The Effects of a Strong Disaggregating Agent on Sec-Page of Aquatic and Soil Humic Matter

Abstract

Size-exclusion chromatographic (SEC) fractionation and electrophoretic separation of aquatic humic matter samples from a Finnish lake using Sephadex G-75 with 7 M urea solution as eluent and 10% polyacrylamide gel (PAGE) with urea and sodium dodecyl sulphate solution (SDS), respectively, were performed and compared to similar analyses performed on a Russian chernozem soil humic acid sample and Nordic reference fulvic and humic acid samples. The integrated whole of aquatic humic solutes and soil humic acids were found to exhibit similar SEC-PAGE behaviours. Humic matter was not excessively disaggregated by the 7 M urea and hence SEC-PAGE can with confidence be applied as a coarse, initial fractionation procedure or for certain predeterminations of the structural composition.     

Fractionation analysis of trace metals in humic substances of soils irrigated with wastewater in Central Mexico by particle induced X-ray emission

The Mezquital Valley in Central Mexico has received wastewater from Mexico City for nearly 100 years. Wastewater brings in organic matter and nutrients but also trace metals. Humic substances, the main components of organic soil matter, are responsible for retaining and regulating the mobility of trace metals in soils. In this study, humic substances were extracted from the soil and separated into distinct fractions (humic acids, fulvic acids and humins). The particle induced X-ray emission (PIXE) technique was applied to determine the metal content in bulk soil as well as in humic acids and fulvic acids not soluble in H₃PO₄. In order to assess whether the long-term input of organic matter and metals modifies the metal association with these humic substances, parcels irrigated for three time periods (5, 47 and 89 years) were selected for this study. It was observed that metals such as Zn and Cu are mainly associated with the humic acids. Fulvic acids retain mainly Cr while Pb is distributed among humic and fulvic acids. It was also observed that in general, metal retention by humic substances increases with irrigation time. Depth also affects metal association with the humic substances.     

The uniqueness of humic substances in each of soil,stream and marine environments

Definitive compositional differences are shown to exist for both fulvic acids and humic acids from soil, stream and marine environments by five different methods (¹H and ¹³C NMR spectroscopy, ¹⁴C age and δ¹³C isotopic analyses, amino acid analyses and pyrolysis-mass spectrometry). Definitive differences are also found between fulvic acids and humic acids within each environment. These differences among humic substances from various sources are more readily discerned because the method employed for the isolation of humic substances from all environments excludes most of the non-humic components and results in more purified humic isolates from water and soils. The major compositional aspects of fulvic acids and humic acids which determine the observed characteristic differences in each environment are the amounts and composition of saccharide, phenolic, methoxyl, aromatic, hydrocarbon, amino acids and nitrogen moieties.     

Preparation and characterization of humic and fulvic acid working standards—practical experience

Two fractions of both fulvic acids (FA) and humic acid (HA) were prepared by fractionation method of Pierce and Felbeck⁵ involving acid hydrolysis of soil rests. This step increases recovery of both FA and HA considerably what suggest us need for slight modification of IHSS method in some cases. The weight loss, change in organic carbon content and visible spectra are figures of merit discussed. After detailed characterization these humic substances (HS) will serve as the working standards for study of interactions between organomercurials and organic part of soil.     

Effect of Organic Substances on the Results of Anodic Stripping Voltammetry Detection of Metal Ions in Aqueous Media

Abstract

The d.c. anodic stripping voltammetry method has been used to investigate the effect of organic substances simulating the composition of natural waters on the results of determination of concentration levels of copper, lead and cadmium. The response, sensitivity and concentration (the latter determined by the standard additions method) have been used as sources of information. In the presence of enzymes, fulvic acids, humic acids and polyethylene glycol all these three parameters change in the case of determination of copper and lead, making the results unreliable. The determination of cadmium concentration is not hampered by the said organic substances.     

Electron Spin Resonance Analysis of Semiquinone Free Radicals of Aquatic and Soil Fulvic and Humic Acids

Abstract

We analyzed the solid state and aqueous solution electron spin resonance (esr) spectra of Oyster River and Podzol soil fulvic and humic acids. Because the aqueous solution esr spectra mimic the behavior of the model compound para-benzosemiquinone, we conclude that semiquinone free radicals predominate in fulvic acid. In addition a decrease in spin concentration at a potential of 0.20 volts (vs. SCE) demonstrates that the semiquinone radicals are at least partially responsible for the reducing capability of humic materials. From the above results we devised a quantitative semiquinone analysis for humic materials.     

