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Sample records for ha humic acid

  1. Effect of humic acid (HA) on sulfonamide sorption by biochars.

    PubMed

    Lian, Fei; Sun, Binbin; Chen, Xi; Zhu, Lingyan; Liu, Zhongqi; Xing, Baoshan

    2015-09-01

    Effect of quantity and fractionation of loaded humic acid (HA) on biochar sorption for sulfonamides was investigated. The HA was applied in two different modes, i.e. pre-coating and co-introduction with sorbate. In pre-coating mode, the polar fractions of HA tended to interact with low-temperature biochars via H-bonding, while the hydrophobic fractions were likely to be adsorbed by high-temperature biochars through hydrophobic and π-π interactions, leading to different composition and structure of the HA adlayers. The influences of HA fractionation on biochar sorption for sulfonamides varied significantly, depending on the nature of interaction between HA fraction and sorbate. Meanwhile, co-introduction of HA with sulfonamides revealed that the effect of HA on sulfonamide sorption was also dependent on HA concentration. These findings suggest that the amount and fractionation of adsorbed HA are tailored by the surface properties of underlying biochars, which differently affect the sorption for organic contaminants. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Fractal analysis of polyferric chloride-humic acid (PFC-HA) flocs in different topological spaces.

    PubMed

    Wang, Yili; Lu, Jia; Baiyu, Du; Shi, Baoyou; Wang, Dongsheng

    2009-01-01

    The fractal dimensions in different topological spaces of polyferric chloride-humic acid (PFC-HA) flocs, formed in flocculating different kinds of humic acids (HA) water at different initial pH (9.0, 7.0, 5.0) and PFC dosages, were calculated by effective density-maximum diameter, image analysis, and N2 absorption-desorption methods, respectively. The mass fractal dimensions (Df) of PFC-HA flocs were calculated by bi-logarithm relation of effective density with maximum diameter and Logan empirical equation. The Df value was more than 2.0 at initial pH of 7.0, which was 11% and 13% higher than those at pH 9.0 and 5.0, respectively, indicating the most compact flocs formed in flocculated HA water at initial pH of 7.0. The image analysis for those flocs indicates that after flocculating the HA water at initial pH greater than 7.0 with PFC flocculant, the fractal dimensions of D2 (logA vs. logdL) and D3 (logVsphere VS. logdL) of PFC-HA flocs decreased with the increase of PFC dosages, and PFC-HA flocs showed a gradually looser structure. At the optimum dosage of PFC, the D2 (logA vs. logdL) values of the flocs show 14%-43% difference with their corresponding Df, and they even had different tendency with the change of initial pH values. However, the D2 values of the flocs formed at three different initial pH in HA solution had a same tendency with the corresponding Dr. Based on fractal Frenkel-Halsey-Hill (FHH) adsorption and desorption equations, the pore surface fractal dimensions (Ds) for dried powders of PFC-HA flocs formed in HA water with initial pH 9.0 and 7.0 were all close to 2.9421, and the Ds values of flocs formed at initial pH 5.0 were less than 2.3746. It indicated that the pore surface fractal dimensions of PFC-HA flocs dried powder mainly show the irregularity from the mesopore-size distribution and marcopore-size distribution.

  3. Changes in redox properties of Humic Acid (HA) upon sorption to alumina

    NASA Astrophysics Data System (ADS)

    Orsetti, Silvia; Haderlein, Stefan B.; Visser, Anna-Neva

    2014-05-01

    The interaction between humic substances and soil minerals may change important properties and reactivity of the organic matter. In particular, we are interested whether changes in the redox properties of a HA (namely total electron exchange capacity and redox state) occur upon sorption to redox inactive minerals. Sorption of Pahokee Peat humic acid to Al2O3 was studied at pH value of 7.0 in batch experiments, at several HA/oxide ratio. All experiments were conducted in anoxic environment. The required equilibration time was determined by taking aliquots of the suspension at several time intervals and registering the UV-vis spectra of the supernatant; apparent sorption equilibrium (no decrease in UV-vis signal) was achieved after 5 days approximately. Both the suspension (mineral+sorbed HA, plus supernatant) and the supernatant after centrifugation were analyzed using mediated electrochemical techniques, and the electron donating and accepting capacities (EDC and EAC, respectively) were determined. In addition, SUVA was calculated for each batch. These preliminary results show a slight increase in the SUVA of the supernatant upon sorption, which would indicate a preferential sorption of more aliphatic fractions. Interestingly, the total electron exchange capacities (EEC) of the supernatants showed no significant differences to that of the stock HA, whereas the EEC of the whole suspension showed values up to twice the one from the stock HA. The EDC/EAC (which can be interpreted as a measure of the redox state of the sample) also showed same values for stock and supernatants, being the values of the whole suspensions towards the reduced side. Therefore, such preliminary results would indicate not a change in the redox properties of the dissolved HA, but only for the sorbed one. The sorbed fraction seems to present higher redox activity (higher EEC) and a more reduced state than the stock HA. Given the absence of redox transfer between the HA and the oxide, it could

  4. The novel kinetics expression of Cadmium (II) removal using green adsorbent horse dung humic acid (Hd-Ha)

    NASA Astrophysics Data System (ADS)

    Basuki, Rahmat; Santosa, Sri Juari; Rusdiarso, Bambang

    2017-03-01

    Humic acid from dry horse dung powder has been prepared and this horse dung humic acid (HD-HA) was then applied as a sorbent to adsorb Cadmium(II) from a solution. Characterization of HD-HA was conducted by detection of its functional group, UV-Vis spectra, ash level, and total acidity. Result of the work showed that HD-HA had similar character compared with peat soil humic acid (PS-HA) and previous researchers. The adsorption study of this work was investigated by batch experiment in pH 5. The thermodynamics parameters in this work were determined by the Langmuir isotherm model for monolayer sorption and Freundlich isotherm model multilayer sorption. Monolayer sorption capacity (b) for HD-HA was 1.329 × 10-3 mol g-1, equilibrium constant (K) was 5.651 (mol/L)-1, and multilayer sorption capacity was 2.646 × 10-2 mol g-1. The kinetics parameters investigated in this work were determined by the novel kinetics expression resulted from the mathematical derivation the availability of binding sites of sorbent. Adsorption rate constant (ka) from this novel expression was 43.178 min-1 (mol/L)-1 and desorption rate constant (kd) was 1.250 × 10-2 min-1. Application of the kinetics model on sorption Cd(II) onto HD-HA showed the nearly all of models gave a good linearity. However, only this proposed kinetics expression has good relation with Langmuir model. The novel kinetics expression proposed in this paper seems to be more realistic and reasonable and close to the experimental real condition because the value of ka/kd (3452 (mol/L)-1) was fairly close with K from Langmuir isotherm model (5651 (mol/L)-1). Comparison of this novel kinetics expression with well-known Lagergren pseudo-first order kinetics and Ho pseudo-second order kinetics was also critically discussed in this paper.

  5. Determination of humic and fulvic acids in commercial solid and liquid humic products by alkaline extraction and gravimetric determination

    USDA-ARS?s Scientific Manuscript database

    Increased use of humic substances in agriculture has generated intense interest among producers, consumers, and regulators for an accurate and reliable method for quantification of humic (HA) and fulvic acids (FA) in raw ores and products. Here we present a thoroughly validated method, the Humic Pro...

  6. Adsorption behaviour of hydrogarnet for humic acid

    NASA Astrophysics Data System (ADS)

    Maeda, Hirotaka; Kurosaki, Yuichi; Nakayama, Masanobu; Ishida, Emile Hideki; Kasuga, Toshihiro

    2018-04-01

    Discharge of humic acid (HA) in aqueous environments is a key health and aesthetic issue. The present work investigates the use of hydrogarnet as a novel adsorbent for HA. Hydrogarnet was hydrothermally synthesized with different solvents to control the chemical composition. Hydrogarnet with three types of chemical compositions had better adsorption properties for HA than hydrogarnet with a single chemical composition. Controlling the chemical composition of hydrogarnet increased the number of hydroxyl groups and the overall binding energy of the system, leading to changes in the zeta potential. The enhancement of these adsorption properties is related to the increased numbers of hydroxyl groups on the surface and their diverse binding energies.

  7. Iodine binding to humic acid.

    PubMed

    Bowley, H E; Young, S D; Ander, E L; Crout, N M J; Watts, M J; Bailey, E H

    2016-08-01

    The rate of reactions between humic acid (HA) and iodide (I(-)) and iodate (IO3(-)) have been investigated in suspensions spiked with (129)I at concentrations of 22, 44 and 88 μg L(-1) and stored at 10 °C. Changes in the speciation of (129)I(-), (129)IO3(-) and mixed ((129)I(-) + (129)IO3(-)) spikes were monitored over 77 days using liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS). In suspensions spiked with (129)I(-) 25% of the added I(-) was transformed into organic iodine (Org-(129)I) within 77 days and there was no evidence of (129)IO3(-) formation. By contrast, rapid loss of (129)IO3(-) and increase in both (129)I(-) and Org-(129)I was observed in (129)IO3(-)-spiked suspensions. However, the rate of Org-(129)I production was greater in mixed systems compared to (129)IO3(-)-spiked suspensions with the same total (129)I concentration, possibly indicating IO3(-)I(-) redox coupling. Size exclusion chromatography (SEC) demonstrated that Org-(129)I was present in both high and low molecular weight fractions of the HA although a slight preference to bond with the lower molecular weight fractions was observed indicating that, after 77 days, the spiked isotope had not fully mixed with the native (127)I pool. Iodine transformations were modelled using first order rate equations and fitted rate coefficients determined. However, extrapolation of the model to 250 days indicated that a pseudo-steady state would be attained after ∼200 days but that the proportion of (129)I incorporated into HA was less than that of (127)I indicating the presence of a recalcitrant pool of (127)I that was unavailable for isotopic mixing. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Humic acid protein complexation

    NASA Astrophysics Data System (ADS)

    Tan, W. F.; Koopal, L. K.; Weng, L. P.; van Riemsdijk, W. H.; Norde, W.

    2008-04-01

    Interactions of purified Aldrich humic acid (PAHA) with lysozyme (LSZ) are investigated. In solution LSZ is moderately positively and PAHA negatively charged at the investigated pH values. The proton binding of PAHA and of LSZ is determined by potentiometric proton titrations at various KCl concentrations. It is also measured for two mixtures of PAHA-LSZ and compared with theoretically calculated proton binding assuming no mutual interaction. The charge adaptation due to PAHA-LSZ interaction is relatively small and only significant at low and high pH. Next to the proton binding, the mass ratio PAHA/LSZ at the iso-electric point (IEP) of the complex at given solution conditions is measured together with the pH using the Mütek particle charge detector. From the pH changes the charge adaptation due to the interaction can be found. Also these measurements show that the net charge adaptation is weak for PAHA-LSZ complexes at their IEP. PAHA/LSZ mass ratios in the complexes at the IEP are measured at pH 5 and 7. At pH 5 and 50 mmol/L KCl the charge of the complex is compensated for 30-40% by K +; at pH 7, where LSZ has a rather low positive charge, this is 45-55%. At pH 5 and 5 mmol/L KCl the PAHA/LSZ mass ratio at the IEP of the complex depends on the order of addition. When LSZ is added to PAHA about 25% K + is included in the complex, but no K + is incorporated when PAHA is added to LSZ. The flocculation behavior of the complexes is also different. After LSZ addition to PAHA slow precipitation occurs (6-24 h) in the IEP, but after addition of PAHA to LSZ no precipitation can be seen after 12 h. Clearly, PAHA/LSZ complexation and the colloidal stability of PAHA-LSZ aggregates depend on the order of addition. Some implications of the observed behavior are discussed.

  9. Effect of humic acid source on humic acid adsorption onto titanium dioxide nanoparticles.

    PubMed

    Erhayem, Mohamed; Sohn, Mary

    2014-02-01

    In many studies, different humic acid (HA) sources are used interchangeably to evaluate the effect of organic matter on geochemical processes in the environment. This research looks more specifically at the effect of HA source on HA adsorption onto nano-TiO2 and how HA adsorption affects the fate and transport of nano-TiO2. In this study, six humic acids (HAs) were studied which were derived from soils (SLHA), or from sediments (SDHA) all originating from the state of Florida. Humic acid adsorption onto titanium dioxide nanoparticles (nano-TiO2) and the sedimentation of HA-coated and uncoated nano-TiO2 were monitored by Ultraviolet-visible (UV-vis) spectroscopy. Synchronous scan fluorescence (SSF) spectroscopy was used to complement the study of HA adsorption onto nano-TiO2. Phosphate buffer was found to reduce the amount of HA adsorbed onto nano-TiO2 relative to solutions of NaCl of the same pH and ionic strength. Adsorption constant values (Kads) for HAs varied in the order SLHA>FSDHA (freshwater sedimentary HA)>ESDHA (estuarine sedimentary HA). SSF results suggested that the more highly conjugated fractions of HA, which are more prevalent in SLHAs versus SDHAs, were preferentially adsorbed. In order to better understand the relationship between adsorption and aggregation, sedimentation studies were conducted and it was found that the percentage of nano-TiO2 sedimentation was preferentially enhanced in the order of the presence of SLHA>FSDHA>ESDHA. The extent of nano-TiO2 sedimentation was decreased with increasing HA concentration. TEM imaging of nano-TiO2 confirmed that nano-TiO2 was aggregated in the presence of HAs. The findings in this study suggest that HAs from different sources influence the fate and transport of nano-TiO2 in the environment differently. © 2013.

  10. Interaction of Humic Acids with Organic Toxicants

    NASA Astrophysics Data System (ADS)

    Tchaikovskaya, O. N.; Yudina, N. V.; Maltseva, E. V.; Nechaev, L. V.; Svetlichnyi, V. A.

    2016-08-01

    Interaction of humic acids with polyaromatic hydrocarbons (PAH) (naphthalene and anthracene) and triazole series fungicides (cyproconazole (CC) and tebuconazole (TC)) is investigated by the method of fluorescence quenching depending on the concentration of substances in solutions and their structural features. Humic acids were modified by mechanochemical activation in a planetary mill. The complex character of intermolecular interactions between PAH and fungicides with humic acids, including donor-acceptor and hydrophobic binding, is established. Thermodynamically stable conformations of biocide molecules were estimated using ChemOffice CS Chem3D 8.0 by methods of molecular mechanics (MM2) and molecular dynamics. Biocide molecules with pH 7 are in energetically favorable position when the benzene and triazole rings are almost parallel to each other. After acidification of solutions to pH 4.5, the CC molecule retains the geometry for which donor-acceptor interactions are possible: the benzene ring in the molecule represents the electron donor, and triazole is the acceptor. In this case, the electron density in CC is redistributed easier, which is explained by a smaller number of carbon atoms between the triazole and benzene rings, unlike TC. As a result, the TC triazole ring is protonated to a greater degree, acquiring a positive charge, and enters into donoracceptor interactions with humic acid (HA) samples. The above-indicated bond types allow HA to participate actively in sorption processes and to provide their interaction with biocides and PAH and hence, to act as detoxifying agents for recultivation of the polluted environment.

  11. Interaction of humic acids and humic-acid-like polymers with herpes simplex virus type 1

    NASA Astrophysics Data System (ADS)

    Klöcking, Renate; Helbig, Björn

    The study was performed in order to compare the antiviral activity against herpes simplex virus type 1 (HSV-1) of synthetic humic-acid-like polymers to that of their low-molecular-weight basic compounds and naturally occurring humic acids (HA) in vitro. HA from peat water showed a moderate antiviral activity at a minimum effective concentration (MEC) of 20 µg/ml. HA-like polymers, i.e. the oxidation products of caffeic acid (KOP), hydrocaffeic acid (HYKOP), chlorogenic acid (CHOP), 3,4-dihydroxyphenylacetic acid (3,4-DHPOP), nordihydroguaretic acid (NOROP), gentisinic acid (GENOP), pyrogallol (PYROP) and gallic acid (GALOP), generally inhibit virus multiplication, although with different potency and selectivity. Of the substances tested, GENOP, KOP, 3,4-DHPOP and HYKOP with MEC values in the range of 2 to 10 µg/ml, proved to be the most potent HSV-1 inhibitors. Despite its lower antiviral potency (MEC 40 µg/ml), CHOP has a remarkable selectivity due to the high concentration of this polymer that is tolerated by the host cells (>640 µg/ml). As a rule, the antiviral activity of the synthetic compounds was restricted to the polymers and was not preformed in the low-molecular-weight basic compounds. This finding speaks in favour of the formation of antivirally active structures during the oxidative polymerization of phenolic compounds and, indirectly, of corresponding structural parts in different HA-type substances.

  12. Sorption of metals on humic acid

    NASA Astrophysics Data System (ADS)

    Kerndorff, H.; Schnitzer, M.

    1980-11-01

    The sorption on humic acid (HA) of metals from an aqueous solution containing Hg(II). Fe(III), Pb, Cu, Al, Ni, Cr(III), Cd, Zn, Co and Mn, was investigated with special emphasis on effects of pH, metal concentration and HA concentration. The sorption efficiency tended to increase with rise in pH, decrease in metal concentration and increase in HA concentration of the equilibrating solution. At pH 2.4. the order of sorption was: Hg≫ Fe≫ Pb≫ CuAl ≫ Ni ≫ CrZnCdCoMn. At pH 3.7. the order was: Hg and Fe were always most readily removed, while Co and Mn were sorbed least readily. There were indications of competition for active sites (CO 2H and phenolic OH groups) on the HA between the different metals. We were unable to find correlations between the affinities of the eleven metals to sorb on HA and their atomic weights, atomic numbers, valencies, and crystal and hydrated ionic radii. The sorption of the eleven metals on the HA could be described by the equation Y = 100/[1 + exp - (A + BX)], where Y = % metal removed by HA; X = mgHA; and A and B are empirical constants.

  13. Forms and Lability of Phosphorus in Humic Acid Fractions of Hord Silt Loam Soil

    USDA-ARS?s Scientific Manuscript database

    Phosphorus (P) has long been known to be present in soil humic fractions, but little is known about specific P forms in humic fractions, or their lability. We extracted the mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fractions from a Nebraska Hord silt loam soil under continuous c...

  14. Equivalent weight of humic acid from peat

    USGS Publications Warehouse

    Pommer, A.M.; Breger, I.A.

