The influence of global sea surface temperature variability on the large-scale land surface temperature     

Nicholas L. Tyrrell  Dietmar Dommenget  Claudia Frauen  Scott Wales  Mike Rezny 《Climate Dynamics》2015,44(7-8):2159-2176

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Groundwater recharge in an arid grassland as indicated by soil chloride profile and multiple tracers          下载免费PDF全文

Tianming Huang  Zhonghe Pang  Jilai Liu  Lihe Yin  W. Mike Edmunds 《水文研究》2017,31(5):1047-1057

Previous studies have shown that shallow groundwater in arid regions is often not in equilibrium with near‐surface boundary conditions due to human activities and climate change. This is especially the case where the unsaturated zone is thick and recharge rate is limited. Under this nonequilibrium condition, the unsaturated zone solute profile plays an important role in estimating recent diffuse recharge in arid environments. This paper combines evaluation of the thick unsaturated zone with the saturated zone to investigate the groundwater recharge of a grassland in the arid western Ordos Basin, NW China, using the soil chloride profiles and multiple tracers (²H, ¹⁸O, ¹³C, ¹⁴C, and water chemistry) of groundwater. Whereas conventional water balance and Darcy flux measurements usually involve large errors in recharge estimations for arid areas, chloride mass balance has been widely and generally successfully used. The results show that the present diffuse recharge beneath the grassland is 0.11–0.32 mm/year, based on the chloride mass balance of seven soil profiles. The chloride accumulation age is approximately 2,500 years at a depth of 13 m in the unsaturated zone. The average Cl content in soil moisture in the upper 13 m of the unsaturated zone ranges from 2,842 to 7,856 mg/L, whereas the shallow groundwater Cl content ranges from 95 to 351 mg/L. The corrected ¹⁴C age of shallow groundwater ranges from 4,327 to 29,708 years. Stable isotopes show that the shallow groundwater is unrelated to modern precipitation. The shallow groundwater was recharged during the cold and wet phases of the Late Pleistocene and Holocene humid phase based on palaeoclimate, and consequently, the groundwater resources are nonrenewable. Due to the limited recharge rate and thick unsaturated zone, the present shallow groundwater has not been in hydraulic equilibrium with near‐surface boundary conditions in the past 2,500 years.  相似文献   

A secondary sludge flow hazard induced by shallow-source seismic activity in karst mining area,Guangxi, South China: localized karstification in anticline     

Zhiyong Li  Xiguang Li  Adil S. Mohammed  Mike Vorkink  Xiaomin Yan 《Natural Hazards》2016,83(1):75-95

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雪宝顶区块流域钙华形成的生物作用研究     

董发勤  李刚  代群威  周琳  王富东  赵学钦  蒋忠诚  张强  李博文  Enrico Capezzuoli  Mike O''Driscoll  Andelka Plenkovic-Moraj 《中国岩溶》2021,40(1):11-18

钙华不仅具有重要的景观旅游价值,而且对确定区内碳酸盐沉积特征、环境演化规律及同期环境生物的作用与贡献有重要的研究意义。本文在对比国内外典型钙华特征的基础上,以黄龙和九寨沟为例,对雪宝顶区块流域内钙华的沉积特征、环境化学与生物作用进行阐述,指出了雪宝顶区块流域冷水型钙华的形成与演化是化学沉积-溶解作用、生物沉积与溶蚀作用等共同作用的结果,并受非生物、生物因素影响。在雪宝顶冷水型钙华的形成过程中,微生物协同参与了钙华的沉积与溶蚀过程,通过自身新陈代谢促活动促使使钙离子结晶,并诱导晶型变化;其他生物体如植物、藻类等或以间接的方式促进或加快了钙华形成,或为钙华生长提供模板和体量。   相似文献   

钙华体次生有机体系的界面结晶作用研究     

董发勤  陈禹衡  代群威  郑飞  刘明学  蒋忠诚  张强  李博文  Alper Bab  Mike O''Driscoll  Andelka Plenkovic-Moraj 《中国岩溶》2021,40(1):34-43