Interaction of Humic Substances with Organic Pollutants and its Influence on the Concentration of these Pollutants from Water

Abstract

The influence of fulvic acids (FAs) and humic acids (HAs) of different origin on liquid-liquid and solid-phase extraction of hydrophobic organic compounds (HOCs) with broadly varying values of octanol-water partition coefficients K_ow has been investigated. It is shown that the solubilization by dissolved FAs and HAs can lead to a significant decrease in recovery of some HOCs even from very dilute (10–20 mg/l) aqueous solutions of these acids. The results of these investigations and an analysis of the relevant literature data, demonstrate that the extent of solubilization of HOCs by humic substances is determined not only by K_ow, but also by the specific structure of the HOCs. The hypothesis of the formation of intramolecular micelles (IMMs) by unaggregated FAs and HAs, and the partition of HOCs between water and the IMMs is put forward to explain the solubilization of HOCs.     

Binding of Organic Pollutants to Soil Organic Matter

Abstract

Binding of organic pollutants to water-soluble, low-molecular weight humic substances increases their mobility in soil and their leaching, whereas binding to high-molecular weight humic substances results in unextractable residues. Water-soluble pollutants in leachate may be bound to low-molecular weight humic material, or may be free water-soluble conversion products that are slowly released from a soil-bound form, as shown for a conversion product of the insecticide aldrin. Unextractable soil-bound 4-chloroaniline was isolated by supercritical methanol extraction 16 years after application of the phenylurea herbicide buturon to soil. Biodegradation and bioavailability of unextractable soil-bound residues are greatly reduced as compared to the free compounds. For some chlorinated anilines and phenols, biomineralization and plant uptake was shown to be highest for residues bound in fulvic acids and lowest for those in humic acids. Model experiments demonstrate that chlorinated anilines form covalent bonds with humic acid precursors.     

Flow amperometric determination of carbofuran and fenobucarb

Abstract

The sorption of pentachlorophenol (PCP) onto the aquatic humic matter (HM) for very wide concentration range (60 ng PCP/L - 1 mg PCP/L) was investigated. The binding affinity increased significantly with the acidity of the solution. The dissolved organic carbon (DOC) normalized sorption coefficients (log K_OC) of PCP were 3.39 at pH 3, 3.19 at pH 5.5 and 3.01 at pH 7. The binding of PCP took place via a two step binding mechanism: the rapid first step was followed by a second much slower one indicating that the surface of the HM is very heterogeneous containing binding sites with different binding affinities. It was possible to obtain a “fully saturated” HM-PCP adduct (also all possible micro-voids of the HM were occupied) in a very high PCP concentration. The log K_OC value for the whole concentration range was slightly smaller than that obtained under very low PCP concentration level. The Langmuir isotherm was the most suitable for the whole concentration range of PCP, whereas the Freundlich model was the most suitable for the low concentration range of PCP. The dissimilarities between different sorption models were as a whole marginal and thus it is possible without significant loss of information to describe the PCP sorption with a linear model. The results verify that the conventional humic (HA) and fulvic (FA) acid type humic solutes of fresh waters account for the main part of the PCP sorption.     

A speciation methodology to study the contributions of humic-like and fulvic-like acids to the mobilization of metals from compost using size exclusion chromatography-ultraviolet absorption-inductively coupled plasma mass spectrometry and deconvolution analysis

High performance size-exclusion chromatography (HP-SEC) with UV absorption for organic matter detection and inductively coupled plasma mass spectrometry (ICP-MS) for elemental detection have been used to study the mobilization of metals from compost as a function of pH and the molecular mass of their complexes with dissolved organic matter (DOM). Due to its heterogeneous nature, organic matter mobilized from compost shows a continuous distribution of molecular masses in the range studied (up to 80 kDa). In order to differentiate between the contribution of humic and fulvic acids (FA) to the organic matter mobilized in the pH range 5-10, their UV absorption chromatographic profiles have been deconvoluted with respect to the adjusted gaussian profiles of the humic and fulvic acids isolated from compost. Results show a preponderant contribution of fulvic acids at low pH values and an increasing percentage of humic acids (HA) mobilized at basic pH (up to 49% of total DOM at pH 10). A similar deconvolution procedure has been applied to the ICP-MS chromatograms of selected metals (Co, Cu, Pb and Bi). In general, both fulvic and humic acids contribute to the mobilization of divalent transition metals, such as copper or cobalt, whereas bismuth or lead are preferably associated to humic acids. Non-humic substances (HS) also contribute to the mobilization of cations, especially at acidic pHs. These conclusions have been extended to different elements based on deconvolution analysis results at pH 7.     

