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1.
土壤腐殖质各组分红外光谱研究   总被引:14,自引:0,他引:14  
肖彦春  窦森 《分析化学》2007,35(11):1596-1600
土壤腐殖质是土壤中所特有的一类特殊的高分子化合物,具有重要的肥力和环境调节功能。其中胡敏素的提取和纯化很困难,从而限制了对其性质和结构的研究。为揭示胡敏素的结构性质,本研究按Pallo分组,将胡敏酸(HA)分为焦磷酸钠提取的胡敏酸(HAP)、氢氧化钠提取的胡敏酸(HAS);富里酸(FA)分为焦磷酸钠提取的富里酸(FAP)和氢氧化钠提取的富里酸(FAS);胡敏素(HM)分为铁结合胡敏素(HMi)、粘粒结合胡敏素(HMc)和不溶性胡敏素(HMr)三个组分,采用红外光谱法对黑土、草甸土以及黑土底土加入大量玉米秸秆培养后腐殖质各组分的结构特征进行研究。腐殖质各组分按Pallo法分组。结果表明:铁结合胡敏素(HMi)、粘粒结合胡敏素(HMc)与胡敏酸(HA)、富里酸(FA)具有相似的光谱特征,但存在明显差异。黑土、草甸土中HMi和HMc的脂族性强于HA和FA;HMi与HMc相比,HMi具有较高的脂族性。黑土中氢氧化钠提取的胡敏酸(HAS)的脂族性强于焦磷酸钠提取的胡敏酸(HAP);NaOH提取的富里酸(FAS)的脂族性强于Na4P2O7提取的富里酸(FAP)。草甸土中HAP的脂族结构较多,而HAS脂族结构相对较少。在培养土中,新形成的FA脂族性强于HA、HMi和HMc组分。新形成的HMc脂族性强于HMi和HMc的脂族性强于HAP,而弱于HAS。  相似文献   

2.
超铀元素的存在界限就是元素周期系的界限,这是一个基础理论研究课题。实验事实表明,冷熔合反应是合成超铀重元素的最成功的方法,但此法受到超重元素核生成截面的限制;超铀元素是不稳定的,它的存在受到几种放射性衰变的限制.现在已经合成的最重元素是109号元素,超铀元素的存在界限不会比Z=109大许多,大体在Z=110—125范围之内。  相似文献   

3.
铅和富里酸化学形态模拟计算方法的比较   总被引:3,自引:0,他引:3  
刘嘉  邓勃 《分析化学》1997,25(5):543-547
在阳极溶出伏安法获限Pb和富里酸的溶出电流和电位偏移数值的基础上采用一种新的全局优化方法-遗传算法模拟计算了水体中铅和富里酸的化学形态,对3种计算络合常数的方法进行了比较,误差分析的结果表明:对所研究的体系,电流迭代-遗传算法比电位偏移-遗传算法获得的结果更可靠。  相似文献   

4.
罗磊  吕继涛  许闯  郭智  张淑贞 《分析化学》2013,41(8):1279-1282
应用同步辐射近边X射线吸收精细结构(NEXAFS)光谱技术研究了土壤腐殖质各组分(富里酸、胡敏酸及胡敏素等)的含碳官能团组成信息,并通过分析PO43-存在条件下胡敏酸、胡敏素的官能团组成变化特征,探讨了PO43-与土壤腐殖质之间的微观作用机制。结果表明,土壤腐殖质不同组分的官能团分布具有类似的光谱特征,但组成比例存在明显差异。随着腐殖质组分的酸不溶性增加,胡敏酸、胡敏素疏水性脂肪基官能团比例显著高于富里酸,芳构化程度也明显增加,而亲水性羧基官能团比例趋于降低;PO43-通过静电作用、取代反应可以选择性释放胡敏酸中部分小分子羧基官能团,从而改变胡敏酸官能团的组成特征。此研究结果对于应用NEXAFS研究有机碳官能团形态、结构及理解PO43-在土壤微界面上的反应机制具有重要意义。  相似文献   

