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11.
水库冰气泡含量和密度对探地雷达测厚的影响分析(英文) 总被引:2,自引:0,他引:2
在水库现场试验了RIS K2型探地雷达探测水库冰厚度的能力,试验时所用天线频率为600MHz;同步钻孔测量雷达探测处的冰厚度;以及在一个点上取样测试分析冰晶体、冰内气泡和冰密度。试验时冰面积雪厚度0.03-0.05m,冰层上部有0.24m粒状冰,其下均为柱状冰;冰内气泡含量呈表层高底层低分布;冰密度随气泡含量变化;冰厚度在平面内不均一。通过探测厚度和实测厚度的对比分析以及气泡含量对介电系数影响的理论分析,建立了积雪、粒状冰和柱状冰三层介质模型,获取雷达波在冰内的理论传递时间。结果发现:能够利用等效介电常数或等效传播速度评价雷达波传递时间,结冰期冰层1/3深度处的对应介电常数或传递速度可以作为等效值;另外因冰内大气泡造成的理论传递时间大于雷达探测时间,其差值随理论传递时间或冰厚的增加呈非线性增加。 相似文献
12.
Elimination of Interferences in the Determination of Palladium,Platinum and Rhodium Mass Fractions in Moss Samples using ICP‐MS/MS 下载免费PDF全文
Terhi Suoranta Syed N. H. Bokhari Thomas Meisel Matti Niemelä Paavo Perämäki 《Geostandards and Geoanalytical Research》2016,40(4):559-569
Moss samples (Pleurozium schreberi) exposed to traffic‐related emission of Pd, Pt and Rh were analysed in this study. Successful elimination of interferences was achieved in the determination of Pd, Pt and Rh mass fractions in these samples using inductively coupled plasma‐tandem mass spectrometry (ICP‐MS/MS). Based on the results, a reliable determination of Pd, Pt and Rh mass fractions in microwave‐digested moss samples was obtained using ammonia (10% NH3 in He) in the collision/reaction cell when 103Rh was measured either on‐mass (103→103) or with mass‐shift (103→171) and mass‐shifts for 108Pd (108→159) and 195Pt (195→229) were used. The ICP‐MS/MS procedure was validated using BCR‐723 (road dust) as a reference material. In addition, a good agreement between the ICP‐MS/MS results and the results obtained with cloud point extraction and quadrupole ICP‐MS was observed for the moss samples. 相似文献
13.
The annual cycle of the thickness and temperature of landfast sea ice in the East Siberian Sea has been examined using a one-dimensional thermodynamic model. The model was calibrated for the year Augus... 相似文献
14.
A very large surface inversion, which would not have been detected at the official recording height of 2 m above the mire surface, was recorded at the snow surface of an earth hummock in Lapland. The maximum inversion was 35 °C, and the monthly temperature departure was 7.8 °C in December 1992. The characteristics of the surface inversion are compared with conditions during another winter when no long inversion periods occurred. The presence of this surface inversion may explain the formation of new permafrost in pounus, even when official records showed no unusually low temperatures. 相似文献
15.
16.
Matti Asikainen 《Geochimica et cosmochimica acta》1981,45(2):201-206
Approximately one thousand drilled wells were investigated for their natural radioactivity. The determinations of 238U, 234U, 226Ra and 222Rn from 310 samples showed a high state of radioactive disequilibrium between the members of the uranium series present in water. The activity ratio usually fell in the range 1–20 and the activity ratio in the range 1–20 × 10?4, the highest activity ratios being from samples with an elevated uranium content. The activity ratio varied between 0.76 and 4.67, the most frequent values showing a 60% excess of 234U in the samples. Most of the activity ratios near unity were found in samples with a high uranium content. Several drilled wells with anomalously high uranium contents were found in southern Finland. The average 226Ra and 222Rn contents of these wells were not exceptionally high, which suggests high mobility of uranium in groundwater from the areas involved. 相似文献
17.
