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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.
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   

3.
The effect of protons, low molecular weight organic ligands, soil humic acid (HA), and stream water dissolved organic matter (DOM) on the rate of dissolution of kaolinite was examined. In acid solution (no ligands present) the rate of dissolution increased with increasing [H+] and the rate of Si dissolution was generally faster than Al. Low molecular weight organic ligands markedly increased the dissolution rates of both Al and Si in the following order: oxalate > malonate ≈ salicylate > o-phthalate. In the presence of organic ligands, the rate of Al dissolution was generally much greater than Si. Soil HA and stream water DOM did not promote the dissolution of kaolinite under the experimental conditions examined in this study.

The dissolution kinetics of Al were interpreted in terms of a surface complexation model and the rate equations described in terms of the concentrations of specific (i.e. inner sphere) surface complexes.  相似文献   


4.
The structural, spectroscopic and phenanthrene binding characteristics were compared for humic acids (HA) extracted from two different sources: eight soils and six lake sediments. The elemental analysis revealed that HA from sediments had higher H/C, N/C, and (N + O)/C ratios compared to HA from soils, reflecting a lower degree of humification and more autochthonous organic input upon the formation of the HA for lake sediments versus soil environments. HA from soils exhibited a higher content of aromatic carbon structures than the sediment HA based on 13C NMR results. The source of HA was easily distinguished by comparing the synchronous fluorescence spectra of each HA group. The presence of a protein like fluorescence was prominent for the HA from sediment while it was minor for the HA from soil. Irrespective of the HA source, however, humification index (HIX) exhibited a common positive correlation with the aromatic content, and a negative correlation with O-alkyl carbon structures of the HA. The correlations were consistent with the general structural trends of humification processes, suggesting that HIX may serve as a source independent predictor to describe the structural information and humification degree of terrigenous HA. Aromatic carbon structures did contribute to enhancing the phenanthrene binding for both sources of HA. However, the primary structures associated with non-ideal phenanthrene binding (i.e., non-linear sorption isotherm) appear to differ by the HA source because the opposed correlations were obtained between aromaticity and the isotherm linearity for the two HA groups. Our results suggest that the HA structural function associated with specific non-linear sorption for hydrophobic organic contaminants (HOCs) may be more strongly governed by the HA source than by the apparent physico-chemical properties.  相似文献   

5.
The phosphorus content of marine humic acids (HA) is in the range of 0.1–0.2%. The C/P ratios of the HA are 300 to 400. Marine fulvic acids (FA) contain 0.4–0.8% P and have C/P ratios of 80 to 100. High molecular weight organic matter dissolved in pore waters (DOM) contains 0.5% P and has C/P of 90. The data suggest that during the formation sequence: Plankton → DOM → FA → HA → Kerogen, phosphorus is lost, mainly in the FA → HA (and possibly also in the HA → Kerogen) step. Diagenesis of sedimentary humic acids is accompanied by loss of phosphorus (as well as of nitrogen) to form HA with C/P ratios of 1000.Soil humic substances resemble marine humates in P content (0.3%) and soil FA's are about three to fivefold enriched in P relative to HA. C/P ratios are lower in soil HA (ca. 200) as compared with marine HA. Humic acids from diagenetic products such as peat and lignite are highly depleted in P. Rough calculations indicate that humate bound P may account for 20–50% of the organic phosphorus reservoir in sediments. The chemical speciation of this P is unknown, but lack of correlation with ash, Fe, Ca or Al content (in marine humates, at least) indicates that it is organically bound.  相似文献   

6.
为探究溶解性有机质(DOM)不同相对分子质量组分对药物和个人护理品(PPCPs)类污染物吸附过程的影响,以卡马西平(CBZ)为目标污染物,以石英砂代表无机矿物,用商用腐殖酸(HA)制备DOM并进行超滤分级,然后开展吸附实验,并采用荧光光谱和红外光谱表征等手段,研究了DOM不同分子质量组分对石英砂吸附CBZ的影响及机制。结果表明,以3 000和10 000的超滤膜进行分级后的不同相对分子质量HA结构有明显差别,大分子质量HA中苯环等疏水性结构以及羟基的含量较多,芳香构造化程度高,多为分子量较高、稳定性较好的疏水性有机物,但中、小分子质量HA结构差异不大,含有更多羰基、羧基等含氧官能团,主要是一些分子质量较小的亲水物质; DOM不同分子质量组分对CBZ在石英砂上的吸附有明显影响,其中大分子质量组分促进吸附,而中、小分子质量组分抑制吸附,原因在于大分子质量组分可疏水结合于矿物表面,增加介质表面的活性吸附位点,同时其芳香性或脂肪性结构可与CBZ的疏水基团发生疏水作用共吸附或累积吸附于介质表面,从而促进CBZ的吸附;而中、小分子质量DOM的极性官能团可与CBZ酰胺部分通过极性作用结合,对CBZ分子有增溶作用,从而抑制吸附。  相似文献   