5.
本文综述了近年来天然水体中腐殖质的光化学研究进展,重点讨论腐殖质以及相关活性氧的光化学反应机理,并分析了影响腐殖质光解的主要因素,最后,针对水体腐殖质光化学研究中面临的问题,提出了今后的重点研究方向.  相似文献   

6.
铀促排化合物的研究进展   总被引:4,自引:0,他引:4  
本文简要介绍了铀中毒的毒理机制和铀促排化合物的解毒机制,综述了自20世纪70年代以来用于铀促排的化合物,并对其中主要的几大类,如邻苯二酚类、羟基吡啶酮类、膦酸类等进行了分析,展望了铀促排化合物的发展前景.  相似文献   

7.
天然铀矿中铀常与黄铁矿共生,这两者之间存在着相互作用,而环境中有机物和微生物也会对此共生现象产生一些影响。本文采用循环伏安法(CV)研究了黄铁矿与U(VI)体系中的铀价态的变化及电子转移数,结果表明,黄铁矿可以自发把U(VI)还原到U(V)和U(IV)。腐殖酸(HA)存在时对黄铁矿还原铀有抑制作用,氧化亚铁硫杆菌(TF)存在时则有协同作用。光电子能谱研究表明,黄铁矿中的Fe2+和S-对U(VI)的还原都起了作用。本文从电子、离子等微观角度研究了黄铁矿还原富集铀的反应机理,解释了天然铀矿中铀与黄铁矿共生这一现象,为铀成矿理论提供了新依据,并为黄铁矿在环境污染修复中的应用及周围环境影响程度的大小提供了理论依据。  相似文献   

8.
本文从腐殖酸的结构和存在形式、与锕系金属离子相互作用等两方面简要总结了近年来相关实验和理论研究进展。研究显示,腐殖酸主要通过羧基与锕系离子形成配位复合物,进而影响锕系离子在环境中的迁移。地质环境中的pH、离子强度、矿物表面等都会对腐殖酸与锕系离子的相互作用产生影响,尤以pH的影响最为显著。在较低的pH条件下,腐殖酸的出现一般会促进锕系离子在一些矿物表面的吸附;而在中性或者碱性条件下,则会减弱锕系离子在矿物表面的驻留。腐殖酸对具有氧化活性的锕系离子表现出来的还原性主要来自于还原态的醌式结构单元以及酚羟基。在还原态硫含量较高的腐殖酸中,硫也会参与氧化还原反应。论文还从实验和理论两方面展望了未来腐殖酸与锕系相互作用的研究前景。  相似文献   

9.
采用多接收电感耦合等离子体质谱(ICP-MS)对铝锭及氧化铝中的超微量铀进行了分析测定,采用浓盐酸溶解样品,监测流程空白.未对铝基体进行分离,直接进行分析测定,相对标准偏差小于4%.  相似文献   

10.
玉米秸秆堆腐过程中形成富里酸的结构分析   总被引:4,自引:0,他引:4  
采用傅里叶变换红外光谱及^1H和^13C核磁共振波谱对玉米秸秆堆腐过程中形成的富里酸的结构进行了表征。结果表明,玉米秸秆腐解过程中形成的富里酸包括羧基或羰基基团,芳香结构,烷基片断和碳水化合物结构。  相似文献   

11.
The influence of humic substances on sorption and methylation processes for inorganic- and organotin species is presented. Four sediment samples from different locations of the Rivers Elbe, Mulde and Spittelwasser, Germany, with different organotin and humic contents were selected to extract the humic and fulvic acids. The various fractions—the original sediment, the humic acid, the fulvic acid and the residual sediment—were analysed for their organotin content. The individual buyltin species show quite different distribution patterns. Monobutyltin is found mostly associated with humic acids. Dibutyltin shows a nonunique behaviour. At low total organotin content, dibutyltin is found bonded to humic and fulvic acids, whereas at high organotin content dibutyltin is distributed more with the residual sediment. Most of the tributyltin remains in the sediment unextracted; only small quantities of it are in the fulvic acid fraction. Tetrabutyltin is only in the humic acid fraction when it binds to humic matter; it mostly remains in the sediment. General observations indicate that ionic butyltin species bind to fulvic acids whereas the non-polar tetrabutyltin is not found in the fulvic acid fractions in any of the samples. The appearance of monomethyl- and dimethyl-tin species in the humic and fulvic acid fractions after the alkaline extraction was surprising. There is a correlation between the humic content of the sample and the formation of methyltin species. Evidence is provided by experiments that humic substances act as methylation agents.  相似文献   

