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61.
A protocol was developed to fractionate soil particles down to the nanocolloid scale by combining sieving, sedimentation,
centrifugation, and cross-flow filtration (CFF). The validity of the method and the performance of the CFF system were tested
by characterizing fractions using laser granulometry, electron microscopy, and chemical analysis. The 0.1-μm-pore-size membrane
CFF system effectively retained nanocolloids (<0.1 μm) as shown by laser granulometry and observed directly by transmission
electron microscopy. However, environmental scanning electron microscopy images of freeze-dried colloids were very different
from their TEM counterparts, suggesting that sample preparation influenced microscopy imaging. Chemical analysis of Cu, Cd,
and organic carbon in each fraction showed that the concentrations of these components increased as particle size decreased,
indicating colloids and nanocolloids play an important role in retaining trace metals. Particle-size fractionation combined
with chemical analysis and electron microscopy can provide insight into the nature and properties of nanocolloids in soil. 相似文献
62.
Characteristics of Important Stopover Locations for Migrating Birds: Remote Sensing with Radar in the Great Lakes Basin 总被引:1,自引:0,他引:1
DAVID N. BONTER†‡ SIDNEY A. GAUTHREAUX JR§ . THERESE M. DONOVAN‡ 《Conservation biology》2009,23(2):440-448
Abstract: A preliminary stage in developing comprehensive conservation plans involves identifying areas used by the organisms of interest. The areas used by migratory land birds during temporal breaks in migration (stopover periods) have received relatively little research and conservation attention. Methodologies for identifying stopover sites across large geographic areas have been, until recently, unavailable. Advances in weather-radar technology now allow for evaluation of bird migration patterns at large spatial scales. We analyzed radar data (WSR-88D) recorded during spring migration in 2000 and 2001 at 6 sites in the Great Lakes basin (U.S.A.). Our goal was to link areas of high migrant activity with the land-cover types and landscape contexts corresponding to those areas. To characterize the landscapes surrounding stopover locations, we integrated radar and land-cover data within a geographic information system. We compared landscape metrics within 5 km of areas that consistently hosted large numbers of migrants with landscapes surrounding randomly selected areas that were used by relatively few birds during migration. Concentration areas were characterized by 1.2 times more forest cover and 9.3 times more water cover than areas with little migrant activity. We detected a strong negative relationship between activity of migratory birds and agricultural land uses. Examination of individual migration events confirmed the importance of fragments of forested habitat in highly altered landscapes and highlighted large concentrations of birds departing from near-shore terrestrial areas in the Great Lakes basin. We conclude that conservation efforts can be more effectively targeted through intensive analysis of radar imagery. 相似文献
63.
目的 解决多层泡沫夹芯结构的雷达吸波复合材料在环境效应下产生外观失效的问题。方法 制备3种类型的雷达吸波复合材料,开展典型自然环境试验。观察试验样品外观状态,并检测变形量。通过观察泡沫的微观组织形貌,检测热膨胀量变化及泡沫与树脂间的粘黏强度,用气相色谱质谱联用仪GCMS检测复合材料裂解气体成分,分析复合材料外观失效成因,并提出解决技术途径。结果 6个月自然环境试验后,1#、2#样品外观失效,而3#样品无明显变化。复合材料100℃裂解气体成分为氮气、二氯一氟乙烷、甲基膦酸二甲脂。4种泡沫在22~85℃的最大热膨胀量分别为–0.18%、–0.37%、–0.30%、–0.45%。环氧树脂与4种泡沫的粘黏强度在41~52N,而聚氨酯树脂达到了54~81N。结论 雷达吸波复合材料泡孔内残留气体的释放,是导致外观失效的根本原因。通过热处理工艺,减少样品残留气体量,并提升胶黏剂与泡沫的粘黏复合强度,是提升复合材料环境适应性的有效技术途径。 相似文献
64.
多普勒雷达回波在一次大暴雨中的应用分析 总被引:2,自引:0,他引:2
利用多部新一代天气雷达资料结合常规探空资料和逐小时的自动站资料,对2007年7月18日发生在河北省东部平原(以下简称冀东平原)的一次区域性暴雨过程进行分析。结果发现:低层中α尺度切变线的南压、东移及"人"字形辐合线是本次降水过程的主要影响系统;降水发生前西南暖湿气流和冀东平原近地层偏东风是"人"字形辐合线形成的直接原因;在不稳定层结存续条件下,急流方向上上游雷达站中尺度低空急流的脉动对下游台站的短时暴雨预报具有一定时效的指示意义。 相似文献
65.
66.
Shinsaku Dobashi Yoshiki Yamaguchi Yoshinori Izawa Akihide Wada Michikazu Hara 《Journal of Material Cycles and Waste Management》2009,11(2):148-154
This study demonstrates the applicability of laser mass spectrometry for safety management of the processed gas and the work
environment in a polychlorinated biphenyl (PCB) disposal plant. By utilization of laser ionization/ion trapping storage/time-of-flight
mass spectrometry (LI-IT-TOFMS), we analyzed gaseous PCBs from scrap capacitors with on-line detection. It was confirmed that
few contaminants were detected in the spectrum. By the effect of laser-induced selective ionization, it was considered that
there was little interference with the mass range of PCBs. The accuracy of LI-IT-TOFMS when analyzing environmental gas was
almost the same as that for the PCB standard gas. It was possible to perform on-line analysis of the work environment for
over 2000 h (120 000 data points). LI-IT-TOFMS was thus shown to be a very useful method for ensuring the safety of the work
environment in disposal plants for PCBs. 相似文献
67.
68.
Monitoring and assessment of toxic metals in Gulf War oil spill contaminated soil using laser-induced breakdown spectroscopy 总被引:1,自引:0,他引:1
Laser-induced breakdown spectroscopy (LIBS) was applied for the detection of toxic metals in oil spill contaminated soil (OSCS).
The OSCS samples were collected from Khursania Saudi Arabia along the coast of Persian Gulf exposed to oil spills in 1991
Gulf war. Environmentally important elements like Aluminum Magnesium, Calcium, Chromium, Titanium, Strontium, Iron, Barium,
Sodium, potassium, Zirconium and Vanadium from the contaminated soil have been detected. Optimal experimental conditions for
analysis were investigated. The LIBS system was calibrated using standard samples containing these trace elements. The results
obtained using Laser-Induced Breakdown Spectroscopy (LIBS) were compared with the results obtained using Inductively Coupled
Plasma Emission Spectroscopy (ICP). The concentrations of some elements (Ba and Cr) were found higher than permissible safe
limits. Health risks associated with exposure to such toxic elements are also discussed. 相似文献
69.
2010年5月5~6日和5月12~13日,湘中发生了两次区域性暴雨。运用了自动站降水资料、多普勒天气雷达基本反射率和基本径向速度资料以及NCEP提供的FNL资料,分析了这两次暴雨的雷达回波特征,并从水汽和地形两方面分析了两次暴雨的影响因素。结果表明:两次暴雨的环流形势场不同。 “100506”暴雨强降水回波呈带状自西南向东北扫过娄底,而“100513”暴雨强降水回波呈块状自西往东范围逐渐加强;两次暴雨都有逆风区存在,逆风区的范围和强度对应着强降水的范围与强度。两次暴雨水汽主要来自孟加拉湾和南海,“100506”暴雨发生在切变线附近;“100513”暴雨发生在切边线南侧的辐合区内。娄底西部、北部、中部山地的阻挡和抬升作用以及冷暖气流交汇也是暴雨产生的重要原因之一 相似文献
70.