共查询到20条相似文献，搜索用时 265 毫秒
1.
This paper deals with the influence of different humic substances (HS) on the enzyme activity (EA) of the proteolytic enzyme pronase E. The EA was determined by analyzing the concentration of the amino acid valine hydrolyzed from caseine. For amino acid analysis, a flourescence detector was used after precolumn derivatization and HPLC-separation of the hydrolysis products. The data show that the presence of HS has no adverse effects on amino acid analysis. Based on this result, a decrease of EA was observed in the presence of HS acting as enzyme inhibitors. Clear inhibition effects could be seen for different fulvic acids (HO3 FA, FBR FA and FBR 1.0 FA) at concentrations of 150 mg/L. In case of FBI-2 FA, higher concentrations were necessary to decrease the EA significantly. At an inhibitor concentration of 1500 mg/L the EA was mostly found to be less than 50%. The standard deviations of the results don't allow a differentiation between the HS of different origin and treatment. Specifying HS according to their influence on EA has to remain uncertain. As shown in a kinetic study of the hydrolysis of L-Leucine-2-naphthylamide-hydrochloride, the inhibitor HO3 FA decreases the maximum velocity of the reaction but has no effect on the Michaelis constant. These results indicate that this HS acts as a noncompetitive inhibitor. 相似文献
2.
Humic substances isolated from water, sediment, and soil were characterized by applying elemental analysis, spectroscopic analysis, and gelchromatographic molecular size distribution. In addition, the amounts and pattern of enzymatically released amino acids were determined. Depending on the origin of the humic substances, the percentage of released amino acid nitrogen related to the total nitrogen was in the range of 0.4 to 26.7%. The samples particularly differed in the content of leucine und tyrosine. The total amount of released amino acids was compared with the results obtained from the other characterization methods. This approach indicated that humic substances with a high content of hydrolysable amino acids had high N/C and O/C ratios and low molecular sizes. Beside this, the absorption of these substances in the UV and visible wavelength range was quite low, while the measured ratios of SAK(254)/SAK(436) showed high values. This work leads to the conclusion that the extent of enzymatically releasable amino acids is not only dependant on the nitrogen content of humic substances. Other physical and chemical properties have to be considered for the understanding of the results obtained by the described biochemical characterization method. 相似文献
3.
A phenoloxidase-producing fungus – Cladosporium cladosporioides – was isolated from water of a bog lake. At high concentrations of carbon (333 mM) and nitrogen (12 mM), the fungus demonstrated the formation of a laccase and a high ligninolytic activity. After addition of riverine or groundwater humic substances into culture media (ca. 1 mg mL–1), the fungus showed the ability of degrading (utilizing) of about 60% of these substances. However, the exact quantification of the degree of degradation was difficult because of adsorption of humic matter on fungal mycelium. Reisolated humic substances were lower in aromatic and higher in aliphatic structures. A crude enzyme from the C. cladosporioides culture showed only low activity in decolorizing humic substances, whereas decolorization up to 50% was observed when using a laccase preparation from Polyporus versicolor, and especially in the presence of a redox mediator. 相似文献
4.
Sixteen samples of fulvic acids and XAD‐4 fractions of riverine, estuarine, coastal, and open ocean origin have been studied by emission and synchronous molecular fluorescence spectroscopy. Certain features of the molecular fluorescence are related to the nature, the content, and the origin of those aquatic humic substances (HS). Riverine HS appear several times richer in fluorophores than marine HS, which can be well observed by emission fluorescence spectroscopy. Synchronous‐scan spectra of fulvic acids and of XAD‐4 fractions from the aquatic environments studied, emphasized the quality differences of their fluorophores. These features are useful as tracers of humic substances related with their natural environment source or even with their anthropogenic origin. 相似文献
5.