    1960-01-01

    By means of discontinuous titration, the equivalent weight of humic acid isolated from a peat was found to increase from 144 to 183 between the third and fifty-second day after the humic acid was dissolved. Infra-red studies showed that the material had probably condensed with loss of carbonyl groups. ?? 1960.

  15. Pyrolysis of humic and fulvic acids

    USGS Publications Warehouse

    Wershaw, R. L.; Bohner, G.E.

    1969-01-01

    Pyrolysis of humic and fulvic acids isolated from a North Carolina soil yields a variety of aromatic, heterocyclic and straight chain organ compounds. The pyrolysis products identified by gas chromatography and mass spectrometry indicate that humic and fulvic acids have aromatic and polysaccharide structures in their molecules. ?? 1969.

  16. Effects of humic acids in vitro.

    PubMed

    Vašková, Janka; Veliká, Beáta; Pilátová, Martina; Kron, Ivan; Vaško, Ladislav

    2011-06-01

    Humic acids are known for their overall positive health and productivity effects in animal feeding trials and, controversially, as an aetiological factor of cancer. We tried to assess the in vitro effect of humic acids from a selected source in Slovakia when used at recommended prophylactic dosage. We investigated antioxidant properties, enzymatic and non-enzymatic antioxidant defence system in liver mitochondria and cultured cancer cell lines in vitro. We observed a significant decrease in superoxide dismutase activity after humic acids treatment irrespective of dissolving in dimethyl sulphoxide or direct addition to mitochondria suspension in a respiration medium. Activities of other antioxidant enzymes measured, such as glutathione peroxidase and glutathione reductase, showed no significant differences from the control as well as the reduced glutathione content. Percentage of inhibition by humic acids of superoxide radical indicated lower efficacy compared with that of hydroxyl radical. Survival of six different cancer cells lines indicated that only the acute T lymphoblastic leukaemia cell line was sensitive to the tested humic acids. Despite relatively low solubility in aqueous solutions, humic acids from the selected source participated in redox regulation. By recapturing the radicals, humic acids reloaded the antioxidant defensive mechanism. Results from in vitro study conducted with humic acids from the natural source showed potential of these substances as promising immunity enhancing agents.

  17. Spectroscopy and photochemistry of humic acids

    NASA Astrophysics Data System (ADS)

    Sokolova, I. V.; Vershinin, N. O.; Skobczova, K. A.; Tchaikovskaya, O. N.; Mayer, G. V.

    2018-04-01

    Spectroscopy and photochemistry of humic acids are discussed. The samples of HAs fractions were obtained from Fluka Chemical Co and prepared from peat of Western Siberia region. The comparative analysis of these acids with the sample of humic acids allocated from brown coal is carried out. A specific feature of the reactor is the use of barrier discharge excilamp (KrCl) with radiation wavelength λ = 222 nm. Influence of the received humic acids on process of photodegradation of herbicide - 2.4-dichlorophenoxyacetic acid is considered.

  18. Adsorption interactions of humic acids with biocides

    NASA Astrophysics Data System (ADS)

    Mal'Tseva, E. V.; Ivanov, A. A.; Yudina, N. V.

    2009-11-01

    The chemical composition of humic acids from brown coal (Aldrich) was determined by element analysis, 13C NMR spectroscopy, and potentiometric titration. The adsorption ability of humic acids with different biocides (cyproconasol, propiconasol, tebuconasol, irgarol 1051, and DCOIT) was studied. The adsorption ability of a mixture of biocides in aqueous solutions was higher than that of the individual components. The limiting concentration of humic acids at which adsorption of biocides was maximum was determined. Adsorption constants were calculated by the Freundlich equation for each biocide in aqueous solution.

  19. Thermodynamics of Molybdate Binding to Humic Acid

    NASA Astrophysics Data System (ADS)

    Thalhammer, K.; Gilbert, B.

    2016-12-01

    Molybdenum is an essential nutrient for diazotrophic bacteria that use nitrogenase I to fix atmospheric nitrogen in soils into bioavailable forms such as ammonia. This metalloid is released during rock weathering processes and at neutral pH it exists primarily as the soluble oxyanion molybdate, MoO42-. It has been established that molybdate mobility and bioavailability in soils is influenced by sorption to mineral surfaces and complexation by natural organic matter (NOM). The molybdate ion is readily bound by ortho dihydroxybenzene molecules such as catechol and catechol groups in siderophores. Humic acids (HA) found in NOM contain abundant phenolic groups and extended X-ray absorption fine structure (EXAFS) spectroscopy demonstrated that molybdate is bound by catechol-containing molecules in soil organic matter1. However, to our knowledge no quantitative determination of the affinity of molybdate to HA has been reported. We studied the interactions of molybdate with Suwannee River HA using ultraviolet-visible (UV-vis) absorption spectroscopy and isothermal titration calorimetry (ITC) to determine the conditional equilibrium constant for complexation at neutral pH. We further used ITC to investigate the thermodynamic contributions to complexation and the interaction kinetics. Addition of molybdate to HA caused the formation of complexes with UV-vis absorption spectra in good agreement with molybdate-catechol species indicating catechol groups to be the primary ligands in HA. ITC data revealed that binding enthalpies and kinetics were strongly influenced by ionic strength, suggesting a role for macromolecular reorganization driven by metalloid addition. 1. Wichard et al., Nature Geoscience 2, 625 - 629 (2009).

  20. Analysis of carbon functional groups in mobile humic acid and recalcitrant calcium humate extracted from eight US soils

    USDA-ARS?s Scientific Manuscript database

    Solid state 13C nuclear magnetic resonance (NMR) spectroscopy is a common tool to study the structure of soil humic fractions; however, knowledge regarding carbon structural relationships in humic fractions is limited. In this study, mobile humic acid (MHA) and recalcitrant calcium humate (CaHA) fr...

  1. Beneficial effects of humic acid on micronutrient availability to wheat

    NASA Technical Reports Server (NTRS)

    Mackowiak, C. L.; Grossl, P. R.; Bugbee, B. G.

    2001-01-01

    Humic acid (HA) is a relatively stable product of organic matter decomposition and thus accumulates in environmental systems. Humic acid might benefit plant growth by chelating unavailable nutrients and buffering pH. We examined the effect of HA on growth and micronutrient uptake in wheat (Triticum aestivum L.) grown hydroponically. Four root-zone treatments were compared: (i) 25 micromoles synthetic chelate N-(4-hydroxyethyl)ethylenediaminetriacetic acid (C10H18N2O7) (HEDTA at 0.25 mM C); (ii) 25 micromoles synthetic chelate with 4-morpholineethanesulfonic acid (C6H13N4S) (MES at 5 mM C) pH buffer; (iii) HA at 1 mM C without synthetic chelate or buffer; and (iv) no synthetic chelate or buffer. Ample inorganic Fe (35 micromoles Fe3+) was supplied in all treatments. There was no statistically significant difference in total biomass or seed yield among treatments, but HA was effective at ameliorating the leaf interveinal chlorosis that occurred during early growth of the nonchelated treatment. Leaf-tissue Cu and Zn concentrations were lower in the HEDTA treatment relative to no chelate (NC), indicating HEDTA strongly complexed these nutrients, thus reducing their free ion activities and hence, bioavailability. Humic acid did not complex Zn as strongly and chemical equilibrium modeling supported these results. Titration tests indicated that HA was not an effective pH buffer at 1 mM C, and higher levels resulted in HA-Ca and HA-Mg flocculation in the nutrient solution.

  2. A new standardized method for quantification of humic and fulvic acids in humic ores and commercial products.

    PubMed

    Lamar, Richard T; Olk, Daniel C; Mayhew, Lawrence; Bloom, Paul R

    2014-01-01

    Increased use of humic substances in agriculture has generated intense interest among producers, consumers, and regulators for an accurate and reliable method to quantify humic acid (HA) and fulvic acid (FA) in raw ores and products. Here we present a thoroughly validated method, the new standardized method for determination of HA and FA contents in raw humate ores and in solid and liquid products produced from them. The methods used for preparation of HA and FA were adapted according to the guidelines of the International Humic Substances Society involving alkaline extraction followed by acidification to separate HA from the fulvic fraction. This is followed by separation of FA from the fulvic fraction by adsorption on a nonionic macroporous acrylic ester resin at acid pH. It differs from previous methods in that it determines HA and FA concentrations gravimetrically on an ash-free basis. Critical steps in the method, e.g., initial test portion mass, test portion to extract volume ratio, extraction time, and acidification of alkaline extract, were optimized for maximum and consistent recovery of HA and FA. The method detection limits for HA and FA were 4.62 and 4.8 mg/L, respectively. The method quantitation limits for HA and FA were 14.7 and 15.3 mg/L, respectively.

  3. Natural Humic-Acid-Based Phototheranostic Agent.

    PubMed

    Miao, Zhao-Hua; Li, Kai; Liu, Pei-Ying; Li, Zhenglin; Yang, Huanjie; Zhao, Qingliang; Chang, Manli; Yang, Qingzhu; Zhen, Liang; Xu, Cheng-Yan

    2018-04-01

    Humic acids, a major constituent of natural organic carbon resources, are naturally formed through the microbial biodegradation of animal and plant residues. Due to numerous physiologically active groups (phenol, carboxyl, and quinone), the biomedical applications of humic acid have been already investigated across different cultures for several centuries or even longer. In this work, sodium humate, the sodium salt of humic acid, is explored as phototheranostic agent for light-induced photoacoustic imaging and photothermal therapy based on intrinsic absorption in the near-infrared region. The purified colloidal sodium humate exhibits a high photothermal conversion efficiency up to 76.3%, much higher than that of the majority of state-of-the-art photothermal agents including gold nanorods, Cu 9 S 5 nanoparticles, antimonene quantum dots, and black phosphorus quantum dots, leading to obvious photoacoustic enhancement in vitro and in vivo. Besides, highly effective photothermal ablation of HeLa tumor is achieved through intratumoral injection. Impressively, sodium humate reveals ultralow toxicity at the cellular and animal levels. This work promises the great potential of humic acids as light-mediated theranostic agents, thus expanding the application scope of traditional humic acids in biomedical field. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Amide and Ester-Functionalized Humic Acid for Fuel Combustion Enhancement

    NASA Astrophysics Data System (ADS)

    Riggs, Mark

    . The modified humic acid samples were diluted with kerosene to identify the influence on combustion properties. Butyl-modified humic acid samples decreased the molar enthalpy of combustion. Hexyl, octyl, and decyl-modified humic acids improved the combustion values. Decyl amide-modified humic acid showed the largest improvement of these mixtures with a 0.9% increase from the expected molar enthalpy of combustion with a loading percentage of 0.36% in kerosene. Octyl amide-modified and octyl ester-modified humic acid mixtures were prepared in 0.05, 0.1, and 1% loading percentage dilutions to study the effect of modified humic acid loading percent on combustion properties. The 0.1% dilution showed the largest increase of the expected molar enthalpy of combustion by 1.14% and 0.4% for amide-modified HA and ester-modified HA, respectively.

  5. Spectral Study of Modified Humic Acids from Lignite

    NASA Astrophysics Data System (ADS)

    Zherebtsov, Sergey; Malyshenko, Natalya; Bryukhovetskaya, Ludmila; Ismagilov, Zinfer

    2017-11-01

    The IR-Fourier, ESR and solid-state 13C NMR analysis are used for investigation of unmodified and modified humic acids obtained from Tisul lignite (the Kansko-Achinsk Basin). Treatment with Hydrogen peroxide used for modification of humic acids and it changes the functionalgroup composition of the humic acids and increases the sorptional capacity

  6. Selective binding behavior of humic acid removal by aluminum coagulation.

    PubMed

    Jin, Pengkang; Song, Jina; Yang, Lei; Jin, Xin; Wang, Xiaochang C

    2018-02-01

    The reactivity characteristics of humic acid (HA) with aluminium coagulants at different pH values was investigated. It revealed that the linear complexation reaction occurred between aluminum and humic acid at pH < 7, and the reaction rate increased as the pH increased from 2 to 6. While at pH = 7, most of the dosed aluminum existed in the form of free aluminum and remained unreacted in the presence of HA until the concentration reached to trigger Al(OH) 3(s) formation. Differentiating the change of functional groups of HA by 1 H nuclear magnetic resonance spectroscopy and X-ray photoelectron spectra analysis, it elucidated that there was a selective complexation between HA and Al with lower Al dosage at pH 5, which was probably due to coordination of the activated functional groups onto aluminium. While almost all components were removed proportionally by sweep adsorption without selectivity at pH 7, as well as that with higher Al dosage at pH 5. This study provided a promising pathway to analyse the mechanism of the interaction between HA and metal coagulants in future. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Synthesis and characterization of agricultural controllable humic acid superabsorbent.

    PubMed

    Gao, Lijuan; Wang, Shiqiang; Zhao, Xuefei

    2013-12-01

    Humic acid superabsorbent polymer (P(AA/AM-HA)) and superabsorbent polymer (P(AA/AM)) were synthesized by aqueous solution polymerization method using acrylic acid (AA), acrylamide (AM) and humic acid (HA) as raw material. The effects of N,N'-methylenebisacrylamide (MBA) crosslinking agent, potassium peroxydisulfate (KPS) initiator, reaction temperature, HA content, ratio of AA to AM, concentration of monomer and neutralization of AA on water absorption were investigated. Absorption and desorption ratios of nitrogen fertilizer and phosphate fertilizer were also investigated by determination of absorption and desorption ratio of NH4(+), PO4(3-) on P(AA/AM-HA) and P(AA/AM). The P(AA/AM-HA) and P(AA/AM) were characterized by Fourier translation infrared spectroscopy, biological photomicroscope and scanning electron microscopy (SEM). The optimal conditions obtained were as follows: the weight ratio of MBA to AA and AM was 0.003; the weight ratio of KPS to AA and AM was 0.008; the weight ratio of HA to AA was 0.1; the mole ratio of AM to AA is 0.1; the mole ratio of NaOH to AA is 0.9; the reaction temperature was 60°C. P(AA/AM-HA) synthesized under optimal conditions, has a good saline tolerance, its water absorbency in distilled water and 0.9 wt.% saline solution is 1180 g/g and 110 g/g, respectively. P(AA/AM-HA) achieves half saturation in 6.5 min. P(AA/AM-HA) is superior to P(AA/AM) on absorption of NH4(+), PO4(3-). The SEM micrograph of P(AA/AM-HA) shows a fine alveolate structure. The biological optical microscope micrograph of P(AA/AM-HA) shows a network structure. Graft polymerization between P(AA/AM) and HA was demonstrated by infrared spectrum. The P(AA/AM-HA) superabsorbent has better absorbing ability of water and fertilizer, electrolytic tolerance and fewer cost than P(AA/AM) superabsorbent. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  8. Novel humic acid-bonded magnetite nanoparticles for protein immobilization.

    PubMed

    Bayrakci, Mevlut; Gezici, Orhan; Bas, Salih Zeki; Ozmen, Mustafa; Maltas, Esra

    2014-09-01

    The present paper is the first report that introduces (i) a useful methodology for chemical immobilization of humic acid (HA) to aminopropyltriethoxysilane-functionalized magnetite iron oxide nanoparticles (APS-MNPs) and (ii) human serum albumin (HSA) binding to the obtained material (HA-APS-MNPs). The newly prepared magnetite nanoparticle was characterized by using Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and elemental analysis. Results indicated that surface modification of the bare magnetite nanoparticles (MNPs) with aminopropyltriethoxysilane (APS) and HA was successfully performed. The protein binding studies that were evaluated in batch mode exhibited that HA-APS-MNPs could be efficiently used as a substrate for the binding of HSA from aqueous solutions. Usually, recovery values higher than 90% were found to be feasible by HA-APS-MNPs, while that value was around 2% and 70% in the cases of MNPs and APS-MNPs, respectively. Hence, the capacity of MNPs was found to be significantly improved by immobilization of HA. Furthermore, thermal degradation of HA-APS-MNPs and HSA bonded HA-APS-MNPs was evaluated in terms of the Horowitz-Metzger equation in order to determine kinetic parameters for thermal decomposition. Activation energies calculated for HA-APS-MNPs (20.74 kJmol(-1)) and HSA bonded HA-APS-MNPs (33.42 kJmol(-1)) implied chemical immobilization of HA to APS-MNPs, and tight interactions between HA and HA-APS-MNPs. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Humic Acid Isolations from Lignite by Ion Exchange Method

    NASA Astrophysics Data System (ADS)

    Kurniati, E.; Muljani, S.; Virgani, D. G.; Neno, B. P.

    2018-01-01

    The humic liquid is produced from lignite extraction using alkali solution. Conventional humic acid is obtained by acidifying a humic solution using HCl. The purpose of this research is the formation of solid humic acid from lignite by ion exchange method using cation resin. The results showed that the addition of cation resin was able to reduce the pH from 14 to pH 2 as well as the addition of acid (HCl), indicating the exchange of Na + ions with H + ions. The reduction of pH in the humic solution is influenced by the concentration of sodium ions in the humic solution, the weight of the cation resin, and the ion exchange time. The IR spectra results are in good agreement for humic acid from lignite characterization.

  10. EFFECTS OF HUMIC ACID PURIFICATION ON INTERACTION WITH HYDROPHOBIC ORGANIC MATTER: EVIDENCE FROM FLUORESCENCE BEHAVIOR. (R822832)

    EPA Science Inventory

    Conventional isolation of humic materials from natural
    matrixes includes demineralization by treatment with HF/HCl. The possible effect of this on the structural integrity of
    humic acid (HA) was investigated by comparing the
    interactions of two aqueous HAs, one produc...

  11. An innovative zinc oxide-coated zeolite adsorbent for removal of humic acid

    EPA Science Inventory

    Zinc oxide (ZnO)-coated zeolite adsorbents were developed by both nitric acid modification and Zn(NO3)2•6H2O functionalization of zeolite. The developed adsorbents were used for the removal of humic acid (HA) from aqueous solutions. The adsorption capacity of the adsorbents at 21...

