粒度分析在中国第四纪黄土古气候研究中的应用现状     

刘冬雁  李巍然  彭莎莎  王玲 《中国海洋大学学报(自然科学版)》2010,40(2)

中国黄土是记录第四纪古气候信息的重要载体,作者就第四纪黄土研究中涉及的粒度测量、常用粒度指标、敏感粒度、粒度年龄模型以及粒度指标时间序列周期分析等方面的应用现状作了回顾。前人研究结果表明:不同前处理方法对粒度测量结果有较大影响;传统粒度指标应用广泛;敏感粒度的确定是反演古环境的关键;粒度指标时序谱分析是古气候定量化研究的重要方法之一;粒度年龄模型仍是较可信的建立地层年代序列的方法。  相似文献   

越冬前后海马齿脂肪酸和挥发性有机物组成和变化特征          下载免费PDF全文

毕正浩  杨芳  潘渊博  杨玲  林忠州  罗冬莲  周成旭 《海洋科学》2023,47(12):40-54

海马齿是一种热带和亚热带盐生植物, 既是传统野生菜蔬, 也在海岸带生态修复中发挥重要作用。北移种植海马齿进行生态修复时, 越冬低温的影响是成功与否的首要关注问题, 其机制尚待解明。脂肪酸在生物耐受低温中发挥作用, 挥发性有机物与脂肪酸代谢关系密切。本研究利用海湾环境中生态修复浮床上的海马齿样品, 重点解析北移种植环境下, 海马齿植株不同部位受越冬影响前后的脂肪酸和挥发性有机物的组成、差异及变化特征。结果显示, 海马齿的花、叶、茎和根样本中, 共检出14种脂肪酸, 根中的脂肪酸种类数相对最多; 多不饱和脂肪酸在花和叶中的含量(平均分别为56.46%和60.23%)总体大于茎和根(平均分别为41.56%和44.45%)。茎、叶中共检出86种挥发性有机物, 蘑菇醇为优势种类。越冬后脂肪酸和挥发性有机物种类数量显著降低, 多不饱和脂肪酸比例在冻伤植株中显著升高; 就植株脂质营养指数而言, 耐受越冬低温的植株其脂质营养品质提高。越冬造成海马齿两类化合物发生显著变化, 其中C18脂肪酸代谢响应有重要贡献, C18: 3(n-3)和蘑菇醇分别是脂肪酸与挥发性物质中最为重要的两个代谢产物, 可能与抗冻应激有密切关系。本研究为推广海马齿种植以构建可持续近海生态修复体系提供了参考。  相似文献   

塔里木盆地流体与油气藏   总被引：6，自引：0，他引：6       下载免费PDF全文

顾家裕  范土芝等 《地质论评》2001,47(2):201-206

本文以塔里木盆地为例，通过流体势分析，油田水化学分析，包裹体测温和原油中含氮化合物的丰度及比值研究，确定塔中地区晚海西期油气主要来自东北和西北两个方向，在中段形成塔中4油藏，并通过流体运移方向分析，认为塔中4油藏在喜马拉雅期受淡水冲洗破坏，使油所储量大大减少，轮南地区的油气主要来自南部的满加尔凹陷和两侧的哈拉哈塘凹陷和草湖凹陷，其中草湖凹陷两次供油气，而其他两个凹陷三次供油气，流体运移方向的研究有助于认识油气的分布规律，对确定勘探的有利区带和目标具有重要意义。  相似文献   

A GIS raster technique to optimise contaminated soil removal     

E. E. Hellawell  A. C. Kemp  D. J. Nancarrow 《Engineering Geology》2001,60(1-4):107-116

A geographic information system (GIS) raster technique has been developed and used interactively with remediation designers to evaluate the optimum extent of excavating soil contaminated by chlorinated solvents. The technique and the results of its application are presented. The site was a former chemical storage plant for acids and solvents. Two distinct solvent plumes were detected within the ground using a photo-ionisation detector. The solvents were found to be dissolved in the groundwater and migrating in the general direction of groundwater flow. A remediation strategy was proposed involving the localised excavation of contamination ‘hot spots’ followed by the implementation of a groundwater remediation system. A number of excavation options were discussed and the GIS raster technique was developed to evaluate these options in terms of contaminant removed and excavation cost.

The plumes were initially mapped using a triangular irregular network (TIN). These TIN models were rasterised to produce a regular grid of rectangular cells, each cell having a value relating to the concentration of contaminant at that spatial point. The proposed excavation zones were then overlaid on to the raster models as masks. The relationship between the value of contaminant concentration of cells within the mask (or excavation zone) and the total value of contaminant concentration of cells within the solvent plume was used to determine the efficiency of the excavation.

