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1.
Fenglin WANG Xumei MAO Cunfu LIU 《中国地球化学学报》2006,25(B08):280-281
One kind of climatic proxies only can describes the comparative change of temperature or rainfall, but dissolved noble gases in groundwater can be used to date groundwater, calculate temperature and rainfall, and this method can give the exact change value of three parameters in one time. Dissolved noble gases in groundwater has four sources, radioactivity-formed noble gases which are from radioactive decay of some radioactive elements in the aquifers, balance-dissolved noble gases from dissolved air in balance condition in the course of supplying, excess noble gases from excess air for groundwater-air mixing and water table changing during infiltrating, and outer-interfused noble gases from outer interfusing air in open conditions during runoff. Because the contents of radioagenic noble gases in groundwater are correlated to flowing time, such as He, the age of groundwater can be dated with 4He based on the solubility of He and the radioactive intensity of aquifers. The solubility of noble gases is the function of temperature. We can compare the contents of balance-dissolved noble gases in groundwater with the temperature-solubility experimental curves of noble gases, and calculate the forming temperature of groundwater. The contents of excess noble gases are related to the water column of infiltration which can reveal the volume of rainfall in a given period of time in general, and it may increase along with the pressure of aquifers when groundwater table rises greatly. So we can calculate the value of rainfall by comparing the contents of excess noble gases in groundwater samples with those in modem groundwater. Reconstruction of climatic change on a quantitative basis with the method of dissolved noble gases in Hebei plain （China） shows that the temperature changed from 3.8 to 19.7℃ in the past forty thousand years, it decreased to 3.8℃ in 16000 a B.P. but higher than 19.7℃ in 5060 a B.P. The rainfall was about 600mm during 40000 to 15000 a B.P., then decreased gradually to 410mm in 11000 a B.P., but subsequently increased to 950mm in 4400 a B.P. The change of noble gas temperature is consistent with 180 shift, and 6D varied with the change of other climatic proxy, such as rainfall. 相似文献
2.
Wang Zhiping 《《地质学报》英文版》1989,63(2):103-114
China is rich in Middle and Carboniferous fossil corals. The coral faunas in different regions have varying characteristics and can be divided into distinct assemblages. The coral fauna in South China is dominated by the order Caninida and contains numerous endemic elements; that in North China has a lot of Middle Carboniferous corals which are monotonous in species, with Late Carboniferous solitary corals being predominant. The coral fauna in Junggar mainly contains large bi-zoned solitary caninids, while that in southern Khingan is similar to that in South China due to the presence of abundant tri-zoned compound corals. In northern Tibet the coral fauna is also similar to that in South China, but in southern Tibet it is of a cold-water type. Therefore, the Middle and Late Carboniferous coral geography of China can be divided into the Tethys, Boreal and Gondwana Realms. 相似文献
3.
AhmedA.Melegy T.Paces 《中国地球化学学报》2004,23(2):155-162
Heavy metals in different environmental compartments can be hazardous to ecosystems. Budgets of Cd, Pb and Zn in small ecosystems of the Shubra E1-Kheima area in Egypt are presented. The budgets are not in steady state because they change with time. So the concentrations of the metals are a function of time. The critical loads of heavy metals to soils can be calculated from an inventory of inputs and outputs of the trace components in the catchment area.Critical time is an important parameter for critical load evaluation because it can indicate which of the heavy metals may be the most acute threat to the soils. Egyptian soil in the Shubra ElKheima area seems to be in danger of heavy metal pollution by Zn, Cd and Pb. The calculated critical loads and their exceedances are approximate indicators of the hazards in the soil system.The critical time is a warning signal to initiate an environmental evaluation of possible pollution hazards. 相似文献
4.
The use of the heavy minerals in sedimentary rocks as a means for correlation of stratigraphic problem is becoming more and more widespread in recent years, especially in England and United States. Where the rock formations are scanty in fossils or can not be correlated by fossils alone, the study 相似文献
5.
