浅层地下水氯代烃污染天然生物降解的判别依据

天然条件下氯代烃生物降解的判别, 是确定氯代烃污染天然衰减恢复治理技术是否可以采用的关键, 可为天然衰减恢复治理技术的应用提供技术支持.通过分析氯代烃生物降解的特性发现, 地下水环境中氯代烃的生物降解, 必然伴随有第一基质、电子受体、中间产物以及有关的一些间接性指标, 在污染羽状体不同位置及污染羽状体内外产生明显变化, 这些指标的变化均可以不同程度地指示氯代烃生物降解的产生.据此总结出氯代烃生物降解衰减的判别依据分别为电子受体、第一基质(能源和碳源) 及降解中间产物三类指标.      

加强技术创新,迎接新世纪和知识经济的挑战--致读者和作者

中共中央、国务院<关于加强技术创新,发展高科技,实现产业化的决定>,是全面实施党的科教兴国、建设国家知识创新体系和持续发展战略的重大举措,直接关系到我国在新世纪中的国际地位和竞争力,关系到中华民族的伟大复兴.认真学习和落实文件精神,有着重要的现实意义和历史意义.     

北赤道流区海温异常与ENSO循环

应用热带太平洋上层XBT温度资料，分析探讨了西太平洋暖池区次表层海温冷暖异常信号的变化规律，揭示了影响西太平洋暖池区次表层海温冷暖异常信号的机制。分析表明，西太平洋暖池区的次表层海温异常冷暖与太平洋北赤道流的海温冷暖异常信号西传有重要关系。北赤道流的海温异常冷(暖)信号是沿温跃层由赤道中东太平洋潜沉向西太平洋暖池区传播，对暖池区域次表层海温场产生重要影响。这一传播过程与西太平洋次表层海温异常暖(冷)信号向赤道中东太平洋传播，构成了热带海洋信号的气旋式“信号通道”。在这一“信号通道”中，北赤道流的海温异常信号西传是导致西太平洋暖池区及西太平洋次表层海温异常的重要机制，是影响El Nifio和La Nifia事件发生的关键。     

1999年和2009年夏季珠江口环境要素的对比与分析

对1999年和2009年夏季珠江口的温、盐、溶解氧、叶绿素和径流量等数据进行分析。结果表明,由于1999年航次期间珠江较大的径流量,1999年冲淡水的扩展范围要大于2009年。1999年夏季珠江口水体存在较强的盐度层结,而2009年夏季受较小的珠江径流量和热带风暴浪卡的共同作用,水体盐度层结较弱,0—5m层水体垂向混合良好。两年夏季珠江口表层溶解氧(DO)的分布较为相似,而底层溶解氧的分布则有显著差异,主要表现在河口西岸浅滩区和河口口门外。1999年河口西岸浅滩区DO小于3mg.L-1,河口口门外DO在4—5mg.L-1之间,2009年河口西岸浅滩DO大于5mg.L-1,河口口门外DO小于3mg.L-1。1999年夏季伶仃洋海域内较强的盐度层结是其底层出现低氧环境的主要原因,2009年夏季强化的垂向混合使得表底层溶解氧得到了及时交换,阻碍了西岸浅滩区底层低氧环境的出现,而盐度层化和浪卡带来的浮游生物的耗氧作用可能是口门外底层出现低氧环境的原因。     

Stress,strain and earthquake activity

There are 13 papers in this special issue on stress field,crustal deformation and seismicity.The great Wenchuan earthquake is a grievous disaster,but Chinese scientists are trying to learn more from the event in order to understand better the physics of earthquakes for     

Dynamic rupture process of the 1999 Chi-Chi,Taiwan,earthquake

In this study, we preliminarily investigated the dynamic rupture process of the 1999 Chi-Chi, Taiwan, earthquake by using an extended boundary integral equation method, in which the effect of ground surface can be exactly included. Parameters for numerical modeling were carefully assigned based on previous studies. Numerical results indicated that, although many simplifications are assumed, such as the fault plane is planar and all heterogeneities are neglected, distribution of slip is still consistent roug...     

A brief discussion on the relationship between apparent stress and slip-weakening law based on the energy partition criteria

According to the representation theorem of seismic energy radiation,we know that,at any point on the fault,the instantaneous seismic radiation energy,ES,the seismic moment M0,and the apparent stress σa=μES /M0(μ is the shear modulus on the fault plane) should be positive values at any time during an earthquake faulting.However,we have noticed that,in recent source parameter inversion scheme for deriving the critical slip-weakening distance,the apparent stress used as a constraint condition on the fault plan...     

Decline of groundwater table in Beijing and recognition of seismic precursory information

This paper quantitatively analyzed groundwater table fluctuations caused by groundwater overdraft, and probed into the possibility of drawing earthquake precursory information from groundwater table variations on the background of groundwater overdraft. Main effect factors of groundwater regime in Beijing region include groundwater extraction and rainfall. The decline of groundwater table was directly related to regional groundwater overdraft. Using the method of correlation analysis, the paper analyzed the...     

Pervasion degree of convective mixing and investigations of mantle mixing

Geodynamic studies have shown that mantle convection is like a giant blender to make the original heterogeneous mantle mixing and homogenizing. However,some models,especially from geochemical data show that the modern mantle may still contain a number of reservoir bodies with different chemical composition. Then,the modern mantle is homogeneous? Authors have defined a box replacement degree of convective mantle mixing and pervasion degree of convective mantle mixing (that equals to initial density of tracin...     

Short-term and imminent geomagnetic anomalies of the Wenchuan M_S8.0 earthquake and exploration on earthquake forecast

The diurnal variation of the geomagnetic vertical component is exhibited mainly by changes of phase and amplitude before strong earthquakes.Based on data recorded by the network of geomagnetic observatories in China for many years, the anomalous features of the appearance time of the minima of diurnal variations(i.e, low-point time) of the geomagnetic vertical components and the variation of their spatial distribution(i.e, phenomena of low-point displacement) have been studied before the Wenchuan MS8.0 eart...