Preparation of Four Chromium Ore Reference Materials     

Zhizhong Cheng  Hongku Huang  Mei Liu  Tiexin Gu  Weidong Yan  Mingcai Yan 《Geostandards and Geoanalytical Research》2013,37(1):95-101

The preparation and characterisation of four chromium ore reference materials are described in this paper. The sample material for GCr‐1, GCr‐3 and GCr‐4 was collected from chromite deposits in Tibet, Qinghai province and Inner Mongolia. GCr‐2 is a composite sample from GCr‐1 and GCr‐4. Sample homogeneity was tested by WD‐XRF and the relative standard deviations were < 1.0%. An F‐test showed that all four materials were homogeneous. Thirteen laboratories involved in the inter‐laboratory programme provided 672 determinations (eighteen oxides and elements). Sixteen components were characterised as certified values, of which Cr₂O₃ ranged from 17.59 to 57.80% m/m. The contents of FeO and CO₂ were taken as reference values.  相似文献   

Changes of land cover in the Yarlung Tsangpo River basin from 1985 to 2005   总被引：1，自引：0，他引：1  

Fapeng Li  Zongxue Xu  Youcan Feng  Mei Liu  Wenfeng Liu 《Environmental Earth Sciences》2013,68(1):181-188

Land cover is closely related to environmental changes and socioeconomic development. Land-cover change in the Tibetan Plateau (TP) is different from that in the lowlands; however, a detailed land-cover change in areas such as the Yarlung Tsangpo River (YTR) basin in the TP has not been reported. To fill this gap, the current study explores the land-cover change between 1985 and 2005 in the YTR basin. The results show that only 1 % of the land cover in the YTR basin changed during this time period. The most significant land-cover changes included increases in forest and built-up areas as well as decreases in grassland, water and wetland areas. By percentage, the most rapid land-cover change occurred for built-up areas with an annual variation of 2.07 %. There was an obvious vertical distribution pattern for land-cover types in the YTR basin; from low to high, the average altitudes were forest, farmland, built-up, grassland, water and wetland, and bare land. The average altitude and slope for most land-cover types did not vary over the past 20 years. However, the average altitude and slope of built-up significantly decreased, especially in the zone between 3,500 and 4,000 m. The water and wetland area in altitudes above 4,500 m increased; however, they decreased in the zone between 3,500 and 4,000 m. Natural factors cause most land-cover changes, whereas the increasing intensity of human activities cause some changes to built-up and farmland. Additional attention should be paid to the study of the mechanism of land-cover change in the TP.  相似文献   

Shrubs proliferated within a six-year exclosure in a temperate grassland—Spatiotemporal relationships between vegetation and soil variables   总被引：1，自引：0，他引：1  

Yong Zhang  Qiong Gao  Li Xu  Mei Yu  YuQiang Tian 《寒旱区科学》2014,6(2):0139-0149

Overgrazing has been considered one of the maj or causes that trigger shrub encroachment of grassland. Proliferation of shrubs in grassland is recognized as an important indicator of grassland degradation and desertification. In China, various conservation measures, including enclosures to reduce livestock grazing, have been taken to reverse the trend of grassland desertification, yet shrubs have been reported to increase in the grasslands over the past decades. In late 2007, we set up a 400-m-by-50-m exclosure in a long-term overgrazed temperate grassland in Inner Mongolia, with the ob- jective to quantify the spatiotemporal relationship between vegetation dynamics, soil variables, and grazing exclusion. Soil moisture was continuously monitored within the exclosure, and cover and aboveground biomass of the shrubs were measured inside the exclosure in 2007, 2009, 2010, 2012, and 2013, and outside the exclosure in 2012 and 2013. We found the average shrub cover and biomass significantly increased in the six years by 103 % and 120%, respectively. The result supported the hypothesis that releasing grazing pressure following long-term overgrazing tends to trigger shrub invasion into grassland. Our results, limited to a single gradient, suggest that any conservation measures with quick release of overgrazing pressure by enclosure or other similar means might do just the opposite to accelerate shrub en- croachment in grassland. The changes in vegetation cover and biomass were regressed on the temporal average of the soil moisture content by means of the generalized least square technique to quantify the effect of the spatial autocor- relation. The result indicates that the grass cover and biomass significantly increased with the top, but decreased with the bottom layer soil moisture. The shrub cover and biomass, on the other hand, decreased with the top, but increased with bottom soil moisture, although the regression coefficients for the shrubs were not statistically significant. Hence this study supports the two-layered soil model which assumes grasses and shrubs use belowground resources in dif- ferent depths.  相似文献   

