Developmental,Reproductive, and Demographic Alterations in Aquatic Wildlife: Establishing Causality between Exposure to Endocrine‐active Compounds (EACs) and Effects     

Helmut Segner 《洁净——土壤、空气、水》2005,33(1):17-26

This brief overview discusses the difficulty of demonstrating causal associations between exposure to endocrine active compounds (EACs) and the occurrence of developmental, reproductive, or demographic disturbances in aquatic wildlife. While for biological responses at the suborganism level correlational or causal evidence of an EAC etiology has been established in a number of cases, well proven examples of ecological consequences of endocrine disruption are rather few in number. The attribution of causality is complicated due to (i) lack of data on EAC exposure and bioaccumulation, (ii) lack of specific biomarkers and endpoints, together with insufficient knowledge on the mechanisms and conditions by which EAC‐induced disruption of endocrine functions translates into impaired organism development and reproduction, and (iii) insufficient understanding of the importance of species diversity in endocrine physiology and life histories for the consequences of endocrine disruption. Future research should address these gaps in our understanding of EAC exposure and effects, but additionally needs to pay more attention (i) to ecological determinants influencing the population‐level consequences of the endocrine disruption of developÍmental and reproductive functions, and (ii) to the use of epidemiological principles and approaches.  相似文献   

抚顺石油一厂地表变形初步探讨   总被引：4，自引：0，他引：4  

李树德 《工程地质学报》1996,4(2):31-35

石油一厂地表变形的主要因素是西露天矿露天台阶开采, 引起厂南缘边坡失稳、变形和地面沉陷, 同时促使其它因素活化, 更加剧了地裂缝和变形发展。  相似文献   

Garnet evolution in pre-Variscan pelitic rocks from the Lake Emosson area, Aiguilles Rouges Massif, Western Alps   总被引：1，自引：0，他引：1  

JÜRGEN F. VON RAUMER  HANS W. SCHWANDER 《Journal of Metamorphic Geology》1985,3(4):467-479

Abstract The chemical evolution of garnets from pelitic rocks of probable Palaeozoic age corresponds to a complex metamorphic evolution of the host rocks.
Among the almandine-rich garnets (Alm_60–80), two main types of evolution can be distinguished. Early Mn-rich garnets coexisting with kyanite may be replaced by plagioclase and then, during a late stage, by biotite and/or sillimanite. The second type of evolution corresponds to an overgrowth of Mn-poor late-stage garnet on older Mn-rich garnets which corresponds to a thermal peak with sillimanite-type of metamorphism. This new garnet may appear either as an overgrowth with a strong discontinuity, or as small, new euhedral garnet or as skeletal garnet.
This chemical evolution of garnet corresponds to an early collisional stage of metamorphism (of high pressure type with high Mn values) of probable Ordovician age followed by uplift and a thermal peak (low Mn values) in Devonian times.  相似文献   

短期气候预测的现状 问题与出路(一)   总被引：4，自引：0，他引：4  

丑纪范 《沙漠与绿洲气象(新疆气象)》2003,26(1):1-4

从方法论上分析了短期气候预测的现状、问题与出路。着重指出：基础理论研究的欠缺又不甚得法是短期气候预测准确率提高缓慢的原因；应当将数值预报的提法从初值问题改为演变问题，进一步提为反问题；统计学方法与动力学方法要相互借鉴，取长补短，融合发展。  相似文献   

实验室仪器设备的日常运行检查及检查结果的评价     

胡九根 《矿产与地质》2002,16(6):381-383

对实验室需要参加运行检查的仪器设备进行了确认 ,制定了运行检查的方法 ,并介绍了运行检查结果的评价方法。  相似文献   

Metamorphism of the Central Anatolian Crystalline Complex, Turkey: influence of orogen-normal collision vs. wrench-dominated tectonics on P–T–t paths     

