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361.
We assessed the current status of tributyltin (TBT) contamination of Thais clavigera (Gastropoda) along the coastal area of Mirs Bay, China for the first time. The snail samples were collected from 10 different sites in the summer (June) and winter (December) of 2006, respectively. They were analyzed for imposex status, i.e. relative penis size index (RPSI) and vas deferens sequence index (VDSI), followed by quantification of butyltins in their tissues. Most of the collected females suffered from imposex, but the level of butyltin contamination varied with the distance from Yantian Port, which is currently the fourth busiest container port in the world. The tissue concentration of TBT varied with season. For a particular site, the winter samples in general contained much higher concentration of TBT than the summer samples. RPSI, VDSI and organotin concentrations were higher in T. clavigera collected from sites closer to the Port, such as the Seafood Street and Kat O. Both RPSI and VDSI were positively correlated with the tissue burden of tributyltin. VDSI exhibited little seasonal variability, whereas RPSI showed marked seasonal variability, with lower values in the summer samples. The current results will serve as an important reference for long-term monitoring of butyltin contamination in this area.  相似文献   
362.
Vibrator excitation generates not only reflections and refractions of wave fields on the subsurface interfaces but also electromagnetic waves with different frequencies. In this paper, we address the vibration-induced effects on the spontaneous potential field. The effects of controllable vibration on the spontaneous potential field were studied under real field geologic conditions. Experimental data confirmed that the vibration-induced effects on the spontaneous potential field do exist under field conditions. Monitoring records over a long time interval showed that there exist three information zones in the vibration-induced effects on the spontaneous potential field. These are the signal-varying zone, the extremestable zone, and the relaxation-recovery zone. Combined with different well-site data, it was concluded that the time-varying features of the anomalies in the information zones was closely related to the properties of the subsurface liquid (oil and water).  相似文献   
363.
Based on TM image data and other survey materials, this paper analyzed the spatiotemporal patterns of land use change in the Bohai Rim during 1985–2005. The findings of this study are summarized as follows: (1) Land use pattern changed dramatically during 1985–2005. Industrial and residential land in urban and rural areas increased by 643,946 hm2, of which urban construction land had the largest and fastest increase of 294,953 hm2 at an annual rate of 3.72%. (2) The outward migration of rural population did not prevent the expansion of residential land in rural areas by 184,869 hm2. This increase reveals that construction of rural residences makes seriously wasteful and inefficient use of land. (3) Arable land, woodland and grassland decreased at a rate of −0.02%, −0.12% and −1.32% annually, while unused land shrank by 157,444 hm2 at an annual rate of −1.69%. (4) The change of land use types showed marked fluctuations over the two stages (1985–1995 and 1995–2005). In particular, arable land, woodland and unused land experienced an inversed trend of change. (5) There was a significant interaction between arable land and woodland. Industrial construction land in urban and rural areas showed a net trend of increase during the earlier period, but only adjustment to its internal structure during the second period. The loss of arable land to the construction of factories, mines and residences took place mainly in the fringe areas of large and medium-sized cities, along the routes of major roads, as well as in the economically developed coastal areas in the east. Such changes are closely related to the spatial differentiation of the level of urbanization and industrialization in the region.  相似文献   
364.
Traditionally a streambed is treated as a layer of uniform thickness and low saturated hydraulic conductivity (K) in surface‐ and ground‐water studies. Recent findings have shown a high level of spatial heterogeneity within a streambed and such heterogeneity directly affects surface‐ and ground‐water exchange and can have ecological implications for biogeochemical transformations, nutrient cycling, organic matter decomposition, and reproduction of gravel spawning fish. In this study a detailed field investigation of K was conducted in two selected sites in Touchet River, a typical salmon spawning stream in arid south eastern Washington, USA. In‐stream slug tests were conducted to determine K following the Bouwer and Rice method. For the upper and lower sites, each 50 m long and 9 m wide and roughly 20 m apart, a sampling grid of 5 m longitudinally and 3 m transversely was used. The slug tests were performed for each horizontal coordinate at 0·3–0·45, 0·6–0·75, 0·9–1·05 and 1·2–1·35 m depth intervals unless a shallower impenetrable obstruction was encountered. Additionally, water levels were measured to obtain vertical hydraulic gradient (VHG) between each two adjacent depth intervals. Results indicated that K ranged over three orders of magnitude at both the upper and lower sites and differed between the two sites. At the upper site, K did not differ significantly among different depth intervals based on nonparametric statistical tests for mean, median, and empirical cumulative distribution, but the spatial pattern of K varied among different depth intervals. At the lower site, K for the 0·3–0·45 m depth interval differed statistically from those at other depth intervals, and no similar spatial pattern was found among different depth intervals. Zones of upward and downward water flow based on VHG also varied among different depth intervals, reflecting the complexities of the water flow regime. Detailed characterization of the streambed as attempted in this study should be helpful in providing information on spatial variations of streambed hydraulic properties as well as surface‐ and ground‐water interaction. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
365.
研究“十五”“地震应急指挥技术系统”中“地震应急指挥辅助决策系统”的一部分。主要研究“特大目标分类别的抢险设计方案和通用性建议模型”,它主要是为地震应急指挥提供辅助决策背景支持信息和特大目标分类别的抢险设计方案,通过检索和查询应急基础数据库,生成专题图表,显示特大目标的相关信息,并结合灾区实际情况,为指挥部成员提供提醒性的决策参考信息。  相似文献   
366.