Compositional peculiarities of the siliceous high-Mg series(SHMS)rocks formed at the Archean-Paleoproterozoic boundary as a function of plume activity are discussed using example of Early Paleoproterozoic mafic volcanic rocks of the Vodlozero Domain,Fennoscandian Shield.These rocks are characterized by wide variations in Mg#(33-67)and Cr contents(25-1123 ppm),LREE enrichment,and weakly negative_(εNd)(from-0.7 to-2.9).The high Gd/Yb ratio in the primitive high-Mg rocks of the Vodlozero Domain suggests their generation from a garnet-bearing source.At the same time,their negative _(εNd)in combination with LREE enrichment points to the crustal contamination.A new model was proposed to explain the remarkable global-scale similarity of SHMS.Such rocks can be generated by the contamination of a high-degree(30%)partial melt derived from a depleted mantle.The lower crustal sanukitoid-type rocks can be considered as a universal crustal contaminant.Modeling showed that such mixing can provide the observed narrow_(εNd)variations in Early Paleoproterozoic volcanics.The Neoarchean sanukitoid suites,which are widespread on all cratons,presumably composed the lower crust at the beginning of the Paleoproterozoic.Therefore,this mechanism can be considered universal for the genesis of the SHMS rocks.The high-to low-Cr rock series can be produced by the fractionation of the mafic melt coupled with an insignificant crustal assimilation of felsic end members of the sanukitoid suite of the Vodlozero Domain en route to the surface,as suggested by the positive correlation of_(εNd)with Cr and Mg#,negative correlation with Th,and slight decrease of_(εNd)in the more evolved varieties. 相似文献
6.
A number of phenomena and processes in geosciences can be summarized by second order partial differential equations. The major numerical methods for their solution include the classical finite difference method and the finite element method newly developed in the last two or three decades. Since 1977 the author has proved that for the Laplace and Poisson equations, these two methods are identical and are different only in the process of formulation. For transient problems, such as heat conduction in the earth and the groundwater and oil-gas unsteady flow in porous media, there are some differences in resulting linear algebraic euqations. In general, two methods give similar results, but when the time step is decreased to some extent, the resulting algebraic equation will be consistent with the anti-heat conduction equation rather than the original heat conduction equation. This is the reason why unrealistic potentials are produced by the finite element method. Such a problem can be overcome by using the 相似文献
7.
Yaping WANG Chunxue XU Suming WANG Ziyi AN 《中国地球化学学报》2006,25(B08):15-15
Along with the rapid development of science and technology, natural matter and energy are further exploited and used. The pollution imposed on nature has also sharply increased. Only do we know the pollution history, can we make a correct appraisal of local environment, get the hold of the main cause of environmental pollution, and then take the effective measures to control the environment？ The evolution of heavy metal concentrations with time in the soil environment in the southern suburbs of Beijing were studied by using annual growth rings of trees. The absorption of 12 elements by different tree species in the same soil type was studied according to their absorption coefficients. The study indicated the differences in adsorption of elements by different species of trees. The adsorption coefficients of the elements Zn, Cd and P are higher. The correlations of nine elements （Na, K, Cu, Zn, As, Sr, Cd, Ba and Pb） in growth rings of poplar trees and those in soils near their roots show that the element contents in growth rings have a positive correlation with the contents in soils near the roots. Based on the logarithmic linear correlation model, the evolution of the contents of the elements Cu, Zn, As, Cd, Ba and Pb in soils from 1982 to 2004 was deduced. The trees have the characters of confirming year precisely, long life and widespread distribution. They are the ideal objects of study on environmental pollution changes. At present, research in China in this aspect is less, and the field of research is expected to further expand. This method can be used to provide richer and more scientific information on the history of environmental pollution and changes during modem urbanization in the past few decades and predicting the evolutionary trend of pollution change. 相似文献
8.
《《地质学报》英文版》1990,64(1)
The calculations of unsteady flow to a multiple well system with the application of boundary elementmethod (BEM) are discussed. The mathematical model of unsteady well flow is a boundary value problem ofparabolic differential equation. It is changed into an elliptic one by Laplace transform to eliminate time varia-ble. The image function of water head H can be solved by BEM. We derived the boundary integral equation ofthe transformed variable H and the discretization form of it, so that there is no need to discretize the bounda-ries of well walls and it becomes easier to solve the groundwater head H by numerical inversion. 相似文献
9.
Rainfall simulations have been conducted to study the soil erosion process of purple soil in two cultivation practices---contour cultivation and downslope cultivation. Results showed that under the two cultivation practices, the surface runoff can be described by the logarithmic function formula. In the initial period of rainfall, the amount of runoff increased with the rainfall duration and 20 minutes later it became relatively constant. The changing process of soil erosion rate may be described by the logarithmic function formula. The erosion rate increased with the rainfall duration and 20 minutes later it also became constant. Under downslope cultivation condition, the soil erosion rate increased more significantly than that under contour cultivation condition in the case of gentle rainfall intensity, and there is no obvious difference in erosion rate for downslope cultivation and contour cultivation practices. However, with increasing rainfall intensity the soil erosion rate under the downslope cultivation condition could be more than 30 times that under the contour cultivation condition. But this kind of difference would be reduced to some extent in the case of heavy rain. 相似文献
10.
