包气带弱渗透性黏土透镜体对降雨入渗补给影响的数值模拟

大气降雨是华北平原浅层地下水的主要补给来源。长期过量开采地下水造成地下水位持续下降,使原来处于饱水带的透镜体位移到包气带中,形成了厚度大、非均质性更为复杂的包气带。厚层包气带中弱渗透性黏土透镜体对于降雨入渗补给的影响是关系到降水入渗过程及补给量评价的基本问题。用HYDRUS软件建立数值模拟模型,模拟探讨单次降雨条件下,透镜体埋深、宽度比、厚度等要素对入渗路径、入渗补给时间和入渗补给量的影响。结果表明:入渗过程中弱渗透性黏土透镜体两侧会形成较快的绕流;透镜体会减小补给峰值并延长总体补给时间,但不改变补给起始时间;透镜体埋深与极限蒸发深度的相对关系决定了潜在补给量的大小,透镜体埋深或因透镜体形成的上层滞水处于极限蒸发深度以上会减少潜在补给量。     

辽宁树基沟铜锌矿成矿时代及矿石再活化机制

树基沟铜锌矿是产于太古宙绿岩带中的与火山岩有关的块状硫化物（VMS）矿床,运用LA-ICP-MS锆石U-Pb定年得到含矿围岩(黑云斜长片麻岩原岩)的结晶年龄约为2 565 Ma,近似代表树基沟矿体的形成时代。后期变质变形作用使矿石结构构造发生了巨大的变化,形成变质变形作用特有的结构构造,有变斑晶结构、硫化物生长结构、碎裂结构、旋转碎斑结构、充填和交代结构以及退变质结构等。成矿组分的两期再活化过程对应了两期变质变形事件：第一期变质变形过程中,矿石以机械再活化迁移为主,并在压力小的位置形成“铜矿囊”;第二期变质变形过程中,矿石的活化方式呈现出复合再活化的特点,具体表现为黄铁矿变斑晶颗粒被再活化的石英-硫化物细脉充填,并发育一定程度的交代作用。     

降水波动对荒漠草原生产力的影响

在干旱、半干旱荒漠草原区,降水量波动对植被生产力有显著影响.这种影响表现在两个层次上,一是降水量年际间波动,二是年内降水分布格局.对阴山北麓内蒙古乌拉特后旗荒漠草原多年气象资料和植被生产力的分析发现:从1971-2011年降水量的年际波动特点来看,荒漠草原区最高降水年的降水量是最小降水年的3.76倍.从气象、实际和矢量年降水量3种统计表达方式与生产力的关系来看,反映年际降水波动和年内分布特点的矢量降水与植被生产力的关系最密切(R=0.9200,R_0.001=0.8010),回归方程F检验达到极显著.由于研究区植被组成以小半灌木和多年生草本为主,且年降水量大部分集中在5-8月,生长期内月降水量的累积效应明显,其中6-8月累计降水对植被生产力的影响最显著.     

科尔沁沙地几种固沙植物光谱-生物量模型构建与分析

在控制背景反射噪音、植被盖度和水分含量的条件下,利用ASD光谱仪对科尔沁沙地4种主要固沙植物杨树(Populus spp.)、黄柳(Salix gordejevii)、小叶锦鸡儿(Caragana microphylla)、樟子松(Pinus sylvestris)光谱反射特征和地面光谱生物量模型构建进行了研究.结果表明:科尔沁沙地4种主要固沙植物光谱反射曲线的趋势基本一致,但是在620～670 nm与841～876 nm波长范围内存在差别,其中在波长620～670 nm最易识别的植物为小叶锦鸡儿,其次是黄柳、杨树,在波长841～876 nm范围最易识别的植物为樟子松、杨树.不同植物的NDVI与盖度和生物量的关系密切,模型拟合精度较高.相对而言,NDVI-盖度模型优于NDVI-生物量模型.不同植物种构建的NDVI盖度模型计算结果相差较小,而NDVI生物量模型的计算结果相差较大.在区域植被生产力遥感监测中,植被样方选择要考虑优势植物种影响,数据采样要涵盖研究区主要植物种.     

A simple earth system model for C3IAM: based on BCC_CSM1.1 and CMIP5 simulations

Natural Hazards - City is an important foundation for human development. Natural disasters, whose impact on cities was influenced by disaster risk, urban vulnerability and resistance, have always...     

江西朱溪铜钨矿床成因:来自矿物学和年代学的启示

江西景德镇朱溪铜钨矿床是近年来发现的一个世界级超大型铜钨矿床。矿床地质特征、矽卡岩矿物学和成矿岩体年代学的研究表明,矿体赋存于上石炭统黄龙组大理岩与新元古界双桥山群变质岩之间的不整合界面之上,空间上具有明显的矿物组合分带特征。根据矽卡岩产状、矿物共生组合和相互关系,把成矿作用划分为矽卡岩阶段、退化蚀变阶段、石英-硫化物阶段、碳酸盐-萤石阶段。代表性的矽卡岩矿物组合有石榴子石、透辉石、透闪石、硅灰石、符山石、蛇纹石、绿泥石等。电子探针分析表明,石榴子石为钙铝榴石—钙铁榴石系列,辉石为透辉石—钙铁辉石系列。同位素年代学及岩浆与成矿关系的研究表明：花岗闪长岩与早期矽卡岩型矿化相关,矿化范围较小,矿石品位较低;黑云母花岗岩与云英岩型和晚期矽卡岩型的矿化相关,矿化范围较广,矿石品位较高,并获得黑云母花岗岩LA-ICP-MS锆石U-Pb年龄为（147.7±2.2）Ma。综合分析指出,朱溪铜钨矿床为晚侏罗世花岗岩浆有关的热液与晚古生代碳酸盐岩发生多阶段交代作用而形成,成矿作用以矽卡岩型和云英岩型为主。     