7.
卤水中溶解性有机质(dissolved organic matter,DOM)会对盐田日晒工艺和产品质量产生不利影响,如盐田卤水的蒸发速率减缓、蒸发度减小以及提取的矿物产品带有刺鼻的气味、浓重的颜色等。因此,对具有资源开发利用价值的卤水体系中DOM结构和性质的研究可以为后续DOM的有效去除或在DOM共存体系中调控无机盐结晶工艺路线提供有效的指导意见。本文以自然界中广泛存在的两种不同类型的卤水体系,即盐湖卤水DOM(SLDOM)和油田卤水DOM(OFDOM)为研究对象,采用溶解性有机碳(dissolved organic carbon,DOC)分析、光谱学分析和平行因子分析等手段对DOM的含量、分子量分布特征、光谱学结构和光降解行为开展了研究。DOC和荧光分析表明SLDOM和OFDOM的DOC含量和生物指数(BIX)值相似;与OFDOM相比,SLDOM的腐质化指数(HIX)值和高分子量组分(HMW)比例偏高;特别吸收光谱(SUVA254)和糖类化合物含量检测结果表明,SLDOM和OFDOM的HMW组分中含有的芳香类和糖类化合物所占比例比低分子量组分(LMW)高;三维荧光谱图分析(EEM)结果表明,SLDOM主要以腐殖质类物质为主,而OFDOM以蛋白质类组分为主。此外,DOM的荧光组分在不同分子量中的分布也存在明显差异:对于SLDOM,富里酸主要分布在HMW DOM中,而腐殖酸主要在LMW DOM中;对于OFDOM,芳香胺类蛋白组分主要分布在HMW DOM中,色氨酸和酪氨酸类蛋白组分主要分布在LMM DOM中。在光降解实验中,SLDOM和OFDOM的DOC含量随光照时间增加而逐渐减少,分别下降了29.32%和15.11%。进一步的分析表明,光照过程中两种卤水中糖类化合物均减少,小分子量的DOM优先分解。此外,在光照过程中SLDOM芳香类化合物增加,腐质化程度基本不变;OFDOM芳香类化合物减少,腐质化程度增加。EEM平行因子分析(PARAFAC)结果表明,SLDOM荧光组分在光降解过程中荧光强度增加,而OFDOM荧光强度减少。  相似文献   

8.
Little is known of potential reactivity and redox properties of reduced dissolved organic matter (DOM), although DOM in anoxic environments, e.g., groundwater, peat soils, or lake sediments, can be expected to differ from DOM of oxidized environments. We therefore investigated the impact of electrochemical and wet chemical [hydrogen (H2)/Pd catalyst] reduction in Sigma-Aldrich humic acid (HA) as a model DOM for high salinity, high ionic strength, or iron-rich systems on its reactivity toward sulfide. Mediated electrochemical measurement showed that the reactivity of HA toward sulfide decreased in the order non-reduced HA > electrochemically reduced (?0.1 V) HA > H2/Pd-reduced HA > electrochemically reduced (?0.4 V) HA. Results indicated that measured initial values of electron-accepting capacities of HA had a strongly positive correlation with the sulfide transformation, except for the H2/Pd treatment of HA. This latter treatment obviously changed HA structures and lead to a different reactivity toward sulfide, limiting a direct comparison to electrochemically reduced organic matter. Our result confirmed that reduced HA was still reactive toward sulfide, although to a lower extent compared with oxidized HA. Compared to electrochemical reduction, H2/Pd pre-treatment of HA alters redox properties and reactivity of organic matter and may therefore lead to results that cannot be transferred to natural systems.  相似文献   

