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1.
利用三维荧光激发.发射光谱(3DEEMs)及荧光偏振法研究了3例腐殖酸和1例湖泊溶解有机物(DOM)在不同腐殖酸浓度、离子强度和pH条件下的荧光光谱特性.实验结果表明,随着浓度增大,各腐殖酸样的荧光强度增大,其中垃圾渗滤液腐殖酸和Pahokee泥炭腐殖酸的荧光峰出现红移.随着浓度进一步增大,腐殖酸的荧光偏振值增大,由此推断在此浓度范围内腐殖酸由于分子间的排斥作用使其构型出现伸展.离子强度增大导致腐殖酸及阿哈湖DOM的荧光强度降低.随着氯化钾(KCI)浓度增大,Fluka腐殖酸的荧光峰A蓝移,荧光峰B的荧光偏振值出现减小,推测是由于静电中和作用使其荧光基团发生卷曲造成的.离子强度对其余腐殖酸样和阿哈湖DOM的其他荧光特性没有明显的影响.总的来说,pH值的变化对腐殖酸和湖泊DOM的荧光特征的影响是很明显的.随着pH值增大,腐殖酸和湖泊DOM的荧光强度增强.而pH值减小时,Fluka腐殖酸和Pahokee泥炭腐殖酸的荧光峰(A峰)蓝移,当pH值降到5时,Fhka腐殖酸的荧光峰突然红移到最大,随后又继续蓝移;垃圾渗滤液腐殖酸和阿哈湖DOM的荧光峰位无明显的漂移.所有样品的荧光偏振值都减小(但阿哈湖DOM的A峰变化不大),但在pHi≤5时又增大,这种现象表明随着pH值降低,腐殖酸和湖泊DOM中有机大分子发生卷曲,但在pH≤5时由于羧基的质子化又以平面伸展构型出现在溶液中.  相似文献   

2.
The topsoil temperature in arid areas of Xinjiang, China can be up to about 80°C in summer. This may significantly affect the chemical properties of soil humic substances. However, the effects of high temperature on characteristics of soil humic substances and their complexation with toxic metals are still poorly known. In the present study, binding of Hg(II) to unheated soil humic substances and heated soil humic substances from sandy soils was comparatively investigated using three-dimensional excitation?Cemission matrix (EEM) fluorescence spectroscopy. Two fluorescent peaks (peak I at Ex/Em?=?365?C370/470?C474?nm; peak II at Ex/Em?=?270?C275/468?C472?nm) identified as humic-like fluorescence were observed in the EEM spectra of humic substances. Both peaks were clearly quenched by Hg(II), indicating the strong interaction of humic-like substances with Hg(II), and showed blue shifts after heat treatment. Heat treatment caused an increase of the fraction of accessible fluorophore (f a), binding sites number (n) and effective quenching constants (logK a), indicating that more binding sites in humic substances could bind Hg(II) and form more stable humic substances?CHg(II) complexes after heat treatment. However, a decrease of binding constants (logK b) suggested that heat treatment would reduce the binding capacity of each binding site of humic substances to Hg(II). This study implies the transport of Hg(II) may be affected by high temperature in the arid zone due to the modification of the physicochemical properties of humic substances in soil.  相似文献   

3.
1IntroductionDissolvedorganicmatter (DOM)isamixtureoforganicsubstancesconsistingmainlyofhighmolecularweightpolymericcompounds (KenandLee,1 974) .Itplaysanimportantroleincarboncyclingandbiogeochemicalmobilizationoftracemetalsandorganiccompoundsintheaquaticenvi ronment (BeffleandLeppard ,1 995) .InrecentyearsmanyresearchershavepaidattentiontothesecomplexesbasedontheMWDofDOM ,sincethefateandtransportoftracechemicalsareinfluencedbyitsmolecularsize (Chiouetal.,1 986) .Themolecularweightorfrac…  相似文献   