Characterization of humic and fulvic acids from Gorleben groundwater

Summary The humic material extracted from one of the Gorleben groundwaters is separated into humic and fulvic acids, and characterized, together with a commercial humic acid from Aldrich Co., for their chemical composition, size distribution, proton exchange capacity and spectroscopic characteristics. The results are compared with one another and with the literature data of other humic acids. The humic acid is fractionated by gel permeation chromatography into different size groups and the fractions are subjected to IR and ¹H-NMR spectroscopy. The high molecular weight fractions (>70000 Dalton) are poor in carboxylic groups, whereas the major fractions (approx. 10000 Dalton) contain organic acids of large molecular entities.     

Tefluthrin Sorption to Mineral Particles: Role of Particle Organic Coatings

Abstract

The sorption of tefluthrin was studied on “pure” clay minerals and those that had been coated with aquatic humic substances over a mass percent carbon range of 0.02 to 2.15. Tefluthrin sorption onto humic-coated minerals was significantly greater than on to the clean minerals and increased with increasing quantities of sorbed humic substances. Humic acid, the most aromatic coating, was the strongest sorbent, followed by fulvic acid, hydrophilic macromolecular acid and natural coatings on estuarine suspended particles. This shows the significant impact of humic coatings on the sorptive capacity of mineral particles. The sorption was linear, also consistent with the operation of a partition process. The partition coefficient normalised to organic carbon (K_oc) after deduction of the contribution from the clean mineral, ranged from 120000 to 770000 and was highest for the most aromatic humic acid fraction.     

Influence of humic substances on sorption and methylation processes of inorganic- and organo-tin species

The influence of humic substances on sorption and methylation processes for inorganic- and organotin species is presented. Four sediment samples from different locations of the Rivers Elbe, Mulde and Spittelwasser, Germany, with different organotin and humic contents were selected to extract the humic and fulvic acids. The various fractions—the original sediment, the humic acid, the fulvic acid and the residual sediment—were analysed for their organotin content. The individual buyltin species show quite different distribution patterns. Monobutyltin is found mostly associated with humic acids. Dibutyltin shows a nonunique behaviour. At low total organotin content, dibutyltin is found bonded to humic and fulvic acids, whereas at high organotin content dibutyltin is distributed more with the residual sediment. Most of the tributyltin remains in the sediment unextracted; only small quantities of it are in the fulvic acid fraction. Tetrabutyltin is only in the humic acid fraction when it binds to humic matter; it mostly remains in the sediment. General observations indicate that ionic butyltin species bind to fulvic acids whereas the non-polar tetrabutyltin is not found in the fulvic acid fractions in any of the samples. The appearance of monomethyl- and dimethyl-tin species in the humic and fulvic acid fractions after the alkaline extraction was surprising. There is a correlation between the humic content of the sample and the formation of methyltin species. Evidence is provided by experiments that humic substances act as methylation agents.     

Spurenanalyse von huminstoffen im trinkwasser: The d.c. polarographic determination of traces of humic substances in potable waters

(The d.c. polarographic determination of traces of humic substances in potable waters) The inhibiting effect of a tri-n-butylphosphate layer adsorbed at the mercury drop on the polarographic wave of copper(II) is reduced by humic substances. This effect can be utilized to determine humic substances in the range 0.05–1 mg l^-1. The standard substance used was isolated from peaty water. Humic and fulvic acids are not differentiated but amino acids, peptides and polyhydroxy compounds do not interfere.     

Determination of the phenolic-group capacities of humic substances by non-aqueous titration technique

The phenolic-group capacities of five humic substances, such as, the Aldrich humic acid, the humic and fulvic acids extracted from a soil, the humic and fulvic acids extracted from a peat have been precisely determined by the non-aqueous potentiometric titration technique. The titration by KOH in the mixed solvent of DMSO:2-propanol:water = 80:19.3:0.7 at [K⁺] = 0.02 M enabled to measure the potential change in a wide range of pOH (=−log [OH⁻]), and thus to determine the capacities of phenolic groups which could not be precisely determined in the aqueous titration. The results of the titration revealed that the mean protonation constants of the phenolic groups were nearly the same for all humic substances and close to that of phenol in the same medium, indicating that each phenolic-group in the humic substances is rather isolated and is not electronically affected by other affecting groups in the humic macromolecule.     