9.
1IntroductionDissolvedorganicmatter (DOM)isamixtureoforganicsubstancesconsistingmainlyofhighmolecularweightpolymericcompounds (KenandLee,1 974) .Itplaysanimportantroleincarboncyclingandbiogeochemicalmobilizationoftracemetalsandorganiccompoundsintheaquaticenvi ronment (BeffleandLeppard ,1 995) .InrecentyearsmanyresearchershavepaidattentiontothesecomplexesbasedontheMWDofDOM ,sincethefateandtransportoftracechemicalsareinfluencedbyitsmolecularsize (Chiouetal.,1 986) .Themolecularweightorfrac…  相似文献   

10.
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11.
鲁宗杰  邓娅敏  杜尧  沈帅  马腾 《地球科学》2017,42(5):771-782
水体中溶解性有机质(dissolved organic matter, DOM)是含水层中砷释放的主控因素之一.江汉平原河湖众多、沟渠广布,地表水体与浅层地下水的交互作用使得DOM的组分特征及其强度有显著差异.为查明江汉平原地下水中溶解性有机质在砷迁移转化过程中的作用,对江汉平原地表水和浅层地下水进行三维荧光光谱分析,使用平行因子分析法提取水体中有机质的分子组成、功能特点和荧光特征,并分析各组分相对含量与地下水中砷与铁的关联.江汉平原水体中DOM包括3种主要组分,组分C1、C2为类腐殖质,C2是生物降解过程中产生的小分子,C3为类蛋白物质.地下水DOM以类腐殖质组分C1、C2为主,地表水以类蛋白类物质C3和小分子腐殖质C2为主.高砷地下水中DOM以陆源为主,主要通过两种途径促进As的迁移转化:(1) DOM的腐殖质组分充当微生物群落的电子运输工具,促进微生物作用下的有机质氧化和铁氧化物的还原,并伴随As的释放及大量溶解性有机碳(dissolved organic carbon, DOC)和HCO3-的产生;(2) As以铁等金属阳离子为桥接物与腐殖质结合,通过形成As-Fe-DOM络合物,导致地下水中砷的迁移.   相似文献   

12.
Brown coals with high Au and PGE concentrations from six deposits in the southern Russian Far East were analyzed for elemental composition, acid-base properties, and the molecular-size distribution of humic acids (HA). The ash contents of the coals were determined to be negatively correlated with their Au concentrations, and the content of “organic Au” (which is chemically bound to humic substances, HS) reaches 95%. The most probable mode of Au occurrence in the brown coals is submicrometer-sized particles of elemental gold stabilized by HA. Quantum-mechanical calculations of interactions between Au(0) clusters with model HS fragments confirm that HS could be originally strongly chemically adsorbed on the surface of elemental gold particles. Different stability of colloids during centrifuging of alkali extracts of the gold-bearing brown coals was proved to be likely responsible for the selective separation of free HA and those bound with gold particles, and this can be used to develop a technology for gold recovery from coals without decomposing their organic matrix.  相似文献   

13.
《Applied Geochemistry》2003,18(7):955-972
This review highlights the major progress over the last decade on characterization of geochemically heterogeneous soil/sediment organic matter (SOM) and the impacts of SOM heterogeneity on sorption and desorption of hydrophobic organic contaminants (HOCs) under equilibrium and rate limiting conditions. Sorption and desorption by soils and sediments are fundamental processes controlling fate and transport of less polar and nonpolar organic pollutants in surface aquatic and groundwater systems. Recent studies have shown that soils and sediments exhibit an array of HOC sorption phenomena that are inconsistent with an early partition model based on an assumption of homogeneous gel-like SOM. Increasing data have revealed that isotherm nonlinearity, varied sorption capacity, sorption–desorption hysteresis, and slow rates of sorption and desorption are characteristics for HOC sorption by soils and sediments. These phenomena have been shown to result from different types of condensed SOM that exhibit capacity limiting sorption processes. Recent findings of glass transition phenomena and the nonlinear HOC sorption by humic acids provide a scientific foundation for drawing an analogy between humic acids and synthetic organic polymers that supports a dual mode model for sorption by soils and sediments. Humic acid is glassy or rigid at temperatures lower than its glass transition temperature and exhibits relatively nonlinear sorption isotherms for HOCs. Fractionation and quantification of SOM indicate that soils and sediments contain significant amounts of black carbon and kerogen of different origins. These particulate organic materials have rigid 3-dimensional structures and are often less polar compared to humic substances. Limited studies show that black carbon and kerogen exhibit nonlinear sorption for HOCs and may dominate the overall nonlinear sorption by soils and sediments.  相似文献   