本文总结了钙华体次生有机体系中生物群落特征和界面结晶行为,根据生物在碳酸盐沉积中的角色,将钙华体中次生有机体系的界面结晶矿化类型分为生物控制矿化沉积和生物诱导矿化沉积。分述了碳酸钙沉积矿化相关的五种生物代谢活动,讨论了生物胞外聚合物（EPS）对碳酸钙矿物晶型和形貌的影响。针对目前钙华研究中存在的问题,今后应深入研究生物体主要构成元素、生物小分子和生物体内部组织在钙华形成或退化中的作用,进一步厘清钙华体与次生有机体系的多界面溶化方式,为钙华保护修复及钙华退化治理措施提供科学依据。   相似文献   

Natural aggregates in the performance and durability of concrete: chemical characteristics     

Peter G. Fookes  Mike J. Walker 《Geology Today》2012,28(1):20-25

This article continues from the earlier feature in Geology Today (2011, v.27, n.4) and looks at the influence of chemical reactivity within concrete due to the presence of unsound aggregates or deleterious material incorporated in the aggregate used in the concrete mix. Some of the more disruptive problems from chemical unsoundness come from the presence of chlorides, which cause rusting in reinforced concrete or, sulphate attack from ground waters. Both of these reactions are relatively common in Britain. Alkali–silica reactions with aggregates and cement is not too prevalent in Britain but can be very prevalent and disruptive elsewhere in the world.  相似文献   

Field Comparison of Micropurging vs. Traditional Ground Water Sampling     

Peter M. Kearl  Nic E. Korte  Mike Stites  Joe Baker 《Ground Water Monitoring & Remediation》1994,14(4):183-190

Micropurge sampling of ground water wells has been suggested as a possible replacement to traditional purge and sample methods. To compare methods, duplicate ground water samples were collected at two field sites using iraditional and micropurge methods. Samples were analyzed for selected organic and inorganic constituents, and the results were compared statistically. Analysis of the data using the nonparametric sign test indicates that within a 95 percent confidence interval, there was no significant difference between the two methods for the site contaminants and the majority of analytes. These analytical results were supported by visual observations with the colloidal borescope, which demonstrated impacts on the flow system in the well when using traditional sampling methods. Under selected circumstances, the results suggest replacing traditional sampling with micropurging based on reliability, cost, and waste minimization.  相似文献   

Coseismic crustal deformation from microseismicity in the Patras area, western Greece     

Nikolaos S. Melis  Paul W. Burton  Mike Brooks 《Geophysical Journal International》1995,122(3):815-836

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River stabilisation due to changing climate and vegetation during the late Quaternary in western Tasmania, Australia     

Gerald C. Nanson  Mike Barbetti  Gillian Taylor 《Geomorphology》1995,13(1-4)

The Stanley River in western Tasmania, Australia, contains sub-fossil rainforest logs within the channel and floodplain. Of the more than 85 radiocarbon dates obtained, all but 3 date from 17 ka to the present and permit an interpretation of fluvial and related environmental changes over this period. Particular attention is focused on the interactive relationship between the river and its riparian rainforest. Following the Last Glacial Maximum, the Stanley River was a laterally active gravel-load system reworking most of its valley floor in the upstream reaches. With ameliorating conditions at the end of the Pleistocene, climate became less seasonal and flow regimes less energetic. Huon pines already present in the catchment, re-asserted themselves in the form of dense tree cover along the river banks and floodplains with basal floodplain deposition shifting from gravels to coarse sands and granules. By about 3.5 ka, a further change in climate reduced stream discharges substantially. As a result the channel reduced in size, transported finer sediment, became laterally stable, and the floodplain accreted with overbank deposits of sand and silt. Huon pines falling into the channel formed obstructions of woody debris, some surviving for 2 ka. These have reduced stream power and boundary shear stress, further contributing to channel stability. Generational sequences of Huon pines on the river banks, some extending back 1–2 ka, are additional evidence of this stability. Since the Pleistocene, changing climate and the re-establishment of dense riparian rainforest appear to have stabilised the river channels and floodplains of western Tasmania.  相似文献   

Quantitative fluorescence microscopy: by F.W.D. Rost. Cambridge University Press, 1991, 236 pp.     

Mike Barer 《International Journal of Coal Geology》1994,26(3-4)

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