  12. Comparative study of humic acid removal and floc characteristics by electrocoagulation and chemical coagulation.

    PubMed

    Semerjian, Lucy; Damaj, Ahmad; Salam, Darine

    2015-11-01

    The current study aims at investigating the efficiency of electrocoagulation for the removal of humic acid from contaminated waters. In parallel, conventional chemical coagulation was conducted to asses humic acid removal patterns. The effect of varying contributing parameters (matrix pH, humic acid concentration, type of electrode (aluminum vs. iron), current density, solution conductivity, and distance between electrodes) was considered to optimize the electrocoagulation process for the best attainable humic acid removal efficiencies. Optimum removals were recorded at pH of 5.0-5.5, an electrical conductivity of 3000 μS/cm at 25 °C, and an electrode distance of 1 cm for both electrode types. With aluminum electrodes, a current density of 0.05 mA/cm2 outperformed 0.1 mA/cm2 yet not higher densities, whereas a current density of 0.8 mA/cm2 was needed for iron electrodes to exhibit comparable performance. With both electrode types, higher initial humic acid concentrations were removed at a slower rate but ultimately attained almost complete removals. On the other hand, the best humic acid removals (∼90%) by chemical coagulation were achieved at 4 mg/L for both coagulants. Also, higher removals were attained at elevated initial humic acid concentrations. Humic acid removals of 90% or higher at an initial HA concentration of 40 mg/L were exhibited, yet alum performed better at the highest experimented concentration. It was evident that iron flocs were larger, denser, and more geometrical in shape compared to aluminum flocs.

  13. Photodegradation of chlorpyrifos with humic acid-bound suspended matter.

    PubMed

    Amarathunga, A A D; Kazama, F

    2014-09-15

    Land exploitation in several developing countries, including tropical areas, has caused a rapid change of the landscape, from forest to farms. This has led to an increase of pesticide use and concentration of suspended matter in river waters, which may cause soil erosion of these areas. Humic acid (HA), one of the main components in the soil particulate organic matter, has a positive effect on the photodegradation of organic matter in water; however, the efficiency of HA-bound suspended matter (HABSM) for pesticide photodegradation is not known. The aim of this study is to clarify the effect of HABSM on the photodegradation of chlorpyrifos employed in artificial soil particulate covered with HA. Experiments were carried out in liquid HA phase, with/without HABSM phase and HABSM with additional LHA phase under light. The adsorption procedure of the pesticide on HABSM was also studied. Our results reveal that adsorption takes place within a short time period on HABSM and that photodegradation is successfully achieved. The additional LHA+HABSM phase have not demonstrated any significant effect of HA concentration to photodegradation of chlorpyrifos. For instance, when 2.0mg/L chlorpyrifos was used in the experiments, concentration reductions caused by adsorption, photodegradation under suspended matter and HABSM were found to be 19.3, 17.7, and 61.7% respectively. This finding suggests that HABSM can be considered as a potential catalyst for pesticide photodegradation under sunlight. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Effects of Humic Acids in Chronic Lead Poisoning.

    PubMed

    Vašková, Janka; Krempaská, Klára; Žatko, Daniel; Mudroň, Pavol; Glinská, Gabriela; Vaško, Ladislav

    2018-05-10

    Chronic exposure to lead causes disruption to energy production mechanisms and tissue damage, in particular through its binding to thiol groups and competition for zinc binding sites. We investigated the possibility of preventing the consequences of chronic lead poisoning by administration of three different doses of humic acids (HAs) into feed with the aim of establishing an effective HA dose. During the 10-week experiment, a sub-lethal dose of lead acetate was given to rats during the first 5 weeks, with continuous administration of HA over 10 weeks. Measurements were taken to determine the content of the metals Pb, Mn, Cu, Fe and Zn; the metalloid Se; and selected antioxidant markers in the heart, liver, kidney and plasma after the first, fifth and tenth weeks of experiment. The administration of lead and HAs clearly affects the redistribution of the elements and the activity of the antioxidant enzymes. This fact was particularly highlighted in the lead-only group as, within the experiment, significantly higher Pb concentrations were found only in the plasma of this group. However, in the group with 1% HA administered with lead, we observed a rise in Zn concentrations in the organs and the deposition of Fe into the liver. Decreased glutathione reductase activity in the plasma and balanced reduced glutathione concentrations indicated sufficient efficiency of redox reactions. SOD activities were among those affected most strongly, with only the 1% HA group showing no effect on heavy metal redistribution as a result of HA administration.

  15. Pyrrolidone - a new solvent for the methylation of humic acid

    USGS Publications Warehouse

    Wershaw, R. L.; Pinckney, D.J.; Booker, S.E.

    1975-01-01

    In the past, humic acid has been methylated by suspending it in a solution of diazomethane in diethyl ether, and degrading the partly methylated humic acid to release those parts of the molecule that were methylated. Only small fragments of the molecule have been identified by this technique. In the procedure described here the humic acid is dissolved in 2-pyrrolidone and methylated by the addition of diazomethane in diethyl ether and ethanol to the solution. Because the humic acid is completely dissolved in the reaction medium, disaggregation of the humic acid particles takes place and much more complete methylation is obtained. The methylated products may be fractionated by countercurrent distribution and analyzed by mass spectrometry.

  16. The Acute Effect of Humic Acid on Iron Accumulation in Rats.

    PubMed

    Cagin, Yasir Furkan; Sahin, N; Polat, A; Erdogan, M A; Atayan, Y; Eyol, E; Bilgic, Y; Seckin, Y; Colak, C

    2016-05-01

    Free iron leads to the formation of pro-oxidant reactive oxygen species (ROS). Humic acids (HAs) enhance permeability of cellular wall and act as a chelator through electron transferring. This study was designed to test chelator effect of HA on iron as well as its anti-oxidant effect against the iron-induced hepatotoxicity and cardiotoxicity. The rats used were randomly divided into four groups (n = 8/group): group I (the control group); group II (the HA group), humic acid (562 mg/kg) was given over 10 days by oral gavage; group III (the iron group), iron III hydroxide polymaltose (250 mg/kg) was given over 10 days by intraperitoneal route; and group IV (the HA plus iron group), received the iron (similar to group II) plus humic acid (similar to those in groups II and III) group. Blood and two tissue samples both from liver and heart were obtained for biochemical and histopathological evaluations. Iron deposition, the iron-induced hepatotoxicity, and cardiotoxicity were demonstrated by histopathological and biochemical manner. However, no significant differences were observed in the serum biochemical values and the histopathological results among the iron and the HA plus iron groups in the liver tissue but not in the heart tissue. The protective effects of humic acid against iron-induced cardiotoxicity were shown but not against hepatotoxicity in our study.

  17. Cd(II) Sorption on Montmorillonite-Humic acid-Bacteria Composites

    PubMed Central

    Du, Huihui; Chen, Wenli; Cai, Peng; Rong, Xingmin; Dai, Ke; Peacock, Caroline L.; Huang, Qiaoyun

    2016-01-01

    Soil components (e.g., clays, bacteria and humic substances) are known to produce mineral-organic composites in natural systems. Herein, batch sorption isotherms, isothermal titration calorimetry (ITC), and Cd K-edge EXAFS spectroscopy were applied to investigate the binding characteristics of Cd on montmorillonite(Mont)-humic acid(HA)-bacteria composites. Additive sorption and non-additive Cd(II) sorption behaviour is observed for the binary Mont-bacteria and ternary Mont-HA-bacteria composite, respectively. Specifically, in the ternary composite, the coexistence of HA and bacteria inhibits Cd adsorption, suggesting a “blocking effect” between humic acid and bacterial cells. Large positive entropies (68.1 ~ 114.4 J/mol/K), and linear combination fitting of the EXAFS spectra for Cd adsorbed onto Mont-bacteria and Mont-HA-bacteria composites, demonstrate that Cd is mostly bound to bacterial surface functional groups by forming inner-sphere complexes. All our results together support the assertion that there is a degree of site masking in the ternary clay mineral-humic acid-bacteria composite. Because of this, in the ternary composite, Cd preferentially binds to the higher affinity components-i.e., the bacteria. PMID:26792640

  18. Uranium Adsorption on Ferrihydrite - Effects of Phosphate and Humic Acid

    USGS Publications Warehouse

    Payne, T.E.; Davis, J.A.; Waite, T.D.

    1996-01-01

    Uranium adsorption on ferrihydrite was studied as a function of pH in systems equilibrated with air, in the presence and absence of added phosphate and humic acid (HA). The objective was to determine the influence of PO43- and HA on uranium uptake. Below pH 7, the sorption of UO22+ typically increases with increasing pH (the 'low pH sorption edge'), with a sharp decrease in sorption above this pH value (the 'high pH edge'). The presence of ??PO43- of 10-4 mol/L moved the low pH edge to the left by approximately 0.8 pH units. The PO43- was strongly bound by the ferrihydrite surface, and the increased uptake of U was attributed to the formation of ternary surface complexes involving both UO22+ and PO43-. The addition of HA (9 mg/L) increased U uptake at pH values below 7, with little effect at higher pH values. The positions of the pH edges were also affected by the ionic strength and total U content. These experiments show that sorption interactions involving PO43 and HA must be considered in order to model the behavior of U in natural systems, in which these components are often present.

  19. Dissimilatory reduction and transformation of ferrihydrite-humic acid coprecipitates.

    PubMed

    Shimizu, Masayuki; Zhou, Jihai; Schröder, Christian; Obst, Martin; Kappler, Andreas; Borch, Thomas

    2013-01-01

    Organic matter (OM) is present in most terrestrial environments and is often found coprecipitated with ferrihydrite (Fh). Sorption or coprecipitation of OM with Fe oxides has been proposed to be an important mechanism for long-term C preservation. However, little is known about the impact of coprecipitated OM on reductive dissolution and transformation of Fe(III) (oxyhydr)oxides. Thus, we study the effect of humic acid (HA) coprecipitation on Fh reduction and secondary mineral formation by the dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens strain CN32. Despite similar crystal structure for all coprecipitates investigated, resembling 2-line Fh, the presence of coprecipitated HA resulted in lower specific surface areas. In terms of reactivity, coprecipitated HA resulted in slower Fh bioreduction rates at low C/Fe ratios (i.e., C/Fe ≤ 0.8), while high C/Fe ratios (i.e., C/Fe ≥ 1.8) enhanced the extent of bioreduction compared to pure Fh. The coprecipitated HA also altered the secondary Fe mineralization pathway by inhibiting goethite formation, reducing the amount of magnetite formation, and increasing the formation of a green rust-like phase. This study indicates that coprecipitated OM may influence the rates, pathway, and mineralogy of biogeochemical Fe cycling and anaerobic Fe respiration within soils.

  20. Fractionation of humic acids upon adsorption on montmorillonite and palygorskite

    NASA Astrophysics Data System (ADS)

    Alekseeva, T. V.; Zolotareva, B. N.

    2013-06-01

    The adsorption of three humic acid (HA) preparations by clays—montmorillonite (Wyoming, USA) and palygorskite (Kolomenskoe district, Moscow oblast)—has been studied. The HA preparations were isolated from samples of the humus-accumulative horizons of a leached chernozem (Voronezh) and a chestnut soil (Volgograd), and a commercial preparation of sodium humate (Aldrich) was also used. The solid-state 13C NMR spectroscopy and IR spectroscopy revealed the selective adsorption of structural HA fragments (alkyls, O-alkyls (carbohydrates), and acetal groups) on these minerals. As a result, the aromaticity of the organic matter (OM) in the organic-mineral complexes (OMCs) and the degree of its humification have been found to be lower compared to the original HA preparations. The fractionation of HAs is controlled by the properties of the mineral surfaces. The predominant enrichment of OMCs with alkyls has been observed for montmorillonite, as well as an enrichment with O-alkyls (carbohydrates) for palygorskite. A decrease in the C : N ratio has been noted in the elemental composition of the OM in complexes, which reflected its more aromatic nature and (or) predominant sorption of N-containing structural components of HA molecules. The adsorption of HA preparations by montmorillonite predominantly occurs on the external surface of mineral particles, and the interaction of nonpolar alkyl groups of HAs with this mineral belongs to weak (van der Waals, hydrophobic) interactions. The adsorption of HA preparations by palygorskite is at least partly of chemical nature: Si-OH groups of minerals are involved in the adsorption process. The formation of strong bonds between the OM and palygorskite explains the long-term (over 300 million years) retention of fossil fulvate-type OM in its complex with palygorskite, which we revealed previously.

  1. [Effect of lignite humic acid on soil ammonia oxidizing archaea community].

    PubMed

    Dong, Lianhua; Li, Baozhen; Yuan, Hongli; Scow, Kate M

    2010-06-01

    To illuminate the impact of humic acid (HA) on soil ammonia oxidizing archaea and then reveal the effect of HA on soil nitrogen cycle. Two humic acids (cHA and bHA) were added into the soil amended with urea. Community changes of ammonia oxidizing archaea (AOA) and total archaea were studied with terminal restricted fragment length polymorphism (T-RFLP) and real time PCR in the microcosm experiment. We found that the AOA population size increased significantly and AOA community changed greatly in the urea only treatment. However, HA could inhibit the increase of AOA population, moreover, HA could buffer the change in AOA community showed by canonical correspondence analysis (CCA) result. On the other hand, the total archaeal population decreased significantly in the urea only treatment, but stabilized in the urea with HA treatments, which indicated HA could eliminate the toxicity of urea to total archaea. CCA results showed that incubation time was the most important factor for the total archaeal community, and partial CCA (pCCA, when time as a covariable) result demonstrated that cHA was the most important environmental variable for total archaeal community. These results showed that HA diminished ammonia loss by inhibiting the increase of AOA competing with plant for ammonia, thus HA can increase the urea efficiency.

  2. Transport of Organic Compounds Through Porous Systems Containing Humic Acids.

    PubMed

    Smilek, Jiri; Sedlacek, Petr; Lastuvkova, Marcela; Kalina, Michal; Klucakova, Martina

    2017-03-01

    Soil pollution by the presence of different contaminants (e.g. heavy metal ions or pesticides) is one of the biggest problems worldwide. The positive affinity of natural humic acids towards these contaminants might contribute to the soil and ground water protection; therefore it is necessary to study the reactivity and barrier properties of humic acids. An original reactivity-mapping tool based on diffusion techniques designed to study the reactivity and barrier properties of polyelectrolytes was developed and tested on humic acids. The results of diffusion experiments demonstrate that the electrostatic interactions between humic acids functioning as a polyelectrolyte interpenetrated in a supporting hydrogel matrix (agarose) and cationic dye (methylene blue) as a model solute have a crucial impact on the rate of diffusion processes and on the barrier properties of hydrogels. The intensity of interactions was evaluated by fundamental diffusion parameters (effective diffusion coefficients and breakthrough time). The impact of modification of humic acids was also studied by means of diffusion experiments conducted on two types of standard humic acids (Leonardite 1S104H) and humic acids with selectively methylated carboxylic groups.

  3. The relationship between dissolved humic acids and soluble iron in estuaries

    NASA Technical Reports Server (NTRS)

    Fox, L. E.

    1984-01-01

    Dissolved humic acid and soluble iron appear to be chemically unassociated in estuaries despite their coincident removal. This conclusion is supported by differences in the aggregation kinetics of soluble iron and dissolved humic acid, the inability of extracted humic acid to stabilize laboratory preparations of ferric hydroxide, and decreasing ratios of humic acid carbon to soluble iron along the axes of some estuaries.

  4. Influence of humic acid on adsorption of Hg(II) by vermiculite.

    PubMed

    do Nascimento, Fernando Henrique; Masini, Jorge Cesar

    2014-10-01

    Geochemical mobility of Hg(II) species is strongly affected by the interactions of these compounds with naturally occurring adsorbents such as humic acids, clay minerals, oxides, etc. Interactions among these sorbents affect their affinity for Hg(II) and a full understanding of these processes is still lacking. The present work describes the influence of a humic acid (HA) sample on the adsorption of Hg(II) by vermiculite (VT). Adsorption isotherms were constructed to evaluate the affinity of Hg(II) by VT, HA, VT modified with humic acid (VT-HA), and VT-HA in presence of soluble humic acid (VT-HA + HA). All experiments were made at pH 6.0 ± 0.1 in 0.02 M NaNO3 and 25.0 ± 0.5 °C for initial Hg(II) concentrations from 1.0 to 100 μM. Determinations of Hg(II) were made by square wave voltammetry automated by sequential injection analysis, an approach that enables the determination of the free plus labile fractions of Hg(II) in HA suspensions without the need for laborious separation steps. The adsorption isotherms were fitted to Langmuir and Freundlich equations, showing that HA was the material with the higher adsorption capacity (537 ± 30 μmol g(-1)) in comparison with VT and VT-HA (44 ± 3 and 51 ± 11 μmol g(-1), respectively). Adsorption order was HA > VT-HA + HA > VT = VT-HA. At pH 6.0 the interaction of HA with VT is weak and only 14% of C initially added to the suspension was effectively retained by the mineral. Desorption of Hg(II) in acidic medium (0.05 M HCl) was higher in binary (VT-HA) and ternary (VT-HA + HA) systems in comparison with that of VT and HA alone, suggesting that interactions between VT and HA are facilitated in acidic medium, weakening the binding to Hg(II). Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Removal of humic acid from aqueous solution using dual PMMA/PVDF composite nanofiber: kinetics study

    NASA Astrophysics Data System (ADS)

    Zulfikar, M. A.; Afrianingsih, I.; Bahri, A.; Nasir, M.; Alni, A.; Setiyanto, H.

    2018-05-01

    The removal of humic acid from aqueous solution using dual poly(methyl methacrylate)/polyvinyl difluoride composite nanofiber under the influence of concentration has been studied. The experiments were performed using humic acid (HA) as an adsorbate at concentration in the range of 50-200 mg/L. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to describe the kinetic data and the rate constants were evaluated. It was observed that the amount of humic acid removed decrease with increasing concentration. The kinetic study revealed that pseudo-second order model fitted well the kinetic data, while the external diffusion or boundary layer diffusion was the main rate determining step in the removal process.

