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Sample records for humic substances

  1. HUMIC SUBSTANCES AND CONTAMINANT TRANSPORT

    EPA Science Inventory

    Humic substances are widely distributed in the environment, occurring in soils and waters. hey are the products of microbial degradation of dead vegetable and animal matter. hey account for the major portion of dissolved organic matter. hey are water soluble and have the ability ...

  2. Preparative isolation of aquatic humic substances

    USGS Publications Warehouse

    Thurman, E.M.; Malcolm, R.L.

    1981-01-01

    A useful procedure has been developed which utilizes adsorption chromatography followed by size-exclusion chromatography, hydrogen saturation by ion exchange, and lypholization to obtain low-ash aqueous humic substances. The preparative concentration of aquatic humic substances is done by multiple reconcentration procedures even though initial concentrations of aqueous humus may be less than 25 ??g/L. The procedure yields concentration factors of 25 000 times for both humic and fulvic acid in water.

  3. Molecular size of aquatic humic substances

    USGS Publications Warehouse

    Thurman, E.M.; Wershaw, R. L.; Malcolm, R.L.; Pinckney, D.J.

    1982-01-01

    Aquatic humic substances, which account for 30 to 50% of the organic carbon in water, are a principal component of aquatic organic matter. The molecular size of aquatic humic substances, determined by small-angle X-ray scattering, varies from 4.7 to 33 A?? in their radius of gyration, corresponding to a molecular weight range of 500 to greater than 10,000. The aquatic fulvic acid fraction contains substances with molecular weights ranging from 500 to 2000 and is monodisperse, whereas the aquatic humic acid fraction contains substances with molecular weights ranging from 1000 to greater than 10,000 and is generally polydisperse. ?? 1982.

  4. Complexing of metal ions by humic substances

    SciTech Connect

    Bryan, N.D.; Zhang, Y.; Jones, M.N.

    1995-12-31

    The interaction of metal ions with humic substances is being studied using two different techniques. UV-scanning ultracentrifugation is being used to determine molecular weights and to investigate changes in aggregation brought about by metal ion complexation. The relationship between cation charge and conformation of the humic ligands is also being investigated. The complexation of actinide elements (U, Np, Pu, Am) by humic substances from soils contaminated by both natural processes and by low-level effluent releases is also being studied. Gel permeation chromatography has been used to show both that different fractions of humic substances vary greatly in their effectiveness as ligands and that different actinide elements associate with different fractions. These studies have also shown that uranium desorption is kinetically controlled by humic substances.

  5. Molecular aggregation of humic substances

    USGS Publications Warehouse

    Wershaw, R. L.

    1999-01-01

    Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

  6. COMPARISON OF PHOTOCHEMICAL BEHAVIOR OF VARIOUS HUMIC SUBSTANCES IN WATER: III. SPECTROSCOPIC PROPERTIES OF HUMIC SUBSTANCES

    EPA Science Inventory

    Spectral absorption coefficients and fluorescence quantum efficiencies were determined for humic substances from a variety of sources. Specific absorption coefficients, K(h), for humic substances at wavelengths lambda from 300 to 500 nm can be closely described by the relation Ae...

  7. Humic substance formation during wastewater infiltration

    SciTech Connect

    Siegrist, R.L. ); Hildmann-Smed, R.; Filip, Z.K. , Langen . Inst. fuer Wasser-, Boden- und Lufthygiene); Jenssen, P.D. . Centre for Soil and Environmental Research)

    1991-01-01

    Soil infiltration of wastewater effluents is a widely practiced method of treatment and disposal/reuse throughout the world. Renovation of the wastewater results from a wide variety of complex physicochemical and biological processes. One set of processes is speculated to involve the accumulation of organic matter by filtration and sorption followed by formation of humic substances. This humic substance formation can effect the performance of soil treatment systems by contributing to soil pore clogging and reduction in hydraulic capacity, and by yielding reactive substances and an enhancement of purification processes. While there has been a wealth of research into the nature and genesis of humic substances in terrestrial environments, there has been limited research of humic substance formation during soil infiltration of wastewater. The purpose of the research reported herein was to determine if humic substances can form under conditions typical of those present during wastewater infiltration into natural soil systems. This work was conducted during 1989 to 1990 as a collaborative effort between the Centre for Soil and Environmental Research, located in Aas, Norway and the Institute for Water, Soil and Air Hygiene located in Langen, West Germany. 11 refs., 3 figs., 6 tabs.

  8. CHLORINATION OF AQUATIC HUMIC SUBSTANCES

    EPA Science Inventory

    This research program was initiated with the overall objective of increasing our understanding of the chemical structures of aquatic humic material and their behavior during chemical oxidation in particular with chlorine. Experimental methods were devised for the isolation of hum...

  9. On the nature of humic substances

    NASA Astrophysics Data System (ADS)

    Fedotov, G. N.; Shoba, S. A.

    2015-12-01

    It is argued that the isolation of low-molecular-weight compounds from humic substances does not prove their supramolecular nature, because small molecules can be sorbed on macromolecules by interacting with them due to noncovalent bonds. The relative mobility of molecular segments in humic substances has been proposed to be used as a criterion for the discrimination between the humic substances of supraand macromolecular nature. The macromolecules are characterized by mobility of their segments, whereas supramolecular systems have stiff structure. This difference between macroand supramolecules results in different behaviors of the matrices (gels) formed from them in the processes of segregation. In the macromolecules, the formations of a new phase appearing at the segregation (microphase separation) are of nano size, at least in one dimension. They are incapable of moving within the matrix and form a well-known, limited set of systems. In the supramolecular matrices, the new-phase formations should have higher mobility and ability to move within the matrix with the formation of particles and zones of not only nano, but also micro sizes, as well as a significantly larger set of systems, including fractal configurations. The experimental electron microscopic study of the humic matrices of soil gels shows that the new-phase formations in the matrix of humic substances have not only nano, but also micro sizes and are capable of moving within the matrix, which confirms the supramolecular nature of humic substances. The proposed method has allowed generalizing the supraand macromolecular approaches, because macromolecules can enter into the composition of supramolecular systems. It is no less important that the behavior of HSs can be perceived as the behavior of stiff impenetrable particles that may compose the structures of different types and sizes.

  10. MEASUREMENTS OF BINDING SITE CONCENTRATIONS IN HUMIC SUBSTANCES

    EPA Science Inventory

    The use of thermodynamic models to calculate the effects of humic substances on metal speciation requires that the complexation capacity (CC) of the humic substance be determined. If the CC of a humic substance is viewed as a compositional rather than a thermodynamic property, th...

  11. Involvement of humic substances in regrowth.

    PubMed

    Camper, Anne K

    2004-05-01

    There appear to be interactions in the distribution system that complicate the ability to use AOC/BDOC as an independent assessment of regrowth potential. Two such complications are the limitation of the assays themselves and the potential interaction between the organic carbon concentration with the presence of disinfectants and pipe materials. To address these interactions, a series of experiments spanning several years have been conducted in model distribution systems at the Center for Biofilm Engineering (CBE) using soil-derived humics. When compared to easily utilized organics, humic substances supported the same order of magnitude of biofilm organisms. As carbon concentration was increased from 500 to 1000 to 2000 ppb, there was no increase in growth rate of the organisms, suggesting zero-order kinetics. If the system was chlorinated, there was less biomass, but growth rates were higher. In the presence of corrosion products, humic-fed systems supported more organisms than a control system fed biologically treated water. When free chlorine was maintained at a residual of about 0.2 mg/l, biofilm numbers on the surfaces were reduced. Phosphate alone did not result in fewer bacteria, while a combination of chorine and phosphate had the best results (lowest biofilm numbers). Adjustment to pH 9 was not effective. Recently completed work compared increasing levels of humic substances in the presence of free chlorine and monochloramine on biofilm growth on a number of surfaces (PVC, epoxy, cement, ductile iron). As the concentration of humic substances was increased from 0, 0.5 to 2 mg/l, there was an increase in biofilm numbers on all surfaces. This effect was the most pronounced on iron surfaces. These results illustrate that carbon compounds not measured by the BDOC or AOC tests may profoundly influence biofilm numbers. In addition, iron surfaces are at much higher risk for elevated biofilm counts in the presence of humic substances, even if disinfection is

  12. Tritium Enrichment in the Hydration Sphere of Humic Substances

    SciTech Connect

    Wierczinski, Birgit; Muellen, Guenther; Tuerler, Andreas

    2005-07-15

    Humic and fulvic acid can be combined under the term 'humic substances' and are natural substances with a complex structure. The structural details are not known, however, due to the functional groups present in these compounds the formation of hydrogen bonds is easily attained. Several humic substances were investigated for their potential use as compounds, which are applicable for tritium enrichment from aqueous solution. For comparison a simple compound, malonic acid, representing only few functional groups was investigated. The experiments were performed using a cryosublimation apparatus, which was run well below equilibrium vapor pressure to avoid any isotope fractionation of HTO and H{sub 2}O. A higher enrichment factor was found for natural humic acid compared to fulvic acid, however, no enrichment could be found for a synthetic humic acid and malonic acid. Interpretation of the results is difficult since no detailed information on the chemical structure of humic substances is known.

  13. Effect of humic substances on the flotation response of coal

    SciTech Connect

    Lai, R.W.; Wen, W.W. ); Okoh, J.M. )

    1989-01-01

    This study investigated the generation of humic substances from the coal and the coal surface, and evaluated the effect of humic substances on the surface property of coal. The humic substances in aqueous solution were readily adsorbed on the surface of fresh coal. The adsorption affects the surface hydrophobicity of the coal and, hence, the flotation recovery of coal. The adsorption of humic substances is maximum at neutral pH and diminishes toward both the alkaline pH and the acid pH. This effect is reflected in the flotation responses of the fresh coal. Solutions of humic substances were oxidized with oxygen gas and ozone. The oxidation of humic substances in solution resulted in an adsorption that greatly enhanced the hydrophilicity of the coal and thus impaired the floatability of the coal. On the other hand, the ozonation of humic substances in solution resulted in the decomposition of humic substances and an improvement in the flotation response of the coal. Direct oxidation and ozonation of coal surface decreased the hydrophobicity of the coal, which resulted in a decrease in the flotation response.

  14. Photochemical aspects related to humic substances

    SciTech Connect

    Frimmel, F.H. )

    1994-01-01

    Dissolved humic substances (HS) show yellow color and relatively strong absorption in the UV range [a(254 nm) ca. 0.04 cm[sup [minus]1] for c(DOC) = 1 mg/L]. This is the basis for photochemical reactions in the photic zone of aquatic systems and in water treatment using IV sources. Even though understanding the mechanisms involved in the energy transfer and the resulting reactions is hampered by the poorly defined structure of HS, reliable information has been gathered on some typical aspects of their photochemistry. The luminescence of HS can be influenced and partly quenched by molecular interactions with other water constituents (e.g., heavy metals and organic micropollutants). The presence of oxygen may lead to the sensitized production of singlet oxygen (O[sub 2]), that can react specifically with substances containing diene structures or low valent sulfur. Because of the presence of these structures in HS, humic molecules will also react with the sensitized products. As a consequence, their biological, chemical, and physical properties are influenced. In addition, HS have a significant impact on the photochemical treatment of organic micropollutants in water. This has to be kept in mind when using photochemical steps for water treatment. The results from model experiments reflecting the conditions in surface water and in water treatment are given and discussed. In the presence of H[sub 2]O[sub 2], irradiation led to a transformation and partial degradation of HS. The rate of photochemical degradation of pesticides (e.g., atrazine) was decreased in the presence of HS. Fe and Mn quenched the luminescence. From this, a decrease of excited states of HS for sensitizing reactions can be deduced. The results suggest the manyfold and significant influences of HS on the photochemistry of aquatic systems. 66 refs., 9 figs., 7 tabs.

  15. Humic substances biological activity at the plant-soil interface

    PubMed Central

    Trevisan, Sara; Francioso, Ornella; Nardi, Serenella

    2010-01-01

    Humic substances (HS) represent the organic material mainly widespread in nature. HS have positive effects on plant physiology by improving soil structure and fertility and by influencing nutrient uptake and root architecture. The biochemical and molecular mechanisms underlying these events are only partially known. HS have been shown to contain auxin and an “auxin-like” activity of humic substances has been proposed, but support to this hypothesis is fragmentary. In this review article, we are giving an overview of available data concerning molecular structures and biological activities of humic substances, with special emphasis on their hormone-like activities. PMID:20495384

  16. Molecular structure in soil humic substances: The new view

    SciTech Connect

    Sutton, Rebecca; Sposito, Garrison

    2005-04-21

    A critical examination of published data obtained primarily from recent nuclear magnetic resonance spectroscopy, X-ray absorption near-edge structure spectroscopy, electrospray ionization-mass spectrometry, and pyrolysis studies reveals an evolving new view of the molecular structure of soil humic substances. According to the new view, humic substances are collections of diverse, relatively low molecular mass components forming dynamic associations stabilized by hydrophobic interactions and hydrogen bonds. These associations are capable of organizing into micellar structures in suitable aqueous environments. Humic components display contrasting molecular motional behavior and may be spatially segregated on a scale of nanometers. Within this new structural context, these components comprise any molecules intimately associated with a humic substance, such that they cannot be separated effectively by chemical or physical methods. Thus biomolecules strongly bound within humic fractions are by definition humic components, a conclusion that necessarily calls into question key biogeochemical pathways traditionally thought to be required for the formation of humic substances. Further research is needed to elucidate the intermolecular interactions that link humic components into supramolecular associations and to establish the pathways by which these associations emerge from the degradation of organic litter.

  17. CAPILLARY ELECTROPHORESIS FOR THE CHARACTERIZATION OF HUMIC SUBSTANCES

    EPA Science Inventory

    The potential of high performance capillary electrophoresis (HPCE), especially in the free solution mode (FSCE), is demonstrated for the analysis/characterization of environmental humic substances (HUS). he very high efficiency of HPCE separations allows the production of electro...

  18. The interaction of humic substances with cationic polyelectrolytes.

    PubMed

    Kam, S K; Gregory, J

    2001-10-01

    The anionic charge carried by aquatic humic substances plays a major part in their interaction with metal ions and other cationic species. Removal of such substances by coagulation and flocculation can be, at least partly, determined by charge neutralisation. In this work, the charge densities of a commercial humic acid and an aquatic humic extract have been investigated by studying their interactions with a series of synthetic cationic polyelectrolytes. These covered a range of charge densities and molecular weights. The techniques used were colloid titration by spectrophotometry and streaming current detection, and flocculation determined by colour removal and by an optical monitoring method. For a given cationic polyelectrolyte, all four methods gave charge densities for humic substances which were in good agreement. However, systematic differences in the apparent humic charge density were found, depending on the charge density of the cationic polyelectrolyte used. With low charge density polyelectrolytes, the apparent anionic charge of the humic substances was found to be low. With higher polyelectrolyte charge densities, the apparent humic substance charge density increases and reaches a limiting value when the polyelectrolyte charge is greater than about 3 meq/g. This indicates a non-stoichiometric interaction between the anionic sites of the humic substances and the cationic charges of the low-charge polyelectrolytes. Optimum flocculation of humics occurred with less cationic charge in the case of low-charge polyelectrolytes than those with higher charge density. However, the degree of removal was considerably better in the latter case. In all cases, the molecular weight of the cationic polyelectrolytes (over a range from about 50,000 to 15 million) appeared to have no effect on the results. PMID:11561615

  19. DBP formation of aquatic humic substances

    USGS Publications Warehouse

    Pomes, M.L.; Green, W.R.; Thurman, E.M.; Orem, W.H.; Lerch, H.E.

    1999-01-01

    Aquatic humic substances (AHSs) in water generate potentially harmful disinfection by-products (DBPs) such as haloacetic acids (HAAs) and trihalomethanes (THMs) during chlorination. AHSs from two Arkansas reservoirs were characterized to define source, identify meta-dihydroxybenzene (m-DHB) structures as probable DBP precursors, and evaluate predicted HAA and THM formation potentials. Elemental nitrogen content 0.5 ??eq/mg, ??13C values of -27???, and low yields of syringyl phenols found by cupric oxide (CuO) oxidation suggest a pine tree source for the AHSs found in the Maumelle and Winona reservoirs in Little Rock, Ark. CuO oxidation yielded fewer m-DHB structures in Maumelle AHSs than in Winona AHSs. A higher 3,5-dihydroxybenzoic acid (3,5-DHBA) content correlated with increased HAA and THM formation potential. The 3,5-DHBA concentration in Winona AHSs was similar to the range found in AHSs extracted from deciduous leaf litter, twigs, and grass leachates.

  20. A unifying model of cation binding by humic substances

    SciTech Connect

    Tipping, E.; Hurley, M.A. )

    1992-10-01

    Humic substances (humic and fulvic acids) are recognized to interact extensively with cations in natural waters and soils, with important effects on chemical speciation. There have been numerous laboratory studies of the interactions-reviewed by Boggs et al. (1985), Buffle (1988) and Sposito (1986)-and these have yielded a considerable body of quantitative binding data. However, the information is difficult to apply to natural systems because of the lack of a suitable model that can take into account competition effects among cations, including protons, and the influence of ionic strength. Another problem, at least in principle, is that the humic samples studied have come from a variety of sources and, therefore, may be intrinsically different in their ion-binding properties. The purpose of the work described here was to formulate a model of ion-binding by humic substances that could be used over a range of conditions, and to obtain parameters by analyzing published data on proton-humic and metal-humic interactions. The study aims to place available data into a unifying framework in order to rationalize present knowledge and aid the iterative processes of further experimentation and consequent model improvement. In this study, the authors concentrate on data for fulvic-type material, but the model (Model V) is applicable to all humic substances.

  1. Humic substances enhance chlorothalonil phototransformation via photoreduction and energy transfer.

    PubMed

    Porras, Jazmín; Fernández, Jhon J; Torres-Palma, Ricardo A; Richard, Claire

    2014-02-18

    The photodegradation of chlorothalonil, a polychlorinated aromatic fungicide widely used in agriculture, was investigated under ultraviolet-visible irradiation in the presence and absence of different humic substances that significantly enhance the chlorothalonil phototransformation. On the basis of a kinetic model, an analytical study, the effect of scavengers, the chlorothalonil phosphorescence measurement, and varying irradiation conditions, it was possible to demonstrate that this accelerating effect is due to their capacity to reduce the chlorothalonil triplet state via H-donor reaction and to energy transfer from the triplet humic to ground state chlorothalonil. Energy transfer occurs at wavelengths below 450 nm and accounts for up to 30% of the reaction in deoxygenated medium upon irradiation with polychromatic light (300-450 nm). This process is more important with Elliott humic and fulvic acids and with humic acids extracted from natural carbonaceous material than with Nordic NOM and Pahokee peat humic acids. The obtained results are of high relevance to understanding the processes involved in chlorothalonil phototransformation and the photoreactivity of humic substances. Chlorothalonil is one of the rare molecules shown to react by energy transfer from excited humic substances. PMID:24455968

  2. Mechanisms of humic substances degradation by fungi

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Hadar, Y.; Grinhut, T.

    2012-04-01

    Humic substances (HS) are formed by secondary synthesis reactions (humification) during the decay process and transformation of biomolecules originating from plants and other dead organisms. In nature, HS are extremely resistant to biological degradation. Thus, these substances are major components in the C cycle and in the biosphere and therefore, the understanding of the process leading to their formation and transformation and degradation is vital. Fungi active in the decomposition process of HS include mainly ascomycetes and basidiomycetes that are common in the upper layer of forest and grassland soils. Many basidiomycetes belong to the white-rot fungi (WRF) and litter-decomposing fungi (LDF). These fungi are considered to be the most efficient lignin degraders due to their nonspecific oxidizing enzymes: manganese peroxidase (MnP), lignin peroxidase (LiP) and laccase. Although bacteria dominate compost and participate in the turnover of HS, their ability to degrade stable macromolecules such as lignin and HS is limited. The overall objectives of this research were to corroborate biodegradation processes of HS by WRF. The specific objectives were: (i) To isolate, identify and characterize HS degrading WRF from biosolids (BS) compost; (ii) To study the biodegradation process of three types of HS, which differ in their structure, by WRF isolated from BS compost; and (iii) To investigate the mechanisms of HA degradation by WRF using two main approaches: (a) Study the physical and chemical analyses of the organic compounds obtained from direct fungal degradation of HA as well as elucidation of the relevant enzymatic reactions; and (b) Study the enzymatic and biochemical mechanisms involved during HA degradation. In order to study the capability of fungi to degrade HS, seventy fungal strains were isolated from biosolids (BS) compost. Two of the most active fungal species were identified based on rDNA sequences and designated Trametes sp. M23 and Phanerochaetesp., Y6

  3. Humic substances as a mediator for microbially catalyzed metal reduction

    USGS Publications Warehouse

    Lovley, D.R.; Fraga, J.L.; Blunt-Harris, E. L.; Hayes, L.A.; Phillips, E.J.P.; Coates, J.D.

    1998-01-01

    The potential for humic substances to serve as a terminal electron acceptor in microbial respiration and to function as an electron shuttle between Fe(III)-reducing microorganisms and insoluble Fe(III) oxides was investigated. The Fe(III)-reducing microorganism Geobacter metallireducens conserved energy to support growth from electron transport to humics as evidenced by continued oxidation of acetate to carbon dioxide after as many as nine transfers in a medium with acetate as the electron donor and soil humic acids as the electron acceptor. Growth of G. metallireducens with poorly crystalline Fe(III) oxide as the electron acceptor was greatly stimulated by the addition of as little as 100 ??M of the humics analog, anthraquinone-2,6-disulfonate. Other quinones investigated, including lawsone, menadione, and anthraquinone-2-sulfonate, also stimulated Fe(III) oxide reduction. A wide phylogenetic diversity of microorganisms capable of Fe(III) reduction were also able to transfer electrons to humics. Microorganisms which can not reduce Fe(III) could not reduce humics. Humics stimulated the reduction of structural Fe(III) in clay and the crystalline Fe(III) forms, goethite and hematite. These results demonstrate that electron shuttling between Fe(III)-reducing microorganisms and Fe(III) via humics not only accelerates the microbial reduction of poorly crystalline Fe(III) oxide, but also can facilitate the reduction of Fe(III) forms that are not typically reduced by microorganisms in the absence of humics. Addition of humic substances to enhance electron shuttling between Fe(III)-reducing microorganisms and Fe(III) oxides may be a useful strategy to stimulate the remediation of soils and sediments contaminated with organic or metal pollutants.

  4. Humic substances interfere with detection of pathogenic prion protein

    USGS Publications Warehouse

    Smith, Christen B.; Booth, Clarissa J.; Wadzinski, Tyler J.; Legname, Giuseppe; Chappell, Rick; Johnson, Christopher J.; Pedersen, Joel A.

    2014-01-01

    Studies examining the persistence of prions (the etiological agent of transmissible spongiform encephalopathies) in soil require accurate quantification of pathogenic prion protein (PrPTSE) extracted from or in the presence of soil particles. Here, we demonstrate that natural organic matter (NOM) in soil impacts PrPTSE detection by immunoblotting. Methods commonly used to extract PrPTSE from soils release substantial amounts of NOM, and NOM inhibited PrPTSE immunoblot signal. The degree of immunoblot interference increased with increasing NOM concentration and decreasing NOM polarity. Humic substances affected immunoblot detection of prion protein from both deer and hamsters. We also establish that after interaction with humic acid, PrPTSE remains infectious to hamsters inoculated intracerebrally, and humic acid appeared to slow disease progression. These results provide evidence for interactions between PrPTSE and humic substances that influence both accurate measurement of PrPTSE in soil and disease transmission.

  5. Amino acid composition of humic substances in tundra soils

    NASA Astrophysics Data System (ADS)

    Vasilevich, R. S.; Beznosikov, V. A.

    2015-06-01

    Peripheral amino acid fragments of humic and fulvic acid molecules from tundra soils have been identified and quantified. A significant weight fraction of amino acids has been found in humic acid preparations, which exceeds their content in fulvic acids. Features of the amino acid composition of humic substances along the soil profile and depending on the degree of hydromorphism and the proportions of different (neutral, basic, acidic, cyclic) groups in amino acids have been revealed. The molar ratio between the hydroxy and heterocyclic amino acids reflects the degree of humification of the soil.

  6. Immobilized humic substances and immobilized aggregates of humic substances as sorbent for solid phase extraction.

    PubMed

    Erny, Guillaume L; Gonçalves, Bruna M; Esteves, Valdemar I

    2013-09-01

    In this work, humic substances (HS) immobilized, as a thin layer or as aggregates, on silica gel were tested as material for solid phase extraction. Some triazines (simazine, atrazine, therbutylazine, atrazine-desethyl-desisopropyl-2-hydroxy, ametryn and terbutryn), have been selected as test analytes due to their environmental importance and to span a large range of solubility and octanol/water partition coefficient (logP). The sorbent was obtained immobilizing a thin layer of HS via physisorption on a pre-coated silica gel with a cationic polymer (polybrene). While the sorbent could be used as it is, it was demonstrated that additional HS could be immobilized, via weak interactions, to form stable humic aggregates. However, while a higher quantity of HS could be immobilized, no significant differences were observed in the sorption parameters. This sorbent have been tested for solid phase extraction to concentrate triazines from aqueous matrixes. The sorbent demonstrated performances equivalent to commercial alternatives as a concentration factor between 50 and 200, depending on the type of triazines, was obtained. Moreover the low cost and the high flow rate of sample through the column allowed using high quantity of sorbent. The analytical procedure was tested with different matrixes including tap water, river water and estuarine water. PMID:23916952

  7. Photogeneration of singlet oxygen by humic substances: comparison of humic substances of aquatic and terrestrial origin.

    PubMed

    Paul, Andrea; Hackbarth, Steffen; Vogt, Rolf D; Röder, Beate; Burnison, B Kent; Steinberg, Christian E W

    2004-03-01

    The singlet oxygen (1(O2)) luminescence of 27 isolated humic substances (HS), natural organic matter, ultrafiltrates, and the synthetic fulvic acid HS1500 has been investigated by time-resolved spectroscopy in buffered D(2)O. The samples include both reverse osmosis isolates from lakes in Scandinavia, Canada, and Germany, and IHSS fulvic and humic acids of aquatic and terrestrial origin. The quantum yields of 1(O2) formation (PhiDelta) obtained on laser excitation at 480 nm ranged between 0.06 (HS1500) and 2.7%(fulvic acid from soil, IHSS). In our study, a general trend towards higher PhiDelta in terrestrial HS was observed. The comparison of reverse osmosis isolates from surface waters collected during fall 1999 and spring 2000 from five Scandinavian sites yielded, in all cases, higher PhiDelta for the spring samples. For the aquatic sampling sites Hietajarvi and Birkenes, PhiDelta even exceeded values of 0.6%, which were found to be typical for terrestrial or soil water material. Investigation of the excitation wavelength dependence of PhiDelta in the spectral range 355-550 nm yielded different spectral shapes for aquatic HS and "non-aquatic" HS, respectively. On the basis of these excitation spectra, 1(O2) production rates were calculated for eight representative HS. PMID:14993944

  8. FLUORESCENCE CHARACTERIZATION OF IHSS HUMIC SUBSTANCES: TOTAL LUMINESCENCE SPECTRA WITH ABSORBANCE CORRECTION. (R822251)

    EPA Science Inventory

    Total luminescence spectroscopy was applied to the fluorescence characterization of humic substances obtained from the International Humic Substances Society (IHSS). Results show that total luminescence spectra, represented as excitation-emission matrices (EEMs), may be used to d...

  9. QUANTITATIVE FOURIER TRANSFORM INFRARED SPECTROSCOPIC INVESTIGATION OF HUMIC SUBSTANCE FUNCTIONAL GROUP COMPOSITION

    EPA Science Inventory

    Infrared (IR) spectroscopy has been widely used for the structural investigation of humic substances. Although Fourier Transform Infrared (FTIR) instrumentation has been available for sometime, relatively little work with these instruments has been reported for humic substances,...

  10. TCE adsorption by GAC preloaded with humic substances

    SciTech Connect

    Kilduff, J.E.; Karanfil, T.; Weber, W.J. Jr.

    1998-05-01

    Adsorption of trichloroethylene (TCE) by activated carbon preloaded with humic and fulvic acids was studied under several conditions in completely mixed batch systems. The authors investigated how molecular weight and molecular-weight distribution of preloaded humic substances affected subsequent adsorption of TCE. The capacity of carbon to adsorb TCE was most greatly reduced in carbon that was preloaded with humic acid components having molecular weights less than about 1,400 g/mol as polystyrene sulfonate. The adsorption capacity was greatly reduced in carbon that was preloaded with whole humic mixtures in which lower molecular weights predominated. The energy distributions of adsorbent indicate that preloaded compounds preferentially occupy high-energy sites, making them inaccessible to subsequently encountered TCE.

  11. Molecular weight, polydispersity, and spectroscopic properties of aquatic humic substances

    USGS Publications Warehouse

    Chin, Y.-P.; Aiken, G.; O'Loughlin, E.

    1994-01-01

    The number- and weight-averaged molecular weights of a number of aquatic fulvic acids, a commercial humic acid, and unfractionated organic matter from four natural water samples were measured by high-pressure size exclusion chromatography (HPSEC). Molecular weights determined in this manner compared favorably with those values reported in the literature. Both recent literature values and our data indicate that these substances are smaller and less polydisperse than previously believed. Moreover, the molecular weights of the organic matter from three of the four natural water samples compared favorably to the fulvic acid samples extracted from similar environments. Bulk spectroscopic properties of the fulvic substances such as molar absorptivity at 280 nm and the E4/E6 ratio were also measured. A strong correlation was observed between molar absorptivity, total aromaticity, and the weight average molecular weights of all the humic substances. This observation suggests that bulk spectroscopic properties can be used to quickly estimate the size of humic substances and their aromatic contents. Both parameters are important with respect to understanding humic substance mobility and their propensity to react with both organic and inorganic pollutants. ?? 1994 American Chemical Society.

  12. Lanthanide--humic substances complexation. II. Calibration of humic ion-binding model V.

    PubMed

    Sonke, Jeroen E

    2006-12-15

    The experimental complexation of the lanthanides (Sc, Y, and rare earth elements) with Suwannee river fulvic acid, Leonardite coal humic acid, and Elliot soil humic acid is described with Humic Ion-Binding Model V. The fitted intrinsic equilibrium constants for metal-proton exchange, pKMHA, for Eu3+ are similar to previously published experimental fits, and linear free energy relationship (LFER) estimated values. The experimentally observed lanthanide contraction effect in REE-humic complex stability is reflected in the gradual decrease in pKMHA from La to Lu. In Model V, a decrease in pKMHA from La to Lu indicates an increase in complex stability. Fitted pKMHA values for heavy REE are lower than those estimated by LFERs. Consequently, REE fractionation by humic substances complexation could be more pronounced than previously thought. Recommended pKMHA values for lanthanide-fulvic and -humic acid complexation are derived by superimposing the fitted trends in pKMHA for all REE, i.e., the decrease in pKMHA from La to Lu, on the average Eu pKMHA value for all literature datasets. These results will allow modeling assessments of organic matter induced REE fractionation in aquatic environments, taking into account changes in pH, ionic strength, and ion competition. A simulation of dissolved REE speciation in an average world river suggests that organic matter outcompetes carbonate complexation, even under alkaline conditions. PMID:17256484

  13. Application of a membrane model to the sorptive interactions of humic substances.

    PubMed Central

    Wershaw, R L

    1989-01-01

    Humic substances, the dark-colored, natural organic polyelectrolytes that are found in practically all soils, sediments, and natural water, strongly interact with both inorganic and organic pollutants. Inorganic cationic species generally undergo complexation reactions with humic substances. The binding of cations, such as cupric ions, by humic substances often markedly reduces their toxicity to aquatic organisms. Some inorganic anionic species, in the presence of metal ions, are sorbed by humic substances. In these instances the metal ions appear to form bridges between the humic substances and the anions. Several different types of interactions take place between organic compounds and humic materials. Hydrophobic organic species partition into either insoluble or soluble humic substances. The insoluble humic substances will remove hydrophobic organic compounds from the aqueous phase, thereby rendering them less mobile. However, soluble humic substances will solubilize hydrophobic organics, increasing their mobility. Other types of interactions between humic substances and organic compounds, such as adsorption and ion exchange, also have been observed. These various interactions between humic substances and pollutants are important in governing their fate and movement in natural water systems, and, for this reason, a detailed understanding of the mechanisms of the interaction is important. A recently developed membrane model of the structure of humic substances is described; this model enables one to better understand the physical-chemical properties of these materials. Images FIGURE 2. FIGURE 3. PMID:2533555

  14. Application of a membrane model to the sorptive interactions of humic substances

    SciTech Connect

    Wershaw, R.L. )

    1989-11-01

    Humic substances, the dark-colored, natural organic polyelectrolytes that are found in practically all soils, sediments, and natural water, strongly interact with both inorganic and organic pollutants. Inorganic cationic species generally undergo complexation reactions with humic substances. The binding of cations, such as cupric ions, by humic substances often markedly reduces their toxicity to aquatic organisms. Some inorganic anionic species, in the presence of metal ions, are sorbed by humic substances. In these instances the metal ions appear to form bridges between the humic substances and the anions. Several different types of interactions take place between organic compounds and humic materials. Hydrophobic organic species partition into either insoluble or soluble humic substances. The insoluble humic substances will remove hydrophobic organic compounds from the aqueous phase, thereby rendering them less mobile. However, soluble humic substances will solubilize hydrophobic organics, increasing their mobility. These various interactions between humic substances and pollutants are important in governing their fate and movement in natural water systems, and, for this reason, a detailed understanding of the mechanisms of the interaction is important. A recently developed membrane model of the structure of humic substances is described.

  15. Conformational arrangement of dissolved humic substances. Influence of solution composition on association of humic molecules

    SciTech Connect

    Conte, P.; Piccolo, A.

    1999-05-15

    The characteristics and quantity of humic substances greatly affects the environmental fate of organic pollutants in soils and natural waters. The authors studied the conformational changes of humic and fulvic acids of different chemical nature by high-pressure size-exclusion chromatography (HPSEC) after dissolution in mobile phases differing in composition but constant in ionic strength. Modification of a neutral mobile phase by addition of methanol, hydrochloric acid, and acetic acid produced, in the order, a progressive decrease in molecular size. Size diminishing was shown by increasingly larger elution volumes at a refractive index detector and by concomitant reductions of peaks absorbance at a UV-vis detector. The decrease of molecular absorptivity (the phenomenon of hypochromism) proved that size reduction of dissolved humic substances was due more to disruption of an only apparent high-molecular-size arrangement into several smaller molecular associations than to coiling down of a macromolecular structure. The most significant conformational changes occurred in acidic mobile phases where hydrogen bondings formation was induced, suggesting that the large and easily disruptable humic conformation was held together predominantly by weak hydrophobic forces.

  16. Fluorescence characterization of IHSS humic substances: Total luminescence spectra with absorbance correction

    SciTech Connect

    Mobed, J.J.; Hemmingsen, S.L.; Autry, J.L.; Mcgown, L.B.

    1996-10-01

    Total luminescence spectroscopy was applied to the fluorescence characterization of humic substances obtained from the International Humic Substances Society (IHSS). Results show that total luminescence spectra, represented as excitation-emission matrices (EEMs), may be used to discriminate between soil-derived and aquatic-derived IHSS humic substances and between humic and fulvic acids derived from the same source (soil or aquatic). Ionic strength in the range of 0-1 M KCl and humic substance concentration in the range 5-100 mg/L had little effect on the fluorescence spectral characteristics of the humic substances, while pH had significant effects as expected. Absorbance correction was shown to be essential for accurate representation and comparison of the EEMs of the humic substances at high concentrations. 16 refs., 5 figs., 3 tabs.

  17. **1**5N-NMR INVESTIGATION OF HYDROXYLAMINE DERIVATIZED HUMIC SUBSTANCES.

    USGS Publications Warehouse

    Thorn, Kevin A.; Arterburn, Jeffrey B.; Mikita, Michael A.

    1986-01-01

    Humic substances are the most abundant naturally occurring refactory organic compounds in soils and water. They have a broad range of physical, chemical and physiological properties. In soils, humic substances contribute to the cation exchange capacity, help maintain the physical structure, and play a role in plant growth and nutrition. In aquatic systems, humic substances serve to regulate the levels of inorganic constituents, yield trihalomethanes upon chlorination, and transport or concentrate organic and inorganic pollutants. The oxygen containing functional groups of humic and fulvic acids are believed to play a key role in the chemical properties of humic substances. This study was undertaken to gain additional information on the specific types of oxygen functionalities in humic substances. Since the analysis of hydroxyl moieties had been earlier established, we focused our attention on the analysis of ketone and aldehyde functional groups in humic substances.

  18. Removal of humic substances from water by brown coal sorbents

    SciTech Connect

    E.V. Veprikova; A.V. Rudkovskii; M.L. Shchipko

    2007-12-15

    Brown coal sorption materials with high activity toward humic substances were prepared using a larger scale laboratory unit with a spouted-bed system. The effect of thermal treatment conditions on the sorption properties of these materials was studied. It was found that the sorption activity of the resulting samples toward humates was closely related to the limiting sorption volume of the materials with respect to benzene.

