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181.
182.
环境样品中痕量元素的化学形态分析Ⅱ.砷汞镉锡铅硒铬的形态分析 总被引:2,自引:6,他引:2
环境中元素的生物有效性和毒性依赖于其存在的化学形态。文章依据文献的有关报道介绍砷、汞、镉、锡、铅、硒和铬在环境中的分布、毒性及它们在环境样品如水、土壤、沉积物和生物体中的形态分析方法,包括分析物的保存、提取、分离和检测。引用文献120篇。 相似文献
183.
用超声技术提取沉积物样品中松散结合态磷,并与振荡提取结果进行比较。结果表明,超声提取结果与振荡提取结果大致相当。超声提取耗时短,操作简单易行,测试结果精密度为3.8%(RSD,n=7),可以替代振荡方法提取沉积物中的松散结合态磷。 相似文献
184.
185.
东海陆缘(闽北段)晚第四纪沉积的硅藻学研究 总被引:10,自引:1,他引:10
对东海陆缘 (闽北段 )晚第四纪沉积 4口钻井岩心进行系统的硅藻分析研究,获得丰富的硅藻化石,共发现硅藻 117种和变种,分属于 33个属。根据剖面硅藻组合特征变化,结合最优分割法和对应序分法的计算机运算结果,可以详细划分为 12个硅藻带,自下而上为 :1.Cascinodiscusargus-Cos.wittiomus-Cyclotellastriata硅藻带,2.Cos.blandus-Cyclotellastriata硅藻带,3.Cos.excentricus-Trbliepteychuscocconiformis硅藻带,4.Gomphonema-Cos.blandus-Actnolychusralfsii硅藻带,5.Cos.-Cyclotellastriata-Actinocyclusralfsii硅藻带,6.Cos.-Actinolychusralfsii硅藻带,7.贫乏硅藻带,8.Cos.lineatus-Cos.rothii-Actinolyclusralfsii硅藻带,9.Gomphonema-Cyclotellastriata-Cocconeisplacentulavareuglypta硅藻带,10.Cos.rothii-Cyclotellastriata-Actinolychusralfsi,11.Cymbel laaffinis-Cyclotellastriata-Gomphonema硅藻带,12.Coscinodiscuswittinus-Cyclotellastriata-Epithemiahynd manii硅藻带,建立了该区晚第四纪硅藻组合序列,并探讨其相应的古环境演变。 相似文献
186.
Scott Lamoureux 《地球表面变化过程与地形》2002,27(10):1107-1124
A 487‐year annually laminated (varved) sediment record from Nicolay Lake, Cornwall Island, in the Canadian High Arctic was evaluated to determine the impact that years with high sediment yields had on sediment yields in subsequent years. All of the 40 largest years showed evidence for increased sediment yield in the subsequent 10–30 years. The positive anomalies in lagging years were approximately scaled according to the size of the initiating year, although many intermediate years (25‐ to 100‐year recurrence) showed weak or variable responses. The smallest events considered (10‐ to 25‐year recurrence) showed a consistent, but low‐amplitude response. Additionally the 10‐year events revealed frequent negative sediment yield anomalies in the preceding decade. This behaviour was interpreted as a frequent sediment activation cycle initiated by the modest year, and leading to sediment yield hysteresis lasting 15–25 years. The largest years (greater than 50‐year recurrence) showed consistently above‐average sediment yields in the preceding decade, in part due to the frequent occurrence of moderate (Q10) years. It is hypothesized that temporary storage of sediment and previous initiation of erosion sites resulted in extraordinary sediment yields during intense summer rainfall events. This study demonstrates the potential use of varved lake sediment records to improve our understanding of long‐term sediment dynamics. These records present an opportunity to further develop and test sediment dynamic and routing models to gain insight into the interaction of time and space in fluvial and sediment delivery processes. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
187.
188.
N. R. J. Poolton K. B. Ozanyan J. Wallinga A. S. Murray L. Bøtter-Jensen 《Physics and Chemistry of Minerals》2002,29(3):217-225
Most natural feldspars contain many charged impurities, and display a range of bond angles, distributed about the ideal.
These effects can lead to complications in the structure of the conduction band, giving rise to a tail of energy states (below
the high-mobility conduction band) through which electrons can travel, but with reduced mobility: transport through these
states is expected to be thermally activated. The purpose of this article is twofold. Firstly, we consider what kind of lattice
perturbations could give rise to both localized and extended conduction band-tail states. Secondly, we consider what influence
the band tails have on the luminescence properties of feldspar, where electrons travel through the sample prior to recombination.
The work highlights the dominant role that 0.04–0.05-eV phonons play in both the luminescence excitation and emission processes
of these materials. It also has relevance in the dating of feldspar sediments at elevated temperatures.
Received: 11 May 2001 / Accepted: 6 September 2001 相似文献
189.
190.
Analysis of monthly momentum transport of zonal waves at 850 hPa for the period 1979 to 1993, between ‡S and ‡N for January
to April, using zonal (u) and meridional (v) components of wind taken from the ECMWF reanalysis field, shows a positive correlation (.1% level of significance) between
the Indian summer monsoon rainfall (June through September) and the momentum transport of wave zero TM(0) over latitudinal
belt between 25‡S and 5‡N (LB) during March. Northward (Southward) TM(0) observed in March over LB subsequently leads to a
good (drought) monsoon season over India which is found to be true even when the year is marked with the El-Nino event. Similarly
a strong westerly zone in the Indian Ocean during March, indicates a good monsoon season for the country, even if the year
is marked with El-Nino. The study thus suggests two predictors, TM(0) over LB and the strength of westerly zone in the Indian
Ocean during March. 相似文献