Use of magnetic signatures to correlate tephra layers in Holocene loessial soil profiles from a small region, SE Iceland

Rock magnetic measurements have been applied to two adjacent loessial soil sections from a small region, SE Iceland. The soils are composed of reworked locally derived sediment (including airfall tephra) and also contain several visible discrete airfall tephra layers. The main magnetic minerals in the airfall tephras are ferrimagnetic (e.g. magnetite) with paramagnetic minerals also present. The main magnetic grain sizes in the tephras are pseudo single domain. The results show that individual tephras do not have unique magnetic signatures that can be used for identification and correlation between sedimentary sequences. However, a correlation of tephra layers was achieved through the application of statistical techniques to a comprehensive dataset of magnetic parameters. Similarity coefficients and Euclidian distance measures were used to identify the best correlation between tephra layers in the two soil profiles. The technique works well providing some tephras present within both profiles have been formally identified (e.g. Oraefajokulla ad 1362) using electron microprobe analyses. Given this initial framework, the statistical analyses of the magnetic parameters can help in the identification and correlation of unknown tephras between two soil profiles.     

城市地铁运营期间对地下水环境影响分析

长距离地铁隧道的运营期间会对地下水环境造成一定影响。本文以北京市M8二期北段为例,进行该类问题的分析研究,首次建立了科学的评价方法体系。根据本文的方法体系,在一定渗流计算的基础上,获得了北京市M8二期北段对渗流场阻隔作用的量化评价,并在此基础上做了进一步的环境及工程影响评价,评价结论为保证地下水环境和该新线建设节省造价和工期提供了科学依据。同时,本文工作也为今后地铁建设中类似问题的评价与研究提供方法上的借鉴与参考。     

Positive Ion Contained in Tamarix Cone Sedimentary Veins and Climatic and Environmental Change in Southern Region of Taklimakan Desert

Based on the research on Tamarix cone sedimentary veins in three different places which are Andier Ancient City, Andier Meadow, and Damagou Township in the southern region of the Taklimakan Desert, the relationship between the characteristics of the positive ion content in Tamarix fallen leaves and climatic change during the past 400 years is systematically analyzed. The results show: the order of four kinds of positive ion content’s change range in three sampling sites is Ca²⁺> K⁺> Mg²⁺> Na⁺. The correlation coefficient between Ca²⁺ content and the total positive ion content is higher, which indicates that Ca²⁺ content or the total positive ion content can reflect the change trends. There is an inverse correlation between positive ion content in Tamarix fallen leaves and the local temperature. According to the change of positive ion content, the climate in the southern region of the Taklimakan Desert can be divided into cold and warm periods during the past 400 years, among which the period of 1590-1691 is warm period, of 1692-1896 is cold period (warm fluctuations are 1799-1808,1825-1829,1878-1881,1887-1891), of 1897-2010 is warm period (cold fluctuations are 1939-1941,1992-1998); Precipitation has a poor correlation with the positive ion content; There is a better correspondence between the changes of positive ion content and the regional flood events. This research provides a kind of research method for the environmental evolution in the southern region of the Taklimakan Desert,and it is of great help to environmental change research of the arid desert regions. It has further perfected the feasibility of using positive ion content in Tamarix cone sedimentary veins to reveal the environmental change, and fills up the blank of high resolution climatic change during the past 400 years in the southern region of the Taklimakan Desert.     

泥河湾盆地晚新生代微体古生物地层及环境演化的探讨

通过对泥河湾盆地43条剖面和6个钻孔晚新生代地层和微体古生物(介形类和有孔虫)的调查研究,发现非常丰富的介形类,计26属70余种,有孔虫4属4种,其中介形类自下而上可明显地划分为5个组合带:(1)Potamocypris plana-Candoniella-Ilyocypris组合带;(2)Leucocythere-Ilyocypris-Candoniella组合带;(3)Leucocythere-Cytherissa-Limnocythere组合带;(4)Ilyocypris-Limnocythere flexa-Limnocythere dubiosa组合带;(5)Limnocythere dubiosa-Limnocythere sancti-Patricii-Ilyocypris组合带。按以上5个介形类组合带的分布,第1组合带及所含地层红崖村组和石匣组的时代为上新世;第2~4组合带及所含地层泥河湾组的时代为早更新世;第5组合带为中-晚更新世,分布于虎头梁组和许家窑组,虎头梁组置中更新世为宜,许家窑组为晚更新世。根据5个介形类组合带和有孔虫的分布及介形类的始现、繁盛、兴衰的演替特征,对泥河湾古湖和盆地的形成经历了上新世的起始,早更新世早期的扩展,中、晚期稳定、发展、湖面最大,中更新世向西部退缩和晚更新世消亡、桑干河水系形成五个发展阶段的演化进行了探讨。     

大溪河流域主要环境地质问题与土地功能区划分析

大溪河流域环境工程地质问题主要表现为地质灾害、岩溶、水土流失三方面,本文调查和分析了上述问题的基本特征、影响因素及对国土规划的影响;在此基础上,结合大溪河流域的特色,对流域进行了国土功能分区与适宜性评价,分为:林业经济区、农业经济区、河谷经济区三个大区,详细阐述各区环境地质问题及适宜性情况,为流域规划开发决策提供参考建议。     

Mineralogical and geochemical constraints on environmental impacts from waste rock at Taojiang Mn-ore deposit,central Hunan,China

