Isolation and biological activity of the pigments of the mold Epicoccum nigrum.
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Anti-Bacterial Agents↗
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Results for “Humic Substances”
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Interaction of reactive and inert chemicals in the presence of oxidoreductases: reaction of the herbicide bentazon and its metabolites with humic monomers.
The herbicide bentazon (3-isopropyl-1H-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide), a relatively inert chemical, and some of its metabolites were incubated with a laccase or a peroxidase in the presence or absence of humic monomers to evaluate the incorporation of the herbicide and its metabolites into humic material by oxidative enzymes. Guaiacol and ferulic acid were used as representative electron donor co-substrates in most of the oxidative coupling reactions. Bentazon and its metabolites, with the exception of hydroxy metabolites, underwent little or no transformation by the two enzymes in the absence of guaiacol and ferulic acid, but in the presence of these co-substrates transformation occurred. The reaction of bentazon with guaiacol in the presence of the laccase or a peroxidase was almost complete in 30 min. 6-Hydroxy- and 8-hydroxy-bentazon were completely transformed by each enzyme both with and without co-substrates. At pH 3.0 and in the presence of laccase and guaiacol, the concentrations of bentazon and its metabolites 2-amino-N-isopropyl-benzamide (AIBA), des-isopropyl-bentazon and 8-chloro-bentazon decreased by 27, 57, 20 and 4%, respectively. The corresponding levels of transformation with peroxidase at pH 3.0 were 9, 70, 30 and 5%, respectively. The extent of transformation decreased with increasing pH. At low pH, the hydroxy-bentazons were completely transformed, followed by (in order of percentage transformation) AIBA, des-isopropyl-bentazon, bentazon and 8-chloro-bentazon. Transformation of bentazon by the laccase increased with increasing guaiacol concentration. In the presence of the peroxidase, the most effective co-substrates for transformation of bentazon were (in decreasing order) catechol, vanillic acid, protocatechuic acid, syringaldehyde and caffeic acid, while in the presence of the laccase, catechol was most effective, followed by caffeic acid, protocatechuic acid and syringaldehyde.
Benzothiadiazines↗
Humic acids of low peat and brown coal.
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Coal↗
Selective enrichment of Geobacter sulfurreducens from anaerobic granular sludge with quinones as terminal electron acceptors.
A quinone-respiring, enrichment culture derived from methanogenic granular sludge was phylogenetically characterized by using a combined cloning-denaturing gradient gel electrophoresis (DGGE) method, which revealed that the consortium developed was dominated by a single microorganism: 97% related, in a sequence of 1520 base pairs, to Geobacter sulfurreducens. The enrichment culture could grow with acetate, formate or H2 when humic acids, the humic model compound, anthraquinone-2,6-disulfonate (AQDS), or chelated Fe(III) was provided as a terminal electron acceptor. The occurrence of a humic acid- or quinone-respiring microorganism in the microbial community of a wastewater treatment system suggests that this type of microorganisms may play a potential role in anaerobic bioreactors treating humus-containing wastewaters.
Acetates↗
Chemical and structural evolution of humic acids during organic waste composting.
The effects of the composting process on the chemical and structural properties of humic acids have been studied in seven different organic waste mixtures from different origin. Only slight changes in elemental composition have been found in the humic acids after the composting process pointing to a more aromatic structure with higher proportions of oxygen and nitrogen. Functional groups were the most sensitive to the changes caused by the composting process showing a marked increase in the total acidity and phenolic, carboxyl and carbonyl groups. Gel permeation chromatography showed a slight increase in the average molecular weight of the humic acids. Infrared spectroscopy did not show important differences in humic acid structure but a clear decrease in the intensity of the bands in the region 3000-2850 cm(-1) corresponding to the aliphatic fractions. As a general result, the composting process yields humic acids in which the elemental and functional composition are closer to that of the more humified soil humic acids.
