海洋酸化对马氏珠母贝受精及早期发育的影响   总被引：1，自引：0，他引：1  

刘文广  林坚士 《海洋科学》2012,36(4):19-23

自2010年7月1日至3日,在pH值为8.1、7.7和7.4条件下研究了海洋酸化对马氏珠母贝(Pinctada martensii Dunker)受精及早期发育的影响。结果显示,海洋酸化对不同pH值下马氏珠母贝的受精率无显著影响。pH8.1、pH 7.7和pH 7.4试验组幼虫的壳长、壳高的值逐渐增大,pH 8.1组幼虫的壳长、壳高的值大于同期其他两组的值,且在实验的第24、36、48小时与其他两组同期幼虫的壳长、壳高的值差异显著,这表明海洋酸化显著影响马氏珠母贝幼虫的生长。实验期间,pH 8.1试验组幼虫的存活率和畸形率没有显著变化,而pH 7.7和pH 7.4组幼虫的存活率显著低于pH 8.1组。pH 7.4组幼虫的畸形率显著高于同期pH 8.1和pH 7.7组幼虫的畸形率,表明在海洋酸化的环境中幼虫的发育受到影响。本文将为海洋酸化的相关研究提供基础数据。  相似文献   

干旱区沙地长期培肥对土壤线虫群落特征的影响   总被引：2，自引：1，他引：1  

王雪峰  苏永中  杨晓  刘文杰  杨荣 《中国沙漠》2011,31(6):1416-1422

为了研究干旱区沙地长期培肥对农田土壤线虫群落结构的影响,通过定位实验设计5种培肥方式,采集分析土壤样品中的线虫群落组成特征。实验中共捕获线虫18 337条,归属22科30属。群落分析结果表明,施用有机肥促进线虫总数中植物寄生线虫（PP）比例的增加,瓦斯乐斯卡指数（WI）在M3处理中最低为0.98±0.22,有机肥增加了土壤线虫群落的物种多样性和营养类群多样性;长期施用化肥能够抑制植物寄生线虫（PP）,提高食细菌线虫（BF）和食真菌线虫（FF）在线虫总数中的比例,瓦斯乐斯卡指数（WI）在NPK3处理中最高为2.51±1.12,化学肥料降低了线虫群落的物种多样性和营养类群多样性,辛普森指数（Dom）和营养类群指数（TD）分别在NPK3处理中达到最低值0.13±0.01和2.34±0.07。线虫区系分析结果表明,合理的有机-无机肥配施有利于农田土壤生态系统的稳定健康发展。本研究从土壤生物学角度揭示了不同施肥措施对农田地下土壤生态过程的影响,对于保护干旱区土壤环境和农业的可持续发展具有重要意义。  相似文献   

The role of biophysical interactions within the ijzermonding tidal flat sediment dynamics     

Annelies De Backer  Carl Van Colen  Magda Vincx  Steven Degraer 《Continental Shelf Research》2010

This paper focuses on the importance of biophysical interactions on short-term and long-term sediment dynamics. Therefore, various biological (macrobenthos, photopigments, colloidal EPS) and physical parameters (grain size, water content, sediment stability, bed level) were determined (bi)monthly in nine sampling plots on the IJzermonding tidal flat (Belgium, 51°08′N, 2°44′E) during three consecutive years (July 2005–June 2008). Results showed that sediment stability varied on the short timescale and was directly influenced by biota, while bed level varied mainly on the long-term due to interannual variability. The short-term dynamic relationships between mud content, water content, fucoxanthin and macrobenthos density resulted in a seasonal mud deposition and erosion cycle, and directly influenced sediment stability. Moreover, macrobenthos was proven to be the most important parameter determining sediment stability. On the long-term, a shift was observed from high fucoxanthin/chla concentration, high mud content and zero to moderate densities of Corophium volutator towards low fucoxanthin/chl a and mud content and high Corophium densities, which resulted in a transition from net accretion to net erosion. However, most measured variables proved to be poor predictors for these long-term bed level changes, indicating that external physical forces, such as waves and storminess, probably were the most important factors triggering long-term sediment dynamics. Nevertheless, biota indirectly influenced bed level changes by mediating short-term changes in sediment stability, thereby influencing the erodability of the sediment. The macrobenthos, and especially the mud shrimp Corophium, was suggested as the (indirect) driving destabilising factor for the sampling plots in the IIzermonding when considering the long-term evolution.  相似文献   

