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1.
The by-products of humic substances (HS), resorcinol, orcinol, phloroglucinol, pyrogallol, 3,4- and 3,5-dihydroxybenzoic acids, and ortho- and meta-phthalic acids, have been tested for antithyroid and goitrogenic activities. By two in vitro assays all compounds, except the phthalic acids, were potent inhibitors of the thyroid peroxidase enzyme, and of thyroidal 125I uptake and/or its incorporation into thyroid hormones using thyroid slices. Resorcinol in drinking water was goitrogenic as indicated by in vivo assay in rats. These findings, the identification of resorcinol in the water supply of an endemic goiter district in western Colombia, where increased goiter prevalence is associated with watersheds rich in organic matter, and results of elemental analysis of goitrogenic water extracts from the same district showing a composition similar to that of aquatic HS, suggest that HS degradation by-products may play an important role in the etiology of endemic goiter.  相似文献   

2.
A quantitative 13C-NMR technique was applied to humic acids, isolated from total solvent extracts obtained from coals, varying in rank from lignite to medium volatile bituminous. The results from elemental analysis and 13C-NMR structural ratios are interpreted in the form of three distinct structural phases in the maturation of coal humic acids. These phases reflect the rank of the parent coals. A decrease in polar functional group content and corresponding increase in aromaticity is observed with increasing maturation of humic acid chemical structure. Limits are postulated for the oxygen content and level of aromaticity for humic acids derived from higher rank coals.  相似文献   

3.
CPMAS 13C NMR spectra of two estuarine sedimentary humic acids were recorded on a Bruker WP-SY 200 spectrometer. Both samples were found to contain similar aromatic and aliphatic carbon fractions. The sedimentary humic acids have unusually high methoxyl contents and more than one type of methoxyl is indicated. The high methoxyl content may be related to relatively low values for estuarine sedimentary humic acid-metal complexes. Carbohydrate contents of the humic acid samples were also found to be low.  相似文献   

4.
Four humic extracts isolated from terrestrial, mahne, plankton and freshwater sources have been investigated by pyrolysis-gas chromatography-mass spectrometry. The results show that substantial quantities of phenols (some not derived from lignin), pyrroles and nitrites (derived from proteins, nucleic acids or porphyrins) are decomposition products. Small amounts of furans (derived from carbohydrates) and unsaturated ketones (derived from polycarboxylic aliphatic acids) are also present. The results illustrate how parent material, transport factors and biological activity affect the composition of humic extracts.  相似文献   

5.
Humic acids were isolated from 5 sediments in which the origin nature of the organic matter are both typical and different. The humic acids were characterized on the basis of elemental compositions, infrared spectra and 1H and 13C NMR. This last technique, especially 13C NMR, provides qualitative and semi-quantitative information regarding aromatic structure. Combined data from the three techniques permits differentiation of marine and terrestrial organic matter as well as identification of mixtures of humic acids from the two sources.  相似文献   

6.
A South Australian Tertiary brown coal is fractionated into humic acid and kerogen fractions. These related samples are then subjected to a number of different analytical techniques including infrared and13C-Nuclear Magnetic Resonance spectroscopies and pertrifluoroacetic acid oxidation. Structural conclusions are drawn from an integrated consideration of the data. Brown coal aliphatic structure is concentrated in the kerogen and the solvent soluble polar acid fractions. The humic acids are the most aromatic and contain a high degree of hydrogen bonding. Only very minor amounts of long polymethylene chain structures are observed in the humic acids, in complete contrast to the kerogen fraction. Different organic detrital origins are proposed for the coal fractions.  相似文献   

7.
13C and 1H NMR spectra were obtained for humic acids isolated from marine sediments. NMR shows great promise in identifying structural components of humic acids as some new and interesting structural features are identified. Aliphatic structures were found to constitute a much larger fraction of humic acids than previously thought, and they appeared to be highly branched. Although the aromatic content of terrestrial humic acid was found to be lower than expected, the aromaticity appears to be a specific discriminator of terrestrial/aquatic source types. A humic acid isolated from an anoxic algal sapropel was found to be composed predominantly of polyuronic acids and different than other aquatic sedimentary humic substances.  相似文献   