Biodegradation, Environmental↗
Impact of emission from oil shale fueled power plants on the growth and foliar elemental concentrations of Scots pine in Estonia.
To study the impact of air pollution on the growth and elemental composition of conifers, 5 sample plots were established at different distances and directions from the Estonian Power Plant (Northeast Estonia) in 1999-2000. The selected stands were 75-80(85)-yr-old parts (0.05 ha) of (Oxalis)-Myrtillus site type forest of 0.7-0.8 density. The soils of all sample plots were Gleyic Podzols (Lkg) on sands. The several times higher Ca concentration in the humus horizon of the sample plot NE from the Estonian PP is caused by the prevailing westerly and southerly winds which carry more pollutants NE from the power plant than to SSW. To ascertain the effect of power plants on the growth of Scots pine (Pinus sylvestris L.), the length growth of the needles and shoots formed in 1997-2000, dry weight of 100 needles, and density of needles on the shoots were measured. As compared to the control, the strongest inhibition of growth was revealed in the sample plots situated 22 km north-east and 17 km south-west from the Estonian Power Plant. As compared to control, the needles of trees growing on sample plots closer to the power plant showed higher contents of Ca, S and Zn. The content of Mg in needles increased with distance from the pollution source. Current year needles had higher contents of Cu and Zn than older needles. Today the amounts of fly ash emitted from Narva power plants are fallen. Long-term fly ash emission has caused changes in the measurements of morphological parameters and chemical composition of needles.
Air Pollutants↗
An in vitro investigation of the anti-inflammatory properties of potassium humate.
In this study the anti-inflammatory potential of potassium humate, derived from bituminous coal, has been investigated in vitro. Exposure of resting and phorbol-12-myristate-13-acetate (PMA) stimulated human neutrophils to potassium humate resulted in a decreased expression of CR3 by activated, but not resting cells, in a dose-related way. Humate also inhibited the adhesion of PMA-stimulated neutrophils to a baby hamster kidney cell line expressing ICAM1 (the CR3 ligand) (BHK331-7). Similar results were obtained using normal BHK cells indicating that this inhibition does not only target specific adhesion molecules on the neutrophil and eosinophil membrane by activated phagocytes, but also affects other mechanisms involved in cell adhesion. Opsonised Sephadex or FMLP/Cyto B-induced degranulation of neutrophils and eosinophils were also decreased by humate treatment. Inhibition of the adhesion of activated phagocytes, as well as inhibition of the release of granule polypeptides, both of which are responsible for tissue damage during inflammatory processes, are attractive targets for anti-inflammatory drugs. Because humate is well tolerated with an excellent safety profile it merits further evaluation in patients suffering from inflammatory conditions.
Animals↗
Resistance of protein-lignin complexes, lignins and humic acids to microbial attack.
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Humic Substances↗
Photosensitized reduction of nitrogen dioxide on humic acid as a source of nitrous acid.
Nitrous acid is a significant photochemical precursor of the hydroxyl radical, the key oxidant in the degradation of most air pollutants in the troposphere. The sources of nitrous acid in the troposphere, however, are still poorly understood. Recent atmospheric measurements revealed a strongly enhanced formation of nitrous acid during daytime via unknown mechanisms. Here we expose humic acid films to nitrogen dioxide in an irradiated tubular gas flow reactor and find that reduction of nitrogen dioxide on light-activated humic acids is an important source of gaseous nitrous acid. Our findings indicate that soil and other surfaces containing humic acid exhibit an organic surface photochemistry that produces reductive surface species, which react selectively with nitrogen dioxide. The observed rate of nitrous acid formation could explain the recently observed high daytime concentrations of nitrous acid in the boundary layer, the photolysis of which accounts for up to 60 per cent of the integrated hydroxyl radical source strengths. We suggest that this photo-induced nitrous acid production on humic acid could have a potentially significant impact on the chemistry of the lowermost troposphere.
