近期长江河口冲淤演变过程研究

基于长江河口1997年以来数字地形图和近期水文泥沙实测资料,分析研究了近期长江河口大量人工整治工程和流域水库工程建造影响下的河口河道自动调整过程。结果表明:1997-2013年河口段中上游河道微冲刷、拦门沙滩顶仍保持淤积外移、口门外侧近海域冲刷的态势略有增强,而其影响原因与历史时期的自然因素影响为主略有差异,近期人类高强度活动的影响贡献率增大。首先,南支至南港和北港中上游河段河床普遍发生冲刷,河床沙活动较活跃,床面微地貌沙波发育更明显,而口门外侧海域地形略有冲刷蚀退,这些变化与流域来沙锐减有直接关系;北支、北港口门、南槽和北槽河道拦门沙河段呈淤积,尤其北槽主航道的拦门沙河段6m水深浚深为12.5m后回淤量很大,这些与拦门沙河道动力结构环境、河口和海域再悬浮泥沙补给有关;局部河段出现强冲和强淤现象,与近期河口工程建造有关。所以,长江河口近期正处在对自然因素变化和人类活动增强的自我缓慢地自动调整和适应过程之中。     

近70年珠江水沙变化特征及人类活动影响因素分析

收集1954—2019年珠江流域的3个主要水文站:高要站(西江)、石角站(北江)和博罗站(东江)的径流量与输沙量资料,运用Mann-Kendall非参数检验法和累积距平法,分析了珠江流域水沙近70年来的年际变化特征。结果表明,1954—2019年珠江年径流量变化趋势不明显,年输沙量呈下降趋势,高要站与博罗站年输沙量分别于2003年和1991年发生突变,多年平均输沙量较突变前分别减少了71.30%和48.88%,石角站未发生明显突变。2000—2019年珠江流域归一化植被指数(Normalized Difference Vegetation Index,NDVI)整体呈上升趋势,植被覆盖改善区域占流域总面积的89.27%,但NDVI与水沙变化的相关性不显著。运用双累积曲线法对不同时期人类活动对珠江输沙量的影响进行分析,20世纪80年代以来,森林砍伐、水库建设、水土保持等人类活动对输沙量造成显著影响,2000年以后龙滩水库建设是西江输沙量下降的主要原因,植被改善对于珠江流域输沙量的影响不明显。     

An influencing mechanism for ecological asset gains and losses and its optimization and promotion pathways in China

Journal of Geographical Sciences - Accounting for the gains and losses of ecological assets holds scientific significance in sustaining human well-being. Based on related research on ecological...     

Temporal and spatial variability of sediment flux into the sea from the three largest rivers in China

The Yellow, Yangtze and Pearl Rivers supply over 90% of the sediment flux from China to the western Pacific Ocean. Trends and abrupt changes in the water discharge and sediment load of the three rivers were examined and compared based on data updated to the year 2011 at the seasonal and annual scales. The total water discharge from the three rivers shows a statistically insignificant decreasing trend with a rate of 0.62 × 10⁹ m³/a, and the total sediment load shows a statistically significant decreasing trend at a rate of 31.12 × 10⁶ t/a from the 1950s to 2011. The water discharge of the entire Yellow River and the upstream portion of the Yangtze River shows significant decreasing trends, and that of the mid-lower stream of Yangtze River and the entire Pearl River shows insignificant trends. The sediment loads in the three river basins all show significant decreasing trends at the annual and seasonal scales, and a dramatic decrease in the 2000s resulted in a more obvious decreasing trend over the studied period. From the 1950s to the 2000s, the contribution of sediment flux from the Yellow River to the ocean decreased from 71.8% to 37.0%, and the contributions of the Yangtze and Pearl Rivers increased from 24.2% and 4.0% to 53.0% and 10.0%, respectively. Inter-annual variations in water discharge and sediment load were affected by climate oscillations, such as the El Niño/Southern Oscillation, and the long-term decreasing trend in sediment load was primarily caused by human activities. Dam constructions and soil conservation projects were the major causes of sediment reduction. From the 1970s to the 2000s, the decrease in total sediment load from the three rivers caused by climate change and human activities was 2.24 × 10⁸ t/a (23.0%) and 7.5 × 10⁸ t/a (77.0%), respectively. In the coming decades, the sediment flux from the three rivers into the sea will decrease further with intensifying human activities, resulting in many challenges for the management of river basins and river deltas.     

