The impact of extreme turbidity events on the nursery function of a temperate European estuary with regulated freshwater inflow     

E. González-Ortegón  M.D. Subida  J.A. Cuesta  A.M. Arias  C. Fernández-Delgado  P. Drake 《Estuarine, Coastal and Shelf Science》2010

Estuaries are used as nursery grounds by numerous marine species despite being usually subject to strong anthropogenic disturbances. Abundances of marine recruits (fish and crustacean decapods) and their main prey (mysids) were monitored by monthly sampling, from June 1997 to February 2009, in the lower reaches of the Guadalquivir estuary (SW Spain). During that period, unusually high and persistent turbidity events (HPTEs) were observed twice. Both HPTEs started with strong and sudden freshwater discharges after relatively long periods of very low freshwater inflow. Data from this time-series were used to test the hypothesis that HPTEs may negatively impact the nursery function of estuaries either by decreasing prey availability or by decreasing survival/arrival of marine recruits. During HPTEs, the commonest mysid (Mesopodopsis slabberi), a key species in the estuarine food web, showed a significant decrease in abundance. Likewise, some marine recruits that prey on M. slabberi and whose peaks of abundance within the estuary occur in summer–autumn (Engraulis encrasicolus and Pomadasys incisus) were less abundant during HPTEs. It is also suggested that HPTEs might have triggered a shift in the distribution of the most euryhaline prey (Neomysis integer) and predator (Dicentrarchus punctatus and Crangon crangon) species, towards more saline waters. This could have contributed to an increase in the inter-specific competition (for food/habitat) within the estuarine nursery area. The results discussed in this study call attention to the need to reduce as much as possible the anthropogenic pressures that may stimulate the occurrence of high and persistent turbidity events (HPTEs) in order to preserve the nursery function of temperate estuaries.  相似文献   

东濮凹陷沙三段致密砂岩储层裂缝形成机制及对储层物性的影响     

刘卫彬  张世奇  徐兴友  周新桂  李世臻  陈珊  白静 《大地构造与成矿学》2019,43(1):58-68

为探讨东濮凹陷沙三段储层裂缝的发育特征、形成机制、主控因素及其对储层的影响,综合运用岩心观察、薄片鉴定、扫描电镜、流体包裹体分析等方法对裂缝进行了研究。结果表明:东濮凹陷沙三段储层中发育的裂缝按规模可分为宏观裂缝和微观裂缝两大类,按成因可分为构造缝、超压缝和成岩缝。构造缝走向以NNE向、NE向为主,其形成可分为两期,分别为40～35 Ma沙河街组沉积中后期和25～18 Ma东营组沉积末期。超压缝的形成与膏盐脱水、烃类充注和膏盐层封堵作用有关,形成于33～25 Ma东营组沉积时期。压实作用、溶解作用、收缩作用等成岩作用均可形成微裂缝。裂缝的形成序列为:早期构造缝-压裂缝-溶解缝-超压缝-收缩缝-晚期构造缝-溶解缝-压裂缝;裂缝的发育可以改善储层物性,宏观裂缝主要起渗流作用,微观裂缝既可作为有效的储集空间,又可作为酸性流体流动通道,产生次生孔隙带,提高储层孔隙度。  相似文献   

重庆东温泉山既有隧道疏排对岩溶水的影响     

贺苏和巴特尔  蒋良文  张贵铜 《中国岩溶》2019,38(4):496-501

岩溶水径流路径非常复杂,而隧道疏排对岩溶水的影响更是一个长期复杂的过程。在长期观测数据以及实地调查研究的基础上,分析重庆东温泉山既有隧道疏排对岩溶水的影响,总结出水平流动带内隧道疏排岩溶水形成的降落漏斗一般可达到隧道标高附近,岩溶裂隙水带内隧道疏排岩溶水形成的降落漏斗仍保持在隧道上方一定高度,渗透性是隧道疏排对岩溶水影响的关键因素。   相似文献   

西北太平洋热带气旋生成数在1990年代中期发生突变的气候环境特征分析   总被引：1，自引：0，他引：1  

李德琳  肖子牛  周秀华  信飞 《热带气象学报》2015,31(3):323-332

利用CMA热带气旋(TC)最佳路径资料和NCEP再分析资料,分析1949—2013年西北太平洋(包括南海)TC生成数的变化特征,发现在1995年前后发生由偏多到偏少的显著突变。对影响TC生成的主要气候环境要素场进行对比分析表明,在1995年之后,虽然赤道西太平洋海表温度偏高,热带太平洋为类La Ni?a的异常海温型,但垂直上升运动减弱、对流层纬向风垂直切变幅度增大、海平面气压升高,均不利于TC的生成,其综合影响导致TC数目显著减少。对1995年前后两个时期TC生成多、少典型年份海洋大气环境场的对比分析表明,1995年以前热带海洋表面温度对TC生成有相对重要的影响,而1995年以后风场环境对TC生成的影响作用更重要。   相似文献   