Atmosphere↗
Electron paramagnetic resonance evidence that copper is complexed in humic acid by the nitrogen of porphyrin groups.
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Copper↗
Assessment of disinfection by-products in drinking water in Korea.
The main purpose of applying the chlorination process during water treatment is for disinfection. Research results, however, indicate that disinfection byproducts (DBPs) including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs), and chloropicrin (CP) can be produced by the chlorination process. Some of these DBPs are known to be potential human carcinogens. This 3-year project is designed to establish a standard analysis procedure for DBPs in drinking water of this country and investigate the distribution and sources of specific DBPs. The occurrence level of DBPs in drinking water was below 50 micrograms/l in most cases. THMs in plant effluent accounted for 60% of all DBPs measured, whereas HAAs accounted for 20%, HANs 12%, HKs 5% and CP 3%. Chloroform was found to be the major THMs compound (77%), followed by bromodichloromethane (BDCM, 18%) and bromoform (BF, 3%). The concentration of DBPs formed in distribution systems increased from those detected in plant effluent. Comparison of humic acid and sewage as precursors for THMs formation showed that humic acid was the major THMs precursor. Results would play an important role in exposure assessment as a part of the risk assessment process, and would give basic information for establishment of DBPs reduction and management procedures.
Chlorine↗
Comparison of degradation state and stability of different humic acids by means of chemolysis with tetramethylammonium hydroxide.
In the chemolysis products of extracted humic acids (HAs) and tetramethylammonium hydroxide, different compounds can be identified which allow a description of the sources of soil organic matter (SOM). It is possible to draw conclusions concerning stability, degree of intramolecular cross-linking and degradation of aliphatic and lignin components from the distinctive product ratios. The ratio of lignin derived acidic phenolic derivatives and their analogous aldehydes and the ratio of phenylpropenoic acids and analogous benzoic acids provide comparably good parameters for the characterization of the state of degradation of lignin compounds to relatively stable HA building blocks. Regarding the aliphatic chemolysis products, alpha,omega-dicarboxylic acid and methoxy fatty acid contents indicate an intramolecular cross-linking state within the HA molecules and the degree of stable aliphatic constituent parts. High contents of unsaturated fatty acids can be considered as an indicator of an easy degradable humic skeleton because with their double bonds they represent active sites for further transformations. The suitability of the carbon preference index as an indicator of a biogenic carbon source can be confirmed. It is remarkable how the results obtained from extracted humic acids are in accordance with the expectations for the different SOMs derived from land use.
Fatty Acids↗
Applications of solid-phase microextraction (SPME) in the determination of residues of certain herbicides at trace levels in environmental samples.
A new analytical procedure based on solid-phase microextraction (SPME) has been developed for the determination of residues of eight selected herbicides: trifluralin, butachlor, pretilachlor, metolachlor, atrazine, acetochlor, alachlor, and fluroxypyr-meptyl, in ground water samples. Carbowax divinylbenzene was used for SPME of the herbicides. Quantification was done at equilibrium. Various parameters, such as, effect of pH, ionic strength, humic acid content and exposure time of fiber, were investigated to find the extraction efficiency. The linearity was determined. The method was found suitable for the determination of residues of herbicides at concentration levels from 5 to 20 ng L-1. The relative standard deviation of the detection limits were calculated. The humic acid content was found to interfere more significantly in the determination of residues. An ionic chloride strength, in terms of sodium chloride, of up to 10% did not have any significant impact on the determination. Furthermore, there was an enhanced sensitivity of detection up to pH 3.0. The method was applied to the analysis of the residue contents of the pesticides under investigation in real ground water samples collected from susceptible places. The results when compared with the standard methods published in the literature showed no significant deviation in their quantification and the values were comparable.
Chemistry Techniques, Analytical↗
Monochloramine loss in the presence of humic acid.
