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At least 955 records · Page 53Linked to original sources
PubMed1994

Characterization of the humic material formed by composting of domestic and industrial biowastes. Part 1. HPLC of the cupric oxide oxidation products from humic acids.

The changes induced by humification of anaerobically digested sewage sludge, source separated biowaste, and pulp mill biosludge were determined by extracting the fractions of bitumen and humic and fulvic acids from the samples of fresh and humified composts. In all cases, a distinct decrease in the amount of bitumen could be detected during humification. The amount of humic acids increased in sewage sludge and biowaste samples, but decreased in pulp mill biosludge sample during humification. The humic acids were degraded by CuO oxidation and the phenolic degradation products were analysed by reversed-phase high-performance liquid chromatography. The yield of these aromatic degradation products was in the range 0.9-2.0% for each sample. The main phenolic degradation products were 4-hydroxybenzoic acid, vanillic acid, 4-hydroxybenzaldehyde, vanillin, syringaldehyde, and acetovanillone. Two lignin dimers, dehydrodivanillin and dehydrodiacetovanillone, were also identified.

Chromatography, High Pressure Liquid↗
PubMed1996

Microcalorimetric study of metabolic inhibition by humic acids in mitochondria from Oryctolagus cuniculus domestica liver cells.

The metabolic thermogenesis curves of mitochondria isolated from Oryctolagus cuniculus domestica liver tissue have been determined by using an LKB-2277 bioactivity monitor. After isolation, mitochondria maintain activity when stored in appropriate nutrients. The thermokinetic equation: [formula: see text] was established for the activity recovery phase of metabolism. For these studies, the order of metabolism was found to be zero. The metabolic activity of mitochondria was inhibited by humic acid, a potential toxicant in Kashin-Beck and Keshan diseases. Experimental results indicate that humic acid will effect the heat output and lag time of mitochondrial metabolism.

Animals↗
PubMed1987

Adsorption of mutagens by humic acid.

Humic acid inhibited the mutagenicity of various mutagens. The inhibitory effect was desmutagenic, heat-resistant and increased with an increase of the humic acid molecular weight. Typical monomeric components of humic acids had no desmutagenic effect. The desmutagenic effect of humic acid was caused by adsorption of mutagen, not by decomposition of mutagen. The adsorption activity was largest at its critical micelle concentration and the adsorbed mutagen was released by ultrasonication. Humic acids exist in natural environment in large amounts and may play an important role for natural purification by adsorption of mutagens.

Adsorption↗
PubMed1987

Comparison of the biological effects of humic materials under acidified conditions.

The acute and chronic effects of three types of humic material were studied using Daphnia magna at pH 5, 6, and 7. At neutral pH humic material had no biological effect. At pH 6 and 5 maximum survival and population growth rate occurred at intermediate levels of humus material (10 mg C/L, 300 mg Pt/L). Lowest survival and population growth rate occurred at pH 5 in either the absence of humus material or at concentrations exceeding 10 mg C/L (300 mg Pt/L). A second order polynomial was used to fit the dose response curve at pH 5 for both Aldrich humic acid and a natural bog water. Aldrich had greater biological activity. It is suggested that the biological behavior of aquatic humus conforms to second order rate phenomena controlled by high levels of free metals ions at low humus concentrations and direct toxic action of the dissolved organics at low pH due to increased lipophilicity.

Daphnia↗
PubMed1989

Mutagenicity and alkylating activity of the aqueous chlorination products of humic acid and their molecular weight fractions.

Fluka humic acid used as a model substrate in these studies was analysed for elemental and the oxygen-containing functional groups. It was chlorinated at C:Cl molar ratios of 1:1 and 1:0.3 and subsequently separated into molecular weight fractions by ultrafiltration. The freeze-dried, chlorinated humic acid and the respective molecular weight fractions were analyzed for TOC, TOX, alkylating activity using 4-(p-nitrobenzyl)pyridine and mutagenicity by the Ames/Salmonella/microsome assay with strains TA-98 and TA-100. Results indicated that predominantly non-volatile, direct-acting mutagenic and/or alkylating agents were formed during humic acid chlorination and that these agents were unevenly distributed among the various molecular weight fractions. Formation of mutagenic and alkylating agents were highly dependent upon level of chlorination and total organic carbon. Higher levels of mutagenic and alkylating activities were produced with increasing concentration of chlorine in the range of 0.4-1.2 chlorine equivalents per mole of carbon. However, both these activities in the freeze-dried, chlorinated humic acid solutions containing the non-volatiles or the fresh solutions decreased gradually with increasing pH and storage time, apparently due to degradation and hydrolysis of some of the components.

Alkylating Agents↗
PubMed1990

Influence of complexing agents and surfactants on metal speciation analysis in road runoff.

A combination of medium exchange and sample acidification techniques is used to enable the calculation of the individual effects of complexing agents and surfactants on the deposition and stripping steps in anodic stripping voltammetry for copper, lead and cadmium in road and urban runoff. A simple acidification procedure is presented for determination of the toxic fraction.