D. L. Whitney  C. Teyssier  Y. Dilek  A. K. Fayon 《Journal of Metamorphic Geology》2001,19(4):411-432

The Central Anatolian Crystalline Complex (CACC) is a microcontinent in the Alpine–Himalayan belt. It has previously been considered as a coherent structural entity, but, although the entire CACC is comprised of similar rocks (primarily metasedimentary rocks and granitoids), it consists of at least four tectonic blocks characterized by different <i>P</i>–<i>T</i>–<i>t</i> paths. These blocks are the K?r?ehir (north‐west), Akda? (north‐east), Ni?de (south) and Aksaray (west) massifs. The northern massifs experienced thrusting and folding during collision and were slowly exhumed by erosion; metamorphic rocks are characterized by clockwise <i>P</i>–<i>T</i> paths at moderate <i>P</i>–<i>T</i> and local low‐<i>P</i>–high‐<i>T</i> (LP–HT) overprinting in the highest grade rocks. Apatite fission track ages are Eocene to Oligocene (47–32 Ma). The Aksaray block represents the hot, shallow mid‐crust of a Late Cretaceous–early Tertiary arc. It is dominated by intrusions; rare metapelitic rocks record low‐<i>P</i> (< 4 kbar) regional metamorphism overprinted by LP–HT contact metamorphism. Apatite fission track ages are 50–45 Ma. The Ni?de massif is different from the other CACC blocks because it evolved as a core complex in a wrench‐dominated setting. It is characterized by clockwise <i>P</i>–<i>T</i> paths at moderate <i>P</i>–<i>T</i> followed by widespread LP–HT metamorphism. Apatite fission track ages are Miocene (12–9 Ma), significantly younger than those in the northern massifs. Ni?de rocks resided in the mid‐crust at a time when the rest of the CACC was at or near the Earth's surface. Variations in <i>P</i>–<i>T</i>–<i>t</i> and tectonic histories — especially timing of exhumation — between the northern and southern CACC reflect the difference between head‐on collision vs. mid‐crustal wrenching.  相似文献   

Analysis of karst hydrodynamics through comparison of dissolved and suspended solids' transport     

Danièle Valdes  Jean-Paul Dupont  Nicolas Massei  Benoît Laignel  Joël Rodet 《Comptes Rendus Geoscience》2005,337(15):1365-1374

In karst systems, rain events often result in a decrease of the conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. This study shows that the comparison of suspended solids and solute transport by the coupled approach of <math><mi is="true">T</mi><mtext is="true">–</mtext><mi is="true">C</mi></math> curves (Turbidity–Conductivity) and autocorrelations gives evidence of the transport processes in the karst network and allows understanding the karst hydrodynamics. <strong><em>To cite this article: D. Valdes et al., C. R. Geoscience 337 (2005).</em></strong>  相似文献   

On the sand surface stability in the southern part of Gurbantünggüt Desert     

Wang?Xueqin?Email author  Tao?Wang  Jin?Jiang  Congju?Zhao 《中国科学D辑(英文版)》2005,48(6):778-785

Longitudinal dunes are the most widespread dune types in the world sand seas but comprehensive study on the sand surface stability is scarce. The southern part of Gürbantünggüt Desert is mainly covered by longitudinal dune in which fixed and semi-fixed dunes occupy over 80% of the total area. Systematic analysis on the climatic conditions, the soil moisture and vegetation distributions, and the sand surface activities showed that the fixed and semi-fixed dunes are in a comprehensive low-energy wind environment. Snow cover and frozen soil provide a good protection to the ground surface in winter. The temporal distribution of precipitation and corresponding variation of temperature create a favorable condition for the desert plants growth, especially for the ephemeral plants. The occurrence of effective winds for sand moving in April to June coincides with the stage of relatively wet sand surface and good vegetation cover, which effectively keep the sand surface stable at the interdune and the plinth of the dunes. Activity sand surface appears only at the crest and the upper part of the sand dunes.  相似文献   

Thermobarometry and P–T–t paths: the granulite to eclogite transition in lower crustal xenoliths from eastern Australia     