Free chlorine has been used extensively as a primary and secondary disinfectant for potable water. Where it is difficult to maintain a free chlorine residual or when disinfection by-products (DBPs) are of concern, monochloramine has been used to provide a stable disinfectant residual in distributions systems. Reactions of disinfectants, free chlorine or monochloramine, with natural organic matter (NOM) consequently result in the formation of DBPs such as trihalomethanes and haloacetic acids. However, few studies have focused on the fate and kinetics of monochloramine loss in the presence of reactive constituents such as NOM. Monochloramine is inherently unstable and decays even without reactive constituents present via a mechanism known as autodecomposition. Therefore, to predict monochloramine concentrations in the presence of NOM is clearly associated with the ability to adequately model autodecomposition. This study presents the results of a semi-mechanisiic model capable of predicting the loss of monochloramine in the presence of humic material in the pH range of 6.55-8.33. The model accounts for both fast and a slow monochloramine demand to explain the loss of monochloramine over the pH range of this study. The formation of dichloroacetic acid was also predicted due to the ability of the model to differentiate monochloramine reaction pathways in the presence NOM. The results shown here demonstrate the ability of a semi-mechanistic model to predict monochloramine residuals and DBP formation in the presence of humic material.
Chloramines↗
Preferential adsorption of fluorescing fulvic and humic acid components on activated carbon using flow field-flow fractionation analysis.
Activated carbon treatment of drinking water is used to remove natural organic matter (NOM) precursors that lead to the formation of disinfection byproducts. The innate hydrophobic nature and macromolecular size of NOM render it amenable to sorption by activated carbon. Batch equilibrium and minicolumn breakthrough adsorption studies were performed using granular activated carbon to treat NOM-contaminated water. Ultraviolet (UV) absorption spectroscopy and flow field-flow fractionation analysis using tandem diode-array and fluorescence detectors were used to monitor the activated carbon sorption of NOM. Using these techniques, it was possible to study activated carbon adsorption properties of UV absorbing, fluorescing and nonfluorescing, polyelectrolytic macromolecules fractionated from the total macromolecular and nonmacromolecular composition of NOM. Adsorption isotherms were constructed at pH 6 and pH 9. Data were described by the traditional and modified Freundlich models. Activated carbon capacity and adsorbability were compared among fractionated molecular subsets of fulvic and humic acids. Preferential adsorption (or adsorptive fractionation) of polyelectrolytic, fluorescing fulvic and humic macromolecules on activated carbon was observed. The significance of observing preferential adsorption on activated carbon of fluorescing macromolecular components relative to nonfluorescing components is that this phenomenon changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the composition that existed in the aqueous phase prior to adsorption. Likewise, it changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the adsorbed phase. This research increases our understanding of NOM interactions with activated carbon which may lead to improved methods of potable water production.
Adsorption↗
Quantifying the phenolic content of freshwaters using simple assays with different underlying reaction mechanisms.
Five different assays, Gibbs, Prussian Blue, Folin-Ciocalteau, fluorescence quenching of added phenol and precipitation of phenolics with bovine serum albumin (BSA) were investigated for their suitability in measuring the phenolic content of freshwaters. Phenol and a hydrolysable tannic acid were used as standards for monophenolics and polyphenolics, respectively. The individual and simultaneous application of both standards in doubly distilled water and filtered freshwater samples showed no matrix interference for the Gibbs, the Prussian Blue and the Folin-Ciocalteau assays. The quenching of phenol fluorescence and incomplete precipitation of added tannic acid in the freshwater samples were thought to originate from complexation. The Gibbs assay was specific for monophenolics, monohydroxybenzenes, with a Criterion of Detection (CoD) of 0.027 mg l(-1). Evaluating the assay using twenty-two monophenolics of lignin origin showed, apart from phenol itself, the phenolic acids vanillic, isovanillic, ferulic and syringic to have a linear response between 0 and 10 microM. The other monophenolics were not responsive in the Gibbs assay. The oxidation-based assays Prussian Blue and Folin-Ciocalteau had a CoD of 0.169 and 0.025 mg l(-1), respectively. The ratio of response of both assays for each sample was taken as an indication of the degree of polymerisation of the phenolic content. The Folin-Ciocalteau assay was used directly on the samples, on samples spiked with tannic acid at 2 and 4 mg l(-1), and after precipitation of phenolics with BSA. The difference in tannic acid equivalents before and after treatment, assayed the amount of protein precipitated phenolics. The results of all assays allowed differentiation between monophenolics (Gibbs), polyphenolics (Prussian Blue), total phenolics (Folin-Ciocalteau), complexation of added phenol and protein-precipitated phenolics. The reaction mechanisms underlying the assays were matched onto those occurring during humification. The assays were applied to six filtered freshwater samples and two humic and two fulvic acids. The results showed a different pattern for each site and illustrated varying reactivity of the 'phenolic content' of freshwater.