  19. Interactions of dissolved humic substances with oppositely charged fluorescent dyes for tracer techniques.

    PubMed

    Hafuka, Akira; Ding, Qing; Yamamura, Hiroshi; Yamada, Koji; Satoh, Hisashi

    2015-11-15

    To investigate interactions between oppositely charged fluorescent dyes and dissolved humic substances, fluorescence quenching of fluorescein and rhodamine 6G with dissolved humic substances was performed. Binding coefficients were obtained by the Stern-Volmer equation. The fluorescence of rhodamine 6G was largely quenched by the addition of humic acid and a non-linear Stern-Volmer plot was obtained. This strong quenching may be caused by the electrostatic interaction between cationic rhodamine 6G and humic acid and strengthened by the hydrophobic repulsion. In contrast, the quenching and interactive effects of dissolved humic substances for fluorescein were relatively weak. PMID:26318652

  20. Formation of Humic Substances in Weathered MSWI Bottom Ash

    PubMed Central

    Zhang, Haixia; Shimaoka, Takayuki

    2013-01-01

    The study aimed at evaluating the humic substances (HSs) content from municipal solid waste incinerator (MSWI) bottom ash and its variation with time and the effect of temperature on HSs formation. The process suggested by IHSS was applied to extract HSs from two different bottom ash samples, and the extracted efficiency with NaOH and Na4P2O7 was compared. MSWI bottom ash samples were incubated at 37°C and 50°C for 1 year. HSs and nonhumic substances were extracted from the bottom ash sample with different incubated period by 0.1 M NaOH/Na4P2O7. Results show that the rate of humic acid formation increased originally with incubation time, reached a maximum at 12th week under 37°C and at 18th week under 50°C, and then decreased with time. More humic acid in MSWI bottom ash was formed under 50°C incubated condition compared with that incubated under 37°C. Also, the elemental compositions of HSs extracted from bottom ash are reported. PMID:23844394

  1. Interactions of Tc(IV) with humic substances.

    PubMed

    Boggs, Mark A; Minton, Travis; Dong, Wenming; Lomasney, Samuel; Islam, Mohammed R; Gu, Baohua; Wall, Nathalie A

    2011-04-01

    To understand the key processes affecting 99Tc mobility in the subsurface and help with the remediation of contaminated sites, the binding constants of several humic substances (humic and fulvic acids) with Tc(IV) were determined, using a solvent extraction technique. The novelty of this paper lies in the determination of the binding constants of the complexes formed with the individual species TcO(OH)+ and TcO(OH)2(0). Binding constants were found to be 6.8 and between 3.9 and 4.3, for logβ1,-1,1 and logβ1,-2,1, respectively; these values were little modified by a change of ionic strength, in most cases, between 0.1 and 1.0 M, nor were they by the nature and origin of the humic substances. Modeling calculations based on these show TcO(OH)-HA to be the predominant complex in a system containing 20 ppm HA and in the 4-6 pH range, whereas TcO(OH)2(0) and TcO(OH)2-HA are the major species, in the pH 6-8 range. PMID:21366306

  2. Formation of humic substances in weathered MSWI bottom ash.

    PubMed

    Zhang, Haixia; Shimaoka, Takayuki

    2013-01-01

    The study aimed at evaluating the humic substances (HSs) content from municipal solid waste incinerator (MSWI) bottom ash and its variation with time and the effect of temperature on HSs formation. The process suggested by IHSS was applied to extract HSs from two different bottom ash samples, and the extracted efficiency with NaOH and Na4P2O7 was compared. MSWI bottom ash samples were incubated at 37°C and 50°C for 1 year. HSs and nonhumic substances were extracted from the bottom ash sample with different incubated period by 0.1 M NaOH/Na₄P₂O₇. Results show that the rate of humic acid formation increased originally with incubation time, reached a maximum at 12th week under 37°C and at 18th week under 50°C, and then decreased with time. More humic acid in MSWI bottom ash was formed under 50°C incubated condition compared with that incubated under 37°C. Also, the elemental compositions of HSs extracted from bottom ash are reported. PMID:23844394

  3. Interactions of Tc(IV) with humic substances

    SciTech Connect

    Boggs, M. A.; Minton, Travis; Lomasney, Samuel; Islam, Mohammed; Dong, Wenming; Gu, Baohua; Wall, Nathalie

    2011-01-01

    To understand the key processes affecting 99Tc mobility in the subsurface and help with the remediation of contaminated sites, the binding constants of several humic substances (humic and fulvic acids) with Tc(IV) were determined, using a solvent extraction technique. The novelty of this paper lies in the determination of the binding constants of the complexes formed with the individual species TcO(OH)+ and TcO(OH)20. Binding constants were found to be 6.8 and between 3.9 and 4.3, for log 1, 1,1 and log 1,-2,1, respectively; these values were little modified by a change of ionic strength, in most cases, between 0.1 M to 1.0 M, nor were they by the nature and origin of the humic substances. Modeling calculations based on these show TcO(OH)-HA to be the predominant complex in a system containing 20 ppm HA and in the 4-6 pH range, while TcO(OH)20 and TcO(OH)2-HA are the major species, in the pH 6-8 range.

  4. Effects of humic substances on the bioconcentration of polycyclic aromatic hydrocarbons: Correlations with spectroscopic and chemical properties of humic substances

    SciTech Connect

    Haitzer, M.; Abbt-Braun, G.; Traunspurger, W.; Steinberg, C.E.W.

    1999-12-01

    The presence of dissolved humic substances (HS, fulvic and humic acids) generally reduces the uptake of hydrophobic organic compounds into aquatic organisms. The extent of this effect depends both on the concentration and on the origin of the HS. The aim of this study was to investigate the role of qualitative differences between HS from different origins. The effects of seven different HS on the bioconcentration of pyrene and benzo[a]pyrene (BaP) in the nematode Caenorhabditis elegans were related to the spectroscopic and chemical properties of the HS. The effect of each humic material on the bioconcentration of pyrene or BaP was quantified as a biologically determined partition coefficient K{sub DOC}. The authors observed significant linear relationships between K{sub DOC} and the atomic H/C ratio, the specific absorptivity at 254 nm, the content of aromatic carbons as determined by {sup 13}C nuclear magnetic resonance spectroscopy, the copper-complexing capacity, the content of phenolic OH groups, and the molecular weight of the HS. There was no discernible relationship of K{sub DOC} with the atomic (N + O)/C ratio, an indicator of the polarity of HS. Taken together, their results show that the variability in the effects of HS from different origins could be related to variations in bulk properties of the HS. Parameters describing the aromaticity of the humic materials seemed to be most useful for estimating effects of HS on the bioconcentration of pyrene and BaP.

  5. Effects of humic substances on the bioconcentration of polycyclic aromatic hydrocarbons: Correlations with spectroscopic and chemical properties of humic substances

    USGS Publications Warehouse

    Haitzer, M.; Abbt-Braun, G.; Traunspurger, W.; Steinberg, C.E.W.

    1999-01-01

    The presence of dissolved humic substances (HS, fulvic and humic acids) generally reduces the uptake of hydrophobic organic compounds into aquatic organisms. The extent of this effect depends both on the concentration and on the origin of the HS. The aim of this study was to investigate the role of qualitative differences between HS from different origins. The effects of seven different HS on the bioconcentration of pyrene and benzo[a]pyrene (BaP) in the nematode Caenorhabditis elegans were related to the spectroscopic and chemical properties of the HS. The effect of each humic material on the bioconcentration of pyrene or BaP was quantified as a 'biologically determined' partition coefficient K(DOC). We observed significant linear relationships between K(DOC) and the atomic H/C ratio, the specific absorptivity at 254 nm, the content of aromatic carbons (as determined by 13C nuclear magnetic resonance spectroscopy, the copper-complexing capacity, the content of phenolic OH groups, and the molecular weight of the HS. There was no discernible relationship of K(DOC) with the atomic (N + O)/C ratio, an indicator of the polarity of HS. Taken together, our results show that the variability in the effects of HS from different origins could be related to variations in bulk properties of the HS. Parameters describing the aromaticity of the humic materials seemed to be most useful for estimating effects of HS on the bioconcentration of pyrene and BaP.

  6. Binding of pyrene to aquatic and commercial humic substances: The role of molecular weight and aromaticity

    USGS Publications Warehouse

    Chin, Y.-P.; Aiken, G.R.; Danielsen, K.M.

    1997-01-01

    The binding of pyrene to a number of humic substances isolated from various aquatic sources and a commercial humic acid was measured using the solubility enhancement method. The humic materials used in this study were characterized by various spectroscopic and liquid chromatography methods. A strong correlation was observed between the pyrene binding coefficient, K(doc), and the molecular weights, molar absorptivities at 280 nm, and aromaticity of the aquatic humic substances. Binding of pyrene to the commercial humic acid, however, was significantly stronger and did not obey the relationships observed between K(doc) and the chemical properties of the aquatic humic substrates. These results suggest that the molecular weight and the aromatic content of the humic substrates exert influences on the binding of nonpolar and planar aromatic molecules and that the physicochemical properties of both humic materials and organic solutes are important in controlling the speciation of nonpolar organic contaminants in natural waters.

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

    USGS Publications Warehouse

    Malcolm, R.L.

    1990-01-01

    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 ?? 13C 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 compositions of saccharide, phenolic, methoxyl, aromatic, hydrocarbon, amino acid and nitrogen moieties.

  8. Reaction of vanadate with aquatic humic substances: An ESR and {sup 51}V NMR study

    SciTech Connect

    Lu, Xi.; Johnson, W.D.; Hook, J.

    1998-08-01

    Electron spin resonance (ESR) spectroscopy and {sup 51}V nuclear magnetic resonance (NMR) spectroscopy have been used to study the interaction of vanadate with aqueous solutions of humic substances (HS) at different pH values and at different concentrations. Under acidic pH conditions, ESR spectra show that humic substances reduce vanadium(V) to vanadium(IV) without further reduction to vanadium(III). The reduced vanadium(IV) ion is bound to oxygen donor atoms, probably at carboxylic acid sites in the humic substances. {sup 51}V NMR spectra show that the VO{sub 2}{sup +} cation is immediately reduced and that the decavanadate cation decomposes to the VO{sub 2}{sup +} cation prior to reduction. The overall rate of reduction depends on both concentration and pH. There is no reduction above pH 6, which suggests that the standard reduction potential of humic substances is about +0.65 V. Near pH 7, vanadate is stabilized by binding to humic substances. As the concentration of humic substances increases, the total vanadium NMR signal intensity decreases. This is due to the quadrupolar nature of the {sup 51}V nucleus that, when bound to humic substances, is invisible in NMR measurements. Quantitative models applied to intensity changes show that the vanadate monomer forms HS0V(V) complexes. The formation equilibrium constant is estimated to be 108 M{sup {minus}1}. At pH above 9, NMR signals appear at {minus}623.6 and at {minus}763.2 ppm when humic substances are added to vanadate solution. The intensities of the signals increase with increasing pH and with increasing concentration of humic substances. These signals appear to be associated with peroxyvanadate anions, which are not bound to humic substances.

  9. Effect of soil invertebrates on the formation of humic substances under laboratory conditions

    NASA Astrophysics Data System (ADS)

    Frouz, J.; Li, X.; Brune, A.; Pizl, V.; Abakumov, E. V.

    2011-08-01

    The complete polymerization of phenols and proteins (one of the processes involved in the formation of humic substances) was explained. It was shown that fly ( Bibio marci) larvae and earthworms ( Aporrectodea caliginosa) participate in the complete polymerization of phenols and proteins. In a laboratory experiment, invertebrates participated in the degradation of organic matter and the synthesis of humic substances, which was proved in experiments with 14C-labeled phenols and proteins. The same organic substances (phenols and proteins) without the impact of invertebrates were used as the control substances. The distributions of the 14C isotope in alkaline extracts separated by solubility in acids (humic and fulvic acids) was compared to those of the control substances. The portion of the 14C isotope in the humic acids in the excrements of Bibio marci was higher than that in the control substances. The content of 14C-labeled humic substances in the excrements of the earthworm Aporrectodea caliginosa exceeded the control values only in the experiment with proteins. When clay material was added to the organic substances, the portion of the 14C isotope in the humic acids increased in both experiments with phenols and proteins. When these substrates passed through the digestive tracts of the invertebrates, the polymerization of organic substances and the inclusion of proteins and phenols into humic acids occurred.

  10. The contribution of humic substances to the acidity of colored natural waters

    USGS Publications Warehouse

    Oliver, B.G.; Thurman, E.M.; Malcolm, R.L.

    1983-01-01

    An operationally defined carboxyl content of humic substances extracted from rivers, streams, lakes, wetlands, and groundwaters throughout the United States and Canada is reported. Despite the diversity of the samples, only small variations were observed in this humic carboxyl content. The dissociation behavior of two combined fulvic/humic acid extracts was studied and it was found that the dissociation of the humics varied in a predictable manner with pH. Using a carboxyl content of 10 ??eq/ mg humic organic carbon, and mass action quotient calculated from sample pH, the ionic balances of three highly colored Nova Scotia rivers were estimated. ?? 1983.

  11. Factors to be considered in the isolation and characterization of aquatic humic substances

    NASA Astrophysics Data System (ADS)

    Malcolm, Ronald L.

    A detailed procedure using XAD-8 resin is presented for the isolation of dissolved fulvic acids and humic acids from water. The procedure entails pressure filtration to remove suspended sediment, sorption of humic substances onto XAD-8 resin at pH 2, desorption of humic substances in base, fulvic/humic separation at pH 1, desalting on XAD-8 resin, hydrogen saturation on cation exchange resin, and freeze-drying. Careful attention must be given to thorough resin cleaning and many procedural details in order to obtain relatively ash-free humic isolates. The equipment required for the procedure is expensive and the method is time consuming, but no other isolation method is known to produce quantitative and unaltered humic isolates from water. The procedure can be used to isolate small quantities (less than 100 mg) of humic substances from water, or it can be scaled to produce large quantities (100 g or more) of humic substances from water. Humic substances may be characterized by several methods. The more useful traditional characterization methods include elemental analysis, ash content, functional group analysis by titration and infrared spectroscopy, and molecular weight analysis. The new characterization methods of 1H-NMR, 13C-NMR, pyrolysis/mass spectroscopy, amino acid analysis, saccharide analysis, and carbon isotopic analysis (14C and 13C content) are usually more definitive than traditional characterizations.

  12. Oxidation of humic substances supports denitrification reactions in agricultural soils.

    NASA Astrophysics Data System (ADS)

    van Trump, J. I.; Coates, J. D.

    2007-12-01

    Humic substances (HS) are a ubiquitous, recalcitrant, and diverse class of compounds arising from degradation and condensation of plant and microbial biopolymers. Many bacteria oxidize hydroquinones within humic substances to their quinone analogs, providing electrons for respiratory processes such as nitrate reduction. Microbial hydroquinone oxidation contributes to the redox state of HS and supports denitrification, which may be of import to agricultural soils where nitrate retention is critical and HS are prevalent. Most probable number counts were performed on soils collected from a Nebraska farm, with the model humic hydroquinone 2,6- anthrahydroquinone disulfonate (AHDS) serving as an electron donor and nitrate as the electron acceptor. Results indicated that AHDS oxidizing, nitrate reducing bacteria were present in soils from bluegrass fields (104 cells/g) and aspen groves (106 cells/g), as well as in plots of corn (106 cells/g), and soybean treated (106 cells/g) and un-treated (105 cells/g) with pig slurry. These results demonstrate that microorganisms participating in the proposed metabolism are prevalent within agricultural soils. Upflow glass columns were constructed, containing a support matrix of glass beads amended with 10% w/w soil from the corn plot previously mentioned. All columns were subjected to a continual flow of phosphate-buffered water amended with sodium nitrate. Above the point source for nitrate injection, phosphate-buffered water containing electron donor treatments were continually injected. The impacts of electron donor treatments (no donor, oxidized HS, reduced HS, and acetate) on denitrification and other geochemical parameters were observed. Column studies were able to resolve effects of electron donor treatment both spatially as a function of distance from the injection point source, and temporally, as a function of time of donor treatment. Four sample ports in each column were routinely analyzed for concentrations of nitrate

  13. XANES studies of oxidation states of sulfur in aquatic and soil humic substances

    SciTech Connect

    Xia, K.; Weesner, F.; Bleam, W.F.; Helmke, P.A.; Bloom, P.R.; Skyllberg, U.L.

    1998-09-01

    Sulfur K-edge x-ray absorption near-edge structure spectroscopy (XANES) was used to identify multiple organic S oxidation states in aquatic and soil humic substances. The XANES results suggest that S in humic substances exists in four major oxidation groups similar to sulfate ester, sulfonate, sulfoxide, and thiol-sulfide. Thiol S cannot be separated from sulfide X and must be considered as a single thiol-sulfide peak. The second derivative spectra suggest the existence of thiophene and sulfone S. The relative quantities of each major S form in humic samples were estimated based on the integrated cross section of each s {r_arrow} p transition peak corresponding to different S oxidation states in the S K-edge XANES spectra. The XANES results of the four humic samples used in this study appear to reflect the environmental settings where the humic substances originally formed. The percentage of the most reduced organic S (thiol-sulfide and possibly thiophene) in humic substances follows the sequence:aquatic samples > organic soil sample > mineral soil sample. The percentage of most oxidized S (sulfate group) was the greatest in the humic substance from a mineral soil and the lowest in the aquatic humic substances.

  14. Natural carbon-based dots from humic substances

    NASA Astrophysics Data System (ADS)

    Dong, Yongqiang; Wan, Lisi; Cai, Jianhua; Fang, Qingqing; Chi, Yuwu; Chen, Guonan

    2015-05-01

    For the first time, abundant natural carbon-based dots were found and studied in humic substances (HS). Four soluble HS including three humic acids (HA) from different sources and one fulvic acids (FA) were synthetically studied. Investigation results indicate that all the four HS contain large quantities of Carbon-based dots. Carbon-based dots are mainly small-sized graphene oxide nano-sheets or oxygen-containing functional group-modified graphene nano-sheets with heights less than 1 nm and lateral sizes less than 100 nm. Carbon-based nanomaterials not only contain abundant sp2-clusters but also a large quantity of surface states, exhibiting unique optical and electric properties, such as excitation-dependent fluorescence, surface states-originated electrochemiluminescence, and strong electron paramagnetic resonance. Optical and electric properties of these natural carbon-based dots have no obvious relationship to their morphologies, but affected greatly by their surface states. Carbon-based dots in the three HS have relative high densities of surface states whereas the FA has the lowest density of surface states, resulting in their different fluorescence properties. The finding of carbon-based dots in HS provides us new insight into HS, and the unique optical properties of these natural carbon-based dots may give HS potential applications in areas such as bio-imaging, bio-medicine, sensing and optoelectronics.

  15. Production of humic substances through coal-solubilizing bacteria

    PubMed Central

    Valero, Nelson; Gómez, Liliana; Pantoja, Manuel; Ramírez, Ramiro

    2014-01-01

    In this paper, the production of humic substances (HS) through the bacterial solubilization of low rank coal (LRC) was evaluated. The evaluation was carried out by 19 bacterial strains isolated in microenvironments with high contents of coal wastes. The biotransformed LRC and the HS produced were quantified in vitro in a liquid growth medium. The humic acids (HA) obtained from the most active bacterial strain were characterized via elemental composition (C, H, N, O), IR analyses, and the E4/E6 ratio; they were then compared with the HA extracted chemically using NaOH. There was LRC biotransformation ranged from 25 to 37%, and HS production ranged from 127 to 3100 mg.L−1. More activity was detected in the isolated strains of Bacillus mycoides, Microbacterium sp, Acinetobacter sp, and Enterobacter aerogenes. The HA produced by B. mycoides had an IR spectrum and an E4/E6 ratio similar to those of the HA extracted with NAOH, but their elemental composition and their degree of aromatic condensation was different. Results suggest that these bacteria can be used to exploit the LRC resulting from coal mining activities and thus produce HS in order to improve the content of humified organic matter in soils. PMID:25477925

  16. Natural carbon-based dots from humic substances

    PubMed Central

    Dong, Yongqiang; Wan, Lisi; Cai, Jianhua; Fang, Qingqing; Chi, Yuwu; Chen, Guonan

    2015-01-01

    For the first time, abundant natural carbon-based dots were found and studied in humic substances (HS). Four soluble HS including three humic acids (HA) from different sources and one fulvic acids (FA) were synthetically studied. Investigation results indicate that all the four HS contain large quantities of Carbon-based dots. Carbon-based dots are mainly small-sized graphene oxide nano-sheets or oxygen-containing functional group-modified graphene nano-sheets with heights less than 1 nm and lateral sizes less than 100 nm. Carbon-based nanomaterials not only contain abundant sp2-clusters but also a large quantity of surface states, exhibiting unique optical and electric properties, such as excitation-dependent fluorescence, surface states-originated electrochemiluminescence, and strong electron paramagnetic resonance. Optical and electric properties of these natural carbon-based dots have no obvious relationship to their morphologies, but affected greatly by their surface states. Carbon-based dots in the three HS have relative high densities of surface states whereas the FA has the lowest density of surface states, resulting in their different fluorescence properties. The finding of carbon-based dots in HS provides us new insight into HS, and the unique optical properties of these natural carbon-based dots may give HS potential applications in areas such as bio-imaging, bio-medicine, sensing and optoelectronics. PMID:25944302

  17. Electrocoagulation treatment of peat bog drainage water containing humic substances.

    PubMed

    Kuokkanen, V; Kuokkanen, T; Rämö, J; Lassi, U

    2015-08-01

    Electrocoagulation (EC) treatment of 100 mg/L synthetic wastewater (SWW) containing humic acids was optimized (achieving 90% CODMn and 80% DOC removal efficiencies), after which real peat bog drainage waters (PBDWs) from three northern Finnish peat bogs were also treated. High pollutant removal efficiencies were achieved: Ptot, TS, and color could be removed completely, while Ntot, CODMn, and DOC/TOC removal efficiencies were in the range of 33-41%, 75-90%, and 62-75%, respectively. Al and Fe performed similarly as the anode material. Large scale experiments (1 m(3)) using cold (T = 10-11 °C) PBDWs were also conducted successfully, with optimal treatment times of 60-120 min (applying current densities of 60-75 A/m(2)). Residual values of Al and Fe (complete removal) were lower than their initial values in the EC-treated PBDWs. Electricity consumption and operational costs in optimum conditions were found to be low and similar for all the waters studied: 0.94 kWh/m(3) and 0.15 €/m(3) for SWW and 0.35-0.70 kWh/m(3) and 0.06-0.12 €/m(3) for the PBDWs (large-scale). Thus, e.g. solar cells could be considered as a power source for this EC application. In conclusion, EC treatment of PBDW containing humic substances was shown to be feasible. PMID:25973580

  18. Humic substances-enhanced electroremediation of heavy metals contaminated soil.

    PubMed

    Bahemmat, Mahdi; Farahbakhsh, Mohsen; Kianirad, Mehran

    2016-07-15

    The effects of catholyte conditioning and the use of humic acids (HAs) and fulvic acids (FAs) as chelating agents to improve electrokinetic (EK) remediation efficiency were investigated using a real and highly contaminated soil. By applying a constant voltage (2.0V/cm) to the soil, pH and current changes and heavy metals (HMs) concentration were investigated through a range of durations and positions. The observations demonstrated that both catholyte conditioning with 0.1N HNO3 and using humic substances (HSs) enhance remediation efficiency. After 20 days of EK treatment, the removal efficiency of HMs in HS-enhanced EK remediation was about 2.0-3.0 times greater than when unenhanced. The quantity of HMs moving toward the cathode exceeded the anode, from which it could be reasonably inferred that most negatively charged HM-HS complexes were moved by electroosmotic forces. Further, free HM cations and positively charged complexed HMs migrated to the catholyte compartment by electromigration. The results obtained in this study, demonstrate the suitability of HS-enhanced EK remediation in HMs contaminated soil. PMID:27058638

  19. NMR characterization and sorption behavior of agricultural and forest soil humic substances

    NASA Astrophysics Data System (ADS)

    Li, Chengliang; Berns, Anne E.; Séquaris, Jean-Marie; Klumpp, Erwin

    2010-05-01

    Humic substances are the predominant components of the organic matter in the terrestrial system, which are not only important for the physicochemical properties of soil but are also dominant factors for controlling the environmental behaviors and fates of some organic contaminants, such as hydrophobic compounds. Nonylphenol [4-(1-ethyl-1, 3 dimethylpentyl) phenol] (NP), a ubiquitous hydrophobic pollutant, has recently focused the attention owing to its endocrine disruptors property. Sorption behavior of NP on humic substances, which were isolated from agricultural and forest soils, was investigated by using the dialysis technique at room temperature. 14C-labeled NP was used to quantify the partitioning behavior. Humic substances were characterized by 13C Cross-Polarization/Magic-Angle-Spinning Nuclear Magnetic Resonance (CP/MAS NMR). The results showed that the partition parameters of NP on various humic acids were slightly different. Relationships between partition coefficients and the functional groups of humic substances identified by CP/MAS NMR were analyzed.

  20. Identifying trends for understanding the role of humic substances in the environmental behavior of radionuclides

    SciTech Connect

    Czerwinski, K.R.; Buckau, G.

    1999-07-01

    Humic substances are expected to have a major role in the environmental speciation of radionuclides. If the speciation of the radionuclide humic complex can be adequately modeled, predictions of its fate and transport may be possible. Additionally, humic substances have been shown to adsorb to a variety of mineral surfaces. The humic coated surfaces also interact with aqueous radionuclides, complicating environmental behavior. Studies indicate the importance of pH, ionic strength, and humic substance concentration in understanding the impact of humic substances on radionuclide speciation. However, values obtained to describe complexation or sorption vary and are difficult to compare and incorporate into existing geochemical codes due to variations in humic complexation models or concepts. This obscures intercomparison and the utility of the resulting values. This work shows results based on different concepts can be evaluated with the charge neutralization model, yielding similar stability constant values. The consistent stability constants found with the charge neutralization model can be used for intercomparison and identification of behavioral trends. A speciation calculation of a contaminated site using identified trends between humic and fulvic acid are given. The results yield good agreement between calculation and environmental observations. Laboratory experiments validate the identified trend. Comparisons between aquatic and sorb humic acid are presented and similarities useful for modeling are given.

  1. Soil humic substances hinder the propagation of prions

    NASA Astrophysics Data System (ADS)

    Leita, Liviana; Giachin, Gabriele; Margon, Alja; Narkiewicz, Joanna; Legname, Giuseppe

    2013-04-01

    capacity of clay minerals; however the contribution of soil organic components in adsorption has so far been neglected, as they represent a minor soil fraction on a weight basis. Among organic molecules, humic substances (HSs) are natural polyanions that result among the most reactive compounds in the soil and possess the largest specific surface area. Humic substances make up a large portion of the dark matter in humus and consist of heterogeneous mixtures of transformed biomolecules exhibiting a supramolecular structure. HSs are classified as humic acids (HAs), which are soluble only in alkaline solutions, and fulvic acids (FAs), which are soluble in both alkaline and acid solutions. The amphiphilic characteristics confer to HAs and FAs great versatility to interact with xenobiotics and reasonably also with prion proteins and/or prions too, leading to the formation of adducts with peculiar chemical and biophysical characteristics, thus affecting the transport, fixation and toxicity of prion. Results from our chemical, biophysical and biochemical investigation will be presented and results on anti-prion activity exerted by HAs and FAs will be provided, thus suggesting that amendment of contaminated soil with humic substances could be a strategy to contrast prion diffusion.

  2. EFFECTS OF ALUMINUM-INDUCED AGGREGATION ON THE FLUORESCENCE OF HUMIC SUBSTANCES. (R822251)

    EPA Science Inventory

    Aluminum-induced aggregates of terrestrial and aquatic humic acid standards from the International Humic Substances Society are shown to be fluorescent by means of a multiwavelength fluorescence anisotropy experiment in which the data was treated with a model for nonspherical ...

  3. Capillary Electrophoresis and Fluorescence Excitation-Emission Matrix Spectroscopy for Characterization of Humic Substances

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Capillary electrophoresis (CE) and fluorescence spectroscopy have been used in natural organic matter (NOM) studies. In this study, we characterized five fulvic acids, six humic acids and two unprocessed NOM samples obtained from the International Humic Substances Society (IHSS) using these two ana...

  4. Distinguishing Black Carbon from Biogenic Humic Substances in Soil Clay Fractions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most models of soil humic substances include a substantial component of aromatic carbon (C) either as the backbone of humic heteropolymers or as a significant component of supramolecular aggregates of degraded biopolymers. Here we report that most of the aromatic C in the clay fraction of three stud...

  5. Reconnaissance samplings and characterization of aquatic humic substances at the Yuma Desalting Test Facility, Arizona

    USGS Publications Warehouse

    Malcolm, R.L.; Wershaw, R. L.; Thurman, E.M.; Aiken, G.R.; Pinckney, D.J.; Kaakinen, J.

    1981-01-01

    Smectite clay minerals were found to be the principal compound on the surface of the cellulose-acetate, reverse-osmosis membranes at the Yuma Desalting Test Facility. These clay minerals were not present in the pumped ground water, but were blown into the conveyance canal from adjacent soils. Humic substances from the water and suspended sediments were associated with the clay films on the membrane, but no definitive results concerning their role in fouling were achieved. Microbial fouling is believed to be only a minor aspect of membrane fouling. Chemical and physical changes in humic substances were extensively studied at four points in the water-treatment process. Humic substances accounted for the largest component (over 25 percent) of organic constituents. Humic substances in the canal source water were similar to other aquatic humic substances present in natural waters. During the treatment process, these substances are brominated and decolorized. The effect of these halogenated humic substances on membrane fouling is unclear, but their presence in the reverse-osmosis product water and reverse-osmosis reject brine, along with volatile trihalomethanes, has led to environmental concerns. (USGS)

  6. Effects of extracellular polymeric and humic substances on chlorpyrifos bioavailability to Chironomus riparius.

    PubMed

    Lundqvist, Anna; Bertilsson, Stefan; Goedkoop, Willem

    2010-04-01

    The role of sediment organic matter quality and quantity for chlorpyrifos bioavailability was studied in experiments with Chironomus riparius larvae and with four types of organic matter; (1) commercially available extracellular polymeric substances (EPS), (2) EPS produced by sediment microbes, (3) commercially available humic substances and, (4) humic substances extracted from a boreal lake. The effects of each type of organic matter were assessed at three concentrations. We used a (14)C-tracer approach to quantify uptake of chlorpyrifos in the larvae, and the partitioning of the insecticide within the microcosm. Carbon-normalised larval uptake was reduced both by EPS and humic substances. However, the reduction in uptake was much greater for EPS than for humic substances: uptake was reduced by 94 and 88% for commercial and complex EPS, and by 59 and 57% for commercial and complex humic substances, respectively. We also found differences in chlorpyrifos uptake, and sediment concentrations between treatments with commercially available and complex polymers, suggesting that minor differences in the quality of relatively simple organic molecules can affect contaminant behaviour in ecotoxicological studies. Passive uptake in dead controls was 40% of that in living larvae. Therefore, both passive and digestive uptake were important processes for chlorpyrifos uptake by larvae. Our results show that both EPS and humic substances affect chlorpyrifos bioavailability to sediment biota negatively and contribute to the understanding of the processes that regulate organic contaminant bioavailability in aquatic environments. PMID:19851864

  7. Humic substances as fully regenerable electron acceptors in recurrently anoxic environments

    NASA Astrophysics Data System (ADS)

    Klüpfel, Laura; Piepenbrock, Annette; Kappler, Andreas; Sander, Michael

    2014-03-01

    Humic substances form through the degradation of microbial and plant precursors, and make up a significant fraction of natural organic matter in terrestrial and aquatic environments. Humic substances are redox-active and can act as terminal electron acceptors in anaerobic microbial respiration. Reduced humic substances may become re-oxidized during aeration of temporarily anoxic systems, such as wetlands, sediments and many soils. If the transfer of electrons from anaerobic respiration through humic substances to oxygen is sustained over many redox cycles, it may competitively suppress electron transfer to carbon dioxide, and thereby lower the formation of methane in temporarily anoxic systems. Here, we monitor changes in the redox states of four chemically distinct dissolved humic substances over successive cycles of reduction by the bacterium Shewanella oneidensis MR-1 and oxidation by oxygen, in a series of laboratory experiments. We show that electron transfer to and from these substances is fully reversible and sustainable over successive redox cycles. We suggest that redox cycling of humic substances may largely suppress methane production in temporarily anoxic systems.

  8. Comparative studies of the reduction behavior of chromium(VI) by humic substances and their precursors

    SciTech Connect

    Nakayasu, Ken; Sasaki, Keiko; Tanaka, Shunitz; Nakamura, Hiroshi ); Fukushima, Masami )

    1999-06-01

    Hexavalent chromium (Cr[VI]) is reduced by dissolved organic carbons (DOCs) such as humic substances, tannic acid (TA), and gallic acid (GA). The kinetic constants and the resulting chemical species after the reduction were compared with each other. The kinetic constants for GA and TA, which are model precursors of humic substances, were two to three orders of magnitude larger than those for the humic substances when these kinetic constants were expressed as a function of the molar concentration of the reductive functional group (F[sub red]) in various DOCs. After the reduction of Cr(VI), the percentages of the species complexed with GA and TA were higher than those with the humic substances. This appears to be due to the formation of high molecular weight compounds by polymerization during the reduction of Cr(VI) and complexation of Cr(III) with the polymerized compounds. The UV-vis spectrophotometric data and gel permeation chromatography support this view.

  9. CAPILLARY ELECTROPHORESIS IN THE ANALYSIS OF HUMIC SUBSTANCES FACTS AND ARTIFACTS

    EPA Science Inventory

    Humic substances, extracted as mixtures from soil and surface waters according to their solubility in acids and bases, are relatively high-molecular-mass polyelectrolytes containing aromatic, aliphatic and heterocyclic subunits. The degree of ionization of their phenolic and carb...

  10. River-derived humic substances as iron chelators in seawater

    PubMed Central

    Krachler, Regina; Krachler, Rudolf F.; Wallner, Gabriele; Hann, Stephan; Laux, Monika; Cervantes Recalde, Maria F.; Jirsa, Franz; Neubauer, Elisabeth; von der Kammer, Frank; Hofmann, Thilo; Keppler, Bernhard K.

    2015-01-01

    The speciation of iron(III) in oxic seawater is dominated by its hydrolysis and sedimentation of insoluble iron(III)-oxyhydroxide. As a consequence, many oceanic areas have very low iron levels in surface seawater which leads to iron deficiency since phytoplankton require iron as a micronutrient in order to grow. Fortunately, iron solubility is not truly as low as Fe(III) solubility measurements in inorganic seawater would suggest, since oceanic waters contain organic molecules which tend to bind the iron and keep it in solution. Various iron-binding organic ligands which combine to stabilize dissolved iron have been detected and thoroughly investigated in recent years. However, the role of iron-binding ligands from terrestrial sources remains poorly constrained. Blackwater rivers supply large amounts of natural organic material (NOM) to the ocean. This NOM (which consists mainly of vascular plant-derived humic substances) is able to greatly enhance iron bioavailability in estuaries and coastal regions, however, breakdown processes lead to a rapid decrease of river-derived NOM concentrations with increasing distance from land. It has therefore been argued that the influence of river-derived NOM on iron biogeochemistry in offshore seawater does not seem to be significant. Here we used a standard method based on 59Fe as a radiotracer to study the solubility of Fe(III)-oxyhydroxide in seawater in the presence of riverine NOM. We aimed to address the question how effective is freshwater NOM as an iron chelator under open ocean conditions where the concentration of land-derived organic material is about 3 orders of magnitude smaller than in coastal regions, and does this iron chelating ability vary between NOM from different sources and between different size fractions of the river-borne NOM. Our results show that the investigated NOM fractions were able to substantially enhance Fe(III)-oxyhydroxide solubility in seawater at concentrations of the NOM ≥ 5

  11. Character of Humic Substances as a Predictor for Goethite Nanoparticle Reactivity and Aggregation.

    PubMed

    Vindedahl, Amanda M; Stemig, Melissa S; Arnold, William A; Penn, R Lee

    2016-02-01

    Natural organic matter (NOM) is ubiquitous in surface water and groundwater and interacts strongly with mineral surfaces. The details of these interactions, as well as their impacts on mineral surface reactivity, are not well understood. In this work, both the reactivity and aggregation of goethite (α-FeOOH) nanoparticles were quantified in the presence of well-characterized humic substances. Results from monitoring the kinetics of reductive degradation of 4-chloronitrobenzene (4-ClNB) by Fe(II) adsorbed onto the goethite nanoparticles with and without added humic substances demonstrates that, in all cases, humic substances suppressed Fe(II)-goethite reactivity. The ranking of the standards from the least to most inhibitive was Pahokee Peat humic acid, Elliot Soil humic acid, Suwannee River humic acid, Suwannee River NOM, Suwannee River fulvic acid I, Suwannee River fulvic acid II, and Pahokee Peat fulvic acid. Correlations between eight characteristics (molecular weight, carboxyl concentration, and carbon, oxygen, nitrogen, aliphatic, heteroaliphatic, and aromatic content) and 4-ClNB degradation rate constants were observed. Faster kinetic rates of reductive degradation were observed with increased molecular weight and nitrogen, carbon, and aromatic content, and slower rates were observed with increased carboxyl concentration and oxygen, heteroaliphatic, and aliphatic content. With these correlations, improved predictions of the reactivity of Fe(II)-goethite with pollutants based on properties of the humic substances are possible. PMID:26790005

  12. Investigating the mechanism of phenol photooxidation by humic substances.

    PubMed

    Golanoski, Kelli S; Fang, Shuo; Del Vecchio, Rossana; Blough, Neil V

    2012-04-01

    To probe the mechanism of the photosensitized loss of phenols by humic substances (HS), the dependence of the initial rate of 2,4,6-trimethylphenol (TMP) loss (R(TMP)) on dioxygen concentration was examined both for a variety of untreated as well as borohydride-reduced HS and C(18) extracts from the Delaware Bay and Mid-Atlantic Bight. R(TMP) was inversely proportional to dioxygen concentration at [O(2)] > 50 μM, a dependence consistent with reaction with triplet excited states, but not with (1)O(2) or RO(2). Modeling the dependence of R(TMP) on [O(2)] provided rate constants for TMP reaction, O(2) quenching, and lifetimes compatible with a triplet intermediate. Borohydride reduction significantly reduced TMP loss, supporting the role of aromatic ketone triplets in this process. However, for most samples, the incomplete loss of sensitization following borohydride reduction, as well as the inverse dependence of R(TMP) on [O(2)] for these samples, suggests that there remains another class of oxidizing triplet sensitizer, perhaps quinones. PMID:22394372

  13. Bromoform formation in ozonated groundwater containing bromide and humic substances

    SciTech Connect

    Cooper, W.J.; Amy, G.L.; Moore, C.A.; Zika, R.G.

    1986-01-01

    The effect of bromide ion, organic carbon concentration (natural aquatic humic substances), pH, and solar irradiation on the formation of bromoform in ozonated groundwater has been studied. The studies were conducted on four unique samples of groundwater taken from different regions of the Biscayne Aquifer in southern Florida. All other conditions being equal, increases in bromide ion concentrations resulted in increases in CHBr/sub 3/ formation. In three of the four samples, CHBr/sub 3/ formation decreased as the pH level increased from 5 to 9. The fourth sample exhibited an opposite trend whereby the CHBr/sub 3/ concentration increased with increasing pH. Bromoform concentration increased with increased O/sub 3/ concentration over an ozone dosage range of 3.4 to 6.7 mg/L. Ozonated samples placed in sunlight immediately after ozone addition showed a decrease in the formation of CHBr/sub 3/ presumably due to the photodecomposition of HOBr/OBr.