LI Yanrong Adnan AYDIN XIANG Xiqiong JU Nengpan ZHAO Jianjun Ahmet OZBEK 《《地质学报》英文版》2012,86(4):1022-1030
11.
以湖南省张家界市桑植县为研究区,在全面分析近30年降雨及滑坡数据的基础上,对滑坡及滑坡数量与降雨因子的关系开展了统计分析研究。首先确定了区域最佳有效降雨衰减系数,同时分别按滑坡规模、坡度、厚度大小统计了降雨与历史滑坡信息,得出有效降雨强度（I）与持续时间（D）散点图,由此确定各不同概率下诱发滑坡的区域有效降雨强度阈值,并进行了滑坡灾害危险性等级划分。进而,利用部分样本数据进行逻辑回归分析,得到了该研究区的滑坡发生概率预测方程,并给出了降雨强度临界值定量表达式,最后选用实际降雨诱发滑坡事件与未诱发滑坡事件进行对比验证。结果表明,文章所建立的滑坡预测模型准确性较高,预测情况与实际情况比较吻合。 相似文献
12.
The stable isotopic analyses (δ18O and δ13C) of a coralFavia speciosa spanning forty two years (1948–89 A.D.), collected from the Pirotan island (22.6°N, 70°E) in the Gulf of Kutch have been
carried out to assess its potential for retrieving past environmental changes in this region. It is seen that the summer (minima)
δ18O variations in the coral CaCO3 are negatively correlated with seasonal (summer) monsoon rainfall in the adjoining region of Kutch and Saurashtra and a qualitative
reconstruction of historical rainfall variations in this region can be obtained by analyzing the δ18O in this species of coral. The observed mean seasonal range of δ18O variations is 0.34 ±0.17‰ (n = 42), whereas the expected range calculated (from available SST and measured δ18O of sea water) is ∼ 1.1 ±0.15‰ The difference is due to the coarse resolution of sampling, which can be corrected. The seasonal
range in δ13C is ∼ l‰ and is explained by changes in: a) the light intensity related to the cloudiness during monsoons and b) phytoplankton
productivity. 相似文献
13.
J. Zinke M. Pfeiffer O. Timm W.-Ch. Dullo G. J. A. Brummer 《International Journal of Earth Sciences》2009,98(1):115-133
We examine the relationship between three tropical and two subtropical western Indian Ocean coral oxygen isotope time series
to surface air temperatures (SAT) and rainfall over India, tropical East Africa and southeast Africa. We review established
relationships, provide new concepts with regard to distinct rainfall seasons, and mean annual temperatures. Tropical corals
are coherent with SAT over western India and East Africa at interannual and multidecadal periodicities. The subtropical corals
correlate with Southeast African SAT at periodicities of 16–30 years. The relationship between the coral records and land
rainfall is more complex. Running correlations suggest varying strength of interannual teleconnections between the tropical
coral oxygen isotope records and rainfall over equatorial East Africa. The relationship with rainfall over India changed in
the 1970s. The subtropical oxygen isotope records are coherent with South African rainfall at interdecadal periodicities.
Paleoclimatological reconstructions of land rainfall and SAT reveal that the inferred relationships generally hold during
the last 350 years. Thus, the Indian Ocean corals prove invaluable for investigating land–ocean interactions during past centuries.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
14.
降雨与滑坡灾害相关性分析及预警预报阀值之探讨 总被引：34，自引：3，他引：31
详细研究了深圳市降雨与滑坡的历史资料,对区域性滑坡与降雨量进行偏相关分析,与降雨强度进行相关分析以及与降雨时间进行了系统地统计分析。研究结果表明,（1）滑坡的活动1～4日的降雨量及一次降雨过程的降雨量偏相关系数较大,表明一次性降雨量达到或超过某一数值时区域性滑坡就可以出现;（2）暴雨尤其是大暴雨及特大暴雨与滑坡的关系非常密切,相关系数达0.8以上,大暴雨或特大暴雨具有直接触发滑坡的作用;（3）滑坡活动时间与季节性降雨相对应,季节雨量越多,滑坡亦越多;另外滑坡活动时间与暴雨、大暴雨相吻合或略滞后,滞后时间一般不超过4 d,暴雨的当天及次日发生滑坡的可能性最大。在此基础上,探讨了区域性滑坡发生的临界降雨量和降雨强度阀值。最后将滑坡灾害的地质模型与降雨模型耦合建立了滑坡灾害的空间预警预报区划指标和等级系统,为区域滑坡灾害发生的时间与空间预报预警提供了科学依据。 相似文献
15.
