Evidence of long-lived I and Pu isotopes enrichment in vegetation samples around the Marcoule Nuclear Reprocessing Plant (France)

Iodine-129 and ²³⁸Pu, ²³⁹Pu and ²⁴⁰Pu are radionuclides posing a long-term safety concern due to their potential integration in bio and geo-chemical cycles and their significant half-lives. They are present throughout the environment at very low levels, and more particularly, nuclear fuel reprocessing plants (NRP) have been identified as local sources of these radionuclides. However, due to measurement difficulties, published data concerning their activity levels in terrestrial environments around NRP facilities remain scarce. The aim of the present paper is to communicate ¹²⁹I, ²³⁸Pu and ^239+240Pu measurements results from the area surrounding the Marcoule NRP, which is situated in SE France. Several vegetation samples were collected around the nuclear installation in 1999 and 2000, in order to examine the possible impacts of its atmospheric I and Pu discharges. Based on ²³⁸Pu/^239+240Pu activity ratios and ¹²⁹I/¹²⁷I isotopic ratios, local increases in Pu and ¹²⁹I were detected and related to industrial activity.     

中国海洋地球物理进展

在中国地球物理学会50周年之际，总结海洋地球物理工作是十分重要的文章从中国海油气普查、近海工程地质调查。大洋多金属结核调查和中国海基础调查四个方面简要地阐述它们的进展。     

Mountain wave motions determined by the Esrange MST radar

A European campaign of ground-based radar, lidar and optical measurements was carried out during the winter of 1996/1997 (28 December–2 February) to study lee waves in the northern part of Scandinavia. The participants operated ozone lidars, backscatter lidars and MST radars at ALOMAR/Andoya and Esrange/Kiruna, and an ALIS imaging system in Kiruna. The Andoya site was generally windward of the Scandinavian mountains, the Kiruna site on the leeward side. The goal of the experiment was to examine the influence of lee waves on the formation of Polar Stratospheric Clouds (PSCs). This paper studies the radar data from MST-radar ESRAD located at Esrange [68.°N, 21.°E], i.e. in the lee of the mountains. We present three cases where strong lee waves were observed: in one case they propagated upwards to the lower stratosphere and in the other two cases they were trapped or absorbed in the troposphere. We examine the local waves and the direction and strength of the local wind using the radar, the synoptic meteorological situation using weather maps (European Meteorological Bulletin) and the synoptic stratospheric temperatures using ECMWF data. We observed that waves propagate up to the stratosphere during frontal passages. When anticyclonic ridges are present, the propagation to the stratosphere is very weak. This is due to trapping of the waves at or below the tropopause. We also show that the radar data alone can be used to characterise the different weather conditions for the three cases studied (through the variation of the height of the tropopause). The synoptic stratospheric temperatures in the three cases were similar, and were above the expected threshold for PSC formation. Lidar and visual observation of PSCs and nacreous clouds, respectively, showed that these were present only in the case when the lee waves propagated up to the lower stratosphere.     

区域土地利用变化及其对粮食生产影响分析——以山东省为例

土地利用变化及其效应是目前全球变化研究的热点之一。本文以山东省为例,在分析土地利用结构特点和粮食总产量的时间变化趋势的基础上,进一步探讨了土地利用变化对粮食生产的影响。其影响主要表现在:土地利用类型变化与粮食播种面积、土地利用程度变化与粮食总产、土地利用集约度与粮食单产等三个方面。针对上述影响进一步探讨了保障粮食生产可持续发展的措施及土地利用分区,可为区域土地利用取向和制定粮食发展政策提供科学依据。     

Gravity evidence for a mafic intrusion beneath a mineralized zone in the Bondy gneiss complex, Grenville Province, Quebec — Exploration implications

