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991.
去除有机质前后海底沉积物对稀土元素吸附能力的变化研究 总被引:1,自引:0,他引:1
为更好地了解有机质对沉积物吸附稀土元素能力的影响,对珠江口和南海沉积物在去除有机质之前和之后进行了稀土元素吸附实验研究。结果表明,同一种沉积物在去除有机质前后对稀土元素的吸附呈现基本相同的规律,只是吸附量有所不同。沉积物在去除有机质之后对稀土离子的吸附能力比去除有机质之前大大降低;沉积物对各种稀土元素吸附量降低的百分比为:珠江口沉积物对Yb的吸附量减少了47.24%,对La的吸附量减少了75.50%,对其它元素的吸附量减少介于47.24%—75.50%之间;南海沉积物对Sm的吸附量减少了35.93%,对Ho的吸附量减少了45.41%,对其它元素的吸附量减少介于35.93%—45.41%之间。 相似文献
992.
993.
G. R. Dargahi-Noubary 《Mathematical Geology》1992,24(2):161-169
In the context of seismology, an example of stochastic modeling on the basis of an established deterministic formulation is presented. The advantages of this approach to modeling over those based solely on statistical fit are discussed. It is demonstrated that the result of applying this procedure is a model whose main parameter has a physical interpretation, and therefore a validation based on criteria other than statistical goodness of fit is also possible. Statistical inference together with some demonstrating examples are also included. 相似文献
994.
Multivariate statistical techniques, cluster and factor analyses were applied on the Amman/Wadi Sir groundwater chemistry, Yarmouk River basin, north Jordan. The main objective was to investigate the main processes affecting the groundwater chemical quality and its evolution. The k‐means cluster analysis yields three groups with distinct ionic concentrations. Cluster 1 comprises the vast majority of the sampled wells, and the water that belongs to this cluster can be classified as freshwater. Cluster 2 comprises only 2% of the sampled wells; it has the highest ionic concentration. The water of this cluster can be classified as brackish water. Cluster 3 involves 23% of the sampled wells, and it has total ionic concentration intermediate to that of clusters 1 and 2. Factor analysis yields a three‐factor model, which explains 76.77% of the groundwater quality variation. Factor 1 ‘salinity factor’ involves EC, Na+, Cl‐, SO4‐2, K+ and Mg+2 and reflects groundwater salinization because of overpumping. Factor 2 ‘hardness factor’ includes Ca+2, HCO3‐ and the pH value and signifies soil–water/rock interaction. Factor 3 ‘nitrate factor’ involves only NO3‐ and points to groundwater contamination because of human activities, mainly untreated wastewater, and crops and animal cultivation in the unconfined portion of the aquifer. Factors 1 and 3 can be described as human‐induced factors, whereas factor 2 can be described as geogenic factor. Factors' scores were mapped to deduce the controlling processes on the groundwater chemistry. Stable isotope composition of 18O and 2H has revealed that the groundwater is a mixture of two water types. The radioactive isotopes tritium and 14 C were used to evaluate present day recharge to the aquifer and to estimate the groundwater age, respectively. Present day recharge to the groundwater is taking place in the unconfined portion of the aquifer as it is indicated by the measurable tritium content and low groundwater age. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
995.
Vertical total electron content (VTEC) time series were obtained from 22 GPS stations near the epicenter of the Lushan earthquake. In this paper, we have adopted a sliding average method to detect and analyze anomalous VTEC associated with the earthquake. The results show that signif- icant, negative ionosphere VTEC anomalies appeared over the 5 days before the earthquake, and on the day when earthquake occurred. The maximum value of VTEC anoma- lies that exceeded the lower bound reached 20 TECU. The spatial distribution of VTEC anomalies showed a conjugate structure, which shifted to the magnetic equator, and subse- quently moved westwards. 相似文献
996.
997.
High frequency seasonal drought in purple soils (Regosols in FAO taxonomy) of the hilly upland areas of Sichuan basin, China, is one of the key restrictive factors for crop production. In order to manage irrigation and fertilizer application in these soils effectively, the soil water content in a sloped plot with 60 cm soil depth was measured by neutron probe devices to investigate the soil moisture regime during the 1998 rainy season after various amounts of rainfall events. The results showed that variation of soil moisture along the slope positions was highest in the top soil layer during the period of sporadic rainfall that did not induce any runoff. The coefficients of variation of soil moisture at various slope positions (upper, middle, and lower) are 17·36%, 8·95%, 10·25%, 8·58%, 8·05% and 9·21% at the 10 cm, 20 cm, 30 cm, 40 cm, 50 cm and 60 cm soil depths respectively. When surface runoff occurred, the soil moisture dynamics at various positions on the plot were then very different. Soil water content decreased more rapidly on the upper slope than on the middle and lower slope positions. When both surface runoff and throughflow occurred, the soil moisture dynamics in the various layers showed a stable period (soil water content is near constant as time elapses) that lasted about 1 week. Also, the pattern of moisture dynamics is ‘decreasing–stabilization–decreasing’. Thus, irrigation and fertilization management according to the spatial and temporal features of soil moisture dynamics on sloped land can increase the water and fertilizer utilization efficacy by reducing their losses during the stable period. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
998.
Jiann‐Mou Chen 《水文研究》2008,22(26):5037-5047
Most methods developed to represent water flow phenomena in an unconfined aquifer with a fully penetrated pumping well are either numerical, such as the well‐known FEMWTER model, or experimental; analytical models of a partially penetrated pumping well are rare. This study employs the linearized Richards equation as the governing equation, with the aid of Fourier Integral Transformation, to obtain an analytical solution of the water content distribution in an unconfined aquifer with a partially penetrated pumping well. The results from this study could serve to substantiate in some sense results from numerical models. In addition, the theory developed herein can be modified to simulate a vacuum‐pressured pumping well since it is derived by considering, among others, the location and length of a well screen with fluxes. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
999.
1000.