Analytical and experimental studies on installation of a suction caisson with tampered tip in clay

Concrete suction caissons have been successfully used as breakwaters or seawalls in recent years. The relative large wall thickness-to-diameter ratio of a concrete caisson can lead to the formation of a full soil heave plug that may cause difficulties in the installation of concrete caisson in clay. One way to overcome this limitation is to use a tampered tip for the caisson wall. An analytical method is proposed in this article to calculate the minimum suction pressure required to penetrate a caisson and the maximum allowable suction pressure that can be applied to avoid too much soil heave plug during the installation of the suction caisson. Four model tests were conducted in normally consolidated clay to study the installation process of a concrete suction caisson with tampered tip and to verify the proposed analytical method. The height of the soil heave plug in the caisson with a tampered tip is observed to be about half of that in the caisson with a flat tip.     

An experimental study on controlling post-earthquake debris flows using slit dams

Post-earthquake debris flows often break out in groups frequently, which are usually caused by the abundant loose solid materials that produced by earthquake. Slit dams represent a practical and effective kind of countermeasure for controlling the post-earthquake debris flow. Flume experiments were carried out to study the interaction mechanism and the effect of slit dams on the post-earthquake debris flows. The results showed that affected by the slit dams, some certain types of deposits formed on the upstream. The steeper the flume slope, as well as the greater the width and the density of slits, the easier the lateral deposit became “V” shaped. Otherwise, the lateral deposit was more likely to be “–?” shaped. When the flume slopes were 12°, 16° and 20°, the profiles of the deposits would be long-shallow type, short-thick type and short-shallow type, respectively. The slope of the deposition first decreases and then increases with the flume slope increasing within a certain range. The slit dam can trap the coarse sand and discharge the fine sand. The maximum attenuation rate can reach 44.4%. The effect of this capacity gradually weakens as the flume slope is increased. When the width or the density of slits is smaller, the greater the rate of decrease in peak sand discharge and the greater the effect of peak cutting will be. The reduction in the sediment storage rate is likely due to the increase in the width and the density of the slits. With the increase in flume slope, the sediment storage rate first increases, then decreases, which reaches a maximum value when the flume slope is 16°.     

High-resolution profiles of trace metals assessed by DGT techniques in lake sediment porewaters

The technique of diffusive gradients in thin films (DGT) was applied to obtain high-resolution vertical profiles of trace metals in sediment porewater of a eutrophic lake, Lake Chaohu. All sampling sediments were under anaerobic conditions with Eh values below 0, the redox potential profile in M4 was relatively stable, and higher Eh values in M4 than that in M1 were observed due to hydrodynamic effects. Fe, Mn and As exhibited closely corresponding profiles due to the co-release of Fe and Mn oxides and the reduction of As. Higher Fe and Mn concentrations and lower As concentrations were observed in M1 of the western half-lake than those in M4 of the eastern half-lake due to different sources and metal contamination levels in the two regions. Cu and Zn showed increasing concentrations similar to Mn and Fe at 1–2 cm depth of sediments, while DGT measured Co, Ni, Cd and Pb concentrations decreased down to 3–4 cm in the profiles. Co, Ni, Cu, Zn, Cd and Pb showed insignificant regional concentration variances in the western and eastern half-lakes. According to the R(C _DGT/C _{centrifugation}) values, the rank order of metal labilities decrease as follows: Fe (>1) > Cu, Pb, Zn (>0.9) > Co, Ni, Cd (>0.3) > Mn, As (>0.1).     

北斗卫星系统频间偏差预报模型研究

为研究北斗卫星频间偏差参数(DCB)长期及短期变化特性,在某卫星DCB参数缺失时,对该卫星DCB参数进行短期及长期预报,以预报值代替真实值。本文利用中国测绘科学研究院i GMAS分析中心数据,采用二次多项式拟合法对北斗卫星DCB参数展开研究,通过构建电离层延迟模型求解北斗卫星DCB参数,统计了北斗卫星包括GEO卫星、IGSO卫星、MEO卫星的2016-01~2016-12及2017-02-01~2017-02-28的频间偏差参数解算结果,分析其变化特性,并采用二次多项式拟合法对DCB参数进行长短期预报及精度分析。实验证明,相比GEO、IGSO卫星、MEO卫星的DCB参数较低且波动幅度介于GEO、IGSO卫星之间;二次多项式拟合法可对北斗卫星的频间偏差参数进行预报,对北斗卫星的频间偏差求值及预报具有重要的参考作用。