古尔班通古特沙漠生物结皮小尺度分异的环境特征   总被引：12，自引：5，他引：7  

王雪芹  张元明  王远超  万金平  徐曼 《中国沙漠》2006,26(5):711-716

古尔班通古特沙漠广泛存在的生物结皮,对地貌部位有极强的选择性分布,其实质是生物对环境条件综合适应的一种生态表现。2002年3~11月在个体沙丘表面初步开展了生物结皮类型小尺度环境分异规律研究。结果表明:苔藓结皮、地衣结皮和藻类结皮依次分布于垄间、沙垄两坡中部和坡上部,从垄间往垄顶,生物结皮盖度逐渐减小,厚度变薄,抗压性减弱。苔藓结皮分布区的物质组成以细沙和极细沙为主,春季表层土壤水分在5%以上,短命植物广泛发育,基质稳定;坡中部的地衣结皮分布区以细沙为主,春季表层土壤水分在4%左右,短命植物亦有广泛分布,地表受风沙活动影响较小;沙垄上部和顶部的藻类结皮分布区,是沙垄表面活动性最强和土壤水分最差的区域,物质组成以中沙为主,高等植物中白梭梭为优势种,可见藻结皮是三类结皮中最能适应恶劣环境的生物结皮类型。  相似文献   

自然水体采集的生物膜上铁、锰氧化物的萃取分离   总被引：1，自引：0，他引：1  

赵兴敏  花修艺  张菁菁  董德明  李鱼 《吉林大学学报(地球科学版)》2005,35(4):505-509

采用选择性萃取分离技术对自然水体采集的生物膜上铁、锰氧化物进行萃取分离研究,考察该技术的适用性。参考人工培养生物膜的萃取方法,分别用NH₂OH·HCl和Na₂S₂O₄为萃取剂选择性萃取生物膜上的锰氧化物和铁、锰氧化物。实验中分别依次只改变萃取剂浓度、萃取液酸度或萃取时间,保持其它两个因素不变,分别考察这三个因素对萃取效果的影响,从中选出对铁、锰氧化物萃取率高而对有机质影响小的条件为最佳条件。用选定的最佳条件对不同时间和地点采集的生物膜进行萃取,发现对目的组分的萃取率可达70.8%~94.6%,而对非目的组分的影响很小（3.3%~11.0%）,满足萃取分离的要求。这说明选择性萃取技术可以广泛应用于自然水体采集的生物膜上铁、锰氧化物的萃取分离。  相似文献   

敦煌某地铁矿中磁性铁的化学物相分析          下载免费PDF全文

郭建斌  蔡敏 《甘肃地质》2015,24(4):80-83

本文选用HAC—H_2O_2和HCl—NaHCO_3作为选择性溶剂,对敦煌某地铁矿中磁性铁的化学物相分析进行了研究,将磁性铁物相从传统1项细化为3项,测定了磁性铁相态中磁黄铁矿、假象赤铁矿、磁铁中铁的含量。使用国家标准物质GBW07272对方法进行了评价,分析结果与标准值或参考值吻合良好(RE为0.28%~4.75%,RSD为0.13%~5.59%)。方法简单、准确。  相似文献   

盐酸及乙酸介质中的碳酸盐岩溶蚀表面特征及机理——以南堡凹陷为例   总被引：1，自引：0，他引：1  

朱文慧  曲希玉  邱隆伟  陈勇  龚发雄  吴思萱 《矿物岩石地球化学通报》2015,(3)

为了研究酸性条件下碳酸盐岩的溶蚀表面特征及机理,以南堡凹陷及周边凸起区10个典型碳酸盐岩样品为研究对象,进行乙酸和盐酸溶液的溶解实验,并通过扫描电镜观察样品的溶蚀特征。结果显示,岩石结构和矿物成分的选择性溶蚀,是碳酸盐岩溶蚀过程中的主要作用形式;方解石和白云石均存在特有的溶蚀现象,即"溶蚀晶锥"方解石和"蜂窝状"白云石,为晶体选择性溶蚀的产物;表生条件下,灰岩中少量白云石的加入能够增加方解石的溶解度,白云石的含量上限为13%,超过该界限,随白云石含量的增加,溶蚀作用减弱。  相似文献   

Effect of Cu toxicity at different salinity on selective group of juvenile pompano Trachinotus ovatus          下载免费PDF全文