  14. Effect of humic substances on phosphorus removal by struvite precipitation.

    PubMed

    Zhou, Zhen; Hu, Dalong; Ren, Weichao; Zhao, Yuzeng; Jiang, Lu-Man; Wang, Luochun

    2015-12-01

    Humic substances (HS) are a major fraction of dissolved organic matters in wastewater. The effect of HS on phosphorus removal by struvite precipitation was investigated using synthetic wastewater under different initial pH values, Mg/P molar ratios and HS concentrations. The composition, morphology and thermal properties of harvested precipitates were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermo-gravimetric analysis (TGA), respectively. It showed that inhibition effect of HS reached its maximum value of 48.9% at pH 8.0, and decreased to below 10% at pH>9.0. The increase of Mg/P ratio enhanced phosphorus removal efficiency, and thus reduced the influence of HS on struvite precipitation. At pH 9.0, the inhibitory effect of initial HS concentration matched the modified Monod model with half maximum inhibition concentration of 356mgL(-1), and 29% HS was removed in conjunction with struvite crystallisation. XRD analysis revealed that the crystal form of struvite precipitates was changed in the presence of HS. The morphology of harvested struvite was transformed from prismatic to pyramid owing to the coprecipitation of HS on crystal surface. TGA results revealed that the presence of HS could compromise struvite purity. PMID:26151483

  15. Prion Protein Interaction with Soil Humic Substances: Environmental Implications

    PubMed Central

    Giachin, Gabriele; Narkiewicz, Joanna; Scaini, Denis; Ngoc, Ai Tran; Margon, Alja; Sequi, Paolo; Leita, Liviana; Legname, Giuseppe

    2014-01-01

    Transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative disorders caused by prions. Animal TSE include scrapie in sheep and goats, and chronic wasting disease (CWD) in cervids. Effective management of scrapie in many parts of the world, and of CWD in North American deer population is complicated by the persistence of prions in the environment. After shedding from diseased animals, prions persist in soil, withstanding biotic and abiotic degradation. As soil is a complex, multi-component system of both mineral and organic components, it is important to understand which soil compounds may interact with prions and thus contribute to disease transmission. Several studies have investigated the role of different soil minerals in prion adsorption and infectivity; we focused our attention on the interaction of soil organic components, the humic substances (HS), with recombinant prion protein (recPrP) material. We evaluated the kinetics of recPrP adsorption, providing a structural and biochemical characterization of chemical adducts using different experimental approaches. Here we show that HS act as potent anti-prion agents in prion infected neuronal cells and in the amyloid seeding assays: HS adsorb both recPrP and prions, thus sequestering them from the prion replication process. We interpreted our findings as highly relevant from an environmental point of view, as the adsorption of prions in HS may affect their availability and consequently hinder the environmental transmission of prion diseases in ruminants. PMID:24937266

  16. Covalent binding of aniline to humic substances and whole soil organic matter

    SciTech Connect

    Thorn, K.A.; Goldenberg, W.S.; Younger, S.J.

    1995-12-31

    Aromatic amines enter the environment from the chemical or microbial degradation of dyes, explosives, and the acylanilide, phenylcarbamate, and phenylurea classes of herbicides. One possible fate of aromatic amines in soils is covalent binding to naturally occurring organic matter. The binding of {sup 15}N-labelled aniline to the fulvic and humic acids extracted from an Elliot silt loam soil with and without catalysis by peroxidase or birnessite has been examined by a combination of liquid and solid state {sup 15}N NMR. In the absence of catalysts, aniline undergoes a complex series of nucleophilic addition reactions with the carbonyl functionality of the humic substances to form both heterocyclic and nonheterocyclic condensation products. In the presence of the catalysts, aniline undergoes free radical coupling reactions together with nucleophilic addition reactions with the humic substances. Reaction of aniline with the whole soil most closely resembled the noncatalyzed reactions with the humic substances, as determined by solid state {sup 15}N NMR.

  17. Radiocarbon of dissolved humic substances in river waters from the Chernobyl area

    NASA Astrophysics Data System (ADS)

    Nagao, Seiya; Aramaki, Takafumi; Fujitake, Nobuhide; Matsunaga, Takeshi; Tkachenko, Yuri

    2004-08-01

    Radiocarbon (14C) was used to study the origin and transport of aquatic humic substances in river waters at the Chernobyl area, which received a pulse input of 14C as a consequence of the nuclear accident. Water samples were collected in April 1999 from the Pripyat and Sakhan Rivers, which flow through the radioactive contaminated area (30 km exclusion zone). The Δ14C values of humic and fulvic acids ranged from -68‰ to +75‰ and were ∼400‰ lower than those of non-contaminated environments. The aquatic humic substances may be derived mainly from those of bog, peat, and podzolic soil with older 14C age, and thereby reflect a larger proportion of older groundwater humic substances. Contribution of 14C by the Chernobyl accident appears to be small because of the long residence time of organic carbon at the surface soil.

  18. Synthetic humic substances and their use for remediation of contaminated environments

    NASA Astrophysics Data System (ADS)

    Dudare, Diana; Klavins, Maris

    2014-05-01

    Soils are increasingly subjected to different chemical stresses, because of increasing industrialization process and other factors. Different anthropogenic compounds (organic or inorganic in nature) upon entering the soil, may not only influence its productivity potential, but may also affect the quality of groundwater and food chain. Consequently, soils of different environments contain a complex mixture of contaminants, such as oil products, metals, organic solvents, acids, bases and radionuclides. Thereby greater focus should be paid to risk assessment and evaluation of remedial techniques in order to restore the quality of the soil and groundwater. The treatment technologies presently used to remove contaminants are physical, chemical and biological technologies. Many functional groups in the structure of humic substances determine their ability to interact with metal ions forming stable complexes and influencing speciation of metal ions in the environment, as well mobility, behaviour and speciation forms in the environment. Humic substances are suggested for use in the remediation of environments contaminated with metals, owing to complex forming properties. Several efforts have been undertaken with respect to synthesize humic substances for their structural studies. At the same time the real number of methods suggested for synthesis of humic substances is highly limited and their synthesis in general has been used mostly for their structural analysis. The present study deals with development of approaches for synthesis of humic substances with increased complex forming ability in respect to metal ions. Industrially produced humic substances (TEHUM) were used for comparison and after their modification their properties were analyzed for their elemental composition; functional group content changes in spectral characteristics. Synthetic humic substances showed significant differences in the number of functional groups and in ability to interact with the metal

  19. Role of dissolved humic substances surrogates on phthalate esters migration from sewage sludge.

    PubMed

    Zheng, Z; He, P J; Zhang, H; Shao, L M

    2008-01-01

    The facilitated transport of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP), the priority endocrine disrupting chemicals in sludge, by dissolved humic substances (HS) was evaluated by batch extraction. The DBP, much less hydrophobic than DEHP, was inclined to migrate from sludge matrix into humic substances solutions, while the DEHP could not migrate facilitated by most humic and fulvic acids solutions, except the humic acid surrogate of high humification. This result revealed that the affinity of DEHP in sludge matrix exceeded DBP and was not susceptible by weak HS. The hydrophobic property controlled the association of phthalic acid esters on sludge residual phases. Migration rate of DBP was positively correlated to the weight-average molecular weight of HS surrogates and the aromatic extents of HA. Some functional groups in HS molecules benefited to the facilitated transport of DBP. PMID:18360003

  20. Identification and characterization of humic substances-degrading bacterial isolates from an estuarine environment.

    PubMed

    Esham; Ye; Moran

    2000-12-01

    Bacterial isolates were obtained from enrichment cultures containing humic substances extracted from estuarine water using an XAD-8 resin. Eighteen isolates were chosen for phylogenetic and physiological characterization based on numerical importance in serial dilutions of the enrichment culture and unique colony morphology. Partial sequences of the 16S rRNA genes indicated that six of the isolates were associated with the alpha subclass of Proteobacteria, three with the gamma-Proteobacteria, and nine with the Gram-positive bacteria. Ten isolates degraded at least one (and up to six) selected aromatic single-ring compounds. Six isolates showed ability to degrade [(14)C]humic substances derived from the dominant salt marsh grass in the estuary from which they were isolated (Spartina alterniflora), mineralizing 0.4-1.1% of the humic substances over 4 weeks. A mixture of all 18 isolates did not degrade humic substances significantly faster than any of the individual strains, however, and no isolate degraded humic substances to the same extent as the natural marine bacterial community (3.0%). Similar studies with a radiolabeled synthetic lignin ([beta-(14)C]dehydropolymerisate) showed measurable levels of degradation by all 18 bacteria (3.0-8.8% in 4 weeks), but mineralization levels were again lower than that observed for the natural marine bacterial community (28.2%). Metabolic capabilities of the 18 isolates were highly variable and generally did not map to phylogenetic affiliation. PMID:11102687

  1. On-the-fly fluorescence lifetime detection of humic substances in capillary electrophoresis.

    PubMed

    Hewitt, Joseph D; McGown, Linda B

    2003-03-01

    On-the-fly fluorescence lifetime detection was investigated as a tool for studying humic substances in capillary zone electrophoresis (CZE). Humic substances are complex, heterogeneous mixtures of natural products that tend to migrate in a single, broad CZE peak. The intrinsic fluorescence lifetime of five humic substances from the International Humic Substances Society (IHSS) was monitored using excitation at 488 or 364 nm to produce intensity-lifetime electropherograms for each of the substances. Each frequency-domain lifetime measurement, collected at subsecond intervals during the CZE run, contains the equivalent of a complete decay profile. Lifetime analysis of each decay profile was used to construct a lifetime-resolved electropherogram for each lifetime component, from which the variation in relative intensity contributions of each lifetime across the broad CZE peak could be determined. Absorption spectra, fluorescence excitation-emission spectra, and lifetime profiles of batch solutions of the samples were determined as well. It was found that, whereas absorption and fluorescence spectral characteristics tended to discriminate between humic acids and fulvic acids, the batch solution lifetime profiles discriminated instead between samples from different sources, regardless of fraction. On-the-fly lifetime detection provided a more detailed view of the fluorescence decay of the samples, including greater resolution of lifetimes for two of the fulvic acids and greater discrimination among samples based on lifetime profiles across the CZE peaks. PMID:14658616

  2. High Pressure Size Exclusion Chromatography (HPSEC) of humic substances: molecular sizes, analytical parameters, and column performance

    PubMed

    Conte; Piccolo

    1999-02-01

    High Pressure Size Exclusion chromatography (HPSEC) is increasingly used to evaluate molecular sizes of humic substances from different sources. Asymmetry factors (As), number of theoretical plates (N), coefficient of distribution (k(d)), and column resolution (Rs) were determined for two different HPSEC columns (TSK G3000SW and Biosep S2000) and polysaccharides of known molecular weights were used as standards. Calibration curves were equivalent for both columns whereas analytical parameters revealed that the TSK column was only slightly more efficient in separating polysaccharide standards. Mw and Mn values for humic substances differed according to the molecular weight range of each column but relative standard deviation never exceeded 5% for both columns. Variations between columns were attributed to intrinsic humic properties such as the stability of conformational structures. These results suggested that humic substances in solutions are loosely-bound association of small molecules that may be consistently dispersed by diffusion through size-exclusion pores. HPSEC is confirmed to represent a highly precise method to evaluate the relative molecular-size distribution of dissolved humic substances. PMID:10901671

  3. Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation

    SciTech Connect

    Reid, P.M.; Wilkinson, A.E.; Tipping, E.; Jones, M.N. Freshwater Biological Association, Ambleside, Cumbria )

    1990-01-01

    Samples of peat humic acid (PHA) and surface water humic (WBHA) and fulvic (WBFA) acids have been extracted from Whitray Beck in North Yorkshire, U.K. The molecular weights of the extracts have been investigated by sedimentation equilibrium using an analytical ultracentrifuge equipped with a UV scanning system. The system allows measurements to be made at low concentrations of humic substances, comparable to those existing in natural humic-rich water. A method is described for correcting UV scanning data for changes in the optical properties of the materials with changing molecular weight. Measurements have also been made on reference samples of Suwannee river humic (SRHA) and fulvic (SRFA) acids from the International Humic Substances Society (IHSS). The weight-average moleuclar weights of the extracted samples range from approximately 2,000 to 17,000 and follow a series PHA > WBHA > WBFA. Apparent specific volumes of these materials were in a range from 0.45 to 0.58 cm{sup 3} g{sup {minus}1} as measured by digital densimetry. Al the samples studied were analysed by gel filtration, but the molecular weights determined by this method based on a globular protein calibration are not in good accord with the absolute determinations by the sedimentation-equilibrium technique. The molecular weight of the SRHA determined by sedimentation equilibrium is in good agreement with that reported by BECKETT (1987) et al., based on flow field-flow fractionation.

  4. Determination of molecular weights of humic substances by analytical (UV scanning) ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Reid, Patrick M.; Wilkinson, Alan E.; Tipping, Edward; Jones, Malcolm N.

    1990-01-01

    Samples of peat humic acid (PHA) and surface water humic (WBHA) and fulvic (WBFA) acids have been extracted from Whitray Beck in North Yorkshire, U.K. The molecular weights of the extracts have been investigated by sedimentation equilibrium using an analytical ultracentrifuge equipped with a UV scanning system. The system allows measurements to be made at low concentrations of humic substances, comparable to those existing in natural humic-rich water. A method is described for correcting UV scanning data for changes in the optical properties of the materials with changing molecular weight. Measurements have also been made on reference samples of Suwannee river humic (SRHA) and fulvic (SRFA) acids from the International Humic Substances Society (IHSS). The weight-average molecular weights of the extracted samples range from approximately 2000 to 17000 and follow a series PHA > WBHA > WBFA. Apparent specific volumes of these materials were in a range from 0.45 to 0.58 cm 3 g -1 as measured by digital densimetry. All the samples studied were analysed by gel filtration, but the molecular weights determined by this method based on a globular protein calibration are not in good accord with the absolute determinations by the sedimentation-equilibrium technique. The molecular weight of the SRHA determined by sedimentation equilibrium is in good agreement with that reported by BECKETT (1987) et al., based on flow field-flow fractionation.

  5. Complexation of transuranic ions by humic substances: Application of laboratory results to the natural system

    SciTech Connect

    Czerwinski, K.; Kim, J.

    1997-12-31

    Environmental investigations show transuranic ions sorb to humic substances. The resulting species are often mobile and are expected to be important vectors in the migration of transuranic ions in natural systems. However, these environmental studies yield no quantitative data useful for modeling. Laboratory complexation experiments with transuranic ions and humic substances generate thermodynamic data required for complexation modeling. The data presented in this work are based on the metal ion charge neutralization model, which is briefly described. When a consistent complexation model is used, similar results are obtained from different experimental conditions, techniques, and laboratories. Trivalent transuranic ions (Cm(III), Am(III)) have been extensively studied with respect to pH, ionic strength, origin of humic acid, and mixed species formation. The complexation of Np(V) has been examined over a large pH and metal ion concentration range with different humic acids. Some data does exist on the complexation ion concentration range with different humic acids. Some data does exist on the complexation of plutonium with humic acid, however further work is needed. Calculations on the Gorleben aquifer system using the thermodynamic data are presented. Critical information lacking from the thermodynamic database is identified. 55 refs., 2 figs., 3 tabs.

  6. Effects of aluminum-induced aggregation on the fluorescence of humic substances

    SciTech Connect

    Sharpless, C.M.; McGown, L.B.

    1999-09-15

    Aluminum-induced aggregates of terrestrial and aquatic humic acid standards from the International Humic Substances Society are shown to be fluorescent by means of a multiwavelength fluorescence anisotropy experiment in which the data were treated with a model for nonspherical particles. While aggregates of aquatic humic acids appear in the fluorescence signal at both short and long excitation wavelengths, aggregates of terrestrial humic acids are detected only at the long Wavelength. Furthermore, the results indicate that emission obtained at longer excitation wavelengths is representative of smaller particles. At pH 4, the aquatic humic acids appear to exist in an extended conformation, whereas the terrestrial humic acids show less extension. The size and shape of the fluorescent particles display a complex dependence on Al concentration. Both enhancement and quenching of fluorescence are observed in the total luminescence spectra upon Al addition. However, quenching is shown to be the result of decreased humic acid concentration due to precipitation by Al rather than photophysical processes.

  7. Order of functionality loss during photodegradation of aquatic humic substances

    USGS Publications Warehouse

    Thorn, Kevin A.; Younger, Steven J.; Cox, Larry G.

    2009-01-01

    The time course photodegradation of the Nordic aquatic fulvic and humic acids and Suwannee River XAD-4 acids subjected to UV irradiation with an unfiltered medium pressure mercury lamp was studied by liquid-state 13C nuclear magnetic resonance. Photodecarboxylation was a significant pathway in all cases. Decreases in ketone, aromatic, and O-alkyl carbons were observed throughout the course of the irradiations, whereas C-alkyl carbons resisted photodegradation. Peaks attributable to the low-molecular-weight photodegradation products bicarbonate, formate, acetate, and succinate grew in intensity with irradiation time. The final products of the irradiations were decarboxylated, hydrophobic, predominantly C-alkyl and O-alkyl materials that were resistant to further photodegradation. The total amount of carbon susceptible to loss appeared to be related mainly to the total concentration of carbonyl and aromatic carbons and partly to the concentration of O-alkyl carbons in the fulvic, humic, and XAD-4 acids. The carbon losses for Nordic fulvic, Nordic Humic, Suwannee fulvic, and Suwannee XAD-4 acids were estimated to be 75, 63, 56, and 17%, respectively. More detailed analyses of the effects of irradiation on the carbonyl functionality in Nordic humic acid and Laurentian soil fulvic acid through reaction with hydroxylamine in conjunction with 15N nuclear magnetic resonance analysis confirmed preferential photodegradation of the quinone/hydroquinone functionality over ketone groups and the loss of ester groups in Laurentian fulvic acid.

  8. Fouling of enhanced biological phosphorus removal-membrane bioreactors by humic-like substances.

    PubMed

    Poorasgari, Eskandar; König, Katja; Fojan, Peter; Keiding, Kristian; Christensen, Morten Lykkegaard

    2014-12-01

    Fouling by free extracellular polymeric substances was studied in an enhanced biological phosphorus removal-membrane bioreactor. It was demonstrated that the free extracellular polymeric substances, primarily consisting of humic-like substances, were adsorbed to the membrane used in the enhanced biological phosphorus removal-membrane bioreactor plant. Infrared analyses indicated the presence of the humic-like substances on the membrane's active surface after filtration of the free extracellular polymeric substances suspension. Scanning electron microscopy showed the presence of a gel layer on the membrane surface after filtration of the free extracellular polymeric substances suspension. The gel layer caused a significant decline in water flux. This layer was not entirely removed by a backwashing, and the membrane's water flux could not be re-established. The membrane used in the enhanced biological phosphorus removal-membrane bioreactor plant showed infrared spectra similar to that fouled by the free extracellular polymeric substances suspension in the laboratory. Thus, the results of this study show the importance of humic-like substances in irreversible fouling of enhanced biological phosphorus removal-membrane bioreactor systems. PMID:25014564

  9. Formation and loss of humic substances during decomposition in a pine forest floor

    USGS Publications Warehouse

    Qualls, R.G.; Takiyama, A.; Wershaw, R. L.

    2003-01-01

    Since twice as much C is sequestered in soils as is contained in the atmosphere, the factors controlling the decomposition rate of soil C are important to the assessment of the effects of climatic change. The formation of chemically resistant humic substances might be an important process controlling recycling of CO2 to the atmosphere. Our objectives were to measure the rate of formation and loss of humic substances during 13 yr of litter decomposition. We placed nets on the floor of a white pine (Pinus strobus) forest to separate each annual layer of litter for 13 yr and measured humic substance concentration using NaOH extraction followed by chromatographic fractionation. The humic acid fraction increased from 2.1% of the C in litterfall to 15.7% after 1 yr. On a grams per square meter (g m-2) basis the humic substance fraction increased during the first year and then declined, with a half decay time (t1/2) of 5.1 yr, which was significantly slower than the bulk litter (t1/2 = 3.9 yr). The carboxylic C concentration estimated from 13C nuclear magnetic resonance (NMR) increased in the litter over time, though total mass of carboxylic acid C in the forest floor also declined over the 13-yr period (t1/2 = 4.6 yr). While humic substances in the forest floor decomposed at a somewhat slower rate than bulk litter during Years 1 to 13, they decomposed much faster than has been calculated from 14C dating of the refractory fraction of organic matter in the mineral soil.

  10. Investigation of metal ions binding of humic substances using fluorescence emission and synchronous-scan spectroscopy.

    PubMed

    Piana, M J; Zahir, K O

    2000-01-01

    The binding site interactions of IHSS humic substances, Suwannee River Humic Acid, Suwannee River Fulvic Acid, Nordic Fulvic Acid, and Aldrich Humic Acid with various metals ions and a herbicide, methyl viologen were investigated using fluorescence emission and synchronous-scan spectroscopy. The metal ions used were, Fe(III), Cr(III), Cr(VI), Pb(II), Cu(II) and Ni(II). Stern-Volmer constants, Ksv for these quenchers were determined at pH 4 and 8 using an ionic strength of 0.1 M. For all four humic substances, and at both pH studied, Fe(III) was found to be the most efficient quencher. Quenching efficiency was found to be 3-10 times higher at pH 8. The bimolecular quenching rate constants were found to exceed the maximum considered for diffusion controlled interactions, and indicate that the fluorophore and quencher are in close physical association. Synchronous-scan spectra were found to change with pH and provided useful information on binding site interactions between humic substances and these quenchers. PMID:10693057

  11. Modeling electrostatic and heterogeneity effects on proton dissociation from humic substances

    USGS Publications Warehouse

    Tipping, E.; Reddy, M.M.; Hurley, M.A.

    1990-01-01

    The apparent acid dissociation constant of humic substances increases by 2-4 pK units as ionization of the humic carboxylate groups proceeds. This change in apparent acid strength is due in part to the increase in electrical charge on the humic molecules as protons are shed. In addition, proton dissociation reactions are complicated because humic substances are heterogeneous with respect to proton dissociating groups and molecular size. In this paper, we use the Debye-Hu??ckel theory to describe the effects of electrostatic interactions on proton dissociation of humic substances. Simulations show that, for a size-heterogeneous system of molecules, the weight-average molecular weight is preferable to the number-average value for averaging the effects of electrostatic interactions. Analysis of published data on the proton dissociation of fulvic acid from the Suwannee River shows that the electrostatic interactions can be satisfactorily described by a hypothetical homogeneous compound having a molecular weight of 1000 (similar to the experimentally determined weight-average value). Titration data at three ionic strengths, for several fulvic acid concentrations, and in the pH range from 2.9 to 6.4 can be fitted with three adjustable parameters (pK??int values), given information on molecular size and carboxylate group content. ?? 1990 American Chemical Society.

  12. Dissolution and Mobilization of Uranium in a Reduced Sediment by Natural Humic Substances under Anaerobic Conditions

    SciTech Connect

    Gu, Baohua; Luo, Wensui

    2009-01-01

    Biological reduction and precipitation of uranium (U) has been proposed as a remedial option for immobilizing uranium at contaminated sites, but the long-term stability and mobility of uranium remain a concern because it is neither removed nor destroyed. In this study, the dissolution and mobilization of reduced and oxidized forms of uranium [U(IV) and U(VI)] by natural humic substances were investigated in batch and column flow systems using a bioreduced sediment containing both U(IV) and U(VI). The addition of humic substances significantly increased the dissolution of U(IV) under anaerobic conditions. Humic acid (HA) was found to be more effective than fulvic acid (FA) in dissolving U(IV) in either 1 mM KCl or KHCO3 background solution. However, more U(VI) was dissolved in 1 mM KHCO3 than in 1 mM KCl background electrolytes. The HA also was found to be more effective than FA in mobilizing uranium under reducing and column flow conditions, although an accumulative amount of eluted U(VI) and U(IV) was relatively low (<60 g) after leaching with ~97 pore volumes of the humic solution in 1 mM KHCO3. These observations suggest that natural humic substances could potentially influence the long-term stability of bioreduced U(IV) even under strong reducing environments.

  13. Mechanisms for the suppression of methane production in peatland soils by a humic substance analog

    NASA Astrophysics Data System (ADS)

    Ye, R.; Keller, J. K.; Jin, Q.; Bohannan, B. J. M.; Bridgham, S. D.

    2014-01-01

    Methane (CH4) production is often impeded in many northern peatland soils, although inorganic terminal electron acceptors (TEAs) are usually present in low concentrations in these soils. Recent studies suggest that humic substances in wetland soils can be utilized as organic TEAs for anaerobic respiration and may directly inhibit CH4 production. Here we utilize the humic analog anthraquinone-2, 6-disulfonate (AQDS) to explore the importance of humic substances, and their effects on the temperature sensitivity of anaerobic decomposition, in two peatland soils. In a bog peat, AQDS was not instantly utilized as a TEA, but greatly inhibited the fermentative production of acetate, carbon dioxide (CO2), and hydrogen (H2), as well as CH4 production. When added together with glucose, AQDS was partially reduced after a lag period of 5 to 10 days. In contrast, no inhibitory effect of AQDS on fermentation was found in a fen peat and AQDS was readily reduced as an organic TEA. The addition of glucose and AQDS to both bog and fen peats caused complicated temporal dynamics in the temperature sensitivity of CH4 production, reflecting temporal changes in the temperature responses of other carbon processes with effects on methanogenesis. Our results show that the humic analog AQDS can act both as an inhibitory agent and a TEA in peatland soils. The high concentrations of humic substances in northern peatlands may greatly influence the effect of climate change on soil carbon cycling in these ecosystems.

  14. Characteristics of Soil Humic Substances as Determined by Conventional and Synchrotron Fourier Transform Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, S.; Song, X. Y.; Wang, N.; Li, C. X.; Wang, W.; Zhang, J. J.

    2014-11-01

    Humic substances (HS) play an important role in soil fertility and carbon sequestration in soil. The structural characteristics of soil HS, extracted from two natural soils and a laboratory-incubated soil, were investigated by conventional beamline-based Fourier transform infrared radiation (CB-FTIR), a common FTIR technique based on a conventional thermal source, and synchrotron radiation-based (SR-FTIR) spectroscopy. The relative area of absorbance peaks that appeared at 2930, 2860, 1711, and 1635 cm-1 were calculated to make a comparison of the absorbance intensities. The absorption of aromatic functional groups of HS was stronger in SR-FTIR spectroscopy than in CB-FTIR spectroscopy. Compared with humic acid extracted with a 0.1 mol/l Na4P2O7 solution, the level of aliphaticity in humic acid extracted with a 0.1 mol/l NaOH solution was higher. The aliphaticity of humin associated with clay (HMc) was higher than that of humin associated with iron (HMi). These results suggest that SR-FTIR spectroscopy is a useful and nondestructive technique to study the structural characteristics of soil humic substances. Sequential extraction of soil humic substances with NaOH and Na4P2O7 solutions may be helpful in providing additional information in cases where differences in the material obtained from different extraction solutions occur. The aliphaticity and complexity of HMc were higher than those of HMi.

  15. Isotope-Filtered 4D NMR Spectroscopy for Structure Determination of Humic Substances**

    PubMed Central

    Bell, Nicholle G A; Michalchuk, Adam A L; Blackburn, John W T; Graham, Margaret C; Uhrín, Dušan

    2015-01-01

    Humic substances, the main component of soil organic matter, could form an integral part of green and sustainable solutions to the soil fertility problem. However, their global-scale application is hindered from both scientific and regulatory perspectives by the lack of understanding of the molecular make-up of these chromatographically inseparable mixtures containing thousands of molecules. Here we show how multidimensional NMR spectroscopy of isotopically tagged molecules enables structure characterization of humic compounds. We illustrate this approach by identifying major substitution patterns of phenolic aromatic moieties of a peat soil fulvic acid, an operational fraction of humic substances. Our methodology represents a paradigm shift in the use of NMR active tags in structure determination of small molecules in complex mixtures. Unlike previous tagging methodologies that focused on the signals of the tags, we utilize tags to directly probe the identity of the molecules they are attached to. PMID:26036217

  16. Influence of humic substances on plant-microbes interactions in the rhizosphere

    NASA Astrophysics Data System (ADS)

    Puglisi, Edoardo; Pascazio, Silvia; Spaccini, Riccardo; Crecchio, Carmine; Trevisan, Marco; Piccolo, Alessandro

    2013-04-01

    Humic substances are known to play a wide range of effects on the physiology of plant and microbes. This is of particular relevance in the rhizosphere of terrestrial environments, where the reciprocal interactions between plants roots, soil constituents and microorganisms strongly influence the plants acquisition of nutrients. Chemical advances are constantly improving our knowledge on humic substances: their supra-molecular architecture, as well as the moltitude of their chemical constituents, many of which are biologically active. An approach for linking the structure of humic substances with their biological activity in the rhizosphere is the use of rhizoboxes, which allow applying a treatment (e.g., an amendment with humic substances) in an upper soil-plant compartment and take measurements in a lower isolated rhizosphere compartment that can be sampled at desired distances from the rhizoplane. This approach can be adopted to assess the effects of several humic substances, as well as composted materials, on maize plants rhizodeposition of carbon, and in turn on the structure and activity of rhizosphere microbial communities. In order to gain a complete understanding of processes occurring in the complex soil-plant-microorganisms tripartite system, rhizobox experiments can be coupled with bacterial biosensors for the detection and quantification of bioavailable nutrients, chemical analyses of main rhizodeposits constituents, advanced chemical characterizations of humic substances, DNA-fingerprinting of microbial communities, and multivariate statistical approaches to manage the dataset produced and to infer general conclusions. By such an approach it was found that humic substances are significantly affecting the amount of carbon deposited by plant roots. This induction effect is more evident for substances with more hydrophobic and complex structure, thus supporting the scientific hypothesis of the "microbial loop model", which assumes that plants feed

  17. Reactions of hydroxyl radical with humic substances: bleaching, mineralization, and production of bioavailable carbon substrates.

    PubMed

    Goldstone, J V; Pullin, M J; Bertilsson, S; Voelker, B M

    2002-02-01

    In this study, we examine the role of the hydroxyl (OH*) radical as a mechanism for the photodecomposition of chromophoric dissolved organic matter (CDOM) in sunlit surface waters. Using gamma-radiolysis of water, OH* was generated in solutions of standard humic substances in quantities comparable to those produced on time scales of days in sunlit surface waters. The second-order rate coefficients of OH* reaction with Suwannee River fulvic (SRFA; 2.7 x 10(4) s(-1) (mg of C/L)(-1)) and humic acids (SRHA; 1.9 x 10(4) s(-1) (mg of C/L)(-1)) are comparable to those observed for DOM in natural water samples and DOM isolates from other sources but decrease slightly with increasing OH* doses. OH* reactions with humic substances produced dissolved inorganic carbon (DIC) with a high efficiency of approximately 0.3 mol of CO2/mol of OH*. This efficiency stayed approximately constant from early phases of oxidation until complete mineralization of the DOM. Production rates of low molecular weight (LMW) acids including acetic, formic, malonic, and oxalic acids by reaction of SRFA and SRHA with OH* were measured using HPLC. Ratios of production rates of these acids to rates of DIC production for SRHA and for SRFA were similar to those observed upon photolysis of natural water samples. Bioassays indicated that OH* reactions with humic substances do not result in measurable formation of bioavailable carbon substrates other than the LMW acids. Bleaching of humic chromophores by OH* was relatively slow. Our results indicate that OH* reactions with humic substances are not likely to contribute significantly to observed rates of DOM photomineralization and LMW acid production in sunlit waters. They are also not likely to be a significant mechanism of photobleaching except in waters with very high OH* photoformation rates. PMID:11871550

  18. Covalent binding of aniline to humic substances. 1. Kinetic studies

    USGS Publications Warehouse

    Weber, E.J.; Spidle, D.L.; Thorn, K.A.

    1996-01-01

    The reaction kinetics for the covalent binding of aniline with reconstituted IHSS humic and fulvic acids, unfractionated DOM isolated from Suwannee River water, and whole samples of Suwannee River water have been investigated. The reaction kinetics in each of these systems can be adequately described by a simple second-order rate expression. The effect of varying the initial concentration of aniline on reaction kinetics suggested that approximately 10% of the covalent binding sites associated with Suwannee River fulvic acid are highly reactive sites that are quickly saturated. Based on the kinetic parameters determined for the binding of aniline with the Suwannee River fulvic and humic acid isolates, it was estimated that 50% of the aniline concentration decrease in a Suwannee River water sample could be attributed to reaction with the fulvic and humic acid components of the whole water sample. Studies with Suwannee River fulvic acid demonstrated that the rate of binding decreased with decreasing pH, which parallels the decrease in the effective concentration of the neutral form, or reactive nucleophilic species of aniline. The covalent binding of aniline with Suwannee River fulvic acid was inhibited by prior treatment of the fulvic acid with hydrogen sulfide, sodium borohydride, or hydroxylamine. These observations are consistent with a reaction pathway involving nucleophilic addition of aniline to carbonyl moieties present in the fulvic acid.

  19. EFFECTS OF HUMIC SUBSTANCES ON ATTENUATION OF METALS: BIOAVAILABILITY AND MOBILITY IN SOIL

    EPA Science Inventory

    Humic substances play vastly important roles in metal behavior in a wide variety of environments. They can affect the mobility and bioavailability of metals by binding and sequestration thereby decreasing the mobility of a metal. They can also transport metals into solution or ...

  20. COMPARISON OF PHOTOCHEMICAL BEHAVIOR OF VARIOUS HUMIC SUBSTANCES IN WATER: II. PHOTOSENSITIZED OXYGENATIONS

    EPA Science Inventory

    The photochemical oxygenation of 2, 5-dimethylfuran (DMF) in water was studied under a variety of reaction conditions employing various humic substances as photosensitizers. As predicted by theory, the reactions at low DMF concentrations were first order with respect to DMF, and ...

  1. A new application of humic substances: activation of supports for invertase immobilization.

    PubMed

    Rosa, A H; Vicente, A A; Rocha, J C; Trevisan, H C

    2000-12-01

    Invertase was immobilized on aminopropyl silica (APTS-SiO2) activated with humic substances (APTS-SiO2-HS) and on aminopropyl silica activated with glutaraldehyde (APTS-SiO2-GA). The resulting activity of both systems was compared. Humic substances (HS) used for the activation of the silica were extracted from soil of Cananéia, São Paulo State, Brazil, according to the procedure recommended by the International Humic Substances Society. Activity was determined by measuring the rate of formation of reduced sugars using the reaction with dinitrosalicylic acid (DNS). The amount of HS bound on the APTS-SiO2 was equal to 50 mg. The maximum amount of invertase immobilized on APTS-SiO2-HS was 15,200 U/g while in the system APTS-SiO2-GA it was 13,400 U/g. The experimental enzymatic activity was 3,700 and 3,300 U/g, for the systems APTS-SiO2-HS and APTS-SiO2-GA, respectively. Considering the increased amount and activity of immobilized enzyme compared with the glutaraldehyde method, it was concluded that this technique opens a new perspective in the preparation of supports for enzyme immobilization employing humic substances. PMID:11227556

  2. TRICHLOROETHYLENE ADSORPTION BY ACTIVATED CARBON PRELOADED WITH HUMIC SUBSTANCES: EFFECTS OF SOLUTION CHEMISTRY. (R828157)

    EPA Science Inventory

    Abstract

    Trichloroethylene (TCE) adsorption by activated carbon previously loaded ("preloaded") with humic substances was found to decrease with increasing concentrations of monovalent ions (NaCl), calcium (until solubility was exceeded), or dissolved oxygen in...

  3. Clay surface catalysis of formation of humic substances: potential role of maillard reactions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mechanisms of the formation of humic substances are poorly understood, especially the condensation of amino acids and reducing sugars products (Maillard reaction) in soil environments. Clay minerals behave as Lewis and Brönsted acids and catalyze several reactions and likely to catalyze the Mai...

  4. Humic substances and nitrogen-containing compounds from low rank brown coals

    SciTech Connect

    Demirbas, A.; Kar, Y.; Deveci, H.

    2006-03-15

    Coal is one of the sources of nitrogen-containing compounds (NCCs). Recovery of NCCs from brown coals in high yield was carried out from tars of stepwise semicoking of brown coals. Humic acids have been shown to contain many types of nitrogen compounds. Humic acids are thought to be complex aromatic macromolecules with amino acids, amino sugars, peptides, and aliphatic compounds that are involved in the linkages between the aromatic groups. Humic acids extracted from peats, brown coals, and lignites, are characterized using different techniques. Humic substances (HSs) have several known benefits to agriculture. The properties of humic substances vary from source to source, because they are heterogeneous mixtures of biochemical degradation products from plant and animal residues, and synthesis activities of microorganisms. HSs have been considered to be a significant floculant in surface water filtration plants for the production of drinking water as well as the processing of water. HSs are produced from chemical and biological degradation of plant and animal residues and from synthetic activities of microorganisms.

  5. Presence and potential significance of aromatic-ketone groups in aquatic humic substances

    USGS Publications Warehouse

    Leenheer, J.A.; Wilson, M.A.; Malcolm, R.L.

    1987-01-01

    Aquatic humic- and fulvic-acid standards of the International Humic Substances Society were characterized, with emphasis on carbonyl-group nature and content, by carbon-13 nuclear-magnetic-resonance spectroscopy, proton nuclear-magnetic-resonance spectroscopy, and infrared spectroscopy. After comparing spectral results of underivatized humic and fulvic acids with spectral results of chemically modified derivatives, that allow improved observation of the carbonyl group, the data clearly indicated that aromatic ketone groups comprised the majority of the carbonyl-group content. About one ketone group per monocyclic aromatic ring was determined for both humic and fulvic acids. Aromatic-ketone groups were hypothesized to form by photolytic rearrangements and oxidation of phenolic ester and hydrocarbon precursors; these groups have potential significance regarding haloform formation in water, reactivity resulting from active hydrogen of the methyl and methylene adjacent to the ketone groups, and formation of hemiketal and lactol structures. Aromatic-ketone groups also may be the point of attachment between aliphatic and aromatic moieties of aquatic humic-substance structure. ?? 1987.

  6. Effect of compost amendment on soil organic matter and humic substances

    NASA Astrophysics Data System (ADS)

    Roca-Pérez, L.; Gil, C.; Jurado, M.; Pons, V.; Boluda, R.

    2009-04-01

    Organic soil amendments are increasingly being examined for their potential use to improve soil functions and quality. We studied the effect of compost amendment on soil organic matter (SOM) and humic substances. The study was carried out on Luvic Calcisol in the Valencian Community (East Spain) used as a citrus fruit orchard. Four plots were amended at dose 0, 6, 12 and 36 Mg ha-1 of rice residue and sewage sludge compost. Seven soil samples for each treatment at depths of 0-10 and 10-20 cm were taken in the first seven months after application. Soil characteristics, SOM, mineral nitrogen, total nitrogen, NH4+-N, and fulvic and humic acids were determined. The results demonstrated that the use of organic compost considerably increases SOM, total nitrogen and the humic substances such as the applied dose. The level of humic substances remained without significant variations during the experimental period. The dose of 36 Mg ha-1 proved the most efficient. We would like to thank Spanish government-MICINN for partial funding and support (MIMAN project 4.3-141/2005/3-B and MICINN project CGL2006-09776).

  7. Nitrite fixation by humic substances: Nitrogen-15 nuclear magnetic resonance evidence for potential intermediates in chemodenitrification

    USGS Publications Warehouse

    Thorn, K.A.; Mikita, M.A.

