Density effects on solute release from streambeds

Contaminants that entered the streambed during previous surface water pollution events can be released to the stream, causing secondary pollution of the stream and impacting its eco-environmental condition. By means of laboratory experiments and numerical simulations, we investigated density effects on the release of solute from periodic bedforms. The results show that solute release from the upper streambed is driven by bedform-induced convection, and that density effects generally inhibit the solute release from the lower streambed. Density gradients modify the pore water flow patterns and form circulating flows in the area of lower streambed. The formation of circulating flows is affected by density gradients associated with the solute concentration and horizontal pressure gradients induced by stream slope. The circulating flows near the bottom of the streambed enhance mixing of the hyporheic zone and the ambient flow zone.     

近三十年保安湖大型底栖动物群落结构演变及其构建机制

保安湖是江汉湖群的一个典型浅水湖泊。近几十年来,随着经济的快速发展,保安湖面临多重人类压力影响,富营养化问题日趋严重。历史上曾开展过数次的保安湖底栖动物调查,但有关群落结构的长期变化及其驱动机制改变的认知仍为空白。本研究基于30余年（1986 2019）的多次调查数据,探索保安湖底栖动物的群落演变规律及其群落构建机制。研究共记录保安湖底栖动物5门10纲25目49科110属170种（历史记录154种,现场调查51种）。总物种数由1992年的107种降为2019年的51种;平均密度由1992年的433 ind．/m2增加到2019年的2177.6 ind．/m2;平均生物量由2001年的160.6 g/m2降低为2019年的26.7 g/m2。优势种在1987年有寡毛类、水生昆虫和软体动物多个类群,其后逐步演变为现阶段少数几种耐污的寡毛类和摇蚊类,如霍甫水丝蚓（Limnodrilus hoffmeisteri）、中国长足摇蚊（Tanypus chinensis）、红裸须摇蚊（Propsilocerus akamusi）等,而多年生大型软体动物衰退明显。PERMANOVA和SIMPER分析结...     

山西数字台网震级测定方法研究

震级是表示地震本身大小的一个量度,也是地震的基本参数之一。利用山西数字测震台网2009-2016年ML≥3.5以上宽频带数字地震资料,对近震震级ML、面波震级MS、宽频带面波震级Ms(BB)和矩震级Mw的震级测定方法进行讨论研究和对比,认为新震级标度能发挥宽频带数字地震资料的优越性,有利于资料的交换利用及对外发布。     

爆炸当量估算的初步研究

爆炸当量是评估爆炸能量的重要参数,快速估算爆炸当量对于有效开展应急救援工作至关重要。收集攀枝花铁矿爆破、宁夏煤矿爆破、河南汝阳钼矿爆破等矿山爆破资料,得到爆破的地方性震级M_L与爆炸当量Y之间的经验关系,并据此估算2019年7月19日河南省三门峡市气化厂爆炸事故的爆炸当量为16 t左右。     

Cyclical one-way continental rupture-drift in the Tethyan evolution: Subduction-driven plate tectonics

Numerous continents have rifted and drifted away from Gondwana to repeatedly open ocean basins over the past-500 millionyears.These Gondwana-derived continents drifted towards and collided with components of the Eurasian continent to successively close the preexisting oceans between the two.Plate tectonics satisfactorily describes the continental drift from Gondwana to Eurasia but does not define the geodynamic mechanism of continuously rifting to collisions of continents in the Tethy an Realm.After reappraisal of geological records of the rift,collision and subduction initiation from the surface and various geophysical observations from depth,we propose that Eurasia-directed subducting oceanic slabs would have driven Tethyan system in the Phanerozoic.The Eurasia-directed subduction would have dragged the passive Gondwana margin to rift and drift northwards,giving birth to new oceans since the Paleozoic.The closure of preexisting oceans between the Gondwana-derived continents and Eurasia led to continental collisions,which would have induced the initiation of oceanic subduction in the Tethyan Realm.Multiple episodic switches between collision-subduction-rift repeatedly led to the separation of continental fragments from Gondwana and dragged them to drift towards Eurasia.The final disappearance of Neo-Tethy s would have induced collision of the Gondwana-derived continents with the Eurasian continent,giving rise to the Cenozoic Alpine-Zagros-Himalayan collisional system.Therefore,the Eurasia-directed oceanic subduction would have acted as a 'one-way train' that successively transferred the ruptured Gondwana continental fragments in the south,into the terminal in the north.In this regard,the engine of this "Tethyan one-way train" is the negative buoyancy of subducting oceanic slabs.     

直流弧光放电等离子体CVD金刚石薄膜中的晶体类型与特征

采用自主研制的直流弧光放电等离子体CVD设备,以甲烷和氢气为气源,在YG6硬质合金基体上制备出主显晶面为（100）、（111）以及纳米晶粒的金刚石薄膜涂层。SEM观测其晶体类型主要为立方体、八面体、立方八面体,其中以立方八面体为主。随着碳源气体浓度的增加,金刚石晶体的形态会呈现从八面体一立方八面体一立方体顺序转变的趋势;而薄膜的表面形貌呈现从主显（111）晶面-（111）与（100）晶面混杂-主显（100）晶面顺序转变的特征。此外,CVD金刚石薄膜中还存在有许多类似接触孪晶、贯穿孪晶、复合孪晶,以及球形或聚晶晶粒形态的晶体,并且多数孪晶属于类似（111）复合孪晶结构。     

长江中游网湖百年花粉序列及其沉积动力和环境特征

本文研究长江中游网湖钻孔百年来的花粉沉积序列,分析花粉沉积近、现代过程以及其与沉积粒度、过去百年湖泊由开放水系到封闭湖泊的气候、水文动力变化的关系.研究表明,花粉浓度、类型与沉积粒度的变化特征以及聚类分析反映出网湖经历了湖泊水系通江与封闭两个重大阶段变化,其花粉序列变化与沉积粒度、区域降水以及长江流量在时间序列上也具有显著的相关性.主要孢粉类型,包括陆生松属、常绿栎/落叶栎、乔灌木花粉、湿生莎草科、水生和陆生草本花粉、以及蕨类孢子,与沉积物粒度和降水具有同步相关的年份占过去130年的27%-40%,与1960年湖泊封闭以前长江流量的同步相关达到47%-57%,反映出花粉沉积量的变化受到了沉积粒径和流域降水量的影响.花粉类型对沉积和气候具有不同的响应关系,表现出具有大于降水70百分点年份以粘土沉积为主、乔灌木花粉占优的多水年模式,和小于降水30百分点的年份以粉砂沉积为主、水生、湿生、陆生草类花粉增加的少水年模式.花粉沉积与水动力这个关系为认识湖泊碎屑和利用花粉沉积记录反演过去环境变迁、生物湖泊沉积机制提供科学依据.     

内陆河流生态环境需水量定量研究

在有限的水资源中,必须维持合理的生态环境需水量,以满足国民经济持续发展和生态平衡维护的需要,以内陆河流为对象,以生态学理论和水环境容量理论为基础,从维持河流系统水生生物生存、维持水体一定量稀释自净能力以及防止河流水面净蒸发损失的角度出发,分析计算了河流系统的生态环境需水量,以期为水资源合理配置提供科学依据。