4.
洱海沉积物孔隙水中溶解有机质的三维荧光光谱特征   总被引：17，自引：0，他引：17  
文章应用三维荧光光谱技术对洱海沉积物孔隙水中的溶解有机质进行了研究。结果表明,所有样品均含有4个明显的荧光峰,其中A和C为类腐殖酸荧光,B和D为类蛋白荧光。荧光强度在沉积物-水界面特别强,在1cm处急剧下降,之后随着沉积深度呈上升趋势。孔隙水溶解有机质均具有强的类蛋白荧光,揭示了溶解有机质中含有大量色氨酸、酪氨酸等芳环结构的类蛋白物质,并且在早期成岩过程中随着沉积深度呈积累趋势;类蛋白荧光与类腐殖酸荧光之间具有一定的相关关系,r(A,C)值在0.94-1.79之间,随着沉积深度逐渐下降,r(D,B)值在0.9-1.75之间,与r(A,C)值极为接近,且随着沉积深度有着类似的变化趋势,说明在洱海沉积物孔隙水中,r(D,B)与r(A,C)之间具有一定的相关性。  相似文献   

5.
Previous studies showed that water chemistry and concentrations of dissolved organic matter (DOM) could affect its molecular conformation and binding characteristics with hydrophobic organic contaminants (HOCs). However, the conformational change of DOM resultant from water chemistry and concentrations of DOM was not extensively investigated; therefore, the contradictory reports regarding the binding property with HOCs were available in literature. In this study, the effects of ionic strength, pH and DOM concentrations on the fluorescence properties of two humic acids (HA), namely Fluka HA and Amherst HA, were investigated by three-dimensional excitation-emission matrix fluorescence spectroscopy (3DEEM) and steady-state fluorescence polarization (FP) techniques. The results not only corroborated previous observations obtained by other investigators, but revealed some new information about the fluorescence properties and molecular conformation of the humic acids under different water chemistry and DOM concentration conditions, which could shed light on its binding mechanisms and binding properties with HOCs.  相似文献   

6.
The adsorption characteristics of natural organic matter (NOM) were investigated on the basis of fluorescence excitation emission matrix (EEM) by using four different coal-based activated carbons (ACs). For each AC, batch adsorption isotherms were analyzed using a modified Freundlich isotherm model on the basis of the fluorescence intensity of three major fluorescence peaks appeared in the fluorescence EEM reported to be reflective of the humic acid-like (P1), fulvic acid-like (P2) and aromatic protein-like (P3) substances, respectively, together with the well-used overall quality indices of dissolved organic carbon (DOC) and ultraviolet absorbance at the wavelength of 260 nm (UV260). It was found that, for all five quality indices, the adsorption capacity differed with the ACs used, and the modified Freundlich isotherm constant K estimated for P1, P2 and P3 was in close correlation with that of the total organic matter evaluated by DOC. Moreover, no matter which AC was concerned, the magnitude of the estimated K and the removal rate over a broader range of AC dose for P3 were apparently smaller than those for P1 and P2, suggesting the adsorbability of aromatic protein-like substances was lower than that of the humic acid-like and fulvic acid-like substances. The dependency of the adsorption capacity of NOM on the volume of pores in some specific size ranges of the ACs was also revealed.  相似文献   

7.
段磊  杨胜科  王文科 《地学前缘》2021,28(5):104-113
研究抗生素在浅层地下水中不同相态间的分布特征,对于了解抗生素的行为特征及评估其危害具有重要的意义。本文利用三维荧光淬灭法研究了胡敏酸(humic acid, HA)对磺胺嘧啶(sulfadiazine, SD)在地下水中不同相态间分布规律的影响及相互作用,探讨了HA浓度、pH值、温度对SD在不同相态间分布的影响,对淬灭过程进行拟合并计算了分配系数、淬灭参数以及热力学参数。结果表明:地下水中SD浓度(0.5 mg/L)较低时或者HA浓度增加(0~20 mg/L)时,HA可显著促进悬浮相中SD比例的增加;SD对HA的淬灭机理为形成复合物的单一静态淬灭,结合位点数均约为1,荧光淬灭常数Ksv为5.271×103 L/mol,淬灭速率常数Kq为5.271×1011 L/(mol·s),属于自发的放热过程;体系处于低温(15 ℃)、弱碱性(8~10)pH值环境时,SD对HA的淬灭作用最强,HA对SD进入悬浮相的促进作用最明显。  相似文献   