14.
Vast amounts of knowledge about the proton- and metal-binding properties of dissolved organic matter (DOM) in natural waters have been obtained in studies on isolated humic and fulvic (hydrophobic) acids. Although macromolecular hydrophilic acids normally make up about one-third of DOM, their proton- and metal-binding properties are poorly known. Here, we investigated the acid-base and Cu-binding properties of the hydrophobic (fulvic) acid fraction and two hydrophilic fractions isolated from a soil solution. Proton titrations revealed a higher total charge for the hydrophilic acid fractions than for the hydrophobic acid fraction. The most hydrophilic fraction appeared to be dominated by weak acid sites, as evidenced by increased slope of the curve of surface charge versus pH at pH values above 6. The titration curves were poorly predicted by both Stockholm Humic Model (SHM) and NICA-Donnan model calculations using generic parameter values, but could be modelled accurately after optimisation of the proton-binding parameters (pH ? 9). Cu-binding isotherms for the three fractions were determined at pH values of 4, 6 and 9. With the optimised proton-binding parameters, the SHM model predictions for Cu binding improved, whereas the NICA-Donnan predictions deteriorated. After optimisation of Cu-binding parameters, both models described the experimental data satisfactorily. Iron(III) and aluminium competed strongly with Cu for binding sites at both pH 4 and pH 6. The SHM model predicted this competition reasonably well, but the NICA-Donnan model underestimated the effects significantly at pH 6. Overall, the Cu-binding behaviour of the two hydrophilic acid fractions was very similar to that of the hydrophobic acid fraction, despite the differences observed in proton-binding characteristics. These results show that for modelling purposes, it is essential to include the hydrophilic acid fraction in the pool of ‘active’ humic substances.  相似文献   

15.
In order to better understand the compositional and structural complexity of dissolved organic matter (DOM) macromolecules and provide mechanistic information on the binding of hydrophobic organic contaminants (HOCs) to DOM, we fractionated large amounts of lake water into three hydrophobic DOM-fractions. The variation of the partitioning coefficients (K DOC) of pyrene at different pH levels was examined by florescence quenching titration. Results show that, relative to the more polar acidic DOM-fractions, the hydrophobic neutral fraction exhibits a higher sorption ability to pyrene. Generally, the sorption of pyrene to the three hydrophobic fractions is strongly pH-dependent. The K DOC values of pyrene generally increase with decreasing pH levels, which is especially obvious in the sorption of pyrene to the fulvic acid fractions, suggesting that the binding is controlled by hydrophobic interactions. The mechanisms underlying the binding of pyrene to the hydrophobic fractions were also discussed. Our data are beneficial to further understanding the binding of HOCs to DOM and how it has been affected, which may result in more accurate predictions of K DOC.  相似文献   

16.
The quantity and quality of dissolved organic matters have been widely characterized by fluorescence spectroscopy, yet the relationship between the fluorescence properties of dissolved organic matters and its molecular composition remains poorly described in the literature. Here, we measured the fluorescence excitation–emission matrix of 17 well-characterized humic substance standards to determine a range of fluorescence parameters, including classical fluorescence indices (e.g., fluorescence index, biological index and humification index) and parameters derived from parallel factor analysis (e.g., component contribution). Relationships between humic substance’s fluorescence and compositional parameters were then statistically examined using canonical correspondence and simple correlation analyses. The canonical correspondence analysis generally suggested that most fluorescence parameters determined here are highly associated with the amount of aliphatic and aromatic compounds in humic substances. However, the correlation analysis between single molecular and fluorescence parameters indicated that the fluorescence properties of humic substances including the parallel factor analysis component contribution also significantly correlate well with several aspects of the molecular composition of humic substances, such as elemental composition, carbon species, acidic functional group and iron complexation. Overall, our results suggest that measurement of humic substance’s fluorescence is beneficial in understanding the molecular composition and environmental functions of dissolved organic matters in natural and engineered waters.  相似文献   

