Anwendung einer enzymatischen Methode zur Charakterisierung von Huminstoffen Enzymatic Characterization of Humic Substances     

J. B. Jahnel  U. Schmiedel  G. Abbt-Braun  F. H. Frimmel 《洁净——土壤、空气、水》1993,21(1):43-50

A method is described for the specific hydrolysis of amino acids from humic substances by using the proteolytic enzyme “Pronase E”. The amino acids are analyzed by a fluorescence detector after precolumn derivatization and HPLC-separation. The pattern and the concentration of amino acids after the enzymatic hydrolysis are set up for humic substances of different origin. Due to the results the enzymatic hydrolysis is suitable for the characterization of humic substances with a nitrogen content higher than 3%. As shown in a kinetic study of the hydrolysis of a fulvic acid the influence of humic substances on the enzyme activity increases in case of lower nitrogen content. Due to the specificity of the proteolytic enzyme the operationally defined method is limited as shown by a protein of a known amino acid content. The amino acids leucine, valine, tyrosine and histidine are released to the highest extent. The determined total extent for the hydrolysis of Insulin B is 26.34% and for Casein 38.37%. By comparison of the enzymatic hydrolysis with the classic acid hydrolysis the advantages of the biochemical method are the simple experimental handling and the mild reaction conditions. Amino acids which are very unstable like glutamine and asparagine can only be analyzed by the enzymatic hydrolysis.  相似文献   

Eignung mikrobieller Biotests für gebundene Schadstoffe Suitability of Microbial Bioassays for Bound Contaminants     

J. Gunkel  K. Rnnpagel  W. Ahlf 《洁净——土壤、空气、水》1993,21(4):215-220

Toxicity of soil spiked with water soluble and insoluble contaminants was assessed with bacteria. Three bioassays were used with common soil bacteria. Water soluble fractions from the soils were estimated in microtiterplates via dehydrogenase activity of B. cereus and growth of P. putida. A new method was developed using B. cereus to include effects of soil particles with bound contaminants. As contaminants p-nitrophenol and 2-naphthol were tested in these systems. Results indicated that the concentration of the contaminants in the soil solution is determined by soil properties. Toxicity of water soluble fractions was not only a result of the toxicant's concentration but further modified by soluble components of the soils. It is not possible to assess soil pollution from toxicity of the water soluble fraction in general, because unknown factors of the soluble soil fraction can influence toxicity greatly. The newly developed contact bioassay with B. cereus showed clearly higher toxicity of 2-naphthol estimated in soil suspension than did the comparable test system with the same bacteria using water soluble fractions only. The results stress the importance of including soil particles into bioassay procedures. It was shown that also water insoluble, bound contaminants can act as toxicants. For an estimation of toxicity under conditions more relevant for the environment, the suggested test system can provide useful information to bioavailability of bound contaminants.  相似文献   

Adsorption und Hydrolyse von Methylparathion an Aktivkohle und Adsorberharz Adsorption and Hydrolysis of Methyl Parathion (MPT) on Activated Carbon and Adsorption Resin     

P. Spitzer  I. Gosse  K. H. Radeke 《洁净——土壤、空气、水》1993,21(5):267-272

Investigating adsorption of methyl parathion on the activated carbons Filtrasorb 400 and F 44 and on the adsorption polymer Wofatit Y 77 we found a stronger adsorption on the carbons at smaller concentration whereas the resin has the larger capacity at higher concentration. Adsorbents were regenerated through hydrolysis of the pesticide at pH = 11.7. The velocity of hydrolysis in the adsorbed state is reduced to a tenth of that in solution. However, a transport resistance in the pores of adsorbents seems to be negligible as may be concluded from the very small measured particle diameter dependence of the velocity constants. In adsorption-regeneration measurements the capacity of the adsorbents stabilized at about 70% of that of the fresh adsorbents.  相似文献   

Gas and Particulate Products Distribution from the Photooxidation of α-Humulene in the Presence of NOx, Natural Atmospheric Air and Sunlight     

M. Jaoui  R. M. Kamens 《Journal of Atmospheric Chemistry》2003,46(1):29-54

The photooxidation of -humulene in the presence of NO_x, natural sunlight, and rural background air was investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). Identification and quantification of gas and particulate reaction products were reported over the course of the reaction. The daytime photooxidation was carried out in a large outdoor smog chamber (190 m³). A wide range of ring retaining and ring opening products in the gas and particle phase are reported. On average, measured gas and particle phase products accounted for 44% of the reacted -humulene carbon. Measurements show that a number of reaction products with low vapor pressures (e.g. 3-seco--humulone aldehyde, 7-seco--humulone aldehyde, -humulal aldehyde, -humulene 3-oxide or -humulene 7-oxide, -humulaic/alic acid isomers, and 3-seco--14-hydroxyhumulone aldehyde) were found in the early stage of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.  相似文献   

