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981.
?о???????????η????????????????С???????÷??????3??2°×2°?????????к????????????????????????????????????????????С???????÷??????????????????????????????????????????????????????????FFT????????????????????????С???????÷?????????????ε????????????????????η????????ì???????????????????????????????????????????????????????????Σ??????????????????????????????μ?????????? 相似文献
982.
983.
利用实时多普勒天气雷达、边界层风廓线雷达和自动站资料对超强台风“威马逊”第4次登陆广西沿海时台风结构的演变特征进行研究,结果表明:台风眼区气压呈“漏斗”形变化,具有气压低、风速弱、空气干而暖的特征;登陆过程中眼区保持圆形,半径约为30 km,是典型强台风结构;天气雷达径向速度大风区具有非对称性,右象限大于左象限;风廓线雷达水平风场能够精确、直观地描述台风不同部位经过测站时的垂直结构特征,从低层到高层风向先后经历了“东北风—东风—东南风—南风”的转变过程,风速整体上呈现随高度先增大后减小的特点,其垂直速度和大气折射率结构常数(C2n)能够很好地反映台风的结构及其云和气流的变化特征;两种雷达风场产品的风向一致,但是VWP产品的风速比风廓线雷达的要小,VWP产品出现无效数据时,可以用风廓线雷达产品作为补充。 相似文献
984.
印度洋Carlsberg洋脊玄武岩岩石地球化学特征及其地质意义 总被引:2,自引:0,他引:2
本文对采自印度洋Carlsberg脊14个站位的新鲜玄武岩样品进行了常量和微量元素组成分析,旨在研究岩浆源区地幔的性质以及岩浆作用过程。研究结果表明:该区玄武岩为典型的源于亏损型地幔的大洋中脊玄武岩,不同样品经历了不同程度的结晶分异作用,演化过程主要受控于橄榄石的结晶分异作用,部分样品中有单斜辉石结晶分异作用的影响,斜长石的结晶分异作用不显著;玄武岩岩浆来源于亏损型尖晶石二辉橄榄岩地幔的熔融,主微量元素组成中尚未见到富集型组分混入的证据;源区地幔不同比例的熔融作用及其后岩浆演化过程的差异是造成不同样品间地球化学性质差异的主要原因,彼此独立的局部岩浆作用过程是岩浆作用差异的主控制因素。Carlsberg脊玄武岩整体与全球标准大洋中脊玄武岩(N-MORB)平均组分相近,不同脊段间岩浆源区地幔的组成、熔融程度(比例)和熔融深度等无明显差异,这种特征向南直到CIR的北段。 相似文献
985.
In order to discuss the content distributions and fluxes of heavy metals in suspended matters during a tidal cycle in the turbidity maximum around the Changjiang(Yangtze) Estuary,the contents of heavy metals(Zn,Pb,Cd,Co and Ni) have been analyzed.During a tidal cycle,the average contents of heavy metals are in the order of ZnNiPbCo àCd.The average contents in ebb tide are generally higher than that in flood tide.However,at the inshore Sta.11,influenced by the contamination from the nearby waste treatment plant,the average contents of Zn and Ni in flood tide are higher than those in ebb tide and at the offshore Sta.10,the content of Cd in flood tide higher than that in ebb tide due to marine-derived materials.The five heavy metals,mainly terrigenous,are transported towards east-northeast,and settle down with suspended matters in the area between Sta.11 and Sta.10.Influenced by marine-derived materials,the flux value of Cd does not alter significantly with obviously changing in flux direction towards northwest.The source of heavy metals,the salinity of water and the concentration of suspended matters are the main factors controlling the content distributions of heavy metals during a tidal cycle.There is a positive correlation between the contents of heavy metals(Zn,Pb,Co and Ni) and the salinity of water,while the opposite correlation between the contents and the concentrations of suspended matters.Because of marine-derived materials,the content of Cd is not correlated with the concentration of suspended matters and the salinity of water. 相似文献
986.
987.
988.
The contents of Pb, Cd, Cr, As, and Hg was investigated in the neighboring areas of a lead smelting enterprise and the metals contamination of soil was evaluated with the methodologies of the single factor index and Nemerow integrated index. It is found that the content of heavy metals in the neighboring areas has no obvious difference from the reference points. And the soil contamination of heavy metals varies by elements, the contamination index follows the pollution order: Cd〉Hg〉Cr〉As〉Pb. The pollution degree of Cd is at high level and Hg at low level, but Cr and As reached the warning level. Therefore, the lead smelting enterprises should not only control lead but also other heavy metals as Cd. 相似文献
989.
Late Paleozoic retrograded eclogites from within the northern margin of the North China Craton: Evidence for subduction of the Paleo-Asian ocean 总被引:4,自引:1,他引:3
Retrograded eclogites from the central part of the northern margin of the North China Craton, Hebei Province, China occur as separate tectonic lenses or boundins within garnet–biotite–plagioclase gneisses of the Paleoproterozoic Hongqiyingzi Complex characterized by amphibolite facies paragneisses. The petrographic features and mineralogical compositions represent three main metamorphic stages: (1) the peak eclogite facies stage (P > 1.40–1.50 GPa, T = 680–730 °C), (2) the granulite facies stage and (3) the amphibolite facies stage (P = 0.67–0.81 GPa, T = 530–610 °C) formed during decompression. The major and trace element and Sm–Nd isotopic data suggest that most of the retrograded eclogite samples had protoliths of tholeiitic oceanic crust with geochemical characteristics of mid-ocean ridge basalt (MORB) or island arc tholeiite (IAT) environment, and were contaminated by crustal components during subsequent subduction. Zircon SHRIMP isotopic dating of two different textural varieties of retrograded eclogite defines a weighted mean age of 325 Ma, which is interpreted as the peak metamorphic age of the eclogites and reflects the occurrence of eclogite facies metamorphism related to subduction of Paleo-Asian Oceanic crust beneath the North China Craton during the Late Paleozoic. Finally, we show that the retrograded eclogite from Hebei Province is not related to the Baimashi retrograded eclogite at the northern foot of the Heng Mountains, approximately, 300 km to the southwest. 相似文献
990.
Nano-sized zinc oxide (nZnO) particles are one kind of the most commonly used metal oxide nanoparticles (NPs). This study compared the cytotoxic and embryotoxic effects of three increasing sized ZnO particles (? 30 nm, 80-150 nm and 2 μm) in the flounder gill (FG) cells and zebrafish embryos, and analyzed the contribution of size, agglomeration and released Zn2+ to the toxic effects. All the tested ZnO particles were found to be highly toxic to both FG cells and zebrafish embryos. They induced growth inhibition, LDH release, morphological changes and apoptosis in FG cells in a concentration-, size- and time-dependent manner. Moreover, the release of LDH from the exposed FG cells into the medium occurred before the observable morphological changes happened. The ultrasonication treatment and addition of serum favored the dispersion of ZnO particles and alleviated the agglomeration, thus significantly increased the corresponding cytotoxicity. The released Zn2+ ions from ZnO particles into the extracellular medium only partially contributed to the cytotoxicity. All the three sizes of ZnO particles tested induced developmental malformations, decrease of hatching rates and lethality in zebrafish embryos, but size- and concentration- dependent toxic effects were not so obvious as in FG cells possibly due to the easy aggregation of ZnO particles in freshwater. In conclusion, both FG cells and zebrafish embryos are sensitive bioassay systems for safety assessment of ZnO particles and the environmental release of ZnO particles should be closely monitored as far as the safety of aquatic organisms is concerned. 相似文献