Benzopyrans↗
PubMed1992

Humic acid: inhibitor of plasmin.

Synthetic humic acid, well water humic acid and commercial humic acid (Aldrich) all have the ability to inhibit human plasmin activity. At a concentration of 20 micrograms/ml, all three species will result in 93%, 70% and 40% of residual plasmin activity, respectively. The components of humic acid, such as protocatechuic acid, resorcinol, vanillic acid and ferulic acid do not have such inhibitory activities. The ability of humic acid to inhibit human plasmin has not been reported. It is, therefore, a new plasmin inhibitor.

Coumaric Acids↗
PubMed1995

Degradation of PCB in different soils by inoculated Alcaligenes xylosoxidans.

The degradation of PCB in soils by the biphenyl-utilising strain Alcaligenes xylosoxidans was studied in different soil types. In addition to the congener specificity, significant differences in the degradation of PCB by the strain in the different soil types were observed. Efficiency of degradation was generally better in sterilised soils, but the differences were not as significant as the differences observed between different soil types. These results indicate that the degradation of PCB is probably related not only to the capabilities of the strain employed and quality and amount of competitive species inhabiting the soils, but also to the soil sorption of the PCB congeners. Degradation is faster in the soils containing an intermediate amount of organic carbon with a high portion of total and aromatic carbon in humic acids.

Alcaligenes↗
PubMed1982

Nickel toxicity to fungi: influence of environmental factors.

The toxicity of nickel (Ni) to the mycelial growth rates of filamentous fungi was influenced by environmental abiotic factors. Increasing the pH from acidic to alkaline levels completely eliminated the toxicity of Ni to Achyla sp. and Saprolegnia sp. Magnesium or zinc, but not potassium, sodium, calcium, or ferric, ions reduced the toxicity of Ni to Achyla sp. An antagonistic interaction between a combination of Ni + Pb was noted toward growth of Achyla sp. and Saprolegnia sp.; the interactions between combinations of Ni + Cd or Ni + Hg were less well defined. Chlorophyll, at 1%, reduced the toxicity of Ni toward Saprolegnia sp. and Cunninghamella blakesleeana, and increasing the chlorophyll concentration from 0.2 to 1% progressively reduced the toxicity of Ni to Aspergillus clavatus. The addition of 1% humic acid reduced the toxicity of Ni to Saprolegnia sp. and C. blakesleeana, and increasing the humic acid concentration from 0.2 to 1% progressively reduced the toxicity of Ni toward Aspergillus flavus. A. flavus was more resistant to Ni at 33 than at 23 degrees C.

Cadmium↗
PubMed1989

The effect of humic acid on the toxicity and bioavailability of trivalent chromium.

The influence of humic acid (HA) on the toxicity and bioavailability of two forms of trivalent chromium (chromic chloride and chrome lignosulfonate) was evaluated using a common freshwater invertebrate, Daphnia pulex. With both compounds, the 50 mg/liter HA significantly decreased toxicity at all time points examined. The remaining two HA concentrations, 0.5 and 5 mg/liter, either had no influence or decreased the toxicity of the compounds. Humic acid appeared to have no influence on the bioavailability of chrome lignosulfonate. However, for chromic chloride, 5 and 50 mg/liter HA decreased the percentage free chromium at all time points examined.

Animals↗
PubMed1991

Evaluation of humic-pesticide interactions on the acute toxicity of selected organophosphate and carbamate insecticides.

The ability of water resource managers to accurately predict the toxicity of agricultural chemicals in aquatic ecosystems is essential for the development of reliable water quality standards. At present, accurate predictions are difficult due to the paucity of data concerning the interaction of these chemicals with organic constituents of the freshwater chemical matrix. Dissolved humic materials are ubiquitous components of freshwater ecosystems and can affect the availability and toxicity of chemicals in the environment. In the present investigation, the influence of humic acid (HA) on the acute toxicity of selected organophosphate and carbamate insecticides was examined using a bacterial bioluminescence inhibition assay. EC50 values for the pesticides were determined in the presence of 0, 0.5, 5.0, 50, and 100 mg/liter HA. A combination of antagonistic and synergistic effects was observed with the selected organophosphate and carbamate insecticides examined. HA significantly reduced the toxicity of azinophos-methyl, chlorpyrifos, and carbofuran, while enhanced toxicity was observed with methyl parathion and carbaryl. These results indicate that humic-pesticide interactions can alter the toxicity of agricultural chemicals. Moreover, the influence of humic materials on the toxicity of these chemicals is dependent on temporal relationships and HA concentration.

Carbamates↗
PubMed1983

Formation of mutagens following chlorination of humic acid. A model for mutagen formation during drinking water treatment.