Stefania Mazzuoli Steven Loiselle Vincent Hull Luca Bracchini Claudio Rossi 《洁净——土壤、空气、水》2003,31(6):461-468
The spatial and temporal distribution of humic substances in aquatic ecosystems can have important effects on ecosystem productivity, negatively impacting primary productivity while positively impacting secondary productivity. In the present investigation, a large shallow lake ecosystem was studied to determine the spatial and seasonal variation of the composition and concentration of humic substances. Concentrations of total dissolved organic matter, humic acid, and fulvic acid were found to display significant spatial distributions (1.3…13.5 mg/L, DOM; 0.1…5.4 mg/L, HA). The distribution is described by using mapping techniques and the analysis of the spatial distribution of the lake. An analysis of the seasonal variations also indicated the dependence of the occurrence of these compounds on meteorological and hydrological conditions. To identify the potential sources of these organic materials, an analysis was made of the ratio of humic and fulvic acid fractions and total DOM. It was found that areas of high DOM concentration coincided with the areas of highest HA percentage of total DOM. Furthermore using the ratio of the normalised concentrations of HA, FA, and residual DOM (< 5000 g/mol) it was found that areas dominated by each are spatially distinct. This confirms the hypothesis that in these shallow lakes, photodegradation and bacterioplankton activity will create a residence time dependent zonation of each component of the total DOM. 相似文献
6.
Eduarda B. H. Santos Olga M. S. Filipe Regina M. B. O. Duarte Helena Pinto Armando C. Duarte 《洁净——土壤、空气、水》2001,28(7):364-371
Three‐dimensional fluorescence spectra of water samples from an eucalyptus bleached kraft pulp mill and from a river, upstream and downstream of the discharge of the effluent, revealed the existence of a peak at δexc = 280 nm and δem = 340 nm Δδ = 60 nm), characteristic of effluentπs organic matter. Humic substances were isolated from the effluent by sequential adsorption onto resins XAD‐8 and XAD‐4 in series. Their synchronous fluorescence spectra with Δδ = 60 nm do also exhibit an intense signal at δexc = 280 nm (≈ 300 nm in the humic acid fraction). The peak is absent in the spectra of humic substances isolated from a non‐polluted site of the river, but it is clearly seen in the spectra of the humic substances from a site downstream of the discharge of the effluent. Synchronous fluorescence spectra (Δδ = 60 nm) of water samples from the river and its lagoon were recorded and revealed to be an easy and fast way of tracing the organic contamination from the effluent. 相似文献
7.
Influence of IHSS Standard and Reference Materials on Copper and Mercury Toxicity to Vibrio fischeri
The reduction in light emission of the marine bacterium Vibrio fischeri used in the standard Microtox® bioassay was measured for the metals copper and mercury. The concentration at which the light emission was reduced by 50% (EC50) was determined to be (3.43 ± 0.83) μmol/L for Cu2+ and (0.66 ± 0.01) μmol/L for Hg2+. The reduction of the toxicity of these metals by humic and fulvic acids were studied using IHSS Standard and Reference Materials. Copper toxicity was reduced 17...20% by the soil and peat fulvic acids and 9...20% by the aquatic fulvic acids. While there appeared to be little difference in the reduction of Cu toxicity by fulvic acids from soils, peats, or aquatic systems, Hg toxicity was reduced 3.6...7.3% by the soils and peats, while aquatic fulvic acids reduced Hg toxicity 14...16%. Soil fulvic acids appear to have significantly less capacity to reduce Hg toxicity than Cu toxicity. Humic acids had much higher reductions of Cu toxicity (44...124%) compared to the fulvic acids, with little difference between aquatic and soil or peat humic acids, 44...124% and 67...100%, respectively. However, humic and fulvic acids, regardless of origin, had approximately the same effect on Hg toxicity with 3.5...16% reduction by fulvic acids and 8...20% reduction by humic acids. Unlike the fulvic acids, no clear trend was observed relative to origin of the humic acids. There was no correlation between percent reduction of Cu or Hg toxicity by the organic compounds and copper binding capacity (CuBC), C/N ratio, or carboxyl content of the materials. Examination of natural organic matter (NOM) isolated by reverse osmosis techniques from three water sources had reductions of both Cu and Hg toxicity that were most similar to the Suwannee River and Nordic fulvic acids. 相似文献
8.
