西天山吐拉苏—也里莫墩早石炭世火山岩带地质特征

我国西天山吐拉苏—也里莫墩早石炭世火山岩带是伊犁裂谷的北展部分,其中赋存有阿希大型金矿。火山岩带内除局部地区见底部沉积砾岩外,主体为陆相中酸性火山熔岩、火山碎屑岩以及石英角闪安山玢岩（潜火山岩）,火山岩属钙碱性—碱性系列岩石组合。火山活动受近EW向（一级）和近SN向（二级）火山构造控制,并保留了火山机构（三级）。形成的古构造环境为陆缘拉张带。火山岩带活动时限较短,只限于早石炭世早期。     

Nonlinear stability analysis of the zonal flows at middle and high latitudes

An attempt has been made to apply Arnol’d type nonlinear stability criteria to the diagnostic study of the persistence (stability) or breakdown (instability) of the atmospheric flows. In the case of the blocking high, the cut-off low and the zonal flow, the relationships of the geostrophic stream function versus the po-tential vorticity of the observed atmosphere are analyzed, which indicates that Arnol'd second type nonlinear stability theorem is more relevant to the observed atmosphere than the first one. For both the sta-ble and unstable zonal flows, Arnol’d second type nonlinear stability criteria are applied to the diagnosis. The primary results show that our analyses correspond well to the evolution of the atmospheric motions. The synoptically stable zonal flows satisfy Arnol'd second type nonlinear stability criteria; while the synoptically unstable ones violate the nonlinear stability criteria.     

黔中岩溶地区岩土水系统中氟的环境地球化学研究

通过对研究区碳酸盐岩— 土— 水系统中氟的系统测定和吸附实验,结合矿物表面化学和土壤化学研究,揭示了岩溶地区岩— 土— 水系统中氟的地球化学特征和迁移富集机理。黔中岩溶地区深层地下水( 100m 以下)和土层具有高氟异常特征,而浅层地下水和地表水含氟较低(大多在0. 5mg /l以下)。以含石膏碳酸盐岩为主的三叠纪海相地层是该区土水中氟的主要来源。土层中针铁矿表面对氟的专性吸附及其解吸作用是岩溶地区土水系统中氟迁移和富集的重要机理。      

Waste dump erosional landform stability – a critical issue for mountain mining

Mining is the largest producer of solid wastes which, when released to land or into waterways, can cause harmful environmental impacts. This is mostly due to fluvial erosion, which is highly increased in mountain areas, due to abrupt slopes. We have analysed this situation at a mountain watershed (192 ha), where steep mined sites and their waste dumps are the main source of sediment in a Natural Park. This problem was tackled by building gabion check dams downstream from the mined sites. We used the DEM of Differences (DoD) method to quantify erosion and sediment yield from three waste dumps (5 ha). Their topography and substrate properties were analysed to understand the erosion problem. The sediment trapped by the check dams was quantified by electrical resistivity tomography (ERT). The rainfall characteristics triggering an episode that filled the check dams with sediment in the winter 2009–2010, were studied to confirm whether it was a case of extreme precipitation conditions. The waste dumps sediment yield (353 ± 95 Mg ha^?1 yr^?1) suggests severe landform instability. Analysis of topographic and substrate properties confirmed long, steep slopes combined with highly erodible materials. The check dams proved to be inefficient in controlling sediment loads, as they had only functioned for four years of 31 of existence, having trapped 13 000 ± 660 m³ of sediment, whereas we estimated that the waste dumps have yielded approximately three times more sediment for the same period. Rainfall analyses showed that neither intense nor extreme conditions (return period of 25 to 35 years) triggered the mobilization of 37 ± 2 Mg ha^?1 in a month. This study highlights the fact that mining operations in similar mountainous settings, with equivalent waste dump construction and reclamation practices, are currently unfeasible. We conclude that landform stability cannot be achieved at this site without landform changes. Copyright © 2017 John Wiley & Sons, Ltd.     