2010-2011年长江河口及邻近水域春夏季仔稚鱼群落结构及其多样性的研究   总被引：2，自引：2，他引：0  

蒋玫  李磊  沈新强  全为民 《海洋学报》2014,36(6):131-137

根据2010—2011年春夏季对长江河口及邻近水域进行了仔稚鱼生态调查,应用单元和多元统计方法分析了春夏季长江河口及邻近水域仔稚鱼群落结构。4个航次调查共获得27个种类的仔稚鱼,隶属5目14科。优势种类主要包括鳀Engraulis japonicus、凤鲚Coilia mystus、康氏小公鱼Stolephorus commersonii、鮻Liza haematocheila、黄姑鱼Nibea albiflora、黄鳍刺虎鱼Acanthogobius flavimanus和寡鳞飘鱼Pseudolaubuca engraulis等。Shannon-Weaver指数(H′)在调查周期内的波动幅度较大,且2011年明显低于2010年。仔稚鱼群落结构和多样性指数春季年间较夏季年间差异性显著。调查区夏季群落结构年间相似性不高,春季群落结构格局年际变化则较明显。聚类分析表明,春夏季长江河口近岸水域仔稚鱼群落可划分为2个站位组,分别对应于长江河口淡水水域和长江口咸水水域。淡水水域组群落和咸水水域组群落总丰度与盐度相关性较高。表明盐度可能是造成长江河口仔稚鱼群落结构时空差异性的主要原因。  相似文献   

连续降温对大菱鲆成鱼代谢机能的影响     

纪利芹  蒋克勇  韩龙江  袁坤山  邱楚雯  王宝杰  刘梅  王雷  温海深 《海洋科学》2014,(9)

为了探寻连续降温对大菱鲆成鱼血清、肝脏及肌肉能量代谢等指标的影响,将大菱鲆从正常养殖水温18℃快速连续降温至1℃,并在18℃、13℃、8℃、5℃、3℃和1℃共计6个温度点取血采样,分别测定血清中的总蛋白(TP)、白蛋白(ALB)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、甘油三酯(TG)、总胆固醇(TC)、总胆红素(TBIL)、血糖(GLU)以及肝脏中的糖原和肌肉中的乳酸等指标,实验数据采用SPSS 17.0统计软件进行单因素方差分析。结果发现,随着温度降低,大菱鲆的血清TP浓度呈先下降后升高的趋势,且在13℃和3℃时出现显著性差异(P<0.05);血清ALB浓度则呈现升高趋势,在3℃时显著高于1℃(P<0.05);血清TC浓度呈现升高趋势,且3℃时显著高于18℃(P<0.05); GLU浓度呈先降低后升高趋势,且8℃时显著高于13℃(P<0.05);尿素浓度呈先降低后升高再降低趋势,且8℃时显著高于1℃(P<0.05);肝糖原浓度在各温度之间无显著差异(P>0.05);肌肉中乳酸含量呈先升高后降低趋势,且5℃时显著高于18℃(P<0.05);其余指标则无显著性差异(P>0.05)。结果表明：当温度在18℃～8℃时,降温对大菱鲆体内代谢影响不大;当温度降到8℃～3℃时,大菱鲆体内开始出现应激反应;当温度继续降低至1℃时,大菱鲆体内的各种代谢基本处于停滞状态。  相似文献   

Characterization of calcium deposition induced by Synechocystis sp. PCC6803 in BG11 culture medium   总被引：1，自引：0，他引：1  

闫华晓  韩作振  赵辉  周仕学  迟乃杰  韩梅  寇小燕  张艳  徐琳琳  田晨晨  秦松 《中国海洋湖沼学报》2014,32(3):503-510

Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate deposition were investigated. Inoculated BGll in different calcium ion concentrations was used for the experimental group, while the BGll culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium （Ca）, carbon （C）, oxygen （O）, phosphorus （P）, iron （Fe）, copper （Cu）, zinc （Zn）, and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BGll culture media. There may be more calcium- containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.  相似文献   

