10,000 years of climate control over carbon accumulation in an Iberian bog(southwestern Europe)

The northwest region of the Iberian Peninsula is home to a unique ecosystem of bogs,which are particularly sensitive to projected climate cha nge.In this context,the rate of carbon(C)accumulation in Chao de Veiga Mol.an intact raised bog,was analysed.Changes in the accumulation rate over the past10 millennia were determined in a peat core of 847 cm in depth,with a high mean rate of peat growth(11 yr cm^-1,0.09 cm yr^-1).An age-depth model was generated from 22 14C dates and fallout radionuclides.Chronological,stratigraphical and physico-chemical data confirmed the existence of a single cycle of peat formation throughout the Holocene and the formation of ombrotrophic peat 9500 years ago.The total mean C content was 50.2%,and over 10 millennia 583 kg C m^-2 accumulated at a mean rate of 35.3 g C m^-2 yr^-1,with a long-term(apparent)rate of carbon accumulation in the catotelm of59.9 g C m^-2 yr^-1.These values are much higher than reported for other Iberian peatlands and are amongst the highest documented for peatlands in the northern hemisphere.The dynamics of C accumulation and other measured parameters reveals important variations throughout the Holocene.They could be associated with the main climatic events described in the northern hemisphere and are highly consistent with models established for northern latitudes.The Chao de Veiga Mol raised bog is unique and of great potential value for carrying out high resolution palaeoenvironmental studies,especially in relation to regional and Iocal modulations in southern Europe.     

小行星

1.在组成理论天文学的各种问题中,小行星运动的研究占了很大的地位。小行星是在两个世纪分界的时候发现的(1801),在那时,牛顿提出的基本问题——用万有引力定律来解释太阳系内天体运动的一切特点,已经差不多被18世纪的伟大数学家们的劳动完成了,古典天体力学的基本输廓,已被拉普拉斯建立起来。小行星的发现,由于它们的运动同太阳系其他成员有很大的区别,给天体力学的发展提出了完全新的问题,而且是一种新的刺激物。     

边坡稳定性分析中的剩余推力法

基于传统的剩余推力法思路,推导了包括地表水、地下水、地震力、锚固力等外荷载综合作用下的边坡稳定性和剩余推力计算公式,以实例给出了剩余推力法在MicrosoftExcel中的实现方法,从中可以清晰看出剩余推力法的实质.比较了用同一安全系数但采用不同的折减方法所获得的剩余推力变化趋势.通过上述4类荷载的敏感性分析,指出了剩余推力法应用中应注意的基本问题.运用Excel中加载宏"规划求解”工具,可以方便实现确定性框架下临界滑动面的随机搜索.     

Intersex and sterility in the periwinkle Littorina littorea (Mollusca: Gastropoda) along the Western Scheldt estuary, The Netherlands

In this study we present the results of an intersex survey of Littorina littorea along the heavily polluted Western Scheldt estuary (the Netherlands), and record for the first time the intersex phenomenon in L. littorea from Dutch waters. Intersex differed significantly between localities and was the highest in the vicinity of the harbours of Antwerp and Vlissingen, as reflected by the I     

MODFLOW/MT3DMS-based reactive multicomponent transport modeling

This paper presents a three-dimensional, MODFLOW/MT3DMS-based reactive multicomponent transport model for saturated porous media. Based on a split-operator technique, the model, referred to as PHT3D, couples the transport simulator MT3DMS and the geochemical modeling code PHREEQC-2. Through the flexible, generic nature of PHREEQC-2, PHT3D can handle a broad range of equilibrium and kinetically controlled reactive processes, including aqueous complexation, mineral precipitation/dissolution, and ion exchange. The diversity of potential applications is demonstrated through simulation of five existing literature benchmarks and a new three-dimensional sample problem. The model might be applied to simulate the geochemical evolution of pristine and contaminated aquifers as well as their cleanup. The latter problem class includes the natural and enhanced attenuation/remediation schemes of a wide range of organic and inorganic contaminants. Processes/reactions not included in the standard PHREEQC-2 database but typical for this type of application (e.g., NAPL dissolution, microbial growth/decay) can be defined and included via the extensible PHREEQC-2 database file.