夏季东海陆架不同水团对悬浮体物质组成及粒度分布的影响

基于2012年7月东海陆架水文及悬浮体粒度等实测数据,分析不同水团内悬浮体物质组成和粒度分布特征,并探究其影响因素,为查明东海陆架海区陆源沉积物输运扩散机制、揭示海底沉积物来源和成因机制等提供理论依据。结果显示:夏季东海陆架悬浮体由两部分构成,即≤128μm的无机颗粒和?128μm以浮游生物为主的颗粒,其平均体积浓度分别为3.5μL/L和8.4μL/L。悬浮体空间分布受到该海域水团类型的制约。长江冲淡水、台湾暖流表层水、台湾暖流深层水、台湾海峡暖水以及东海冷涡的悬浮体粒径均呈双峰分布,峰值位于27.7—74.7μm和391μm;苏北沿岸流影响海域悬浮体粒径呈单峰分布,小颗粒端含量极低。悬浮体粒度组成及其空间分布差异与水团挟带的无机颗粒、营养盐输送以及水体界面阻隔密切相关。其中,长江冲淡水挟带大量无机颗粒和营养盐进入东海,致使其无机颗粒和浮游生物含量均为研究区最高;苏北沿岸流经长距离扩散后挟带的无机颗粒大多已经沉降,因此无机颗粒含量在研究区最低,而其挟带的丰富营养盐,致使浮游生物含量为次高值;台湾暖流表层水、台湾暖流深层水、东海冷涡以及台湾海峡暖水中悬浮体均以无机颗粒为主,其中前三个水团的水体界面处浮游生物含量较高;不同水团垂向交界处常形成温、盐跃层,跃层能够抑制底层营养盐向表层的扩散,导致跃层位置成为浮游生物高含量区。     

The effect of shroud on vortex shedding mechanism of cylinder

In the present study, flow characteristics were investigated experimentally using particle image velocimetry technique (PIV) in a gap between a solid cylinder and a shroud to reveal the effect of shroud diameter (D_s) and porosity (β) on the vortex shedding mechanism of the cylinder. Porosity (varied from β = 0.3 to 0.7) and diameter ratio (D/D_s = 0.4, 0.5 and 0.6) were main parameters examined at a Reynolds number of Re = 5000. For the porosity values of β ≤ 0.5, it is observed that vortex formation of the cylinder occurs only in the gap and shroud produces its own wake flow patterns. Penetrating flow through the shroud extends the shear layers on the both sides of the shroud through the downstream direction and prevents the interaction of shear layers in the near wake region. The diameter ratio and the porosity are impactful on the wake flow patterns in outer region of the shroud since they are determinant of the penetrating flow rate. Force measurements were also performed in the air tunnel in order to reveal the effect of shroud on the drag coefficient of cylinder. It is found that the drag coefficient of the cylinders are reduced significantly by shrouds when compared with that obtained from the bare cylinder case. However, the drag coefficient of the cylinder together with the shroud is higher than the bare cylinder for all cases since the shrouds enlarge the area exposed to the flow.     

Analysis of CO2 Emissions and the Mechanism of the Industrial Enterprises above Designated Size (IEDS) in Resource-based Cities by Application of Geographical Detector Technology

Resource-based cities are the most important players in responding to climate change and achieving low carbon development in China. An analysis of relevant data (such as the energy consumption) showed an inter-city differentiation of CO₂ emissions from energy consumption, and suggested an influence of the Industrial Enterprises above Designated Size (IEDS) in resource-based industrial cities at the prefecture level and above in different regions. Then by geographical detector technology, the sizes of each influencing mechanism on CO₂ emissions from energy consumption of the IEDS were probed. This analysis showed that significant spatial differences exist for CO₂ emissions from energy consumption and revealed several factors which influence the IEDS in resource-based cities. (1) In terms of unit employment, Eastern and Western resource-based cities are above the overall level of all resource-based cities; and only Coal resource-based cities far exceeded the overall level among all of the cities in the analysis. (2) In terms of unit gross industrial output value, the Eastern, Central and Western resources-based cities are all above the overall level for all the cities. Here also, only Coal resource-based cities far exceeded the overall level of all resources-based cities. Economic scale and energy structure are the main factors influencing CO₂ emissions from energy consumption of the IEDS in resource-based cities. The factors influencing CO₂ emissions in different regions and types of resource-based cities show significant spatial variations, and the degree of influence that any given factor exerts varies among different regions and types of resource-based cities. Therefore, individualized recommendations should be directed to different regions and types of resource-based cities, so that the strategies and measures of industrial low carbon and transformation should vary greatly according to the specific conditions that exist in each city.     

