河南舞阳地区赵案庄铁矿床成矿时代及地质意义——中国最古老的岩浆型铁矿床

河南舞阳地区赵案庄铁矿床是产于超基性岩中的隐伏矿床。超基性岩侵位于新太古界太华群赵案庄组透辉斜长角闪片麻岩中。矿体呈似层状,具有多层。矿石成分较复杂,主要矿物为磁铁矿、蛇纹石、氟磷灰石等。矿床规模为中等,其成因是与超基性岩有关的岩浆晚期磷灰石-磁铁矿矿床。在磷灰蛇纹磁铁矿石中选出的锆石样品为变质锆石,利用激光烧蚀多接收器电感耦合等离子体质谱仪(LA-MC-ICPMS)进行微区原位U_Pb同位素测年,获得不一致线的上交点年龄为(1943±5)Ma(MSWD=2.3)。同时对锆石阴极发光(CL)图像研究,表明该年龄代表锆石遭受强烈变质作用的年龄,可以限定矿体形成时代的上限,即矿体形成时代不晚于1943 Ma。超基性岩浆演化晚期,岩浆充填构造裂隙呈透辉石岩脉产出。透辉石脉与矿体同期并且穿切铁山庙组BIF型铁山铁矿。铁山庙组形成时代在2300~2500 Ma之间。透辉石岩脉形成时代不早于该组年龄,可作为赵案庄铁矿床形成时代的下限。赵案庄铁矿床的形成时代为1943~2300 Ma,为古元古代,这是中国目前发现的最古老的岩浆型铁矿床。该成矿地质时代反映了在华北陆块东南缘曾发生过一次地壳扩张和裂陷活动及华北克拉通裂解事件。     

杭州市降水特征及极端降水趋势预估

利用国家气候观象台杭州站百年降水观测数据和CMIP5模式模拟预估数据,分析了杭州市降水长期变化特征,采用累积概率分布函数转换方式(CDF-T),降尺度预估了未来气候情景下杭州极端降水发生趋势。结果表明:杭州市年降水量在百年时序(1907—2015年)上无显著性增加或减小趋势,1980年后春季降水明显下降,下降速率约32.1mm·(10a)~(-1),冬季降水显著增加,增加速率约35.4mm·(10a)~(-1)。1988—2015年的3和6h及日降水的各重现期降水量均较1961—1987年有所增大,1961—1987年的100年一遇日最大降水已演变为1988—2015年的50年一遇甚至是20年一遇。CMIP5模式降水的降尺度分析表明,2020—2039年杭州市日极端降水强度将可能会进一步加强,2020—2039年日降水的R95值和R99p值均较现气候期(1981—2010年)有所提高,超R95p和超R99p的极端降水发生日数分别为11.08和2.24d·a~(-1),分别较现气候期平均值增加了3.52和0.69d·a~(-1)。     

Desorption of tetracycline from montmorillonite by aluminum,calcium, and sodium: an indication of intercalation stability

As the uptake of cationic drugs, such as tetracycline (TC), was attributed to cation exchange, the stability of adsorbed TC on a Ca-montmorillonite SAz-2 was studied using cationic solutions of different valence charges under different pH conditions. At the initial loading of 356 mg g^?1, the amounts of TC desorbed by 0.05 M AlCl₃, CaCl₂, and NaCl were 133 ± 4, 83 ± 6, and 50 ± 4 mg g^?1, respectively, or 37, 23, and 14 %. However, when the amount or percentage of TC desorbed was normalized to the equivalence of each cation, the values were in the range of 44–50 mg g^?1 or 11–14 % per 10 mmol of charge. The kinetics of TC desorption were moderately fast and almost reached equilibrium in 6 h. The results followed the pseudo-second-order kinetic model with reaction rate in the order of AlCl₃ > CaCl₂ > NaCl at a higher initial TC loading level. The total amount of TC desorbed after five desorption cycles followed the order of AlCl₃ > CaCl₂ > NaCl, too, suggesting that cations with higher positive charges, thus, less hydrated, are preferred to remove adsorbed cationic drugs. The FTIR analyses showed larger band shift when Al³⁺ was used as the desorbing reagent. The XRD patterns before and after TC desorption revealed no changes in basal spacing, even after five desorption cycles, suggesting that the removal of TC from SAz-2 was largely from the external surfaces.     