Revisiting and rethinking regional urbanization in Changjiang River Delta, China   总被引：1，自引：1，他引：0  

Mark Yaolin WANG 《中国地理科学(英文版)》2012,22(5):617-625

China is entering a critical and accelerating phase of urbanization.As one of the most urbanized regions in China,the Changjiang(Yangtze)River Delta has experienced dramatic urbanization and urban transformation.However,in the recent years,many changes have taken place in this region and there is limited attention to the regional urbanization path evolution,its problems and the way to solve these problems.Therefore,we should revisit the urbanization process in the Changjiang River Delta again.In this paper,we revisited urbanization paths of the Changjiang River Delta by data analysis,influence factors of urbanization by the Gray Relational Analysis,and major challenges to urbanization of the Changjiang River Delta by theoretical considerations.We found that the urbanization of the Changjiang River Delta had experienced several stages of large-scale spatial and urban system restructuring.Within the Changjiang River Delta,Shanghai,Zhejiang and Jiangshu had experienced different urbanization path with local characteristics.But with their development model gradually converging,their urbanization model is also converging.We also found that the major influence factors affecting the Changjiang River Delta urbanization were dynamic change and urbanization was driven by different key factors in different socio-economic development stages.Meanwhile,the Changjiang River Delta urbanization is facing many problems such as existing institutional arrangements,including the hukou(household registration)system and others which can not meet the needs of current socioeconomic development and urbanization.Therefore,it is imperative to promote institutional innovation and adopt a new urbanization development strategy for the sake of the orderly and sustainable urbanization development in the Changjiang River Delta.  相似文献   

城市居住空间分异背景下青少年成长的邻里影响——以广州市鹭江村与逸景翠园为例   总被引：2，自引：1，他引：1  

孙瑜康  袁媛 《地理科学进展》2014,33(6):756-764

城市居住空间分异是现代城市社会阶层分化导致的普遍现象,西方许多研究证明这种特定人群集中居住的邻里会对其中的青少年的成长产生多方面的影响。本文以广州市鹭江村和逸景翠园社区为例进行对比研究,探究中国城市中不同邻里对居住在其中的青少年成长的影响。在此将邻里特征分为社会经济特征、家庭教育观念特征、同龄人交往特征、机构资源特征4 个方面,运用logistic 回归分析发现,上述4 个方面的邻里特征确实会对青少年的成长产生影响,其中社会经济特征对青少年的学习成绩有影响,家庭教育观念特征影响青少年的教育表现与心理状态,同龄人交往特征则对青少年性格有重要影响,机构资源特征会影响青少年发展机会的获得。而邻里影响的作用机制可以用Jencks等的邻里机构资源模式和群体社会化模式来解释。  相似文献   

中国周边地缘影响力的建模与测算——以南亚为例   总被引：2，自引：0，他引：2  

王淑芳  葛岳静  曹原  胡浩 《地理科学进展》2014,33(6):738-747

当今国际社会已经进入了大规模实力转移的时代,如何顺应当代国际关系中实力结构变化的趋势,科学合理地测度一国在周边地缘环境中的影响力,成为国家外交政策和周边战略研究的重要内容。本文基于权力理论、硬实力和软实力理论、相互依赖理论,在突出主导因素和可操作原则的基础上,构建了国家地缘影响力的指标体系,定量测算了近10 年来中国在南亚各国和南亚地区的地缘影响力。结果表明：①2012 年中国与南亚七国的综合实力比较,按照差距从小到大排序,分别为印度、巴基斯坦、孟加拉国、斯里兰卡、尼泊尔、不丹和马尔代夫。说明国家本身的地缘重量,尤其是硬实力依旧是综合实力的重要支撑。②近10 年来,中国在南亚地区的地缘影响力呈逐年上升趋势。其中,中国在不丹、孟加拉国和尼泊尔的地缘影响力最大,而在斯里兰卡和马尔代夫最小。表明地缘影响力受国家间地理位置的制约,呈距离衰减的空间分布。③国家的实力和地缘影响力并非成正比关系。国家实力强大并不能代表其对外的影响力就强大。④无论在政策制度、国家形象还是文化交流方面,中国与南亚各国间的软实力差距不大。  相似文献   

