natural and anthropogenic causes, has often been discussed since classical times. Environmental change including climate change was seen by some as a biblical mandate, to ‘complete the Creation’. In line with this view, the prospect of climate change was considered as a promising challenge in more modern times. Only since the middle of the 20th century, has anthropogenic climate change become a menacing prospect. The concept of anthropogenic climate change seems to be deeply embedded in popular thinking, at least in Europe, which resurfaces every now and then after scientific discoveries. Also, extreme weather phenomena have in the past often been explained by adverse human interference. A list of claims of anthropogenic climate modifications is presented; the remarkable similarity of the anthropogenic climate change debate in the second half of the 19th century is compared to the present situation. Of course, the present threat seems much more real than any of the historical predecessors, which turned out to be overestimated. 相似文献
8.
9.
10.
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