    2000-01-01

    Studies have suggested that NO2/-, produced during nitrification and denitrification, can become incorporated into soil organic matter and, in one of the processes associated with chemodenitrification, react with organic matter to form trace N gases, including N2O. To gain an understanding of the nitrosation chemistry on a molecular level, soil and aquatic humic substances were reacted with 15N-labeled NaNO2, and analyzed by liquid phase 15N and 13C nuclear magnetic resonance (NMR). The International Humic Substances Society (IHSS) Pahokee peat and peat humic acid were also reacted with Na15NO2 and analyzed by solid-state 15N NMR. In Suwannee River, Armadale, and Laurentian fulvic acids, phenolic rings and activated methylene groups underwent nitrosation to form nitrosophenols (quinone monoximes) and ketoximes, respectively. The oximes underwent Beckmann rearrangements to 2??amides, and Beckmann fragmentations to nitriles. The nitriles in turn underwent hydrolysis to 1??amides. Peaks tentatively identified as imine, indophenol, or azoxybenzene nitrogens were clearly present in spectra of samples nitrosated at pH 6 but diminished at pH 3. The 15N NMR spectrum of the peat humic acid exhibited peaks corresponding with N-nitroso groups in addition to nitrosophenols, ketoximes, and secondary Beckmann reaction products. Formation of N-nitroso groups was more significant in the whole peat compared with the peat humic acid. Carbon-13 NMR analyses also indicated the occurrence of nitrosative demethoxylation in peat and soil humic acids. Reaction of 15N-NH3 fixated fulvic acid with unlabeled NO2/- resulted in nitrosative deamination of aminohydroquinone N, suggesting a previously unrecognized pathway for production of N2 gas in soils fertilized with NH3.Studies have suggested that NO2-, produced during nitrification and denitrification, can become incorporated into soil organic matter and, in one of the processes associated with chemodenitrification, react with organic

  8. Sorption of metal ions on lignite and the derived humic substances.

    PubMed

    Havelcová, Martina; Mizera, Jirí; Sýkorová, Ivana; Pekar, Miloslav

    2009-01-15

    The study presents results of sorption of metal ions (Pb2+, Zn2+, Cu2+, and Cd2+) onto lignite mined in South Moravia, Czech Republic, and solid humic substances (humin and humic acid) derived from it. The efficiency of these sorbents has been studied as a function of contact time, solution pH, and metal concentration. The sorption efficiencies were higher for humin and lower for humic acid samples than for the original lignite. With its high sorption capacities of several mmol/g, particularly for Pb2+ and Cd2+, the South Moravian lignite can provide a cheap source material for preparation of sorbents utilizable in removal of toxic metals from wastewaters. PMID:18490104

  9. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants

    NASA Astrophysics Data System (ADS)

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-02-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established.

  10. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants

    PubMed Central

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-01-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established. PMID:26862010

  11. Structure-Property-Function Relationship in Humic Substances to Explain the Biological Activity in Plants.

    PubMed

    García, Andrés Calderín; de Souza, Luiz Gilberto Ambrosio; Pereira, Marcos Gervasio; Castro, Rosane Nora; García-Mina, José María; Zonta, Everaldo; Lisboa, Francy Junior Gonçalves; Berbara, Ricardo Luis Louro

    2016-01-01

    Knowledge of the structure-property-function relationship of humic substances (HSs) is key for understanding their role in soil. Despite progress, studies on this topic are still under discussion. We analyzed 37 humic fractions with respect to their isotopic composition, structural characteristics, and properties responsible for stimulating plant root parameters. We showed that regardless of the source of origin of the carbon (C3 or C4), soil-extracted HSs and humic acids (HAs) are structurally similar to each other. The more labile and functionalized HS fraction is responsible for root emission, whereas the more recalcitrant and less functionalized HA fraction is related to root growth. Labile structures promote root stimulation at lower concentrations, while recalcitrant structures require higher concentrations to promote a similar stimulus. These findings show that lability and recalcitrance, which are derived properties of humic fractions, are related to the type and intensity of their bioactivity. In summary, the comparison of humic fractions allowed a better understanding of the relationship between the source of origin of plant carbon and the structure, properties, and type and intensity of the bioactivity of HSs in plants. In this study, scientific concepts are unified and the basis for the agronomic use of HSs is established. PMID:26862010

  12. BDE-209: kinetic studies and effect of humic substances on photodegradation in water.

    PubMed

    Leal, J F; Esteves, V I; Santos, E B H

    2013-12-17

    BDE-209 is a brominated flame retardant and a priority contaminant, which has been found in several environmental matrices, namely, in water. To date, there are no quantum yield data for BDE-209 photodegradation by sunlight in water, to allow predicting half-life times in aquatic systems. In this work, the kinetics of BDE-209 photodegradation in water was studied and the influence of different fractions of aquatic humic substances (HS) was evaluated. Aqueous solutions of BDE-209 exposed for different periods of time to simulated sunlight were analyzed by HPLC-UV after being concentrated using dispersive liquid-liquid microextraction (DLLME) or solid-phase extraction (SPE). The photodegradation of BDE-209 in aqueous solution followed pseudo-first-order kinetics. The average quantum yield obtained of 0.010 ± 0.001 (about 20-fold lower than the quantum yield determined in ethanol) allow to predict an outdoor half-life time of 3.5 h. The photodegradation percentage of BDE-209 was not significantly affected by the XAD-4 fraction of HS, but it decreased substantially in the presence of humic and fulvic acids. Light screening by the humic substances could not explain this delay, which is probably the result of the association of the compound with the hydrophobic sites of the humic material. PMID:24245794

  13. Distinguishing black carbon from biogenic humic substances in soil clay fractions

    USGS Publications Warehouse

    Laird, D.A.; Chappell, M.A.; Martens, D.A.; Wershaw, R. L.; Thompson, M.

    2008-01-01

    Most models of soil humic substances include a substantial component of aromatic C either as the backbone of humic heteropolymers or as a significant component of supramolecular aggregates of degraded biopolymers. We physically separated coarse (0.2-2.0????m e.s.d.), medium (0.02-0.2????m e.s.d.), and fine (> 0.02????m e.s.d.) clay subfractions from three Midwestern soils and characterized the organic material associated with these subfractions using 13C-CPMAS-NMR, DTG, SEM-EDX, incubations, and radiocarbon age. Most of the C in the coarse clay subfraction was present as discrete particles (0.2-5????m as seen in SEM images) of black carbon (BC) and consisted of approximately 60% aromatic C, with the remainder being a mixture of aliphatic, anomeric and carboxylic C. We hypothesize that BC particles were originally charcoal formed during prairie fires. As the BC particles aged in soil their surfaces were oxidized to form carboxylic groups and anomeric and aliphatic C accumulated in the BC particles either by adsorption of dissolved biogenic compounds from the soil solution or by direct deposition of biogenic materials from microbes living within the BC particles. The biogenic soil organic matter was physically separated with the medium and fine clay subfractions and was dominated by aliphatic, anomeric, and carboxylic C. The results indicate that the biogenic humic materials in our soils have little aromatic C, which is inconsistent with the traditional heteropolymer model of humic substances.

  14. How humic substances dominate mercury geochemistry in contaminated floodplain soils and sediments

    SciTech Connect

    Wallschlaeger, D.; Desai, M.V.M.; Spengler, M.; Windmoeller, C.C.; Wilken, R.D.

    1998-09-01

    The interaction of mercury (Hg) and humic substances (hs) was studied in floodplain topsoils and surface sediments of the contaminated German river Elbe. An intimate coupling exists between the geochemical cycles of Hg and organic carbon (OC) in this ecosystem. Humic substances exert a dominant influence on several important parallel geochemical pathways of Hg, including binding, transformation, and transport processes. Significant differences exist between the Hg-hs associations in floodplains and sediments. Both humic acids (ha) and fulvic acids (fa) contribute to Hg binding in the sediments. In contrast, ultrafiltration experiments proved that Hg in the floodplain soils is almost exclusively bound to very large humic acids (ha) with a nominal molecular weight (MW) > 300,000. Successive cation and anion exchange experiments demonstrated that those Hg-ha complexes are inert toward competition by other cations, and also apparently predominantly electroneutral. Speciation transformation reactions in the solid phase were investigated by sequential extraction and thermal release experiments. Upon addition of Hg model compounds to a sediment matrix, all species were transformed to the same new speciation pattern, regardless of their original speciation. The accompanying alterations in availability and solubility were partially due to interconversion between the different Hg redox states, including Hg(I). Simultaneously, partial transformation of added Hg{sup 2+} into volatile Hg compounds (35% in 10 d) was observed. Finally, Hg association with water-soluble ha continuously increased downstream, indicating that hs play a key role in both lateral and longitudinal Hg transport in the Elbe ecosystem.

  15. The molecular properties of humic substances isolated from a UK upland peat system: a temporal investigation.

    PubMed

    Scott, M J; Jones, M N; Woof, C; Simon, B; Tipping, E

    2001-12-01

    The study concerns the possible changes in the molecular characteristics of humic materials isolated from the same source as a function of time. A great deal of data has been reported concerning the contrast in molecular characteristics of humic substances isolated from different environments. This has primarily been an attempt to identify source-specific molecular characteristics. However, data presented in this paper suggests that humic substances isolated from a single catchment have significant changes in molecular characteristics over time. Two naturally occurring peat pools (X and Y) situated upon a small organic catchment on Great Dun Fell, Cumbria, UK were sampled monthly between November 1994 and November 1996. Dissolved organic matter (DOM) from the pool water samples was fractionated using macroporous nonionic resins (XAD8 and 4), and the humic, fulvic and hydrophilic acids were collected. These fractions were analysed for elemental composition (C, H and N), weight average molecular weight, functional group content and adsorption (340 nm) of a 1 g l(-1) solution measured in a 1-cm spectrophotometer cell. The molecular characteristics were compared to those of natural DOM described by Scott et al. (1998). Scott et al. reported that drought conditions and seasonal climatic changes could have appreciable effects upon molecular characteristics of natural DOM. Results showed that the atomic H/C ratio of the humic substances increased immediately after strong drought conditions experienced in the summer of 1995. This change was temporary with atomic H/C ratio decreasing gradually over the following months. A similar decrease was observed in the carboxyl group content of the isolated compounds. The data set suggested that atomic H/C ratio in the fulvic and hydrophilic fractions exhibited seasonal characteristics of higher ratios during the late summer/early autumn months. This was not observed in the humic fraction. Humic acids exhibited a seasonal pattern of

  16. Comparative evaluation of humic substances in oral drug delivery.

    PubMed

    Mirza, Mohd Aamir; Ahmad, Niyaz; Agarwal, Suraj Prakash; Mahmood, Danish; Khalid Anwer, M; Iqbal, Z

    2011-05-01

    Major and biologically most explored components of natural organic matter (NOM) are humic acid (HA) and fulvic acid (FA). We have explored rock shilajit as a source of NOM. On the other hand carbamazepine (CBZ) is a well known anticonvulsant drug and has a limited accessibility to brain. Bioavailability and pharmacokinetic profiles of CBZ have been improved by complexation and different techniques also. Present study has assessed the comparative abilities of FA and HA as complexing agent for CBZ in order to enhance pharmacokinetic profile of CBZ and accessibility to the brain. These two complexing agents have been compared on various indices such as their abilities to cause complexation and enhance solubility, permeability and dissolution. The present study also compared pharmacodynamic and biochemical profiles after oral administration of complexes. With the help of various pharmaceutical techniques such as freeze drying, physical mixture, kneading and solvent evaporation, two molar ratios (1:1 and 1:2) were selected for complexation and evaluated for conformational analysis (molecular modeling). Complex formed was further characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), mass spectroscopy and X-ray diffraction (XRD). Preclinical study on rodents with CBZ-HA and CBZ-FA has yielded appreciable results in terms of their anticonvulsant and antioxidants activities. However, CBZ-HA (1:2) demonstrated better result than any other complex. PMID:25755978

  17. Comparative evaluation of humic substances in oral drug delivery

    PubMed Central

    Mirza, Mohd. Aamir; Ahmad, Niyaz; Agarwal, Suraj Prakash; Mahmood, Danish; Khalid Anwer, M.; Iqbal, Z.

    2011-01-01

    Major and biologically most explored components of natural organic matter (NOM) are humic acid (HA) and fulvic acid (FA). We have explored rock shilajit as a source of NOM. On the other hand carbamazepine (CBZ) is a well known anticonvulsant drug and has a limited accessibility to brain. Bioavailability and pharmacokinetic profiles of CBZ have been improved by complexation and different techniques also. Present study has assessed the comparative abilities of FA and HA as complexing agent for CBZ in order to enhance pharmacokinetic profile of CBZ and accessibility to the brain. These two complexing agents have been compared on various indices such as their abilities to cause complexation and enhance solubility, permeability and dissolution. The present study also compared pharmacodynamic and biochemical profiles after oral administration of complexes. With the help of various pharmaceutical techniques such as freeze drying, physical mixture, kneading and solvent evaporation, two molar ratios (1:1 and 1:2) were selected for complexation and evaluated for conformational analysis (molecular modeling). Complex formed was further characterized by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), mass spectroscopy and X-ray diffraction (XRD). Preclinical study on rodents with CBZ–HA and CBZ–FA has yielded appreciable results in terms of their anticonvulsant and antioxidants activities. However, CBZ–HA (1:2) demonstrated better result than any other complex. PMID:25755978

  18. Effects of molecular weight on the diffusion coefficient of aquatic dissolved organic matter and humic substances.

    PubMed

    Balch, J; Guéguen, C

    2015-01-01

    In situ measurements of labile metal species using diffusive gradients in thin films (DGT) passive samplers are based on the diffusion rates of individual species. Although most studies have dealt with chemically isolated humic substances, the diffusion of dissolved organic matter (DOM) across the hydrogel is not well understood. In this study, the diffusion coefficient (D) and molecular weight (MW) of 11 aquatic DOM and 4 humic substances (HS) were determined. Natural, unaltered aquatic DOM was capable of diffusing across the diffusive gel membrane with D values ranging from 2.48×10(-6) to 5.31×10(-6) cm(2) s(-1). Humic substances had diffusion coefficient values ranging from 3.48×10(-6) to 6.05×10(-6) cm(2) s(-1), congruent with previous studies. Molecular weight of aquatic DOM and HS samples (∼500-1750 Da) measured using asymmetrical flow field-flow fractionation (AF4) strongly influenced D, with larger molecular weight DOM having lower D values. No noticeable changes in DOM size properties were observed during the diffusion process, suggesting that DOM remains intact following diffusion across the diffusive gel. The influence of molecular weight on DOM mobility will assist in further understanding and development of the DGT technique and the uptake and mobility of contaminants associated with DOM in aquatic environments. PMID:25112575

  19. Chemistry and potential mutagenicity of humic substances in waters from different watersheds in Britain and Ireland

    USGS Publications Warehouse

    Watt, B.E.; Malcolm, R.L.; Hayes, M.H.B.; Clark, N.W.E.; Chipman, J.K.

    1996-01-01

    Humic substances are amorphous organic macromolecules responsible for the hue of natural waters. They are also known to be precursors of mutagens formed on chlorination prior to distribution of drinking water. In this study humic substances from the waters of primary streams, from major rivers, and from reservoirs were isolated and fractionated into humic acids (HA), fulvic acids (FA) and XAD-4 acids using columns of XAD-8 and of XAD-4 resins in tandem, and the fractions from the different sources were chlorinated and assayed for mutagenicity. CPMAS 13C NMR spectroscopy showed marked differences in compositions not only between HA, FA, and XAD-4 acids from the same water samples, but also between the same fractions from water samples from different watersheds. There were found to be strong similarities between the fractions from watersheds which had closely related soil types. Aromaticity was greatest in HAs, and lowest in XAD-4 acids, and carboxyl contents and aliphatic character were greatest in the XAD-4 acids. Carbon content decreased in the order HA > FA > XAD-4 acids, and amino acids and neutral sugars contents decreased in the order HA > XAD-4 > FA. Titration data complemented aspects of the NMR data, demonstrating that carboxyl content decreased in the order XAD-4 acids > FA > HA, and indicated that phenolic character was highest in HAs and lowest in the XAD-4 acids. All samples tested gave rise to bacterial mutagens on chlorination. Although the mutagenicities were of the same order of magnitude for the chlorinated humic samples from the different sources, the samples which showed the greatest number of revertant bacterial colonies were from the Thames and Trent, large rivers with humic materials from diverse environments, and relatively high in amino acid contents.

  20. Binding of mercury(II) to aquatic humic substances: Influence of pH and source of humic substances

    USGS Publications Warehouse

    Haitzer, M.; Aiken, G.R.; Ryan, J.N.

    2003-01-01

    Conditional distribution coefficients (KDOM???) for Hg(II) binding to seven dissolved organic matter (DOM) isolates were measured at environmentally relevant ratios of Hg(II) to DOM. The results show that KDOM??? values for different types of samples (humic acids, fulvic acids, hydrophobic acids) isolated from diverse aquatic environments were all within 1 order of magnitude (1022.5??1.0-1023.5??1.0 L kg-1), suggesting similar Hg(II) binding environments, presumably involving thiol groups, for the different isolates. KDOM??? values decreased at low pHs (4) compared to values at pH 7, indicating proton competition for the strong Hg(II) binding sites. Chemical modeling of Hg(II)-DOM binding at different pH values was consistent with bidentate binding of Hg(II) by one thiol group (pKa = 10.3) and one other group (pKa = 6.3) in the DOM, which is in agreement with recent results on the structure of Hg(II)-DOM bonds obtained by extended X-ray absorption fine structure spectroscopy (EXAFS).

  1. A comparison of dissolved humic substances from seawater with Amazon River counterparts by sup 13 C-NMR spectrometry

    SciTech Connect

    Hedges, J.I. ); Hatcher, P.G. ); Ertel, J.R. ); Meyers-Schulte, K.J. )

    1992-04-01

    Although dissolved organic matter (DOM) in seawater constitutes one of the major reservoirs of reduced carbon on earth, the biochemical and geographic origins of this material and its hydrophobic humic component remain unclear. Rivers have been suggested as a potentially important source of marine DOM, but this implication has not yet been systematically tested by direct comparisons of the bulk structural characteristics of DOM isolated from representative ocean reservoirs and their major river sources. The authors report here such a comparison and find that dissolved humic substances isolated from surface and deep seawater in the East Equatorial and north Central Pacific are enriched in nitrogen and {sup 13}C and depleted in unsaturated carbon with respect to counterparts from the Amazon River system. Based on these observations, riverine dissolved humic substances appear to comprise a small fraction of seawater humic substances and therefore must be efficiently and rapidly removed from the ocean.

  2. Metal distribution and spectroscopic analysis after soil washing with chelating agents and humic substances.

    PubMed

    Tsang, Daniel C W; Hartley, Neil R

    2014-03-01

    Biodegradable chelating agents ([S,S]-ethylenediamine-N,N-disuccinic acid (EDDS) and glutamic-N,N-diacetic acid (GLDA)) and natural humic substances (lignite-derived, standard, and commercially available humic acids) are potentially useful for enhancing soil remediation of timber treatment sites. This study integrated macroscopic and spectroscopic analyses to assess their influence on the distribution and chemical speciation of the remaining metals as well as their interaction with the soil surface after 48-h washing of a field-contaminated soil. The results demonstrated that EDDS and GLDA were an appealing alternative to non-biodegradable ethylenediamine-tetraacetic acid, but the three humic substances were less effective. As shown by sequential extractions, Cu was primarily extracted from the carbonate fraction while Cr and As extraction resulted from (co-)dissolution of the oxide fraction. As a result, the relative proportion of strongly bound organic matter and residual fractions increased by 7-16 %. However, it was noteworthy that the exchangeable fraction also increased by 5-11 %, signifying that a portion of the remaining metals was destabilized by chelating agents and transformed to be more labile in the treated soil. The X-ray photoelectron spectroscopy spectra confirmed the substantial removal of readily accessible Cu from the soil surface, but Cr maintained its original chemical forms of trivalent chromium oxides and iron-chromium coprecipitates, whereas As remained as arsenic trioxide/pentoxide and copper arsenate precipitates. On the other hand, the absence of characteristic peaks of adsorbed carboxylate groups in the Fourier-transform infrared (FTIR) spectra inferred that the extent of adsorption of chelating agents and humic substances on the bulk soil was insufficient to be characterized by FTIR analysis. These results suggested that attention should be paid to the exchangeable fraction of Cu and oxides/coprecipitates of As prior to possible on

  3. Spectral and temporal luminescent properties of Eu(III) in humic substance solutions from different origins

    NASA Astrophysics Data System (ADS)

    Brevet, Julien; Claret, Francis; Reiller, Pascal E.

    2009-10-01

    Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on their origins. The information on the difference in the structure of these complexes is scarce. To participate in the filling of this lack, a study of the spectral and temporal evolution of the Eu(III) luminescence implied in humic substance (HS) complexes is presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) and humic acid (SRHA), and Leonardite HA (LHA) from the International Humic Substances Society (USA), humic acid from Gorleben (GohyHA), and from the Kleiner Kranichsee bog (KFA, KHA) from Germany, and purified commercial Aldrich HA (PAHA), were made to contact with Eu(III). Eu(III)-HS time-resolved luminescence properties were compared with aqueous Eu 3+ at pH 5. Using an excitation wavelength of 394 nm, the typical bi-exponential luminescence decay for Eu(III)-HS complexes is common to all the samples. The components τ1 and τ2 are in the same order of magnitude for all the samples, i.e., 40 ≤ τ1 (μs) ≤ 60, and 145 ≤ τ2 (μs) ≤ 190, but significantly different. It is shown that different spectra are obtained from the different groups of samples. Terrestrial extract on the one hand, i.e. LHA/GohyHA, plus PAHA, and purely aquatic extracts on the other hand, i.e., SRFA/SRHA/KFA/KHA, induce inner coherent luminescent properties of Eu(III) within each group. The 5D 0 → 7F 2 transition exhibits the most striking differences. A slight blue shift is observed compared to aqueous Eu 3+ ( λmax = 615.4 nm), and the humic samples share almost the same λmax ≈ 614.5 nm. The main differences between the samples reside in a shoulder around λ ≈ 612.5 nm, modelled by a mixed Gaussian-Lorentzian band around λ ≈ 612 nm. SRFA shows the most intense shoulder with an intensity ratio of I612.5/ I614.7 = 1.1, KFA/KHA/SRHA share almost the same ratio I612.5/ I614.7 = 1.2-1.3, whilst the LHA

  4. Spectral and temporal luminescent properties of Eu(III) in humic substance solutions from different origins.

    PubMed

    Brevet, Julien; Claret, Francis; Reiller, Pascal E

    2009-10-01

    Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on their origins. The information on the difference in the structure of these complexes is scarce. To participate in the filling of this lack, a study of the spectral and temporal evolution of the Eu(III) luminescence implied in humic substance (HS) complexes is presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) and humic acid (SRHA), and Leonardite HA (LHA) from the International Humic Substances Society (USA), humic acid from Gorleben (GohyHA), and from the Kleiner Kranichsee bog (KFA, KHA) from Germany, and purified commercial Aldrich HA (PAHA), were made to contact with Eu(III). Eu(III)-HS time-resolved luminescence properties were compared with aqueous Eu(3+) at pH 5. Using an excitation wavelength of 394 nm, the typical bi-exponential luminescence decay for Eu(III)-HS complexes is common to all the samples. The components tau(1) and tau(2) are in the same order of magnitude for all the samples, i.e., 40 (7)F(2) transition exhibits the most striking differences. A slight blue shift is observed compared to aqueous Eu(3+) (lambda(max) = 615.4 nm), and the humic samples share almost the same lambda(max) approximately 614.5 nm. The main differences between the samples reside in a shoulder around lambda approximately 612.5 nm, modelled by a mixed Gaussian-Lorentzian band around lambda approximately 612 nm. SRFA shows the most intense shoulder with an intensity ratio of I(612.5)/I(614.7) = 1.1, KFA

  5. Covalent binding of aniline to humic substances. 2. 15N NMR studies of nucleophilic addition reactions

    USGS Publications Warehouse

    Thorn, K.A.; Pettigrew, P.J.; Goldenberg, W.S.; Weber, E.J.

    1996-01-01

    Aromatic amines are known to undergo covalent binding with humic substances in the environment. Although previous studies have examined reaction conditions and proposed mechanisms, there has been no direct spectroscopic evidence for the covalent binding of the amines to the functional groups in humic substances. In order to further elucidate the reaction mechanisms, the Suwannee River and IHSS soil fulvic and humic acids were reacted with 15N-labeled aniline at pH 6 and analyzed using 15N NMR spectrometry. Aniline underwent nucleophilic addition reactions with the quinone and other carbonyl groups in the samples and became incorporated in the form of anilinohydroquinone, anilinoquinone, anilide, imine, and heterocyclic nitrogen, the latter comprising 50% or more of the bound amine. The anilide and anilinohydroquinone nitrogens were determined to be susceptible to chemical exchange by ammonia. In the case of Suwannee River fulvic acid, reaction under anoxic conditions and pretreatment with sodium borohydride or hydroxylamine prior to reaction under oxic conditions resulted in a decrease in the proportion of anilinohydroquinone nitrogen incorporated. The relative decrease in the incorporation of anilinohydroquinone nitrogen with respect to anilinoquinone nitrogen under anoxic conditions suggested that inter- or intramolecular redox reactions accompanied the nucleophilic addition reactions.

  6. In Situ Formation of Humic-like Substances In Model Cloud Water

    NASA Astrophysics Data System (ADS)

    Gelencsér, A.; Hoffer, A.; Kiss, G.; Tombácz, E.; Blazsó, M.; Bencze, L.

    It is now widely established that humic-like substances (HULIS) are ubiquitous con- stituents in continental fine aerosol. Several studies have confirmed that HULIS are abundant organic species in the aqueous extract of rural, urban and biomass burn- ing aerosol. We have recently suggested that such compounds may be secondary (ternary?) aerosol constituents which are formed in the condensed phase from a vast array of low volatility organic precursors of primary or secondary origin. However, no experimental evidence has ever confirmed that such polymerisation reactions can indeed take place within the limited residence time of the accumulation mode aerosol. Normally, humification processes are generally assumed to take years and require spe- cial microbial environment which is barely available aloft. We studied polymerisation reactions of aromatic hydroxy-acids in the laboratory in solutions modelling the condi- tions prevalent in cloud water. In the solutions OH radicals were generated in Fenton- type reactions. The course of the reaction was monitored by UV-VIS spectrophotom- etry and liquid chromatography. The reaction products were characterised by fluo- rescence spectrometry, liquid chromatography-mass spectrometry and pyrolysis- gas chromatography-mass spectrometry. By monitoring the absorbance of the simulated cloud solution we demonstrated that chemical reactions took place in the solution pro- ducing measurable concentrations of chromophoric substances within the order of a few hours. The recorded UV-VIS spectra of the reaction products were very similar to those which had been observed in aqueous extracts of rural fine aerosol as well as in aqueous solutions of terrestrial humic and fulvic acids. Electrospray-mass spectra of the reaction products revealed that they consisted of an array of molecular species with a continuous molecular weight distribution peaking at a few hundred Dalton. Such spectra were also found to be typical of terrestrial humic and

  7. Influence of biochar addition on the humic substances of composting manures.

    PubMed

    Jindo, Keiji; Sonoki, Tomonori; Matsumoto, Kazuhiro; Canellas, Luciano; Roig, Asunción; Sanchez-Monedero, Miguel A

    2016-03-01

    Application of biochar (10% v/v) to a manure composting matrix was investigated to evaluate its effect on the chemical composition of humic substances during the composting process. The characteristics of the humic acid (HA) and fulvic acid (FA) fractions were analyzed in compost mixtures originating from two different manures (poultry manure (PM) and cow manure (CM)). The C contents of HA and FA from the manure compost/biochar blends (PM+B and CM+B) were higher than those from PM and CM, with an enhanced recalcitrant fraction, as determined by thermogravimetric analysis. Spectroscopic analysis showed that enrichment of aromatic-C and carboxylic-C occurred in the FA fractions of PM+B and CM+B to a greater extent than in PM and CM. Biochar addition into the composting mixture improved the final compost quality, especially for the light humified fraction (FA). PMID:26786401

  8. Membrane filtration studies of aquatic humic substances and their metal species: a concise overview Part 1. Analytical fractionation by means of sequential-stage ultrafiltration.

    PubMed

    Burba, P; Aster, B; Nifant'eva, T; Shkinev, V; Spivakov, B Y

    1998-03-01

    A concise overview (75 references) of the analytical fractionation of aquatic humic substances using sequential-stage ultrafiltration is presented. First, humic substances in aquatic environments and actual problems connected with their fractionation and analysis are briefly considered. The molecular size classification of dissolved humic substances by means of multistage ultrafiltration, with special emphasis on on-line techniques, is the focal point of the discussion. In particular, the capabilities of ultrafiltration for the size fractionation and characterization of species formed between colloidal humic substances and pollutants (e.g. metals) are stressed. PMID:18967087

  9. Investigating Nitrate-Dependent Humic Substance Oxidation and In-Service K-12 Teachers' Understanding of Microbiology

    ERIC Educational Resources Information Center

    Jones, Nastassia N.

    2011-01-01

    Humic substances (HS) are the humified portions of totally decomposed soil organic matter that are ubiquitous in nature. Although these substances have been studied for more than 200 years, neither their metabolic capabilities nor a specific chemical structure has yet to be determined. HS have been studied as a carbon source in many environments…

  10. The influence of structural features of marine humic substances on the accumulation rates of cadmium by a blue mussel Mytilus edulis

    SciTech Connect

    Pempkowiak, J.; Kozuch, J. ); Southon, T. )

    1994-01-01

    Laboratory experiments revealed that both concentration and origin of humic substances (HS) influence the accumulation rates of cadmium by the blue mussel Mytilus edulis. In the concentration of humic substances typical of seawater, the increase is about 60% and 100%, respectively, for aquatic and sedimentary humic substances. The phenomenon was attributed to the stimulation of cadmium uptake due to complexing properties of the substances toward cadmium. Complexing capacity of sedimentary humic substances was found to be 0.57 [mu]g/mg HS, that of aquatic substances 0.41 [mu]g/mg HS. Cross Polarization Magic Angle Spinning (CP/MAS) [sup 13]C NMR of the investigated humic substances revealed differences in the spectra at about 175, 100, 55 and 32 ppm. This was attributed to the varying content of oxygen containing functional groups involved in formation of complexes with metal ions. 8 refs., 4 figs., 3 tabs.

  11. Comparison of structural features of dissolved organic matter isolated from rainwater with those of aquatic humic substances

    NASA Astrophysics Data System (ADS)

    Santos, P.; Santos, E.; Duarte, A.

    2012-04-01

    The complexity of rainwater dissolved organic matter (DOM), a large percentage of which remains uncharacterized, has made difficult to determine the role of rainwater DOM in regional and global carbon budgets. Recent studies have focused on determining the structural characteristics of the bulk DOM in rainwater, reporting the prevalence of DOM with characteristics resembling those of natural humic substances due to its polyacidic nature. However, it is important to investigate the structural features of humic-like DOM isolated from rainwater and to evaluate whether such features differ from those found in aquatic humic substances, namely in what concerns the relative content of aliphacity and aromaticity. In this work, rainwater samples were collected for about one year, in Aveiro (Portugal). Humic-like DOM was extracted from rainwater by a procedure based on adsorption onto DAX-8 resin. The International Humic Substance Society (IHSS) (http://www.ihss.gatech.edu) operationally defined dissolved humic substances (HSs) on the base of adsorption onto a XAD-8 like resin. The isolation and extraction procedure adopted in the present work for the extraction of DOM from rainwater was slightly modified from the procedure recommended by the IHSS as suggested by Santos et al. (2009). Then, humic-like DOM isolated from rainwater was analysed by 1H NMR spectroscopy. Due to the small amounts of DOM extracted from rainwater, the DOM fractions extracted from rainwater samples were combined for each sampling season, and the 1H NMR results were compared between seasons and also with spectra of aquatic humic substances from available literature. Similar structural characteristics were observed for extracted DOM from the different seasons: high content of aliphatic structures, of hydroxy and alkoxy groups, of carbonyl groups and unsaturated carbon atoms, and low content in aromatic structures when compared with aliphatic structures. Moreover, results suggest that the DOM extracted

  12. Anaerobic decomposition of humic substances by Clostridium from the deep subsurface

    PubMed Central

    Ueno, Akio; Shimizu, Satoru; Tamamura, Shuji; Okuyama, Hidetoshi; Naganuma, Takeshi; Kaneko, Katsuhiko

    2016-01-01

    Decomposition of humic substances (HSs) is a slow and cryptic but non-negligible component of carbon cycling in sediments. Aerobic decomposition of HSs by microorganisms in the surface environment has been well documented; however, the mechanism of anaerobic microbial decomposition of HSs is not completely understood. Moreover, no microorganisms capable of anaerobic decomposition of HSs have been isolated. Here, we report the anaerobic decomposition of humic acids (HAs) by the anaerobic bacterium Clostridium sp. HSAI-1 isolated from the deep terrestrial subsurface. The use of 14C-labelled polycatechol as an HA analogue demonstrated that the bacterium decomposed this substance up to 7.4% over 14 days. The decomposition of commercial and natural HAs by the bacterium yielded lower molecular mass fractions, as determined using high-performance size-exclusion chromatography. Fourier transform infrared spectroscopy revealed the removal of carboxyl groups and polysaccharide-related substances, as well as the generation of aliphatic components, amide and aromatic groups. Therefore, our results suggest that Clostridium sp. HSAI-1 anaerobically decomposes and transforms HSs. This study improves our understanding of the anaerobic decomposition of HSs in the hidden carbon cycling in the Earth’s subsurface. PMID:26743007

  13. The physico-chemical properties and biostimulative activities of humic substances regenerated from lignite.

    PubMed

    David, Jan; Smejkalová, Daniela; Hudecová, Sárka; Zmeškal, Oldřich; von Wandruszka, Ray; Gregor, Tomáš; Kučerík, Jiří

    2014-01-01

    The positive effect of humic acids on the growth of plant roots is well known, however, the mechanisms and role of their physical structure in these processes have not been fully explained yet. In this work, South-Moravian lignite was oxidized by means of nitric acid and hydrogen peroxide to produce a set of regenerated humic acids. The elemental composition, solid state stability and solution characteristics were determined and correlated in vitro with their biological activity. A modified hydroponic method was applied to determine the effects of their potassium salts on Zea mays seedlings roots with respect to the plant weight, root length, root division, and starch and protein content. The relations between the determined parameters were evaluated through Principal Component Analysis and Pearson's correlation coefficients. The results indicated that the most important factor determining the biological activity of South-Moravian lignite potassium humates is related to the nature of self-assemblies, while the chemical composition had no direct connection with the root growth of Zea mays seedlings. It was demonstrated a controlled processing that provided humic substances with different chemical and physicochemical properties and variable biological activity. PMID:24790812

  14. Experimental evidence of incomplete fluorescence quenching of pyrene bound to humic substances: implications for Koc measurements.

    PubMed

    Shirshin, E A; Budylin, G S; Grechischeva, N Yu; Fadeev, V V; Perminova, I V

    2016-07-01

    Fluorescence quenching (FQ) is extensively used for quantitative assessment of partition coefficients (KOC) of polycyclic aromatic hydrocarbons (PAHs) to natural organic materials - humic substances (HS). The presence of bound PAHs with incompletely quenched fluorescence would lead to underestimation of the KOC values measured by this technique. The goal of this work was to prove the validity of this assumption using an original experimental setup, which implied FQ measurements upon excitation into two distinct vibronically coupled electronic states. Pyrene was used as a fluorescent probe, and aquatic fulvic acid (SRFA) and leonardite humic acid (CHP) were used as the humic materials with low and high binding affinity for pyrene, respectively. Excitation of pyrene into the forbidden (S0-S1) and allowed (S0-S2) electronic states yielded two pairs of nonidentical FQ curves. This was indicative of incomplete quenching of the bound pyrene, and the divergence of the two FQ curves was much more pronounced for CHP as compared to SRFA. The two component model of fluorescence response formation was proposed to estimate the KOC values from the data obtained. The resulting pyrene KOC value for CHP (220 ± 20) g L(-1) was a factor 3 higher compared to the KOC value determined with the use of the Stern-Volmer formalism (68 ± 2) g L(-1). At the same time for aquatic FA the difference in FQ curves was almost negligible, which enables the use of the Stern-Volmer formalism for weakly interacting HS and PAHs. PMID:27279258

  15. Fouling of a microfiltration membrane by humic-like substances: a mathematical approach to modelling permeate flux and membrane retention.

    PubMed

    Poorasgari, Eskandar; Farsi, Ali; Christensen, Morten Lykkegaard

    2016-01-01

    Membrane retention of the humic-like substances present in a soluble microbial products (SMP) suspension was studied by using a dead-end filtration system. The SMP suspension was extracted from the sludge of an enhanced biological phosphorus removal-membrane bioreactor. Our results showed that both adsorption and steric retention of the humic-like substances governed their transport through the membrane during the filtration. The adsorption, which followed pseudo-first order kinetics, did not cause substantial decline of permeate flux. The steric retention, on the other hand, formed a gel layer, which in turn led to a major decrease in the flux. The reduction of permeate flux was well predicted by cake filtration theory. Based on the adsorption and the steric retention, a new model was developed for predicting the overall membrane retention of the humic-like substances. The general trend of the modelled overall retention was in partial agreement with the experimental results. PMID:27332850

  16. Quantitative and mid-infrared changes of humic substances from burned soils.

    PubMed

    Vergnoux, A; Guiliano, M; Di Rocco, R; Domeizel, M; Théraulaz, F; Doumenq, P

    2011-02-01

    The humic substances are an abundant and important part of soil organic matter which plays many roles in ecosystems. On the other hand, forest fires are known to have a potential impact on the soil organic matter. Consequently, we chose to study the impact of forest fires on humic substances and the three relevant fractions, e.g. humic acids (HA), fulvic acids (FA) and non-humified fraction (NHF), NHF being the fulvic acids not adsorbed on XAD-8 resins. The studied site is a Mediterranean forest called "Maures Mountains", in France, where 30 sites were sampled in two layers: 0-5 and -5 to 15 cm. In order to validate the method, the 2 horizons from 5 sites randomly chosen were analyzed in triplicates. The extraction and fractionation procedures were achieved using alkali- and acid-solutions. The measurement of total organic carbon (TOC) using the TOC-meter and the use of Fourier transform infra-red (FTIR) spectroscopy gave us quantitative and qualitative results to evaluate the impact of forest fires and the role of their repetition. The results show that the fires led to significant decreases (Student test, P=0.05) of humic substances (HS), HA and of the fulvic fractions (FF=FA+NHF) in surface layers, corresponding to 40%, 34% and 35%, respectively. Moreover, the significant HA/FF ratio increases (Student test, P=0.05), as a result of the fire, indicate that NHF was probably transformed in FA-like compounds. About the qualitative impact, the results showed a significant decrease of alkyl and hydroxyl groups (OH), carboxylic acids and carbohydrates in HA after a wildfire, whereas the decrease was significant only for alkyl groups and carboxylic acids in FA. Lastly, the design of this work (control and burned sites, number of samples, time elapsed after fires, etc.) enables one to show the recovery of the Mediterranean forest ecosystem. FA quality and OH groups in HA are recovered between 3 and 16 years after the fire whereas alkyl groups, carboxylic acids and

  17. Study the properties of activated carbon and oxyhydroxide aluminum as sorbents for removal humic substances from natural waters

    NASA Astrophysics Data System (ADS)

    Shiyan, L. N.; Machekhina, K. I.; Gryaznova, E. N.