  6. Investigation of adsorptive fractionation of humic acid on graphene oxide using fluorescence EEM-PARAFAC.

    PubMed

    Lee, Bo-Mi; Seo, Young-Soo; Hur, Jin

    2015-04-15

    In this study, the adsorptive fractionation of a humic acid (HA, Elliott soil humic acid) on graphene oxide (GO) was examined at pH 4 and 6 using absorption spectroscopy and fluorescence excitation-emission matrix (EEM)-parallel factor analysis (PARAFAC). The extent of the adsorption was greater at pH 4.0 than at pH 6.0. Aromatic molecules within the HA were preferentially adsorbed onto the GO surface, and the preferential adsorption was more pronounced at pH 6, which is above the zero point of charge of GO. A relative ratio of two PARAFAC humic-like components (ex/em maxima at 270/510 nm and at (250, 265)/440 nm) presented an increasing trend with larger sizes of ultrafiltered humic acid fractions, suggesting the potential for using fluorescence EEM-PARAFAC for tracking the changes in molecular sizes of aromatic HA molecules. The individual adsorption behaviors of the two humic-like components revealed that larger sized aromatic components within HA had a higher adsorption affinity and more nonlinear isotherms compared to smaller sized fractions. Our results demonstrated that adsorptive fractionation of HA occurred on the GO surface with respect to their aromaticity and the sizes, but the degree was highly dependent on solution pH as well as the amount of adsorbed HS (or available surface sites). The observed adsorption behaviors were reasonably explained by a combination of different mechanisms previously suggested. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Micro-organization of humic acids in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Klučáková, Martina; Věžníková, Kateřina

    2017-09-01

    The methods of dynamic light scattering and micro-rheology were used to investigate the molecular organization of humic acids in solutions. The obtained results were supplemented by ultraviolet/visible spectrometry and measurement of the zeta potential. Particle tracking micro-rheology was used for the first time as a novel method in humic research. Solutions of humic acids were prepared in three different mediums: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. The molecular organization of humic acids was studied over a wide concentration range (0.01-10 g dm-3). Two breaks were detected in the obtained concentration dependencies. The rearrangements were observed at concentrations around 0.02 g dm-3 and 1 g dm-3. Changes in the measured values observed at around 0.02 g dm-3 were less noticeable and were related to the formation of particles between 100 and 1000 nm in size and the strong bimodal character of humic systems diluted by NaCl. The ;switch-over point; at around 1 g dm-3 indicated changes in the secondary structure of humic acids connected with the increase in colloidal stability (decrease of zeta potential), the decrease in polydispersity, and minimal values of viscosity.

  8. Adsorption of humic acids and trace metals in natural waters

    NASA Technical Reports Server (NTRS)

    Leung, W. H.

    1982-01-01

    Studies concerning the interactions between suspended hydrous iron oxide and dissolved humic acids and trace metals are reported. As a major component of dissolved organic matters and its readiness for adsorption at the solid/water interface, humic acids may play a very important role in the organometallic geochemistry of suspended sediments and in determining the fate and distribution of trace metals, pesticides and anions in natural water systems. Most of the solid phases in natural waters contain oxides and hydroxides. The most simple promising theory to describe the interactions of hydrous iron oxide interface is the surface complex formation model. In this model, the adsorptions of humic acids on hydrous iron oxide may be interpreted as complex formation of the organic bases (humic acid oxyanions) with surface Fe ions. Measurements on adsorptions were made in both fresh water and seawater. Attempts have been made to fit our data to Langmuir adsorption isotherm. Adsorption equilibrium constants were determined.

  9. Effect of humic acids on intestinal viscosity, leaky gut and ammonia excretion in a 24 h feed restriction model to induce intestinal permeability in broiler chickens

    USDA-ARS?s Scientific Manuscript database

    Humic acids (HA) are produced by biodegradation of organic matter that involves physical, chemical and microbiological processes, hence, HA are a complex mixture of many different acids containing carboxyl and phenolate groups. The purpose of this study was to evaluate the effect of HA on intestina...

  10. Humic Acid-Oxidizing, Nitrate-Reducing Bacteria in Agricultural Soils

    PubMed Central

    Van Trump, J. Ian; Wrighton, Kelly C.; Thrash, J. Cameron; Weber, Karrie A.; Andersen, Gary L.; Coates, John D.

    2011-01-01

    ABSTRACT This study demonstrates the prevalence, phylogenetic diversity, and physiology of nitrate-reducing microorganisms capable of utilizing reduced humic acids (HA) as electron donors in agricultural soils. Most probable number (MPN) enumeration of agricultural soils revealed large populations (104 to 106 cells g−1 soil) of microorganisms capable of reducing nitrate while oxidizing the reduced HA analog 2,6-anthrahydroquinone disulfonate (AH2DS) to its corresponding quinone. Nitrate-dependent HA-oxidizing organisms isolated from agricultural soils were phylogenetically diverse and included members of the Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. Advective up-flow columns inoculated with corn plot soil and amended with reduced HA and nitrate supported both HA oxidation and enhanced nitrate reduction relative to no-donor or oxidized HA controls. The additional electron donating capacity of reduced HA could reasonably be attributed to the oxidation of reduced functional groups. Subsequent 16S rRNA gene-based high-density oligonucleotide microarray (PhyloChip) indicated that reduced HA columns supported the development of a bacterial community enriched with members of the Acidobacteria, Firmicutes, and Betaproteobacteria relative to the no-donor control and initial inoculum. This study identifies a previously unrecognized role for HA in stimulating denitrification processes in saturated soil systems. Furthermore, this study indicates that reduced humic acids impact soil geochemistry and the indigenous bacterial community composition. PMID:21750120

  11. Fluorescence Quenching of Humic Acid by Coated Metallic Silver Particles.

    PubMed

    Zhu, Guocheng; Yin, Jun

    2017-07-01

    Natural organic matter is an important component of the aquatic environments, which has attracted wide attention to its influence of interaction with other pollutants. The present work aimed to investigate its fluorescence quenching (FQ) by coated metallic silver particles (AgNPs). In this work, using fluorescence spectroscopy in conjunction with UV-Vis spectroscopy and dynamic light scattering, the effect of coated AgNPs on fluorescence quenching intensity (FQI) of humic acid (HA) was assessed. In addition, the influence of electrolytes (NaCl, NaNO 3 and CaNO 3 ) in the FQI was observed. Results showed that with AgNPs dosage increased (>1.17X10 -3  mM), fluorescence quantum yield of HA gradually decreased, which implies that the FQ occurred. Furher observation showed that the FQ process followed both first-order and second-order Stern-Volmer functions. The FQ process was affected by the electrolytes: NaCl had an effect on reduction of FQI, possibly resulting from dissolution of AgNPs; Both of NaNO 3 and Ca(NO 3 ) 2 had an effect on the FQ of HA but Ca(NO 3 ) 2 presented greater degree. As a result, the FQ degree of HA by alone electrolyte was listed in descent order as Ca(NO 3 ) 2  > NaNO 3  > NaCl, which also implies the subsequent experimental results, indicating the FQ degree of HA by mutual electrolytes as Ca(NO 3 ) 2  + NaNO 3  > Ca(NO 3 ) 2  + NaCl > NaNO 3  + NaCl.

  12. Potentiometric titration and equivalent weight of humic acid

    USGS Publications Warehouse

    Pommer, A.M.; Breger, I.A.

    1960-01-01

    The "acid nature" of humic acid has been controversial for many years. Some investigators claim that humic acid is a true weak acid, while others feel that its behaviour during potentiometric titration can be accounted for by colloidal adsorption of hydrogen ions. The acid character of humic acid has been reinvestigated using newly-derived relationships for the titration of weak acids with strong base. Re-interpreting the potentiometric titration data published by Thiele and Kettner in 1953, it was found that Merck humic acid behaves as a weak polyelectrolytic acid having an equivalent weight of 150, a pKa of 6.8 to 7.0, and a titration exponent of about 4.8. Interdretation of similar data pertaining to the titration of phenol-formaldehyde and pyrogallol-formaldehyde resins, considered to be analogs for humic acid by Thiele and Kettner, leads to the conclusion that it is not possible to differentiate between adsorption and acid-base reaction for these substances. ?? 1960.

  13. Humic Acid Reduction by Propionibacterium freudenreichii and Other Fermenting Bacteria

    PubMed Central

    Benz, Marcus; Schink, Bernhard; Brune, Andreas

    1998-01-01

    Iron-reducing bacteria have been reported to reduce humic acids and low-molecular-weight quinones with electrons from acetate or hydrogen oxidation. Due to the rapid chemical reaction of amorphous ferric iron with the reduced reaction products, humic acids and low-molecular-weight redox mediators may play an important role in biological iron reduction. Since many anaerobic bacteria that are not able to reduce amorphous ferric iron directly are known to transfer electrons to other external acceptors, such as ferricyanide, 2,6-anthraquinone disulfonate (AQDS), or molecular oxygen, we tested several physiologically different species of fermenting bacteria to determine their abilities to reduce humic acids. Propionibacterium freudenreichii, Lactococcus lactis, and Enterococcus cecorum all shifted their fermentation patterns towards more oxidized products when humic acids were present; P. freudenreichii even oxidized propionate to acetate under these conditions. When amorphous ferric iron was added to reoxidize the electron acceptor, humic acids were found to be equally effective when they were added in substoichiometric amounts. These findings indicate that in addition to iron-reducing bacteria, fermenting bacteria are also capable of channeling electrons from anaerobic oxidations via humic acids towards iron reduction. This information needs to be considered in future studies of electron flow in soils and sediments. PMID:9797315

  14. Acid-base properties of humic and fulvic acids formed during composting.

    PubMed

    Plaza, César; Senesi, Nicola; Polo, Alfredo; Brunetti, Gennaro

    2005-09-15

    The soil acid-base buffering capacity and the biological availability, mobilization, and transport of macro- and micronutrients, toxic metal ions, and xenobiotic organic cations in soil are strongly influenced by the acid-base properties of humic substances, of which humic and fulvic acids are the major fractions. For these reasons, the proton binding behavior of the humic acid-like (HA) and fulvic acid-like (FA) fractions contained in a compost are believed to be instrumental in its successful performance in soil. In this work, the acid-base properties of the HAs and FAs isolated from a mixture of the sludge residue obtained from olive oil mill wastewater (OMW) evaporated in an open-air pond and tree cuttings (TC) at different stages of composting were investigated by a current potentiometric titration method and the nonideal competitive adsorption (NICA)-Donnan model. The NICA-Donnan model provided an excellent description of the acid-base titration data, and pointed out substantial differences in site density and proton-binding affinity between the HAs and FAs examined. With respect to FAs, HAs were characterized by a smaller content of carboxylic- and phenolic-type groups and their larger affinities for proton binding. Further, HAs featured a greater heterogeneity in carboxylic-type groups than FAs. The composting process increased the content and decreased the proton affinity of carboxylic- and phenolic-type groups of HAs and FAs, and increased the heterogeneity of phenolic-type groups of HAs. As a whole, these effects indicated that the composting process could produce HA and FA fractions with greater cation binding capacities. These results suggest that composting of organic materials improves their agronomic and environmental value by increasing their potential to retain and exchange macro- and micronutrients, and to reduce the bioavailability of organic and inorganic pollutants.

  15. Environmental conditions that influence the ability of humic acids to induce permeability in model biomembranes.

    PubMed

    Ojwang', Loice M; Cook, Robert L

    2013-08-06

    The interaction of humic acids (HAs) with 1-palmitoyl-2-oleoyl-Sn-glycero-3-phosphocholine (POPC) large unilamellar vesicle (LUV) model biomembrane system was studied by fluorescence spectroscopy. HAs from aquatic and terrestrial (including coal) sources were studied. The effects of HA concentration and temperature over environmentally relevant ranges of 0 to 20 mg C/L and 10 to 30 °C, respectively, were investigated. The dosage studies revealed that the aquatic Suwannee River humic acid (SRHA) causes an increased biomembrane perturbation (percent leakage of the fluorescent dye, Sulforhodamine B) over the entire studied concentration range. The two terrestrial HAs, namely Leonardite humic acid (LAHA) and Florida peat humic acid (FPHA), at concentrations above 5 mg C/L, show a decrease or a plateau effect attributable to the competition within the HA mixture and/or the formation of "partial aggregates". The temperature studies revealed that biomembrane perturbation increases with decreasing temperature for all three HAs. Kinetic studies showed that the membrane perturbation process is complex with both fast and slow absorption (sorption into the bilayer) components and that the slow component could be fitted by first order kinetics. A mechanism based on "lattice errors" within the POPC LUVs is put forward to explain the fast and slow components. A rationale behind the concentration and temperature findings is provided, and the environmental implications are discussed.

  16. Ozonization of polyfunctional and humic acids of sapropelites

    SciTech Connect

    Verkhodanova, N.N.; Myakina, I.A.; Egor'kov, A.N.

    Data are presented which show that in the ozonization of polyfunctional acids (PFAs) and humic acids (HAs) in glacial acetic acid, all the organic carbon can be converted into the soluble form. Mono- and dicarboxylic acids of normal structure have been detected in the ozonization products. 5 refs.

  17. Effect of Acid-Base Equilibrium on Absorption Spectra of Humic acid in the Presence of Copper Ions

    NASA Astrophysics Data System (ADS)

    Lavrik, N. L.; Mulloev, N. U.

    2014-03-01

    The reaction between humic acid (HA, sample IHSS) and a metal ion (Cu2+) that was manifested as absorption bands in the range 210-350 nm was recorded using absorption spectroscopy. The reaction was found to be more effective as the pH increased. These data were interpreted in the framework of generally accepted concepts about the influence of acid-base equilibrium on the dissociation of salts, according to which increasing the solution pH increases the concentration of HA anions. It was suggested that [HA-Cu2+] complexes formed.

  18. Effect of fulvic and humic acids on copper and zinc homeostasis in rats.

    PubMed

    Hullár, István; Vucskits, András Valentin; Berta, Erzsébet; Andrásofszky, Emese; Bersényi, András; Szabó, József

    2018-03-01

    The objective of this study was to investigate the effects of fulvic acid (FA) and humic acid (HA), the two main compounds of humic substances (HSs), on copper (Cu) and zinc (Zn) homeostasis. Seventy-two male Wistar rats were randomly divided into nine experimental groups. The control diet (AIN-93G formula) and the diets supplemented with 0.1%, 0.2%, 0.4% and 0.8% FA or HA were fed for 26 days. Cu and Zn concentrations of the large intestinal content (LIC), liver, kidney, femur and hair were determined. FA and HA did not influence significantly the Cu or Zn contents of the experimental diets, the rats' feed intake, weight gain and the feed to gain ratio. Both FA and HA decreased the Cu concentrations of the LIC significantly and in a dose-related manner; however the absorption-stimulating effect of HA was more pronounced. FA increased the Cu content of the liver, but neither FA nor HA had a dose-dependent effect on it. FA or HA supplementations had no significant effect on the Cu concentration of the kidney. At the concentrations used, dietary FA or HA supplementations are not promising growth promoters. FA influences the Cu homeostasis unlike HA, because FA not only stimulates Cu absorption, but the extra quantity of absorbed Cu is retained in the organism. The stimulatory effect of HA on Zn absorption may not be manifested in Cu and Zn homeostasis, because of the tight connection of these microelements to FA and HA, which prevents the transmission of Zn from the ZnHA complex to the organs. As regards the effect of FA and HA on Cu and Zn homeostasis, both FA and HA stimulated the absorption of these microelements, but only FA increased the retention of Cu (in the liver) and Zn (in the kidney).

  19. [Effects of different fertilization treatments on soil humic acid structure characteristics].

    PubMed

    Zhao, Nan; Lü, Yi-Zhong

    2012-07-01

    The present article used soil humic acid as research object to study effects on the structure characteristics of soil humic acid under the condition of applying cake fertilizer, green manure, straw fertilizer with the same contents of nitrogen and phosphorus. It used element analysis, micro infrared, and solid 13C-NMR for structure analysis, the results indicated that: The chemical composition and structure characteristics of humic acids were similar, but they also had many obvious differences. (1) The atomic ratios of H/C, O/C, and C/N were all different for the humic acids, the soil humic acid of cake fertilizer processing had the highest contents of H and N, green manure processing of soil humic acid contained the highest content of O, while straw fertilizer processing of soil humic acid contained highest content of C. (2) Infrared analysis displayed that the three soil humic acids contained protein Cake fertilizer processing of soil humic acid contained the most amino compounds, green manure processing of soil humic acid contained the maximum contents of hydroxyl and aliphatic hydrocarbon, while straw fertilizer processing of soil humic acid contained the highest contents of alcohol and phenol. (3) Solid 13C-NMR data indicated that cake fertilizer processing of soil humic acid contained the most carboxyl carbon, green manure processing of soil humic acid contained the highest contents of alkyl carbon and carbonyl carbon, while straw fertilizer processing of soil humic acids had the most alkoxy carbon and aromatic carbon

  20. The effect of humic acid on uranyl sorption onto bentonite at trace uranium levels.

    PubMed

    Ivanov, Peter; Griffiths, Tamara; Bryan, Nick D; Bozhikov, Gospodin; Dmitriev, Serguei

    2012-11-01

    The effect of humic acid (HA) on U(VI) sorption on bentonite was studied in batch experiments at room temperature and ambient atmosphere at a (237)U(VI) concentration of 8.4 × 10(-11) M and HA concentration of 100 mg L(-1). The distribution of U(VI) between the liquid and solid phases was studied as a function of pH and ionic strength both in the absence and presence of HA. It was shown that the uranyl sorption on bentonite is strongly dependent on pH and the presence of humics, and the effect of the addition order was negligible. In the absence of HA an enhancement in the uptake with increasing pH was observed and a sharp sorption edge was found to take place between pH 3.2 and 4.2. The presence of HA slightly increases uranium(VI) sorption at low pH and curtails it at moderate pH, compared to the absence of HA. In the basic pH range for both the presence and absence of HA the sorption of uranium is significantly reduced, which could be attributed to the formation of soluble uranyl carbonate complexes. The influence of ionic strength on U(VI) and HA uptake by bentonite were investigated in the range of 0.01-1.0 M, and while there was an enhancement in the sorption of humic acid with increasing ionic strength, no significant effect of the ionic strength on the U(VI) sorption was observed in both the absence and presence of HA.