农田生态系统温室气体排放研究进展   总被引：39，自引：0，他引：39  

李晶  王明星  王跃思  黄耀  郑循华  徐新 《大气科学》2003,27(4):740-749

自1985年起,中国科学院大气物理研究所利用自行设计制造的自动观测仪器系统,历时十六年先后对我国四大类主要水稻产区的甲烷排放规律及其与土壤、气象条件和农业管理措施的关系进行了系统野外观测实验,并对稻田甲烷产生、转化和输送机理进行了理论研究,探讨了控制稻田甲烷排放的实用措施,建立了估算和预测稻田甲烷排放的数值模型.在甲烷排放的时空变化规律和转化率研究方面有一系列新的发现,在稻田甲烷产生率、排放率及其与环境条件的关系方面取得一系列新的成果,以充分证据改变了国际上关于全球和中国稻田甲烷排放总量的估算.在对稻田甲  相似文献   

Köppen Climate Types in Observed and Simulated Climates     

Kalvová  Jaroslava  Halenka  Tomáš  Bezpalcová  Klára  Nemešová  Ivana 《Studia Geophysica et Geodaetica》2003,47(1):185-202

The Köppen climate classification was applied to the observed gridded climatological sets and the outputs of four general circulation models (GCMs) over the continents of the Earth. All data had been acquired via the Data Distribution Centre established by the Intergovernmental Panel on Climate Change. The ability of the GCMs to simulate the Köppen climate zones identified in the real data was explored and possible future (global warming) changes in the climate types' distribution for each GCM were assessed. Differences in the area distributions derived from the GCMs' recent climate simulations give evidence about uncertainties generally involved in climate models. As to the global warming simulations, all GCM projections of warming climate (horizon 2050) show that the zones representing tropical rain climates and dry climates become larger, and the zones identified with boreal forest and snow climates together with the polar climates are smaller.  相似文献   

低质量X射线双星的毫秒级准周期信号——最近的进展     

YU Wen-fei 《天文研究与技术》2003,(1):12-15

最近对低质量X射线双星中的千赫兹准周期振动的研究表明 ,是辐射压力 ,而不是盘和磁球的相互作用以及处于盘内边界的广义相对论效应在短时标的盘切断机制上起作用。本文给出了一些研究结果及讨论。  相似文献   

Fluxes of CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O from alpine grassland in the Tibetan Plateau   总被引：1，自引：0，他引：1  

PEIZhiyong OUYANGHua ZHOUCaiping XUXingliang 《地理学报(英文版)》2003,13(1):27-34

Using static chamber technique,fluxes of CO2,CH4 and N2O were measured in the alpine grassland area from July 2000 to July 2001,determinations of mean fluxes showed that CO2 and N2O were generally released from the soil,while the alpine grassland accounted for a weak CH4 sink.Fluxes of CO2,CH4 and N2O ranged widely.The highest CO2 emission occurred in August,whereas almost 90?of the whole year emission occurred in the growing season.But the variations of CH4 and N2O fluxes did not show any clear patterns over the one-year-experiment.During a daily variation,the maximum CO2 emission occurred at 16:00,and then decreased to the minimum emission in the early morning.Daily pattern analyses indicated that the variation in CO2 fluxes was positively related to air temperatures(R^2=0.73)and soil temperatures at a depth of 5 cm(R^2=0.86),whereas daily variations in CH4 and N2O fluxes were poorly explained by soil temperatures and climatic variables.CO2 emissions in this area were much lower than other grasslands in plain areas.  相似文献   

The Non-Linear Stability of L4 in the Restricted Three-Body Problem when the Bigger Primary is a Triaxial Rigid Body     

P. P. Hallan  Sanjay Jain  K. B. Bhatnagar 《Celestial Mechanics and Dynamical Astronomy》2000,77(3):157-184

The non-linear stability of L ₄ in the restricted three-body problem has been studied when the bigger primary is a triaxial rigid body with its equatorial plane coincident with the plane of motion. It is found that L ₄ is stable in the range of linear stability except for three mass ratios:where A₁, A₂ depend upon the lengths of the semi axes of the triaxial rigid body. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

EH-4电导率成像系统的特点及其在金属矿勘探中的应用   总被引：10，自引：0，他引：10  

孟贵祥  兰险 《矿床地质》2006,25(1):36-42

EH-4电导率成像系统是一种混场源频率域电磁观测系统,具有轻便、高效、勘探深度大、分辨率高的特点。通过在块状硫化物铜矿、斑岩铜矿已知矿区的试验研究,证实EH-4系统在这两种矿床类型的隐伏-半隐伏金属矿勘探中有较好的找矿效果。  相似文献