    2016-02-01

    The present work relates to the problem of high-quality drinking water supply using processes of adsorption on activated carbon and aluminum oxyhydroxide for removal humic- type organic substances. Also the paper reports on sorbtion properties of the activeted carbon Norit SA UF and oxyhydroxide aluminum for removal humic substances. It was found out that the maximum adsorption capacity of activated carbon to organic substances is equal to 0.25 mg/mg and aluminum oxyhydroxide is equal to 0.3 mg/mg. It is shown that the maximum adsorption capacity of activated carbon Norit SA UF to iron (III) ions is equal to 0.0045 mg/mg and to silicon ions is equal to 0.024 mg/mg. Consequently, the aluminum oxyhydroxide has better adsorption characteristics in comparison with the activated carbon for removal of humic substances, iron and silicon ions. It is associated with the fact that activated carbon has a large adsorption surface, and this is due to its porous structure, but not all molecules can enter into these pores. Therefore, the fibrous structure of aluminum oxyhydroxide promotes better sorption capacity. The presented results suggest that activated carbon Norit SA UF and aluminum oxyhydroxide can be used as sorbents for removal humic substances or other organic substances from groundwater and natural waters.

  18. Humic preperations from Russian lignites

    SciTech Connect

    Rodeh, V.V.; Ryzhkov, O.G.

    1994-12-31

    THe objective of this work was to study lignites as the precursor materials to humic substances. Lignites contain humic substances primarily as humic acids. Their extraction requires the processing of coals with alkali.

  19. Characterization and diagenesis of strong-acid carboxyl groups in humic substances

    USGS Publications Warehouse

    Leenheer, J.A.; Wershaw, R. L.; Brown, G.K.; Reddy, M.M.

    2003-01-01

    A small fraction of carboxylic acid functional groups in humic substances are exceptionally acidic with pKa values as low as 0.5. A review of acid-group theory eliminated most models and explanations for these exceptionally acidic carboxyl groups. These acidic carboxyl groups in Suwannee River fulvic acid were enriched by a 2-stage fractionation process and the fractions were characterized by elemental, molecular-weight, and titrimetric analyses, and by infrared and 13C- and 1H-nuclear magnetic resonance spectrometry. An average structural model of the most acidic fraction derived from the characterization data indicated a high density of carboxyl groups clustered on oxygen-heterocycle alicyclic rings. Intramolecular H-bonding between adjacent carboxyl groups in these ring structures enhanced stabilization of the carboxylate anion which results in low pKa1 values. The standard, tetrahydrofuran tetracarboxylic acid, was shown to have similar acidity characteristics to the highly acidic fulvic acid fraction. The end products of 3 known diagenetic pathways for the formation of humic substances were shown to result in carboxyl groups clustered on oxygen-heterocycle alicyclic rings.

  20. Improving Lowland Rice (O. sativa L. cv. MR219) Plant Growth Variables, Nutrients Uptake, and Nutrients Recovery Using Crude Humic Substances.

    PubMed

    Palanivell, Perumal; Ahmed, Osumanu Haruna; Ab Majid, Nik Muhamad; Jalloh, Mohamadu Boyie; Susilawati, Kasim

    2015-01-01

    High cation exchange capacity and organic matter content of crude humic substances from compost could be exploited to reduce ammonia loss from urea and to as well improve rice growth and soil chemical properties for efficient nutrients utilization in lowland rice cultivation. Close-dynamic air flow system was used to determine the effects of crude humic substances on ammonia volatilization. A pot experiment was conducted to determine the effects of crude humic substances on rice plant growth, nutrients uptake, nutrients recovery, and soil chemical properties using an acid soil mixed with three rates of crude humic substances (20, 40, and 60 g pot(-1)). Standard procedures were used to evaluate rice plant dry matter production, nutrients uptake, nutrients recovery, and soil chemical properties. Application of crude humic substances increased ammonia volatilization. However, the lowest rate of crude humic substances (20 g pot(-1)) significantly improved total dry matter, nutrients uptake, nutrients recovery, and soil nutrients availability compared with crude humic substances (40 and 60 g pot(-1)) and the normal fertilization. Apart from improving growth of rice plants, crude humic substances can be used to ameliorate acid soils in rice cultivation. The findings of this study are being validated in our ongoing field trials. PMID:25977938

  1. Improving Lowland Rice (O. sativa L. cv. MR219) Plant Growth Variables, Nutrients Uptake, and Nutrients Recovery Using Crude Humic Substances

    PubMed Central

    Palanivell, Perumal; Ahmed, Osumanu Haruna; Ab Majid, Nik Muhamad; Jalloh, Mohamadu Boyie; Susilawati, Kasim

    2015-01-01

    High cation exchange capacity and organic matter content of crude humic substances from compost could be exploited to reduce ammonia loss from urea and to as well improve rice growth and soil chemical properties for efficient nutrients utilization in lowland rice cultivation. Close-dynamic air flow system was used to determine the effects of crude humic substances on ammonia volatilization. A pot experiment was conducted to determine the effects of crude humic substances on rice plant growth, nutrients uptake, nutrients recovery, and soil chemical properties using an acid soil mixed with three rates of crude humic substances (20, 40, and 60 g pot−1). Standard procedures were used to evaluate rice plant dry matter production, nutrients uptake, nutrients recovery, and soil chemical properties. Application of crude humic substances increased ammonia volatilization. However, the lowest rate of crude humic substances (20 g pot−1) significantly improved total dry matter, nutrients uptake, nutrients recovery, and soil nutrients availability compared with crude humic substances (40 and 60 g pot−1) and the normal fertilization. Apart from improving growth of rice plants, crude humic substances can be used to ameliorate acid soils in rice cultivation. The findings of this study are being validated in our ongoing field trials. PMID:25977938

  2. Fluorescence spectroscopy as a tool for quality assessment of humic substances

    NASA Astrophysics Data System (ADS)

    Boguta, Patrycja

    2016-04-01

    *The studies were partly carried out within the framework of a research project. The project was financed from funds of National Science Center on the base of decision number DEC-2013/11/D/NZ9/02545. Fluorescence spectroscopy belongs to modern, non-destructive, rapid and relatively cheap methods, as well as for many years it was successfully used in studies of organic compounds in the fields of medicine, biology and chemistry. On the other hand, soil organic matter is a group of compounds with a complex spatial structure showing a large number of groups with different kinds of fluorophores. This could suggest the possibility of application of fluorescence spectroscopy in assessing the quality of humic substances as well as in monitoring of their chemical transformations. The aim of study was chemical description of humic and fulvic acids based on fluorescence spectra, as well as an attempt of evaluation of changes occurring under the influence of different pH and during interactions with various concentrations of metal. The humic and fulvic acids were isolated from chemically different soils. The measurements were carried out on Hitachi fluorescence spectrometer in solutions with a concentration of humic acids 40mg dm-3, at pH from 3 to 7, and for the evaluation of the metal impact: with increasing Zn concentrations (0-50mg dm-3). The fluorescence spectra were recorded in the form of synchronous and emission-excitation matrices (EEM). Studies have shown the presence of different groups of fluorophores. Synchronous spectra were characterized by a well-separated bands showing fluorescence in the area of low, medium and high wavelengths, suggesting the presence of structures, both weakly and strongly humified. EEM spectra revealed map of fluorophores within wide ranges of emission and excitation. Fluorophores differed in both position and intensity. The highest intensity was observed for compounds with the lowest humification degree which might be due to high amount

  3. X-ray absorption spectroscopic evidence for the complexation of Hg(II) by reduced sulfur in soil humic substances

    SciTech Connect

    Xia, K.; Skyllberg, U.L.; Bleam, W.F.; Helmke, P.A.; Bloom, P.R.; Nater, E.A.

    1999-01-15

    Analysis of Hg(II) complexed by a soil humic acid (HA) using synchrotron-based X-ray absorption spectroscopy (XAS) revealed the importance of reduces sulfur functional groups (thiol (R-SH) and disulfide (R-SS-R)/disulfane (R-SSH)) in humic substances in the complexation of Hg(II). A two-coordinate binding environment with one oxygen atom and one sulfur atom at distances of 2.02 and 2.38 {angstrom}, respectively, was found in the first coordination shell of Hg(II) complexed by humic acid. Model calculations show that a second coordination sphere could contain one carbon atom and a second sulfur atom at 2.78 and 2.93 {angstrom}, respectively. This suggests that in addition to thiol S, disulfide/disulfane S may be involved with the complexation of Hg(II) in soil organic matter. The appearance of carbon atom in the second coordination shell suggests that one O-containing ligand such as carboxyl and phenol ligands rather than H{sub 2}O molecule is bound to the Hg(II). The involvement of oxygen ligand in addition to the reduced S ligands in the complexation of Hg(II) is due to the low density of reduced S ligands in humic substances. The XAS results from this experiment provided direct molecular level evidence for the preference of reduced S functional groups over oxygen ligands by Hg(II) in the complexation with humic substances.

  4. Humic substances in natural waters and their complexation with trace metals and radionuclides: a review. [129 references

    SciTech Connect

    Boggs, S. Jr.; Livermore, D.; Seitz, M.G.

    1985-07-01

    Dissolved humic substances (humic and fulvic acids) occur in surface waters and groundwaters in concentrations ranging from less than 1 mg(C)/L to more than 100 mg(C)/L. Humic substances are strong complexing agents for many trace metals in the environment and are also capable of forming stable soluble complexes or chelates with radionuclides. Concentrations of humic materials as low as 1 mg(C)/L can produce a detectable increase in the mobility of some actinide elements by forming soluble complexes that inhibit sorption of the radionuclides onto rock materials. The stability of trace metal- or radionuclide-organic complexes is commonly measured by an empirically determined conditional stability constant (K'), which is based on the ratio of complexed metal (radionuclide) in solution to the product concentration of uncomplexed metal and humic complexant. Larger values of stability constants indicate greater complex stability. The stability of radionuclide-organic complexes is affected both by concentration variables and envionmental factors. In general, complexing is favored by increased of radionuclide, increased pH, and decreased ionic strength. Actinide elements are generally most soluble in their higher oxidation states. Radionuclides can also form stable, insoluble complexes with humic materials that tend to reduce radionuclide mobility. These insoluble complexes may be radionuclide-humate colloids that subsequently precipitate from solution, or complexes of radionuclides and humic substances that sorb to clay minerals or other soil particulates strongly enough to immobilize the radionuclides. Colloid formation appears to be favored by increased radionuclide concentration and lowered pH; however, the conditions that favor formation of insoluble complexes that sorb to particulates are still poorly understood. 129 refs., 25 figs., 19 tabs.

  5. Lanthanide humic substances complexation. I. Experimental evidence for a lanthanide contraction effect

    NASA Astrophysics Data System (ADS)

    Sonke, Jeroen E.; Salters, Vincent J. M.

    2006-03-01

    The interaction of the lanthanides (Ln) with humic substances (HS) was investigated with a novel chemical speciation tool, Capillary Electrophoresis-Inductively Coupled Plasma Mass Spectrometry (CE-ICP-MS). By using an EDTA-ligand competition method, a bi-modal species distribution of LnEDTA and LnHS is attained, separated by CE, and detected online by sector field ICP-MS. We quantified the binding of all 14 rare earth elements (REEs), Sc and Y with Suwannee river fulvic acid, Leonardite coal humic acid, and Elliot soil humic acid under environmental conditions (pH 6-9, 0.001-0.1 mol L -1 NaNO 3, 1-1000 nmol L -1 Ln, 10-20 mg L -1 HS). Conditional binding constants for REE-HS interaction ( Kc) ranged from 8.9 < log Kc < 16.5 under all experimental conditions, and display a lanthanide contraction effect, ΔLKc: a gradual increase in Kc from La to Lu by 2-3 orders of magnitude as a function of decreasing ionic radius. HS polyelectrolyte effects cause Kc to increase with increasing pH and decreasing ionic strength. ΔLKc increases significantly with increasing pH, and likely with decreasing ionic strength. Based on a strong correlation between ΔLKc values and denticity for organic acids, we suggest that HS form a range of tri- to tetra-dentate complexes under environmental conditions. These results confirm HS to be a strong complexing agent for Ln, and show rigorous experimental evidence for potential REE fractionation by HS complexation.

  6. PREDICTING CHEMICAL REACTIVITY OF HUMIC SUBSTANCES FOR MINERALS AND XENOBIOTICS: USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY AND VIRTUAL REALITY

    EPA Science Inventory

    In this chapter we review the literature on scanning probe microscopy (SPM), virtual reality (VR), and computational chemistry and our earlier work dealing with modeling lignin, lignin-carbohydrate complexes (LCC), humic substances (HSs) and non-bonded organo-mineral interactions...

  7. A humic substance analogue AQDS stimulates Geobacter sp. abundance and enhances pentachlorophenol transformation in a paddy soil.

    PubMed

    Chen, Manjia; Tong, Hui; Liu, Chengshuai; Chen, Dandan; Li, Fangbai; Qiao, Jiangtao

    2016-10-01

    Soil humic substances can be used as redox mediators in accelerating the biotransformation of organic pollutants, and humus-respiring bacteria are widely distributed in soils. However, the impact of humic substances on the soil microbial community during the biotransformation of organic pollutants is expected to be crucial while remains to be unclear. In this study, the biostimulation of indigenous microbial communities and the consequent effects on anaerobic transformation of pentachlorophenol (PCP) by a model humic substance, anthraquinone-2,6-disulfonate (AQDS), were systematically investigated in a paddy soil. The addition of AQDS was observed to increase the production of HCl-extractable Fe(II) and enhance the PCP transformation rates consequently. The pseudo-first-order rate constants of the PCP transformation showed a positive exponential relationship with the AQDS dosage. The terminal restriction fragment length polymorphism (T-RFLP) results indicated the substantial effect of added AQDS on soil microbial community. The enhanced abundance of Geobacter sp. was disclosed to be most critical for accelerated PCP transformation when with AQDS, in which Geobacter sp. functioned for promoting the generation of active Fe(II) and consequently enhancing the PCP transformation rates. The transformation rates of PCP were exponentially correlated with the abundance of Geobacter sp. positively. The findings are expected to improve the understanding of diversity and ubiquity of microorganisms in humic substances-rich soils for accelerating the transformations of soil chlorinated pollutants. PMID:27372263

  8. MODELING OF METAL BINDING ON HUMIC SUBSTANCES USING THE NIST DATABASE: AN A PRIORI FUNCTIONAL GROUP APPROACH

    EPA Science Inventory

    Various modeling approaches have been developed for metal binding on humic substances. However, most of these models are still curve-fitting exercises-- the resulting set of parameters such as affinity constants (or the distribution of them) is found to depend on pH, ionic stren...

  9. Characterization of humic substances in salt marsh soils under sea rush ( Juncus maritimus)

    NASA Astrophysics Data System (ADS)

    Santín, C.; González-Pérez, M.; Otero, X. L.; Vidal-Torrado, P.; Macías, F.; Álvarez, M. Á.

    2008-09-01

    Humic substances (HS) from salt marsh soils were characterized and the relationships among HS composition and some geochemical factors were analysed. For this, three salt marshes with the same vegetation cover ( Juncus maritimus), but with different geochemical characteristics, were selected. The qualitative characterization of the soil humic acids and fulvic acids was carried out by elemental analysis, FTIR spectroscopy, fluorescence spectroscopy and VACP/MAS 13C NMR spectroscopy. HS from salt marsh soils under sea rush ( Juncus maritimus) displayed some shared characteristics such as low degree of humification, low aromatic content and high proportion of labile compounds, mainly polysaccharides and proteins. However, although the three salt marsh soils under study were covered by the same type of vegetation, the HS showed some important differences. HS composition was found to be determined not only by the nature of the original organic material, but also by environmental factors such as soil texture, redox conditions and tidal influence. In general, an increase in the humification process appeared to be related to aerobic conditions and predominance of sand in the mineral fraction of the soil, while the preservation of labile organic compounds may be associated with low redox potential values and fine soil texture.

  10. Multidimensional fluorescence studies of the phenolic content of dissolved organic carbon in humic substances.

    PubMed

    Pagano, Todd; Ross, Annemarie D; Chiarelli, Joseph; Kenny, Jonathan E

    2012-03-01

    Indicators suggest that the amount of dissolved organic carbon (DOC) in natural waters may be increasing. Climate change has been proposed as a potential contributor to the trend, and under such a mechanism, the phenolic content of DOC may also be increasing. This study explores the assessment of the phenolic character of DOC using multidimensional fluorescence spectroscopy as a more convenient alternative to traditional wet chemistry methods. Parallel factor analysis (PARAFAC) is applied to fluorescence excitation emission matrices (EEMs) of humic samples to analyze inherent phenolic content. The PARAFAC results are correlated with phenol concentrations derived from the Folin-Ciocalteau reagent-based method. The reagent-based method reveals that the phenolic content of five International Humic Substance Society (IHSS) samples varies from approximately 5.2 to 22 ppm Tannic Acid Equivalents (TAE). A four-component PARAFAC fit is applied to the EEMs of the IHSS sample dataset and it is determined by PARAFAC score correlations with phenol concentrations from the reagent-based method that components C2, C3, and C4 have the highest probability of containing phenolic groups. The results show the potential for PARAFAC analysis of multidimensional fluorescence data for monitoring the phenolic content of DOC. PMID:22278717

  11. Effects of humic substances on the heavy metal removal and the phytotoxicity of pesticide

    SciTech Connect

    Yang, J.E.; Shin, Y.K.; Rhee, H.I.; Kim, J.J.

    1995-12-31

    Efficiency of humic (HA) or fulvic acid (FA) on the removal of Cu or Pb from aqueous solution and phytotoxicity of Paraquat were assessed using the principle of contaminant-ligand complexation. Increasing HA concentrations enhanced the efficiency of Cu or Pb removal, up to a critical ligand concentration capable of forming a maximum HA-metal complex. Removal efficiency ranged from 70 to 95% for Pb, but only 13 to 65% for Cu. HA of 100mg was estimated to complex with 7.5 mg of Cu and 34.1 mg of Pb. Fulvic acid removed nearly 100% of Pb, but only 13 to 29% of Cu. The reactions followed the first- or multiple first-order kinetics depending on the concentrations of metal and ligand, pH and temperature. Paraquat alone exerted a high degree of phytotoxicity at low concentration to the hydroponically grown rye (Secale cereale L.), but the presence of HA or FA decreased the Paraquat toxicity up to 40% and enhanced the yield and growth of rye up to 20% indicating that humic substances reduced the bioavailability of paraquat to rye due to the complexation.

  12. Effects of humic substances and quinones at low concentrations on ferrihydrite reduction by Geobacter metallireducens.

    PubMed

    Wolf, Manfred; Kappler, Andreas; Jiang, Jie; Meckenstock, Rainer U

    2009-08-01

    Humic substances (HS) and quinones can accelerate dissimilatory Fe(III) reduction by electron shuttling between microorganisms and poorly soluble iron(III) (hydr)oxides. The mechanism of electron shuttling for HS is not fully understood, but it is suggested that the most important redox-active components in HS are also quinones. Here we studied the influence of HS and different quinones at low concentrations on ferrihydrite reduction by Geobacter metallireducens. The aquatic HS used were humic and fulvic acids (HA and FA) isolated from groundwater of a deep aquifer in Gorleben (Niedersachsen, Germany). HA stimulated iron reduction stronger than FA down to total HA concentrations as low as 1 mg/L. The quinones studied showed large differences: some had strong accelerating effects, whereas others showed only small effects, no effects, or even inhibitory effects on the kinetics of iron reduction. We found that the redox potentials of the most active quinones fall in a narrow range of -137 to -225 mV vs NHE at pH 7. These results give evidence that the kinetic of microbial iron reduction mediated by electron shuttles is mainly controlled by thermodynamic parameters, i.e., by the redox potential of the shuttle compound, rather than by the proportion of dissolved vs adsorbed compound. PMID:19731662

  13. Chemistry and transport of soluble humic substances in forested watersheds of the Adirondack Park, New York

    USGS Publications Warehouse

    Cronan, C.S.; Aiken, G.R.

    1985-01-01

    Studies were conducted in conjunction with the Integrated Lake-Watershed Acidification Study (ILWAS) to examine the chemistry and leaching patterns of soluble humic substances in forested watersheds of the Adirondack region. During the summer growing season, mean dissolved organic carbon (DOC) concentrations in the ILWAS watersheds ranged from 21-32 mg C l-1 in O/A horizon leachates, from 5-7 mg C l-1 in B horizon leachates, from 2-4 mg C l-1 in groundwater solutions, from 6-8 mg C l-1 in first order streams, from 3-8 mg C l-1 in lake inlets, and from 2-7 mg C l-1 in lake outlets. During the winter, mean DOC concentrations dropped significantly in the upper soil profile. Soil solutions from mixed and coniferous stands contained as much as twice the DOC concentration of lysimeter samples from hardwood stands. Results of DOC fractionation analysis showed that hydrophobia and hydrophilic acids dominate the organic solute composition of natural waters in these watersheds. Charge balance and titration results indicated that the general acid-base characteristics of the dissolved humic mixture in these natural waters can be accounted for by a model organic acid having an averagepKa of 3.85, an average charge density of 4-5 ??eq mg-1 C at ambient pH, and a total of 6-7 meq COOH per gram carbon. ?? 1985.

  14. Chemistry and transport of soluble humic substances in forested watersheds of the Adirondack Park, New York

    NASA Astrophysics Data System (ADS)

    Cronan, Christopher S.; Aiken, George R.

    1985-08-01

    Studies were conducted in conjunction with the Integrated Lake-Watershed Acidification Study (ILWAS) to examine the chemistry and leaching patterns of soluble humic substances in forested watersheds of the Adirondack region. During the summer growing season, mean dissolved organic carbon (DOC) concentrations in the ILWAS watersheds ranged from 21-32 mg C l-1 in O/A horizon leachates, from 5-7 mg C l-1 in B horizon leachates, from 2-4 mg C l-1 in groundwater solutions, from 6-8 mg C l-1 in first order streams, from 3-8 mg C l-1 in lake inlets, and from 2-7 mg C l-1 in lake outlets. During the winter, mean DOC concentrations dropped significantly in the upper soil profile. Soil solutions from mixed and coniferous stands contained as much as twice the DOC concentration of lysimeter samples from hardwood stands. Results of DOC fractionation analysis showed that hydrophobia and hydrophilic acids dominate the organic solute composition of natural waters in these watersheds. Charge balance and titration results indicated that the general acid-base characteristics of the dissolved humic mixture in these natural waters can be accounted for by a model organic acid having an averagepKa of 3.85, an average charge density of 4-5 μeq mg-1 C at ambient pH, and a total of 6-7 meq COOH per gram carbon.

  15. Mitigation of Fe(0) nanoparticles toxicity to Trichosporon cutaneum by humic substances.

    PubMed

    Pádrová, Karolína; Maťátková, Olga; Šiková, Michaela; Füzik, Tibor; Masák, Jan; Čejková, Alena; Jirků, Vladimír

    2016-01-25

    Zero-valent iron nanoparticles (nZVI) are a relatively new option for the treatment of contaminated soil and groundwater. However, because of their apparent toxicity, nZVI in high concentrations are known to interfere with many autochthonous microorganisms and, thus, impact their participation in the remediation process. The effect of two commercially available nZVI products, Nanofer 25 (non-stabilized) and Nanofer 25S (stabilized), was examined. Considerable toxicity to the soil yeast Trichosporon cutaneum was observed. Two chemically different humic substances (HSs) were studied as a possible protection agent that mitigates nZVI toxicity: oxidized oxyhumolite X6 and humic acid X3A. The effect of addition of HSs was studied in different phases of the experiment to establish the effect on cells and nZVI. SEM and TEM images revealed an ability of both types of nZVI and HSs to adsorb on surface of the cells. Changes in cell surface properties were also observed by zeta potential measurements. Our results indicate that HSs can act as an electrosteric barrier, which hinders mutual interaction between nZVI and treated cell. Thus, the application of HS seems to be a promising solution to mitigating the toxic action of nZVI. PMID:26455640

  16. Reducing capacities and redox potentials of humic substances extracted from sewage sludge.

    PubMed

    Yang, Zhen; Du, Mengchan; Jiang, Jie

    2016-02-01

    Humic substances (HS) are redox active organic materials that can be extracted from sewage sludge generated in wastewater treatment processes. Due to the poor understanding of reducing capacity, redox potentials and redox active functional groups of HS in sewage sludge, the potential contribution of sludge HS in transformation of wastewater contaminants is unclear. In the present study, the number of electrons donated or accepted by sewage sludge HS were quantified before and after reduction by iron compounds that possess different redox potentials and defined as the reducing capacity of the sewage sludge. In contrast to previous studies of soil and commercial humic acids (HA), reduced sludge HA showed a lower reducing capacity than that of native HA, which implies formation of semiquinone radicals since the semiquinone radical/hydroquinone pair has a much higher redox potential than the quinone/hydroquinone pair. It is novel that reducing capacities of sludge HA were determined in the redox potential range from -314 to 430 mV. The formation of semiquinone radicals formed during the reduction of quinone moieties in sludge HA is shown by three-dimensional excitation/emission matrix fluorescence spectroscopies information, increasing fluorescence intensities and blue-shifting of the excitation/emission peak of reduced sludge HA. Knowledge of sludge HS redox potentials and corresponding reducing capacities makes it possible to predict the transformation of redox active pollutants and facilitate manipulation and optimization of sludge loading wastewater treatment processes. PMID:26432531

  17. Novel electrochemical approach to assess the redox properties of humic substances.

    PubMed

    Aeschbacher, Michael; Sander, Michael; Schwarzenbach, René P

    2010-01-01

    Two electrochemical methods to assess the redox properties of humic substances (HS) are presented: direct electrochemical reduction (DER) on glassy carbon working electrodes (WE) and mediated electrochemical reduction (MER) and oxidation (MEO) using organic radicals to facilitate electron transfer between HS and the WE. DER allows for continuous monitoring of electron and proton transfer to HS by chronocoulometry and automated acid titration, respectively, and of changes in bulk HS redox potential E(h). Leonardite Humic Acid (LHA) showed an H(+)/e(-) ratio of unity and a decrease in potential from E(h) = +0.18 to -0.23 V upon transfer of 822 mumol(e-) g(LHA)(-1) at pH 7, consistent with quinones as major redox-active functional moieties in LHA. MER and MEO quantitatively detected electrons in LHA samples that were prereduced by DER to different extents. MER and MEO therefore accurately quantify the redox state of HS. Cyclic DER and O(2)-reoxidation revealed that electron transfer to LHA was largely reversible. However, LHA contained a small pool of moieties that were not reoxidized, likely due to endergonic first electron transfer to O(2). Electron accepting capacities of 13 different HS, determined by MER, strongly correlated with their C/H ratios and aromaticities and with previously published values, which, however, were a factor of 3 smaller due to methodological limitations. PMID:19950897

  18. Monitoring transitory profiles of leachate humic substances in landfill aeration reactors in mesophilic and thermophilic conditions.

    PubMed

    Tong, Huanhuan; Yin, Ke; Ge, Liya; Giannis, Apostolos; Chuan, Valerie W L; Wang, Jing-Yuan

    2015-04-28

    The presence of humic substances (HS) in landfill leachate is of great interest because of their structural stability and potential toxicity. This study examined the effects of temperature and waste age on the transformation of HS during in situ aeration of bioreactor landfills. By establishing aerobic conditions, dissolved organic carbon (DOC) rapidly accumulated in the bioreactor leachate. Fractional analysis showed that the elevated concentration of humic acids (HAs) was primarily responsible for the increment of leachate strength. Further structural characterization indicated that the molecular weight (MW) and aromacity of HS were enhanced by aeration in conjunction with thermophilic temperature. Interestingly, elevation of HAs concentration was not observed in the aeration reactor with a prolonged waste age, as the mobility of HAs was lowered by the high MW derived from extended waste age. Based on these results, aeration may be more favorable in aged landfills, since dissolution of HAs could be minimized by the evolution to larger MW compared to young landfills. Moreover, increased operation temperature during aeration likely offers benefits for the rapid maturation of HS. PMID:25682368

  19. Investigation of humic substance photosensitized reactions via carbon and hydrogen isotope fractionation.

    PubMed

    Zhang, Ning; Schindelka, Janine; Herrmann, Hartmut; George, Christian; Rosell, Mònica; Herrero-Martín, Sara; Klán, Petr; Richnow, Hans H

    2015-01-01

    Humic substances (HS) acting as photosensitizers can generate a variety of reactive species, such as OH radicals and excited triplet states ((3)HS*), promoting the degradation of organic compounds. Here, we apply compound-specific stable isotope analysis (CSIA) to characterize photosensitized mechanisms employing fuel oxygenates, such as methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), as probes. In oxygenated aqueous media, Λ (Δδ(2)H/Δδ(13)C) values of 23 ± 3 and 21 ± 3 for ETBE obtained by photosensitization by Pahokee Peat Humic Acid (PPHA) and Suwannee River Fulvic Acid (SRFA), respectively, were in the range typical for H-abstraction by OH radicals generated by photolysis of H2O2 (Λ = 24 ± 2). However, (3)HS* may become a predominant reactive species upon the quenching of OH radicals (Λ = 14 ± 1), and this process can also play a key role in the degradation of ETBE by PPHA photosensitization in deoxygenated media (Λ = 11 ± 1). This is in agreement with a model photosensitization by rose bengal (RB(2-)) in deoxygenated aqueous solutions resulting in one-electron oxidation of ETBE (Λ = 14 ± 1). Our results demonstrate that the use of CSIA could open new avenues for the assessment of photosensitization pathways. PMID:25427194

  20. Chitosan nanoparticles loaded the herbicide paraquat: the influence of the aquatic humic substances on the colloidal stability and toxicity.

    PubMed

    Grillo, Renato; Clemente, Zaira; de Oliveira, Jhones Luis; Campos, Estefânia Vangelie Ramos; Chalupe, Victor C; Jonsson, Claudio M; de Lima, Renata; Sanches, Gabriela; Nishisaka, Caroline S; Rosa, André H; Oehlke, Kathleen; Greiner, Ralf; Fraceto, Leonardo F

    2015-04-01

    Polymeric nanoparticles have been developed for several applications, among them as carrier system of pesticides. However, few studies have investigated the fate of these materials in the environment in relation to colloidal stability and toxicity. In nature, humic substances are the main agents responsible for complexation with metals and organic compounds, as well as responsible for the dynamics of these nanoparticles in aquatic and terrestrial environments. In this context, the evaluation of the influence of aquatic humic substances (AHS) on the colloidal stability and toxicity of polymeric nanoparticles of chitosan/tripolyphosphate with or without paraquat was performed. In this study, the nanoparticles were prepared by the ionic gelation method and characterized by size distribution measurements (DLS and NTA), zeta potential, infrared and fluorescence spectroscopy. Allium cepa genotoxicity studies and ecotoxicity assays with the alga Pseudokirchneriella subcapitata were used to investigate the effect of aquatic humic substances (AHS) on the toxicity of this delivery system. No changes were observed in the physical-chemical stability of the nanoparticles due to the presence of AHS using DLS and NTA techniques. However some evidence of interaction between the nanoparticles and AHS was observed by infrared and fluorescence spectroscopies. The ecotoxicity and genotoxicity assays showed that humic substances can decrease the toxic effects of nanoparticles containing paraquat. These results are interesting because they are important for understanding the interaction of these nanostructured carrier systems with species present in aquatic ecosystems such as humic substances, and in this way, opening new perspectives for studies on the dynamics of these carrier systems in the ecosystem. PMID:25636059

  1. Characterization of the International Humic Substances Society standard and reference fulvic and humic acids by solution state carbon-13 (13C) and hydrogen-1 (1H) nuclear magnetic resonance spectrometry

    USGS Publications Warehouse

    Thorn, Kevin A.; Folan, Daniel W.; MacCarthy, Patrick

    1989-01-01

    Standard and reference samples of the International Humic Substances Society have been characterized by solution state carbon-13 and hydrogen-1 nuclear magnetic resonance (NMR) spectrometry. Samples included the Suwannee River, soil, and peat standard fulvic and humic acids, the Leonardite standard humic acid, the Nordic aquatic reference fulvic and humic acids, and the Summit Hill soil reference humic acid. Aqueous-solution carbon-13 NMR analyses included the measurement of spin-lattice relaxation times, measurement of nuclear Overhauser enhancement factors, measurement of quantitative carbon distributions, recording of attached proton test spectra, and recording of spectra under nonquantitative conditions. Distortionless enhancement by polarization transfer carbon-13 NMR spectra also were recorded on the Suwannee River fulvic acid in deuterated dimethyl sulfoxide. Hydrogen-1 NMR spectra were recorded on sodium salts of the samples in deuterium oxide. The carbon aromaticities of the samples ranged from 0.24 for the Suwannee River fulvic acid to 0.58 for the Leonardite humic acid.

  2. Atmospheric SO2 emissions since the late 1800s change organic sulfur forms in humic substance extracts of soils.

    PubMed

    Lehmann, Johannes; Solomon, Dawit; Zhao, Fang-Jie; McGrath, Steve P

    2008-05-15

    Atmospheric SO2 emissions in the UK and globally increased 6- and 20-fold, respectively, from the mid-1800s to the 1960s resulting in increased S deposition, acid rain, and concurrent acidification of terrestrial and aquatic ecosystems. Structural analyses using synchrotron-based X-ray near-edge spectroscopy (XANES) on humic substance extracts of archived samples from the Rothamsted Park Grass Experiment reveal a significant (R2 = -0.58; P < 0.05; N = 7) shift in soil organic sulfur (S) forms, from reduced to more oxidized organic S between 1876 and 1981, even though soil total S contents remained relatively constant. Over the last 30 years, a decrease in emissions and consequent S deposition has again corresponded with a change of organic S structures of humic extracts-reverting in the direction of their early industrial composition. However, the observed reversal lagged behind reductions in emissions by 19 years, which was computed using cross correlations between time series data (R2 = 0.66; P = 0.0024; N = 11). Presently, the ratio of oxidized-to-reduced organic S in humic substance extracts is nearly double that of early industrial times at identical SO2 emission loads. The significant and persistent structural changes of organic S in humic substances as a response to SO2 emissions and S deposition may have effects on recuperation of soils and surface waters from acidification. PMID:18546688

  3. Atmospheric So2 Emissions Since the Late 1800s Change Organic Sulfur Forms in Humic Substance Extracts of Soils

    SciTech Connect

    Lehmann,J.; Solomon, D.; Zhao, F.; McGrath, S.

    2008-01-01

    Atmospheric SO2 emissions in the UK and globally increased 6- and 20-fold, respectively, from the mid-1800s to the 1960s resulting in increased S deposition, acid rain, and concurrent acidification of terrestrial and aquatic ecosystems. Structural analyses using synchrotron-based X-ray near-edge spectroscopy (XANES) on humic substance extracts of archived samples from the Rothamsted Park Grass Experiment reveal a significant (R2 = -0.58; P < 0.05; N = 7) shift in soil organic sulfur (S) forms, from reduced to more oxidized organic S between 1876 and 1981, even though soil total S contents remained relatively constant. Over the last 30 years, a decrease in emissions and consequent S deposition has again corresponded with a change of organic S structures of humic extractsreverting in the direction of their early industrial composition. However, the observed reversal lagged behind reductions in emissions by 19 years, which was computed using cross correlations between time series data (R2 = 0.66; P = 0.0024; N = 11). Presently, the ratio of oxidized-to-reduced organic S in humic substance extracts is nearly double that of early industrial times at identical SO2 emission loads. The significant and persistent structural changes of organic S in humic substances as a response to SO2 emissions and S deposition may have effects on recuperation of soils and surface waters from acidification.

  4. INFLUENCE OF BORATE BUFFERS ON THE ELECTROPHORETIC BEHAVIOR OF HUMIC SUBSTANCES IN CAPILLARY ZONE ELECTROPHORESIS

    EPA Science Inventory

    The influence of tetrahydroxyborate ions on the electrophoretic mobility of humic acids was evaluated by capillary electrophoresis (CE). Depending on the molarity of borate ions in the separation buffer, the humic acids exhibit electropherograms with sharp peaks consistently exte...

  5. A meta-analysis of plant-growth response to humic substance applications

    NASA Astrophysics Data System (ADS)

    Patti, Antonio; Rose, Michael; Little, Karen; Jackson, Roy; Cavagnaro, Tim

    2013-04-01

    Humic substances (HS) are a category of naturally occurring organic compounds that arise from the decomposition and transformation of plant, animal and microbial residues (Maccarthy 2001). The loss of humic material, together with overall reductions in soil organic matter, is of concern because they play important roles in maintaining key soil functions and plant productivity (Lal 2004). Consequently, there is interest in the application of HS-based amendments, often derived from agricultural wastes (e.g composts) to remediate and/or maintain soil health (Quilty and Cattle 2011). In light of the potential benefits of HS, together with their inconsistent performance under field conditions, we sought to quantitatively review the effects of HS on plant growth, by undertaking a meta-analysis of the literature. A total of 390 papers were originally selected from the current literature. A number of criteria were applied to reduce this number to 81, from which the meta-analysis was undertaken. The 81 papers comprised 57 studies presenting data on shoot (or total) dry weight and 39 studies reporting root dry weight. As part of the meta-analysis we attempted: (i) to quantify the magnitude and likelihood of plant growth promotion, in terms of shoot and root biomass, resulting from HS application, (ii) to determine the influence of environmental conditions, plant type, humic substance properties, and the manner of application on plant growth response to HS, (iii) to identify gaps in our understanding of the interaction of HS with plants, and (iv) to provide some general recommendations for the practical use of HS in agronomic systems and suggestions for future work. Some of the key findings from this meta-analysis included: Many papers lack details on HS chemical characteristics The application of HS needs to be tailored to the environmental conditions in which they will be used. The effect of HS on shoot biomass was not only dependent on the source and rate of application

  6. Characterization of humic substances by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Mugo, Samuel M; Bottaro, Christina S

    2004-01-01

    Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and laser desorption/ionization (LDI-)TOFMS have been used to characterize Suwannee River humic substances, obtained from the International Humic Substances Society (IHSS), and Armadale soil fulvic acid (ASFA). An array of MALDI matrices were tested for use with humic substances, including alpha-cyano-4-hydroxycinammic acid (CHCA), 2-(4-hydroxyphenylazo)benzoic acid (HABA), 2,5-dihydroxybenzoic acid (DHBA), sinapinic acid, dithranol and norharmane. DHBA yielded the best results, exhibiting superior ionization efficiency, low noise, broad applicability to the analytes of interest, and most importantly producing an abundance of high mass ions, the highest observed being m/z 1848. A number of sample preparation modes were investigated; the overlayer method improved sample/matrix homogeneity and hence shot-to-shot reproducibility. The choice of the matrix, mass ratio of analyte to matrix, and the sample preparation protocol, were found to be the most critical factors governing the quality of the mass spectra. Matrix suppression was greatly enhanced by ensuring good mixing of matrix and analyte in the solid phase, proper optimization of the matrix/analyte ratio, and optimizing delayed extraction to ensure complete matrix-analyte reaction in the plume before ions are moved to the flight tube. A number of common features, in particular specific ions which could not be attributed to the matrices or to contaminants, were present in the spectra of all the humic substances, regardless of origin or operational definition. Additionally, a prominent repeating pattern of peaks separated by 55, 114 and 169 Da was clearly observed in both LDI and MALDI, suggesting that the humic compounds studied here may have quasi-polymeric or oligomeric features. PMID:15386633

  7. Impact of humic substances on the aqueous solubility, uptake and bioaccumulation of platinum, palladium and rhodium in exposure studies with Dreissena polymorpha.

