Comparability of Biogenic VOC Emission Rate Measurements under Laboratory and Ambient Conditions at the Example of Monoterpene Emissions from Scots Pine (Pinus sylvestris)     

M. Komenda  K. Kobel  R. Koppmann  J. Wildt 《Journal of Atmospheric Chemistry》2003,45(1):1-23

Laboratory experiments under controlled environmental conditions are a useful tool to investigate the influence of different environmental parameters on VOC emissions from plants individually. Before using the obtained results to interpret measurements under ambient conditions, it has to be ensured that the laboratory system is suitable for performing emission rate measurements under ambient-like conditions to derive algorithms describing the emissions of volatile organic compounds as a function of physical variables like temperature and light intensity. Here we compare results from monoterpene emission rate measurements with Scots pines (Pinus sylvestris L.) under both ambient environmental conditions using a mobile plant enclosure chamber, and under controlled laboratory conditions in a continuously stirred tank reactor. The different analytical instruments to quantify monoterpene emissions were compared in an intercalibration experiment. Measurements of the mixing ratios of -pinene, -pinene, 3-carene, camphene, and limonene on the order of some hundred parts per trillion differed by less than 20%. The laboratory system has proven capable of providing ambient-like conditions and results of monoterpene emission rate measurements under laboratory conditions could be extrapolated to the natural environment. Monoterpene emission rate measurements with identical specimens of Scots pines conducted within small temporal differences under similar laboratory and outdoor conditions agreed well. Both laboratory and outdoor experiments clearly showed that distinct and constant values neither exist for the standard emission rates nor for the emission pattern of monoterpenes from Scots pine. Temporal variations in the standard emission rates from identical specimens and plant-to-plant variations were on the order of one magnitude.  相似文献   

Biogenic silica accumulation in the sediments of Iron Gate I Reservoir on the Danube River   总被引：2，自引：0，他引：2  

Cristian Teodoru  Aristidis Dimopoulos  Bernhard Wehrli 《Aquatic Sciences - Research Across Boundaries》2006,68(4):469-481

  相似文献   

高纯球形-准球形亚微米晶质SiO2材料的制备与表征     

林金辉  周世一  康秀英 《矿物岩石》2007,27(1):7-10

以天然粉石英为基本原料,通过氢氟酸与盐酸混合酸溶蚀技术和机械强力搅拌处理,制备了高纯球形-准球形亚微米晶质SiO2材料。XRD,SEM表征结果表明,制备的高纯球形亚微米晶质SiO2材料为纯结晶SiO2相,粒子呈球形-准球形,球化-准球化率达80%～90%,粒径一般为300 nm～800 nm;其化学组成为:w(SiO2)99.90%,w(Al2O3)192×10-6,w(Fe2O3)33×10-6,w(Mg)1×10-6,w(Ca)2×10-6,w(Cl-)20×10-6。  相似文献   

Silica fume stabilization of an expansive clay subgrade and the effect of silica fume-stabilised soil cushion on its CBR     

B. R. Phanikumar  Jagapathi Raju m  Ramanjaneya Raju e 《Geomechanics and Geoengineering》2020,15(1):64-77

ABSTRACT

Expansive soil subgrades, which are subjected to dual swell-shrink problem consequent upon absorption and evaporation of water, need to be improved by chemical stabilization or compacted cushion or geosynthetic reinforcement in order that pavements constructed over them are even, stable and safe. This paper presents extensive experimental data on plasticity, free swell index (FSI) and compaction characteristics of a highly swelling expansive clay stabilized with varying silica fume contents. In another series of tests on a laterite soil to be used as a cushion over the expansive clay subgrade, plasticity properties, compaction characteristics and strength characteristics were determined at varied silica fume contents. Further, CBR of the expansive clay subgrade was determined in the laboratory stabilizing it with varied silica fume contents and providing a cushion of 50 mm thickness of silica fume-stabilized lateritic soil. Liquid limit (LL), plasticity index (PI) and free swell index (FSI) of the expansive clay decreased with increasing silica fume contents. The compaction and strength characteristics of both the soils improved with silica fume stabilization. The CBR of the expansive clay provided with silica fume-stabilized cushion improved significantly.  相似文献   

Facile Conversion of Alcohols to Olefins by Tosylation and Subsequent SiO2- promoted β-elimination     

RUAN Xiaohong  SONG Gaopeng  ZHANG Yichun  LI Yingxia 《中国海洋大学学报(英文版)》2007,6(2)

A convenient and effective procedure was developed for the conversion of alcohol to olefin by tosylation and subsequent β-elimination promoted by silica gel in this study. Treatment of the alcohols with p-toluenesulfonyl chloride in pyridine at 0℃ affords tosylates which undergo β-elimination with silica gel in dichloromethane or chloroform at room temperature, yielding olefinswith high productivity.  相似文献   