High resolution records of flood deposition in the mud area off the Changjiang River mouth during the past century     

胡刚  李安春  刘健  徐刚  梅西  孔祥淮 《中国海洋湖沼学报》2014,32(4):909-920

This paper presents a paleoflood study to determine the flood frequency of the Changjiang River, based on core cj0702, taken from the Changjiang River subaqueous delta. We identified flood deposits by means of high-resolution grain-size variation, sensitive population, geochemical indexes and magnetic susceptibility. The core covers a time span of 120 years by 210 Pb dating and was sampled at 1–2 cm intervals. Grain size, geochemical elements, and physical parameters were analyzed. The results indicate that the sediment of the core is mainly composed of silt and clay, as well as groups of interbedded silt, clay silt, and clay. Vertically, the grain size pattern was controlled by seasonal variations in water discharge and by the sediment input in winter from the abandoned Huanghe River delta. River flooding caused extreme values in all our measured parameters. We identified more than 20 flood events that occurred since 1887 using the physical parameter analysis method. The environmentally sensitive component of sediment grain size(14.32–96.39 μm) contribution30%, Zr/Rb ratio1.5, and magnetic susceptibility16 were selected as the criteria for flood identification generally. We also found that floods that had taken place in the upstream, midstream, or downstream parts of the river were clearly identified by these indexes while the large-scale floods that covered the whole drainage area did not leave clear indications in the sediment record. This study for identification of flood events is of great significance for understanding hyperpycnal current sedimentation as well as for forecasting of floods.  相似文献   

自动气象站草面温度、地面温度异常记录处理分析     

张梅  秦莉  李元华 《内蒙古气象》2014,(3):44-46

针对自动气象站在数据采集过程中,由于受仪器故障、维护不当或自动站仪器校准漂移等因素的影响,容易造成草面温度、地面温度数据的异常,文章根据具体实例分析了各种异常记录出现的原因,提出相关处理方法,以保证数据序列完整、准确。  相似文献   

西太平洋副热带高压季节内异常活动与亚洲夏季风系统的时延相关特征   总被引：1，自引：0，他引：1       下载免费PDF全文

洪梅  张韧  张海洋  马晨晨  葛晶晶  赵靓  余丹丹 《大气科学学报》2014,37(6):705-714

基于西太平洋副热带高压的异常活动与亚洲夏季风系统其他成员之间存在着密切联系的天气事实,运用交叉小波的非线性时滞相关分析方法,对东亚夏季风系统成员与西太平洋副热带高压形态和变异的相互影响的基本事实和物理特征进行研究,得到了西太平洋副热带高压与主要的亚洲夏季风系统成员之间基本的关联结构和演变示意图。研究结果揭示了不同的季风子系统对西太平洋副热带高压的影响不同:影响西太平洋副热带高压强度和脊线位置异常变化的是亚洲夏季风系统中的印度夏季风子系统的5个主要成员;而影响西太平洋副热带高压西脊点异常变化的则是亚洲夏季风系统中的另一个子系统——东亚夏季风子系统的5个主要成员。研究揭示了副热带高压与亚洲夏季风系统主要成员之间的时延特征与统计关联特性,为相应的机理研究提供了事实依据。  相似文献   

一种建筑信息模型与三维数字城市集成方法     

薛梅 《地理信息世界》2014,(5)

BIM的发展为数字城市三维模型提供了更加精确的数据来源,现有研究主要关注BIM空间实体模型向三维表面模型转换,缺少建筑语义信息映射及整体集成方案研究。本文以构成建筑骨架的主要空间构件为研究对象,在参考IFC标准基础上,结合数字城市应用特点设计了具有空间语义一致性的建筑构件信息模型BCM,在此基础上提出建筑信息模型和三维数字城市集成方案。首先,基于CAD图纸开展BIM模型交互式构建,然后,通过空间和语义信息映射将其转换为BCM,并基于ArcGIS Geodatabase建立建筑构件信息库,在三维数字城市场景开展建筑构件信息的集成应用。该方案可实现建筑构件信息与三维数字城市的大规模集成,对推动数字城市向智慧城市发展,进一步开展建筑内外模型集成展示、建筑节能分析、内部设施管理等具有重要价值。  相似文献