采动作用下上硬下软型缓倾岩质高边坡变形机理试验研究

我国西南岩溶山区地质环境复杂,地下开采活动频繁,大型崩滑灾害频发。为了了解上硬下软缓倾岩质边坡下覆矿层开采时坡体的沉降与地裂缝发育规律,以贵州普洒崩塌为例,通过相似模型试验,研究采动作用下,坡体的地表沉降、内部位移、层间压力变化规律、以及采动诱发的地裂缝发育情况。研究表明：在地下开采情况下,坡体地表沉降和内部位移随开采宽度增加呈线性增大;当开采宽度约为采高的16倍时,地表沉降突增,并伴随裂缝出现;测点越靠近地裂缝,沉降变化率越大,地裂缝发生位置与地表沉降变化率最大的测点大致出现在同一区域;掘进工作面推进时,采空区上方顶板岩层出现卸荷区域,压应力减小,而采动工作面煤层上方岩体出现层间挤压区域,压应力增加;采空区上方大于20倍采高范围以外,岩体层间压力受地下开采活动的扰动影响微弱。本研究为西南岩溶山区在地下采动作用下,对山体崩滑的早期识别与破坏机制分析具有一定的参考意义。     

江西信江白垩纪陆相盆地地质作用与构造演化

以现代地层学理论为指导 ,应用砾石成分的旋回变化、沉积物地球化学元素变化和岩浆活动类型变化的综合信息 ,论述了江西信江白垩纪陆相盆地的地层划分和中生代晚期的构造演化。     

辽东黄花甸地区古元古代花岗质岩浆作用及其地质意义

胶-辽-吉古元古代造山/活动带的辽东黄花甸地区出露大量古元古代花岗质岩石,前人将该区的花岗质岩石统称为花岗质混杂岩。本文通过详细的野外地质调查和室内综合研究,将该套花岗质混杂岩解体为时代及性质完全不同的两类花岗岩——黑云母二长花岗岩和花岗闪长岩。其中黑云母二长花岗岩具有块状、条痕状、片麻状的不同构造类型,均显示富SiO_2(72.37%~77.44%)、贫Al_2O_3(11.69%~13.21%)、富K_2O(3.97%~5.11%)的特征,Na_2O/K_2O=0.64~1.08,TiO_2含量在0.18%~0.34%之间,MnO、MgO和P_2O_5的含量较低,分别为0.01%~0.07%、0.12%~0.32%和0.01%~0.06%,铝饱和指数A/CNK集中分布在1.33~1.45之间,A/NK在1.49~2.60之间,属于过铝质高钾钙碱性系列;微量元素Sr、Ba、Ti、P强烈亏损,具有明显的Eu负异常,具有A型花岗岩的特征。黑云母二长花岗岩的锆石大部分为具有清晰震荡环带结构的岩浆锆石,从3个样品获得LA-ICP-MS锆石U-Pb谐和年龄分别为2185±29Ma、2183±13Ma、2166±10Ma,据目前所获得南辽河群碎屑锆石年龄(1.95~2.15Ga),本文认为黑云母二长花岗岩的侵位时代要早于南辽河群地层沉积的时间,构成了南辽河群地层沉积的基底。花岗闪长岩呈岩枝状侵入黑云母二长花岗岩和里尔峪组地层中,富SiO_2(72.54%~74.31%)、Al_2O_3(15.01%~16.17%),全碱(K_2O+Na_2O)平均7.77%,相对富钠(Na_2O/K_2O=1.27~2.82),贫钙、镁,MgO平均为0.26%,CaO平均为1.59%,Mg#值平均为54.0,铝饱和指数A/CNK集中分布在1.61~1.78之间,A/NK在1.49~2.60之间,属于过铝质钙碱性系列,具明显的Eu正异常,Y/Yb低,Sr/Y高,而且强烈亏损Th、Ta、Nb、Ti等高场强元素,富集Ba、K、Rb、Sr等低场强元素,具有埃达克质花岗岩的特征。花岗闪长岩的锆石大部分为具有清晰震荡环带结构的岩浆锆石,从2个样品获得LAICP-MS锆石U-Pb年龄分别为1995±18Ma、1995±13Ma。可以推断花岗闪长岩的侵位时代为2.0Ga左右。本文认为具有A型特征的黑云二长花岗岩是陆块内部拉伸减薄-裂解过程中下部地壳部分熔融的产物,具有埃达克质特征的花岗闪长岩是俯冲过程中所形成火山弧或活动大陆边缘岩浆活动的产物。以上研究表明胶-辽-吉古元古代造山/活动带可能经历了在2.2~2.15Ga左右的拉伸裂解过程和2.0Ga左右俯冲挤压的构造演化过程。     