The U---Pb age on pooled data of zircnos from the postorogenic Svecokarelian Mosshaga granite is 1788 ± 11 Ma (2 σ). The corresponding Rb---Sr whole rock age is 1742 ± 34 Ma (2 σ). The Mosshaga granite intrudes a synorogenic granodiorite, which has a U---Pb zircon age of 1889 ± 10 Ma and a Rb---Sr whole rock age of 1850 ± 28 Ma. The age differences between the U---Pb zircon ages and Rb---Sr whole rock ages are concluded to be geologically significant. It is shown that the Mosshaga pluton cooled rapidly and as a consequence the Rb---Sr isotopic system closed at a time very close to the crystallization of the zircons. A commonly observed feldspar and biotite alteration in Svecokarelian granitoids indicates migration of Rb and Sr isotopes in the whole rock system which may lead to apparently younger Rb---Sr ages. 相似文献
18.
Lathrap introduced the concept of lateral channel migration of the meandering rivers as a potential factor for human community dynamics in the Upper Amazon. Nevertheless, the dynamics considered by Lathrap is restricted to particular floodplains. He payed no attention to a large scale fluvial phenomenom: the sudden river relocations (avulsion), which also profoundly affected the Upper Amazon cultures. We present here a historical case study analyzing a river floodplain avulsion at the Middle Ucayali River during the late 1700s, causing the abandonment of a settlement called San Miguel de Cunibos and probably leading to the massive migration of the Cunibos Indians. Furthermore, we argue that similar situations have frequently occurred during the human history of the Upper Amazon, and thus these fluvial phenomena should be taken into consideration in future archaeological and ethnohistorical studies. © 1996 John Wiley & Sons, Inc. 相似文献
19.
The in situ sea-ice temperature, salinity and density observed from Chinese Antarctic Zhongshan Station have been applied to calculate the vertical profile of sea ice porosity. Based on numerical method, a number of schemes on sea-ice thermal diffusivity versus porosity have been accessed and one optimized scheme is identified by an optimal control model with an advanced distributing parameter system. For simplicity, the internal heating source item was neglected in the heat conduction equation during the identification procedure. In order to illustrate the applicability of this identified scheme, the vertical ice temperature profiles have been simulated and compared with measurements, respectively by using identified scheme and by classical thermodynamic formulae.The comparisons indicated that the scheme describing sea-ice thermal diffusivity and porosity is reasonable. In spite of a minor improvement of accuracy of results against in situ data, the identified scheme has a more physical meaning and could be used potentially in various applications. 相似文献
20.
Holocene colluvial chronology in a sub‐arctic esker landscape at Kuttanen,Finnish Lapland: kettleholes as geo‐ecological archives of interactions amongst fire,vegetation, soil,climate and geomorphological instability 下载免费PDF全文
John A. Matthews Matti Seppälä 《Boreas: An International Journal of Quaternary Research》2015,44(2):343-367
Excavations were made in the colluvial deposits of seven kettleholes in a sandy esker at Kuttanen, northwestern Finnish Lapland. The Holocene history of forest fires and the associated colluvial activity initiated on the slopes of the kettleholes were reconstructed based on 131 radiocarbon dates from charcoal layers. These dates were supplemented by luminescence dating of colluvial sand layers. The first forest fires occurred ~9000 years ago following the immigration of Pinus sylvestris about 1000 years after deglaciation. Evidence of forest fires and colluvial activity increased with the density of the pine forest, reaching a maximum during the Holocene Thermal Maximum between ~8000 and 4000 cal. a BP, declining thereafter to a minimum in the last ~500 years. This multimillennial‐scale pattern corresponds with forest fires being triggered by lightning strikes during the warmest summer weather of the Holocene, which also produced heavy rain and slope wash from convective storms. The 50 forest fires identified over the Holocene indicate a long cycle in fire frequency of 1 in ~200 years, which appears to reflect the average successional recovery time of the forest. Complex interactions amongst vegetation, fire and climate may account for little or no association between 23 centennial‐ to millennial‐scale clusters of forest fires/colluvial events and Holocene temperature or precipitation anomalies. Buried podzols indicate five phases of soil formation and hence low levels of landscape disturbance. The kettleholes and their colluvial deposits therefore provide a unique geo‐ecological archive that has led to new insights into the geo‐ecological interactions that affect environmental change in the sub‐arctic landscape. 相似文献