8.
A simple method based on high-performance size-exclusion chromatography (HPSEC) has been developed for rapid quantification of humic and fulvic acids (HA and FA) in stream waters. A Tsk-gel column was used to separate natural dissolved organic matter (DOM) into two components: peak A and B. In terms of HPSEC chromatograms and fluorescence patterns, peak A and B were similar to the corresponding XAD-extracted HA and FA, respectively. It is suggested that peak A fraction mainly consisted of HA, and peak B fraction FA. The similar separation of HA and FA using HPSEC and a conventional XAD method suggests the consistency of molecular size distribution and physical–chemical properties of DOM. HPSEC offers a simple and rapid method for the quantification of HA and FA instead of tedious extractions of humic substances. Analyses of natural water samples show that the calculation of HA/FA based on UV absorbance was under- or over-estimated, the calibration using the extracted HS allows a more accurate quantification. The fast screening of HA and FA provides useful quantitative and qualitative information that can be used in environmental or monitoring studies.  相似文献   

9.
为了提高复杂环境水体中雌激素污染的检测性能,通过直接吸附法将核酸适配体固定在氧化石墨烯表面,合成出核酸适配体修饰氧化石墨烯复合物,并将其应用于17β-雌二醇水体污染的高灵敏和特异性均相检测。采用紫外可见分光光谱分析核酸适配体修饰氧化石墨烯复合物,发现该复合物在250 nm处有较宽的肩峰,证明核酸适配体成功固定在氧化石墨烯表面。通过荧光分光光度计分析核酸适配体修饰氧化石墨烯复合物与目标物17β-雌二醇反应前后的荧光强度变化,发现荧光强度由峰值110增加到峰值450,表明该复合物可以成功用于对17β-雌二醇的检测,并且荧光强度与17β-雌二醇的质量浓度在10~100 μg/L范围内呈正比,最低检出限为6.2 μg/L。  相似文献   

10.
腐泥煤变质系列的红外光谱和X衍射特征   总被引：4，自引：1，他引：4  
对淄博、滕县两煤田不同煤级与腐植煤共生的腐泥煤系列进行了对比研究。红外光谱特征为：反映芳环－Ｃ＝Ｃ－键伸缩和弯曲振动的１６００ｃｍ－１峰的吸收值都小于共生腐植煤；反映芳烃ＣＨ基团面外弯曲振动的８８０ｃｍ－１峰只在腐植煤中出现，而８１０ｃｍ－１峰的吸收值全部高于腐植煤；两次出现了在腐植煤中从未出现过的８１０ｃｍ－１＞７５０ｃｍ－１的情况；芳烃结构指数＞０８，而腐植煤则全部＜０８。Ｘ线衍射结果：ＬＣ都随煤化作用的进行逐渐增大，在Ｃｄａｆ为９２％±达峰值，然后又逐渐变小；两个系列相比，全都是腐泥煤较大；Ｌａ都随煤化作用的进行逐渐增大，大部分腐植煤比腐泥煤的大；ｄ（００２）都随煤化作用的进行逐渐变小，两个系列相比都是腐泥煤的较小。  相似文献   

11.
Here we report on an investigation of the three-dimensional excitation-emission-matrix (EEM) fluorescence spectra of unconcentrated water samples collected in 1996, 1998 and 1999 at a site particularly propitious for macro-algae development. The degradation of these macro-algae was studied to determine the influence of their exudates on natural water EEM fluorescence spectra. This work demonstrates that biological activity is one of the major factors involved in the formation of the blue-shifted fluorescence band observed in marine waters (β component Ex/Em=310–320 nm/380–410 nm); our study also shows that fluorescence can be used to evaluate the biological activity both quantitatively and to determine its different phases.  相似文献   