1980-2007年新疆地区能见度的变化特征及其影响因子研究

在小风、无降水、无大雾等天气条件下,运用能见度累计百分率法和能见度均值法,分析了新疆15个城市1980-2007年间每日14时大气能见度的月分布特征、年际变化趋势及影响大气能见度的影响因子,结果表明:⑴ 新疆的能见度在夏季出现峰值,冬季降到最小值。北疆地区的能见度总体高于南疆地区。全疆能见度最高的城市是哈密,年均值为49.6km。和田最低,年均值仅为16.4km;⑵ 近28年来15个城市中只有阿勒泰、哈密、昌吉3个城市的能见度基本保持不变,北疆博乐、克拉玛依、伊宁、石河子、乌鲁木齐和南疆吐鲁番、阿克苏的能见度逐年降低,南疆阿图什、库尔勒、喀什、和田市的能见度缓慢增加;⑶ 从气象因素相对湿度、风速、降水、沙尘天气日数的年变化以及全疆经济发展中能源消费总量和能源加工转换总效率来看,15个城市的相对湿度、风速总体上没有呈现显著的变化,降水增多、沙尘天气减少促使南疆大部分城市的能见度逐步好转,而近年来的经济快速增长是导致北疆大部分地区能见度逐年下降的主要因素。     

A multimetric index for assessment of aquatic ecosystem health based on macroinvertebrates for the Zio river basin in Togo

The use of multimetric indices as tools for assessing aquatic ecosystem health in most of the developing countries such as Togo is still lacking. To fill this gap, we developed a macroinvertebrates-based multimetric index for the Zio river basin of Togo. Forty-two sites were assessed for the development and the validation of the Multimetric Index of Zio River Basin (MMIZB). Thirty-nine candidate metrics belonging to four categories (composition metrics, functional feeding metrics, diversity metrics and tolerance measure metrics) were evaluated. After comprehensive multiple selection procedure, six core metrics were retained to provide the final MMIZB. The results showed that the MMIZB responded to a set of organic pollution (chemical oxygen demand, ammonium, total suspended solid) and hydromorphological alterations, which corresponded to a set of gradients of human pressures affecting the ecological integrity of Zio river basin water bodies (r = 0.78, p < 0.001). The final macroinvertebrate index well distinguished the reference sites and impaired sites of a validation data set (p < 0.001) and showed a significant relationship between water and habitat quality based on Prati’s index (r = 0.73, p < 0.001) and Multimetric Macroinvertebrates Index of Vietnam (MMI_Vietnam) (r = 0.88, p < 0.001). This work underlines the relevance of the MMIZB as an effective tool for biological monitoring and decision making in water management of Zio river basin.     

远东中俄边界地区的火成活动

本文以远东中俄边界地区广泛发育的火成岩的研究为基础，对火成活动在地体构造学业伦历史中的构造背景、不同阶段的发育特点、形成的岩石组合和动力学机制６等作了探讨。得出地体构造从早及晚由挤压向伸展和走滑构造背景演化，相应发育一系有成因特征的火成岩。为古亚洲洋东段的构造演化提供了佐证。