8.
Fatty acids and isoprenoid alcohols were analyzed in river, estuarine, and coastal sediment cores: (1) to investigate the distribution of these lipids among the unbound phase. those bound or closely associated with humic substances, and those bound or closely associated with the huminkerogen and clay mineral matrix. (2) to investigate the diagenetic changes of these lipids with depth in the sediments. and (3) to obtain information on the use of these compounds as organic tracers in marine sediments.Results confirm earlier observations that fatty acids are rapidly altered in marine sediments Both the total and the individual fatty acids decrease in concentration with depth in the sediments: unsaturated acids decrease faster than saturated acids and unbound acids decrease faster than bound acids Approximately 8–62% of the fatty acids were unbound. 2–22% were associated with humic substances. and 38–86% were associated with the residual organic-mineral matrix. Qualitative differences also exist between the fatty acids associated with the unbound, humic, and residual fractions. The ratio of trans/cis geometric isomers of the fatty acids generally increases downcore. with no rearrangement of the double bond positions within the molecules. Either the cis isomer is being preferentially degraded with depth in the sediments, or there is a low temperature, clay catalyzed conversion of the cis isomers to the trans isomers occurring down the cores.Phytol was the major alcohol present in the sediments and does not appear to be altered as rapidly as the fatty acids. Less than 10% of the total phytol (PHY) plus dihydrophytol (DHP) was present as DHP and no trend could be discerned between PHY and DHP with depth or with unbound, humic, and residual material in the cores. All of the isolated DHP appeared to be present as the RRR stereoisomer. Along with the absence of phytane in the cores, this observation suggests that the reduction of phytol to dihydrophytol is microbially mediated in the upper layer of the sediment.  相似文献   

9.
The structure of dissolved marine humic material and the intracellular and extracellular material from the diatom Phacodactylum tricornutum has been investigated by 1H- and 13C-NMR spectroscopy. The results show that carbohydrates, highly-branched alkyl chains and to a lesser extent aromatic materials are important contributors to the structure of marine humic substances and aqueous extracts of P. tricornutum. There is a close relationship between the chemical structure of P. tricornutum exudate and dissolved marine humic material.  相似文献   

10.
Particulate matter was collected during September–October, 1977, in particle traps suspended 30–60 m above the floor of San Nicolas, Santa Barbara, Santa Monica and San Pedro Basins, off the coast of southern California. The trap particulates were analyzed for C15–C35 hydrocarbons using gas chromatography (GC) and GC-mass spectrometry. Kerogens and humic acids were characterized by H/C, N/C, δ13C, δ15N and δ34S ratios, and by electron-spin resonance. Hydrocarbons arising from fresh and weathered petroleum, marine autochthonous and terrestrial sources were identified. The rates of petroleum deposition during the collection period followed the order: San Nicolas Basin < Santa Barbara Basin ~ Santa Monica Basin < San Pedro Basin, with the largest amount of weathered petroleum being deposited in San Pedro Basin. The rates of petroleum deposition are correlated more strongly with human activities such as shipping, and the discharge of municipal and industrial wastes, than with natural submarine oil seepage. Analyses of kerogens and humic acids indicate that the majority of the organic matter in the trap particulates is of marine origin. The water column overlying Santa Barbara Basin appears to have the highest marine productivity of the four basins studied.  相似文献   

11.
The experimental conditions allowing quantitative interpretation of liquid state 13C-NMR spectra of the humic acids, derived from the five Victorian brown coal lithotypes are described. The structure of the two classes of humic acids investigated for each lithotype vary significantly in their level of aromaticity, the level of polar functional groups and aliphatic chains attached to their polyaromatic skeletons. Variation is also observed in the degree of aromaticity and oxygen-containing functions of humic acids with lithotype. These data are interpreted in the light of paleobotanical evidence, which suggests that the lithotypes represent variations in depositional environment and input to the coal seam.  相似文献   

12.
Algal humic-like substances were oxidized with KMnO4. The oxidation products were analyzed by GC-MS. Normal and branched fatty acids, dicarboxylic and benzene carboxylic acids were identified. Aliphatic acids were by far the most prominent compounds. Similarities between humic and fulvic acids of both Fucus and Laminaria algae were apparent. Fucus humic acids, however, showed a more aromatic structure than their Laminaria counterpart. The contribution of algae to marine sedimentary humus is discussed.  相似文献   