  1. Effects of humic acid concentration on the microbially-mediated reductive solubilization of Pu(IV) polymers.

    PubMed

    Xie, Jinchuan; Han, Xiaoyuan; Wang, Weixian; Zhou, Xiaohua; Lin, Jianfeng

    2017-10-05

    The role of humic acid concentration in the microbially-mediated reductive solubilization of Pu(IV) polymers remains unclear until now. The effects of humic concentration (0-150.5mg/L) on the rate and extent of reduction of polymeric Pu(IV) were studied under anaerobic and pH 7.2 conditions. The results show that Shewanella putrefaciens, secreting flavins as endogenous electron shuttles, cannot notably stimulate the reduction of polymeric Pu(IV). In the presence of humic acids, the reduction rate of polymeric Pu(IV) increased with increasing humic concentrations (0-15.0mg/L): e.g., a 102-fold increase from 4.1×10 -15 (HA=0) to 4.2×10 -13 mol Pu(III) aq /h (HA=15.0mg/L). The bioreduced humic acids by S. putrefaciens facilitated the extracellular electron transfer to Pu(IV) polymers and thus the reduction of polymeric Pu(IV) to Pu(III) aq became thermodynamically favorable. However, the reduction rate did not increase but decrease with increasing humic concentrations from 15.0 to 150.5mg/L. Humic coatings formed on the polymer surfaces at relatively high humic concentrations limited the electron transfer to the polymers and thus decreased the reduction rate. The finding of the dynamic role of humic acids in the bioreductive solubilization may be helpful in evaluating Pu mobility in the geosphere. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Bioremoval of humic acid from water by white rot fungi: exploring the removal mechanisms.

    PubMed

    Zahmatkesh, M; Spanjers, H; Toran, M J; Blánquez, P; van Lier, J B

    2016-12-01

    Twelve white rot fungi (WRF) strains were screened on agar plates for their ability to bleach humic acid (HA). Four fungal strains were selected and tested in liquid media for removal of HA. Bioremediation was investigated by HA color removal and changes in the concentration and molecular size distribution of HA by size exclusion chromatography. Trametes versicolor and Phanerochaete chrysosporium showed the highest HA removal efficiency, reaching about 80%. Laccase and manganese peroxidase were measured as extracellular enzymes and their relation to the HA removal by WRF was investigated. Results indicated that nitrogen limitation could enhance the WRF extracellular enzyme activity, but did not necessarily increase the HA removal by WRF. The mechanism of bioremediation by WRF was shown to involve biosorption of HA by fungal biomass and degradation of HA to smaller molecules. Also, contradicting previous reports, it was shown that the decolorization of HA by WRF could not necessarily be interpreted as degradation of HA. Biosorption experiments revealed that HA removal by fungal biomass is dependent not only on the amount of biomass as the sorbent, but also on the fungal species. The involvement of cytochrome P450 (CYP) enzymes was confirmed by comparing the HA removal capability of fungi with and without the presence of a CYP inhibitor. The ability of purified laccase from WRF to solely degrade HA was proven and the importance of mediators was also demonstrated.

  3. Optical properties of selected components of mineral dust aerosol processed with organic acids and humic material

    NASA Astrophysics Data System (ADS)

    Alexander, Jennifer M.; Grassian, V. H.; Young, M. A.; Kleiber, P. D.

    2015-03-01

    Visible light scattering phase function and linear polarization profiles of mineral dust components processed with organic acids and humic material are measured, and results are compared to T-matrix simulations of the scattering properties. Processed samples include quartz mixed with humic material, and calcite reacted with acetic and oxalic acids. Clear differences in light scattering properties are observed for all three processed samples when compared to the unprocessed dust or organic salt products. Results for quartz processed with humic acid sodium salt (NaHA) indicate the presence of both internally mixed quartz-NaHA particles and externally mixed NaHA aerosol. Simulations of light scattering suggest that the processed quartz particles become more moderate in shape due to the formation of a coating of humic material over the mineral core. Experimental results for calcite reacted with acetic acid are consistent with an external mixture of calcite and the reaction product, calcium acetate. Modeling of the light scattering properties does not require any significant change to the calcite particle shape distribution although morphology changes cannot be ruled out by our data. It is expected that calcite reacted with oxalic acid will produce internally mixed particles of calcite and calcium oxalate due to the low solubility of the product salt. However, simulations of the scattering for the calcite-oxalic acid system result in rather poor fits to the data when compared to the other samples. The poor fit provides a less accurate picture of the impact of processing in the calcite-oxalic acid system.

  4. H-binding of size- and polarity-fractionated soil and lignite humic acids after removal of metal and ash components

    USGS Publications Warehouse

    Drosos, Marios; Leenheer, Jerry A.; Avgeropoulos, Apostolos; Deligiannakis, Yiannis

    2014-01-01

    A fractionation technique, combining dialysis removal of metal and ash components with hydrofluoric acid and pH 10 citrate buffer followed by chromatography of dialysis permeate on XAD-8 resin at decreasing pH values, has been applied to lignite humic acid (lignite-HA) and soil humic acid (soil-HA). H-binding data and non ideal competitive adsorption-Donnan model parameters were obtained for the HA fractions by theoretical analysis of H-binding data which reveal a significant increase of the carboxyl and the phenolic charge for the lignite-HA fractions vs. the parental lignite humic acid (LParentalHA). The fractionated lignite-HA material consisted mainly of permeate fractions, some of which were fulvic acid-like. The fractionated soil-HA material consisted mainly of large macromolecular structures that did not permeate the dialysis membrane during deashing. Chargeable groups had comparable concentrations in soil-HA fractions and parental soil humic acid (SParentalHA), indicating minimal interference of ash components with carboxyl and phenolic (and/or enolic) groups. Fractionation of HA, combined with theoretical analysis of H-binding, can distinguish the supramolecular vs. macromolecular nature of fractions within the same parental HA.

  5. H-binding of size- and polarity-fractionated soil and lignite humic acids after removal of metal and ash components.

    PubMed

    Drosos, Marios; Leenheer, Jerry A; Avgeropoulos, Apostolos; Deligiannakis, Yiannis

    2014-03-01

    A fractionation technique, combining dialysis removal of metal and ash components with hydrofluoric acid and pH 10 citrate buffer followed by chromatography of dialysis permeate on XAD-8 resin at decreasing pH values, has been applied to lignite humic acid (lignite-HA) and soil humic acid (soil-HA). H-binding data and non ideal competitive adsorption-Donnan model parameters were obtained for the HA fractions by theoretical analysis of H-binding data which reveal a significant increase of the carboxyl and the phenolic charge for the lignite-HA fractions vs. the parental lignite humic acid (LParentalHA). The fractionated lignite-HA material consisted mainly of permeate fractions, some of which were fulvic acid-like. The fractionated soil-HA material consisted mainly of large macromolecular structures that did not permeate the dialysis membrane during deashing. Chargeable groups had comparable concentrations in soil-HA fractions and parental soil humic acid (SParentalHA), indicating minimal interference of ash components with carboxyl and phenolic (and/or enolic) groups. Fractionation of HA, combined with theoretical analysis of H-binding, can distinguish the supramolecular vs. macromolecular nature of fractions within the same parental HA.

  6. Influence of humic acid on the stability and bacterial toxicity of zinc oxide nanoparticles in water.

    PubMed

    Akhil, K; Chandran, Preethy; Sudheer Khan, S

    2015-12-01

    The present study investigated the stability of zinc oxide nanoparticles (ZnO NPs) by the adsorption of humic acid (HA) and the mechanism of adsorption. The effect of humic acid on NP toxicity was determined by Escherichia coli (ATCC 13534), E. coli (ATCC 25922), and Pseudomonas putida (MTCC 4910). The nanoparticles showed low zeta potential and were least stable in the absence of HA. However, the negative surface charge of the particles increased in the presence of HA (0-50mg/L) that reduced the propensity of nanoparticles to aggregate in water. A decrease in absorbance of ZnO NPs at 375 nm (plasmon peak) was noted in the presence of HA by UV-visible spectrophotometric analysis. A blue shift towards 370 nm was noted when the concentration of HA was above 20mg/L. The HA adsorbed ZnO NPs showed higher zeta potential (>-30 mV) and were highly stable. HA reduced the photocatalytic activity of ZnO and at the same time increased the photostability of ZnO. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Simultaneous biodegradation of phenol and carbon tetrachloride mediated by humic acids.

    PubMed

    Martínez, Claudia M; Alvarez, Luis H; Cervantes, Francisco J

    2012-09-01

    The capacity of an anaerobic sediment to achieve the simultaneous biodegradation of phenol and carbon tetrachloride (CT) was evaluated, using humic acids (HA) as redox mediator. The presence of HA in sediment incubations increased the rate of biodegradation of phenol and the rate of dehalogenation (2.5-fold) of CT compared to controls lacking HA. Further experiments revealed that the electron-accepting capacity of HA derived from different organic-rich environments was not associated with their reducing capacity to achieve CT dechlorination. The collected kinetic data suggest that the reduction of CT by reduced HA was the rate-limiting step during the simultaneous biodegradation of phenol and CT. To our knowledge, the present study constitutes the first demonstration of the simultaneous biodegradation of two priority pollutants mediated by HA.

  8. Effect of Lime, Humic Acid and Moisture Regime on the Availability of Zinc in Alfisol

    PubMed Central

    Naik, Sushanta Kumar; Das, Dilip Kumar

    2007-01-01

    Lime and humic acid application can play an important role in the availability of zinc in paddy soils. We conducted laboratory incubation experiments on a rice growing soil (Alfisol) to determine the effect of lime, humic acid and different moisture regimes on the availability of Zn. Addition of half doses of liming material (powdered lime stone) recorded highest values of DTPA-Zn followed by no lime and 100% of lime requirement throughout the incubation period. With the progress of incubation, DTPA-Zn increased slightly during the first week and then decreased thereafter. The highest DTPA-extractable Zn content of 2.85 mg/kg was found in the treatment Zn10 L1/2 at 7 days of incubation, showing 17.3 % increase in DTPA-Zn content over its corresponding treatment of Zn alone (Zn10L0). The DTPA-Zn concentration increased with the application of humic acid compared with no humic acid throughout 35 days of the incubation period and the peak value obtained was 3.12 mg/kg in the treatment Zn10 HA2 at 14 days after incubation, showing 50 % increase in Zn content over its corresponding treatment of Zn alone (Zn10HA0). The application of 0.2% humic acid compared with 0.1% resulted in greater increase in DTPA-Zn concentration in soil application. During the 35 days of incubation, highest values of DTPA-Zn were recorded in soil maintained at saturated compared to water logged conditions. However, under alternate wetting and drying condition the DTPA-Zn content gradually decreased up to 21 days and thereafter increased slowly. PMID:17704853

  9. Evaluation of methods of determining humic acids in nucleic acid samples for molecular biological analysis.

    PubMed

    Wang, Yong; Fujii, Takeshi

    2011-01-01

    It is important in molecular biological analyses to evaluate contamination of co-extracted humic acids in DNA/RNA extracted from soil. We compared the sensitivity of various methods for measurement of humic acids, and influences of DNA/RNA and proteins on the measurement. Considering the results, we give suggestions as to choice of methods for measurement of humic acids in molecular biological analyses.

  10. Humic Acid Complexation of Th, Hf and Zr in Ligand Competition Experiments: Metal Loading and Ph Effects

    NASA Technical Reports Server (NTRS)

    Stern, Jennifer C.; Foustoukos, Dionysis I.; Sonke, Jeroen E.; Salters, Vincent J. M.

    2014-01-01

    The mobility of metals in soils and subsurface aquifers is strongly affected by sorption and complexation with dissolved organic matter, oxyhydroxides, clay minerals, and inorganic ligands. Humic substances (HS) are organic macromolecules with functional groups that have a strong affinity for binding metals, such as actinides. Thorium, often studied as an analog for tetravalent actinides, has also been shown to strongly associate with dissolved and colloidal HS in natural waters. The effects of HS on the mobilization dynamics of actinides are of particular interest in risk assessment of nuclear waste repositories. Here, we present conditional equilibrium binding constants (Kc, MHA) of thorium, hafnium, and zirconium-humic acid complexes from ligand competition experiments using capillary electrophoresis coupled with ICP-MS (CE- ICP-MS). Equilibrium dialysis ligand exchange (EDLE) experiments using size exclusion via a 1000 Damembrane were also performed to validate the CE-ICP-MS analysis. Experiments were performed at pH 3.5-7 with solutions containing one tetravalent metal (Th, Hf, or Zr), Elliot soil humic acid (EHA) or Pahokee peat humic acid (PHA), and EDTA. CE-ICP-MS and EDLE experiments yielded nearly identical binding constants for the metal- humic acid complexes, indicating that both methods are appropriate for examining metal speciation at conditions lower than neutral pH. We find that tetravalent metals form strong complexes with humic acids, with Kc, MHA several orders of magnitude above REE-humic complexes. Experiments were conducted at a range of dissolved HA concentrations to examine the effect of [HA]/[Th] molar ratio on Kc, MHA. At low metal loading conditions (i.e. elevated [HA]/[Th] ratios) the ThHA binding constant reached values that were not affected by the relative abundance of humic acid and thorium. The importance of [HA]/[Th] molar ratios on constraining the equilibrium of MHA complexation is apparent when our estimated Kc, MHA values

  11. Effects of filtration temperature, humic acid level and alum dose on cryptosporidium sized particle breakthrough.

    PubMed

    Xu, G R; Fitzpatrick, C S B; Deng, L Y

    2006-01-01

    Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and especially particle breakthrough. Understanding the causes of breakthrough is essential, as the parasite cannot be destroyed by conventional disinfection with chlorine. Particle breakthrough depends on many factors. This research aims to investigate the influence of temperature, humic acid (HA) level and chemical dosing on particle breakthrough in filtration. A series of temperatures were set at 5 degrees C, 15 degrees C and 25 degrees C; humic acid level was 5 mg L(-1). Each was combined with a series of Al doses. A laser particle counter was used to assess the particle breakthrough online. Turbidity, zeta potential, and UV254 absorption were measured before and after filtration. The results showed that particle breakthrough was influenced significantly by temperature, humic acid and dosing. Particle breakthrough occurred earlier at lower temperature, while at higher temperature it was reduced at the same coagulant dose. With coagulants, even at low dose, particle breakthrough was significantly reduced. With HA 5 mg L(-1), particle breakthrough was earlier and the amount was much larger than without HA even at high temperature. There was an optimal dose in filtration and it was well correlated with zeta potential.

  12. Two-dimensional correlation spectroscopic analysis on the interaction between humic acids and aluminum coagulant.

    PubMed

    Jin, Pengkang; Song, Jina; Wang, Xiaochang C; Jin, Xin

    2018-02-01

    In this study, two-dimensional correlation spectroscopy integrated with synchronous fluorescence and infrared absorption spectroscopy was employed to investigate the interaction between humic acids and aluminum coagulant at slightly acidic and neutral pH. Higher fluorescence quenching was produced for fulvic-like and humic-like fractions at pH5. At pH5, the humic-like fractions originating from the carboxylic acid, carboxyl and polysaccharide compounds were bound to aluminum first, followed by the fulvic-like fractions originating from the carboxyl and polysaccharide compounds. This finding also demonstrated that the activated functional groups of HA were involved in forming the Al-HA complex, which was accompanied by the removal of other groups by co-precipitation. Meanwhile, at pH7, almost no fluorescence quenching occurred, and surface complexation was observed to occur, in which the activated functional groups were absorbed on the amorphous Al(OH) 3 . Two-dimensional FT-IR correlation spectroscopy indicated the sequence of HA structural change during coagulation with aluminum, with IR bands affected in the order of COOH>COO - >NH deformation of amide II>aliphatic hydroxyl COH at pH5, and COO - >aliphatic hydroxyl COH at pH7. This study provides a promising pathway for analysis and insight into the priority of functional groups in the interaction between organic matters and metal coagulants. Copyright © 2017. Published by Elsevier B.V.

  13. PCE solubilization and mobilization by commercial humic acid

    NASA Astrophysics Data System (ADS)

    Johnson, William P.; John, W. Wynn

    1999-01-01

    In this paper, comparison is made of terms describing solubilization of hydrophobic organic compounds (HOC) by dissolved humic substances (DHS) and commercial non-ionic surfactants. This paper examines the ability of a commercial humic acid (Aldrich humic acid) to solubilize and mobilize tetrachlorothene (PCE) residual in porous media. The constant for solubilization of PCE by Aldrich humic acid is shown to be a factor of two to thirty times less than that published for dodecyl alcohol ethoxylate surfactants, showing that Aldrich humic acid is less capable than some non-ionic surfactants at solubilizing residual PCE. The depression of PCE-water interfacial tension in the presence of DHS is shown to be significantly less than published values for a non-ionic surfactant, and surfactant mixtures, indicating that the DHS used in this study is less prone to cause mobilization of non-aqueous phase liquids relative to surfactants. Several possible advantages of DHS use in the remediation of subsurface media contaminated with HOC are described, including the ability of DHS to solubilize HOC irrespective of the DHS concentration, and potential lesser tendency of DHS to depress the interfacial tension between non-aqueous phases and water relative to surfactants (an advantage when mobilization is undesired).

  14. Influence of cations on noncovalent interactions between 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and dissolved fulvic and humic acids.

    PubMed

    Gadad, Praveen; Nanny, Mark A

    2008-12-01

    The influence of cations (Na(+), Ca(2+) and Mg(2+)) on noncovalent interactions between 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and dissolved fulvic acids (FAs) (Norman landfill leachate fulvic acid (NLFA) and Suwannee River fulvic acid (SRFA)) and dissolved humic acids (HAs) (Suwannee River humic acid (SRHA) and Leonardite humic acid (LHA)) was examined using steady-state fluorescence spectroscopy at pH 4, 7 and 10 as a function of cation concentration (up to 25-100mM). Regardless of pH and cation concentration, PRODAN quenching by FA was unaffected by cations. However, interactions between PRODAN and HA decreased in the presence of cations at pH 7 and 10. Cation concentrations below the HA charge density resulted in the greatest decrease of PRODAN quenching, while very little additional decrease in PRODAN quenching occurred at cation concentrations above the HA charge density. This suggests that as the HA carboxylic acid functional groups form inner sphere complexes with divalent cations, intramolecular interactions result in a contraction of the HA molecular structure, thereby preventing PRODAN from associating with the condensed aromatic, electron accepting moieties inherent within HA molecules and responsible for PRODAN quenching. However, once the HA carboxylic acid functional groups are fully titrated with divalent cations, PRODAN quenching is no longer significantly influenced by the further addition of cations, even though these additional cations facilitate intermolecular interactions between the HA molecules to form supramolecular HA aggregates that can continue to increase in size. Regardless of FA and HA type, pH, cation type and concentration, the lack of blue-shifted fluorescence emission spectra indicated that micelle-like hydrophobic regions, amenable to PRODAN partitioning, were not formed by intra- and intermolecular interactions of FA and HA.