    PubMed

    Sures, Bernd; Zimmermann, Sonja

    2007-03-01

    Zebra mussels (Dreissena polymorpha) were exposed to different types of water containing PGE salts (PtCl4, PdSO4, RhCl3) to investigate the influence of humic substances on the aqueous solubility, uptake and bioaccumulation of noble metals. The results showed a time dependent decrease of the aqueous PGE concentrations in tank water for all groups. This could mainly be related to non-biological processes. The aqueous solubility of Pd and Rh was higher in humic water compared with non-chlorinated tap water, whereas Pt showed opposing results. Highest metal uptake rates and highest bioaccumulation plateaus were found for Pd, followed by Pt and Rh. Pd uptake and bioaccumulation was significantly hampered by humic substances, whose presence appear to increase Pt uptake and bioaccumulation. No clear trend emerged for Rh. Differences in effects of humic matter among the PGE may be explained by formation of metal complexes with different fractions of humic substances. PMID:17018243

  8. Hydrogeochemical and mineralogical investigations of arsenic- and humic substance-enriched aquifers

    NASA Astrophysics Data System (ADS)

    Liu, Chen-Wuing; Lai, Chih-Chieh; Chen, Yen-Yu; Lu, Kuang-Liang

    2013-08-01

    This study investigated the hydrogeochemical and mineralogical characteristics of arsenic-contaminated and humic-substance-enriched aquifers in the Chianan Plain, Taiwan, which is an endemic area for blackfoot disease (BFD). Factorial analysis (FA) was used to evaluate the hydrochemical characteristics of 83 groundwater samples in the Chianan Plain, and 462 geological core samples obtained from 9 drilling wells were collected to analyze their arsenic and iron contents. The major mineral phases and chemical components were determined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy and energy dispersive spectrometry (SEM-EDS). Partition of arsenic among various hosting solids in sediments was determined by sequential extraction. The results of FA showed that the hydrochemical characteristics of the groundwater samples could be grouped by 4 factors: salinization, arsenic, sulfide, and iron. Arsenic was positively correlated with alkalinity, dissolved organic/inorganic carbon, and fluorescence intensity [humic acids, (HAs)]. As(V) has a higher chelating affinity with HAs than does As(III), resulting in higher As(V) concentrations distributed throughout the reducing environment. High levels and correlations of As and HAs may cause BFD in the Chianan Plain. No correlation was found between the measured and calculated redox potentials of the various redox couples. The As(III)/As(V) was under a chemical non-equilibrium condition. The vertical distribution of the sedimentary As (solid phase) typically increased with depth, but the aqueous As concentrations were higher in the second aquifer (depth of 80-120 m). Arsenic content (solid phase) was higher in the clay/silt sediments and marine formations. The major minerals identified by XPS and SEM-EDS were goethite, hematite, magnetite, pyrite, and siderite, agreeing with the SI values calculated by PHREEQC. Arsenic content was strongly correlated with sulfur (weight%; R2

  9. Comprehensive characterization of oil refinery effluent-derived humic substances using various spectroscopic approaches.

    PubMed

    Lingbo, Li; Song, Yan; Congbi, Han; Guangbo, Shan

    2005-07-01

    Refinery effluent-derived humic substances (HS) are important for developing refinery effluent reclamation techniques and studying the environmental chemistry of wastewater effluents. In this study, dissolved organic matter (DOM) from refinery effluent was concentrated using a portable reverse osmosis (RO) system. HS were isolated from RO retentates with XAD-8 resin. A variety of approaches such as specific UV absorbance at 254nm (SUV(254)), elemental analysis, size exclusion chromatography (SEC), solid-state cross polarization magic angle spinning (13)C nuclear magnetic resonance spectrometry ((13)C CPMAS NMR), Fourier transform infrared spectrometry (FTIR), and electrospray ionization/ion trap/mass spectrometry (ESI/ion trap/MS) were employed for characterization of HS. The portable RO system exhibited high yield and recovery of DOM for concentrating refinery effluent. The concentration of dissolved organic carbon (DOC) in the refinery effluent was 9.9mg/l, in which humic acids (HA) and fulvic acids (FA) accounted for 2.3% and 34.6%, respectively. Elemental and SUV(254) analyses indicated relative high amounts of aliphatic structures and low amounts of aromatic structures in refinery effluent-derived HS. Refinery effluent-derived HS displayed lower molecular weight than natural HS. The number-average molecular weight (M(n)) and the weight-average molecular weight (M(w)) of HA were 1069 and 2934, and those of FA were 679 and 1212 by SEC, respectively. By ESI/ion trap/MS, the M(n) and the M(w) of FA were 330 and 383. Four kinds of carbon structures (aliphatic, aromatic, heteroaliphatic, and carboxylic carbons) were found in refinery effluent-derived HS by (13)C NMR analysis. The quantitative results support the interpretation that these HS are rich in aliphatic carbons and poor in aromatic carbons. Proteinaceous materials were identified by FTIR analysis in refinery effluent-derived HS. PMID:15950039

  10. Effect of humic substance photodegradation on bacterial growth and respiration in lake water.

    PubMed

    Anesio, Alexandre M; Granéli, Wilhelm; Aiken, George R; Kieber, David J; Mopper, Kenneth

    2005-10-01

    This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-microm-pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H2O2 photoproduction. The H2O2 decayed in the dark, and after 43 h, nearly all irradiated HSs enhanced BCP (average 39% increase relative to nonirradiated controls, standard error = 7.5%, n = 16). UV exposure of HSs also increased bacterial respiration (by approximately 18%, standard error = 5%, n = 4), but less than BCP, resulting in an average increase in BGE of 32% (standard error = 10%, n = 4). Photoenhancement of BCP did not correlate to HS bulk properties (i.e., elemental and chemical composition). However, when the photoenhancement of BCP was normalized to absorbance, several trends with HS origin and extraction method emerged. Absorbance-normalized hydrophilic acid and humic acid samples showed greater enhancement of BCP than hydrophobic acid and fulvic acid samples. Furthermore, absorbance-normalized autochthonous samples showed approximately 10-fold greater enhancement of BCP than allochthonous-dominated samples, indicating that the former are more efficient photoproducers of biological substrates. PMID:16204548

  11. Effect of Humic Substance Photodegradation on Bacterial Growth and Respiration in Lake Water

    PubMed Central

    Anesio, Alexandre M.; Granéli, Wilhelm; Aiken, George R.; Kieber, David J.; Mopper, Kenneth

    2005-01-01

    This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-μm-pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H2O2 photoproduction. The H2O2 decayed in the dark, and after 43 h, nearly all irradiated HSs enhanced BCP (average 39% increase relative to nonirradiated controls, standard error = 7.5%, n = 16). UV exposure of HSs also increased bacterial respiration (by ∼18%, standard error = 5%, n = 4), but less than BCP, resulting in an average increase in BGE of 32% (standard error = 10%, n = 4). Photoenhancement of BCP did not correlate to HS bulk properties (i.e., elemental and chemical composition). However, when the photoenhancement of BCP was normalized to absorbance, several trends with HS origin and extraction method emerged. Absorbance-normalized hydrophilic acid and humic acid samples showed greater enhancement of BCP than hydrophobic acid and fulvic acid samples. Furthermore, absorbance-normalized autochthonous samples showed ∼10-fold greater enhancement of BCP than allochthonous-dominated samples, indicating that the former are more efficient photoproducers of biological substrates. PMID:16204548

  12. Humic substances increase survival of freshwater shrimp Caridina sp. D to acid mine drainage.

    PubMed

    Holland, Aleicia; Duivenvoorden, Leo J; Kinnear, Susan H W

    2013-02-01

    Humic substances (HS) are known to decrease the toxicity of heavy metals to aquatic organisms, and it has been suggested that they can provide buffering protection in low pH conditions. Despite this, little is known about the ability for HS to increase survival to acid mine drainage (AMD). In this study, the ability of HS to increase survival of the freshwater shrimp (Caridina sp. D sensu Page et al. in Biol Lett 1:139-142, 2005) to acid mine drainage was investigated using test waters collected from the Mount Morgan open pit in Central Queensland with the addition of Aldrich humic acid (AHA). The AMD water from the Mount Morgan open pit is highly acidic (pH 2.67) as well as contaminated with heavy metals (1780 mg/L aluminum, 101 mg/L copper [Cu], 173 mg/L manganese, 51.8 mg/L zinc [Zn], and 51.8 mg/L iron). Freshwater shrimp were exposed to dilutions in the range of 0.5 % to 5 % AMD water with and without the addition of 10 or 20 mg/L AHA. In the absence of HS, all shrimp died in the 2.5 % AMD treatment. In contrast, addition of HS increased survival in the 2.5 % AMD treatment by ≤66 % as well as significantly decreased the concentration of dissolved Cu, cobalt, cadmium, and Zn. The decreased toxicity of AMD in the presence of HS is likely to be due to complexation and precipitation of heavy metals with the HS; it is also possible that HS caused changes to the physiological condition of the shrimp, thus increasing their survival. These results are valuable in contributing to an improved understanding of potential role of HS in ameliorating the toxicity of AMD environments. PMID:23135152

  13. Effect of humic substance photodegradation on bacterial growth and respiration in lake water

    USGS Publications Warehouse

    Anesio, A.M.; Graneli, W.; Aiken, G.R.; Kieber, D.J.; Mopper, K.

    2005-01-01

    This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-??m-pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H 2O2 photoproduction. The H2O2 decayed in the dark, and after 43 h, nearly all irradiated HSs enhanced BCP (average 39% increase relative to nonirradiated controls, standard error = 7.5%, n = 16). UV exposure of HSs also increased bacterial respiration (by ???18%, standard error = 5%, n = 4), but less than BCP, resulting in an average increase in BGE of 32% (standard error = 10%, n = 4). Photoenhancement of BCP did not correlate to HS bulk properties (i.e., elemental and chemical composition). However, when the photoenhancement of BCP was normalized to absorbance, several trends with HS origin and extraction method emerged. Absorbance-normalized hydrophilic acid and humic acid samples showed greater enhancement of BCP than hydrophobic acid and fulvic acid samples. Furthermore, absorbance-normalized autochthonous samples showed ???10-fold greater enhancement of BCP than allochthonous-dominated samples, indicating that the former are more efficient photoproducers of biological substrates. Copyright ?? 2005, American Society for Microbiology. All Rights Reserved.

  14. Quantification of carbohydrate structures in size fractionated aquatic humic substances by two-dimensional nuclear magnetic resonance.

    PubMed

    Haiber, S; Herzog, H; Burba, P; Gosciniak, B; Lambert, J

    2001-03-01

    Two-dimensional phase sensitive C,H correlation spectra were successfully applied to the quantification of carbohydrate substructures in aquatic humic substance (HS) fractions obtained by tangential flow multistage ultrafiltration (TFMSTUF) of a selected bog water HS (HO13, German Research Program DFG-ROSIG) as well as a river HS (Suwannee River Fulvic Acid Reference of the International Humic Substances Society, IHSS). It turns out that after size fractionation the HS samples give very well resolved C,H-correlation spectra which offer a great potential for substructure quantification. Details of the combined substructure quantification technique, novel in HS characterization, are presented. The results of the combined procedure point out that carbohydrate moieties predominantly occur in higher molecular mass fractions (> 10 kDa) of isolated HS. PMID:11270229

  15. DRIFT and HR MAS NMR characterization of humic substances from a soil treated with different organic and mineral fertilizers

    NASA Astrophysics Data System (ADS)

    Ferrari, Erika; Francioso, Ornella; Nardi, Serenella; Saladini, Monica; Ferro, Nicola Dal; Morari, Francesco

    2011-07-01

    In this study, using DRIFT and HR MAS NMR, we analyzed the humic substances isolated from a soil treated, over 40 years, with different organic, mineral and organic plus mineral treatments and cultivated with maize as the main crop. As expected, the structure of humic substances was very complex but by combining both techniques (DRIFT and HR MAS NMR) additional information was obtained on aromatic and aliphatic components, the most recalcitrant parts of these macromolecules. In so doing we wanted to investigate the relationship between HS structure and long-term management practices. An elevated content of lignin, aminoacids, peptides and proteins was observed mainly for farmyard manure treatments with respect to mineral or liquid manure amendments; this supports how the different management practices have greatly influenced the humification process of cultivated soils.

  16. Effects of pH and natural humic substances on the accumulation of organic pollutants in two freshwater invertebrates

    NASA Astrophysics Data System (ADS)

    Kukkonen, Jussi

    The present study focused on the accumulation of benzo(a)pyrene (BaP), hexachlorocyclohexane (lindane), pentachlorophenol (PCP) and dehydroabietic acid (DHAA), from a natural humic water (DOC 18 mg/l) and a humus-free reference water, in Daphnia magna (Cladocera) and nymphs of the mayfly Heptagenia fuscogrisea (Ephemeroptera). Effects of water pH ranging from 3.5 to 8.5 was examined. The partition coefficients (Kp) of BaP and PCP to organic material were measured by equilibrium dialysis, and in both cases increases in Kp values were noticed with decreasing pH. For neutral compounds (BaP and lindane), the bioconcentration factor (BCF) was the highest at pH 6.5 in the control water. Humic substances significantly lowered the accumulation of BaP, but had no effect on the accumulation of lindane. The lowest test pH gave the highest BCF value, and increasing pH decreased the BCF values of weak organic acids (PCP and DHAA) in the control experiments. This was because the unionized forms of these compounds accumulate better than the more hydrophilic ionized forms. The presence of dissolved organic substances lowered the accumulation of PCP in H. fuscogrisea between pH 4.5 and 7.5 and had no effect at pHs 3.5 and 8.5. Humic substances lowered the accumulation of DHAA in D. magna between pH 5.5 and 6.5 and had no effect when pH was over 7. In experiments with H. fuscogrisea humic substances had no effect on the accumulation of DHAA.

  17. Investigating nitrate-dependent humic substance oxidation and in-service K-12 teachers' understanding of microbiology

    NASA Astrophysics Data System (ADS)

    Jones, Nastassia N.

    2011-12-01

    Humic substances (HS) are the humified portions of totally decomposed soil organic matter that are ubiquitous in nature. Although these substances have been studied for more than 200 years, neither their metabolic capabilities nor a specific chemical structure has yet to be determined. HS have been studied as a carbon source in many environments where they are degraded; however, previous studies have shown that some microorganisms are capable of utilizing humic substances as electron acceptors and electron donors in anaerobic respiration. Even though there have been humic-reducing and humic-oxidizing microorganisms isolated and studied in recent years, the mechanism of humics metabolism and its interaction in the natural environment are not well understood. However, it is known that the continuous change in the redox state of HS is important to the cycling of iron, stability of nitrogen and carbon, and the mobility and bioavailability of inorganic and organic environmental pollutants. In this study, microbial communities were examined to evaluate the community dynamics of nitrate-dependent HS-oxidizing populations and to provide a snapshot of the phylogenetic diversity of these microorganisms. Column studies were performed using nitrate as the sole electron acceptor and the following as the electron donors in different columns: reduced humic acids, oxidized humic acids, and acetate as the control. Liquid buffered media was added to a separate column to serve as an additional control. Polymerase chain reactions of the 16S rRNA genes using DNA from the column studies were performed and analyzed by constructing 16S rDNA clone libraries and by performing denaturing gradient gel electrophoresis (DGGE). Clones from the library have been sequenced and analyzed to paint a phylogenetic picture of the microbial community under the various conditions. Results indicate that the majority of the clones were assigned to four well-characterized divisions, the Acidobacteria, the

  18. Photocatalytic degradation of humic substances in aqueous solution using Cu-doped ZnO nanoparticles under natural sunlight irradiation.

    PubMed

    Maleki, Afshin; Safari, Mahdi; Shahmoradi, Behzad; Zandsalimi, Yahya; Daraei, Hiua; Gharibi, Fardin

    2015-11-01

    In this study, Cu-doped ZnO nanoparticles were investigated as an efficient synthesized catalyst for photodegradation of humic substances in aqueous solution under natural sunlight irradiation. Cu-doped ZnO nanocatalyst was prepared through mild hydrothermal method and was characterized using FT-IR, powder XRD and SEM techniques. The effect of operating parameters such as doping ratio, initial pH, catalyst dosage, initial concentrations of humic substances and sunlight illuminance were studied on humic substances degradation efficiency. The results of characterization analyses of samples confirmed the proper synthesis of Cu-doped ZnO nanocatalyst. The experimental results indicated the highest degradation efficiency of HS (99.2%) observed using 1.5% Cu-doped ZnO nanoparticles at reaction time of 120 min. Photocatalytic degradation efficiency of HS in a neutral and acidic pH was much higher than that at alkaline pH. Photocatalytic degradation of HS was enhanced with increasing the catalyst dosage and sunlight illuminance, while increasing the initial HS concentration led to decrease in the degradation efficiency of HS. Conclusively, Cu-doped ZnO nanoparticles can be used as a promising and efficient catalyst for degradation of HS under natural sunlight irradiation. PMID:26104905

  19. Monitoring changes in the structure and properties of humic substances following ozonation using UV-Vis, FTIR and (1)H NMR techniques.

    PubMed

    Rodríguez, Francisco J; Schlenger, Patrick; García-Valverde, María

    2016-01-15

    The main objective of this work is to conduct a comprehensive structural characterization of humic substances using the following experimental techniques: FTIR, 1H NMR and several UV–Vis parameters (Specific UV Absorbance at 254 nm or SUVA254, SUVA280, A400, the absorbance ratios A210/254, A250/365, A254/203, A254/436, A265/465, A270/400, A280/350, A465/665, the Absorbance Slope Index (ASI), the spectral slopes S275–295, S350–400 and the slope ratio SR). These UV–Vis parameters have also been correlated with key properties of humic substances such as aromaticity, molecular weight (MW) and trihalomethane formation potential (THMFP). An additional objective of this work is also to evaluate the usefulness of these techniques to monitor structural changes in humic substances produced by the ozonation treatment. Four humic substances were studied in this work: three of them were provided by the International Humic Substances Society (Suwannee River Fulvic Acid Standard: SRFA, Suwannee River Humic Acid Standard: SRHA and Nordic Reservoir Fulvic Acid Reference: NLFA) and the other one was a terrestrial humic acid widely used as a surrogate for aquatic humic substances in various studies (Aldrich Humic Acid: AHA). The UV–Vis parameters showing the best correlations with aromaticity in this study were SUVA254, SUVA280, A280/A350 ratio and A250/A364 ratio. The best correlations with molecular weight were for SUVA254, SUVA280 and A280/A350 ratio. Finally, in the case of the THMFP it was STHMFP-per mol HS the parameter showing good correlations with most of the UV–Vis parameters studied (especially with A280/A350 ratio, A265/A465 ratio and A270/A400 ratio) whereas STHMFP-per mg C showed poor correlations in most cases. On the whole, the UV–Vis parameter showing the best results was A280/A350 ratio as it showed excellent correlations for the three properties studied (aromaticity, MW and THMFP). A decrease in aromaticity following ozonation of humic substances can

  20. Sulfur and nitrogen speciation in humic substances by x-ray absorption near-edge structure spectroscopy

    SciTech Connect

    Vairavamurthy, M.A.; Wang, Shenghe; Maletic, D.

    1996-12-31

    Understanding the chemical composition and structure of complex macromolecules in the geosphere, such as humic substances and kerogen, poses a challenging analytical problem. Widely used chromatographic techniques, such as the pyrolysis GC-MS, cause severe changes in structure during preparation and analysis of the sample, and thus, may not give accurate information. An important non-destructive technique that is becoming popular in speciation studies of environmental and geochemical samples is x-ray absorption fine structure spectroscopy. We used the x-ray absorption near-edge structure (XANFS) spectroscopy for examining the speciation of sulfur and nitrogen in humic substances of different origins, including soil and marine sediments. XANES provides information on the characteristics of the functional groups containing these atoms because of its sensitivity to the electronic structure, oxidation state, and the geometry of the neighboring atoms. Organic sulfides, di- and poly-sulfides, sulfonates and organic sulfates are the major forms of sulfur detected in all the humics we examined. The oxidized sulfonate-sulfur dominates the composition of sulfur species in soil humics accounting for more than 60% of the total sulfur. In marine humics, although sulfonates are abundant in near-surface sediments, reduced sulfur species, particularly di-and poly-sulfides, also constitute an important fraction. The nitrogen XANES indicates the dominance of amino and amide groups among nitrogen functionalities, although porphyrinic and pyridinic groups also are present. The significance of these results for the transformations of nitrogen and sulfur in soil and sedimentary systems will be presented.

  1. Photoreduction of Terrigenous Fe‐Humic Substances Leads to Bioavailable Iron in Oceans

    PubMed Central

    Blazevic, Amir; Orlowska, Ewelina; Kandioller, Wolfgang; Jirsa, Franz; Keppler, Bernhard K.; Tafili‐Kryeziu, Myrvete; Linert, Wolfgang; Krachler, Rudolf F.; Krachler, Regina

    2016-01-01

    Abstract Humic substances (HS) are important iron chelators responsible for the transport of iron from freshwater systems to the open sea, where iron is essential for marine organisms. Evidence suggests that iron complexed to HS comprises the bulk of the iron ligand pool in near‐coastal waters and shelf seas. River‐derived HS have been investigated to study their transport to, and dwell in oceanic waters. A library of iron model compounds and river‐derived Fe‐HS samples were probed in a combined X‐ray absorption spectroscopy (XAS) and valence‐to‐core X‐ray emission spectroscopy (VtC‐XES) study at the Fe K‐edge. The analyses performed revealed that iron complexation in HS samples is only dependent on oxygen‐containing HS functional groups, such as carboxyl and phenol. The photoreduction mechanism of FeIII‐HS in oceanic conditions into bioavailable aquatic FeII forms, highlights the importance of river‐derived HS as an iron source for marine organisms. Consequently, such mechanisms are a vital component of the upper‐ocean iron biogeochemistry cycle.

  2. Photoreduction of Terrigenous Fe‐Humic Substances Leads to Bioavailable Iron in Oceans

    PubMed Central

    Blazevic, Amir; Orlowska, Ewelina; Kandioller, Wolfgang; Jirsa, Franz; Keppler, Bernhard K.; Tafili‐Kryeziu, Myrvete; Linert, Wolfgang; Krachler, Rudolf F.; Krachler, Regina

    2016-01-01

    Abstract Humic substances (HS) are important iron chelators responsible for the transport of iron from freshwater systems to the open sea, where iron is essential for marine organisms. Evidence suggests that iron complexed to HS comprises the bulk of the iron ligand pool in near‐coastal waters and shelf seas. River‐derived HS have been investigated to study their transport to, and dwell in oceanic waters. A library of iron model compounds and river‐derived Fe‐HS samples were probed in a combined X‐ray absorption spectroscopy (XAS) and valence‐to‐core X‐ray emission spectroscopy (VtC‐XES) study at the Fe K‐edge. The analyses performed revealed that iron complexation in HS samples is only dependent on oxygen‐containing HS functional groups, such as carboxyl and phenol. The photoreduction mechanism of FeIII‐HS in oceanic conditions into bioavailable aquatic FeII forms, highlights the importance of river‐derived HS as an iron source for marine organisms. Consequently, such mechanisms are a vital component of the upper‐ocean iron biogeochemistry cycle. PMID:27100573

  3. Determination of humic substances in natural waters by cathodic stripping voltammetry of their complexes with iron.

    PubMed

    Laglera, Luis M; Battaglia, Gianluca; van den Berg, Constant M G

    2007-09-01

    A new voltammetric method is presented for the measurement of humic substances (HS) in natural waters. The method is based on catalytic cathodic stripping voltammetry (CSV) and makes use of adsorptive properties of iron-HS complexes on the mercury drop electrode at natural pH. A fulvic acid standard (IHSS) was used to confirm the voltammetric response (peak potential and sensitivity) for the HS for natural water samples. Optimized conditions included the linear-sweep mode, deposition at -0.1 V, pH buffered at 8 and a scan rate of 50 mV s(-1). At a deposition time of 240 s in the presence of 10 nM iron and 30 mM bromate, the detection limit was 5 microg L(-1) HS in seawater, which could be lowered further by an increase in the bromate concentration, or in the adsorption time. The method was used to determine HS in the Irish Sea which were found to occur at levels between 60 and 600 microg L(-1). The new method is sufficiently sensitive to detect the low HS content in oceanic samples and has implications to the study of iron speciation. PMID:17765064

  4. Development of an automated system for isolation and purification of humic substances.

    PubMed

    van Zomeren, André; van der Weij-Zuiver, Esther; Comans, Rob N J

    2008-07-01

    Characterization of humic substances (HS) in environmental samples generally involves labor-intensive and time-consuming isolation and purification procedures. In this paper, the development of an automated system for HS isolation and purification is described. The novelty of the developed system lies in the way the multiple liquids and columns used in the isolation/purification procedure are handled in both forward and back-elution mode by solenoid valves. The automated procedure significantly reduces the total throughput time needed, from 6-7 days to 48 h, and the amount of labor to obtain purified HS for further characterization. Chemical characterization of purified HS showed that results were in good agreement with previously published values for HS from a variety of sources, including the IHSS standard HS collection. It was also shown that the general properties of HS were consistent among the different source materials (soil, waste, aquatic) used in this study. The developed system greatly facilitates isolation and characterization of HS and reduces the risk of potential (time-dependent) alteration of HS properties in the manual procedure. PMID:18488204

  5. Photoreduction of Terrigenous Fe-Humic Substances Leads to Bioavailable Iron in Oceans.

    PubMed

    Blazevic, Amir; Orlowska, Ewelina; Kandioller, Wolfgang; Jirsa, Franz; Keppler, Bernhard K; Tafili-Kryeziu, Myrvete; Linert, Wolfgang; Krachler, Rudolf F; Krachler, Regina; Rompel, Annette

    2016-05-23

    Humic substances (HS) are important iron chelators responsible for the transport of iron from freshwater systems to the open sea, where iron is essential for marine organisms. Evidence suggests that iron complexed to HS comprises the bulk of the iron ligand pool in near-coastal waters and shelf seas. River-derived HS have been investigated to study their transport to, and dwell in oceanic waters. A library of iron model compounds and river-derived Fe-HS samples were probed in a combined X-ray absorption spectroscopy (XAS) and valence-to-core X-ray emission spectroscopy (VtC-XES) study at the Fe K-edge. The analyses performed revealed that iron complexation in HS samples is only dependent on oxygen-containing HS functional groups, such as carboxyl and phenol. The photoreduction mechanism of Fe(III) -HS in oceanic conditions into bioavailable aquatic Fe(II) forms, highlights the importance of river-derived HS as an iron source for marine organisms. Consequently, such mechanisms are a vital component of the upper-ocean iron biogeochemistry cycle. PMID:27100573

  6. Maillard Chemistry in Clouds and Aqueous Aerosol As a Source of Atmospheric Humic-Like Substances.

    PubMed

    Hawkins, Lelia N; Lemire, Amanda N; Galloway, Melissa M; Corrigan, Ashley L; Turley, Jacob J; Espelien, Brenna M; De Haan, David O

    2016-07-19

    The reported optical, physical, and chemical properties of aqueous Maillard reaction mixtures of small aldehydes (glyoxal, methylglyoxal, and glycolaldehyde) with ammonium sulfate and amines are compared with those of aqueous extracts of ambient aerosol (water-soluble organic carbon, WSOC) and the humic-like substances (HULIS) fraction of WSOC. Using a combination of new and previously published measurements, we examine fluorescence, X-ray absorbance, UV/vis, and IR spectra, complex refractive indices, (1)H and (13)C NMR spectra, thermograms, aerosol and electrospray ionization mass spectra, surface activity, and hygroscopicity. Atmospheric WSOC and HULIS encompass a range of properties, but in almost every case aqueous aldehyde-amine reaction mixtures are squarely within this range. Notable exceptions are the higher UV/visible absorbance wavelength dependence (Angström coefficients) observed for methylglyoxal reaction mixtures, the lack of surface activity of glyoxal reaction mixtures, and the higher N/C ratios of aldehyde-amine reaction products relative to atmospheric WSOC and HULIS extracts. The overall optical, physical, and chemical similarities are consistent with, but not demonstrative of, Maillard chemistry being a significant secondary source of atmospheric HULIS. However, the higher N/C ratios of aldehyde-amine reaction products limits the source strength to ≤50% of atmospheric HULIS, assuming that other sources of HULIS incorporate only negligible quantities of nitrogen. PMID:27227348

  7. Structural characterization of humic-like substances with conventional and surface-enhanced spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Carletti, Paolo; Roldán, Maria Lorena; Francioso, Ornella; Nardi, Serenella; Sanchez-Cortes, Santiago

    2010-10-01

    Emission-excitation, synchronous fluorescence spectroscopy and surface-enhanced Raman scattering (SERS) combined with surface-enhanced fluorescence (SEF) were applied to aqueous solutions of a humic-like substance (HLS) extracted from earthworm faeces. All measurements were acquired in a wide range of pH (4-12) and analysed by the linear regression analysis. Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectra were also acquired to assist in the structural characterization of this HLS. The emission and excitation spectra allowed the identification of two main fluorophores in the analysed sample. Moreover, a close correlation between fluorescence intensities of each fluorophore with pH variation was observed. SERS and SEF, in agreement with the fluorescence spectroscopy, showed that the HLS at low pH values exists in an aggregated and coiled molecular structure while it is dispersed and uncoiled at alkaline conditions. The obtained spectra also evidenced that different conditions modify the functional groups exposed to the surrounding aqueous environment.

  8. Interaction of arsenic species with tropical river aquatic humic substances enriched with aluminum and iron.

    PubMed

    de Oliveira, Lilian Karla; Melo, Camila de Almeida; Fraceto, Leonardo Fernandes; Friese, Kurt; Rosa, André Henrique

    2016-04-01

    The mobility and bioavailability of arsenic (As) are strongly controlled by adsorption/precipitation processes involving metal oxides. However, the organic matter present in the environment, in combination with these oxides, can also play an important role in the cycle of arsenic. This work concerns the interaction between As and two samples of aquatic humic substances (AHS) from tropical rivers. The AHS were extracted as proposed by IHSS, and were characterized by (13)C NMR. The experiments were conducted with the AHS in natura and enriched with metal cations, with different concentrations of As, and complexation capacity was evaluated at three different pH levels (5.0, 7.0, and 9.0). The AHS samples showed similar chemical compositions. The results suggested that there was no interaction between As(III) and AHS in natura or enriched with Al. Low concentrations of As(V) were bound to AHS in natura. For As(III), the complexation capacity of the AHS enriched with Fe was approximately 48 μmol per g of C, while the values for As(V) were in the range 69-80 μmol per grams of C. Fluorescence spectra showed that changes in Eh affected the complexation reactions of As(V) species with AHS. PMID:26606934

  9. Pollutant toxicity and detoxification by humic substances: mechanisms and quantitative assessment via luminescent biomonitoring.

    PubMed

    Kudryasheva, N S; Tarasova, A S

    2015-01-01

    The paper considers mechanisms of detoxification of pollutant solutions by water-soluble humic substances (HSs), natural detoxifying agents. The problems and perspectives of bioassay application for toxicity monitoring of complex solutions are discussed from ecological point of view. Bioluminescence assays based on marine bacteria and their enzymes are of special attention here; they were shown to be convenient tools to study the detoxifying effects on cellular and biochemical levels. The advantages of bioluminescent enzymatic assay for monitoring both integral and oxidative toxicities in complex solutions of model pollutants and HS were demonstrated. The efficiencies of detoxification of the solutions of organic oxidizers and salts of metals (including radioactive ones) by HS were analyzed. The dependencies of detoxification efficiency on time of exposure to HS and HS concentrations were demonstrated. Antioxidant properties of HS were considered in detail. The detoxifying effects of HS were shown to be complex and regarded as 'external' (binding and redox processes in solutions outside the organisms) and/or 'internal' organismal processes. The paper demonstrates that the HS can stimulate a protective response of bacterial cells as a result of (1) changes of rates of biochemical reactions and (2) stabilization of mucous layers outside the cell walls. Acceleration of auto-oxidation of NADH, endogenous reducer, by HS was suggested as a reason for toxicity increase in the presence of HS due to abatement of reduction ability of intracellular media. PMID:25146119

  10. Comparison of isolation and quantification methods to measure humic-like substances (HULIS) in atmospheric particles

    NASA Astrophysics Data System (ADS)

    Fan, Xingjun; Song, Jianzhong; Peng, Ping'an

    2012-12-01

    Humic-like Substances (HULIS) comprise a significant fraction of the water-soluble organic aerosol mass and influence the cloud microphysical properties and climate effects of aerosols in the atmosphere. In this work, the most frequently used HULIS isolation and quantification methods including ENVI-18, HLB, XAD-8 and DEAE were comparatively characterized with two model standards, ten interfering compounds, and five ambient aerosol samples. Quantification of HULIS is performed with a TOC analyzer, complemented by an investigation of the chemical structure of the extracted fractions by UV-Vis spectroscopy. The results show that the four isolation methods were all characterized by high reliability, high reproducibility, and low limit of detection (LOD), indicating that each method can be used to efficiently recover Suwannee River Fulvic Acid (SRFA) and be applied to the quantification of the lower amount of HULIS in atmospheric particles. The analytical results of the UV-Vis spectra of HULIS fractions isolated also indicate that they are all favorable for extraction of compounds of high UV absorbance, high MW, and high aromaticity and that the DEAE protocol is the most significant one. Compared with the DEAE method that favors extraction of highly UV-absorbing and more aromatic compounds, SRFA isolated by the ENVI-18, HLB, and XAD-8 protocols were more representative of the global matrix. Each method has its own advantages and disadvantages and is suitable for a particular application. No single method is ideal for both isolation and quantification of HULIS in atmospheric samples.

  11. Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades

    USGS Publications Warehouse

    Hoch, A.R.; Reddy, M.M.; Aiken, G.R.

    2000-01-01

    The crystallization of calcium carbonate minerals plays an integral role in the water chemistry of terrestrial ecosystems. Humic substances, which are ubiquitous in natural waters, have been shown to reduce or inhibit calcite crystal growth in experiments. The purpose of this study is to quantify and understand the kinetic effects of hydrophobic organic acids isolated from the Florida Everglades and a fulvic acid from Lake Fryxell, Antarctica, on the crystal growth of calcite (CaCO3). Highly reproducible calcite growth experiments were performed in a sealed reactor at constant pH, temperature, supersaturation (?? = 4.5), P(CO2) (10-3.5atm), and ionic strength (0.1 M) with various concentrations of organic acids. Higher plant-derived aquatic hydrophobic acids from the Everglades were more effective growth inhibitors than microbially derived fulvic acid from Lake Fryxell. Organic acid aromaticity correlated strongly with growth inhibition. Molecular weight and heteroatom content correlated well with growth inhibition, whereas carboxyl content and aliphatic nature did not. Copyright (C) 1999 Elsevier Science Ltd.

  12. Effects of humic substances on precipitation and aggregation of zinc sulfide nanoparticles

    USGS Publications Warehouse

    Deonarine, A.; Lau, B.L.T.; Aiken, G.R.; Ryan, J.N.; Hsu-Kim, H.

    2011-01-01

    Nanoparticulate metal sulfides such as ZnS can influence the transport and bioavailability of pollutant metals in anaerobic environments. The aim of this work was to investigate how the composition of dissolved natural organic matter (NOM) influences the stability of zinc sulfide nanoparticles as they nucleate and aggregate in water with dissolved NOM. We compared NOM fractions that were isolated from several surface waters and represented a range of characteristics including molecular weight, type of carbon, and ligand density. Dynamic light scattering was employed to monitor the growth and aggregation of Zn-S-NOM nanoparticles in supersaturated solutions containing dissolved aquatic humic substances. The NOM was observed to reduce particle growth rates, depending on solution variables such as type and concentration of NOM, monovalent electrolyte concentration, and pH. The rates of growth increased with increasing ionic strength, indicating that observed growth rates primarily represented aggregation of charged Zn-S-NOM particles. Furthermore, the observed rates decreased with increasing molecular weight and aromatic content of the NOM fractions, while carboxylate and reduced sulfur content had little effect. Differences between NOM were likely due to properties that increased electrosteric hindrances for aggregation. Overall, results of this study suggest that the composition and source of NOM are key factors that contribute to the stabilization and persistence of zinc sulfide nanoparticles in the aquatic environment. ?? 2011 American Chemical Society.

  13. Effects of humic substance on precipitation and aggregation of zinc sulfide nanoparticles

    USGS Publications Warehouse

    Deonarine, Amrika; Lau, Boris L.T.; Aiken, George R.; Ryan, Joseph N.; Hsu-Kim, Heileen

    2011-01-01

    Nanoparticulate metal sulfides such as ZnS can influence the transport and bioavailability of pollutant metals in anaerobic environments. The aim of this work was to investigate how the composition of dissolved natural organic matter (NOM) influences the stability of zinc sulfide nanoparticles as they nucleate and aggregate in water with dissolved NOM. We compared NOM fractions that were isolated from several surface waters and represented a range of characteristics including molecular weight, type of carbon, and ligand density. Dynamic light scattering was employed to monitor the growth and aggregation of Zn-S-NOM nanoparticles in supersaturated solutions containing dissolved aquatic humic substances. The NOM was observed to reduce particle growth rates, depending on solution variables such as type and concentration of NOM, monovalent electrolyte concentration, and pH. The rates of growth increased with increasing ionic strength, indicating that observed growth rates primarily represented aggregation of charged Zn-S-NOM particles. Furthermore, the observed rates decreased with increasing molecular weight and aromatic content of the NOM fractions, while carboxylate and reduced sulfur content had little effect. Differences between NOM were likely due to properties that increased electrosteric hindrances for aggregation. Overall, results of this study suggest that the composition and source of NOM are key factors that contribute to the stabilization and persistence of zinc sulfide nanoparticles in the aquatic environment.

  14. Terrestrial humic substances in Daliao River and its estuary: optical signatures and photoreactivity to UVA light.

    PubMed

    Chen, Hao; Lei, Kun; Wang, Xuechun

    2016-04-01

    Fluorescent dissolved organic matter (FDOM) components were identified by Parallel Factor Analysis (PARAFAC) in surface water of Daliao River and its estuary with a focus on terrestrial humic substance-(HS)-like FDOM identified under two contrasting hydrological conditions. The hydrological conditions did not have noticeable effect on the spectral features of the terrestrial HS-like FDOM, but did affect the components' intensities and photoreactivity: (1) the intensities of terrestrial HS-like components were higher in the normal flow period than in the high flow period, and (2) a spectrally similar terrestrial HS-like FDOM identified under the two contrasting hydrological conditions showed distinct photoreactivity to the same dose of UVA illumination. The findings indicated that terrestrial HS was generated at lower intensities at the terrestrial sources during the high flow period than during the normal flow period and that the transport of terrestrial HS material through the river-estuary system was affected dominantly by seawater dilution along the salinity gradient while fine-tuned by solar UVA illumination. This study exemplifies the effect of hydrological conditions on optical signatures of terrestrial HS-like FDOM and their photoreactivity towards UVA illumination, improving our understanding of the dynamics of terrestrial HS material in river-estuary systems in the framework of the currently proposed new conceptual model for terrestrial organic matter. PMID:26627698

  15. Contribution of capillary electrophoresis to an integrated vision of humic substances size and charge characterizations

    SciTech Connect

    D'Orlye, Fanny; Reiller, Pascal E.