OU You-jun  LI Jia-er  CAI Wen-chao 《热带海洋学报》2014,33(4):26-32

Effects of copper toxicity and salinity shock on selective group of juvenile pompano Trachinotus ovatus were investigated.The fish were exposed to different Cu2+ concentrations of 0(blank),0.02(C1),0.05(C2),0.10(C3),and 0.15 mg·L–1(C4)at a salinity of 10‰ or 40‰ for 96 h,with the salinity of 29‰ as the control.The results showed that the effects of the acute salinity stimulation to survival rates of pompano between control(29‰)and lower or higher salinity for 96 h were not significant(p0.05).However,the survival rates in each treatment were decreased with the increase of Cu2+ concentration.The dominant factor influencing body moisture of the fish was salinity,and there was no sign that body moisture was correlated with exposure to Cu2+.The gill lamellas in high level of Cu2+ concentration(C4 treatments)were abnormal under the salinity of 40‰ and extremely curly under the salinity of 10‰.Hemorrhage in gill was observed in the two C4 treatments.Under transmission electron microscope,pillar cells in gill lamellas appeared deformed and ruptured in some areas of the epithelia in the higher concentration of Cu2+,resulting in the death of the fish due to the destruction of gill tissue,elevation of the arithmetic mean distance from water to blood,the decrease of oxygen diffusion capacity,and other physiological functions.These findings indicate that the pompano might suffer much more pressure when encountered with Cu2+ pollution and low salinity.  相似文献   

CBERS-02B多光谱数据在城市不透水面 估算中的可用性研究   总被引：2，自引：0，他引：2  

陈峰  邱全毅  郭青海  唐立娜 《遥感学报》2011,15(3):621-639

以厦门岛为研究区,以CBERS-02B的CCD影像为数据源,采用基于可变端元的线性光谱混合模型估算了城市不 透水面组分含量,并探讨了该方法的实现过程与优势。通过端元评估确定了研究区的４个典型端元,即高反射不透水 面、低反射不透水面、高反射土壤和植被。在此基础上,以高、低反射不透水面端元的组分含量对城市不透水面含量 进行估算。精度评价结果显示：基于可变端元的方法要优于一般带全约束法;而在混合像元分解过程中加入全色波段 （band5）有助于提高模型估算精度,使得在像元尺度的精度与采用Landsat的已有报道相近,而在土地利用单元尺度实 现了对城市不透水面的无偏估计。研究实例也表明,尽管目前CBERS-02B数据在辐射定标和地理定位等方面还有待改 进,通过采用适当的处理过程和技术手段,依然能利用该数据对城市不透水面进行有效估算。  相似文献   

Vertical mixing of gravel over a long flood series     

Judith K. Haschenburger 《地球表面变化过程与地形》2011,36(8):1044-1058

Vertical sediment exchange is a fundamental component of bedload transport in gravel‐bed channels. This paper describes the characteristic depth of exchange achieved over a long flood series. Analysis is based on 11 recoveries of magnetically tagged gravels deployed in Carnation Creek, Canada, completed between 1990 and 2008. Vertical grain exchange mixes gravels throughout the streambed relatively rapidly. Within one to eight floods the mean burial depth approaches two times the surface layer thickness, quantified by the 90th percentile of the size distribution. Finer gravels are mixed more rapidly into the bed than coarser gravels. Both active and passive grain exchanges throughout most of the bed produce the overall vertical distribution of marked grains. Gravel exchanges exhibit fairly consistent patterns once tracers are well mixed by large floods. Results highlight the role of flood sequence in determining exchange depths, support the notion of an upper limit to exchange, and underscore the importance of passive grain exchange. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Effects of residual chlorine on the mortality, grazing and respiration of Labidocera euchaeta (Copepoda)     

MA Zengling  LIN Hongping  GU Xiaolian  XU Zhaoli 《海洋学报(英文版)》2011,30(2):96-102

In this study,the authors investigated the effects of residual chlorine on mortality,grazing and respiration of Labidocera euchaeta in laboratory.The grazing rate was evaluated by subtraction method of food concentration and respiration rate was measured using oxygen electrode.It was found that the lethal effect of residual chlorine on L.euchaeta increased with enhanced concentration and prolonged duration.The medium lethal concentration (LC 50 ) of chlorine for L.euchaeta in 24 h was about 0.58 mg/L and the safe concentration was about 0.21 mg/L.However,the grazing and respiration of L.euchaeta decreased by 32.6% and 18.9% when exposed to 0.2 mg/L residual chlorine for 4 h.It indicated that the physiological activities of zooplankton could be suppressed by the residual chlorine less than the safety concentration.Therefore,both survival and physiological activities of the organisms living in the thermal (nuclear) power plant discharging waters should be considered when carrying out the ecological risks assessment.  相似文献   

Differences in top-down and bottom-up regulation of macroalgal communities between a reef crest and back reef habitat in Zanzibar     

Gustaf Lillieskld Sj  Erik Mrk  Simon Andersson  Inger Melander 《Estuarine, Coastal and Shelf Science》2011,91(4):331

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PATTERNS OF VEGETATION CHANGE ON ALPINE MOUNTAIN SUMMER FARMS IN NORWAY     

KERSTIN POTTHOFF  VERA STROTH 《Geografiska Annaler: Series A, Physical Geography》2011,93(3):163-174

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