Enhancement of radon signals in geophysical studies with the track technique

The existence of a suspected geological fault has been confirmed using Solid State Nuclear Track Detectors (SSNTDs) by measuring radon concentration variations in the upper soil above its inferred position. The results obtained prompted us to increase the natural radon signal in the soil, using an additional radon source; this enhancement technique, has been experimentally checked with SSNTD detectors.On leave from Faculté des Sciences, Laboratoire des D.S.T.N. Université de Dakar, Dakar-Fann, Sénégal     

Seasonal variation of atmospheric dimethylsulfide at Amsterdam Island in the southern Indian Ocean

Daily measurements of atmospheric concentrations of dimethylsulfide (DMS) were carried out for two years in a marine site at remote area: the Amsterdam Island (37°50S–77°31E) located in the southern Indian Ocean. DMS concentrations were also measured in seawater. A seasonal variation is observed for both DMS in the atmosphere and in the sea-surface. The monthly averages of DMS concentrations in the surface coastal seawater and in the atmosphere ranged, respectively, from 0.3 to 2.0 nmol l^-1 and from 1.4 to 11.3 nmol m^-3 (34 to 274 pptv), with the highest values in summer. The monthly variation of sea-to-air flux of DMS from the southern Indian Ocean ranges from 0.7 to 4.4 mol m^-2 d^-1. A factor of 2.3 is observed between summer and winter with mean DMS fluxes of 3.0 and 1.3 mol m^-2 d^-1, respectively.     

大理州2005年初夏干旱成因探析

大理州2005年初夏出现了严重干旱气象事件.从500pHa高空环流特征、500pHa距平场特征、西太平洋副高特征量及北太平洋中低纬海温距平场、OLR距平场对这次干旱的成因进行了分析,分析结果表明：2005年初夏（4月1日～6月10日）降水异常偏少气温明显偏高是发生干旱的主要原因,高空大气环流异常、西太平洋副高持续偏强偏西、冷空气活动偏北是导致干旱的直接原因;孟加拉湾南部4月OLR场呈明显正距平,抑制低值系统的发展和东北移影响云南,是影响2005年大理初夏干旱重要原因;北太平洋中低纬海温特征与大理州初夏干旱有一定的遥相关性.     

An electrochemical study of pyrite oxidation in the presence of carbon coatings in cyanide medium

The anodic and cathodic behaviour of pyrite with clay and different carbon coatings of activated carbon, graphite and carbonaceous matter in cyanide medium was investigated using the potentiodynamic method. The presence of clay coating did not change the polarisation curve appearance for either the anodic oxidation of pyrite or the cathodic reduction of oxygen or the potential of the current plateau, but only decreased the plateau current especially at a higher coating thickness. The presence of the carbon coatings marginally shifted the rest potential for pyrite to a more anodic position and slightly changed the polarisation curve appearance for pyrite oxidation. The current density for pyrite oxidation largely increased in the presence of the carbon coatings, the potential at the plateau shifted to more cathodic positions, and the plateau width became smaller. These effects became more noticeable at a higher coating thickness. The activated carbon, graphite and carbonaceous matter coatings performed similarly in affecting pyrite oxidation at a similar thickness. The carbon coatings significantly increased the limiting current densities for oxygen reduction on pyrite, and the limiting current plateau became steeper at a higher coating thickness. The carbon coatings increased the limiting current density for oxygen reduction to a similar extent at a low coating thickness, but increased to varied extents at a higher coating thickness. The carbon coatings also greatly increased the cathodic current density for gold reduction on pyrite. The enhancement of pyrite oxidation and oxygen or gold reduction on pyrite by the carbon coatings was likely attributed to the electrochemical interaction between pyrite and the carbon materials with electron-rich surfaces and high conductivity. The presence of the carbon coatings significantly increased the oxidation of pyrite in aerated cyanide solutions and the preg-robbing of pyrite especially at a higher coating thickness.     