17.
The fluorescent properties of dissolved organic matter (DOM) have been used as natural tracers in various water systems. However, only few studies have focused on groundwater systems, specifically, on karst systems. The aim of this study was to develop the use of the DOM fluorescence signal as a natural tracer, considering the multiple compartments of a karst system. This method was applied to the Lez hydrosystem, which supplies the city of Montpellier with drinking water. The hydrodynamics and hydrochemistry of the spring were monitored beginning March 2006. The DOM fluorescence was measured by the excitation–emission matrix spectroscopy technique. The analysis of the total fluorescence signal confirms the efficiency of this tool to trace rapid infiltration flows. Moreover, the decomposition of the signal into different fluorophores complements the information provided by the total signal. Indeed, the fluorescence emitted by the humic compounds seems to be the ideal tool for identifying rapid infiltration flows. Nevertheless, the fluorescence of protein-like compounds is better correlated with the inflow of faecal bacteria at the outlet. This decomposition of the fluorescence signal is an interesting way to provide information on both the rapid infiltration flow as well as the vulnerability of the karst aquifers.  相似文献   

18.
The complexation of Cu and Cd by ligands observed in filtered unfractionated lakewaters is compared to the complexation by humic and fulvic acids. Complexation parameters (conditional stability constants and ligand concentrations) of Suwannee River fulvic acids (FA), purified peat humic acids (HA) and of ligands in lakewater samples have been determined using the same methods (ligand-exchange and CSV (cathodic stripping voltammetry) or ASV (anodic stripping voltammetry)), and the same titration ranges of Cu, Cd and organic carbon concentrations. The performance of the used techniques is first evaluated in FA and HA suspensions, and gives comparable results with the literature values for the same materials, according to published models (5-site model, NICA model) and parameters. Model calculations using the WHAM model for FA and HA (Tipping, 1994) are also presented. The comparison of titrations of FA and HA with Cu and Cd with those of lakewater samples indicates that stronger ligands than FA and HA are present at low concentrations in the lakewaters. Specific strong ligands occur in particular in eutrophic lake waters, whereas in a lake with higher metal concentrations and low biological productivity the ligands more closely match the fulvic acid characteristics.  相似文献   

19.
洱海沉积物间隙水中溶解有机质的地球化学特性   总被引：11，自引：0，他引：11       下载免费PDF全文
对洱海沉积物间隙水中溶解有机质(DOM)含量、紫外可见吸收、荧光以及分子量等的垂直分布特征进行了研究。结果表明,DOC含量在沉积物水界面明显富集,随后急剧下降,6cm处达到最小值,随后呈上升趋势。DOC与吸光度值、荧光发射光谱强度之间具有一定的线性相关关系。DOM的E3/E4值范围在1～6之间,绝大多数在1～35之间。表征DOM中腐殖质来源的指标荧光指数值处于148～159之间,说明DOM以陆源输入为主。此外,洱海沉积物间隙水DOM分子量分布呈多峰分布模式,重均分子量(Mw)值在1462～1953Da之间,数均分子量(Mn)值在547～900Da之间,多分散性系数ρ值在202～305之间。随着沉积深度增大,Mw和Mn有略微的增大趋势,但变化不大。沉积物的氧化还原条件、微生物活动以及铁、锰氧化物等在沉积剖面的差异是控制间隙水中DOM各种地球化学特性的主要因素。  相似文献   

20.
激光诱导荧光(LIF)遥测是针对大面积水域富营养化状况进行原位、实时、快速测量的一种先进的监测技术。利用自行研制的水体污染LIF遥测系统对太湖水域进行了一次较为全面的测量,以测得的溶解有机物(DOM)荧光因子、瑞利散射因子和叶绿素a荧光因子分别代表各测量点的DOM浓度、浊度和叶绿素a浓度。同时以Skalar三维荧光成像仪测量各点DOM浓度,多参数水质分析仪测量浊度和叶绿素a浓度。对比分析了LIF遥测系统测量DOM荧光因子、瑞利散射因子和叶绿素a荧光因子与DOM浓度、浊度和叶绿素a浓度关系。结果表明LIF系统测得的DOM因子与三维荧光成像仪测量的DOM浓度值一致性较好(R=0.88733),而瑞利散射因子和叶绿素a荧光因子与多参数水质测量仪测得浊度值和叶绿素a浓度值线性相关性较差,相关系数分别为-0.39185和0.4552。对上述差异产生的可能原因进行了讨论,并阐述了LIF遥测技术在水质监测中的应用前景和潜在的应用限制。  相似文献   

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