Asynchrony of spring phytoplankton response to temperature driver within a spatial heterogeneity bay of Three-Gorges Reservoir, China

The increased air temperature is expected to have important driver on spring phytoplankton dynamics. To test whether spatial heterogeneity modifies the synchronous responses of phytoplankton to regional temperature driver, we evaluate temporal coherences for physical factors (temperature, water stability and non-algal light extinction), nutrients (nitrogen, phosphorus and silicon), and biomass and density of phytoplankton by Pearson correlation analysis and synchrony for phytoplankton community dynamics by Mantel test and nonmetric multi-dimensional scaling (NMS), during spring bloom (February 23–April 28, 2005) within Xiangxi Bay, a high spatial gradient bay of Three-Gorges Reservoir (China). The high level of temporal coherences for surface water temperature (r = 0.946, p < 0.01) and relative water column stability (r = 0.750, p < 0.01) were found between pair sites (A and B), in which the increase trends occurred with increase in regional air temperature during the study period. However, the low synchrony for phytoplankton dynamics were indeed observed between Site A and B, especially for the density of common dominant taxa (Cyclotella spp.: r = 0.155, p = 0.388) and community structure (Mantel test: r = 0.351). Moreover, the local habitat characteristics such as nutrient (nitrogen and phosphorus) and non-algal light extinction showed low levels of temporal coherence. It indicated that local community of phytoplankton varies rather independently within the single lentic bay with high spatial heterogeneity and that dispersal of algal organisms among locations cannot overwhelm out these local dynamics. Contrary to many studies, the present results argued that, in a small geographic area (i.e., a single reservoir bay of approximately 24 km length), spatial gradients also may influence spring phytoplankton response to regional temperature driver.     

Preface to the Special Issue on Antarctic Meteorology and Climate:Past,Present and Future

<正>The Antarctic, including the continent of Antarctica and the Southern Ocean, is a critically important part of the Earth system. Research in Antarctic meteorology and climate has always been a challenging endeavor. Studying and predicting weather patterns in the Antarctic are important for understanding their role in local-to-global processes and facilitating field     

凉山地区防雹作业雷达回波判据指标分析

本文利用四川凉山地区三类雹云降雹过程的雷达回波资料,对各类冰雹个例的回波强度、回波顶高、强回波中心高度以及垂直积分液态含水量等主要特征参数及随时间变化进行了分析。结果表明,雹云回波强度、回波云顶高和垂直积分液态含水量等参数的跃增、骤降是人工防雹作业预警的重要参考指标,回波强度和垂直积分液态含水量出现减小趋势维持时间一般为2个体扫后(约12分钟),地面将发生降雹,这一分析结果为本地区人工防雹可能的最佳作业时机和雷达回波判据指标的选择有了初步认识。     

The integrated impacts of natural processes and human activities on groundwater salinization in the coastal aquifers of Beihai,southern China

Salinization in coastal aquifers is usually related to both seawater intrusion and water–rock interaction. The results of chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai, southern China. The concentrations of the major ions that dominate in seawater (Cl^?, Na⁺, Ca²⁺, Mg²⁺ and SO ₄ ^2– ), as well as the isotopic content and ratios (²H, ¹⁸O, ⁸⁷Sr/⁸⁶Sr and ¹³C), suggest that the salinization occurring in the aquifer of the coastal plain is related to seawater and that the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization has occurred in an area that is significantly influenced by land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds are identified in the shallowest confined aquifer (I) in the middle of the area (site BBW2). Leakage from this polluted confined aquifer causes the salinization of groundwater in the underlying confined aquifer (II). At the coastal monitoring site (BBW3), confined aquifer I and lower confined aquifer II are heavily contaminated by seawater intrusion. The weak connectivity between the upper aquifers, and the seaward movement of freshwater, prevents saltwater from encroaching the deepest confined aquifer (III). A conceptual model is presented. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for the planning and sustainable management of groundwater resources in this region.     

平度市海水入侵成因及防治对策

平度市北胶莱河沿岸由于遭受海水入侵的影响,给工农业生产和人民生活造成了严重的危害。通过调查分析平度市北胶莱河沿岸海水入侵的现状和特点;针对海水入侵的演化特征分析了海水入侵的形成原因,并分析海水入侵造成的危害,提出相应的防治对策。     

济南玉符河重点渗漏带岩溶地下水补给特征与保护

玉符河是济南趵突泉域的重点渗漏带之一,是天然河道型渗漏带,其流域面积较大,具有较好来水条件,且卧虎山水库与锦绣城水库水系联通工程使其具备调水补源的条件,能通过增加外调补水增加重点渗漏带的补水能力。文章根据渗漏补给功能特征,采用RS、GPS、GS、物探测量、水文地质试验等技术手段,利用岩性、构造、地形、渗透性、植被覆盖度五大矢量数据的叠加分析方法,以主河道为中心划定玉符河重点渗漏带的保护范围,并利用变化参数法计算出玉符河重点渗漏带多年平均天然地下水补给量约为1 290万m³,其是岩溶地下水的重要补给来源。玉符河重点渗漏带的补水效果主要是通过提升西郊区域岩溶地下水水位,阻止趵突泉南部山区地下水向北径流过程中的向西分流,使地下水集中向泉水出露区汇聚,从而增大泉水的出流量。在保护渗漏带自然入渗功能的前提下,可充分挖掘玉符河重点渗漏带的补水功能,通过调水补源、河道生态修复、入河污染控制等措施,增大玉符河重点渗漏带的渗漏补给量。     