The effects of carbon dioxide leakage on fractures, and water quality of potable aquifers during geological sequestration of CO2

Since industrial revolution, the ＂greenhouse effect＂ is one of the most important global environmental issues. Of all the greenhouse gases, CO2 is responsible for about 64% of the enhanced ＂greenhouse effect＂, making it the target for mitigation, so reducing anthropogenic discharge of carbon dioxide attracts more and more attention. Geological sequestration of CO2 in deep saline aquifers is one of the most promising options. But because unknown fractures and faults may exist in the caprock layers which can prevent the leakage of CO2, CO2 will leak upward into upper potable aquifers, and lead to adverse impacts on the shallow potable aquifers. In order to assess the potential effect of CO2 leakage from underground storage reservoirs on fractures and water quality of potable aquifers, this study used the non-isothermal reactive geochemical transport code TOUGHREACT developed by Xu et al to establish a simplified 2-D model of CO2 underground sequestration system, which includes deep saline aquifers, caprock layers, and shallow potable aquifers, and study and analyze the changes of mineral and aqueous components. The simulation results indicated that the minerals of deep saline aquifers and fractures should be mainly composed of aluminosilicate and silicate minerals, which not only enhance the mass of CO2 sequestrated by mineral trapping, but also decrease the porosity and permeability of caprock layers and fractures to prevent and reduce CO2 leakage. The results from deep saline aquifers showed that the mass of carbon dioxide trapped by minerals and solution phases is limited, the rest remained as a supercritical phase, and so once the caprock aquifers have some unknown fractures, the free carbon dioxide phase may leak from CO2 geologic sequestration reservoirs by buoyancy.     

Rodent paleofaunas as indicators of climatic change in Europe during the last 125,000 years

This paper presents a quantitative reconstruction of the European late Pleistocene paleoclimate based on 72 rodent assemblages of five sequences from France, Germany and Bulgaria, covering the last interglacial-glacial cycle. They show a pattern of severe changes in temperature, with reduced precipitation during the coldest periods. A tentative correlation between the isotopic and palynological records and the paleotemperature changes is shown. These changes are consistent with variations in atmospheric circulation patterns in response to an expanding-retracting Fennoscandian ice-sheet. They can be attributed to the enhancement-weakening of the Scandinavian-Polar anticyclone and its associated dry winds, the south-north shifting of the North Atlantic Polar Front, and the varying supply of moist air from the Atlantic. Qualitative paleoenvironmental analysis shows broadleaved-deciduous forests in France and Bulgaria during most of the studied period. Taiga and tundra appeared in eastern France during the lower Würm. The German sequence indicates the presence of coniferous forests. These results are broadly consistent with other paleobiological records (mammalian, avian and insect faunas, isotopic record in dental tissue, palynology). The main discrepancies with the paleoclimate inferred from the palynological record are found during the coldest periods and are probably due to the interaction between vegetation, climate, and atmospheric CO₂ levels.     

森林碳汇决策与农村可持续发展研究(英文)

认为有必要在基于碳汇的土地利用和当地可持续发展之间建立一种更加明确的联系.依托一个中国-加拿大合作项目,以中国贵州省黎平县为例,阐述了一种将森林碳汇、森林资源管理以及如何促进当地可持续发展联系起来的综合评估方法,并且着重介绍了能帮助资源管理和规划部门实施这种综合评估的土地利用决策支持工具(LUDST) .     

湿地生态系统碳循环过程及碳动态模型

从地上、地下有机物质生产对湿地碳输入的贡献,湿地土壤碳库以及土地利用变化对湿地土壤碳库和碳排放的影响,甲烷排放和可溶性有机碳输出以及影响因子,湿地生态系统碳循环动态模型4个方面对湿地生态系统碳循环国内外研究进展和研究成果进行综述、分析,提出了我国亚热带区域天然湿地碳循环研究的主要热点和方向:⑴沿海湿地碳库估算及土地利用转化对土壤碳库和温室气体排放的影响;⑵酸沉降对于我国东南沿海低纬度地区湿地甲烷排放的影响;⑶沿海湿地生态系统碳循环动态模型的应用与开发;⑷湿地系统可溶性有机碳的输出机理探讨.