13.
Aqueous solutions of increasing pH (7.0, 10.6 and 12.6) were used to extract exhaustively the organic matter (OM) from a pelo-stagnogley (heavy clay) soil in long term cultivation. OM yield was 1.7 times greater when the extracts were processed using an XAD-8 and XAD-4 resin-in-tandem procedure than that from the procedure of the International Humic Substances Society (IHSS). The substantial difference can be attributed to the amount retained by the XAD-4 resin, which is lost in the IHSS process. Elemental, δ13C, δ15N, cation exchange capacity, neutral sugars, amino acids and solid state CPMAS 13C NMR analyses indicated significant, but rational similarities and differences between the various fractions isolated. There was strong NMR evidence for material derived from lignin in all the humic and fulvic acid isolates. The signals were attenuated in the more transformed/oxidized fractions isolated at lower pH. Novel humic acid fractions enriched in carbohydrate/peptide functionalities were isolated from the more hydrophobic extracts at pH 10.6 and 12.6. Isolates from XAD-4, of microbial origin, were enriched in neutral sugars but not in amino acids, and had minimal aromaticity. Components isolated from the cultivated soil were broadly similar to those from a comparable soil in long term grassland. The compositions of fractions isolated from the drainage water were similar to those extracted from the soil but had higher carboxyl content. The amount and composition of the various organic fractions in grassland and the continuously cropped soil are discussed in terms of their potential to contribute to carbon sequestration by soil under similar management regimes.  相似文献   

14.
Thermogravimetric technique was used for the characterization of natural (humic) and synthetic (melanoidins) substances. The influence of pH on the thermal stability of humic substances was studied. A similarity in thermal behaviour of natural humic substances and of melanoidins (prepared from an excess of sugar) and the unique thermal properties of melanoidins (prepared from basic amino acids) was observed. Thermal behavior of natural and synthetic substances was compared with model compounds of sugar, peptide and kerogen types.  相似文献   

15.
The aim of this work is to study the structural changes involved in humification processes. Total humic extracts (THE) obtained from five composted materials of diverse origin (solid wastes of wineries, solid mill olive wastes, domestic wastes, ovine manures plus straw, and a mixture of animal manures), and their corresponding initial raw fresh organic mixtures were studied using 13C nuclear magnetic resonance (NMR) using the cross-polarization magic angle spinning technique (CPMAS), 1H NMR, Fourier transform infrared spectroscopy (FTIR) and high pressure size exclusion chromatography (HPSEC). One group of three humic acids extracted from soils, and a second group consisting of two reference humic acids and two reference fulvic acids (1S104H, 1R103H, 1R101F and 1R107F) obtained from the International Humic Substances Society were also characterized using these techniques, in order to compare the features of reference humic and fulvic acids with those of composted materials. Likewise, the results were compared with those obtained in previous studies, in which UV–Visible and fluorescence spectroscopies were employed to characterize the humification degree of the molecular systems.The results obtained by 13C CPMAS NMR, 1H NMR and FTIR indicate that, in general, humification seems to be associated with an increase in the aromatic character of the systems, with the presence of phenol groups as principal substituents and a reduction in oxygen containing functional groups, principally carboxylic or carbonylic groups, as well as the development of molecular fractions with larger size. These results also support the suitability of UV–Visible and fluorescence spectroscopies in the assessment of the humification course of humic extracts in composting processes.  相似文献   

16.
Analysis of river, estuary and marine sediments from the Atlantic coast of Spain using thermogravimetry–differential scanning calorimetry–quadrupole mass spectrometry–isotope ratio mass spectrometry (TG–DSC–QMS–IRMS) was used to (a) distinguish bulk chemical hosts for C within a sediment and humic acid fraction, (b) track C pools with differing natural C isotope ratios and (c) observe variation with distance from the coast. This is the first application of such a novel method to the characterisation of organic matter from marine sediments and their corresponding humic acid fractions. Using thermal analysis, a labile, a recalcitrant and a refractory carbon pool can be distinguished. Extracted humic fractions are mainly of recalcitrant nature. The proportion of refractory carbon is greatest in marine sediments and humic acid fractions. Quadrupole mass spectrometry confirmed that the greatest proportion of m/z 44 (CO2) and m/z 18 (H2O) were detected at temperatures associated with recalcitrant carbon (510–540 °C). Isotope analysis detected progressive enrichment in δ13C for the sediment samples with an increase in marine influence. Isotopic heterogeneity in the refractory organic matter in marine sediments could be due to products of anthropogenic origin or natural combustion products. Isotope homogeneity of humic acids confirms the presence of terrigenous C in marine sediments, allowing the terrestrial input to be characterised.  相似文献   