12.
Black, brown, and light peat and sapropel were analyzed as natural sources of organic and humic substances. These specific substances are applicable in industry, agriculture, the environment, and biomedicine with well-known and novel approaches. Analysis of the organic compounds fulvic acid, humic acid, and humin in different peat and sapropel extracts from Lithuania was performed in this study. The dominant organic compound was bis(tert-butyldimethylsilyl) carbonate, which varied from 6.90% to 25.68% in peat extracts. The highest mass fraction of malonic acid amide was in the sapropel extract; it varied from 12.44% to 26.84%. Significant amounts of acetohydroxamic, lactic, and glycolic acid derivatives were identified in peat and sapropel extracts. Comparing the two extraction methods, it was concluded that active maceration was more efficient than ultrasound extraction in yielding higher amounts of organic compounds. The highest amounts of fulvic acid (1%) and humic acid and humin (15.3%) were determined in pure brown peat samples. This research on humic substances is useful to characterize the peat of different origins, to develop possible aspects of standardization, and to describe potential of the chemical constituents.  相似文献   

13.
Cyclodextrin-modified graphene oxide nanosheets (denoted as CD/GO) were synthesized by an in-situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and potentiometric acid-base titration. The characterization results indicated that CD was successfully grafted onto GO surfaces by forming a chemical bond. Mutual effects on the simultaneous removal of hexavalent uranium and humic acid by CD/GO from aqueous solution were investigated. The results indicated that U(VI) and humic acid (HA) sorption on CD/GO were greatly affected by pH and ionic strength. The presence of HA enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH, whereas the presence of U(VI) enhanced HA sorption. The surface adsorbed HA acted as a “bridge” between U(VI) and CD/GO, and formed strong inner-sphere surface complexes with U(VI). Sorption isotherms of U(VI) or HA on CD/GO could be well fitted by the Langmuir model. This work highlights that CD/GO can be used as a promising material in the enrichment of U(VI) and HA from wastewater in U(VI) and humic substances obtained by environmental pollution cleanup.  相似文献   

14.
Analytical chemistry of freshwater humic substances   总被引:4,自引:0,他引:4  
Dissolved organic carbon (DOC) in aquatic environments represents one of the largest active organic carbon reservoirs in the biosphere. Current ideologies concerning the sources of DOC, how it is formed and utilized, and what determines the quality of DOC are examined. Humic substances can comprise a significant fraction of the DOC and developments in methods of analysis including the isolation and characterization of this fraction are reviewed.  相似文献   

15.
Aluminum ion (Al3+) in the ‘free’ (aquo) state is becoming increasingly prevalent in environmental waters, especially fresh waters, as a consequence of acid rain and other environmental processes. As Al3+ ion is known to affect markedly a wide range of biological systems, and since the presence of Al3+ in humans has been linked to a number of human diseases, it is important to understand the speciation of Al3+ ion in natural waters. Since some of the most important complexation agents for Al3+ in both fresh and sea waters are members of the complex humic substances group, it is important to understand the manner in which Al3+ interacts with this class of molecules, especially since binding of Al3+ to these molecules can effectively increase the bioavailability of this toxic metal ion to biological systems. The objective of this review is to present the current state of our understanding of aqueous aluminum complexation with the most acidic members (and therefore the most likely candidates for serving as Al3+ complexing agents) of the humic substances group, the fulvic acids. Much of the current knowledge has been revealed by comprehensive fluorescence titration analyses. Some additional information has come from other experimental approaches, including infrared spectroscopy, nuclear magnetic resonance spectroscopy, and a variety of electrochemical approaches. In this review, we also report on the results of our recent fluorescence and IR spectroscopy survey of the interaction of metals from of all three Nieboer and Richardson categories of environmental metals (Class A, Class B and Intermediate Class) with the fulvic acid sub-group of the humic substances. This has proven helpful in understanding some of the unique spectral behaviors of the Al3+-fulvic acid complex vis-a-vis fulvic acid complexes with many other metal ions. The results of our fluorescence and IR experiments with the model compounds, such as salicylic and phthalic acids, have allowed confirmation of the important roles played by both salicylic acid-like sites and phthalic acid-like sites in the unique complexation of Al3+ to humic substances, and help to explain some of the observed spectroscopic changes associated with Al3+ ion complexation to humic material. From the current work, it seems clear that major sources of the deviation in spectral properties between Al3+ and many other metal ions (across all three Nieboer and Richardson categories) are the unusually high value of its charge density and relatively low propensity for involvement in covalent bonding interactions (i.e. a very high ionic index combined with a relatively low covalent index in the Nieboer and Richardson classification of environmental metals), as well as affinity for certain functional groups.  相似文献   