The excavation options were compared taking into account the percentage of the contaminant plume removed, the excavation area (soil volumes) and related costs. Once the GIS raster technique had been developed, it proved very quick to rerun the analysis for the other excavation zones. The optimum excavation zone, based upon cost and contaminant recovery, was found for the site. The technique helped by targeting the worst area of contamination and provided the client with a cost-benefit analysis of the different remediation options.  相似文献   

两广地区自然硫释放量的研究          下载免费PDF全文

庞燕波  王文兴 《大气科学》1993,17(4):499-505

全球和区域大气环境研究的重要任务之一是查明各种气态物质自然源释放通量,含硫化合物是其中的一种,它在阐明生物圈硫循环和环境酸化中起重要作用.迄今为止,我国尚无有关研究报道.本文参考文献资料和实测数据用类比法进行了我国两广地区自然源硫化物释放量的计算.结果表明,天然源硫化物中主要是来自树木和土壤,释放的硫化物为COS(49％),DMS(32％)和H_2S(14％).两广地区全年自然源硫释放量3325吨(以硫计).  相似文献   

INTERACTIONS BETWEEN AMMONIUM UPTAKE AND NITRATE UPTAKE BY NATURAL PHYTOPLANKTONASSEMBLAGES   总被引：4，自引：0，他引：4  

焦念志 《中国海洋湖沼学报》1993,11(2):97-107

Measurements of ammonium and nitrate uptakes by natural phytoplankton assemblages from Jiaozhou Bay at various combinations of ammonium and nitrate concentrations with 15N trace techniques showed that uptake rate of either nitrogen was influenced by the presence of the other but that the influence of ammonium on nitrate uptake was much greater than, that of nitrate on ammonium uptake. The influence mechanism of ammonium on nitrate uptake manifested as competition at lower concentrations and as inhibition at higher concentrations (ammonium concentration >0.6 umol/L), but no total inhibition appeared within the concentration.range of the experiments (0-10umol/L). The influence of nitrate on ammonium uptake seems to be a result of competition for uptake sites on the cell surface. In view of the in situ nutrient concentration in the given marine . environment, it is believed that both nitrogen sources are utilized by phytoplankton. Nitrate uptake in the presence of ammonium and ammonium uptake in the presen  相似文献   

Size-Resolved Aerosol Characterization for a Polluted Episode at the IfT Research Station Melpitz in Autumn 1997     

A. Plewka  T. Gnauk  E. Brüggemann  C. Neusüss  H. Herrmann 《Journal of Atmospheric Chemistry》2004,48(2):131-156

Inorganic ions, organic carbon (OC), elemental carbon (EC) and a variety of organic single species in airborne particles have been determined at the research station of the Leibniz – Institut für Troposphärenforschung (IfT) in Melpitz (Germany) in autumn 1997.Samples of eight selected measurement events were divided in two groups in order to investigate differences in the chemical composition of particles originating from southwesterly (SW – developed EU countries) or from easterly directions (E – less developed eastern countries). Differences between these two groups were tested statistically by Student's t-test.Five stage cascade impactor samples show nitrate as most abundant in the accumulation mode in the SW group. EC and sulphate show the most abundant mass fractions in the E group. That can be considered as a consequence of domestic coal heating and coal-fired power plant emissions in the region of westerly Poland, northern Czech Republic and easterly Germany. Higher nitrate concentrations in the SW group can be explained by stronger NO _x emissions caused by the leeward plume of the conurbation of Leipzig, as well as by the still higher traffic density in western Germany.The methane sulphonic acid (MSA) mass fraction was higher for SW air masses in accumulation mode particles, probably indicating marine origin. Succinic acid also showed higher mass fractions for the SW group. This could be caused by primary emission in automobile exhaust gases and photochemical formation during transport from SW. Indeed, during SW sampling, solar radiation intensity was higher than during E sampling.The observed differences in the particle composition are an expression of the still existing technology gradient in Europe. Future campaigns could show the development to a joint economy with smaller differences in anthropogenic emissions.  相似文献   

Molecular cloning and mRNA expression of cytochrome P4501A1 and 1A2 in the liver of common minke whales (Balaenoptera acutorostrata)     

Satoko Niimi  Michio X. Watanabe  Eun-Young Kim  Hisato Iwata  Genta Yasunaga  Yoshihiro Fujise  Shinsuke Tanabe 《Marine pollution bulletin》2005,51(8-12):784

This study presents full-length cDNA sequences of CYP1A1 and 1A2, in common minke whale (Balaenoptera acutorostrata) from the North Pacific. Both CYP1A1 and CYP1A2 cDNAs had an open reading frame of 516 amino acid residues, and predicted molecular masses were 58.3 kDa and 58.1 kDa, respectively. The deduced full-length amino acid sequence of CYP1A1 revealed higher identities with those of sheep (86%) and pig (87%), and that of CYP1A2 was most closely related to human (82%) and monkey CYP1A2 (82%) among species from which CYP1A2 has been isolated so far. Differences in certain conserved and functional amino acid residues of CYP1A1 and 1A2 between common minke whale and other mammalian species indicate the possibility of their specific metabolic function. Concentrations of organochlorine compounds (OCs) including PCBs and DDTs analyzed in common minke whale liver showed no significant correlation with hepatic mRNA expression levels of CYP1A1 and CYP1A2, indicating no induction of these enzymes by such OCs.  相似文献   

Persistent organic pollutants in remote freshwater ecosystems   总被引：3，自引：0，他引：3  

Pilar Fernández  Guillem Carrera  Joan O. Grimalt 《Aquatic Sciences - Research Across Boundaries》2005,67(3):263-273

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Secular variation record of the Earth's magnetic field in Italy during the Holocene: constraints for the construction of a master curve     

Luigi Vigliotti 《Geophysical Journal International》2006,165(2):414-429

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