17.
Humic substances were isolated from ocean, estuarine water and fresh water using a two column array of XAD-8 and XAD-4 resins in series. The extracted fulvic acids and XAD-4 fraction from different origins were characterized using UV–vis., molecular fluorescence, Fourier transform infrared (FTIR) spectroscopy and cross polarization magic angle spinning (CPMAS)-13C nuclear magnetic resonance (NMR) spectroscopy. The isolation procedure allowed us to obtain the necessary amount of sample for characterization, even in the case of open ocean water, which has a very low amount of dissolved organic carbon (DOC). Humic substances from the open ocean showed the lowest chromophore and fluorophore contents and showed relatively greater fluorescence at lower wavelengths than those from fresh water. FTIR and 13C NMR spectra highlighted the idea that humic substances from a marine environment have a more branched aliphatic structure and less aromatic structure than those highly influenced by terrestrial sources. The spectra also suggest that the open ocean humic substances have a higher content of olefinic carbons than aromatic- or alkyl-substituted carbons.  相似文献   

18.
Humic acids and fulvic acids were extracted from six paleosols in Southern Italy. Humic acids (HAs) constituted between 96.5 and 99.2% of the total extracts; the remaining materials consisted of fulvic acids (FAs). Radiocarbon ages of the HAs ranged from about 6,000 to close to 29,000 years B.P., δ13C values averaged ?25.6 ± 0.3‰ The HAs were characterized by chemical (elemental and functional group analyses) and spectroscopic (IR, ESR, 13CNMR, E4/E6 ratios) methods. FAs were characterized by chemical methods, E4/E6 ratios and IR spectra.The chemical and spectroscopic analyses showed practically no differences in the chemical structure and composition of the six HAs and FAs, so that age appeared to have little effect on these parameters. The paleosols were found to be closed systems with low polysaccharide and protein contents, thus providing unfavorable substrates for microbial activity. The preservation of the humic materials in the paleosols may have been due to low biological activity and/or to retention by amorphous minerals. The HAs did not appear to be affected by temperatures higher than 170–200°C over the 23,000 year period which we observed.  相似文献   

19.
Aquatic humic substances can be removed by chemical coagulation during water treatment. Hydrolyzing metals such as Al(III) and Fe(III), as well as commercially available cationic polyelectrolytes, can effectively remove humic substances prior to chlorination, thus reducing the formation of trihalomethanes. Synthetic waters, produced by adding soil-extracted fulvic acids to distilled water containing a clay source and various salts, have some merit in approximating the behavior of aquatic humic substances during chemical coagulation; however, caution must be exercised in the interpretation and applicability of the results.  相似文献   

20.
1H NMR spectra of humic (HA) and fulvic (FA) acids and their oxidative degradation products are reported. The HA shows the presence of -(CH2)n - CH3 (n > 6) chemical fragments belonging to n-alkanes and/or n-fatty acids physically adsorbed onto the macromolecule structure. These fragments are absent in the FA fraction. Both humic fractions reveal the presence of similar amounts of aromatic protons which partly undergo exchange phenomena. The importance of this experimental observation is discussed. Oxidative degradation seems to cause partial cleavage of aromatic rings, more pronounced in the FA than in the HA. The degraded FA shows a higher total acidity and a higher phenolic OH content than the degraded HA. Both degraded fractions display some sharp singlet signals at 1.9 and 3.9 ppm arising from protons belonging to repetitive chemical fragments probably formed during the oxidation reaction. Tentative assignments of these signals are given. A general analysis of the HA and FA degraded spectra seems to indicate that the chemical fragments which undergo peracetic oxidation are substantially similar. The extent of oxidation of the two humic fractions is different. The HA degradation products reveal the presence of oligomeric structures, whereas the degraded FA appears less resistant to the oxidizing agent.  相似文献   

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