The mineralogy and geochemistry of the waste rocks distributed at Taojiang Mn-ore deposit, central Hunan province, China, were studied using X-ray powder diffraction (XRD), electron microprobe analysis (EMPA) fitted with energy dispersive spectrometer (EDS) and inductively coupled plasma mass spectrum (atomic emission spectra) ICP-MS (AES), with the aim of predicting the environmental impacts of weathering of the waste rocks. The mineralogical results from microscope observation and XRD and EMPA studies show that the waste rock is composed of black shale and minor Mn carbonates. The oxidation of sulfide minerals such as galena, pyrite and chalcopyrite is accompanied by decomposition of Mn carbonates and K-feldspar during exposure to atmospheric O₂. The geochemical characteristics of major, rare earth elements (REE) and trace elements of the waste rocks also show that the waste rock can be divided into black shale and Mn carbonate, and both of them are currently under chemical weathering. The major alkalies and alkaline elements (Ca, Mg, Na, K, Rb, Sr and Cs) and major elements (Fe, S and P) and heavy metals (Sc, V, Cr, Th, U, Sn, Co, Ni, Cu, Zn, Pb, Mo, Cd, Sb, an Tl) are being released during weathering. The mobility of alkalis and alkaline elements Ca, Mg, Na, K, Rb, Sr and Cs is controlled by decomposition of Mn carbonates. The dispersion of Cr, Sc and Th (U) might be related to weathering of K-feldspar, and the release of the heavy metals Co, Ni, Cu, Zn, Pb, Mo, Cd Sb and Tl is dominated by the breaking of sulfide minerals. The REE of the waste rocks and surrounding soils and the spidery distribution patterns of heavy metals in the waste rocks, the surrounding soils and the surface waters show that weathering of the waste rocks and bedrock might be the sources of heavy metal contamination for the surrounding soils and surface water system for the mining area. This is predicted by the mass-balance calculation by using Zr as an immobile element. Therefore, it is urgently necessary take measures to treat the waste rocks distributed throughout the area for the local environmental protection.     

The importance of alternative conceptual models for simulation of concentrations in a multi-aquifer system

Four different conceptual models based on alternative geological interpretations were formulated for a shallow 600 km² aquifer system in Denmark comprising Quaternary deposits. Each of the four models was calibrated against groundwater heads and discharge measurements through inverse modeling. Subsequently, the transport capabilities of the four models were compared to 32 concentration measurements of environmental tracers (tritium ³H, helium-3 ³He, chlorofluorocarbons CFC11, CFC12 and CFC113). The flow simulations showed only minor differences in spatial head distribution associated with alternative conceptualizations despite the complexity of the aquifer system and the significant differences in geological interpretations. The models, however, showed major differences in predictions of the age of the groundwater and environmental tracer concentrations, differences that are seen as an effect of model structure uncertainty, because no additional calibrations to these data were performed. A single conceptualization may be adequate in characterizing the natural behavior of a field system after calibration, because the calibration procedure is able to compensate for errors in the data or in the conceptual model through biased parameter values. However, once extrapolation beyond the calibration base is attempted, different conceptual model formulations result in significantly different results. Consequently, it is crucial to take model conceptual uncertainty into account when making predictions beyond the calibration base.     

A critique of development and conservation policies in environmentally sensitive regions in Brazil

More than a strategy for environmental conservation, protected area paradigm has represented a specific conception of nature–society relationship. Originated in a context of capitalist consolidation, rapid urbanisation and frontier development in the US, this paradigm has given rise to a ‘politically viable rationale' in which utilitarian use of natural resources by tourism development would ensure nature preservation. This political rationality has deeply influenced environmental policies in developing countries, fostering a paradoxical model in the history of nature preservation. It also has brought into play diverse interests that have shifted patterns of local nature–society interaction, configuring a complex politicised environment. Established in ‘isolated' regions, protected areas have been implemented often by top–down approaches, disrupting resident peoples' livelihoods strategies through conflicts over the control of natural resources. Understanding the implications of development and conservation policies on resident peoples' livelihoods may represent a starting point for an integrated developmental conservation policy towards the promotion of sustainable livelihoods in environmentally sensitive regions in developing countries. These issues are analysed in the region of the Lençois Maranhenses National Park in Brazil. This paper argues that the context facing the region reveals a standardised conservationist paradigm marked by the absence of wider ecological criteria informing nature protection and a disregard for the strengthening of sustainability in existent socio-economic dynamics. The regional development and conservation policies have not only promoted tensions between resident peoples' livelihoods and the protected area paradigm, but also reinforced the legitimisation of social exclusion and environmental disruption under the prevalent rhetoric of nature protection and tourism development.     

湖南省农用土地的环境地质问题

湖南省农用土地的环境地质问题主要有两种类型，一种是受成土母岩的物理性状和化学组分的影响而产生的原生环境地质问题，另一种是受人类工程一经济活动及外动力作用影响而形成的次生环境地质问题，本文就其形成机制作了探讨，并结合农业产提出了可操作的防治措施。     

区域生态风险评价

生态风险评价是伴随着环境管理目标和环境观念的转变而逐渐兴起并得到发展的一个新的研究领域，它区别于生态影响评价的重要特征在于其强调不稳定性因素的作用，区域生态风险评价所涉及的风险源以及评价受体等都在区域内具有空间异质性，因而比一般生态风险评价更复杂。通过讨论区域生态风险评价的特点和方法论基础，对有关概念和评价的方法步骤进行了理论探讨。