    2014-02-15

    The physicochemical properties of three different humic substances (HS) are probed using capillary zone electrophoresis in alkaline carbonate buffers, pH 10. Special attention is drawn to the impact of the electrolyte ionic strength and counter-ion nature, chosen within the alkali-metal series, on HS electrophoretic mobility. Taylor-Aris dispersion analysis provides insights into the hydrodynamic radius (R-H) distributions of HS. The smallest characterized entities are of nano-metric dimensions, showing neither ionic strength- nor alkali-metal-induced aggregation. These results are compared with the entities evidenced in dynamic light scattering measurements, the size of which is two order of magnitude higher, ca. 100 nm. The extended Onsager model provides a reasonable description of measured electrophoretic mobilities in the ionic strength range 1-50 mM, thus allowing the estimation of limiting mobilities and ionic charge numbers for the different HS samples. An unexpected HS electrophoretic mobility increase (in absolute value) is observed in the order Li{sup +} ≤ Na{sup +} ≤ K{sup +} ≤ Cs{sup +} and discussed either in terms of retarding forces or in terms of ion-ion interactions. (authors)

  16. Enhanced photoproduction of hydrogen peroxide by humic substances in the presence of phenol electron donors.

    PubMed

    Zhang, Yi; Simon, Kelli A; Andrew, Andrea A; Del Vecchio, Rossana; Blough, Neil V

    2014-11-01

    Addition of a series of phenol electron donors to solutions of humic substances (HS) enhanced substantially the initial rates of hydrogen peroxide (H2O2) photoproduction (RH2O2), with enhancement factors (EF) ranging from a low of ∼3 for 2,4,6-trimethylphenol (TMP) to a high of ∼15 for 3,4-dimethoxyphenol (DMOP). The substantial inhibition of the enhanced RH2O2 following borohydride reduction of the HS, as well as the dependence of RH2O2 on phenol and dioxygen concentrations are consistent with a mechanism in which the phenols react with the triplet excited states of (aromatic) ketones within the HS to form initially a phenoxy and ketyl radical. The ketyl radical then reacts rapidly with dioxygen to regenerate the ketone and form superoxide (O2-), which subsequently dismutates to H2O2. However, as was previously noted for the photosensitized loss of TMP, the incomplete inhibition of the enhanced RH2O2 following borohydride reduction suggests that there may remain another pool of oxidizing triplets. The results demonstrate that H2O2 can be generated through an additional pathway in the presence of sufficiently high concentrations of appropriate electron donors through reaction with the excited triplet states of aromatic ketones and possibly of other species such as quinones. However, in some cases, the much lower ratio of H2O2 produced to phenol consumed suggests that secondary reactions could alter this ratio significantly. PMID:25288017

  17. AQUATIC HUMIC SUBSTANCES AS SOURCES AND SINKS OF PHOTOCHEMICALLY PRODUCED TRANSIENT REACTIONS

    EPA Science Inventory

    In sunlit surface waters, aquatic humics and nitrate act as sensitizers or precursors for the production of photoreactants such as singlet oxygen, humic-derived peroxy radicals, hydrogen peroxide, and solvated electrons. ifetimes of the various reactants are controlled by their r...

  18. AQUATIC HUMIC SUBSTANCES AS SOURCES AND SINKS OF PHOTOCHEMICALLY PRODUCED TRANSIENT REACTANTS

    EPA Science Inventory

    In sunlit surface waters, aquatic humics and nitrate act as sensitzers or precursors for the production of photoreactants such as singlet oxygen, humic-derived peroxy radicals, hydrogen peroxide, and solvated electrons. ifetimes of the various reactants are controlled by their re...

  19. Estimation of Uptake of Humic Substances from Different Sources by Escherichia coli Cells under Optimum and Salt Stress Conditions by Use of Tritium-Labeled Humic Materials▿

    PubMed Central

    Kulikova, Natalia A.; Perminova, Irina V.; Badun, Gennady A.; Chernysheva, Maria G.; Koroleva, Olga V.; Tsvetkova, Eugenia A.

    2010-01-01

    The primary goal of this paper is to demonstrate potential strengths of the use of tritium-labeled humic substances (HS) to quantify their interaction with living cells under various conditions. A novel approach was taken to study the interaction between a model microorganism and the labeled humic material. The bacterium Escherichia coli was used as a model microorganism. Salt stress was used to study interactions of HS with living cells under nonoptimum conditions. Six tritium-labeled samples of HS originating from coal, peat, and soil were examined. To quantify their interaction with E. coli cells, bioconcentration factors (BCF) were calculated and the amount of HS that penetrated into the cell interior was determined, and the liquid scintillation counting technique was used as well. The BCF values under optimum conditions varied from 0.9 to 13.1 liters kg−1 of cell biomass, whereas under salt stress conditions the range of corresponding values increased substantially and accounted for 0.2 to 130 liters kg−1. The measured amounts of HS that penetrated into the cells were 23 to 167 mg and 25 to 465 mg HS per kg of cell biomass under optimum and salt stress conditions, respectively. This finding indicated increased penetration of HS into E. coli cells under salt stress. PMID:20639375

  20. Influence of mineral colloids and humic substances on uranium(VI) transport in water-saturated geologic porous media.

    PubMed

    Wang, Qing; Cheng, Tao; Wu, Yang

    2014-12-01

    Mineral colloids and humic substances often co-exist in subsurface environment and substantially influence uranium (U) transport. However, the combined effects of mineral colloids and humic substances on U transport are not clear. This study is aimed at quantifying U transport and elucidating geochemical processes that control U transport when both mineral colloids and humic acid (HA) are present. U-spiked solutions/suspensions were injected into water-saturated sand columns, and U and colloid concentrations in column effluent were monitored. We found that HA promoted U transport via (i) formation of aqueous U-HA complexes, and (ii) competition against aqueous U for surface sites on transport media. Illite colloids had no influence on U transport at pH5 in the absence of HA due to low mobility of the colloids. At pH9, U desorbed from mobile illite and the presence of illite decreased U transport. At pH5, high U transport occurred when both illite colloids and HA were present, which was attributed to enhanced U adsorption to illite colloids via formation of ternary illite-HA-U surface complexes, and enhanced illite transport due to HA attachment to illite and transport media. This study demonstrates that the combined effects of mineral colloids and HA on contaminant transport is different from simple addition of the individual effect. PMID:25444118

  1. Electropulse treatment of water solution of humic substances in a layer iron granules in process of water treatment

    NASA Astrophysics Data System (ADS)

    Lobanova, G. L.; Yurmazova, T. A.; Shiyan, L. N.; Machekhina, K. I.

    2016-02-01

    The present work is a part of a continuations study of the physical and chemical processes complex in natural waters containing humic-type organic substances at the influence of pulsed electrical discharges in a layer of iron pellets. The study of humic substances processing in the iron granules layer by means of pulsed electric discharge for the purpose of water purification from organic compounds humic origin from natural water of the northern regions of Russia is relevant for the water treatment technologies. In case of molar humate sodium - iron ions (II) at the ratio 2:3, reduction of solution colour and chemical oxygen demand occur due to the humate sodium ions and iron (II) participation in oxidation-reduction reactions followed by coagulation insoluble compounds formation at a pH of 6.5. In order to achieve this molar ratio and the time of pulsed electric discharge, equal to 10 seconds is experimentally identified. The role of secondary processes that occur after disconnection of the discharge is shown. The time of contact in active erosion products with sodium humate, equal to 1 hour is established. During this time, the value of permanganate oxidation and iron concentration in solution achieves the value of maximum permissible concentrations and further contact time increase does not lead to the controlled parameters change.

  2. Buthionine sulfoximine prevents the reduction of the genotoxic activity of maleic hydrazide by soil humic substances in Vicia faba seedlings.

    PubMed

    De Marco, A; De Simone, C; D'Ambrosio, C; Owczarek, M

    1999-01-13

    A significant reduction of the genotoxic effects caused by herbicide maleic hydrazide (MH) in Vicia faba seedlings was observed to be induced by a growth step in an organic soil as well as by a pretreatment with highly purified humic substances. In addition, such protective activity was resulted quite similar to that observed when the conditioning pretreatment was carried out with metal salts, so suggesting the involvement of the GSH biosynthesis in determining the protective activity observed. In agreement with this hypothesis, a previous exposure to buthionine sulfoximine (BSO), an inhibitor of the phytochelatins production, through the inhibition of GSH synthesis, prevented the reduction of the genotoxic activity of MH. The findings provide evidence for the involvement of the GSH biosynthesis pathway in determining the antigenotoxic activity revealed and suggest a possible involvement of the phytochelatins in this process. However, yet to be clarified is whether the stimulation of GSH production results as a consequence of a nonspecific influence on the protein synthesis by humic substances or of its direct activation due to the presence, as contaminants, of some heavy metals in both organic soil and humic acids extracts. PMID:10036330

  3. Diversity and ubiquity of bacteria capable of utilizing humic substances as electron donors for anaerobic respiration.

    PubMed

    Coates, John D; Cole, Kimberly A; Chakraborty, Romy; O'Connor, Susan M; Achenbach, Laurie A

    2002-05-01

    Previous studies have demonstrated that reduced humic substances (HS) can be reoxidized by anaerobic bacteria such as Geobacter, Geothrix, and Wolinella species with a suitable electron acceptor; however, little is known of the importance of this metabolism in the environment. Recently we investigated this metabolism in a diversity of environments including marine and aquatic sediments, forest soils, and drainage ditch soils. Most-probable-number enumeration studies were performed using 2,6-anthrahydroquinone disulfonate (AHDS), an analog for reduced HS, as the electron donor with nitrate as the electron acceptor. Anaerobic organisms capable of utilizing reduced HS as an electron donor were found in all environments tested and ranged from a low of 2.31 x 10(1) in aquifer sediments to a high of 9.33 x 10(6) in lake sediments. As part of this study we isolated six novel organisms capable of anaerobic AHDS oxidation. All of the isolates coupled the oxidation of AHDS to the reduction of nitrate with acetate (0.1 mM) as the carbon source. In the absence of cells, no AHDS oxidation was apparent, and in the absence of AHDS, no cell density increase was observed. Generally, nitrate was reduced to N(2). Analysis of the AHDS and its oxidized form, 2,6-anthraquinone disulfonate (AQDS), in the medium during growth revealed that the anthraquinone was not being biodegraded as a carbon source and was simply being oxidized as an energy source. Determination of the AHDS oxidized and nitrate reduced accounted for 109% of the theoretical electron transfer. In addition to AHDS, all of these isolates could also couple the oxidation of reduced humic substances to the reduction of nitrate. No HS oxidation occurred in the absence of cells and in the absence of a suitable electron acceptor, demonstrating that these organisms were capable of utilizing natural HS as an energy source and that AHDS serves as a suitable analog for studying this metabolism. Alternative electron donors included

  4. Carbonaceous species and humic like substances (HULIS) in Arctic snowpack during OASIS field campaign in Barrow

    NASA Astrophysics Data System (ADS)

    Voisin, Didier; Jaffrezo, Jean-Luc; Houdier, StéPhan; Barret, Manuel; Cozic, Julie; King, Martin D.; France, James L.; Reay, Holly J.; Grannas, Amanda; Kos, Gregor; Ariya, Parisa A.; Beine, Harry J.; Domine, Florent

    2012-07-01

    Snowpacks contain many carbonaceous species that can potentially impact on snow albedo and arctic atmospheric chemistry. During the OASIS field campaign, in March and April 2009, Elemental Carbon (EC), Water insoluble Organic Carbon (WinOC) and Dissolved Organic Carbon (DOC) were investigated in various types of snow: precipitating snows, remobilized snows, wind slabs and depth hoars. EC was found to represent less than 5% of the Total Carbon Content (TCC = EC + WinOC + DOC), whereas WinOC was found to represent an unusual 28 to 42% of TCC. Snow type was used to infer physical processes influencing the evolution of different fractions of DOC. DOC is highest in soil influenced indurated depth hoar layers due to specific wind related formation mechanisms in the early season. Apart from this specific snow type, DOC is found to decrease from precipitating snow to remobilized snow to regular depth hoar. This decrease is interpreted as due to cleaving photochemistry and physical equilibration of the most volatile fraction of DOC. Depending on the relative proportions of diamond dust and fresh snow in the deposition of the seasonal snowpack, we estimate that 31 to 76% of DOC deposited to the snowpack is reemitted back to the boundary layer. Under the assumption that this reemission is purely photochemical, we estimate an average flux of VOC out of the snowpack of 20 to 170 μgC m-2 h-1. Humic like substances (HULIS), short chain diacids and aldehydes are quantified, and showed to represent altogether a modest (<20%) proportion of DOC, and less than 10% of DOC + WinOC. HULIS optical properties are measured and could be consistent with aged biomass burning or a possible marine source.

  5. Factors influencing inapplicability of cosolvency-induced model on organic acid sorption onto humic substance from methanol mixture.

    PubMed

    Kim, Minhee; Kim, Juhee; Kim, Jeong-Gyu; Hyun, Seunghun

    2015-10-01

    Applicability of cosolvency model for describing the sorption of organic acids to humic substance was investigated by analyzing dataset of sorption (K m) and solubility (S m) of selected solutes (benzoic acid, 1-naphthoic acid, 2,4-dichlorophenoxyacetic acid, and 2,4,6-trichlorophenol (2,4,6-TCP)) as a function of pH(appCME) (apparent pH of liquid phase) and f c (methanol volume fractions). For all solutes, the K m decreased with f c with the K m reduction being less than the S m-based prediction. The slope of log K m-f c plot in the three organic carboxylic acids was well correlated with their cosolvency power, whereas the data of organic phenolic acid (2,4,6-TCP) was placed above the trend, indicating the different actions of functional groups. The occurrence of Ca(2+) bridge between carboxylate and negatively charged humic surface may explain this phenomenon. Normalizing the K m to the corresponding S m (α' = K m/S m) was not in unity over the pH(app)-f c range but decreased with f c, indicating a possible structural modification of sorption domain favoring extra sorption. For a given solute, the α' of neutral species was always greater than that of anionic species, showing that extra interaction will be likely at pH(app) humic substance in methanol/water mixtures. Modification of humic structure and hydrophilic interaction (such as Ca(2+) bridge and same-charge repulsion) is considered a relevant process that possibly restricts the applicability of the cosolvency model. PMID:26028349

  6. Humic substance charge determination by titration with a flexible cationic polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Tan, Wen-Feng; Norde, Willem; Koopal, Luuk K.

    2011-10-01

    The anionic charge of humic substances (HS) plays a major role in the interaction of HS with other components. Therefore, the potential of the polyelectrolyte titration technique to obtain the charge density of HS in simple 1-1 electrolyte solutions has been investigated. Titrations are carried out with an automatic titrator combined with the "Mütek particle charge detector" which allows determination of the Mütek potential and the pH as a function of the added amount of titrant which is a solution of poly-diallyldimethylammonium chloride (polyDADMAC), a cationic strong polyelectrolyte. When the Mütek potential reverses its sign the iso-electric point (IEP) of the polyDADMAC-HS complex is reached. The polyDADMAC/HS mass ratio at the IEP gives information on the HS charge density and from the pH changes in solution an estimate of the charge regulation in the HS-polyDADMAC complex can be obtained. In general, for polyDADMAC-HS complexes an increase in the dissociation of the acid groups of HS is found (charge regulation). The charge regulation decreases with increasing concentration of 1-1 background electrolyte. Cation incorporation can be neglected at 1-1 electrolyte concentrations ⩽ 1 mmol L -1 and a 1-1 stoichiometry exists between the polyDADMAC and HS charge. However, at these low salt concentrations the charge regulation is substantial. A detailed analysis of purified Aldrich humic acid (PAHA) at pH 5 and a range of KCl concentrations reveals that the anionic charge of PAHA in the complex increases at 5 mmol L -1 KCl by 30% and at 150 mmol L -1 KCl by 12%. On the other hand, increasing amounts of K + become incorporated in the complex: at 5 mmol L -1 KCl 5% and at 150 mmol L -1 KCl 24% of the PAHA charge is balanced by K +. By comparing at pH 5 the mass ratios polyDADMAC/PAHA in the complex at the IEP with the theoretical mass ratios of polyDADMAC/PAHA required to neutralize PAHA in the absence of charge regulation and K + incorporation, it is found that

  7. Perspectives of humic substances application in remediation of highly heavy metals contaminated soils in Kola Subarctic

    NASA Astrophysics Data System (ADS)

    Tregubova, Polina; Turbaevskaya, Valeria; Zakharenko, Andrey; Kadulin, Maksim; Smirnova, Irina; Stepanov, Andrey; Koptsik, Galina

    2016-04-01

    Northwestern part of Russia, the Kola Peninsula, is one of the most heavy metals (HM) contaminated areas in the northern hemisphere. The main polluters, mining-and-metallurgical integrated works "Pechenganikel" and "Severonikel", are surrounded by heavily damaged barren lands that require remediation. The main contaminating metals are Ni and Cu. Using of exogenous humic substances could be possible effective and cost-efficient solution of HM contamination problem. Rational application of humates (Na-K salts of humic acids) can result in improvement of soil properties, localization of contamination and decreasing bioavailability through binding HM in relatively immobile organic complexes. Our research aim was to evaluate the influence of increasing doses of different origin humates on i) basic properties of contaminated soils; ii) mobility and bioavailability of HMs; iii) vegetation state and chemistry. In summer 2013 a model field experiment was provided in natural conditions of the Kola Peninsula. We investigated the Al-Fe-humus abrazem, soil type that dominates in technogenic barren lands around the "Severonikel" work. These soils are strongly acid: pHH2O was 3.7-4.1; pHKCl was 3.4-4.0. The exchangeable acidity is low (0.8-1.6 cmol(+)/kg) due to the depletion of fine particles and organic matter, being the carriers of exchange positions. The abrazems of barrens had lost organic horizon. 12 sites were created in 1 km from the work. In those sites, except 2 controls, various amendments were added: i) two different by it's origin types of humates: peat-humates and coal-humates, the last were in concentrations 0.5% and 1%; ii) lime; iii) NPK-fertilizer; iv) biomates (organic degradable cover for saving warm and erosion protection). As a test-culture a grass mixture with predominance of Festuca rubra and Festuca ovina was sowed. As a result we concluded that humates of different origin have unequal influence on soil properties and cause decreasing as well as

  8. Source indicators of humic substances and proto-kerogen - Stable isotope ratios, elemental compositions and electron spin resonance spectra

    NASA Technical Reports Server (NTRS)

    Stuermer, D. H.; Peters, K. E.; Kaplan, I. R.

    1978-01-01

    Stable isotope ratios of C, N and H, elemental compositions, and electron spin resonance (ESR) data of humic acids and proto-kerogens from twelve widely varying sampling locations are presented. Humic acids and proto-kerogens from algal sources are more aliphatic and higher in N than those from higher plant sources. Oxygen content appears to represent a measure of maturation, even in Recent sediments, and S content may reflect redox conditions in the environment of deposition. The ESR data indicate that the transformation of humic substances to proto-kerogens in Recent sediments is accompanied by an increase in aromatic character. A combination of stable carbon isotope ratio and H/C ratio may be a simple but reliable source indicator which allows differentiation of marine-derived from terrestrially-derived organic matter. The stable nitrogen isotope ratios are useful indicators of nitrogen nutrient source. Deuterium/hydrogen isotope ratios appear to reflect variations in meteoric waters and are not reliable source indicators.

  9. Influence of dissolved humic substances on the mass transfer of organic compounds across the air-water interface.

    PubMed

    Ramus, Ksenia; Kopinke, Frank-Dieter; Georgi, Anett

    2012-01-01

    The effect of dissolved humic substances (DHS) on the rate of water-gas exchange of two volatile organic compounds was studied under various conditions of agitation intensity, solution pH and ionic strength. Mass-transfer coefficients were determined from the rate of depletion of model compounds from an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution (dynamic system). Under these conditions, the overall transfer rate is controlled by the mass-transfer resistance on the water side of the water-gas interface. The experimental results show that the presence of DHS hinders the transport of the organic molecules from the water into the gas phase under all investigated conditions. Mass-transfer coefficients were significantly reduced even by low, environmentally relevant concentrations of DHS. The retardation effect increased with increasing DHS concentration. The magnitude of the retardation effect on water-gas exchange was compared for Suwannee River fulvic and humic acids, a commercially available leonardite humic acid and two synthetic surfactants. The observed results are in accordance with the concept of hydrodynamic effects. Surface pressure forces due to surface film formation change the hydrodynamic characteristics of water motion at the water-air interface and thus impede surface renewal. PMID:22051345

  10. Influence of low molecular weight fractions of humic substances on reducing capacities and distribution of redox functional groups

    NASA Astrophysics Data System (ADS)

    Yang, Zhen; Jiang, Jie

    2016-04-01

    Humic substances (HS) are redox-active organic compounds and their reducing capacities depend on their molecule structure and distribution of redox functional groups (RFG). During dialysis experiments, bulk humic acids (HA) were separated into low molecular weight fractions (LMWF) and retentate. LMWF account for only 2% of the total organic carbon content of HA molecules, however, their reducing capacities are up to 33 times greater than either those of the bulk HA or retentate. Furthermore, the total reducing capacity of the bulk HA accounts for less than 15% of the total reducing capacity of bulk HA, retentate and LMWF combined, suggesting that releasing of LMWF cannot reduce the number of RFG. RFG are neither in fixed amounts nor in uniformly distributed in bulk HA. LWMF have great fluorescence intensities for humic-like fluorophores (quinone-like functional groups), where quinonoid π-π* transition is responsible for the great reducing capacities of LMWF, and protein-like fluorophores. The 3,500 Da molecules (1.25 nm diameter) of HS could stimulate transformation of redox-active metals or potential pollutants trapped in soil micropores (< 2 nm diameter). A development of relationship between reducing capacity and Ex/Em position provides a possibility to predicate relative reducing capacities of HS in environmental samples.

  11. Complexation humic substances of soils with metal ions as the main way migration of matals from soil to water

    NASA Astrophysics Data System (ADS)

    Dinu, Marina

    2013-04-01

    Organic matter (OM) of natural waters can bind with the ions metals (IM) entering the system, thus reducing their toxic properties. OM in water consists predominantly (up to 80%) of humic acids (HA), represented by highmolecular, dyed, polyfunctional compounds. The natural-climatic zones feature various ratios of fulvic (FA) and humic acids. An important specific feature of metals as contamination elements is the fact that when they occur in the environment, their potential toxicity and bioavailability depend significantly on their speciation. In recent years, lakes have been continuously enriched in hazardous elements such as Pb, Cd, Al, and Cr on a global (regional) basis. The most important organic ligands are humic matter (HM) washed out from soils in water and metals occur in natural waters as free ions, simple complexes with inorganic and organic ligands, and mineral and organic particles of molecules and ions sorbed on the surface. The occurrence of soluble metal forms in natural waters depends on the presence of organic and inorganic anions. However, direct determinations are rather difficult. The goal was the calculation and analysis of the forms of metals in the system catchment basin, based on the chemical composition of the water body and the structural features of soil humic substances (HS).We used the following analytical techniques - leaching of humic substances from soil and sample preparation (Orlov DS, 1985), the functional characteristics of humic substances - spectral analysis methods, the definition of conditional stability constants of complexes - electrochemical methods of analysis. Our results show thet HAs of selected soil types are different in functions, and these differences effect substantially the complexing process. When analyzing the results obtained in the course of spectrometric investigation of HMs in selected soil types, we determined the following main HA characteristics: (1) predominance of oxygen bearing groups in HM of the

  12. Pb(II) binding to humic substances: an equilibrium and spectroscopic study.

    PubMed

    Orsetti, Silvia; Marco-Brown, Jose L; Andrade, Estela M; Molina, Fernando V

    2013-08-01

    The binding of Pb(II) to humic acids is studied through an approach combining equilibrium and spectroscopic measurements. The methods employed are potentiometric and fluorometric titrations, fluorescence excitation-emission matrices (EEM) and IR spectroscopy. Potentiometric titration curves are analyzed using the NICA equations and an electrostatic model treating the humic particles as an elastic polyelectrolyte network. EEMs are analyzed using parallel factor analysis, decomposing the signal in its independent components and finding their dependence on Pb(II) activity. Potentiometric results are consistent with bimodal affinity distributions for Pb(II) binding, whereas fluorometric titrations are explained by monomodal distributions. EEM analysis is consistent with three independent components in the humic fluorescence response, which are assigned to moieties with different degree of aromaticity. All three components show a similar quenching behavior upon Pb(II) binding, saturating at relatively low Pb(II) concentrations. This is attributed to metal ion induced aggregation of humic molecules, resulting in the interaction between the aromatic groups responsible for fluorescence; this is also consistent with IR spectroscopy results. The observed behavior is interpreted considering that initial metal binding (observed as strongly binding sites), correspond to bi- or multidentate complexation to carboxylate groups, including binding between groups of different humic molecules, promoting aggregation; further metal ions (observed as weakly binding sites) bind to single ligand groups. PMID:23805795

  13. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    SciTech Connect

    Thorn, Kevin A.; Cox, Larry G.

    2009-02-28

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS ¹⁵N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by ¹⁵N NMR. Liquid state ¹⁵N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (¹H–¹⁵N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  14. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    USGS Publications Warehouse

    Thorn, K.A.; Cox, L.G.

    2009-01-01

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS 15N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by 15N NMR. Liquid state 15N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (1H-15N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  15. Contrasting cellular stress responses of Baikalian and Palearctic amphipods upon exposure to humic substances: environmental implications.

    PubMed

    Protopopova, Marina V; Pavlichenko, Vasiliy V; Menzel, Ralph; Putschew, Anke; Luckenbach, Till; Steinberg, Christian E W

    2014-12-01

    The species-rich, endemic amphipod fauna of Lake Baikal does not overlap with the common Palearctic fauna; however, the underlying mechanisms for this are poorly understood. Considering that Palearctic lakes have a higher relative input of natural organic compounds with a dominance of humic substances (HSs) than Lake Baikal, we addressed the question whether HSs are candidate factors that affect the different species compositions in these water bodies. We hypothesized that interspecies differences in stress defense might reveal that Baikalian amphipods are inferior to Palearctic amphipods in dealing with HS-mediated stress. In this study, two key mechanisms of general stress response were examined: heat-shock protein 70 (HSP70) and multixenobiotic resistance-associated transporters (ABCB1). The results of quantitative polymerase chain reaction (qPCR) showed that the basal levels (in 3-day acclimated animals) of hsp70 and abcb1 transcripts were lower in Baikalian species (Eulimnogammarus cyaneus, Eulimnogammarus verrucosus, Eulimnogammarus vittatus-the most typical littoral species) than in the Palearctic amphipod (Gammarus lacustris-the only Palearctic species distributed in the Baikalian region). In the amphipods, the stress response was induced using HSs at 10 mg L(-1) dissolved organic carbon, which was higher than in sampling sites of the studied species, but well within the range (3-10 mg L(-1)) in the surrounding water bodies populated by G. lacustris. The results of qPCR and western blotting (n = 5) showed that HS exposure led to increased hsp70/abcb1 transcripts and HSP70 protein levels in G. lacustris, whereas these transcript levels remained constant or decreased in the Baikalian species. The decreased level of stress transcripts is probably not able to confer an effective tolerance to Baikalian species against further environmental stressors in conditions with elevated HS levels. Thus, our results suggest a greater robustness of Palearctic amphipods and

  16. Fluorescence of sediment humic substance and its effect on the sorption of selected endocrine disruptors.

    PubMed

    Sun, W L; Ni, J R; Xu, N; Sun, L Y

    2007-01-01

    Humic substances (HS) have a critical influence on the sorption of organic contaminants by soils and sediments. This paper describes investigations into the sorption behavior of three representative endocrine disruptors, bisphenol A (BPA), 17beta-estradiol (E2), and 17alpha-ethynylestradiol (EE2), onto sediments and HS extracted sediments using a batch technique. The organic carbon-normalized partition coefficients (K(oc)) for the extracted HS (K(oc)(hs)) were calculated, and the fluorescence spectra of the HS extraced from different sediment samples were gained using excitation/emission matrix (EEM). Particular attention was paid to the correlations between the fluorescence characteristics of HS and the log K(oc)(hs) of selected endocrine disruptors. The results show that the log K(oc)(hs) values range from 3.14 to 4.09 for BPA, from 3.47 to 4.33 for E2, and from 3.65 to 4.32 for EE2. Two characteristic excitation-emission peaks were observed for HS samples extracted from sediments. They are located at Ex/Em=250-260 nm/400-450 nm (peak alpha') and Ex/Em=310-330 nm/390-400 nm (peak alpha) respectively. The alpha' and alpha peak relative intensities I(alpha')/I(alpha) vary from 0.46 to 1.64 for different extracted HS samples. The similarity between fulvic acids (FA) Ex/Em pairs and those observed for HS indicates that FA is the predominant fraction of HS extracted from sediments. Moreover, the log K(oc)(hs) values of BPA, E2, and EE2 have a negative linear correlation to I(alpha')/I(alpha) values. Peak alpha is often attributed to relatively stable and high molecular weight aromatic fulvic-like matter. Therefore, the result presented here reveals that the abundance of aromatic rings in HS molecular structure plays a critical role in the sorption of selected endocrine disruptors. PMID:16979213

  17. Linking fluorescence spectroscopy to diffuse soil source for dissolved humic substances in the Daning River, China.

    PubMed

    Chen, Hao; Zheng, Bing-Hui; Zhang, Lei

    2013-02-01

    Dissolved organic matter collected in Daning River (China) in July 2009 was investigated with parallel factor analysis (PARAFAC) and fluorescence spectroscopy with the aim of identifying the origin of dissolved humic substance (HS) components. Two HS-like fluorescence components (peak M and C) with excitation/emission (ex/em) maxima at 305/406 nm and 360/464 nm showed relatively uniform distribution in the vertical direction for each sampling site but a trend of accumulation down the river, independent of the highly heterogeneous water environment as implicated by water quality parameters (i.e., water temperature, algae density, chlorophyll a, dissolved oxygen, dissolved organic carbon, pH, conductivity and turbidity), while an amino acid/protein-like component (peak T; ex/em = 280/334 nm) was quite variable in its spatial distribution, implying strong influence from point sources (e.g. sewage discharge) and local microbial activities. The fluorescence intensity (F max in Raman units) at these ex/em wavelength pairs fell in the range of 0.031-0.358, 0.051-0.224 and 0.026-0.115 for peak T, M and C, respectively. In addition, the F max values of peak C covaried with M (i.e. C = 0.503 ×M, p < 0.01, R (2) = 0.973). Taken together, these results indicate that peak M and C originated primarily and directly from the same soil sources that were diffusive in the catchment, but peak T was more influenced by local point sources (e.g. wastewater discharge) and in situ microbial activities. This study presents new insights into the currently controversial origin of some HS components (e.g."peak M", as commonly referred to in the literature). This study highlights that natural water samples should be collected at various depths in addition to along a river/stream flow path so as to better evaluate the origin of HS fluorescence components. PMID:25208714

  18. Analytical fractionation of aquatic humic substances and their metal species by means of multistage ultrafiltration.

    PubMed

    Aster, B; Burba, P; Broekaert, J A

    1996-03-01

    The molecular-size fractionation of aquatic humic substances (HS) and their metal species by means of a novel sequential-stage ultrafiltration (UF) device equipped with five appropriate ultramembranes (1, 5, 10, 50 and 100 kD) is described. First of all, the concentration dynamics of macromolecules, particulary HS, during five-stage UF and its subsequent washing step has been modelled. Based on these results, the fractionation of aquatic HS (from ground and bog water) by means of multistage UF has been optimized for an analytical scale (10 ml sample, 1 mg/ml HS, 10 ml washing solution, pH 6.0). The molecular size-distribution of selected aquatic HS (BOC 1/2 from the "DFG-Versuchsfeld Bocholt", VM 5 from "Venner Moor", Germany) studied by five-stage UF exhibited strong systematic influences of the procedure used for their isolation. The molecular-size distribution of HS obtained by on-line UF and gel permeation chromatography (GPC) showed a satisfactory agreement in the range 1-50 kD. Moreover, when interrupting multistage UF for > 48 h a slow transformation in the HS samples has been found as gradually additional HS fractions of < 1 kD have been formed. Besides unloaded HS molecules, the molecular-size distribution of freshly formed metal species of HS (1.0 mg metal/g HS of Al(III), Cd(II), Cu(II), Fe(III), Mn(II), Ni(II), Pb(II), Zn(II), each) has been characterized by multistage UF as a function of pH-value, degree of loading and complexation time. Metal determinations as carried out by flame AAS, showed that considerable metal fractions in HS especially are present in molecules > 50 kD, which seemed to be rather acid-inert. With complexation times of < 2 days a transient shift of the molecular size distribution of both HS and their metal species (e.g., Al(III), Fe(III) to higher values (> 10 kD) has been found. PMID:15067480

  19. Conductometric measurement of the changes in humic substances caused by ozone oxidation.

    PubMed

    Martín-Domínguez, Alejandra; Lara-Sánchez, Abigail; Hansen-Hansen, Anne M; Alarcón-Herrera, M Teresa

    2016-06-01

    Humic substances (HS), a broad category of organic compounds and a major constituent of soil, are responsible for serious problems during water purification processes. In particular, HS react with chlorine during disinfection processes to produce a variety of organochlorine compounds such as trihalomethanes (THMs), which are potentially carcinogenic to humans. The use of ozone as a disinfection method represents a potential solution to this problem; however, HS that are not completely oxidized may form by-products more reactive than the original molecules. The structural changes of HS during oxidation with ozone were evaluated through a replicated 2(2) design, where concentrations of 5 and 30 mg/L of two commercial HS (Aldrich and Fluka) were ozonized over different time intervals (0, 10, and 20 min). The ozone-treated HS were titrated with acid and base solutions, and the shifts of the slopes were then analyzed and finally related to the ionic alterations of the HS. The Aldrich HS (AHS) showed only protonated functional groups; the Fluka HS (FHS) showed only ionized groups; and in both cases, the amount of functional groups increased with increasing ozonation. For AHS and FHA, respectively, the maximum ozone exposure time (20 min) and the highest concentration of HS (30 mg/L) produced the greatest reductions in total organic carbon (TOC) (39 and 34 %), UV254 (50 and 60.8 %), and color (16.4 and 19.6 %). As for aromaticity, AHS showed removals of 39.6 % (from a starting concentration of 5 mg/L) and 17.2 % (from a starting concentration of 30 mg/L). FHS showed the opposite effect, with removals of 33.3 % (starting at 5 mg/L) and 40.1 % (starting at 30 mg/L). In this study, the structural changes of HS submitted to ozonation were inferred in a relatively quick and easy way by using a conductometric titration, thus demonstrating the applicability of the technique. PMID:26965279

  20. Dependence of microbial magnetite formation on humic substance and ferrihydrite concentrations

    NASA Astrophysics Data System (ADS)

    Piepenbrock, Annette; Dippon, Urs; Porsch, Katharina; Appel, Erwin; Kappler, Andreas

    2011-11-01

    Iron mineral (trans)formation during microbial Fe(III) reduction is of environmental relevance as it can influence the fate of pollutants such as toxic metal ions or hydrocarbons. Magnetite is an important biomineralization product of microbial iron reduction and influences soil magnetic properties that are used for paleoclimate reconstruction and were suggested to assist in the localization of organic and inorganic pollutants. However, it is not well understood how different concentrations of Fe(III) minerals and humic substances (HS) affect magnetite formation during microbial Fe(III) reduction. We therefore used wet-chemical extractions, magnetic susceptibility measurements and X-ray diffraction analyses to determine systematically how (i) different initial ferrihydrite (FH) concentrations and (ii) different concentrations of HS (i.e. the presence of either only adsorbed HS or adsorbed and dissolved HS) affect magnetite formation during FH reduction by Shewanella oneidensis MR-1. In our experiments magnetite formation did not occur at FH concentrations lower than 5 mM, even though rapid iron reduction took place. At higher FH concentrations a minimum fraction of Fe(II) of 25-30% of the total iron present was necessary to initiate magnetite formation. The Fe(II) fraction at which magnetite formation started decreased with increasing FH concentration, which might be due to aggregation of the FH particles reducing the FH surface area at higher FH concentrations. HS concentrations of 215-393 mg HS/g FH slowed down (at partial FH surface coverage with sorbed HS) or even completely inhibited (at complete FH surface coverage with sorbed HS) magnetite formation due to blocking of surface sites by adsorbed HS. These results indicate the requirement of Fe(II) adsorption to, and subsequent interaction with, the FH surface for the transformation of FH into magnetite. Additionally, we found that the microbially formed magnetite was further reduced by strain MR-1 leading to

  1. Role of humic substances in the degradation pathways and residual antibacterial activity during the photodecomposition of the antibiotic ciprofloxacin in water.

    PubMed

    Porras, Jazmín; Bedoya, Cristina; Silva-Agredo, Javier; Santamaría, Alexander; Fernández, Jhon J; Torres-Palma, Ricardo A

    2016-05-01

    This study focuses on the photo-transformation, in presence of humic substances (HSs), of ciprofloxacin (CIP), a commonly-used fluoroquinolone antibiotic whose presence in aquatic ecosystems is a health hazard for humans and other living organisms. HSs from the International Humic Substances Society (Elliott humic acid and fulvic acid, Pahokee peat humic acid and Nordic lake) and a humic acid extracted from modified coal (HACM) were tested for their ability to photodegrade CIP. Based on kinetic and analytical studies, it was possible to establish an accelerating effect on the rate of CIP decomposition caused by the humic substances. This effect was associated with the photosensitized capacity of the HSs to facilitate energy transfer from an excited humic state to the ground state of ciprofloxacin. Except for Nordic lake, which experienced a lower positive effect, no significant differences in the CIP transformation were found among the different humic acids examined. The photochemistry of CIP can be modified by parameters such as pH, CIP or oxygen concentration. The irradiation of this antibiotic in the presence of HACM showed that antimicrobial activity was negligible after 14 h for E. coli and 24 h for S. aureus. In contrast, the antimicrobial activity was only slightly decreased after 24 h of irradiation by direct photolysis. Although mineralization of CIP irradiation in the presence of a HACM solution was not achieved, biodegradability was achieved after 12 h of irradiation, indicating that microorganisms within the environment can easily degrade CIP photochemical by-products. PMID:26921708

  2. Influence of humic substances on the formation of chlorinated polycyclic aromatic hydrocarbons during chlorination of polycyclic aromatic hydrocarbon polluted water

    SciTech Connect

    Johnsen, S.; Gribbestad, I.S.