12.
近岸沉积物再悬浮期间所释放溶解有机物的荧光特征   总被引：9，自引：0，他引：9  
对采自厦门湾九龙江人海河口的4个沉积物样品进行了室内再悬浮模拟实验,利用荧光激发-发射矩阵光谱(EEMs)研究了再悬浮过程中从沉积物中释放出的有色溶解有机物(CDOM)的荧光特征,同时通过与相应站位沉积物间隙水和底层水的对比分析,探讨了河口近岸海域的沉积物再悬浮作用作为水体中溶解有机物来源之一的可能性.结果表明,对给定站位,CDOM相对荧光强度和溶解有机碳(DOC)含量分布变化非常一致,均为间隙水最高,再悬浮次之,底层水最低;站位之间,底层水和再悬浮水样中CDOM相对荧光强度随盐度的降低而增加,从海端向河端增加的趋势明显.EEMs分析表明,各样品中均存在类腐殖质荧光与类蛋白质荧光团,且模拟实验也表明再悬浮作用可释放类腐殖质与类蛋白质荧光物质到底层水中,表明底质再悬浮将是近岸水体中CDOM的一个重要来源.与相应的底层水相比,间隙水的荧光峰(如峰A/C)的位置发生红移.再悬浮样品中EEMs的荧光团同时表现出相应底层水和间隙水的特征,但是荧光峰(峰A和峰C)的最大激发和发射波长更接近底层水中相应荧光团,与间隙水相比,则发生谱峰位置的蓝移.近海端样品中荧光峰M明显,随着盐度的降低,底层水和再悬浮水样的γ(M/C)值逐渐降低,且海源的峰M由海端向河端逐渐消失,表明峰M属于海洋自生来源.本研究区域DOM的荧光指数在1.61～1.93之间,表明近海端样品DOM主要为生物来源,而近河端样品DOM主要为陆源输入,或者为陆源与生物活动共同作用的结果.  相似文献   

13.
三维荧光光谱是20世纪80年代发展起来的一种新的荧光分析技术,其与紫外荧光光谱相比,前者能获得激发波长和发射波长同时变化时的荧光强度信息,在多组分混合物的定性与定量分析、在环境、生物、化学等方面的应用较成熟,而在珠宝玉石的测试与研究中则应用较少。选取山东蒙阴矿区产出的25颗钻石样品作为研究对象,采用三维荧光和紫外荧光对其进行了测试与分析。结果表明,该钻石样品的三维荧光光谱特征可分为无荧光谱峰、单荧光谱峰、双荧光谱峰和3个荧光谱峰4种类型,与其紫外荧光特征呈一一对应关系。  相似文献   

14.
In this study, nineteen brine samples from the Qarhan Salt Lake (QSL) in western China were collected and analyzed for boron (B) and chlorine (Cl) concentrations, total dissolved solids (TDS), pH values and stable B isotopic compositions. The B concentrations and δ11B values of brines in the QSL range from 51.6 mg/L to 138.4 mg/L, and from +9.32‰ to +13.08‰, respectively. By comparison of B concentrations and TDS of brines in QSL with evaporation paths of brackish water, we found that B enrichment of brines primarily results from strong evaporation and concentration of Qarhan lake water. Combining with comparisons of B concentrations, TDS, pH values and δ11B values of brines, previously elemental ratios (K/Cl, Mg/Cl, Ca/Cl, B/Cl) and δ11B values of halite from a sediment core (ISL1A), we observe good correlations between B concentrations and TDS, TDS and pH values, pH and δ11B values of brines, which demonstrate that higher B concentrations and more positive δ11B values of halite indicate higher salinity of the Qarhan paleolake water as well as drier paleoclimatic conditions. Based on this interpretation of the δ11B values of halite in core ISL1A, higher salinity of the Qarhan paleolake occurred during two intervals, around 46–34 ka and 26–9 ka, which are almost coincident with the upper and lower halite-dominated salt layers in core ISL1A, drier climate phases documented from the δ18O record of carbonate in core ISL1A and the paleomoisture record in monsoonal central Asia, and a higher solar insolation at 30°N. These results demonstrate that the δ11B values of halite in the arid Qaidam Basin could be regarded as a new proxy for reconstructing the salinity record of paleolake water as well as paleoclimate conditions.  相似文献   