N. J. PEARSON  S. Y. O'REILLY 《Journal of Metamorphic Geology》1991,9(3):349-359

‘Lower crustal’ suite xenoliths in basaltic and kimberlitic magmas are dominated by mafic granulites and may also include eclogites and garnet pyroxenites. Pressures of up to 25 kbar obtained from such xenoliths are well in excess of an upper value of <i>c.</i> 12 kbar for exposed granulite terranes. Palaeogeotherms constructed from xenoliths for the lower crust beneath the Phanerozoic fold belts of eastern Australia (SEA) and beneath the eastern margin of the Australian craton (EMAC) indicate two distinct thermal regimes. The two geotherms have similar form, with the EMAC curve displaced <i>c.</i> 150°C to lower temperatures. Reaction microstructures show the partial re-equilibration of primary igneous assemblages to granulite and eclogite assemblages and are interpreted to reflect the cooling from magmatic temperatures. Variations in mineral compositions and zoning are used to constrain further the history of several EMAC xenoliths to near-isobaric trajectories. Detailed graphical models are constructed to predict compositional changes for isobaric <i>P–T</i> paths (at 7, 14 & 21 kbar) to transform an SEA-type geotherm to a cratonic geotherm. The models show that for the assemblage grt + cpx ± ky + plag + qtz, the changes associated with falling temperature in <i>X</i><sub>gr</sub>, <i>X</i><sub>jd</sub> (increase) and <i>X</i><sub>an</sub> (decrease) will be greater at higher pressures. These results indicate that discernible zoning is more likely to be preserved in the higher pressure xenoliths. The zoning recorded in clinopyroxene from mafic granulite xenoliths over the pressure range <i>c.</i> 12–22 kbar suggests isobaric cooling of a large crustal thickness (30–35 km). An isobaric cooling path is consistent with magma accretion models for the transition of a crust–mantle boundary from an SEA-type geotherm to a cratonic geotherm. The coexistence of granulite and eclogite over the depth range 35–75 km beneath the EMAC indicates that the granulite to eclogite transition in the lower crust is controlled by <i>P–T</i> conditions, bulk chemistry and kinetic factors. At shallower crustal levels, typified by exposed granulite terranes, isobaric cooling may not result in the transition to eclogite.  相似文献   

Contact metamorphic P–T–t paths from Sm–Nd garnet ages, phase equilibria modelling and thermobarometry: Garnet Ledge, south-eastern Alaska, USA     

H. H. Stowell  D. L. Taylor  D. L. Tinkham  S. A. Goldberg  K. A. Ouderkirk 《Journal of Metamorphic Geology》2001,19(6):645-660

Sm–Nd garnet‐whole rock geochronology, phase equilibria, and thermobarometry results from Garnet Ledge, south‐eastern Alaska, provide the first precisely constrained <i>P–T–t</i> path for garnet zone contact metamorphism. Garnet cores from two crystals and associated whole rocks yield a four point isochron age for initial garnet growth of 89.9 ± 3.6 Ma. Garnet rims and matrix minerals from the same samples yield a five point isochron age for final garnet growth of 89 ± 1 Ma. Six size fractions of zircon from the adjacent pluton yield a concordant U–Pb age of 91.6 ± 0.5 Ma. The garnet core and rim, and zircon ages are compatible with single‐stage garnet growth during and/or after pluton emplacement. All garnet core–whole rock and garnet rim‐matrix data from the two samples constrain garnet growth duration to ≤5.5 my. A garnet mid‐point and the associated matrix from one of the two garnet crystals yield an age of 90.0 ± 1.0 Ma. This mid‐point result is logically younger than the 90.7 ± 5.6 Ma core–whole rock age and older than the 88.4 ± 2.5 Ma rim‐matrix age for this sample. A MnNaCaKFMASH phase diagram (<i>P–T</i> pseudosection) and the garnet core composition are used to predict that cores of garnet crystals grew at 610 ± 20 °C and 5 ± 1 kbar. This exceeds the temperature of the garnet‐in reaction by <i>c.</i> 50 °C and is compatible with overstepping of the garnet growth reaction during contact metamorphism. Intersection of three reactions involving garnet‐biotite‐sillimanite‐plagioclase‐quartz calculated by THERMOCALC in average <i>P–T</i> mode, and exchange thermobarometry were used to estimate peak metamorphic conditions of 678 ± 58 °C at 6.1 ± 0.9 kbar and 685 ± 50 °C at 6.3 ± 1 kbar, respectively. Integration of pressure, temperature, and age estimates yields a pressure‐temperature‐time path compatible with near isobaric garnet growth over an interval of <i>c.</i> 70 °C and <i>c.</i> 2.3 my.  相似文献