通过“十五”改造,浙江省目前有地震地下流体观测台站5个,10项测项,主要是水位,水温和水氡。在2008年5月12日四川汶川8.0级地震中有明显映震效应的台站为100%,测项为80%。水氡测值表现为临震向上突跳异常,最大异常幅度达23.7%,创历史之最;水温测项主要出现临震突跳或阶跃;水位测项主要是同震效应现象,为水震波引起的脉冲和阶跃变化。认为同震效应可能是地震发生后地震波传播引起的含水层弹性形变所致。并且认为观测效果不一定是井位越深越好,而是要看含水层封闭情况和仪器观测传感器的位置,没有明显的优劣之分。好的静水位观测井记录的水震波效果明显优于动水位观测井。由于前兆数字化仪器采样率相对较底(1次/min),记录数据缺失较多,记录的同震变化波形不完整,很难进一步分析。  相似文献   
367.
In situ LA-ICPMS U-Pb, trace element, and Hf isotope data in zircon demonstrate a Carboniferous age for eclogite-facies metamorphism in Siluro-Devonian protoliths in the Huwan shear zone, Dabie Mountains, Central China. This age contrasts with the more prevailing Triassic age for high- to ultrahigh pressure (HP to UHP) metamorphism in the Qinling-Dabie-Sulu orogen. Metamorphic zircon in two eclogite samples from Sujiahe is characterized by low Th/U ratios, small negative Eu anomalies, flat HREE patterns, and low 176Lu/177Hf ratios. These geochemical signatures suggest that the zircon crystallized in the presence of garnet and in the absence of plagioclase feldspar. Furthermore, temperatures of ~ 655 and ~ 638 °C, calculated using the Ti content of zircon, are consistent with their formation during eclogite-facies metamorphism. The weighted mean 206Pb/238U age of 309 ± 4 Ma (2δ) for this zircon improves previous age estimates for eclogite-facies metamorphism in the Huwan shear zone, ranging from 420 to 220 Ma. Metamorphic zircon from one eclogite sample from Hujiawan, most likely formed during prograde metamorphism, yields an equivalent age estimate of 312 ± 11 Ma. Magmatic zircon cores in the three samples yield ages for the magmatic protoliths of the eclogites ranging from 420 ± 7 to 406 ± 5 Ma, and post-dating the middle Paleozoic collision of the North China and the Qinling terrain. The zircon crystals in the three eclogite samples display a large variation of εHf (t) values of ? 4.9 to 21.3. The metamorphic zircon overgrowths show the same range of εHf (t) values as those of the inherited magmatic crystal interiors. This suggests that the metamorphic zircon overgrowths may have formed by dissolution-reprecipitation of pre-existing magmatic zircon thereby preserving their original Hf isotopic composition. The high εHf (t) values suggest that the protoliths were derived from depleted mantle sources, most likely Paleotethyan oceanic crust; while the low εHf (t) values are attributed to crustal contamination. Some eclogites in the Huwan shear zone have a distinctive signature of continental crust most probably derived from the Yangtze Craton. The coexistence of Paleozoic oceanic crust and Neoproterozoic continental crust with similar metamorphic ages in the Huwan shear zone implies that Paleozoic Paleotethyan oceanic crust was produced within a marginal basin of the northern Yangtze Craton. The opening of the Paleo-Tethyan ocean was slightly younger than the collision of the North China Craton and the Qinling terrain during the Late Paleozoic in the Qinling-Dabie-Sulu orogen. Subduction of the Paleo-Tethyan oceanic crust and associated continental basement resulted in the 309 ± 2 Ma (2σ) eclogite-facies metamorphism in the Huwan shear zone. The subsequent Triassic continent-continent collision led to the final coalescence of the Yangtze and Sino-Korean cratons. Amalgamation of the Yangtze and North China cratons was, therefore, a multistage process extending over at least 200 Ma.  相似文献   
368.
王强  邱家骧 《地质学报》2000,74(1):63-71
本文以北大别地块中典型燕山期花岗岩--天堂寨、九资河花岗岩为例,研究了其黑云母、角闪石的矿物成分及岩石包体特征;并结合当前有关脱水熔融和含自由水体系的熔融实验岩石学成果,对花岗质岩浆的形成方式进行了讨论,认为天堂寨、九资河花岗岩是由含自由水体系的熔融作用形成的,含水流体的主要来源可能为南大别地块。  相似文献   
369.
本文以北大别地块中典型燕山期花岗岩——天堂寨、九资河花岗岩为例,研究了其黑云母、角闪石的矿物成分及岩石包体特征;并结合当前有关脱水熔融和含自由水体系的熔融实验岩石学成果,对花岗质岩浆的形成方式进行了讨论,认为天堂寨、九资河花岗岩是由含自由水体系的熔融作用形成的,含水流体的主要来源可能为南大别地块。  相似文献   
370.
多普勒雷达资料对中尺度系统短期预报的改进   总被引:51,自引:9,他引:42  
邱崇践  余金香  QinXu 《气象学报》2000,58(2):244-249
文中给了一种由单多普勒雷达资料反演风矢量场的变分方法 ,并由此形成预报初始场。运用美国风暴分析预报中心 ( CAPS)的改进的区域系统模式对移经美国俄克拉何马州的一个强雷暴系统进行了数值预报试验 ,结果表明 ,初始场中引入多普勒雷达观测资料后明显地改进了预报。  相似文献   
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