地壳增长与壳—幔再循环

在会聚边缘的地壳增长目前是由地壳从地幔中的萃取作用所支配的,这是一个只能间接观察到的过程。在现代的会聚边缘,常见于地壳最上部的玄武岩和安山岩(及相应的侵入岩)并非直接源于地幔(如它们不是地幔的初始成分)。例如,在阿留申岛弧,橄榄拉斑玄武岩已被认作是初始岩浆,它与普通高铝玄武岩有关,而后者是由积聚在莫霍面深处的橄榄石和辉石的分离作用所形成的,并代表一个新生的上地幔,更常见的浅部富铝质火山岩及深成岩可以由高铝玄武岩的壳内组分分异、岛弧地壳低熔组分的同化、地壳熔融所形成,或者是诸过程结合的产物。每个岛弧真正的地壳剖面取决于岛弧     

卡鲁溢流玄武岩由地幔羽—岩石圈混合作用形成的Re—Os同位素证据

大量证据表明大陆溢流玄武岩省与地幔羽活动有关。然而，溢流玄武岩所具有的放射性同位素特征往往超出了地幔羽源区（如海岛玄武岩所证实的）范围。这些特征较易解释为大陆岩石圈源于将温度较低的，难熔的地幔岩石圈贡献了富集同位素的（低＾１４３Ｎｄ／＾１４４Ｎｄ）物质。然而，对于将温度较低的，难熔的地幔岩石圈作为玄武质岩浆的一个重要源区的模式有不少反对意见。关于玄武岩的成因，Ｒｅ－Ｏｓ体系可以对地幔羽和大陆下岩石     

长江倒灌对鄱阳湖水动力特征影响的数值模拟

长江水倒灌是鄱阳湖的一个重要现象,是江湖作用的具体体现.利用环境流体动力学开源代码(EFDC)建立鄱阳湖的二维水动力模型,并借助染色剂模块和水龄模块,分析鄱阳湖全年的水动力变化过程、倒灌现象及其影响.数值模拟结果精确地验证倒灌的发生、持续时间和倒灌流量,显示倒灌时期湖区水力梯度、湖流逆向的特点.顶托作用强于鄱阳湖盆地作用时是倒灌发生的条件,通过计算倒灌发生的临界流量并与实际来流进行对比,本文提出新的倒灌判定条件,可以准确地预测倒灌和预估倒灌流量,且利用2007 2009年的测量数据验证了其可靠性.通过在赣江入流设置染色剂的方法,模拟获得2008年4次倒灌入流水体在湖区的占据面积.顶托作用和倒灌造成湖水不能外泄甚至逆流,增加湖区水体的水龄,通过数值模拟并与水力停留时间进行对比,估算出湖湖水水龄的增加时间.     

Impacts of diverted freshwater on dissolved organic matter and microbial communities in Barataria Bay, Louisiana, U.S.A

Here we present results of an initial assessment of the impacts of a water diversion event on the concentrations and chemical composition of dissolved organic matter (DOM) and bacterioplankton community composition in Barataria Bay, Louisiana U.S.A, an important estuary within the Mississippi River Delta complex. Concentrations and spectral properties of DOM, as reflected by UV/visible absorbance and fluorescence, were strikingly similar at 26 sites sampled along transects near two western and two eastern areas of Barataria Bay in July and September 2010. In September 2010, dissolved organic carbon (DOC) was significantly higher (568.1-1043 μM C, x=755.6+/-117.7 μM C, n=14) than in July 2010 (249.1-577.1 μM C, x=383.7+/-98.31 μM C, n=14); conversely, Abs254 was consistently higher at every site in July (0.105-0.314) than in September (0.080-0.221), averaging 0.24±0.06 in July and 0.15±0.04 in September. Fluorescence data via the fluorescence index (FI450/500) revealed that only 30% (8 of 26) of the July samples had an FI450/500 above 1.36, compared to 96% (25 of 26) for the September samples. This indicates a more terrestrial origin for the July DOM. Bacterioplankton from eastern sites differed in composition from bacterioplankon in western sites in July. These differences appeared to result from reduced salinities caused by the freshwater diversion. Bacterioplankton communities in September differed from those in July, but no spatial structure was observed. Thus, the trends in bacterioplankton and DOM were likely due to changes in water masses (e.g., input of Mississippi River water in July and a return to estuarine waters in September). Discharge of water from the Davis Pond Freshwater Diversion (DPFD) through Barataria Bay may have partially mitigated some adverse effects of the oil spill, inasmuch as DOM is concerned.     

美国海水养殖业的机会

世界人口对蛋白质来源的需求日益增长,而全球野生鱼类和贝类供应目前尚满足不了人们日益增长的需求。因此,海水养殖的发展具有广阔的前景。 人类养殖(农牧)鱼类和贝类已有数百年的历史。尽管大多数人认识到海水养殖是一个全球增长潜力很强,并可持续发展的行业,但是最佳的机遇在何处、何时出现敏感问题则是很难证明的。美国是否可能以海水养殖生产者大国的地位出现在国际舞台上,在这个时候也是很