Increase in medium-size rainfall events will enhance the C-sequestration capacity of biological soil crusts

Biological soil crusts(BSCs) play important roles in the carbon(C) balance in arid regions. Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs. The compensation-rainfall size for BSCs(the minimum rainfall amount for a positive net C balance) is assumed to be different with BSCs of different developmental stages. A field experiment with simulated rainfall amount(SRA) of 0, 1, 5, 10, 20, and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis. We found algae-lichen crust on the interdunes and crest, algae crust on the leeward side, and lichen-moss crust on the windward. Even a small rainfall(1 mm) can activate both photosynthesis and respiration of all types of BSCs. The gross ecosystem production, ecosystem respiration, and net ecosystem exchange were significantly affected by SRA, hours after the simulated rainfall, position on a dune, and their interactions. The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting. C-uptake and-emission capacity of all the BSCs positively correlated with rainfall size, with the lowest C fluxes on the leeward side. The compensation rainfall for a net C uptake was 3.80, 15.54, 8.62, and 1.88 mm for BSCs on the interdunes, the leeward side, the crest, and the windward side, respectively. The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm. The compensation-rainfall size is negatively correlated with chlorophyll content. Our results suggest that BSCs will be favored in terms of C balance, and sand dune stabilization could be sustained with an increasing frequency of 5-10 mm rainfall events in the desert-oasis transitional zone.-     

长江口邻近海域浮游植物粒级结构特征及其与环境的响应关系

浮游植物的分粒级研究是监测浮游植物特征的重要工具,对于深入了解浮游植物动态的作用也不容忽视。本文的研究目的在于揭示长江口邻近海域春秋季不同粒级的浮游植物分布动态,分析浮游植物粒级结构与环境因素以及浮游动物群落结构的关系。通过2010年春季和秋季对粒径分级叶绿素a浓度的现场调查研究发现：春季,浮游植物主要以微型浮游植物占优势;秋季,微微型浮游植物和微型浮游植物共同占优势。相关分析结果表明,温度和富营养化状况是影响微型和微微型浮游植物对总叶绿素a贡献的重要因素。浮游动物的摄食压力可能对小型浮游植物对总叶绿素a的贡献起着重要的作用。     

渤海沉积记录的末次冰期千年尺度古环境与古气候变化

末次冰期千年尺度古气候变化事件在全球大部分载体中均有不同程度的记录,但在海岸带-陆架区的沉积记录中该事件还未见有报道。对取自渤海的BH08孔上部26m的岩芯进行了高分辨率粒度测试与分析,结合AMS 14C测年结果和微体古生物特征,探讨了研究区末次冰期以来古环境和古气候变化。运用粒级-标准偏差法对粒度数据进行研究,发现BH08孔敏感组分(88.4~148.7μm)的变化记录了末次冰期D-O(Dansgarrd-Oeschger)旋回冷暖事件:在暖期时敏感粒级粗组分(88.4~148.7μm)的含量低,而在冷期时含量高,且可以与反映东亚夏季风的指标对应。在暖期时,强盛的夏季风带来丰富的降水,增加的径流可以将粗粒沉积物搬运至更远的下游区,且暖湿气候有利于植被的发育,使得流域内粗粒沉积物减少;而在冷期呈现相反的变化趋势。我们推测,在末次冰期低海面的背景下,格陵兰和北大西洋等高纬地区气候变化导致大气环流和/或洋流系统发生改变,从而对东亚夏季风降水的调控造成河流输入物质的变化可能是造成BH08岩芯敏感组分变化的主要原因。     