坝基碎屑岩三轴蠕变特性及长期强度试验研究     

张玉  金培杰  徐卫亚  赵海斌  梅松华 《岩土力学》2016,37(5):1291-1300

基于物理和常规变形特性分析,认为某水电站坝基碎屑岩力学特性异常复杂,故采用岩石三轴伺服仪开展了系列的蠕变力学特性试验研究。首先,探讨了轴向、侧向及体积蠕变特性和速率变化规律;其次,分析了蠕变对偏应力-应变特性影响并开展了破坏岩样微细观电镜扫描试验;最后,在采用等时曲线簇法确定长期强度的基础上,以实际延性扩容为依据,认为岩石侧向体积扩容速率大于轴向压缩速率的临界点为快速蠕变破坏的标志,提出确定长期强度的新方法。结果表明,碎屑岩表现出显著的蠕变特性,蠕变曲线主要分为初始衰减和稳态蠕变两阶段,且最后一级应力施加后呈现加速蠕变现象;应力增加导致蠕变变形加剧,最终破坏表现出轴向压缩变形过大、体积延性扩容明显、稳态蠕变速率较大等特点,且蠕变速率与应力符合指数函数关系。岩样长期强度与三向稳态蠕变速率交点和侧向体积扩容应力阀值基本一致,为常规强度的54%～80%。试验结果旨在为相关岩石工程长期稳定分析及蠕变模型构建提供可靠的依据。  相似文献   

Essai de définition     

G. CASTANY  J. MARGAT 《水文科学杂志》2013,58(1):74-81

Abstract

The apprehension and elaboration of hydrological maps in parallel with the development of hydrogeological maps render inevitable at first a clarification of terminology, besides an examination of the whole problem concerning the mapping of the data relating to water. It states theoretical (limits and validity of mapping in this property) and practical problems (methods, cooperation and distribution of work between using specialists and organizations).  相似文献   

华北中部重力场的动态变化及其强震危险含义   总被引：3，自引：0，他引：3       下载免费PDF全文

祝意青  闻学泽  张晶  刘芳 《地球物理学报》2013,56(2):531-541

基于绝对和相对重力观测获得的区域重力场时、空动态变化,结合区域GPS测量资料与活动构造分析,本文研究了华北中部地区2009-2011年的重力场变化特征,讨论了该区域重力场动态变化的强震危险含义.结果主要表明:(1)华北中部的活动地块边界及部分重要活动断裂带两侧存在较大差异的重力场空间变化;其中,以山西断陷带北东段所在的晋冀蒙交界地区为中心,形成较大面积的重力负值变化区,且沿该区西北缘的NE向岱海-黄旗海断裂带以及东南缘的NNE向太行山山前断裂带附近分别形成重力变化的高梯度带,可能反映这些部位近年的构造或断裂活动显著.(2)不同时段的重力场差分动态演化图像可能反映了近年山西断陷带北东段(京西北盆-岭构造区)及其附近的重力场整体经历了"准均匀→非均匀→断陷带北段侧向显著变化→局部"硬化"的演化过程.(3)研究区重力场的时间累积变化图像可用"区域应力场增强→区域断裂与断块差异运动及变形增强→局部运动受阻"的过程进行解释.(4)研究区的一些重力异常部位存在中-长期强震危险背景.  相似文献   

华北汛期降水长期变化规律研究新进展          下载免费PDF全文

刘海文  袁帅  杨朝虹  武凯军  朱玉祥  林一骅 《大气科学学报》2022,45(5):700-712

华北汛期降水的年代际减少,一直是气候学领域关心的重要课题之一。本文扼要回顾了华北汛期旱涝研究的最新代表性成果,主要包括华北汛期起讫的客观识别、华北汛期降水多时间尺度的变化特征、华北汛期降水变化与大气遥相关型的关系,以及华北汛期降水量增多趋势的停滞等。在此基础之上,归纳和总结了该领域需要继续深入研究的问题,如：华北汛期起讫时间的统一性;在华北汛期降水年代际变少的归因分析中,其年际振荡成分衰减的物理原因;华北汛期降水年代际变多趋势停滞的原因;华北汛期降水何时恢复增多等科学问题。  相似文献   

Estimation and Long-term Trend Analysis of Surface Solar Radiation in Antarctica: A Case Study of Zhongshan Station     