Fire impact on forest soils evaluated using near-infrared spectroscopy and multivariate calibration

The assessment of physico-chemical properties in forest soils affected by fires was evaluated using near infrared reflectance (NIR) spectroscopy coupled with chemometric methods. In order to describe the soil properties, measurements were taken of the total organic carbon on solid phase, the total nitrogen content, the organic carbon and the specific absorbences at 254 and 280 nm of humic substances, organic carbon in humic and fulvic acids, concentrations of NH₄⁺, Ca²⁺, Mg²⁺, K⁺ and phosphorus in addition to NIR spectra. Then, a fire recurrence index was defined and calculated according to the different fires extents affecting soils. This calculation includes the occurrence of fires as well as the time elapsed since the last fire. This study shows that NIR spectroscopy could be considered as a tool for soil monitoring, particularly for the quantitative prediction of the total organic carbon, total nitrogen content, organic carbon in humic substances, concentrations of phosphorus, Mg²⁺, Ca²⁺ and NH₄⁺ and humic substances UVSA₂₅₄. Further validation in this field is necessary however, to try and make successful predictions of K⁺, organic carbon in humic and fulvic acids and the humic substances UVSA₂₈₀. Moreover, NIR coupled with PLS can also be useful to predict the fire recurrence index in order to determine the spatial variability. Also this method can be used to map more or less burned areas and possibly to apply adequate rehabilitation techniques, like soil litter reconstitution with organic enrichments (industrial composts) or reforestation. Finally, the proposed recurrence index can be considered representative of the state of the soils.     

Separation and determination of dissolved and particulate humic substances in river water

Distribution of humic and fulvic acids in participate or dissolved form is studied by using simple leaching and sorption techniques. After filtration of water sample (100–200 ml), the filter along with suspended particles is treated with 5 ml of chloroform and 3 ml of 0.1 mol/l sodium hydroxide solution. The filter dissolves completely in the organic phase, while the suspended particles remain in the aqueous phase enabling a leaching of humic substances. The leaching is repeated once more with 2 ml of 0.1 mol/l sodium hydroxide solution. The humic and fulvic acids in the combined solution are fractionated at pH l by filtration, where the membrane filter is preliminarily coated with sodium dodecyl sulfate. On the other hand, dissolved humic substances are concentrated from a 50-ml filtered sample by sorption on a DEAE-cellulose column. They are desorbed with 5 ml of 0.1 mol/l sodium hydroxide solution and fractionated at pH 1. The spectrophotometric analysis of river water reveals that fulvic acid is predominant in suspended particles as well as in filtered samples. The concentration of dissolved humic and fulvic acids is approximately ten times that of suspended particles.     

Radio-tracer methods for studying speciation in natural waters

Radio-tracer experiments have shown that antimony, mercury and zinc interact to form complexes with humic and/or fulvic acids, whose molar masses can be estimated by gel chromatography. Sb(III) and (V) humates are stable in the pH range 7–11, but are largely dissociated below pH 4; humic acid does not reduce Sb(V) to Sb(III) in solution. Mercury forms a strong complex with humic+fulvic acids. Zinc forms complexes with both humic acids and glycine, and the humic acid complex has similar elution behaviour on dextran gel to a fraction from river water equilibrated with⁶⁵Zn. At least one other form of zinc, in addition to Zn²⁺, occurs in this river.     

Role of fulvic acids for transporting and fixing phosphate and iron ions in bean plants by radiotracer technique

Among humic substances formed by organic matter decomposition process, fulvic acids have been extensively studied because their solubility and soil fertilizer properties. This paper describes how some mineral nutrient elements are absorbed by the root as well as the foliage of bean plants and how they move in both directions depending on their association to fulvic acids. In this study, radiotracers of phosphate and iron have been used (H₂ ³²PO₄ ^-, ⁵⁹Fe²⁺). The results obtained are quantitative by instrumental detection and qualitative by autoradiography of the radiotracers. A very clear effect has been found about motion and fixation of phosphate and iron ions in bean plants brought about by fulvic acids commercially produced in Mexico by organic synthesis. This effect seems to be the more homogeneous distribution in the vegetable tissues of the mineral ions absorbed from the soil. This revised version was published online in August 2006 with corrections to the Cover Date.     

Xps Analysis of Humic and Fulvic Acids

Abstract

The composition of humic and fulvic acids is examined using X-ray Photoelectron Spectroscopy (XPS). The XPS results are compared to that of elemental analyses. XPS permits an easy detection of the different chemical forms of carbon and sulfur that exist in these complex compounds.