16.
The determination of statistical and deterministic hydrological landslide-triggering thresholds 总被引：25，自引：0，他引：25
Mark T. J. Terlien 《Environmental Geology》1998,35(2-3):124-130
Hydrological landslide-triggering thresholds separate combinations of daily and antecedent rainfall or of rainfall intensity
and duration that triggered landslides from those that failed to trigger landslides. They are required for the development
of landslide early warning systems. When a large data set on rainfall and landslide occurrence is available, hydrological
triggering thresholds are determined in a statistical way. When the data on landslide occurrence is limited, deterministic
models have to be used. For shallow landslides directly triggered by percolating rainfall, triggering thresholds can be established
by means of one-dimensional hydrological models linked to the infinite slope model. In the case of relatively deep landslides
located in topographic hollows and triggered by a slow accumulation of water at the soil-bedrock contact, simple correlations
between landslide occurrence and rainfall can no longer be established. Therefore real-time failure probabilities have to
be determined using hydrological catchment models in combination with the infinite slope model.
Received: 15 October 1997 · Accepted: 25 June 1997 相似文献
17.
18.
The reconstruction of the climatic history during the past several hundred years requires a sufficient geographical coverage
of combined climate proxy series. Especially in order to identify causal connections between the atmosphere and the ocean,
inclusion of marine records into composite climate time series is of fundamental importance. We present two skeletal δ
18O chronologies of coral skeletons of Diploria labyrinthiformis from Bermuda fore-reef sites covering periods in the nineteenth and twentieth centuries and compare them with instrumental
temperature data. Both time series are demonstrated to display sea-surface temperature (SST) variability on inter-annual to
decadal time scales. On the basis of a specific modern δ
18O vs instrumental SST calibration we reconstruct a time series of SST anomalies between AD 1350 and 1630 covering periods
during the Little Ice Age. The application of the coral δ
18O vs temperature relationship leads to estimates of past SST variability which are comparable to the magnitude of modern variations.
Parallel to δ
18O chronologies we present time series of skeletal bulk density. Coral δ
18O and skeletal density reveal a strong similarity during Little Ice Age, confirming the reliability of both proxy climate
indicators. The past coral records, presented in this study, share features with a previously published climate proxy record
from Bermuda and a composite time series of reconstructed Northern Hemisphere summer temperatures. The coral proxy data presented
here represent a valuable contribution to elucidate northern Atlantic subtropical climate variation during the past several
centuries.
Received: 9 November 1998 / Accepted: 13 September 1999 相似文献
19.
为了解决由降雨强度引起的径流汇流的非线性问题,提出一种基于SCS(United States Department of Agriculture-Soil Conservation Service)流速公式的时变分布式单位线计算方法。引入参考雨强表征SCS公式中流速系数对应的水力条件。由降雨过程的时段雨强与参考雨强的比值构成一个量纲一因子,将该因子加入SCS公式后使其能够考虑降雨对流速的影响。改进后的流速公式用于计算一次降雨过程中不同降雨时段对应的时变分布式单位线,时变分布式单位线与新安江模型的产流模块构成降雨径流模型,将模型用于裴河流域率定参考雨强。率定后的模型用于谭家河流域进行应用检验,结果显示,确定性系数大于等于0.9的洪水场次,由时不变单位线的42%增大为83%。提出的方法能够显著提高流域水文模型的降雨径流模拟能力。 相似文献
20.
Rainfall-induced landslides can cause loss of life and damage to property, infrastructure, and the environment. Rainfall patterns affect the pore-water pressure of unsaturated soil slopes, and are related to the slopes’ stability. Four rainfall patterns were chosen to represent natural rainfall patterns for an examination of rainfall infiltration into soil slopes using numerical models incorporating coupled water infiltration and deformation in unsaturated soils. Our analysis showed that rainfall patterns play a significant role in the distribution of the pore-water pressure in soil slopes, and influence the slope stability. The pore-water pressure profile of soil slopes and the factor of safety are affected by the ratio of rainfall intensity and the coefficient of permeability. The depth and shape of the shallow sliding plane of the landslide is closely related to the rainfall pattern; moreover, the results showed a correlation between the factor of safety of the slope and the rainfall intensity. This relationship can be described by a dimensionless rainfall intensity. The nonlinear relationship can be used to estimate the slope stability resulting from rainfall infiltration when the hydro-mechanical coupling in unsaturated soil slopes is considered. 相似文献