山西洪洞井水位对远场大震的响应特征分析

对洪洞井水位自2013年数字化改造以来记录到的同震响应资料进行统计分析后认为:洪洞井水位对全球MS≥7.5的远场大震有较好的响应能力,其同震响应呈一定的方向性;对不同地震的响应形态具有固定模式,以水震波为主,部分水震波伴随阶变;水位振荡阶变的初始方向以上升为主。统计分析显示,井水位同震变化幅度与震级、井震距无明显相关性,水位响应时刻与井震距有一定关系。进一步核实表明:引起水位同震响应的地震波大多为S波,部分为P波、面波;S波引起的水位变化幅度要小于P波,而面波引发的水位变化幅度最大。综合分析了前人对水位振荡的机理研究,并结合洪洞井具体情况对其相关机理进行了初步探讨。     

Numerical simulation of 23 June 2016 Yancheng City EF4 tornadic supercell and analysis of lightning activity

Based on the Weather Research Forecasting (WRF) model that features charging and discharging parameterization, relationships between tornado, hail and lightning were investigated for a tornado-producing (EF4 intensity) supercell thunderstorm over Yancheng City in Jiangsu Province, China, on 23 June 2016. Based on a sounding at 0800, there was a low lifting condensation level, substantial convective available potential energy (CAPE), and strong vertical wind shear near Yancheng City, which promote supercell development. At 1400, observations revealed that hail production and a dramatic increase of positive cloud-to-ground flash rates occurred simultaneously, maximizing five minutes later. The tornado occurred 30 min after the hail production. The time of minimum positive cloud-to-ground flash rates was 15 min later. The simulation indicated that the tornadic supercell moved eastward and that positive cloud-to-ground flash rates increased dramatically at 1400, the same as observed, but their maximum was 5 min later than observed. The simulated updraft volume peaked at 1425 and the simulated downdraft volume maximized 5 min later, when the mesocyclone formed. Simulated reflectivities showed no hook echo and horizontal winds for different height at mid-low levels had a different cyclonic shear at 1430, favorable to mesocyclone formation. Based on the simulated results, the region of positively charged graupel ascended resulting from the region of high liquid water content was lifted by the strong updraft, forming a mid-level strong positive charge region. A lower negative charge region formed by the inductive charging mechanism of collisions between graupel and droplets at the bottom of the cloud, conducive to positive cloud-to-ground flashes.     

Preliminary calibration results of the HY-2B altimeter’s SSH at China’s Wanshan calibration site

Satellite altimeter needs to be calibrated to evaluate the accuracy of sea surface height data. The dedicated altimeter calibration field needs to establish a special calibration strategy and needs to evaluate its calibration ability. This paper describes absolute calibration of HY-2B altimeter SSH using the GPS calibration method at the newly Wanshan calibration site, located in the Wanshan Islands, China. There are two HY-2B altimeter passes across the Wanshan calibration site. Pass No. 362 is descending and the ground track passes the east of Dan’gan Island. Pass No. 375 is ascending and crosses the Zhiwan Island. The GPS data processing strategy of Wanshan calibration site was established and the accuracy of GPS calibration method of Wanshan calibration site was evaluated. Meanwhile, the processing strategies of the HY-2B altimeter for the Wanshan calibration site were established, and a dedicated geoid model data were used to benefit the calibration accuracy. The time-averaged HY-2B altimeter bias was approximately 2.12 cm with a standard deviation of 2.08 cm. The performance of the HY-2B correction microwave radiometer was also evaluated in terms of the wet troposphere path delay and showed a mean difference ?0.2 cm with a 1.4 cm standard deviation with respect to the in situ GPS radiosonde.     