  15. Effect of humic acids on the adsorption of paraquat by goethite.

    PubMed

    Brigante, Maximiliano; Zanini, Graciela; Avena, Marcelo

    2010-12-15

    The adsorption of the herbicide paraquat (PQ(2+)) on goethite and on the binary system humic acid-goethite has been studied in batch experiments by performing adsorption isotherms under different conditions of pH, supporting electrolyte concentration and temperature. The results were completed with capillary electrophoresis (CE) in order to measure the binding isotherm between PQ(2+) and humic acid (HA) molecules in solution. PQ(2+) adsorption is negligible on the bare goethite surface but important on the HA-goethite adsorbent. In this last case, the adsorption increases by increasing pH and decreasing electrolyte concentration. There are no significant effects of temperature on the adsorption. The adsorption takes place by direct binding of PQ(2+) to adsorbed HA molecules leading to the formation of surface species of the type goethite-HA-PQ(2+). The results are consistent with a mechanism where PQ(2+) binds negatively charged groups of HA (carboxylates and phenolates) forming ionic pairs or outer-sphere complexes. Since goethite in nature usually contains adsorbed HA molecules, it may act as a good adsorbent for cationic herbicides. This will not only benefit the deactivation of the herbicides but also reduce their leaching and transport through groundwater. Copyright © 2010 Elsevier B.V. All rights reserved.

  16. On the acid-base properties of humic acid in soil.

    PubMed

    Cooke, James D; Hamilton-Taylor, John; Tipping, Edward

    2007-01-15

    Humic acid was isolated from three contrasting organic-rich soils and acid-base titrations performed over a range of ionic strengths. Results obtained were unlike most humic acid data sets; they showed a greater ionic strength dependency at low pH than at high pH. Forward- and back-titrations with the base and acid revealed hysteresis, particularly at low pH. Previous authors attributed this type of hysteresis to humic acid aggregates-created during the isolation procedure-being redissolved during titration as the pH increased and regarded the results as artificial. However, forward- and back-titrations with organic-rich soils also demonstrated a similar hysteretic behavior. These observations indicate (i) that titrations of humic acid in aggregated form (as opposed to the more usual dissolved form) are more representative of the acid-base properties of humic acid in soil and (ii) that the ionic strength dependency of proton binding in humic acid is related to its degree of aggregation. Thus, the current use of models based on data from dissolved humic substances to predictthe acid-base properties of humic acid in soil under environmental conditions may be flawed and could substantially overestimate their acid buffering capacity.

  17. Response of humic acid formation to elevated nitrate during chicken manure composting.

    PubMed

    Shi, Mingzi; Wei, Zimin; Wang, Liqin; Wu, Junqiu; Zhang, Duoying; Wei, Dan; Tang, Yu; Zhao, Yue

    2018-06-01

    Nitrate can stimulate microbes to degrade aromatic compounds, whereas humic acid (HA) as a high molecular weight aromatic compound, its formation may be affected by elevated nitrate during composting. Therefore, this study is conducted to determine the effect of elevated nitrate on HA formation. Five tests were executed by adding different nitrate concentrations to chicken manure composting. Results demonstrate that the concentration of HA in treatment group is significantly decreased compared with control group (p < 0.05), especially in the highest nitrate concentration group. RDA indicates that the microbes associated with HA and environmental parameters are influenced by elevated nitrate. Furthermore, structural equation model reveals that elevated nitrate reduces HA formation by mediating microbes directly, or by affecting ammonia and pH as the indirect drivers to regulate microbial community structure. Copyright © 2018 Elsevier Ltd. All rights reserved.

  18. Fluorescence analysis of humic and fulvic acids from two Brazilian oxisols as affected by biosolid amendment.

    PubMed

    Bertoncini, E I; D'Orazio, V; Senesi, N; Mattiazzo, M E

    2005-03-01

    Conventional monodimensional fluorescence spectroscopy in the emission, excitation, and synchronous-scan modes and total luminescence spectroscopy have proven to be sensitive techniques for characterization and differentiation of humic acid (HA) and fulvic acid (FA) fractions isolated from an aerobically and anaerobically digested and limed biosolid, two layers of a sandy and a clayey Brazilian oxisol, and the corresponding biosolid-amended soils. The spectral patterns and the relative fluorescence intensities suggest greater molecular heterogeneity, less aromatic polycondensation, and less humification of biosolid HA and FA compared with soil HA and FA. However, the differences are smaller for the FA fractions than for the HA fractions. Fluorescence properties of soil HA and FA differ slightly as a function of soil type and soil layer. Biosolid application causes a shift to shorter wavelengths of the main fluorescence peaks and marked variation of the relative fluorescence intensities of HA and FA isolated from amended soils. These results suggest that molecular components of relatively small molecular size, with a low level of aromatic polycondensation, and low degree of humification present in biosolid HA and FA are partially and variously incorporated into amended soil HA and FA. In general, these modifications seem to be smaller in HA and FA from the clayey soil layers than in those from the sandy soil layers, possibly because of protective effects exerted by clay minerals of native soil HA and FA against disturbances caused by biosolid application.

  19. Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Columns

    EPA Science Inventory

    The distinct effects of humic acid (HA, 0−10 mg L−1) on the transport of titanium dioxide (rutile) nanoparticles (nTiO2) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3−200 mM NaCl, pH 5.7 and 9.0). Specifically, the tra...

  20. Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Column

    EPA Science Inventory

    Distinct effects of humic acid (HA, 0 – 10 mg L-1) on the transport of titanium dioxide (rutile) nanoparticles (nTiO2) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3 – 200 mM NaCl, pH 5.7 and 9.0). Specifical...

  1. Spectral characterization of the fluorescent components present in humic substances, fulvic acid and humic acid mixed with pure benzo(a)pyrene solution.

    PubMed

    El Fallah, Rawa; Rouillon, Régis; Vouvé, Florence

    2018-06-15

    The fate of benzo(a)pyrene (BaP), a ubiquitous contaminant reported to be persistent in the environment, is largely controlled by its interactions with the soil organic matter. In the present study, the spectral characteristics of fluorophores present in the physical fractions of the soil organic matter were investigated in the presence of pure BaP solution. After extraction of humic substances (HSs), and their fractionation into fluvic acid (FA) and humic acid (HA), two fluorescent compounds (C 1 and C 2 ) were identified and characterized in each physical soil fraction, by means of fluorescence excitation-emission matrices (FEEMs) and Parallel Factor Analysis (PARAFAC). Then, to each type of fraction having similar DOC content, was added an increasing volume of pure BaP solution in attempt to assess the behavior of BaP with the fluorophores present in each one. The application of FEEMs-PARAFAC method validated a three-component model that consisted of the two resulted fluorophores from HSs, FA and HA (C 1 and C 2 ) and a BaP-like fluorophore (C 3 ). Spectral modifications were noted for components C 2 HSs (C 2 in humic substances fraction) (λex/λem: 420/490-520 nm), C 2 FA (C 2 in fulvic acid fraction) (λex/λem: 400/487(517) nm) and C 1 HA (C 1 in humic acid fraction) (λex/λem: 350/452(520) nm). We explored the impact of increasing the volume of the added pure BaP solution on the scores of the fluorophores present in the soil fractions. It was found that the scores of C 2 HSs, C 2 FA, and C 1 HA increased when the volume of the added pure BaP solution increased. Superposition of the excitation spectra of these fluorophores with the emission spectrum of BaP showed significant overlaps that might explain the observed interactions between BaP and the fluorescent compounds present in SOM physical fractions. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Spectral characterization of the fluorescent components present in humic substances, fulvic acid and humic acid mixed with pure benzo(a)pyrene solution

    NASA Astrophysics Data System (ADS)

    El Fallah, Rawa; Rouillon, Régis; Vouvé, Florence

    2018-06-01

    The fate of benzo(a)pyrene (BaP), a ubiquitous contaminant reported to be persistent in the environment, is largely controlled by its interactions with the soil organic matter. In the present study, the spectral characteristics of fluorophores present in the physical fractions of the soil organic matter were investigated in the presence of pure BaP solution. After extraction of humic substances (HSs), and their fractionation into fluvic acid (FA) and humic acid (HA), two fluorescent compounds (C1 and C2) were identified and characterized in each physical soil fraction, by means of fluorescence excitation-emission matrices (FEEMs) and Parallel Factor Analysis (PARAFAC). Then, to each type of fraction having similar DOC content, was added an increasing volume of pure BaP solution in attempt to assess the behavior of BaP with the fluorophores present in each one. The application of FEEMs-PARAFAC method validated a three-component model that consisted of the two resulted fluorophores from HSs, FA and HA (C1 and C2) and a BaP-like fluorophore (C3). Spectral modifications were noted for components C2HSs (C2 in humic substances fraction) (λex/λem: 420/490-520 nm), C2FA (C2 in fulvic acid fraction) (λex/λem: 400/487(517) nm) and C1HA (C1 in humic acid fraction) (λex/λem: 350/452(520) nm). We explored the impact of increasing the volume of the added pure BaP solution on the scores of the fluorophores present in the soil fractions. It was found that the scores of C2HSs, C2FA, and C1HA increased when the volume of the added pure BaP solution increased. Superposition of the excitation spectra of these fluorophores with the emission spectrum of BaP showed significant overlaps that might explain the observed interactions between BaP and the fluorescent compounds present in SOM physical fractions.

  3. The role of humic and fulvic acids in the phototransformation of phenolic compounds in seawater.

    PubMed

    Calza, P; Vione, D; Minero, C

    2014-09-15

    Humic substances (HS) are known to act as photosensitizers toward the transformation of pollutants in the surface layer of natural waters. This study focused on the role played by HS toward the transformation of xenobiotics in seawater, with the purpose of assessing the prevailing degradation routes. Phenol was chosen as model xenobiotic and its transformation was investigated under simulated sunlight in the presence of terrestrial or marine humic and fulvic acids, in pure water at pH8, artificial seawater (ASW) or natural seawater (NSW). The following parameters were determined: (1) the phenol degradation rate; (2) the variation in HS concentration with irradiation time; (3) the production of transformation products; (4) the influence of iron species on the transformation process. Faster transformation of phenol was observed with humic acids (HA) compared to fulvic acids (SRFA), and transformation induced by both HA and SRFA was faster in ASW than that in pure water. These observations can be explained by assuming an interplay between different competing and sometimes opposite processes, including the competition between chloride, bromide and dissolved oxygen for reaction with HS triplet states. The analysis of intermediates formed in the different matrices under study showed the formation of several hydroxylated (hydroquinone, 1,4-benzoquinone, resorcinol) and condensed compounds (2,2'-bisphenol, 4,4'-bisphenol, 4-phenoxyphenol). Although 1,4-benzoquinone was the main transformation product, formation of condensed molecules was significant with both HA and SRFA. Experiments on natural seawater spiked with HS confirmed the favored formation of condensed products, suggesting a key role of humic matter in dimerization reactions occurring in saline water. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Influence of Humic Acid Complexation with Metal Ions on Extracellular Electron Transfer Activity.

    PubMed

    Zhou, Shungui; Chen, Shanshan; Yuan, Yong; Lu, Qin

    2015-11-23

    Humic acids (HAs) can act as electron shuttles and mediate biogeochemical cycles, thereby influencing the transformation of nutrients and environmental pollutants. HAs commonly complex with metals in the environment, but few studies have focused on how these metals affect the roles of HAs in extracellular electron transfer (EET). In this study, HA-metal (HA-M) complexes (HA-Fe, HA-Cu, and HA-Al) were prepared and characterized. The electron shuttle capacities of HA-M complexes were experimentally evaluated through microbial Fe(III) reduction, biocurrent generation, and microbial azoreduction. The results show that the electron shuttle capacities of HAs were enhanced after complexation with Fe but were weakened when using Cu or Al. Density functional theory calculations were performed to explore the structural geometry of the HA-M complexes and revealed the best binding sites of the HAs to metals and the varied charge transfer rate constants (k). The EET activity of the HA-M complexes were in the order HA-Fe > HA-Cu > HA-Al. These findings have important implications for biogeochemical redox processes given the ubiquitous nature of both HAs and various metals in the environment.

  5. Natural and pyrogenic humic acids at goethite and natural oxide surfaces interacting with phosphate.

    PubMed

    Hiemstra, Tjisse; Mia, Shamim; Duhaut, Pierre-Benoît; Molleman, Bastiaan

    2013-08-20

    Fulvic and humic acids have a large variability in binding to metal (hydr) oxide surfaces and interact differently with oxyanions, as examined here experimentally. Pyrogenic humic acid has been included in our study since it will be released to the environment in the case of large-scale application of biochar, potentially creating Darks Earths or Terra Preta soils. A surface complexation approach has been developed that aims to describe the competitive behavior of natural organic matter (NOM) in soil as well as model systems. Modeling points unexpectedly to a strong change of the molecular conformation of humic acid (HA) with a predominant adsorption in the Stern layer domain at low NOM loading. In soil, mineral oxide surfaces remain efficiently loaded by mineral-protected organic carbon (OC), equivalent with a layer thickness of ≥ ~0.5 nm that represents at least 0.1-1.0% OC, while surface-associated OC may be even three times higher. In natural systems, surface complexation modeling should account for this pervasive NOM coverage. With our charge distribution model for NOM (NOM-CD), the pH-dependent oxyanion competition of the organo-mineral oxide fraction can be described. For pyrogenic HA, a more than 10-fold increase in dissolved phosphate is predicted at long-term applications of biochar or black carbon.

  6. Assessing the influence of humic acids on the weathering of galena and its environmental implications.

    PubMed

    Liu, Qingyou; Li, Heping; Jin, Guoheng; Zheng, Kai; Wang, Luying

    2018-08-30

    Galena weathering often occurs in nature and releases metal ions during the process. Humic acid (HA), a critical particle of natural organic matter, binds metal ions, thus affecting metal transfer and transformation. In this work, an electrochemical method combined with spectroscopic techniques was adopted to investigate the interfacial processes involved in galena weathering under acidic and alkaline conditions, as well as in the presence of HA. The results show that the initial step of galena weathering involved the transformation Pb 2+ and S°, regardless of whether the solution was acidic or alkaline. Under acidic conditions, S° and Pb 2+ further transform into anglesite, and HA adsorbs on the galena surface, inhibiting the transformation of sulfur. HA and Pb (II) ions form bridging complexes. Under alkaline conditions without HA, the sulfur produced undergoes no transformation, whereas Pb 2+ will transform into PbO. The presence of HA changes the galena weathering mechanism via ionization effect, and Pb 2+ is ultimately converted into anglesite. Higher acidity in acidic conditions or higher alkalinity in alkaline conditions causes galena corrosion when the electrolyte does not contain HA. Conversely, higher pH always accelerates galena corrosion when the electrolyte contains HA, whether the electrolyte is acidic or alkaline. At the same acidity/alkalinity, increasing the concentration of HA inhibits galena weathering. Galena will release 134.7 g m -2 ·y -1 Pb 2+ to solution at pH 2.5, and the amount decreases to 28.09 g m -2 ·y -1 in the presence of 1000 mg/L HA. This study provides an in situ electrochemical method for the assessment of galena weathering. Copyright © 2018 Elsevier Inc. All rights reserved.

  7. Quantitative evaluation of noncovalent interactions between polyphosphate and dissolved humic acids in aqueous conditions.

    PubMed

    Fang, Wei; Sheng, Guo-Ping; Wang, Long-Fei; Ye, Xiao-Dong; Yu, Han-Qing

    2015-12-01

    As one kind of phosphorus species, polyphosphate (poly-P) is ubiquitous in natural environments, and the potential interactions between poly-P and humic substances in the sediments or natural waters would influence the fate of poly-P in the environments. However, the mechanism of the interactions has not yet been understood clearly. In this work, the characteristics and mechanisms of the interactions between humic acids (HA) and two model poly-P compounds with various chain lengths have been investigated. Results show that a stable polyphosphate-HA complex would be formed through the noncovalent interactions, and hydrogen bond might be the main driving force for the binding process, which might be formed between the proton-accepting groups of poly-P (e.g., PO and P-O(-)) and the oxygen containing functional groups in HA. Our findings implied that the presence of humic substances in natural waters, soils and sediments would influence the potential transport and/or mobility of environmental poly-P. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Gene quantification by the NanoGene assay is resistant to inhibition by humic acids.

    PubMed

    Kim, Gha-Young; Wang, Xiaofang; Ahn, Hosang; Son, Ahjeong

    2011-10-15

    NanoGene assay is a magnetic bead and quantum dot nanoparticles based gene quantification assay. It relies on a set of probe and signaling probe DNAs to capture the target DNA via hybridization. We have demonstrated the inhibition resistance of the NanoGene assay using humic acids laden genomic DNA (gDNA). At 1 μg of humic acid per mL, quantitiative PCR (qPCR) was inhibited to 0% of its quantification capability whereas NanoGene assay was able to maintain more than 60% of its quantification capability. To further increase the inhibition resistance of NanoGene assay at high concentration of humic acids, we have identified the specific mechanisms that are responsible for the inhibition. We examined five potential mechanisms with which the humic acids can partially inhibit our NanoGene assay. The mechanisms examined were (1) adsorption of humic acids on the particle surface; (2) particle aggregation induced by humic acids; (3) fluorescence quenching of quantum dots by humic acids during hybridization; (4) humic acids mimicking of target DNA; and (5) nonspecific binding between humic acids and target gDNA. The investigation showed that no adsorption of humic acids onto the particles' surface was observed for the humic acids' concentration. Particle aggregation and fluorescence quenching were also negligible. Humic acids also did not mimic the target gDNA except 1000 μg of humic acids per mL and hence should not contribute to the partial inhibition. Four of the above mechanisms were not related to the inhibition effect of humic acids particularly at the environmentally relevant concentrations (<100 μg/mL). However, a substantial amount of nonspecific binding was observed between the humic acids and target gDNA. This possibly results in lesser amount of target gDNA being captured by the probe and signaling DNA.

