Primary production of the cryptoendolithic microbiota from the Antarctic Desert

Primary production in the Antarctic cryptoendolithic microbiota can be determined from biomass and photosynthetic 14CO2 incorporation measurements. Even though good nanoclimate data are available, it is difficult to determine the amount of time when abiotic conditions permit metabolism. Making appropriate assumptions concerning the metabolism of the cryptoendolithic microbiota during periods of warmth, light and moisture, the primary production of the biota was calculated to be on the order of 0.108 to 4.41 mgC/m2/yr, with a carbon turnover time from 576 to 23,520 years. These production values are the lowest found on planet Earth.     

美国南阿帕拉契亚晚古生代上冲地体的复原再造

阿帕拉契亚造山带经历了早中古生代期间的增生历史,并伴有变形作用、变质作用和深成岩浆侵入作用。早中古生代期间形成的构造在二叠纪与非洲大陆碰撞期间,被阿勒格尼逆冲断层所切割。该逆冲断层从碰撞带下部的韧一脆性过渡带依次进入晚元古代和古生代裂谷边缘和地台,其上的构造迁移主要向北美内陆,但阿勒格尼走向滑移构造域也在包括主要为右行运动的内构造带中形成。有些地区(东部山麓)的右行位移明     

太古宙陆壳的熔融层存在吗？：热力学估算及构造推断

笔者研究了太古宙陆壳中部分熔融层存在的条件和它们存在的后果。这可由一个已提出的最古老的云黄闪长岩-奥长花岗岩-花岗闪长岩(TTG)地壳,用开放系统的分离结晶作用模式来解释,其涉及到小于50Km深处的全球性部分熔融层(Kramers,1988)。对于一个熔融层保存的先决条件是它应被固体的地壳覆盖着。因为在低压条件下,     

实验地球化学

实验地球化学(实验岩石学)是近代发展起来的一个重要地质学分支。它是以物理化学的基本原理为理论基础,运用高温高庄实验技术,对自然界内生岩石和矿床、矿物的形成作用和过程进行深入的人工模拟研究的学科。其目的在于使人们能更直观地了解地质作用的过程和机理,更正确地掌握成岩成矿和地壳的演化规律,从而有效地推动地质理论的发展。     

Polycyclic aromatic hydrocarbons in bivalves from the San Francisco estuary: Spatial distributions, temporal trends, and sources (1993-2001)

Bivalve tissue samples were examined over a range of spatial and temporal scales (1993-2001) to determine PAH distributions, trends, and possible sources. Mussels (Mytilus californianus), oysters (Crassostrea gigas), and clams (Corbicula fluminea) were deployed for three months in the estuary at stations remote from known point source discharges. The range of summation operatorPAH detected in bivalves was oysters 184-6899 microg/kg dry wt (mean 678 microg/kg dry wt), mussels 21-1093 microg/kg dry wt (mean 175 microg/kg dry wt), and clams 78-720 microg/kg dry wt (mean 323 microg/kg dry wt). Linear regression analysis showed no statistically significant (p>0.05) temporal trends in clam and mussel summation operatorPAH at any of the deployment stations or estuary segments. On the other hand, a statistically significant (p<0.05) decreasing trend was found in summation operatorPAH in oysters at the Petaluma River station, and in the North Estuary segment. PAH isomer pair ratios applied as diagnostic indicators suggested that the bioaccumulated PAH were derived primarily from petroleum combustion, with lesser amounts derived from biomass and coal combustion, and unburned petroleum.     

The nested superblock approach for regional-scale analytic element models

A new approach is presented for improving the computational efficiency of regional-scale ground water models based on the analytic element method (AEM). The algorithm is an extension of the existing "superblock" algorithm, which combines the effects of multiple analytic elements into Laurent series and Taylor series (superblock expansions). With the new "nested superblock" formulation, Laurent series are nested in a hierarchical (quad-tree) data structure with direct mathematical relationships between parent and child superblock coefficients. Nested superblocks significantly accelerate the evaluation of the complex potential and discharge function in models that contain a large number of analytic elements at multiple scales. This evaluation process, the primary computational cost of AEM models, is required to determine the element coefficients, generate contour plots, and trace pathlines. The performance of the nested superblocks is demonstrated with a simplified model based on the Lake Ontario watershed geometry comprising thousands of hydrogeologic features at multiple geographic scales.     

Nutrient dynamics at the sediment-water interface in a Mediterranean lagoon (Thau, France): influence of biodeposition by shellfish farming activities

The Thau Lagoon, a French Mediterranean shallow lagoon, is a site where extensive shellfish farming occurs. The aim of the present work is to evaluate the role of this activity on nutrient exchange at the sediment-water interface in relation to organic matter (OM) sedimentation and degradation. Two stations inside (C5) and outside (C4) of the shellfish farming areas were sampled at three seasons. Porewater chemistry surveys and calculated diffusive fluxes were used to evaluate the trophic status of the Thau lagoon. Quantitative (Particulate Organic Carbon) as well as qualitative OM (Hydrogen Index, Carbohydrates) analyses were performed on sediments to assess OM characteristics. Results emphasized that surficial sediments at C5 are always more enriched in OM. Porewater nutrient concentrations are 10-20 times higher at C5 than at C4. In June 2003, the porewater profiles exhibit a sharp gradient at the bottom waters, indicating a hypereutrophic status, leading to an anoxic crisis.     

NO3^—对硼同位素测定的干扰及其消除

在石墨存在下测定Ｃｓ２ＢＯ２＾＋离子是硼同位素测定的最佳方法，但ＮＯ３＾－却存在严重的干扰，本文对这种干扰进行了详细的研究。为了避免ＮＯ３＾－的干扰，本文改进了硼的分离提取方法，完全避免了ＮＯ３＾－的引入，取得了满意的测定结果。