After an explanation of the complex composition of the system of humic substances, some gravel deposits are described from whose open-pit boundaries there were taken water samples, their content of components of humic matter having been determined. Since spectroscopic analysis techniques yield spectra which are difficult to analyse and have a relatively low detection sensitivity, an indirect polarographic method was applied by which water-soluble humic substances can be determined very selectively down to a lower limit of 5 μg/1. Thus, enrichment in water or in adsorbing columns is not required. From the results found there are derived several statements concerning the occurrence of humic substances and fulvic acids in waters and conclusions about the possible influence on the hardening of concrete are given. 相似文献
9.
John D. Coates Romy Chakraborty Susan M. O&#x;Connor Claudia Schmidt Jürgen Thieme 《洁净——土壤、空气、水》2001,28(7):420-427
As part of a study on microbial redox alteration of humic substances we investigated the potential effect of this metabolism on the fate of heavy metals and hydrocarbons as a result of conformational alteration of the humic molecular structure due to microbial reduction. Our studies indicate that the microbial reduction of humic acids (HA) results in significant morphological and geochemical alterations. X‐ray microscopy analysis indicate that the conformational structure of the humic colloids is altered as a result of the redox change. In the reduced state, the HA appeared as small dense particles, on reoxidation, large loose aggregates were formed. In addition, spectrofluorometric studies indicated that the binding capacity of the HA for naphthalene was decreased by 10% when the HA was reduced. Similarly, the reduced HA yielded higher surface tension values at all concentrations tested which is indicative of a more hydrophilic and less hydrophobic solute. On reoxidation, the surface tension values reverted back to values similar to those obtained for the untreated oxidized HA. These data indicate that the hydrophobicity of the HA is altered on biological reduction of the HA and that this alteration is reversible. In contrast the reduced HA demonstrated a 15% higher affinity for heavy metals such as divalent cobalt than the oxidized HA. In addition to increasing the binding capacity of HA for heavy metals, the reduction of the HA also decreased the bioavailability and toxicity of bound heavy metals such as chromium. When incubated in the presence of Cr(III) and HA, cells of Escherichia coli grew much more rapidly in the presence of the reduced HA suggesting that the higher metal binding capacity of the reduced humic substances resulted in a removal of the Cr(III) from solution and hence reduced its bioavailability and toxicity. These studies demonstrate that HA redox state and reduction of humic acids by microorganisms can have a significant effect on the molecular morphology and binding constants of HA for heavy metals and hydrocarbons and also directly affects the bioavailability of these compounds in the environment. 相似文献
10.
乌梁素海沉积物腐殖质的组成及分布特征 总被引：4，自引：2，他引：2
以乌梁素海为研究对象,应用化学方法对乌梁素海湖泊表层沉积物有机质含量、腐殖质组成、影响腐殖质的环境因子及腐殖化程度进行了研究,结果表明:乌梁素海表层沉积物有机质含量变化范围为1.06%~5.38%.有机质分布特征与表层沉积物所处的水力条件、水生植物分布、人为活动有关;腐殖质组成中,胡敏酸含量为0.65~2.78 g/kg,富里酸含量为2.19~8.72 g/kg,胡敏素是主体,含量在3.28~20.92 g/kg之间;腐殖质与环境因子的相关性分析中,各组分含量与有机质含量呈极显著相关.pH值与胡敏素含量呈显著负相关.溶解氧与富里酸、胡敏素含量分别呈极显著正相关、显著正相关.腐殖化程度分析中,随着有机质含量的上升,可提取腐殖质的相对含量下降.PQ值介于9.50%~27.06%之间,平均值为21.47%,变异较大,且腐殖化程度较低. 相似文献
11.