A ground gravity survey over the Bondy gneiss complex and its mineralized iron oxide- and copper-rich hydrothermal system(s) in the Grenville Province of SW Quebec was undertaken to aid mineral exploration in mapping subsurface intrusions. Several kilometric-scale positive Bouguer anomalies were identified that coincide with outcropping mafic and intermediate intrusive rocks of the post peak-metamorphic, 1.17-1.16 Ga mafic to intermediate Chevreuil suite intrusions and a 1.09-1.07 Ga Rolleau ultramafic stock. An additional 4 × 3 kilometre positive gravity anomaly indicates a mafic body underlies part of the metamorphosed hydrothermal system in the area of magnetite, pyrite, pyrrhotite, and chalcopyrite mineralization. Advanced argilic alteration associated with sulphide enrichment here is however indicative of an epithermal system with a felsic intrusion fluid source. As a felsic intrusion cannot explain the positive Bouguer gravity anomaly both felsic and mafic bodies must be present beneath the mineralized zone. Our preferred interpretation based on integrating gravity data and 2D forward gravity modelling with the results of field and geochemical studies is that this anomaly corresponds to a ca. 500 m deep mafic 1.17-1.16 Ga Chevreuil suite pluton that may have provided the source for hydrothermal fluids associated with late ductile shear- and fault-related mineralization or remobilization of early mineralization associated with a felsic pluton into late structures. This interpretation is compatible with gabbro xenoliths in the 1.07 Ga Rivard lamprophyre dyke on the NW margin of the gravity anomaly that bear significant similarities with those of the Chevreuil intrusive suite. The presence of both early felsic and late mafic intrusions beneath a group of three mineral occurrences in the Bondy gneiss complex strengthens their prospectivity in comparison to other mineral occurrences in the area. That early, pre-metamorphic mineralization was upgraded late in the tectonothermal evolution during a subsequent igneous and deformation event agrees with interpretations of other IOCG-style deposits in the Lac Manitou area of the eastern Grenville Province.     

西辽河平原东部沼泽发育与中全新世早期以来古环境演变

根据典型沼泽剖面14 C测年及其树木年轮校正、孢粉分析、粘土矿物X 衍射分析、泥炭植物残体鉴定和沉积物的化学元素聚集与迁移资料 ,研究了中全新世以来西辽河平原东部沼泽发育过程与古环境演变及其二者的关系。结果表明 ,位于生态环境过渡带、脆弱带的沼泽发生、发育对环境变化尤为敏感。中全新世早期以来 ,环境变化频繁 ,由此导致沼泽发育出现多次形成、发育、退化、消亡、再生循环变化。沼泽发育与古环境演变可划分为 6个时期 :中全新世早期沼泽孕育与萌芽发育期 ;中全新世中期沼泽旺盛发育期 ;中全新世中晚期沼泽间断发育期 ;中全新世晚期沼泽退化发育期 ;晚全新世早期沼泽复苏期 ;晚全新世晚期沼泽消亡期。距今 5 80 0年左右为本区全新世沼泽最早发育期。沼泽发育也遵循富营养沼泽长期发展的模式     

Aeromagnetic signature of an exhumed double dome system in the SW Grenville Province (Canada)

Analysis of aeromagnetic data in the Grenville Province reveals the presence of two regional‐scale unmapped structural domes (the Morin and Mékinac‐Taureau domes) with an oval‐shaped magnetic pattern bounded by regional‐scale shear zones and a geometry that is similar to that produced in crustal flow models under extension, which predict two upright domes of foliation (double dome) separated by a steep shear zone. The Mékinac‐Taureau dome, a metamorphic core complex, and the Morin dome may have been exhumed by channel flow. Exhumation occurred by a combination of thrust, normal‐sense and wrench shear zones. The preservation of paragneisses in the Morin dome suggests that it underwent a lesser degree of exhumation than did the Mékinac‐Taureau dome. This study shows how the integration of local field information with magnetic data in a regional tectonic setting can reveal and delineate concealed gneiss domes and highlights a role for strike‐slip tectonics in the creation of regional structures involving the exhumation of deep crust.     

分区连续函数的Radon变换的高精度反演法

Ｒａｄｏｎ变换及其反演是ＣＴ技术的数学基础，常用的反演算法虽然在函数比较光滑的情况下都能获得较满意的结果，但当函数有较强的奇性时精度就比较差．对函数在每一子区域中是光滑，但在不同于区域交界处有间断的情况，本文给出了有高精度的反演算法．     

喜马拉雅和青藏高原深剖面研究的进展

概述了1992─1996年中、美、德合作开展“喜马拉雅和青藏高原深剖面及综合研究”的主要进展，包括研究项目的提出、工作进展概况和取得的主要科学、技术成果；并对今后的工作提出了建议．     

西太平洋海-气相互作用研究进展

主要对近十几年来我国在西太平洋海域海-气相互作用方面的研究成果作一简要回顾通过参与国际合作，我国在西太平洋海域已经获得大量观测资料，并在海气能量交换和物质交换方面取得了不少科研成果这些成果主要包括：（1）近中国海和热带西太平洋海域的海面动量、热量交换特征；（2）西太平洋及暖油海域的边界层特征；（3）海上气溶胶特性及分布规律；（4）热带西太平洋海-气二氧化碳交换。