15.
This study examined the dissolved organic matter (DOM) components of cow dung using a combination of fluorescence (excitation–emission matrix, EEM) spectroscopy and parallel factor (PARAFAC) modelling along with eleven trace metals using ICP-MS and nutrients (NH4+ and NO3?) using an AA3 auto analyser. EEM–PARAFAC analysis demonstrated that cow dung predominantly contained only one fluorescent DOM component with two fluorescence peaks (Ex/Em = 275/311 nm and Ex/Em = 220/311 nm), which could be denoted as tyrosine by comparison with its standard. Occurrence of tyrosine can be further confirmed by the FTIR spectra. Trace metals analysis revealed that Na, K and Mg were significantly higher than Ca, Fe, Mn, Zn Sr, Cu, Ni and Co. The NH4+ concentrations were substantially higher than NO3?. These results thus indicate that the dissolved components of the cow dung could be useful for better understanding its future uses in various important purposes.  相似文献   

16.
This paper deals with the influences of pH, acidity and ionic intensity of the solutions on the resonance Rayleigh scattering spectra and fluorescence spectra of humic acid. When the pH value is low and the acidity and ionic intensity are high, the resonance Rayleigh spectra and fluorescence spectra both show a tendency of increasing, though the former’s intensity is much higher. In combination with the transmission electron microscope data, the factors leading to the occurrence and enhancement of the resonance Rayleigh scattering spectra of humic acid were explored. It is considered that particle enlargement caused by aggregation, the increase of heterogeneity, the increase of hydrophobility, the formation of interface, etc., are the factors leading to the occurrence and enhancement of the resonance Rayleigh scattering spectra of humic acid. As the intensity of the resonance Rayleigh scattering spectra of humic acid is much higher, resonance Rayleigh scattering spectroscopy can be used as a newly developed spectrum technology, which is more sensitive and simpler, to study humic acid and its complicated behaviors.  相似文献   

17.
Equilibrium dialysis was used to measure Co- and Cu-binding by an isolated peat humic acid (PHA) in controlled laboratory experiments under simulated estuarine conditions: ionic strengths of 0.005 to 0.7 M in NaCl and mixed Na-Mg-Ca chloride solutions, with trace metal concentrations of ∼5 × 10−7 M, a PHA concentration of 10 mg/L, and at constant pH values of ∼7.8 (Co and Cu) and ∼4.6 (Cu only). Generally, Co- and Cu-humic binding decreased substantially with increasing ionic strength and, in the case of Cu, with decreasing pH. The presence of seawater concentrations of Ca and Mg had a relatively small effect on Co-humic binding and no measurable effect on that of Cu under the experimental conditions. The binding data were well-described by an equilibrium speciation code (the Windermere Humic Aqueous Model, WHAM) after optimising the fits by varying the metal-proton exchange constants for humic acid within justifiable limits (i.e., within 1 standard deviation of the mean exchange constants used in the WHAM database). The main factor producing the observed variations in metal-humic binding at constant pH was the electrostatic effect on the humic molecule. WHAM was used to predict Co- and Cu-humic binding in simulations of real estuaries. Co-humic binding is predicted to be relatively unimportant (generally <5% of total Co), whereas the Cu-humic complex is likely to be the dominant species throughout an estuary. The main factors producing changes in Co- and Cu-humic binding in the real-estuary simulations are the electrostatic effect on the humic molecule, ligand competition (mainly from carbonate species) for metals, and to a lesser extent Ca and Mg competition for humic binding sites. Variations in pH are significant only at the freshwater end of an estuary. WHAM simulations also indicated that competition effects between metals are more likely to occur in freshwaters than in seawater, due to enhanced electrostatic binding at low ionic strength.  相似文献   