Acoustic emission processes occurring during high-pressure sand compaction

Granular materials submitted to uniaxial compression undergo pore space reduction due to mechanisms such as particle rearrangement and grain crushing. These changes in the internal structure of the material release energy in the form of elastic waves that can be detected by sensors sensitive to acoustic emission. In this study, Acoustic emission monitoring with a wavelet-based signal processing technique is used to identify the various mechanisms occurring during high-pressure sand compaction. Particle movement, grain failure, friction between grains and the surface of the compression cell and intergranular friction are studied. Acoustic emission data recorded during these simplified tests are used to characterize each phenomenon. Wavelet transform analyses allow the identification of useful features, making possible frequency discrimination among sliding, rolling, friction and grain fragmentation processes. For instance, we observe that at low stress, grain flow is characterized by the lowest centroid and peak frequencies, while at greater stresses, intergranular friction and grain fragmentation have the higher values. In the tests performed, the stress–strain evolution and final condition of the tested sand are broadly consistent, irrespective of the condition employed: continuous, stepwise or even variable loading rate or temperature. However, Acoustic emission data manifest much more complex behaviour (including thermal, load-rate dependency and delayed fragmentation phenomena) than that suggested by stress–strain relationships. At low stress levels, grain flow (sliding/rolling) is a relevant strain-accommodation mechanism, but so is crushing due to the effect of concentrated forces at the grain contact level. At high stresses, when crushing is generalized, intergranular friction is also a relevant phenomenon due to the increase in the coordination number produced by previous fragmentation.     

The impact of climate change and human activities on streamflow and sediment load in the Pearl River basin

This paper uses monthly streamflow, suspended sediment concentration, and meteorological data to examine the impact of human activity and climate change on streamflow and sediment load in the Pearl River basin from the 1950s to the 2000s. The influences of climate change and human activities on hydrological processes were quantitatively evaluated using the Mann–Kendall abrupt change test and power rating curves. The results showed that:(1) abrupt changes and turning points in streamflow occurred in 1963, 1983, and 1991 which were found to be consistent with global ENSO events and volcanic eruptions. However, abrupt changes in sediment load showed significant spatial differences across the Pearl River basin. For the Xijiang River, an abrupt change in sediment load occurred in 2002, and after 2007 the change becomes significant at the 95% confidence level. At Beijiang and Dongjiang, abrupt changes in sediment load occurred in 1998 and 1988, respectively.(2) The time series of sediment load data was divided into four periods according to abrupt changes. The contribution of climate change and human activities is different in the different rivers. For the Xijiang River, compared with the first period, climate change and human activities contributed 83% and 17%, respectively, to the increasing sediment load during the second period. In the third period, the variation of sediment load followed a decreasing trend. The contribution from climate change and human activities also changed to t236% and -136%, respectively. In the fourth period, climate change and human activities contributed -32% and t132%, respectively. Meanwhile, For the Beijiang River, climate change and human activities contributed 90% and 10% in the second period, the contribution of climate change increased to t115% and human activities decreased to -15% in the third period. In the fourth period, the value for climate change decreased to t36% and human activities increased to t64%. For the Dongjiang River, the contribution of human activities was from 74.5% to 90%, and the values for climate change were from 11% to 25%. Therefore, the effect of human activity showed both spatial and temporal differences, and it seems likely that the decreased sediment load will continue to be controlled mainly by human activities in the future.     

山西夏县中心地震台温泉水化学特征

采集夏县中心地震台温泉水及周边水点样品进行水化学组分特征分析。利用矩形图、Na-K-Mg三角图等方法,初步分析温泉水的水质类型、水-岩平衡状态、热储温度以及循环深度等,并结合氢氧同位素组成特征,初步分析温泉水补给来源。研究表明,夏县中心地震台温泉水化类型属于Na-Cl·SO₄型,水-岩反应属于部分成熟水,热储温度为148.8℃,循环深度为3.91 km,补给源主要为大气降水,温泉为断裂型温泉。以上结果可为该台流体异常分析提供基础研究资料,为夏县地区水化研究奠定基础。