Zhaoliang ZENG  Zemin WANG  Minghu DING  Xiangdong ZHENG  Xiaoyu SUN  Wei ZHU  Kongju ZHU  Jiachun AN  Lin ZANG  Jianping GUO  Baojun ZHANG 《大气科学进展》2021,38(9):1497-1509

Long-term,ground-based daily global solar radiation (DGSR) at Zhongshan Station in Antarctica can quantitatively reveal the basic characteristics of Earth’s surface radiation balance and validate satellite data for the Antarctic region.The fixed station was established in 1989,and conventional radiation observations started much later in 2008.In this study,a random forest (RF) model for estimating DGSR is developed using ground meteorological observation data,and a highprecision,long-term DGSR dataset is constructed.Then,the trend of DGSR from 1990 to 2019 at Zhongshan Station,Antarctica is analyzed.The RF model,which performs better than other models,shows a desirable performance of DGSR hindcast estimation with an R~2 of 0.984,root-mean-square error of 1.377 MJ m~(-2),and mean absolute error of 0.828 MJ m~(-2).The trend of DGSR annual anomalies increases during 1990–2004 and then begins to decrease after 2004.Note that the maximum value of annual anomalies occurs during approximately 2004/05 and is mainly related to the days with precipitation (especially those related to good weather during the polar day period) at this station.In addition to clouds and water vapor,bad weather conditions (such as snowfall,which can result in low visibility and then decreased sunshine duration and solar radiation) are the other major factors affecting solar radiation at this station.The high-precision,longterm estimated DGSR dataset enables further study and understanding of the role of Antarctica in global climate change and the interactions between snow,ice,and atmosphere.  相似文献   

凹凸棒石与Zn^2＋的长期作用研究   总被引：1，自引：0，他引：1  

谢晶晶  陈天虎  王健  谢巧勤  刘海波 《矿物学报》2011,31(4):738-741

以凹凸棒石与Zn2＋为例研究粘土矿物与重金属离子长期作用过程,并运用高分辨透射电镜和X射线衍射分析粘土矿物与重金属离子长期作用的次生物相。结果表明：Zn2＋与凹凸棒石的长期作用是一个二阶段的过程,初始阶段为快速吸附作用,其后表现为慢速沉淀反应。高分辨透射电镜和X射线衍射分析表明,凹凸棒石与Zn2＋的长期作用过程中,具有纳米矿物特性的凹凸棒石表面快速水化,提高了悬浮液的pH值,诱导Zn2＋水解沉淀。而后,凹凸棒石缓慢溶解释放Al3＋和SiO44-与Zn（OH）2沉淀反应,形成Zn-A1双氢氧化物和异极矿。这一结果对认识土壤环境中重金属与粘土矿物的作用及重金属的归宿具有重要意义。  相似文献   

Anthropogenic influences on shoreline and nearshore evolution in the San Francisco Bay coastal system   总被引：1，自引：0，他引：1  

Kate L. Dallas  Patrick L. Barnard 《Estuarine, Coastal and Shelf Science》2011

Analysis of four historical bathymetric surveys over a 132-year period has revealed significant changes to the morphology of the San Francisco Bar, an ebb-tidal delta at the mouth of San Francisco Bay estuary. From 1873 to 2005 the San Francisco Bar vertically-eroded an average of 80 cm over a 125 km² area, which equates to a total volume loss of 100 ± 52 million m³ of fine- to coarse-grained sand. Comparison of the surveys indicates the entire ebb-tidal delta contracted radially, with the crest moving landward an average of 1 km. Long-term erosion of the ebb-tidal delta is hypothesized to be due to a reduction in the tidal prism of San Francisco Bay and a decrease in coastal sediment supply, both as a result of anthropogenic activities. Prior research indicates that the tidal prism of the estuary was reduced by 9% from filling, diking, and sedimentation. Compilation of historical records dating back to 1900 reveals that a minimum of 200 million m³ of sediment has been permanently removed from the San Francisco Bay coastal system through dredging, aggregate mining, and borrow pit mining. Of this total, ∼54 million m³ of sand-sized or coarser sediment was removed from central San Francisco Bay. With grain sizes comparable to the ebb-tidal delta, and its direct connection to the bay mouth, removal of sediments from central San Francisco Bay may limit the sand supply to the delta and open coast beaches.  相似文献