  9. Fluorescence studies on binding of pyrene and its derivatives to humic acid

    NASA Astrophysics Data System (ADS)

    Nakashima, K.; Maki, M.; Ishikawa, F.; Yoshikawa, T.; Gong, Y.-K.; Miyajima, T.

    2007-07-01

    Binding of pyrene (PyH) and its derivatives to humic acid (HA) has been studied by fluorescence spectroscopy. The nature of the interaction between HA and pyrene derivatives are extensively investigated by employing three derivatives ranging from anionic to cationic compounds: 1-pyrenebutylic acid (PyA), 1-pyrenemethanol (PyM), and 1-pyrenebutyltrimethylammonium bromide (PyB). Binding constants between HA and PyX (X = H, A, M, B) are obtained by steady-state fluorescence quenching techniques, and it is found that PyB has a markedly large binding constant among the pyrene family. This is attributed to a strong electrostatic interaction between cationic PyB and anionic HA. The result suggests that an electrostatic interaction plays a dominant role in binding of pyrenes to humic acid. The importance of electrostatic interaction was also confirmed by a salt effect on the binding constant. Influence of collisional quenching on the binding constant, which causes overestimation of the binding constant, was examined by time-resolved fluorescence spectroscopy as well as temperature effect in steady-state fluorescence measurements. It is elucidated that collisional quenching does not much bring overestimation into the binding constants.

  10. Surfactant toxicity to Artemia Franciscana and the influence of humic acid and chemical composition

    PubMed Central

    Deese, Rachel D.; LeBlanc, Madeline R.

    2016-01-01

    Surfactants can be extremely toxic to aquatic species and are introduced to the environment in a variety of ways. It is thus important to understand how other environmental constituents, in this case humic acids (HAs), may alter the toxicity of anthropogenic surfactants. Hatching and mortality assays of Artemia Franciscana were performed for three different toxic surfactants: Triton X-100 (Tx-100, non-ionic), cetylpyridinium chloride (CPC, cationic), and sodium dodecyl sulfate (SDS, anionic). Humic acids of varying composition and concentrations were added to the assays to determine the toxicity mitigating ability of the HAs. Tx-100 had a significant toxic effect on Artemia mortality rates and HAs from terrestrial sources were able to mitigate the toxicity, but an aquatic HA did not. CPC and SDS limited hatching success of the Artemia and, as HAs were added, the hatching percentages increased for all HA sources, indicating toxicity mitigation. In order to determine which functional groups within HAs were responsible for the interaction with the surfactants, the HAs were chemically modified by: (i) bleaching to reduce aromatics, (ii) Soxhlet extraction to reduce lipids, and (iii) acid hydrolysis to reduce O- and N-alkyl groups. Although most of the modified HAs had some toxicity mitigating ability for each of the surfactants, there were two notable differences: 1) the lipid-extracted HA did not reduce the toxicity of Tx-100 and 2) the bleached HA had a lower toxicity mitigating ability for CPC than the other modified HAs. PMID:27453688

  11. Experimental determination and modeling of arsenic complexation with humic and fulvic acids.

    PubMed

    Fakour, Hoda; Lin, Tsair-Fuh

    2014-08-30

    The complexation of humic acid (HA) and fulvic acid (FA) with arsenic (As) in water was studied. Experimental results indicate that arsenic may form complexes with HA and FA with a higher affinity for arsenate than for arsenite. With the presence of iron oxide based adsorbents, binding of arsenic to HA/FA in water was significantly suppressed, probably due to adsorption of As and HA/FA. A two-site ligand binding model, considering only strong and weak site types of binding affinity, was successfully developed to describe the complexation of arsenic on the two natural organic fractions. The model showed that the numbers of weak sites were more than 10 times those of strong sites on both HA and FA for both arsenic species studied. The numbers of both types of binding sites were found to be proportional to the HA concentrations, while the apparent stability constants, defined for describing binding affinity between arsenic and the sites, are independent of the HA concentrations. To the best of our knowledge, this is the first study to characterize the impact of HA concentrations on the applicability of the ligand binding model, and to extrapolate the model to FA. The obtained results may give insights on the complexation of arsenic in HA/FA laden groundwater and on the selection of more effective adsorption-based treatment methods for natural waters. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Phenanthrene binding by humic acid-protein complexes as studied by passive dosing technique.

    PubMed

    Zhao, Jian; Wang, Zhenyu; Ghosh, Saikat; Xing, Baoshan

    2014-01-01

    This work investigated the binding behavior of phenanthrene by humic acids (HA-2 and HA-5), proteins (bovine serum albumin (BSA)), lysozyme and pepsin), and their complexes using a passive dosing technique. All sorption isotherms were fitted well with Freundlich model and the binding capability followed an order of HA-5 > HA-2 > BSA > pepsin > lysozyme. In NaCl solution, phenanthrene binding to HA-BSA complexes was much higher than the sum of binding to individual HA and BSA, while there was no enhancement for HA-pepsin. Positively charged lysozyme slightly lowered phenanthrene binding on both HAs due to strong aggregation of HA-lysozyme complexes, leading to reduction in the number of binding sites. The binding enhancement by HA-BSA was observed under all tested ion species and ionic strengths. This enhancement can be explained by unfolding of protein, reduction of aggregate size and formation of HA-BSA complexes with favorable conformations for binding phenanthrene. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Consequence of chitosan treating on the adsorption of humic acid by granular activated carbon.

    PubMed

    Maghsoodloo, Sh; Noroozi, B; Haghi, A K; Sorial, G A

    2011-07-15

    In this work, equilibrium and kinetic adsorption of humic acid (HA) onto chitosan treated granular activated carbon (MGAC) has been investigated and compared to the granular activated carbon (GAC). The adsorption equilibrium data showed that adsorption behaviour of HA could be described reasonably well by Langmuir adsorption isotherm for GAC and Freundlich adsorption isotherm for MGAC. It was shown that pre-adsorption of chitosan onto the surface of GAC improved the adsorption capacity of HA changing the predominant adsorption mechanism. Monolayer capacities for the adsorption of HA onto GAC and MGAC were calculated 55.8 mg/g and 71.4 mg/g, respectively. Kinetic studies showed that film diffusion and intra-particle diffusion were simultaneously operating during the adsorption process for MGAC. Copyright © 2011 Elsevier B.V. All rights reserved.

  14. Prophylactic effects of humic acid-glucan combination against experimental liver injury

    PubMed Central

    Vetvicka, Vaclav; Garcia-Mina, Jose Maria; Yvin, Jean-Claude

    2015-01-01

    Aim: Despite intensive research, liver diseases represent a significant health problem and current medicine does not offer a substance able to significantly inhibit the hepatotoxicity leading to various stages of liver disease. Based on our previously published studies showing the protective effects of a glucan-humic acid (HA) combination, we focused on the hypothesis that the combination of these two natural molecules can offer prophylactic protection against experimentally induced hepatotoxicity. Materials and Methods: Lipopolysaccharide, carbon tetrachloride, and ethanol were used to experimentally damage the liver. Levels of aspartate aminotransferase, alanine transaminase, alkaline phosphatase, glutathione, superoxide dismutase, and malondialdehyde, known to correspond to the liver damage, were assayed. Results: Using three different hepatotoxins, we found that in all cases, some samples of HA and most of all the glucan-HA combination, offer strong protection against liver damage. Conclusion: Glucan-HA combination is a promising agent for use in liver protection. PMID:26401416

  15. Humic acids facilitated microbial reduction of polymeric Pu(IV) under anaerobic conditions.

    PubMed

    Xie, Jinchuan; Liang, Wei; Lin, Jianfeng; Zhou, Xiaohua; Li, Mei

    2018-01-01

    Flavins and humic substances have been extensively studied with emphasis on their ability to transfer extracellular electrons to insoluble metal oxides. Nevertheless, whether the low-solubility Pu(IV) polymers are microbially reduced to aqueous Pu(III) remains uncertain. Experiments were conducted under anaerobic and slightly alkaline conditions to study the difference between humic acids and flavins to transport extracellular electrons to Pu(IV) polymers. Our study demonstrates that Shewanella putrefaciens was unable to directly reduce polymeric Pu(IV) with a notably low reduction rate (3.4×10 -12 mol/L Pu(III) aq within 144h). The relatively high redox potential of flavins reveals the thermodynamically unfavorable reduction: E h (PuO 2 (am)/Pu 3+ )humic acids facilitated the extracellular electron transfer to the polymers and reduced polymeric Pu(IV) (2.1×10 -10 mol/L Pu(III) aq ) 62 times more rapidly than the flavins. The driving force for electron transfer explains the observed reduction: E h (HA ox /HA red )humic acids. In contrast, flavins were able to substantially reduce aqueous Pu(IV)-EDTA (1.9×10 -9 mol/L Pu(III) aq ) because of the available driving force for electron transfer: Δ r G m =-F[E h (PuL 2 4- /PuL 2 5- )-E h o '(FMN/FMNH 2 )]=-33.5kJ/mol is a result of E h (PuL 2 4- /PuL 2 5- )≫E h (PuO 2 (am)/Pu 3+ ), where L is the EDTA ligand. In the presence of humic acids, the reduction of Pu(IV)-EDTA exhibited the most rapid rate (2.2×10 -9 mol/L Pu(III) aq ). This result further demonstrates that humic acids facilitated the extracellular electron transfer to polymeric and aqueous Pu(IV). Reductive solubilization of the polymers may enhance Pu mobility in the geosphere and hence increases risks to human health. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Capillary Electrophoresis Profiles and Fluorophore Components of Humic Acids in Nebraska Corn and Philippine Rice Soils

    USDA-ARS?s Scientific Manuscript database

    As humic substances represent relatively high molecular mass polyelectrolytes containing aromatic, aliphatic and heterocyclic subunits, capillary electrophoresis (CE) has become an attractive method for “finger-print” characterization of humic acids. In addition, fluorescence excitation-emission ma...

  17. Characterization of humic acids by two-dimensional correlation fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Nakashima, K.; Xing, Shaoyong; Gong, Yongkuan; Miyajima, Toru

    2008-07-01

    We have investigated interaction between humic acids and heavy metal ions by fluorescence spectroscopy. The humic acids examined are Aldrich humic acid (AHA) and Dando humic acid (DHA), and heavy metal ions are Cu 2+ and Pb 2+. The binding constants between the humic acids and the heavy metal ions are obtained by a conventional fluorescence quenching technique. The two prominent bands in the fluorescence spectra of the humic acids give different binding constants, implying that the two bands are originated from different fluorescent species in the matrices of the humic acids. This was confirmed by two-dimensional correlation analysis based on the quenching perturbation on the fluorescence spectra. Two prominent cross peaks corresponding to the two fluorescence bands are obtained in the asynchronous maps, indicating that the two fluorescence bands belong to different species. The order of the response of the two fluorescence bands to the quenching perturbation is also elucidated based on Noda's rule.

  18. Microscopic examination of the intestinal wall and selected organs of minipigs orally supplemented with humic acids.

    PubMed

    Büsing, Kirsten; Elhensheri, Mohamed; Entzian, Kristin; Meyer, Udo; Zeyner, Annette

    2014-04-01

    Humic acids are used to prophylactically treat intestinal diseases in a wide number of species, yet the mechanism of action remains unknown. The general assumption has been that humic acids act locally; however studies using young piglets show orally supplemented humic acids can penetrate the intestinal wall, and thus potentially act systemically. The objective of this study was to determine if humic acids could also cross the intestinal barrier in adult pigs and be detected in other organs. Adult minipigs (>18 months old) orally received either 1g humic acids/kg body weight (verum, n=3) or placebo (control, n=3), for 2 weeks. At the end of the feeding period tissue samples were harvested from the intestine, various glands and organs. Unstained tissue samples were examined by light microscopy for the presence of humic acid particles. No humic acid particles were detected in any of the unstained tissues from verum or control pigs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Label Distribution in Tissues of Wheat Seedlings Cultivated with Tritium-Labeled Leonardite Humic Acid

    PubMed Central

    Kulikova, Natalia A.; Abroskin, Dmitry P.; Badun, Gennady A.; Chernysheva, Maria G.; Korobkov, Viktor I.; Beer, Anton S.; Tsvetkova, Eugenia A.; Senik, Svetlana V.; Klein, Olga I.; Perminova, Irina V.

    2016-01-01

    Humic substances (HS) play important roles in the biotic-abiotic interactions of the root plant and soil contributing to plant adaptation to external environments. However, their mode of action on plants remains largely unknown. In this study the HS distribution in tissues of wheat seedlings was examined using tritium-labeled humic acid (HA) derived from leonardite (a variety of lignites) and microautoradiography (MAR). Preferential accumulation of labeled products from tritiated HA was found in the roots as compared to the shoots, and endodermis was shown to be the major control point for radial transport of label into vascular system of plant. Tritium was also found in the stele and xylem tissues indicating that labeled products from tritiated HA could be transported to shoot tissues via the transpiration stream. Treatment with HA lead to an increase in the content of polar lipids of photosynthetic membranes. The observed accumulation of labeled HA products in root endodermis and positive impact on lipid synthesis are consistent with prior reported observations on physiological effects of HS on plants such as enhanced growth and development of lateral roots and improvement/repairs of the photosynthetic status of plants under stress conditions. PMID:27350412

  20. Label Distribution in Tissues of Wheat Seedlings Cultivated with Tritium-Labeled Leonardite Humic Acid

    NASA Astrophysics Data System (ADS)

    Kulikova, Natalia A.; Abroskin, Dmitry P.; Badun, Gennady A.; Chernysheva, Maria G.; Korobkov, Viktor I.; Beer, Anton S.; Tsvetkova, Eugenia A.; Senik, Svetlana V.; Klein, Olga I.; Perminova, Irina V.

    2016-06-01

    Humic substances (HS) play important roles in the biotic-abiotic interactions of the root plant and soil contributing to plant adaptation to external environments. However, their mode of action on plants remains largely unknown. In this study the HS distribution in tissues of wheat seedlings was examined using tritium-labeled humic acid (HA) derived from leonardite (a variety of lignites) and microautoradiography (MAR). Preferential accumulation of labeled products from tritiated HA was found in the roots as compared to the shoots, and endodermis was shown to be the major control point for radial transport of label into vascular system of plant. Tritium was also found in the stele and xylem tissues indicating that labeled products from tritiated HA could be transported to shoot tissues via the transpiration stream. Treatment with HA lead to an increase in the content of polar lipids of photosynthetic membranes. The observed accumulation of labeled HA products in root endodermis and positive impact on lipid synthesis are consistent with prior reported observations on physiological effects of HS on plants such as enhanced growth and development of lateral roots and improvement/repairs of the photosynthetic status of plants under stress conditions.

  1. Substantial Humic Acid Adsorption to Activated Carbon Air Cathodes Produces a Small Reduction in Catalytic Activity.

    PubMed

    Yang, Wulin; Watson, Valerie J; Logan, Bruce E

    2016-08-16

    Long-term operation of microbial fuel cells (MFCs) can result in substantial degradation of activated carbon (AC) air-cathode performance. To examine a possible role in fouling from organic matter in water, cathodes were exposed to high concentrations of humic acids (HA). Cathodes treated with 100 mg L(-1) HA exhibited no significant change in performance. Exposure to 1000 mg L(-1) HA decreased the maximum power density by 14% (from 1310 ± 30 mW m(-2) to 1130 ± 30 mW m(-2)). Pore blocking was the main mechanism as the total surface area of the AC decreased by 12%. Minimization of external mass transfer resistances using a rotating disk electrode exhibited only a 5% reduction in current, indicating about half the impact of HA adsorption was associated with external mass transfer resistance and the remainder was due to internal resistances. Rinsing the cathodes with deionized water did not restore cathode performance. These results demonstrated that HA could contribute to cathode fouling, but the extent of power reduction was relatively small in comparison to large mass of humics adsorbed. Other factors, such as biopolymer attachment, or salt precipitation, are therefore likely more important contributors to long-term fouling of MFC cathodes.

  2. Particle size, charge and colloidal stability of humic acids coprecipitated with Ferrihydrite.

    PubMed

    Angelico, Ruggero; Ceglie, Andrea; He, Ji-Zheng; Liu, Yu-Rong; Palumbo, Giuseppe; Colombo, Claudio

    2014-03-01

    Humic acids (HA) have a colloidal character whose size and negative charge are strictly dependent on surface functional groups. They are able to complex large amount of poorly ordered iron (hydr)oxides in soil as a function of pH and other environmental conditions. Accordingly, with the present study we intend to assess the colloidal properties of Fe(II) coprecipitated with humic acids (HA) and their effect on Fe hydroxide crystallinity under abiotic oxidation and order of addition of both Fe(II) and HA. TEM, XRD and DRS experiments showed that Fe-HA consisted of Ferrihydrite with important structural variations. DLS data of Fe-HA at acidic pH showed a bimodal size distribution, while at very low pH a slow aggregation process was observed. Electrophoretic zeta-potential measurements revealed a negative surface charge for Fe-HA macromolecules, providing a strong electrostatic barrier against aggregation. Under alkaline conditions HA chains swelled, which resulted in an enhanced stabilization of the colloid particles. The increasing of zeta potential and size of the Fe-HA macromolecules, reflects a linear dependence of both with pH. The increase in the size and negative charge of the Fe-HA precipitate seems to be more affected by the ionization of the phenolic acid groups, than by the carboxylic acid groups. The main cause of negative charge generation of Fe/HA is due to increased dissociation of phenolic groups in more expanded structure. The increased net negative surface potential induced by coprecipitation with Ferrihydrite and the correspondent changes in configuration of the HA could trigger the inter-particle aggregation with the formation of new negative surface. The Fe-HA coprecipitation can reduce electrosteric repulsive forces, which in turn may inhibit the aggregation process at different pH. Therefore, coprecipitation of Ferrihydrite would be expected to play an important role in the carbon stabilization and persistence not only in organic soils, but

  3. Removal of humic acid by a new type of electrical hollow-fiber microfiltration (E-HFMF)

    NASA Astrophysics Data System (ADS)

    Shang, Ran; Deng, Hui-ping; Hu, Jing-yi

    2010-11-01

    Low pressure membrane filtration, such as microfiltration, was widely used in the field of drinking water purification in the past few decades. Traditional microfiltration membranes are not efficient enough in the removal of natural organic matters (NOM) from raw water. Moreover, they tend to be fouled by the NOM and the filtration age of the membranes is thus shrinked. To tackle these problems, a new type of electrical hollow-fiber microfiltration module (E-HFMF) was designed. In the E-HFMF module, the hollow-fiber microfiltration membranes were placed into the radialized electrical field which functioned from the centre to the exterior of the cylindrical cavity. The main goal of the present study was to evaluate the efficiency of E-HFMF to remove the humic acid (HA, one of the main components of NOM). According to the parallel tests compared with the traditional microfiltration, the removal rate of humic acid was raised to 70%˜85% in terms of UV-254 and to 60%˜75% in terms of DOC when filtrating with the E-HFMF, while the removal rates of humic acid were 10%˜20% and 1%˜10% respectively when filtrating with the traditional microfiltration. The negative charged humic acid moved to the anode because of the electrophoresis, so few humic acid could be able to permeate through the membrane. The electrophoresis mobility of the humic acid permeating through the traditional microfiltration decreased by 19%, while the same index from the E-HFMF decreased by 75%. This indicated that the electrophoresis played a significant role on removing the humic acid. According to the gel permeate chromatograph analysis, humic acid aggregated in an electric field and thus forms loose and permeable cake layer on the membrane surface, which also relieved membrane fouling. Meanwhile, the negative charged humic acid migrating to the anode at the center minimized the deposition onto the membrane surface, and eliminated the membrane fouling as a result. During the E-HFMF filtration, the

  4. Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

    DOE PAGES

    Ouyang, Kai; Yu, Xiao-Ying; Zhu, Yunlin; ...