16.
Humic acid was the main compound in soil and reduced the availability of some organic compounds in soils. In this work, humic acid was immobilized for the first time on a homemade neutravidin poly(glycidyl methacrylate-co-ethylene dimethacrylate) capillary column with a 20 μm i.d. for the screening of potential ligands to humic acid and the evaluation of their molecular recognition mechanism. This homemade humic acid column enabling it to work at very low backpressure (0.60 MPa at 20 nl/min flow rate), had a long lifetime, excellent repeatability, and negligible non-specific binding sites. The performance of this affinity humic acid column was demonstrated by the evaluation of recognition assay for a series of known ligands of humic acid (a series of rodenticide molecules) which is the heart of the fragment-based drug design. In addition, this column was used successfully for highlighting the binding mechanism to humic acid of the severe acute respiratory syndrome coronavirus-2-spike protein. As well this new humic acid miniaturized liquid chromatography column developed in this work could be used in the feature for another solute molecule-humic acid binding studies or for a separative mode.  相似文献   

17.
A hydrophilic interaction liquid chromatography (HILIC) method was developed to measure the composition of humic substances from river, reservoir, and treated wastewater based on their physicochemical properties. The current method fractionates the humic substances into four well-defined groups based on parallel analyses with a neutral and a cationic HILIC column, using mobile phases of varied compositions and pH. The results indicate that: (i) the proportion of carboxylic acids in the humic substances from terrestrial origins is less than half of that from treated wastewater (Jeddah, KSA), (ii) a higher content of basic compounds was observed in the humic substances from treated wastewater and Ribou Reservoir (Cholet, France) than in the sample from Loire River (France), (iii) a higher percentage of hydrophobic macromolecules were found in the humic substances from Loire River than in the other samples, and (iv) humic substances of treated wastewater contained less ionic neutral compounds (i.e., pKa 5–9) than the waters from terrestrial origins. The physicochemical property disparity amongst the compounds in each humic substances sample was also evaluated. The humic substances from the lightly humic Loire river displayed the highest disparity, whereas the highly humic Suwannee river (Georgia, USA) showed the most homogeneous humic substances.  相似文献   

18.
硝酸氧解法提高泥炭中黄腐酸的产率   总被引:6,自引:0,他引:6  
何云龙  刘大强 《应用化学》2003,20(12):1220-0
硝酸氧解法提高泥炭中黄腐酸的产率;腐植酸;硝酸氧化降解  相似文献   

19.
Summary Although the binding of pesticides to organic carbon in soil, especially to humic acid (HA), is well recognized, the mechanisms have not been completely explained. This publication deals with adsorption of atrazine and terbuthylazine by humic acid under different experimental conditions, including adsorption times longer than those used hitherto. Direct HPLC analysis of HA suspensions is assessed as an alternative to more complicated techniques for estimation of free triazines, and compared with combined solid-phase extraction and HPLC. Experimental conditions such as time of exposure, addition of neutral salt, pH of the suspension, and HA concentration have a significant impact on the extent of triazine adsorption. At alkaline pH, triazines become partitioned in the HA fraction because of its hydrophobicity, whereas at acidic pH hydrogen-bonding probably occurs between triazine molecules and humic acid polymers. Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999  相似文献   

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