    1988-08-01

    Chlorinated polycyclic aromatic hydrocarbons (PAH) are present at nanogram per liter levels in lake water. Some of these compounds are known to be mutagenic in the Ames Salmonella test. The PAH compounds fluorene, anthracene, fluoranthene, and benzo(a)pyrene were dissolved in lake water with low humus content and in humus water with 9.17 mg of total organic carbon/L, followed by sodium hypochlorite chlorination at different concentrations. Reaction of PAH and formation of chlorinated PAH were measured by cyclohexane extraction of the samples 3 days after chlorination and gas chromatography/mass spectrometry analyses of the extracts. The PAH-chlorine reaction was found to be dependent upon the concentration of free active chlorine in the water, and the presence of humic substances was found to affect the formation of chlorinated PAH. Chlorinated PAH were formed in the lake water samples of fluoranthene and benzo(a)pyrene, but no chlorinated PAH were detected in the presence of humic substances.

  3. Separation of photosensitive substances in humic acids using molecular imprinting method based on electrostatic interactions and hydrogen bond

    NASA Astrophysics Data System (ADS)

    Ou, Xiaoxia; Yu, Chunyan; Wang, Chong; Zhang, Fengjie

    2013-03-01

    The goal of this research was to provide an improved understanding of the existence of photosensitive structure in humic acids (HAs) that are extracted from Changbai Mountain soils. Molecular imprinting technique was used to separate phthalocyanine-like substances from HAs with the mechanisms of electrostatic interactions and intermolecular hydrogen bond. Copper phthalocyanine (CuPc) was used as template molecule and the fraction bound by CuPc-imprinted polymers (MIP) named F (bind) presented higher spectroscopic activity than that of effluent fraction named F (eff). The fluorescence intensity of F(bind) at emission wavelength of 462 nm was 5.5 times as high as that of F(eff) at 458 nm, and the UV-vis absorbance at 254 nm of F(bind) had been increased to 2.5 times as compared with F(eff). The results of this work show the key role of humic substances with special structures in the light or photo involved process.

  4. Solid state NMR spectroscopy in the evaluation of the conformational changes of humic substances as affected by thermal variations

    NASA Astrophysics Data System (ADS)

    de Pasquale, C.; Berns, A. E.; Kucerik, J.; Conte, P.; Alonzo, G.

    2009-04-01

    Soil organic matter (SOM) is an ubiquitous, complex material which is produced by the degradation of plant tissues and animal bodies. It is the major indicator of soil quality since it is directly involved in the maintenance of soil fertility, prevention of erosion and desert encroachment and provision of suitable environment for biological activity. Organic matter is an important driving force in environmental global change as it acts as both a source and sink of atmospheric carbon. However, SOM is subjected to rapid changes due to environmental transformations such as massive deforestations, fires, intensive land uses, temperature increases and so on. In the present work, a characterization of humic substances was done in order to obtain information about the transformation occurring to SOM as affected by temperature increases. For the first time variable temperature cross polarization magic angle spinning (CPMAS) 13C NMR spectroscopy was applied in combination with thermal analyses (TG and DSC) on environmentally relevant soil organic matter. The results show that the conformational changes occurring in humic substances as temperature is raised can be associated to melting of alkyl components connected with sublimation of some organic compounds. The simultaneous application of solid phase micro extraction GC-MS also allowed the identification of the components which were released by sublimation processes.

  5. Measurement of associations of pharmaceuticals with dissolved humic substances using solid phase extraction.

    PubMed

    Ding, Yunjie; Teppen, Brian J; Boyd, Stephen A; Li, Hui

    2013-04-01

    An innovative method was developed to determine association of carbadox, lincomycin and tetracycline with dissolved humic acids using solid phase extraction (SPE). Dissolved organic matter (DOM) and DOM-bound pharmaceuticals passed through the SPE cartridge while the cartridge retained freely dissolved pharmaceuticals from water. This method was validated by comparison with the results measured using the common equilibrium dialysis technique. For the SPE method pharmaceutical interaction with DOM required ∼30h to approach the equilibration, whereas 50-120h was needed for the equilibrium dialysis technique. The uneven distributions of freely membrane-penetrating pharmaceuticals and protons inside vs. outside of the dialysis cell due to the Donnan effect resulted in overestimates of pharmaceutical affinity with DOM for the equilibrium dialysis method. The SPE technique eliminates the Donnan effect, and demonstrates itself as a more efficient, less laborious and more accurate method. The measured binding coefficients with DOM followed the order of carbadoxhumic acid were greater than those with Aldrich humic acid due to more interaction sites, i.e. carboxylic and phenolic functional moieties, present in the Leonardite humic acid. The results obtained suggest that many pharmaceuticals could be significantly bound to DOM, which alters their fate and mobility in the environment. PMID:23260244

  6. REMOVAL OF TASTE- AND ODOR-CAUSING COMPOUNDS BY BIOFILMS GROWN ON HUMIC SUBSTANCES

    EPA Science Inventory

    Laboratory experiments showed that biodegradation of taste- and odor-causing compounds by biofilms grown on natural humic materials is feasible. Although the mineralization of peat fulvic acid (PFA) was relatively low (about 10 percent), long-term application of the PFA resulted ...

  7. Characterization of humic substances isolated from clay- and silt-sized fractions of a corn residue-amended agricultural soil

    SciTech Connect

    Clapp, C.E.; Hayes, M.H.B.

    1999-12-01

    In a small-plot field study on a Waukegan silt loam soil, annual applications of 20 g N m{sup {minus}2} were made each May for 8 years before planting corn (Zea mays L.). Subplots were fertilized with 0.8 g {sup 15}N m{sup {minus}2}. Soil treatment in the fall either incorporated the chopped corn stover after grain harvest, using a rototiller, or the stover was removed from the plots. Soil samples taken in the fall were ultrasonicated, separated into clay- and silt-sized fractions, and extracted exhaustively with 0.1 mol L{sup {minus}1} sodium pyrophosphate (Na{sub 4}P{sub 2}O{sub 7}) + 0.1 mol L{sup {minus}1} NaOH (pH 12.6). Humic (HA) and fulvic (FA) acids were isolated using the International Humic Substances Society (IHSS) procedures. A variety of analytical methods were employed. The most useful information was obtained from amino acid (AA) and neutral sugar (NS) analyses, and from cross polarization magic angle spinning (CPMAS) {sup 13}C-NMR and {delta}{sup 13}C data. Overall, the corn residue amendments did not have a large effect on the composition of the humic substances (HS) from the different sized separates, but there were differences in the relative abundance of some AA and NS in the HAs and FAs. The NMR and {delta}{sup 13}C data provided evidence of some compositional differences and extent of humification between the HS from the clay- and silt-sized separates. The conclusion reached is, therefore, that the silt-sized particles were microaggregates of clay-sized particles, and the HS in these microaggregates were partially protected from bioalteration. These HS bore greater resemblance to the plants of origin than did those associated with the clays. The composition of the HAs and that of the FAs were similar to that of the Mollisol soil standard of the IHSS, but they were different from humic samples from other non-Mollisol soil types.

  8. Spectroscopic study (DRIFT, SERS and 1H NMR) of peat, leonardite and lignite humic substances

    NASA Astrophysics Data System (ADS)

    Francioso, O.; Sànchez-Cortés, S.; Tugnoli, V.; Marzadori, C.; Ciavatta, C.

    2001-05-01

    Diffuse reflectance infrared Fourier transform, surface-enhanced Raman and proton nuclear magnetic resonance spectroscopies were applied to investigate the structure of humic acids (HA) extracted from peat (P-HA), leonardite (Le-HA) and lignite (Li-HA) samples. The combined use of these techniques has shown a specific pattern of functional groups for each sample. P-HA was characterised by a greater content of oxygenate (COOH, C-OH in carbohydrates and phenols) and aliphatic groups. Le-HA and Li-HA showed a lower content of sugar-like components and polyethers. On the other hand, the aromatic structures were ubiquitous in all samples, although the different composition in Le-HA and Li-HA could be employed to identify and distinguish the HA in these two kinds of humic materials.

  9. Addition of a Worm Leachate as Source of Humic Substances in the Drinking Water of Broiler Chickens

    PubMed Central

    Gomez-Rosales, S.; de L. Angeles, M.

    2015-01-01

    The objective of this research was to evaluate the growth performance, the apparent ileal digestibility of nitrogen and energy, the retention of nutrients and the apparent metabolizable energy corrected to zero nitrogen retention (AMEn) in broiler chickens supplemented with increasing doses of a worm leachate (WL) as a source of humic substances (HS) in the drinking water. In Exp. 1, 140 male broilers were penned individually and assigned to four WL levels (0%, 10%, 20%, and 30%) mixed in the drinking water from 21 to 49 days of age. Water was offered in plastic bottles tied to the cage. In Exp. 2, 600 male broilers from 21 to 49 days of age housed in floor pens were assigned to three levels of WL (0%, 10%, and 20%) mixed in the drinking water. The WL was mixed with tap water in plastic containers connected by plastic tubing to bell drinkers. The results of both experiments were subjected to analysis of variance and polynomial contrasts. In Exp. 1, the daily water consumption was similar among treatments but the consumption of humic, fulvic, and total humic acids increased linearly (p<0.01) as the WL increased in the drinking water. The feed conversion (p<0.01) and the ileal digestibility of energy, the excretion of dry matter and energy, the retention of dry matter, ash and nitrogen and the AMEn showed quadratic responses (p<0.05) relative to the WL levels in drinking water. In Exp. 2, the increasing level of WL in the drinking water had quadratic effects on the final body weight, daily weight gain and feed conversion ratio (p<0.05). The addition of WL as a source of HS in the drinking water had beneficial effects on the growth performance, ileal digestibility of energy, the retention of nutrients as well on the AMEn in broiler chickens; the best results were observed when the WL was mixed at levels of 20% to 30% in the drinking water. PMID:25557817

  10. Stability and mobility of cerium oxide nanoparticles in soils: effects of humic substances, pH and ionic strength

    NASA Astrophysics Data System (ADS)

    Chen, Yirui; Mu, Linlin; Li, Chunyan; Bai, Lingyun; Jacobson, Astrid; Darnault, Christophe

    2015-04-01

    Among the large number of types of nanomaterials used in the field of nanotechnology, cerium oxide nanoparticles (CeO2 NPs) are among the top five most commonly utilized by industry, agriculture and nanomedicine for their unique physico-chemical properties. They are used, for example, in the production of catalysts, as fuel additives, and as polishing agents. Therefore, the release and encounter of CeO2 NPs in the environment following their application, waste disposal, life-cycle and accidents is inevitable. It is critical to examine the behavior of CeO2 NPs released in the environment to assess the risk they pose to the environmental and public health. In particular, little is known about the fate and transport of CeO2 NPs in soils and groundwater. To assess the behavior of CeO2 NPs, it is important to investigate the factors that affect their stability and mobility. Humic substances are a major component of soils and have been shown to have the potential to impact the transport and retention of nanoparticles in soils. Consequently, our study characterizes the impacts of humic and fulvic acids on the stability and mobility of cerium oxides in model porous media under various pH and ionic strength conditions. Batch experiments conducted at various concentrations of humic and fulvic acids coupled with a wide range of pHs and ionic strengths were investigated. Selected parameters from these batch studies were then used as experimental conditions representative of environmental systems to perform column transport experiments to assess of the mobility of CeO2 NPs in saturated porous media, which is the first step in simulating their behavior in soil and groundwater systems.

  11. Influence of humic substances on Co[sup 2+] sorption by a subsurface mineral separate and its mineralogic components

    SciTech Connect

    Zachara, J.M.; Resch, C.T.; Smith, S.C. )

    1994-01-01

    The sorption of Co[sup 2+] (10[sup [minus]6] mol/L) was measured on subsurface mineral materials in the absence and presence of a sorbed leonardite humic acid (LHA) to (1) evaluate the sorptive role of mineral-bound humic substances, and (2) establish approaches to model metal ion binding in composite materials. The subsurface materials were a <2.0 [mu]m size fraction of an ultisol saprolite (CP) and this same material treated with dithonite-citrate-bicarbonate (DCB) to remove Fe-oxides (DCP). Comparable experiments (with and without LHA) were also performed with mineral sorbents representing dominant phases in the CP separate (gibbsite, Al-geothite, and kalonite) to evaluate their potential contributions to Co sorption. The mineral-bound LHA ranged in concentration between 0.1-0.4 mg-C/m[sup 2], representing approximately 0.7% of the subsurface isolate by mass. In solid-free suspensions, the affinity of LHA for Co increased with pH and decreasing I (K[sub d] ranging 20-450 L/g). Mineral-bound LHA increased Co sorption on all the sorbents by factors of 10-60%, with the greatest augmentation noted at pH values (4.5-6.5) where (1) maximum LHA sorption occurred, and (2) Co sorption to the mineral phase was weak and dominated by ion exchange. The LHA appeared simply to augment, rather than to change the intrinsic adsorption behavior of the mineral sorbents. Accordingly, predictions of the K[sub d] for Co on the LHA-coated subsurface materials (DCP, CP) based on a linear additivity model agreed well with the experimental data, suggesting that the complex humic-mineral association acted as a noninterative sorbent mixture at low aqueous Co concentrations.

  12. Competitive effect of iron(III) on metal complexation by humic substances: characterisation of ageing processes.

    PubMed

    Lippold, H; Evans, N D M; Warwick, P; Kupsch, H

    2007-03-01

    Aiming at an assessment of counteractive effects on colloid-borne migration of actinides in the event of release from an underground repository, competition by Fe(III) in respect of metal complexation by dissolved organic matter was investigated for the example of Eu(III) as an analogue of trivalent actinides. Complexation with different humic materials was examined in cation exchange experiments, using (59)Fe and (152)Eu as radioactive tracers for measurements in dilute systems as encountered in nature. Competitive effects proved to be significant when Fe is present at micromolar concentrations. Flocculation as a limiting process was attributed to charge compensation of humic colloids. Fe fractions bound to humic acids (HA) were higher than 90%, exceeding the capacity of binding sites at high Fe concentrations. It is thus concluded that the polynuclear structure of hydrolysed Fe(III) is maintained when bound to HA, which is also inferred from UV-Vis spectrometry. The competitive effect was found to be enhanced if Fe and HA were in contact before Eu was added. Depending on the time of Fe/HA pre-equilibration, Eu complexation decreased asymptotically over a time period of several weeks, the amount of bound Fe being unchanged. Time-dependent observations of UV-Vis spectra and pH values revealed that the ageing effect was due to a decline in Fe hydrolysis rather than structural changes within HA molecules. Fe polycations are slowly degraded in contact with humic colloids, and more binding sites are occupied as a consequence of dispersion. The extent of degradation as derived from pH shifts depended on the Fe/HA ratio. PMID:17140629

  13. Characterization of typical aquatic humic substances in areas of sugarcane cultivation in Brazil using tetramethylammonium hydroxide thermochemolysis.

    PubMed

    Tadini, A M; Constantino, I C; Nuzzo, A; Spaccini, R; Piccolo, A; Moreira, A B; Bisinoti, M C

    2015-06-15

    Aquatic humic substances (AHSs) differ from one environment to another depending on land use and occupation. In addition, the effects of planting sugarcane on AHSs are not well known. Thus, the aim of this study was to characterize AHSs extracted from a river in a typical region of sugarcane cultivation during dry and rainy seasons. The main characteristics of the AHSs were obtained using Fourier transformation infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and off-line pyrolysis coupled with gas chromatography and mass spectrometry (off-line tetramethylammonium hydroxide (TMAH)-GC-MS-thermochemolysis). The FTIR and NMR results were used to infer that no distinctions occurred between the sampling periods. The samples were composed of aromatic groups that were potentially associated with the presence of residual vegetable materials (lignin). The results of the off-line TMAH-GC-MS-thermochemolysis indicated that the structures of the AHSs had uniform compositions that were rich in fatty acid methyl esters (FAMEs), polysaccharide derivatives, aliphatic biopolymers derived from plants, long hydrocarbon chains, branched alkyl groups and methylene carbons. Thus, the results showed that the AHSs obtained from the sugarcane cultivation area during the crop period mainly consisted of resistant aliphatic hydrocarbons, which are derivatives of lignin and FAMEs in compounds rich in humic acid. Therefore, we concluded that sugarcane cultivation produces changes in AHSs because greater amounts of lignin derivatives were observed during the dry season, corresponding to sugarcane cultivation. PMID:25756675

  14. Application of a constrained regularization method to extraction of affinity distributions: proton and metal binding to humic substances.

    PubMed

    Orsetti, Silvia; Andrade, Estela María; Molina, Fernando V

    2009-08-15

    The binding of proton and metal cations to humic substances has been analyzed with a regularized fitting procedure (using the CONTIN software package) to extract conditional affinity distributions, valid at a given ionic strength, from binding (titration) curves. The procedure was previously tested with simulated titration curves using a simple bi-Gaussian model, the NICA-Donnan model, and the Stockholm humic model. Application to literature data for proton binding shows that in several cases the affinity distribution found is bimodal (carboxylic and phenolic sites) as usually assumed; however in other cases, specially for fulvic acids, a trimodal distribution is clearly discerned, with a smaller peak between the two noted above attributed to the presence of vicinal carboxylic groups. The analysis of metal binding curves has been performed in a few cases where the available data could be reliably processed, separating the proton affinity distribution and obtaining the conditional affinity spectra. For Cd(II) and Pb(II) a bimodal distribution is found, attributed in principle to mono- and bidentate binding, based on spectroscopic data. In the case of Cu(II), a more complex affinity distribution is found showing 3-4 peaks; this is consistent with spectroscopic studies, where different binding modes, up to tetradentate, have been observed. PMID:19477457

  15. Effects of humic substances derived from organic waste enhancement on the growth and mineral nutrition of maize.

    PubMed

    Eyheraguibel, B; Silvestre, J; Morard, P

    2008-07-01

    A physico-chemical process has been developed to transform and enhance lignocellulosic waste in liquid humic extracts: humic-like substances (HLS). The aim of this study was to determine the effects of HLS on plant physiology in order to consider their agricultural use as organic fertilizers. The effects of HLS were evaluated on maize seed germination, and their impact on growth, development and mineral nutrition was studied on maize plants cultivated under hydroponic conditions. The experimental results showed that HLS do not increase the percentage and rate of germination but enhance the root elongation of seeds thus treated. Positive effects were also observed on the whole plant growth as well as on root, shoot and leaf biomass. These effects can be related to the high water and mineral consumption of plants undergoing this treatment. The high water efficiency indicated that such plants produce more biomass than non-treated plants for the same consumption of the nutrient solution. Furthermore, the use of HLS induced a flowering precocity and modified root development suggesting a possible interaction of HLS with developmental processes. Considering the beneficial effect of HLS on different stages of plant growth, their use may present various scientific and economic advantages. The physico-chemical transformation of sawdust is an interesting way of enhancing organic waste materials. PMID:17962015

  16. The Nematode Caenorhabditis elegans, Stress and Aging: Identifying the Complex Interplay of Genetic Pathways Following the Treatment with Humic Substances

    PubMed Central

    Menzel, Ralph; Menzel, Stefanie; Swain, Suresh C.; Pietsch, Kerstin; Tiedt, Sophie; Witczak, Jördis; Stürzenbaum, Stephen R.; Steinberg, Christian E. W.

    2012-01-01

    Low concentrations of the dissolved leonardite humic acid HuminFeed® (HF) prolonged the lifespan and enhanced the thermal stress resistance of the model organism Caenorhabditis elegans. However, growth was impaired and reproduction delayed, effects which have also been identified in response to other polyphenolic monomers, including Tannic acid, Rosmarinic acid, and Caffeic acid. Moreover, a chemical modification of HF, which increases its phenolic/quinonoid moieties, magnified the biological impact on C. elegans. To gain a deep insight into the molecular basis of these effects, we performed global transcriptomics on young adult (3 days) and old adult (11 days) nematodes exposed to two different concentrations of HF. We also studied several C. elegans mutant strains in respect to HF derived longevity and compared all results with data obtained for the chemically modified HF. The gene expression pattern of young HF-treated nematodes displayed a significant overlap to other conditions known to provoke longevity, including various plant polyphenol monomers. Besides the regulation of parts of the metabolism, transforming growth factor-beta signaling, and Insulin-like signaling, lysosomal activities seem to contribute most to HF’s and modified HF’s lifespan prolonging action. These results support the notion that the phenolic/quinonoid moieties of humic substances are major building blocks that drive the physiological effects observed in C. elegans. PMID:22529848

  17. The Nematode Caenorhabditis elegans, Stress and Aging: Identifying the Complex Interplay of Genetic Pathways Following the Treatment with Humic Substances.

    PubMed

    Menzel, Ralph; Menzel, Stefanie; Swain, Suresh C; Pietsch, Kerstin; Tiedt, Sophie; Witczak, Jördis; Stürzenbaum, Stephen R; Steinberg, Christian E W

    2012-01-01

    Low concentrations of the dissolved leonardite humic acid HuminFeed(®) (HF) prolonged the lifespan and enhanced the thermal stress resistance of the model organism Caenorhabditis elegans. However, growth was impaired and reproduction delayed, effects which have also been identified in response to other polyphenolic monomers, including Tannic acid, Rosmarinic acid, and Caffeic acid. Moreover, a chemical modification of HF, which increases its phenolic/quinonoid moieties, magnified the biological impact on C. elegans. To gain a deep insight into the molecular basis of these effects, we performed global transcriptomics on young adult (3 days) and old adult (11 days) nematodes exposed to two different concentrations of HF. We also studied several C. elegans mutant strains in respect to HF derived longevity and compared all results with data obtained for the chemically modified HF. The gene expression pattern of young HF-treated nematodes displayed a significant overlap to other conditions known to provoke longevity, including various plant polyphenol monomers. Besides the regulation of parts of the metabolism, transforming growth factor-beta signaling, and Insulin-like signaling, lysosomal activities seem to contribute most to HF's and modified HF's lifespan prolonging action. These results support the notion that the phenolic/quinonoid moieties of humic substances are major building blocks that drive the physiological effects observed in C. elegans. PMID:22529848

  18. Influence of Low Molecular Weight Fractions of Humic Substances on Their Reducing Capacities and Distribution of Redox Functional Groups.

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Jiang, J.

    2015-12-01

    Humic substances (HS) are redox-active organic compounds and their reducing capacities depend on molecule structure and distribution of redox functional groups (RFG). During dialysis experiments, initial HS were separated into low molecular weight fractions (LMWF, molecular weight <3,500 Da or <14,000 Da) and retentate. LMWF accounts for only 2% in TOC contents of HS molecules, while their reducing capacities are up to 33 times greater than those of initial HA. However, great amount of reducing capacities of LMWF does not cause decreasing reducing capacities of retentate relative to those of initial HA. Total reducing capacities of whole dialysis device were calculated for initial HA, retentate and LMWF in native and reduced state, and result suggests that releasing of LMWF leads to production and explosion of RFG. LWMF have great fluorescence intensities for protein-like fluorophores and humic acids-like fluorophores (quinone-like functional groups), where quinonoid π-π* transition is responsible for the great reducing capacities of LMWF. The 3,500 Da molecules (0.25 nm diameter) of HS are capable of stimulating transformation of redox-active metals or potential pollutants trapped in soil micropores (< 2 nm diameter). A development of relationship between reducing capacity and Ex / Em position provides a possibility to predicate relative reducing capacities of HS in treated raw water sample.

  19. Complexion between mercury and humic substances from different landfill stabilization processes and its implication for the environment.

    PubMed

    Chai, Xiaoli; Liu, Guixiang; Zhao, Xin; Hao, Yongxia; Zhao, Youcai

    2012-03-30

    Three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy was employed to investigate the structural properties and Hg(II)-binding behavior of humic substances (HS) extracted from different landfill stabilization processes. The EEM fluorescence properties of humic acid (HA) are characterized by intense fluorescence at Ex/Em=440/500 nm and Ex/Em=380/460 nm. Two relatively strong fluorescence peaks appeared in the region of Ex/Em=260-290/350-370 nm with the landfill time extended, which represented a protein-like or soluble microbial byproduct structure. The fluorescence EEM spectrum of fulvic acid (FA) featured a prominent peak of strong relative fluorescence intensity (FI=1598) at Ex/Em=330/440 nm (peak C) accompanied by a weak fluorophore (FI=594) located at Ex/Em=275/445 nm (peak D). There were strong interactions between HA and Hg, and the overall stability constant of Hg(II)-HA was mainly determined by the abundant O-ligands existing in HA. FA had a much higher Hg(II)-complexing capacity compared to HA samples, which may be ascribed to its relatively high content of carboxylic groups. The Hg(II)-complexing capacity of HA tended to decrease with stabilization process extension. The much higher Hg(II)-complexing capacity of FA than that of HA implied that FA played an important role in binding Hg(II) in early landfill stabilization process. PMID:22285919

  20. Immobilized humic substances on an anion exchange resin and their role on the redox biotransformation of contaminants.

    PubMed

    Cervantes, Francisco J; Gonzalez-Estrella, Jorge; Márquez, Arturo; Alvarez, Luis H; Arriaga, Sonia

    2011-01-01

    A novel technique to immobilize humic substances (HS) on an anion exchange resin is presented. Immobilized HS were demonstrated as an effective solid-phase redox mediator (RM) during the reductive biotransformation of carbon tetrachloride (CT) and the azo model compound, Reactive Red 2 (RR2). Immobilized HS increased ∼4-fold the extent of CT reduction to chloroform by a humus-reducing consortium in comparison to incubations lacking HS. Immobilized HS also increased 2-fold the second-order rate constant of decolorization of RR2 as compared with sludge incubations lacking HS. To our knowledge, the present study constitutes the first demonstration of immobilized HS serving as an effective solid-phase RM during the reductive biotransformation of priority contaminants. The immobilizing technique developed could be appropriate for enhancing the redox biotransformation of recalcitrant pollutants in anaerobic wastewater treatment systems. PMID:20801024

  1. Effect of humic substances aggregation on the determination of fluoride in water using an ion selective electrode.

    PubMed

    Shen, Junjie; Gagliardi, Simona; McCoustra, Martin R S; Arrighi, Valeria

    2016-09-01

    The control of drinking water quality is critical in preventing fluorosis. In this study humic substances (HS) are considered as representative of natural organic matter (NOM) in water. We show that when HS aggregate the response of fluoride ion selective electrodes (ISE) may be perturbed. Dynamic light scattering (DLS) results of both synthetic solutions and natural water sample suggest that low pH and high ionic strength induce HS aggregation. In the presence of HS aggregates, fluoride concentration measured by ISE has a reduction up to 19%. A new "open cage" concept has been developed to explain this reversible phenomenon. The interference of HS aggregation on fluoride measurement can be effectively removed by centrifugation pretreatment. PMID:27276164

  2. A mineral support and biotic catalyst are essential in the formation of highly polymeric soil humic substances

    NASA Astrophysics Data System (ADS)

    Zavarzina, A. G.

    2006-12-01

    The hypothesis was proposed that highly polymeric humic substances in the mineral horizons of soils in a temperate humid climate originate from polymerization of water-soluble structural precursors directly on mineral surfaces under the catalytic effect of immobilized phenoloxidases (heterophasic biocatalysis). This hypothesis was confirmed by a laboratory experiment using a mixture of monomeric phenols and nitrogenous compounds as structural precursors, fungal laccase as a biotic catalyst, and a hydroxyaluminum-kaolinite complex as a mineral support. Enzymic oxidation of phenolic precursors on the mineral surface was substantially more rapid than abiotic oxidation and led to synthesis of a highly polymeric fraction with a molecular weight over 75 kDa. These products were not produced on the mineral with an absence of laccase (abiotic catalysis) or in solution without the mineral matrix (homogeneous catalysis).

  3. Interfacial reactions between humic-like substances and lateritic clay: application to the preparation of "geomimetic" materials.

    PubMed

    Goure-Doubi, Herve; Martias, Céline; Lecomte-Nana, Gisèle Laure; Nait-Ali, Benoît; Smith, Agnès; Thune, Elsa; Villandier, Nicolas; Gloaguen, Vincent; Soubrand, Marilyne; Konan, Léon koffi

    2014-11-15

    The aim of this study was to understand the mechanisms responsible for the strengthening of "geomimetic" materials, especially the chemical bonding between clay and humic substances. The mineral matter is lateritic clay which mainly consists in kaolinite, goethite, hematite and quartz. The other starting products are fulvic acid (FA) and lime. The preparation of these geomimetic materials is inspired from the natural stabilization of soils by humic substances occurring over thousands of years. The present process involves acidic and alkaline reactions followed by a curing period of 18days at 60°C under a water saturated atmosphere. The acceleration of the strengthening process usually observed in soils makes this an original process for treatment of soils. The consolidation of the "geomimetic" materials could result from two major phenomena: (i) chemical bonding at the interface between the clay particles and iron compounds and the functional groups of the fulvic acid, (ii) a partial dissolution of the clay grains followed by the precipitation of the cementitious phases, namely calcium silicate hydrates, calcium aluminate hydrates and mixed calcium silicum and aluminum hydrates. Indeed, the decrease of the BET specific area of the lateritic clay after 24 h of reaction with FA added to the structural reorganization observed between 900 and 1000°C in the "geomimetic" material, and to the results of adsorption measurements, confirm the formation of organo-ferric complexes. The presence of iron oxides in clay, in the form of goethite, appears to be another parameter in favor of a ligand exchange process and the creation of binding bridges between FA and the mineral matter. Indeed all faces of goethite are likely to be involved in complexation reactions whereas in lateritic clay only lateral faces could be involved. The results of the adsorption experiments realized at a local scale will improve our understandings about the process of adsorption of FA on lateritic

  4. Characterization of the humic substances isolated from postfire soils of scotch pine forest in Togljatty city, Samara region by the 13C-NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Maksimova, Ekaterina; Abakumov, Evgeny

    2016-04-01

    Postpyrogenic soil dynamics is an informative tool for studying of soil elementary processes in extreme temperature conditions and for predicting of short time environmental changes in conditions of catastrophic landscape changes. Soil organic matter (SOM) system evolution is the most rapid process of postpyrogenic soil development. In this relation the evaluation of humus accumulation rates and humification trend were conducted with use of the classical chemical and modern spectroscopy methods. Soil restoration after spontaneous forest fires near Togljatty city (Samara region, Russia) was abandoned in 2010, and further monitoring over the next four years was organized to evaluate the speed of biogenic processes and humus accumulation dynamics. Three key soil plots were studied for estimating SOM quality changes under the forest fire effect: surface forest fire, crown forest fire and control. Total carbon and nitrogen content as well as Cha/Cfa ratios (content of humic acids/ content of fulvic acids), were estimated to assess the dynamics of soil restoration. Humic acid powders were extracted and analyzed by elemental composition and 13C-NMR spectroscopy to assess changes in humic substance structure and composition. The data obtained indicate that burning of a forest floor and sod (humic) horizon led to humus losses and decreases in total carbon stocks. As a result of the fires, the content of humic acids in the pyrogenic horizon increased, leading alterations of humus type. Greater increases in the degree of organic matter humification were observed for surface fires than crown fires. It was shown that the humus molecular composition was substantially affected by the wildfires. The data show an increase in aromaticity, a loss of oxygen-containing groups and dehydrogenation of humic acids. Humic acids in the soils of the control plots and after wildfires were significantly different, especially in the ratios of hydrogen, oxygen and carbon. The increase in the

  5. Involvement of Hormone- and ROS-Signaling Pathways in the Beneficial Action of Humic Substances on Plants Growing under Normal and Stressing Conditions.

    PubMed

    García, Andrés Calderín; Olaetxea, Maite; Santos, Leandro Azevedo; Mora, Verónica; Baigorri, Roberto; Fuentes, Marta; Zamarreño, Angel Maria; Berbara, Ricardo Luis Louro; Garcia-Mina, José María

    2016-01-01

    The importance of soil humus in soil fertility has been well established many years ago. However, the knowledge about the whole mechanisms by which humic molecules in the rhizosphere improve plant growth remains partial and rather fragmentary. In this review we discuss the relationships between two main signaling pathway families that are affected by humic substances within the plant: one directly related to hormonal action and the other related to reactive oxygen species (ROS). In this sense, our aims are to try the integration of all these events in a more comprehensive model and underline some points in the model that remain unclear and deserve further research. PMID:27366744

  6. Involvement of Hormone- and ROS-Signaling Pathways in the Beneficial Action of Humic Substances on Plants Growing under Normal and Stressing Conditions

    PubMed Central

    García, Andrés Calderín; Olaetxea, Maite; Santos, Leandro Azevedo; Mora, Verónica; Baigorri, Roberto; Fuentes, Marta; Zamarreño, Angel Maria; Berbara, Ricardo Luis Louro; Garcia-Mina, José María

    2016-01-01

    The importance of soil humus in soil fertility has been well established many years ago. However, the knowledge about the whole mechanisms by which humic molecules in the rhizosphere improve plant growth remains partial and rather fragmentary. In this review we discuss the relationships between two main signaling pathway families that are affected by humic substances within the plant: one directly related to hormonal action and the other related to reactive oxygen species (ROS). In this sense, our aims are to try the integration of all these events in a more comprehensive model and underline some points in the model that remain unclear and deserve further research. PMID:27366744

  7. Methylation patterns of aquatic humic substances determined by 13C NMR spectroscopy

    USGS Publications Warehouse

    Thorn, K.A.; Steelink, C.; Wershaw, R. L.

    1987-01-01

    13C NMR spectroscopy is used to examine the hydroxyl group functionality of a series of humic and fulvic acids from different aquatic environments. Samples first are methylated with 13C-labeled diazomethane. The NMR spectra of the diazomethylated samples allow one to distinguish between methyl esters of carboxylic acids, methyl ethers of phenolic hydroxyls, and methyl ethers of phenolic hydroxyls adjacent to two substituents. Samples are then permethylated with 13C-labeled methyl iodide/NaH. 13C NMR spectra of permethylated samples show that a significant fraction of the hydroxyl groups is not methylated with diazomethane alone. In these spectra methyl ethers of carbohydrate and aliphatic hydroxyls overlap with methyl ethers of phenolic hydroxyls. Side reactions of the methyltion procedure including carbon methylation in the CH3I/NaH procedure, are also examined. Humic and fulvic acids from bog, swamp, groundwater, and lake waters showssome differences in their distribution of hydroxyl groups, mainly in the concentrations of phenolic hydroxyls, which may be attributed to their different biogeochemical origins. ?? 1987.

  8. Ammonia fixation by humic substances: A nitrogen-15 and carbon-13 NMR study

    USGS Publications Warehouse

    Thorn, K.A.; Mikita, M.A.

    1992-01-01

    The process of ammonia fixation has been studied in three well characterized and structurally diverse fulvic and humic acid samples. The Suwannee River fulvic acid, and the IHSS peat and leonardite humic acids, were reacted with 15N-labelled ammonium hydroxide, and analyzed by liquid phase 15N NMR spectrometry. Elemental analyses and liquid phase 13C NMR spectra also were recorded on the samples before and after reaction with ammonium hydroxide. The largest increase in percent nitrogen occurred with the Suwannee River fulvic acid, which had a nitrogen content of 0.88% before fixation and 3.17% after fixation. The 15N NMR spectra revealed that ammonia reacted similarly with all three samples, indicating that the functional groups which react with ammonia exist in structural configurations common to all three samples. The majority of nitrogcn incorporated into the samples appears to be in the form of indole and pyrrole nitrogen, followed by pyridine, pyrazine, amide and aminohydroquinone nitrogen. Chemical changes in the individual samples upon fixation could not be discerned from the 13C NMR spectra.

  9. Sources and haloacetic acid/trihalomethane formation potentials of aquatic humic substances in the Wakarusa River and Clinton Lake near Lawrence, Kansas

    USGS Publications Warehouse

    Pomes, M.L.; Larive, C.K.; Thurman, E.M.; Green, W.R.; Orem, W.H.; Rostad, C.E.; Coplen, T.B.; Cutak, B.J.; Dixon, A.M.

    2000-01-01

    Gram quantities of aquatic humic substances (AHS) were extracted from the Wakarusa River-Clinton Lake Reservoir system, near Lawrence, KS, to support nuclear magnetic resonance (NMR) experimental studies, report concentrations of dissolved organic carbon (DOC) and AHS, define sources of the AHS, and determine if the AHS yield sufficient quantities of haloacetic acids (HAA5) and trihalomethanes (THM4) that exceed U.S. Environmental Protection Agency (EPA) Maximum Contaminant Levels (MCL) in drinking water. AHS from the Wakarusa River and Clinton Lake originated from riparian forest vegetation, reflected respective effects of soil organic matter and aquatic algal/bacterial sources, and bore evidence of biological degradation and photodegradation. AHS from the Wakarusa River showed the effect of terrestrial sources, whereas Clinton Lake humicacid also reflected aquatic algal/bacterial sources. Greater amounts of carbon attributable to tannin-derived chemical structures may correspond with higher HAA5 and THM4 yields for Clinton Lake fulvic acid. Prior to appreciable leaf-fall from deciduous trees, the combined (humic and fulvic acid) THM4 formation potentials for the Wakarusa River approached the proposed EPA THM4 Stage I MCL of 80 ??g/L, and the combined THM4 formation potential for Clinton Lake slightly exceeded the proposed THM4 Stage II MCL of 40 ??g/L. Finally, AHS from Clinton Lake could account for most (>70%) of the THM4 concentrations in finished water from the Clinton Lake Water Treatment Plant based on September 23, 1996, THM4 results.Gram quantities of aquatic humic substances (AHS) were extracted from the Wakarusa River-Clinton Lake Reservoir system, near Lawrence, KS, to support nuclear magnetic resonance (NMR) experimental studies, report concentrations of dissolved organic carbon (DOC) and AHS, define sources of the AHS, and determine if the AHS yield sufficient quantities of haloacetic acids (HAA5) and trihalomethanes (THM4) that exceed U

  10. Number of independent parameters in the potentiometric titration of humic substances.

    PubMed

    Lenoir, Thomas; Manceau, Alain

    2010-03-16

    With the advent of high-precision automatic titrators operating in pH stat mode, measuring the mass balance of protons in solid-solution mixtures against the pH of natural and synthetic polyelectrolytes is now routine. However, titration curves of complex molecules typically lack obvious inflection points, which complicates their analysis despite the high-precision measurements. The calculation of site densities and median proton affinity constants (pK) from such data can lead to considerable covariance between fit parameters. Knowing the number of independent parameters that can be freely varied during the least-squares minimization of a model fit to titration data is necessary to improve the model's applicability. This number was calculated for natural organic matter by applying principal component analysis (PCA) to a reference data set of 47 independent titration curves from fulvic and humic acids measured at I = 0.1 M. The complete data set was reconstructed statistically from pH 3.5 to 9.8 with only six parameters, compared to seven or eight generally adjusted with common semi-empirical speciation models for organic matter, and explains correlations that occur with the higher number of parameters. Existing proton-binding models are not necessarily overparametrized, but instead titration data lack the sensitivity needed to quantify the full set of binding properties of humic materials. Model-independent conditional pK values can be obtained directly from the derivative of titration data, and this approach is the most conservative. The apparent proton-binding constants of the 23 fulvic acids (FA) and 24 humic acids (HA) derived from a high-quality polynomial parametrization of the data set are pK(H,COOH)(FA) = 4.18 +/- 0.21, pK(H,Ph-OH)(FA) = 9.29 +/- 0.33, pK(H,COOH)(HA) = 4.49 +/- 0.18, and pK(H,Ph-OH)(HA) = 9.29 +/- 0.38. Their values at other ionic strengths are more reliably calculated with the empirical Davies equation than any existing model fit. PMID