18.
Cd Te量子点具有荧光强度高和稳定性好的优点,应用Cd Te量子点荧光猝灭法分析基体复杂的样品,需要有效分离对测定干扰的金属元素和高效富集待测元素。本文以巯基乙酸(TGA)作稳定剂,采用水相合成法制备了巯基乙酸修饰的Cd Te量子点,基于镍离子在p H=10.0硼砂缓冲溶液中对Cd Te量子点的荧光具有较强猝灭作用,建立了一种测定赤泥中痕量镍的荧光光度方法。荧光猝灭反应的最佳实验条件为:Cd Te量子点的浓度3.0×10-4mol/L,反应温度为室温,反应时间10 min,在此条件下镍离子浓度在2.0×10-7~7.8×10-5mol/L范围内与Cd Te量子点的相对荧光强度呈良好的线性关系;方法检出限为1.5×10-7mol/L。本方法针对Fe3+、Co2+、Cu2+等主要基体金属元素允许量低的问题,采用25%的2-羟基-4-仲辛氧基二苯甲酮肟(N530)磺化煤油萃取回收滤液中的Ni2+,镍回收率达到99%以上;赤泥中痕量镍的测定结果与催化光度法相符,加标回收率为98.3%-104.2%。  相似文献   

19.
To elucidate the influence of tidal marshes on the amount and chemical structure of chromophoric dissolved organic matter (CDOM) in adjacent coastal waters, surface water samples were collected along three cross-marsh transects in tidal marshes within the Changjiang Estuary. In addition, three sediment cores were collected from the marshes and incubated for 10 h in the laboratory after adding overlying tidal waters. Nutrients, DOC, absorption, fluorescence excitation–emission matrix (EEM) spectroscopy, and other parameters were measured in these samples, which clearly illustrated releases by the tidal marshes of DOC, and CDOM absorbent and fluorescent molecules. To characterize the chemical nature of the marsh-derived CDOM, variations in a suite of optical indices (including molar absorptivity, absorption spectral slope, fluorescence quantum yield, and fluorescence ratios between certain excitation/emission locations) in these samples were plotted against the offshore distance of the stations as well as the incubation time. From the literature, it has been suggested that these variations are closely associated with molecular weight, aromaticity, and humic/fulvic or allochthonous/autochthonous ratios in the CDOM mixtures. This study showed that the CDOM fluorophores changed to more humic-like and were less protein-like from sea to land across the marsh gradients. Furthermore, subtractions between EEM spectra before and after laboratory incubations were applied to illustrate in greater detail the properties of the pure fluorescent compounds exchanged at the sediment–overlying water interface.  相似文献   

20.
A transect of the St Marys River estuary from above the point of maximum salt wedge penetration to coastal salinities was conducted in July 1999. None of the parameters examined—dissolved organic carbon (DOC) content, UV light absorbance at 254 nm, and Total Luminescence spectra—follow the rule of conservative mixing. The characteristics of the different molecular size fractions of the St Marys River natural organic matter (NOM), as well as the results of a laboratory mixing experiment, provided evidence that loss of larger molecular size compounds from riverine NOM may occur by coagulation at salinities up to 10. An apparent gain of carbon in the lower estuary was attributed to exports from abundant coastal marshes in this area. The Total Luminescence spectra of the riverine NOM can be described by two peaks, centered respectively around 340/445 nm, and 230/430 nm Excitation/Emission Wavelength Pair (EEWP), which are characteristic of humic materials of aquatic origin. The samples from the high salinity stations exhibit peaks at lower emission wavelength EEWP 320/424 nm, which can be considered as marine humic-like material. The presence of amino acid-tryptophan like peaks were observed, with EEWP 300/350 nm in some of the high salinity samples. This peak was of high relative fluorescence intensity. It is hypothesized that the intense biological activity of the salt marsh and near coastal area is responsible for the carbon addition as well as the appearance of the highly fluorescence amino acid-protein like material.  相似文献   

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