Aqueous chlorination of humic acids results in the formation of compounds with direct-acting mutagenic activity in the Ames/Salmonella plate assay for tester strains TA98, TA100, TA1535, TA1537 and TA1538. The addition of a rat-liver microsomal fraction (S9) plus cofactors causes a substantial decrease of activity, the extent of which is tester strain dependent. The non-chlorinated humic acids are not mutagenic either in the presence or absence of S9. Formation of mutagenic activity and of total organic halogen (TOX) is linearly related to humic concentration in the range of 0.2-1.6 mg/ml total organic carbon (TOC), and to chlorine concentration in the range of 0.1-1.0 chlorine equivalents per mole of carbon. The mutagenic activity is due predominantly to non-volatile compounds. Mutagenic activity is also detectable, after sample concentration by lyophilization, upon chlorination at a humic acid level of 0.02 mg/ml TOC. The specific mutagenic activities (per mg TOX), and also the degree of chlorine incorporation into humic acid, at 0.02 mg/ml TOC are similar to those present after chlorination at 1 mg/ml TOC. Production of mutagens is greatly dependent on the chlorination pH, with a pattern of decreasing mutagenic activity with increasing pH. This order of activity can be at least partially explained by the alkali liability of the compounds. Chlorination of commercial humic acids is proposed as a model for examination of mutagen formation during water chlorination.

Animals↗
PubMedDate not supplied

Identification of mutagenic compounds formed during chlorination of humic acid.

Humic acid chlorination products are being studied in an effort to identify the chemicals responsible for the mutagenicity formed during water chlorination. In the present report, 19 chlorinated organic compounds have been identified and quantified in ether extracts of chlorinated humic acid solutions. 10 of these compounds, including a number of chlorinated propanones and chlorinated propenals, are direct-acting mutagens in the Salmonella/microsome mutagenicity assay. The position of the chlorine substituent has been found to be an important factor in the mutagenic activity of these two classes of compounds. The total mutagenicity of the compounds identified thus far, when tested either individually or as a composite, accounts for only 7-8% of the total TA100 mutagenicity, and less than 2% of the TA98 mutagenicity formed during humic acid chlorination. The addition of bromide to the humic acid chlorination reaction results in up to a 2-fold increase in the level of mutagenicity formed.

Animals↗
PubMed1987

Mutagenicity of products formed by ozonation of naphthoresorcinol in aqueous solutions.

The mutagenicity of products formed by ozonation of naphthoresorcinol in aqueous solution was assayed with Salmonella typhimurium strains TA97, TA98, TA100, TA102 and TA104 in the presence and absence of S9 mix from phenobarbital- and 5,6-benzoflavone-induced rat liver. Ozonated naphthoresorcinol was mutagenic in TA97, TA98, TA100 and TA104 without S9 mix. By the addition of S9 mix, the mutagenic activity of ozonated naphthoresorcinol was markedly suppressed in TA98 and TA100, but became positive in TA102. High-performance liquid chromatography (HPLC) after derivatization to 2,4-dinitrophenylhydrazones demonstrated the formation of glyoxal as an ozonation product of naphthoresorcinol. Ion chromatographic technique also demonstrated the formation of o-phthalic acid, muconic acid, maleic acid, mesoxalic acid, glyoxylic acid and oxalic acid as ozonation products. The mutagenicity assays of these identified products with five Salmonella showed that glyoxal and glyoxylic acid were directly mutagenic; the former in TA100, TA102 and TA104, the latter in TA97, TA100 and TA104. In the presence of S9 mix, glyoxylic acid gave a positive response of mutagenicity for TA102. The experimental evidence supported that glyoxal and glyoxylic acid may contribute to the mutagenicity of ozonated naphthoresorcinol.

Animals↗
PubMed1993

Desmutagenic activity of natural humic acids: inhibition of mitomycin C and maleic hydrazide mutagenicity.

Humic acids are natural components of organic matter widespread in the environment. In spite of the incomplete knowledge about their composition, increasing interest in humic acid activity is justified by their ubiquity. Four different humic acids have been tested in Chinese hamster ovary cells in vitro, both alone and in combination with two well-known mutagens (mitomycin C and maleic hydrazide). Data about sister-chromatid exchanges, mitotic and proliferation indices were collected. Our results, on the whole, indicate: (i) a slight mutagenicity and toxicity of tested humic acids, probably due to chlorination during sample preparation; (ii) a desmutagenic rather than antimutagenic activity of the tested humic acids.

Animals↗
PubMed1993

High-field 13C solid-state NMR studies of stream humic and fulvic acids with fast magic-angle spinning.

Standard samples of stream humic and fulvic acids have been studied by high-resolution 13C solid-state NMR. The spectra have been recorded at a high (9.4 T) magnetic field using 1H-13C cross-polarization (CP) and proton high-power decoupling (HPDEC) with fast (up to 15 kHz) magic-angle spinning (MAS). The widths of the spectral lines decrease with increasing spinning rate. This is probably due to the overlap of spinning sidebands with resonances at low speeds and to a more effective averaging of anisotropic broadening at high speeds. However, fast MAS modulates the CP signal intensities, making quantitative analysis very difficult.

Benzopyrans↗