氯化物水型盐碱池塘浮游植物叶绿素a的研究   总被引：3，自引：0，他引：3  

赵文  董双林  戴昀娣  张美昭  张兆琪 《湖泊科学》2000,12(3):247-254

于 1997年 4月至 1998年 9月对山东省高青赵店渔场 ( 37°17′N,117°55′E)的盐碱池塘叶绿素进行了调查研究 .结果表明 ,盐碱池塘叶绿素总量平均为 115.12μg· L-1,叶绿素 a平均含量为 73.90μg· L-1,占叶绿素总量的 61.76% ,叶绿素 b和叶绿素 c分别占总量的 12 .97%和2 5.2 7% .叶绿素 a含量的季节变动较大 ,有明显盛夏和初秋高峰期 .无鱼对照池的叶绿素 a比养鱼池塘低得多 .叶绿素 a的昼夜变化与垂直分布变化较大 ,但不遵循同一模式 .盐碱池塘叶绿素 a含量与浮游植物生物量、水温、总氮、总磷和硅酸盐显著正相关 ,与透明度显著负相关 ,而与盐度、碱度、p H、硬度、电导率均无规律性联系  相似文献   

基于通径分析法的太湖蓝藻水华定量气象评估模型     

杭鑫  李心怡  谢小萍  李亚春 《湖泊科学》2019,31(2):345-354

利用2005-2017年太湖周边区域气象观测资料和基于遥感解译的蓝藻水华信息,基于信息量权数法构建太湖蓝藻水华影响程度指数（简称为蓝藻指数）,应用通径分析法,分析年平均气温（T_y）、1-3月平均气温（T_1-3）、年降水量（R_y）、6-7月降水量（R_6-7）和年高温日数（D_Tmax）5个气象因子对蓝藻水华影响的直接效应和间接效应,在此基础上构建太湖蓝藻水华气象评估模型.结果表明,2007年蓝藻指数值最大,为0.759,2017年其次,为0.709,2009年最小,仅为0.113,蓝藻指数与实际情况基本相符;直接通径系数中T_y和T_1-3为正值,其余为负值,表明T_y和T_1-3对蓝藻水华的发生发展具有正效应,而R_y、R_6-7和D_Tmax具有负效应,总通径系数绝对值排序为：T_y > T_1-3 > R_y > R_6-7 > D_Tmax,由此可以反映各气象因子对蓝藻水华影响程度的权重.根据模型计算的综合气象指数与蓝藻指数之间的相关系数达0.826,通过0.01显著性检验,根据百分位法将蓝藻指数和气象指数进行等级划分,分类总精度为84.6%,其中中度以上达90.9%,表明模型能够较好地反映综合气象因子与蓝藻水华发生发展程度的关系,在水体富营养化程度没有明显改善的情况下,可用于太湖蓝藻水华定量气象评估.上述研究结果有助于更好地理解环境因子、尤其是气象因子在蓝藻生长和水华形成机制中所起的作用,从而为太湖蓝藻水华的监测、预测预警和精细化防控提供理论依据.  相似文献   

Mid‐MIS3 climate inferred from reconstructing the Dalijia Shan ice cap,north‐eastern Tibetan Plateau          下载免费PDF全文

JIE WANG  HANG CUI  JONATHAN M. HARBOR  LIMIN ZHENG  PAN YAO 《第四纪科学杂志》2015,30(6):558-568

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一种北斗卫星钟差短期预报新方法     

柴伟杰  杭芬  刘国光 《测绘通报》2020,(3):78-82

为提高北斗卫星的定位与授时精度，必须准确计算出卫星钟差数值。本文考虑北斗卫星钟差中随机部分误差的影响，尝试建立北斗卫星钟差拟合推估模型，根据拟合推估两步极小解法解算该模型，在求解协方差函数系数中，依据模型残差拟合多项式系数；并与常用的灰理论模型、拟合推估的正常解法钟差预报模型结果进行比对，算例结果表明了两步极小解法及拟合推估模型在北斗卫星钟差短期预报方面的有效性。  相似文献   

Lateglacial cryptotephra detected within clay varves in Östergötland,south‐east Sweden          下载免费PDF全文

A. MACLEOD  L. BRUNNBERG  S. WASTEGÅRD  T. HANG  I. P. MATTHEWS 《第四纪科学杂志》2014,29(7):605-609

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The First Observed Cloud Echoes and Microphysical Parameter Retrievals by China's 94-GHz Cloud Radar   总被引：1，自引：0，他引：1       下载免费PDF全文

WU Juxiu  WEI Ming  HANG Xin  ZHOU Jie  ZHANG Peichang  LI Nan 《Acta Meteorologica Sinica》2014,28(3):430-443

By using the cloud echoes first successfully observed by China's indigenous 94-GHz SKY cloud radar, the macrostructure and microphysical properties of drizzling stratocumulus clouds in Anhui Province on 8 June2013 are analyzed, and the detection capability of this cloud radar is discussed. The results are as follows.(1) The cloud radar is able to observe the time-varying macroscopic and microphysical parameters of clouds,and it can reveal the microscopic structure and small-scale changes of clouds.(2) The velocity spectral width of cloud droplets is small, but the spectral width of the cloud containing both cloud droplets and drizzle is large. When the spectral width is more than 0.4 m s-1, the radar reflectivity factor is larger(over –10 dBZ).(3) The radar's sensitivity is comparatively higher because the minimum radar reflectivity factor is about–35 dBZ in this experiment, which exceeds the threshold for detecting the linear depolarized ratio(LDR) of stratocumulus(commonly –11 to –14 dBZ; decreases with increasing turbulence).(4) After distinguishing of cloud droplets from drizzle, cloud liquid water content and particle effective radius are retrieved. The liquid water content of drizzle is lower than that of cloud droplets at the same radar reflectivity factor.  相似文献   