鸭绿江端元粒度分级样品常量元素控制因素分析及物源识别

对鸭绿江河口表层沉积物陆源组分进行了水动力敏感粒度分级,以消弱"粒度效应"对沉积物地球化学组成的影响。通过多元统计方法,对不同粒级样品内常量元素含量特征、控制因素、源区特征等内容进行了探讨,并与全样测试结果进行对比分析。结果表明:源区化学风化程度是控制常量元素分布的主要因素,"粒度效应"和表生环境下的自生作用对常量元素的分布也有一定的控制作用,但"粒度效应"主要控制8μm以下样品内元素分布;源区目前处于以斜长石风化为主的中等化学风化程度阶段,风化产物未遭受钾交代影响;Al2O3、Fe2O3、MgO、MnO、TiO2、P2O5六种元素在>63μm、32~63μm和8~32μm 3个粒级内含量相近,8μm以下样品随粒级减小元素含量显著增加,CaO、Na2O两种元素在各粒级内含量分布特征与上述6种元素相反,高K2O含量且未受"粒度效应"控制,可作为鸭绿江端元的指示性元素。根据流域岩性特征分析,>2μm粒级样品可能主要来自鸭绿江中下游地区变质基底和花岗质侵入体的风化产物;而<2μm粒级样品则可能主要来自鸭绿江上游地区基性侵入体的风化产物。此外,对比分析还表明,全样测试结果仅相当于分粒级样品的均值水平,极大地掩盖了不同粒级内元素地球化学特征的差异性和规律性。因此,在利用全样地球化学特征进行物源示踪时需综合考虑。     

南海北部陆架坡折附近表层沉积物的粒度特征和其输运趋势

对南海北部陆架坡折附近取的50个表层沉积物样品,作粒度测试,计算粒度参数。粒度分析表明研究区的沉积物主要存在4种类型:含砾砂、砾质砂、砂质砾和含砾泥质砂;沉积物组分中砾石和砂占绝对优势,基本上不含黏土。综合因子分析和聚类分析的结果把研究区划分为4类沉积区:Ⅰ类沉积区属于内陆架沉积区,Ⅱ类沉积区属于陆架坡折上部沉积区,Ⅲ类沉积区属于陆架坡折下部沉积区,Ⅳ类沉积区区属于陆架边缘沉积区,每类沉积区都代表着不同的沉积环境。研究区沉积物的粒径趋势分析结果显示,陆架坡折附近的沉积物主要向内陆架和外陆架边缘或上陆坡输运,同时存在着跨陆架输运和沿陆架坡折输运现象,这与研究区实测的底流方向相一致。本研究表明,南海北部陆架坡折附近的沉积环境和沉积物输运模式比较复杂和特殊。本研究对今后陆架和陆坡区其他相关的研究具有十分重要的指导和借鉴意义。     

走向大中小城市协调发展的中国新型城镇化格局——建国以来中国城市规模分布演化与影响因素

为了落实国家新型城镇化规划提出的大中小城市协调发展战略,对1952-2014年中国城市规模分布指数进行演化分析,并在时间序列分析基础上探索了影响因素。结果表明,2000年以来,中国城市规模分布一改长期的分散化趋势,正走向集中化;人口规模增长、政策干预以及城市之间信息和交通成本的节约,都促使城市规模分布分散化;人均GDP长期以来促进了城市规模分布的集中,但近年来开始促进分散化;对外开放水平则主要促进分布的集中。未来应以全国适度均衡发展作为指导方针;远期以市场一体化,近期以共赢互利机制建设为抓手,促进城市群内大中小城市协调分工,优势互补;注意政策的稳定性和长期性,减少城市化格局的人为波动。     

玉兔号月球车巡视点矿物丰度及粒径分布高光谱反演

矿物的类型、丰度及其粒径分布对理解月球和行星表面曾经存在过怎样的地质演化过程具有重要的意义。本文提出基于辐射传输模型和稀疏分解模型反演矿物丰度及其粒径分布的方法,利用辐射传输模型计算各矿物端元不同粒径的单次散射反照率以构建解混光谱库,然后基于稀疏分解算法得到在每个可观测像元的端元最优丰度和粒径分布。利用实验室测量数据进行验证,表明本文方法具有较高的精度。最后根据玉兔号月球车的实地测量光谱数据,利用本文方法获得了其矿物的丰度及粒径分布,结果显示,辉石、橄榄石、斜长石、熔融玻璃和钛铁矿的丰度在4个观测点的平均丰度分别为28.1%、4.5%、39%、28%、0.4%,辉石的平均粒径为166.02μm,橄榄石为8.34μm,斜长石为196.31μm,熔融玻璃为44.21μm,一定程度上表明在这些观测点不同矿物对太空风化的响应不同。