基于RS和GIS的地质灾害易发性定量评价:以湖北省五峰县为例

根据地质灾害的群发性和区域性的特点,运用地质统计学理论,通过分析,选取研究区内致灾因子,采用信息量模型进行地质灾害易发性定量评价。文中采用地质统计学信息量法,以GIS技术和RS技术为基础,从致灾机理上对各致灾因子进行选取和分析,使用GIS空间分析技术,完成了地质灾害易发性分区定量分析。分析结果表明,研究区内:(1)软硬相间碳酸盐岩类、(2)与河谷距离50～350m的斜坡带、(3)软硬相间碎屑岩类、(4)公路两侧1km范围、(5)斜坡在断裂带影响范围以内(1km)、(6)与河谷距离<50m或350～550m等6大影响因子对地质灾害的发生起主导作用。其中,除"公路两侧1km范围"为人类工程活动外,其他因素均为地质动力作用。研究完成的五峰县地质灾害易发分区定量评价,为五峰县的经济发展和城镇规划提供了科学依据,同时为以后在鄂西南地区进行地质灾害遥感解译提供了参考。     

松辽盆地白垩系青山口阶缺氧事件层的有机地球化学特征

松辽盆地白垩系青山口阶下部广泛分布一套富含有机碳的黑色泥岩、页岩沉积,它具有干酪根碳同位素正偏、重排甾烷含量低,普遍存在伽马蜡烷生物标志化合物等有机地球化学特征,代表了白垩纪温室效应时间窗内古湖泊贫氧环境条件下的沉积产物。结合生物地层研究成果,认为青山口阶下部曾发生过古湖泊缺氧事件,其层位大体可与白垩纪古海洋Cenomanian-Turonian界线事件层进行对比,由此提出了松辽盆地青山口阶下部的时代归属于晚白垩世Cenomanian晚期—Turonian早期的新观点。     

中国东部大陆尺度地球化学走廊带碳酸盐岩稀土元素分布特征与影响因素

碳酸盐岩是地球表层岩石圈的重要组成部分,其化学组成可提供沉积环境与海洋水体演化等信息,然而,前人对碳酸盐岩中稀土等元素的分布与变化特征关注不足。本文选择穿越中国东部6个一级大地构造单元的3条地球化学走廊带,系统采集了582件碳酸盐岩地层样品,并准确分析了包括稀土元素(REE)在内的81项指标的含量。结果表明,中国东部地球化学走廊带碳酸盐岩稀土元素(REE＋Y)总量为(0.59～183)×10-6,均值为24.0×10-6,纯净碳酸盐岩(CMC含量≥99％)均值为4.80×10-6。PAAS标准化后其显示具有轻稀土相对于中稀土和重稀土略亏损、δEu轻微正异常、δCe中度负异常等特征。白云岩中稀土含量、LREE/HREE值一般低于石灰岩;砂泥质含量相近时,前中生代各时代碳酸盐岩稀土分布模式相差不大,各构造单元稀土分布特征基本相似;与其他时代相比,中生代及中新元古代碳酸盐岩具有相对较平坦的稀土分布模式。研究表明,碳酸盐岩中稀土分布受碎屑物质影响明显,表现为稀土元素含量与碳酸根负相关,与碎屑物质相关元素(Si、Ti、Rb、Cs、Th、Zr等)、黏土相关元素(Al、Fe、K等)等正相关。成岩过程及白云化过程对较纯净碳酸盐岩中稀土分布特征影响不明显。我国古生代纯净碳酸盐岩分布模式受控于海相环境,其分布模式与现今海水相近;中生代纯净石灰岩受到陆相或海陆交互相的影响,具有较平坦的稀土分布模式。氧化还原条件对δCe的影响较δEu更为明显,δCe值受海相环境控制,极端正异常值(δCe＞1.3)受到还原环境或/和热液影响。若假定海水中REE自中元古代至今无太大变化,各时代稀土元素分配系数均值介于103.55～102.39,分配系数差异是造成碳酸盐岩中轻稀土亏损、Ce负异常及Y正异常的主要原因。微生物(席)可富集稀土等金属元素并改变沉积环境,这可能是造成中新元古界碳酸盐岩较平坦的稀土分布模式的主要原因。     

中国东北松辽盆地晚白垩世青山口组浮动天文年代标尺的建立

松辽盆地上白垩统青山口组主要由深湖相黑色泥岩、页岩组成,是大庆油田最重要的烃源岩之一,但长期以来对其年代学框架存在很大争议。对松辽盆地"松科1井"南井(茂206井)自然伽马测井和密度测井数据进行小波分析和连续滑动窗口频谱分析,表明茂206井青山口组记录了稳定的Milankovitch旋回。由长、短偏心率、地轴斜率和岁差周期造成的地层旋回厚度分别为39、13.5~9、5~3.8和2.5~1.7m。茂206井青山口组沉积速率变化不大,平均沉积速率为9.63cm/ka,沉积时限为5.16Ma。通过对长、短偏心率周期进行高斯带通滤波,建立了茂206井青山口组的"浮动"天文年代标尺。青山口组共记录了12.7个长偏心率周期和47.7个短偏心率周期。确定出青山口组1段下部油页岩层段对应的古湖泊缺氧事件(LAE1)持续时间约为250ka,与白垩纪Cenomanian-Turonian时期第二次大洋缺氧事件(OAE2)的持续时间接近。青山口组天文年代标尺的确立为约束青山口组沉积期各种地质事件的持续时间提供了年代学依据。