Benzopyrans↗
Speciation of iron in river water using a specific catalytic determination and size fractionation.
A comprehensive speciation scheme was proposed for the speciation of iron in river water (0.45 microm filtrate). The speciation was based on the catalytic determination of reactive iron as Fe3+ and Fe(III)Li/(3 -in)+, where i = 1 or 2 for a unidentate and i = 1 for a bidentate ligand, Ln-. The scheme incudes size fractionation and acid decomposition of the sample and determination of the coexisting species. The proposed scheme was applied to natural and artificial samples and acidified preparations of these. Resulting fractionation patterns of reactive and unreactive iron and of coexisting humic acid were useful for the characterization of iron species in the natural samples. The reactive iron in the molecular weight (Mr) > or = 10(4) fraction was associated with humic iron aggregates and estimated as iron complexed with them. The unreactive iron in this fraction dissociated in 0.1 M HCI and was estimated as iron in the aggregates of iron(III) hydroxide (s) and humic iron. From the fractionation results of the artificial sample, the reactive and unreactive iron in the Mr < 10(3) fraction may be formed by complexing simple anions like F- and C2O4(2-) at their naturally-occurring concentration levels. The fractionation results also suggested that humic acid and Si contributed to the formation of reactive and unreactive iron in the Mr > or = 10(4) fraction.
Catalysis↗
Characterization of humic-rich hydrocolloids and their metal species by means of competing ligand and metal exchange--an on-site approach.
An improved on-site characterization of humic-rich hydrocolloids and their metal species in aquatic environments was the goal of the present approach. Both ligand exchange with extreme chelators (diethylenetetraaminepentaacetic acid (DTPA), ethylendiaminetetraacetic acid (EDTA)) and metal exchange with strongly competitive cations (Cu(II) were used on-site to characterize the conditional stability and availability of colloidal metal species in a humic-rich German bogwater lake (Venner Moor, Münsterland). A mobile time-controlled tangential-flow ultrafiltration technique (cut-off: 1 kDa) was applied to differentiate operationally between colloidal metal species and free metal ions, respectively. DOC (dissolved organic carbon) and metal determinations were carried out off-site using a home-built carbon analyzer and conventional ICP-OES (inductively-coupled plasma-optical emission spectrometry), respectively. From the metal exchange equilibria obtained on-site the kinetic and thermodynamic stability of the original metal species (Fe, Mn, Zn) could be characterized. Conditional exchange constants Kex obtained from aquatic metal species and competitive Cu(II) ions follow the order Mn > Zn > > Fe. Obviously, Mn and Zn bound to humic-rich hydrocolloids are very strongly competed by Cu(II) ions, in contrast to Fe which is scarcely exchangeable. The exchange of aquatic metal species (e.g. Fe) by DTPA/EDTA exhibited relatively slow kinetics but rather high metal availabilities, in contrast to their Cu(II) exchange.
Chelating Agents↗