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731.
本文论述了中国东南大陆中、新生代岩浆作用的多旋回性和迁移性,构造演化与岩石系列和岩石组合的关系。前寒武纪岩石圈制约本区中、新生代岩浆作用和成矿作用,并在三种岩石围岩石学一地球物理综合模型中反映。总结了四个主要构造期岩浆作用源区特征和构造背景,并根据不同大地构造单元在碰撞造山后近南北向刊近北东向伸展裂解,从造山带挤压碰撞向伸展裂解机制转换过程探讨了中、新生代岩浆作用和壳幔演化动力学。 相似文献
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733.
A comprehensive investigation of heavy metal pollutants in Xiangjiang river was accomplished to evaluate their chemical stability through three different ways: (1) Chemical speciation by direct measurements; (2) Chemical equilibrium model simulation; (3) Sediment extraction experiments. All the results demonstrated that the directly bioavailable fraction was in a very limited amount. The metal bound to organic ligands, adsorbed particles and precipitated species presented a buffer for solution species. The majority of metals occured in the residues as solid particulates. It was inferred that the heavy metal pollutants in this aquatic system exhibited a high chemical stability. The critical limits of discharging load and pH values were suggested. 相似文献
734.
通过对全市放射性污染源现状调查 ,摸清了全市放射性源的种类、数量、分布及放射性污染物排放现状以及存在的主要环境问题 ,针对存在的问题 ,提出了减轻污染的防治对策 相似文献
735.
在地震台站,地震计与模数转换器,计算机,通讯设备一起构成一个系统,系统中任何一个环节不能正常工作,都会影响整个系统。判断系统究竟是哪一部份有故障,需要冷静分析,对比试验,逐一排除。故障现象可能一样,但原因可能有多种。因此,不仅要了解系统的工作原理,还要有一定的工作积累,才能迅速准确地找到故障原因并排除。 相似文献
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737.
运用小波变换方法分析了跨断层形变观测资料不同尺度的小波变换的细节信号变化特征.研究结果表明:1)不同尺度小波变换分解的细节信号显示出不同的时变特征.当尺度为1时,日均值的细节信号主要为噪声;尺度为2、4时,日均值细节信号主要为非平稳信号;尺度为5、6时,细节信号主要为平稳周期信号;2)每月观测一次和每4月观测一次的跨断层形变资料在尺度为3时的细节信号有较好的年周期特征;3)关中地区垂直形变小波处理结果与测点附近200km左右范围内的中强地震有较好的对应关系,口镇-关山断裂2005年最新资料显示异常,应给予关注. 相似文献
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739.
Shujuan Lou Jietai Mao Meihua Wang 《Frontiers of Environmental Science & Engineering》2007,1(3):345-349
The objective of this study was to determine the black carbon concentration in Beijing in 2003. The aerosol properties were measured using an Aethalometer and a tapered element oscillating microbalance (TEOM) on the roof of the Physics Building of Peking University (39.99° N, 116.31° E) from July to August 2003 and from November 2003 to January 2004. The average black carbon (BC) concentrations in the summer and winter were 8.80 and 11.4 μg/m3, respectively. During winter, two different cyclone cut offs were installed at the inlet of an aethalometer. The BC mass concentration in TSP, PM10, and PM2.5 were obtained. The results indicated that in winter aerosol, 90% of BC exited in PM10 and 82.6% of BC exited in PM2.5. The BC in PM10 accounted for 5.11% of the PM10 mass. 相似文献
740.
Mao Ting Wang Yue-si Xu Hong-hui Jiang Jie Wu Fang-kun Xu Xiao-bin 《Atmospheric environment (Oxford, England : 1994)》2009,43(15):2503-2508
Intensive field investigations were conducted at the summit of Mount Tai in June 2006 to understand the effects of the local and regional sources on atmospheric volatile organic compounds (VOCs) distributions. A total of 60 samples were collected and determined by quantitative analytical methods. The concentrations of the total VOCs (TVOCs) observed in the air of Mount Tai were 6.95 ± 5.71 ppb. Aromatic hydrocarbons provided the largest contribution to TVOCs, followed by alkanes and halocarbons. High levels of halocarbons accounted for 20% of TVOCs due to emission from a PVC plant located at the foot of Mount Tai. Alkenes and cycloalkanes contributed little to the total VOCs. The day-and-night differences and day-to-day variations in the concentrations of four selected species were investigated and the effects of several factors such as meteorological parameters, sources and transport characteristics on them were discussed in details. A back trajectory analysis showed that relatively higher levels of VOCs were related to long-range transport of pollutants from polluted areas. The vertical motions of air masses also had a large impact on the variations of the levels of VOCs. The result of the variability–lifetime relationships of VOCs, which is used to estimate the remoteness of the sampling location, showed that Mount Tai represents intermediate conditions between remote sites and sites in the vicinity of sources. 相似文献