Caspian Sea level prediction using satellite altimetry by artificial neural networks

The demand for accurate predictions of sea level fluctuations in coastal management and ship navigation activities is increasing. To meet such demand, accessible high-quality data and proper modeling process are critically required. This study focuses on developing and validating a neural methodology applicable to the short-term forecast of the Caspian Sea level. The input and output data sets used contain two time series obtained from Topex/Poseidon and Jason-1 satellite altimetry missions from 1993 to 2008. The forecast is performed by multilayer perceptron network, radial basis function, and generalized regression neural networks. Several tests of different artificial neural network (ANN) architectures and learning algorithms are carried out as alternative methods to the conventional models to assess their applicability for estimating Caspian Sea level anomalies. The results derived from the ANN are compared with observed sea level values and with the forecasts calculated by a routine autoregressive moving average (ARMA) model. Different ANNs satisfactorily provide reliable results for the short-term prediction of Caspian Sea level anomalies. The root mean square errors of the differences between observations and predictions from artificial intelligence approaches can be significantly reduced by about 50 % compared with ARMA techniques.     

Dynamics of deformation and water flow in heterogeneous porous media and its impact on soil properties

The interaction of geomechanics and flow within a soil body induces deformation and pore pressure change. Deformation may change hydrogeological and elastic properties, which alters the mechanical behaviour and results in non‐linearity. To investigate this interaction effect in a heterogeneous porous medium, a stochastic poroelastic model is proposed. Monte Carlo simulations are performed to determine the mean and uncertainty of the parameter changes, displacement, and change in pore water pressure. Hydraulic conductivity is treated as the only random variable in the coupled geomechanics‐flow system due to its large variation compared to other mechanical and hydrogeological properties in natural environments. The three considered non‐linear models for the interaction between parameters and deformation are those that consider (1) porosity and hydraulic conductivity; (2) porosity and Young's modulus; and (3) a combined effect that includes porosity, hydraulic conductivity, and Young's modulus. Boundary effects on the coupled system are also explored. The relationships between changes of porosity, hydraulic conductivity, and Young's modulus are analytically shown to be non‐linear. Among the considered parameters, the deformation effect induces the largest reduction in hydraulic conductivity. The deformation‐induced change in hydraulic conductivity shows the most significant effect on the mean and variance of the change in pore water pressure and displacement, while changes in Young's modulus have the least effect. When the deformation effect is considered, the superposition relationship does not exist in the mean displacement and mean change in pore water pressure for the three scenarios considered; it exists for the case without deformation effects. Deformation also causes a reduction in the effective hydraulic conductivity for the whole domain. The scenario that considers both loading and discharge boundaries has larger changes in hydrogeological and geo‐mechanical parameters than those in scenarios that consider loading and discharge boundaries separately. The results indicate that the interaction between deformation and changes in parameters has a profound effect on the poroelastic system. The effect of deformation should thus be considered in modelling and practice. Copyright © 2009 John Wiley & Sons, Ltd.     

我国四种典型土类有机碳剖面分布特征

以中国黑土、褐土、水稻土和砖红壤4种典型农田土类为研究对象,分析了不同土类有机碳、碳氮比和有机碳密度的剖面分布特征。结果表明：土壤有机碳含量随土层加深而呈现递减趋势;褐土有机碳含量最低,固碳潜力较大;黑土、砖红壤C／N比值明显高于水稻土和褐土,各类土壤耕地表层土壤C／N比值与第二次土壤普查数据相比有明显降低,有可能会影...