大亚湾西部海域沉积物中生物硅的含量及其分布特征          下载免费PDF全文

周鹏  李冬梅  李海涛  赵力  赵峰  郑远来  吴梅桂  余汉生 《应用海洋学学报》2019,38(1):109-117

采用2. 0 mol/dm~3Na_2CO_3溶液5h单点化学提取-硅钼蓝连续分光光度分析法分别测定了大亚湾西部海域13个表层沉积物和1个沉积物岩芯中生物硅的含量.表层沉积物和沉积物岩芯中生物硅含量占比分别为0. 69%～2. 02%和1. 24%～2. 05%,平均值分别为1. 42%和1. 60%.结果证实西大亚湾沉积物中生物硅含量水平与我国南海近岸海域基本一致.在210Pbex测年的基础上,通过分析沉积物岩芯中生物硅、有机物、无机碳等多指标,揭示近百年来大亚湾周边环境变化对海洋环境的影响,证实了上世纪80年代以来西大亚湾周边农业、海水养殖业和工业发展等人类活动加剧了该海域生态环境变化,尤其90年代核电站运行对海洋生态变化造成一定的影响.  相似文献   

Morphological observation of Epithemia ocellata (Ehr.) Kütz. (Bacillariophyceae) from China     

FAN Yawen  HU Zhengyu 《中国海洋湖沼学报》2007,(4)

The species of Epithemia ocellata (Ehr.) Kütz. from Northeastern China were observed by scanning electron microscopy (SEM). The studies on silica valve formation in different stages were made. At the early stage, a Y-shaped raphe sternum was found. Areolae were made from virgae and vimines. In immature valves, the canal formation before the raphe fissure is visible. The raphe system, virgae and vimines (areolae) might be the early siliceous elements of the valve during morphogenesis. The formations of virgae and vimines are similar to that of Gephyria media W. Arnott. Rows of silica papillae formed gradually on the face of the valve. After the areolae were covered with silica and form rows of papillae, the outer valve surface could become mature. Details of the internal costae were observed in mature valves.  相似文献   

Micromorphology of solonetzic horizons as related to environmental events in the Caspian Lowland     

М.Lebedeva 《山地科学学报》2009,6(2):132-138

Micromorphology of solonetz species with special attention to natric horizon was studied in microcatenas at the Dzhanybek Research Station （northwestern Caspian Lowland）. The solonetzic （natric） horizon is easily identified, and it occurs at varying depths, which are the criteria for subdividing solonetzes into 4 species, namely, crusty, shallow, medium and deep. In this sequence, the depth of humus-accumulative horizons increases, and the upper boundary of salinity manifestations goes down. The following micromorphological features are assumed as typical for natric horizons： angular blocky microstructures with partially accommodated aggregates having sharp boundaries and narrow plane-like packing voids; b-fabric speckled in the aggregates＇ centers and monostriated at their peripheries merging into stress coatings; very few interpedal voids; organo-clay coatings; humus- enriched infillings; no calcite and gypsum pedofeatures. A complete set of ＂natric＂ features was found only in the crusty solonetz; the shallow solonetz lacks only illuviation coatings, while the medium and deep species have several modifications of fabric elements： blocky aggregates have a rounded shape and are penetrated by biogenic channels favoring their further biogenic reworking; plant residues became more abundant and diverse, and blackened tissues occur; illuviation clay coatings evolved into papules; stress coatings gave birth to striated bfabrics, thus maintaining a high plasma orientation. The thin sections of natric horizons made 50 and 20 years ago were examined to study the influence of environmental changes （increase in precipitation and rise of ground water table） on micropedofeatures. The following processes took place： （i） in the topsoil： humus accumulation and biogenic structurization; （ii） in the natric horizon - re-arrangement of clay coatings into micromass b-fabrics; and （iii） in the lower part of the natric horizon - development of pseudosand fabric, calcite and gypsum formation. The trends revealed are in good agreement with the environmental events.  相似文献   

南海北部陆坡神狐海域晚中新世以来沉积物中生物组分变化及意义   总被引：4，自引：1，他引：3  

陈芳  苏新  周洋  陆红锋  刘广虎  陈炽新  陈超云 《海洋地质与第四纪地质》2009,(2)

对南海北部陆坡神狐海域4口钻孔(BY1、BY2、BY3、BY4)岩心沉积物中微体古生物的研究表明晚中新世以来该区沉积物中硅质和钙质生物组分丰度具有较大时间和空间变化。从时间上看,硅质生物在晚中新世—上新世几乎缺失,中更新世以来约40万年(0～24m)才较多出现,18万年以后繁盛,大于0.15mm粗粒级有孔虫在晚中新世期间丰度很低,而在更新世—上新世丰度很高;空间上的差异表现在不同的钻井岩心中生物丰度变化范围较大。根据硅质生物丰度变化可推测晚中新世—上新世—早更新世时海水表层古生产力极低,而中更新世以来古生产力相对较高。南海北部钙质生物丰度的变化主要受控于陆源物质的输入量,在钻探区可识别2个可能具有不同物质来源的小区块,如BY1、BY2孔晚中新世—上新世陆源物质的输入量高于更新世,BY3和BY4孔更新世陆源物质的输入量高于上新世。2007年本区钻探结果揭示的一个令人惊奇和十分独特的现象,水合物以高达20%～49%饱和度状态分散在细粒沉积物(黏土粉砂)孔隙中,本研究发现这些矿层富含钙质生物组分(钙质超微化石和有孔虫),而硅质组分贫乏。由此初步推测,大量钙质生物组分的存在可能增加了黏土粉砂沉积物的孔隙空间,从而为大...  相似文献   

Si–C interactions during degradation of the diatom Skeletonema marinoi     

Brivaëla Moriceau  Madeleine Goutx  Catherine Guigue  Cindy Lee  Robert Armstrong  Marie Duflos  Christian Tamburini  Bruno Charrire  Olivier Ragueneau 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1381-1395

  相似文献