Ostrich eggshell is a favoured substrate for amino acid geochronology, yielding consistent results and thought to approximate a closed system with respect to protein diagenesis. We found that the intra-crystalline fraction in ostrich eggshell is more challenging to isolate than that from mollusc shells, requiring 72 h oxidative treatment with NaOCl, resulting in a loss of up to half of the whole-shell protein. Through high temperature studies we have shown that under continuous leaching conditions approximately 99% of the intra-crystalline amino acids are resistant to leaching. Furthermore, high temperature experiments of the intra-crystalline proteins at pH 5, 7 and 9 have shown that this fraction is unaffected by pH changes over this range. This study confirms that the intra-crystalline protein fraction in OES may approximate a closed system. The intra-crystalline amino acids have been shown to follow predictable patterns of hydrolysis and racemization for all amino acids studied. Most amino acids showed some conformity to pseudo reversible first order reaction kinetics for racemization over limited D/L ranges, but hydrolysis was generally described poorly by first order kinetics. We therefore tried a new scaling method to determine relative reaction rates, estimated by applying scaling factors to overlap the observed rates of racemization (or hydrolysis) at the different temperatures, with the advantage of not forcing a linear relationship with respect to time. Using apparent first order kinetics, constrained power functions and scaling methods, we estimated the Arrhenius parameters (activation energy, EA and frequency factors, A) for both hydrolysis and racemization. The different methods for the estimation of reaction rates can give significantly different, but equally plausible, activation energies. This study reinforces previous work that indicates we need to understand the underlying mechanisms in order to estimate accurate kinetic parameters. 相似文献
12.
Microbial biodegradation of organic substances takes place during drinking water treatment, but also in the distribution net, if the drinking water still contains biodegradable organic substances. This phenomenon is called regrowth. The regrowth potential of a drinking water is high, when for instance ozonation is used as the last step of treatment. It was proved before, that ozonation increases the biodegradability of humic substances, which are the main fraction of organic carbon in drinking water. In this work the objective was to check, if chlorination has a similar effect on humic substances. Using the method developed by Werner of measuring the regrowth potential of a water it could be shown by dilution series with chlorinated and unchlorinated humic substances that the substrate quality of these organics is increased by chlorination. The better substrate quality is seen in the chlorinated solutions, which might contain also low molecular weight organic compounds, but also in the fulvic acid fraction after XAD-enrichment, which removes most of the low molecular weight organic compounds. The chlorination creates in the fulvic acid solutions a shift of molecular size to smaller molecules and higher polar substances, which might be the reasons for the better biodegradability. From these results it can be concluded, that chlorination produces substances, which are more easily biodegradable. But this will not produce regrowth problems as long as there is free chlorine present as a disinfectant. In contrast, when the chlorine demand is very high and no free chlorine is left, this might produce high colony counts in the distribution net. 相似文献
13.
Dissolved total carbohydrates (DTCH), dissolved free monosaccharides (DFMS), dissolved organic carbon (DOC), biodegradable DOC (BDOC), and humic substances (HS) were measured in White Clay Creek (WCC), a stream in southeastern Pennsylvania Piedmont, USA. Samples were collected over different seasons and under baseflow and stormflow conditions. DOC concentrations ranged from 1.0 to 12.8 mg/L C with the highest concentrations associated with stormflows. Carbohydrates ranged from 0.42 to 12.4 μM and accounted for 2.9 to 12.7% of the DOC. Humic substances represented the major DOC fraction, accounting for 55 to 72% of the DOC pool under all flow conditions. The humic fraction had a lower carbohydrate content (4.4%) than the non-humic fraction of DOC (7.2%). Stormflow DOC was enriched in carbohydrates relative to baseflow DOC, but the percentage of humic-C changed little. Carbohydrates were primarily present as dissolved polysaccharides (55%), but a significant fraction was bound to humic substances (40%), while a small proportion was present as monosaccharides (5%). The major monosaccharides in stream water, listed in order of decreasing concentration, included glucose, galactose, rhamnose, xylose, arabinose, mannose, and fucose. On average (30.6 ± 7.4)% (n = 44) of the stream water DOC was biodegradable, and carbohydrates accounted for 9.9 to 17.7% of the BDOC. 相似文献
14.