广东省城镇建设用地经济密度差异时空特征及影响机理   总被引：2，自引：0，他引：2  

王枫  汤惠君  杜继丰 《热带地理》2014,34(1):87-94

基于广东省21个地级市的城镇建设用地经济密度数据,利用ArcGIS空间分析、泰尔指数、重心模型等方法分析了1996―2008年广东省城镇建设用地经济密度差异的时空特征,并构建面板数据模型对其影响机理进行了探讨。结果表明：1）1996―2008年,广东省城镇建设用地经济密度总体差异波动增大,城镇建设用地经济密度重心向西北偏移;2）广东省各城市之间城镇建设用地经济密度差异显著,空间格局上存在较明显的集聚和峰值效应;3）广东省各城市之间城镇建设用地经济密度的相对发展速度差别较大,按基础水平和提高速度的差异划分为4种类型区,其中基础高密度提高较慢类型区和基础低密度提高较慢类型区涉及城市数量较多;4）随着产业结构的优化、资本与劳动力投入规模的增大、交通区位的改善和科技水平的提升,广东省城镇建设用地的经济效益将会得到不断提高。  相似文献   

页岩储层可压裂性影响因素及评价方法   总被引：9，自引：0，他引：9       下载免费PDF全文

唐颖  邢云  李乐忠  张滨海  蒋时馨 《地学前缘》2012,19(5):356-363

可压裂性是页岩在水力压裂中具有能够被有效压裂的能力的性质,是页岩开发中最关键的评价参数,影响因素包括页岩脆性、天然裂缝、石英含量、成岩作用及其他因素,目前常利用页岩矿物组成或岩石力学参数来表征,难以全面反映页岩在水力压裂过程中的综合性质。采用极差变换和经验赋值方法将参数标准化,使用层次分析法确定不同因数对可压裂性影响的权重,使用标准化值与权重系数加权得到可压裂系数的数学模型可对页岩可压裂性进行定量评价。可压裂系数越大,页岩可压裂性越强。采用该模型计算渝东南地区渝页1井龙马溪组页岩可压裂系数为0.485 5,Barnett页岩可压裂系数为0.484 4,总体处于同一水平;同时,使用该模型将页岩可压裂性分为3个级别,可压裂系数在0.132 0~0.282 0的页岩可压裂性低,水力压裂效果不佳;可压裂系数在0.282 0~0.456 7的页岩可压裂性中等,水力压裂能够取得较好的效果;可压裂系数在0.456 7~0.784 0的页岩可压裂性高,是优质的可压裂层。水力压裂应选择可压裂系数大于0.360 7的页岩。  相似文献   

Optical Response of the Atmosphere During the Caribbean Total Solar Eclipses of 26 February 1998 and of 3 February 1916 at Falcón state,Venezuela     

Peñaloza-Murillo  Marcos A. 《Earth, Moon, and Planets》2002,91(3):125-159

An investigation of the optical response of the atmosphere before, during, and afterthe total solar eclipse of 26 February 1998 at the Caribbean Peninsula of Paraguaná (Falcón State) in Venezuela, was made by measuring photometrically the intensity of the sky brightness in three strategic directions: zenith, horizon anti-parallel or opposite the umbra path, and horizon perpendicular to this path. From these measurements, and by applying in an inverse way an empirical photometric model, very rough estimations of theextinction coefficient, and also of the average optical depth, were obtained in one of these particular directions. However based on meteorological measurements such as those of relative humidity and temperature, and applying a different model, a better estimation in the visual of the total global extinction coefficient of the sky (except the horizon), were made considering the contribution of each component: atmospheric aerosol, water vapour, ozone and Rayleigh scattering. It is shown that this global coefficient is mostly dependent upon aerosol extinction. In spite of the strong reduction of sky brightness photometrically observed during the totality, the results show that the sky was not dark. This is confirmed by the results obtained for the total global extinction coefficient. Additionally it is estimated that the total solar eclipse that took place also in Falcón State, Venezuela, at the beginning of the last century on 3 February 1916, was 30% darker that the 1998 eclipse, and that atmospheric aerosol played a relevant and similar role in the scattering of sunlight during the totality as it was for 1998's. Visual observations made during each event, which show that at length only one or two bright stars could be seen in the sky, support the results obtained for both eclipses.  相似文献