制备条件对聚乙烯醇-壳聚糖凝胶性能的影响   总被引：1，自引：0，他引：1  

温燕梅  李思东  钟杰平  章超桦  梁泽萍 《广东海洋大学学报》2007,27(4):74-77

以戊二醛为交联剂,由聚乙烯醇(PVA)和壳聚糖(CTS)混合交联得到一种水凝胶,考察了聚乙烯醇和壳聚糖的配比、交联剂用量和反应时间对聚乙烯醇/壳聚糖凝胶吸水率的影响。通过单因素实验,得出了聚乙烯醇/壳聚糖凝胶具有最佳溶胀性能时的条件:聚乙烯醇与壳聚糖的摩尔比为6∶1,交联剂戊二醛的体积分数为0.05%,反应时间9h。测定了该凝胶在不同pH值下的吸水率和吸附铜离子的性能,得出聚乙烯醇/壳聚糖凝胶在酸性介质的吸水率远远大于碱性介质,对铜离子(Cu2+)的吸附量比壳聚糖凝胶提高了33.7%,因此该凝胶吸附剂在工业废水处理重金属离子方面具有一定的优越性。  相似文献   

First discovery of cryptotephra in Holocene peat deposits of Estonia, eastern Baltic     

TIIT HANG  STEFAN WASTEGÅRD  SIIM VESKI  ATKO HEINSALU 《Boreas: An International Journal of Quaternary Research》2006,35(4):644-649

This article reports the first discovery of middle Holocene cryptotephra from a peat sequence in Estonia, eastern Baltic. Two sequences, Mustjärve and Parika (located 110 km apart), were chosen for a pilot study aimed at finding traces of tephra fallout during the middle Holocene. Peat accumulation at both sites started in the early Holocene (c. 9500–9000 ¹⁴C yr BP; c . 11 000–10000 cal. yr BP) and continued throughout the whole Holocene. The radiocarbon-dated intervals between c. 2000 and 5000 ¹⁴C yr BP (c. 2000–5500 cal. yr BP) were chosen from both sites for the study. Colourless tephra shards were identified at 312–316 cm below the peat surface in the Mustjärve peat sequence, while no tephra was found in peat of the same age at Parika. Electron microprobe analyses suggest a correlation with the initial phase of the Hekla-4 eruption (c. 4260 cal. yr BP), although the age-depth model indicated an age around 4900 cal. yr BP. Small concentrations of colourless to light brown tephra shards at 266–270 cm in the Mustjärve sequence indicate that the Kebister tephra (c. 3750 cal. yr BP) might also be present, but geochemical analyses were not possible. The low concentration and small size of the tephra particles indicate that Estonian bogs are probably on the verge of where tephrochronology is possible in northwestern Europe. Further studies of full Holocene sequences are required in order to discover traces of other ash plumes reaching as far east as the eastern Baltic area.  相似文献   

Correlation of stadial and interstadial events in the south Swedish glacial varves with the GRIP oxygen isotope record     

BERTIL RINGBERG  JONAS BJÖRCK  TIIT HANG 《Boreas: An International Journal of Quaternary Research》2003,32(2):427-435

A number of correlated varve sequences from the local varve chronology in southeastern Sweden have been selected to make a 1040 varve years long mean varve thickness curve. Pollen analyses were carried out over an interval of 373 varve years in the northern part of the study area. The pollen stratigraphical data have been divided into local pollen assemblage zones which have been correlated with the radiocarbon-dated regional pollen assemblage zones. Based on variations in herb and tree pollen content of the analysed varve sequences, it has been possible to identify well-documented lateglacial pollen zones for southern Sweden, i.e. the Bölling interstadial (GI-1e), the Older Dryas cold event (GI-1d) and the early part of the Alleröd interstadial (GI-1c). The event stratigraphy in this study, based on varying varve thicknesses and the composition of the pollen flora in the varves, has been correlated with the oxygen isotope stratigraphy of the GRIP ice-core on Greenland between 13600 and 14400 GRIP ice-core years BP. It is concluded that five decadal warm events and one centennial warm event (15–60 and 100 varve years long, respectively) occur in the clay varve record along with one centennial cold event (150 varve years long), the Older Dryas (GI-1d).  相似文献   

天水地区近50年气温与降水变化特征   总被引：8，自引：1，他引：7  

胡利平  姚延锋  裴古娥  安晶  袁雅萍  杭波 《地理科学进展》2009,28(4)

根据1961-2006年天水7个站每月温度和降水资料,分析了近50a天水温度和降水的突变事实。在此基础上给出了气候变暖前后气温、降水的概率分布,比较了变暖前后时段天水气温、降水空间分布的差异。结果表明:1)20世纪90年代初期天水气温、降水发生了明显突变,进入温度显著增暖和降水偏少时段;2)增暖后天水气温和降水的概率分布发生了明显变化,气温偏冷的概率显著减小,偏暖的概率显著增大;降水偏少的概率明显增多,偏多的概率明显减少;3)气候变暖后天水地区和各气候分区气温上升幅度均较显著;降水距平百分率渭北区下降幅度相对突出。进而,讨论了温度增加和降水减少对该地区农业生产的影响。  相似文献