15.
Experiments were conducted to study the microbial co-oxidation of naturally structured humic substances in different water bodies at different glucose concentrations. At low buffer capacity of aquatic ecosystems, the initial stages of the process are shown to be accompanied by a considerable increase in the medium acidity, a decrease in its alkalinity, and accumulation of colored intermediate products of bacterial and enzymatic synthesis. It is found that the co-metabolism processes with highly labile compounds either do not play any significant role in the trophodynamics of aquatic ecosystems (<10% of the original humic material is co-oxidized) or are not detected, notwithstanding the sufficient sensitivity of the analytical techniques involved. The low degree of co-oxidation (or its virtual absence) are found to be attributable to the masking effect of intermediate products. 相似文献
16.
Humic material isolated from six Himalayan lakes was investigated for its elemental composition, exchange behaviour and spectrophotometric properties. The carbon content was 36.8… 56.6 %. The C: H ratio was lower than for soil humic acids. The nitrogen content was 3.8… 5.8 % and was higher than reported for soil humic acids. Zinc and copper were higher at the sites with high pollution load. On a strong cation exchanger copper showed the highest stability and calcium was least stable. The Δ log K values suggested that comparatively deep water sediments show lower degrees of humification. 相似文献
17.
In natural waters arsenic concentrations up to a few milligrams per litre were measured. The natural content of arsenic found in soils varies between 0.01 mg/kg and a few hundred milligrams per kilogram. Anthropogenic sources of arsenic in the environment are the smelting of ores, the burning of coal, and the use of arsenic compounds in many products and production processes in the past. A lot of arsenic compounds are toxic and cause acute and chronic poisoning. In aqueous environment the inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are the most abundant species. The mobility of these species is influenced by the pH value, the redox potential, and the presence of adsorbents such as oxides and hydroxides of Fe(III), Al(III), Mn(III/IV), humic substances, and clay minerals. 相似文献
18.
Membrane-filtration or dialysis techniques are increasingly used for the partial desalting of waters, e.g. brackish waters. By the use of Bulgarian PAN and acetate-cellulose separating membranes there are eliminated also organic substances – inclusive of humic matter – from natural waters to different degrees. The experimental arrangement is described and the measured results for COD-Mn, concentrations of humic acid and specific electrolytic conductivity are summarized in tables. The humic acid concentration (2.8 mg/l) was reduced by about 79 % by ultrafiltration, 82 % by reverse osmosis and 62 % by electrodialysis. The efficiency of the investigated techniques could be increased under certain conditions. 相似文献
19.
On the basis of an analysis of literature and of own investigations, the state of metalions in natural waters is described as essential for the properties. There are investigated especially: hydrolysis, polymerization and complexation with humic substances. An analytical method for determining the degree of dispersion and the shares of free and complexed metal-ions as well as their charge and molar mass is presented. 相似文献
20.
A Specord M 40 device with the Date Handling 1 computer cassette was used for the derivative-spectroscopie determination of lignosulphonic acid. Because of the higher sensitivity and the better evaluable peaks, the 2nd derivation of the five possible derivations was used. The analysis method described in detail was tested with test substances on a surface water which was polluted with waste-products from the pulp industry. With the stated device parameters, the lignosulphonic acid up to 2 mg/l can be determined in the presence of humic acids and chlorolignosulphonic acids. In weakly polluted waters, as groundwaters and shore filtrates. still lignosulphonic acid concentrations of 0.1 mg/l can be detected after an adequate enrichment. 相似文献