    2017-08-26

    The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. But, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These resultsmore » suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular polymeric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn 2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn 2+ on HA. Furthermore, the combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.« less

  5. Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

    SciTech Connect

    Ouyang, Kai; Yu, Xiao-Ying; Zhu, Yunlin

    The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. However, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These resultsmore » suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular poly-meric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn 2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn 2+ on HA. The combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.« less

  6. Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms

    SciTech Connect

    Ouyang, Kai; Yu, Xiao-Ying; Zhu, Yunlin

    The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. But, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These resultsmore » suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular polymeric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn 2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn 2+ on HA. Furthermore, the combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems.« less

  7. Effects of humic acid on the interactions between zinc oxide nanoparticles and bacterial biofilms.

    PubMed

    Ouyang, Kai; Yu, Xiao-Ying; Zhu, Yunlin; Gao, Chunhui; Huang, Qiaoyun; Cai, Peng

    2017-12-01

    The effects of humic acid (HA) on interactions between ZnO nanoparticles (ZnO NPs) and Pseudomonas putida KT2440 biofilms at different maturity stages were investigated. Three stages of biofilm development were identified according to bacterial adenosine triphosphate (ATP) activity associated with biofilm development process. In the initial biofilm stage 1, the ATP content of bacteria was reduced by more than 90% when biofilms were exposed to ZnO NPs. However, in the mature biofilm stages 2 and 3, the ATP content was only slightly decreased. Biofilms at stage 3 exhibited less susceptibility to ZnO NPs than biofilms at stage 2. These results suggest that more mature biofilms have a significantly higher tolerance to ZnO NPs compared to young biofilms. In addition, biofilms with intact extracellular polymeric substances (EPS) showed higher tolerance to ZnO NPs than those without EPS, indicating that EPS play a key role in alleviating the toxic effects of ZnO NPs. In both pure ZnO NPs and ZnO-HA mixtures, dissolved Zn 2+ originating from the NPs significantly contributed to the overall toxicity. The presence of HA dramatically decreased the toxicity of ZnO NPs due to the binding of Zn 2+ on HA. The combined results from this work suggest that the biofilm maturity stages and environmental constituents (such as humic acid) are important factors to consider when evaluating potential risks of NPs to ecological systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. The influence of humic acid and clay content on the transport of polymer-coated iron nanoparticles through sand.

    PubMed

    Jung, Bahngmi; O'Carroll, Denis; Sleep, Brent

    2014-10-15

    The introduction of nanoscale zero valent iron (nZVI) into the subsurface has recently received significant attention as a potentially effective method for remediation of source zones of chlorinated solvents present as dense nonaqueous phase liquids (DNAPL). One of the challenges in the deployment of nZVI is to achieve good subsurface nZVI mobility to permit delivery of the nZVI to the target treatment zone. Stabilization of nZVI with various polymers has shown promise for enhancing nZVI subsurface mobility, but the impact of subsurface conditions on nZVI mobility has not been fully explored. In this study, the effect of humic acid and kaolinite on the transport of polymer-stabilized nZVI (carboxylmethyl cellulose-surface modified nZVI, CMC90K-RNIP) in sand was investigated using column experiments. In addition, effects of electrolytes on the stability of CMC90K-RNIP in the presence of humic acid, and the stability of humic acid-coated reactive nanoscale iron particles (HA-RNIP) at various humic acid concentrations were investigated. Humic acid enhanced the mobility of bare RNIP, whereas the transport of CMC90K-RNIP was not significantly affected by humic acid injected as a background solution, except at the highest concentration of 500mg/L. At lower pore water velocity, the effect of humic acid on the transport of CMC90K-RNIP was greater than that at high water velocity. Adding kaolinite up to 2% by weight to the sand column reduced the retention of CMC90K-RNIP, but further increases in kaolinite content (to 5%) did not significantly affect nZVI retention. The impact of kaolinite on nZVI retention was more pronounced at lower pore water velocities. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Changes in redox properties of humic acids upon sorption to alumina

    NASA Astrophysics Data System (ADS)

    Subdiaga, Edisson; Orsetti, Silvia; Jindal, Sharmishta; Haderlein, Stefan B.

    2016-04-01

    1. Introduction A prominent role of Natural Organic Matter (NOM) in biogeochemical processes is its ability to act as an electron shuttle, accelerating rates between a bulk electron donor and an acceptor. The underlying processes are reversible redox reactions of quinone moieties.1 This shuttling effect has been studied in two major areas: transformation of redox active pollutants and microbial respiration.2-3 Previous studies primarily compared effects in the presence or absence of NOM without addressing the redox properties of NOM nor its speciation. The interaction between humic acids (HA) and minerals might change properties and reactivity of organic matter. Specifically, we investigate whether changes in the redox properties of a HA occur upon sorption to redox inactive minerals. Since fractionation and conformational rearrangements of NOM moieties upon sorption are likely to happen, the redox properties of the NOM fractions upon sorption might differ as well. 2. Materials and methods Elliot Soil Humic Acid (ESHA), Pahokee Peat Humic Acid (PPHA) and Suwannee River Humic Acid (SRHA) were used as received from IHSS. Aluminum oxide (Al2O3) was suspended in 0.1M KCl. Sorption was studied at pH 7.0 in duplicate batch experiments for several HA/Al2O3 ratios. For the suspension (mineral + sorbed HA, plus dissolved HA), the filtrate (0.45μm) and the HA stock solution, the electron donating and accepting capacities (EDC and EAC) were determined following established procedures.4 3. Results All studied HA-Al2O3 systems showed similar behavior with regard to changes in redox properties. There was a significant increase in the EDC of the whole suspension compared to the stock solutions and the non-sorbed HA in the filtrate (up to 300% for PPHA). This effect was more pronounced with increasing amounts of sorbed HA in the suspension. Although ESHA had the highest sorption capacity on Al2O3 (~ 6 times higher than PPHA & SRHA), it showed the smallest changes in redox

  10. Mid-Infrared Spectroscopic Properties of Humic Acid and Fulvic Acid-Soil Mixtures

    USDA-ARS?s Scientific Manuscript database

    The detection of humic materials in soils is essential in order to determine organic matter (SOM) stability and C sequestration on agricultural land. Mid-Infrared (MidIR) spectroscopy has been used to characterize SOM quality [1], study extracted soil humic acids [2], develop calibrations for quanti...

  11. Mid-Infrared Spectroscopic Properties of Humic Acid and Fulvic Acid-Soil Mixtures.

    USDA-ARS?s Scientific Manuscript database

    The detection of humic materials in soils is essential in order to determine organic matter (SOM) stability and C sequestration on agricultural land. Mid-Infrared (MidIR) spectroscopy has been used to characterize SOM quality [1], study extracted soil humic acids [2], develop calibrations for quanti...

  12. Influence of different nominal molecular weight fractions of humic acids on phenol oxidation by permanganate.

    PubMed

    He, Di; Guan, Xiaohong; Ma, Jun; Yu, Min

    2009-11-01

    The effects of humic acid (HA) and its different nominal molecular weight (NMW) fractions on the phenol oxidation by permanganate were studied. Phenol oxidation by permanganate was enhanced by the presence of HA at pH 4-8, while slightly inhibited at pH 9-10. The effects of HA on phenol oxidation by permanganate were dependent on HA concentration and permanganate/phenol molar ratios. The high NMW fractions of HA enhanced phenol oxidation by permanganate at pH 7 more significantly than the low fractions of HA. The apparent second-order rate constants of phenol oxidation by permanganate in the presence of HA correlated well with their specific ultraviolet absorption (SUVA) at 254 nm and specific violet absorption (SVA) at 465 or 665 nm. High positive correlation coefficients (R(2) > 0.72) implied that pi-electrons of HA strongly influenced the reactivity of phenol towards permanganate oxidation which agreed well with the information provided by fluorescence spectroscopy. The FTIR analysis indicated that the HA fractions rich in aliphatic character, polysaccharide-like substances, and the amount of carboxylate groups had less effect on phenol oxidation by permanganate. The negative correlation between the rate constants of phenol oxidation by permanganate and O/C ratios suggested that the oxidation of phenol increased with a decrease in the content of oxygen-containing functional groups.

  13. Effect of humic acid in leachate on specific methanogenic activity of anaerobic granular sludge.

    PubMed

    Guo, Mengfei; Xian, Ping; Yang, Longhui; Liu, Xi; Zhan, Longhui; Bu, Guanghui

    2015-01-01

    In order to find out the effects of humic acid (HA) in anaerobic-treated landfill leachate on granular sludge, the anaerobic biodegradability of HA as well as the influences of HA on the total cumulative methane production, the anaerobic methanization process and the specific methanogenic activity (SMA) of granular sludge are studied in this paper. Experimental results show that as a non-biodegradable organic pollutant, HA is also difficult to be decomposed by microbes in the anaerobic reaction process. Presence of HA and changes in the concentration have no significant influences on the total cumulative methane production and the anaerobic methanization process of granular sludge. Besides, the total cumulative methane production cannot reflect the inhibition of toxics on the methanogenic activity of granular sludge on the premise of sufficient reaction time. Results also show that HA plays a promoting role on SMA of granular sludge. Without buffering agent the SMA value increased by 19.2% on average due to the buffering and regulating ability of HA, while with buffering agent the SMA value increased by 5.4% on average due to the retaining effect of HA on the morphology of the sludge particles. However, in the presence of leachate the SMA value decreased by 27.6% on average, because the toxic effect of the toxics in the leachate on granular sludge is much larger than the promoting effect of HA.

  14. Reinvestigation of the role of humic acid in the oxidation of phenols by permanganate.

    PubMed

    Sun, Bo; Zhang, Jing; Du, Juanshan; Qiao, Junlian; Guan, Xiaohong

    2013-12-17

    Humic acid (HA) affects the oxidation of phenolic compounds by permanganate, but the role of HA in the oxidation of phenols by permanganate is far from clear. The mechanisms by which HA influences the oxidation of phenols by permanganate at pH 5.0-9.0 were systematically examined in this study. The presence of HA enhanced the oxidation of phenolic compounds by permanganate at pH ≤7.0, with greater enhancement at lower pH values. The presence of HA facilitated the in situ formation of MnO2, implying the importance of reductive moieties of HA in this reaction. This was supported by the finding that HA preoxidized by ozone showed enhancements in the oxidation of phenols by permanganate at pH 5.0-6.0 smaller than those seen with pristine HA. The good correlation between HA-induced improvement in the oxidation rates of phenols by permanganate and those by preformed colloidal MnO2 at pH 5.0 confirmed that contribution of MnO2 formed in situ for the oxidation of phenols under this condition. The differences in the influence of Na2S2O3 and HA on the oxidation of phenol by permanganate revealed the fact that the continuous generation of fresh MnO2 and stabilization of the MnO2 formed in situ by HA were crucial for the HA-induced enhancement of the oxidation of phenols by permanganate at pH ≤7.0. The consumption of permanganate by HA and the poor oxidation ability of in situ-generated MnO2 under alkaline conditions resulted in the slightly negative effect of HA on the degradation rates of phenols by permanganate at pH >7.0.

  15. Influence of addition order and contact time on thorium(IV) retention by hematite in the presence of humic acids.

    PubMed

    Reiller, Pascal; Casanova, Florence; Moulin, Valérie

    2005-03-15

    The influence of addition order and contact time in the system hematite (alpha-Fe2O3)-humic acid (HA)-thorium(IV) (Th(IV)) was studied in batch experiments. Th(IV) is considered here as a chemical analogue of other actinides (IV). The sorption isotherms were acquired varying pH in the range 2-10 and HA concentration in the range 1-100 mg/L. As already observed by numerous authors, Th(IV) retention was hindered when HA and hematite were equilibrated beforehand during 24 h. As it has been observed in a previous study, this effect was drastic when the ratio between humic and surface (iron oxide) sites exceeds a critical value. However, when HA was added after a 24-h equilibration of the hematite-Th(IV) system, Th(IV) was barely desorbed from the iron oxide surface. Furthermore, no drastic effect of the ratio between humic and surface sites could be evidenced, as the increase of HA concentration only results in a slight monotonic decrease in Th(IV) retention. Increasing contact time between components of the systems only indicated slight Th(IV) retention variation. This was interpreted as a consequence of slow kinetic controls of both the Th(IV)-HA complexation and HA-hematite sorption.

  16. Simulation of the influence of EDTA on the sorption of heavy metals by humic acids

    NASA Astrophysics Data System (ADS)

    Kropacheva, T. N.; Didik, M. V.; Kornev, V. I.

    2015-04-01

    The results of mathematical simulation of sorption equilibria with the participation of divalent cations of heavy metals (HMs), chelant (EDTA), and insoluble forms of humic acids (HAs) are discussed. It is shown that the formation of chelates of metals with EDTA in solutions results in the decreasing sorption of the metals by humic acids. We also analyzed the effect of the acidity of the medium and the HM: EDTA: HA ratio (in a wide range) on the desorption of metals. The desorbing effect of EDTA on the metals is the highest at pH 3-5 and increases with an increase in the concentration of EDTA and a decrease in the concentration of HAs. With respect to the remobilization of metals under the impact of EDTA, the metal cations can be arranged into the following sequence: Cu(II) > Ni(II) > Pb(II) ≫ Cd(II) > Co(II) > Zn(II). The obtained data have been used to analyze the remobilization / extraction of HMs from soils with a high content of humic substances.

  17. Reduced humic acid nanosheets and its uses as nanofiller

    NASA Astrophysics Data System (ADS)

    Duraia, El-shazly M.; Henderson, B.; Beall, Gary W.

    2015-10-01

    Leonardite is highly oxidized form of lignite coal and contains a number of carboxyl groups around the edges of a graphene-like core. A novel approach has been developed to synthesize graphene oxide-like nanosheets in large scale utilizing leonardite as a starting material. Humic acid extracted from leonardite has been reduced by performing a high pressure catalytic hydrogenation. The reaction was carried out inside a high pressure stirred reactor at 150 °C and 750 psi (~5.2×106 Pa). Morphology of the as-synthesized samples showed porous platy particles and EDAX analysis indicates the carbon and oxygen atomic ratios as 96:4-97:3%. The as-synthesized material has been used as nanofiller in polyurethane. The reduced humic acid-polyurethane nanocomposite showed over 250% increase of Young's modulus. This new approach provides a low cost and scalable source for graphene oxide-like nanosheets in nanocomposite applications.

  18. Humic acid transport in saturated porous media: influence of flow velocity and influent concentration.

    PubMed

    Wei, Xiaorong; Shao, Mingan; Du, Lina; Horton, Robert

    2014-12-01

    Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media. Copyright © 2014. Published by Elsevier B.V.

  19. Evaluation of the potentials of humic acid removal in water by gas phase surface discharge plasma.

    PubMed

    Wang, Tiecheng; Qu, Guangzhou; Ren, Jingyu; Yan, Qiuhe; Sun, Qiuhong; Liang, Dongli; Hu, Shibin

    2016-02-01

    Degradation of humic acid (HA), a predominant type of natural organic matter in ground water and surface waters, was conducted using a gas phase surface discharge plasma system. HA standard and two surface waters (Wetland, and Weihe River) were selected as the targets. The experimental results showed that about 90.9% of standard HA was smoothly removed within 40 min's discharge plasma treatment at discharge voltage 23.0 kV, and the removal process fitted the first-order kinetic model. Roles of some active species in HA removal were studied by evaluating the effects of solution pH and OH radical scavenger; and the results presented that O3 and OH radical played significant roles in HA removal. Scanning electron microscope (SEM) and FTIR analysis showed that HA surface topography and molecular structure were changed during discharge plasma process. The mineralization of HA was analyzed by UV-Vis spectrum, dissolved organic carbon (DOC), specific UV absorbance (SUVA), UV absorption ratios, and excitation-emission matrix (EEM) fluorescence. The formation of disinfection by-products during HA sample chlorination was also identified, and CHCl3 was detected as the main disinfection by-product, but discharge plasma treatment could suppress its formation to a certain extent. In addition, approximately 82.3% and 67.9% of UV254 were removed for the Weihe River water and the Wetland water after 40 min of discharge plasma treatment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Effect of humic acid on ciprofloxacin removal by magnetic multifunctional resins

    PubMed Central

    Wang, Wei; Cheng, Jiade; Jin, Jing; Zhou, Qing; Ma, Yan; Zhao, Qingqing; Li, Aimin

    2016-01-01

    Background organic matter significantly influences the removal of emerging contaminants in natural water. In this work, the adsorption of ciprofloxacin (CPX) onto a series of magnetic multifunctional resins (GMA10-GMA90) in the presence and absence of humic acid (HA) was conducted to demonstrate the effect of HA. Both hydrophobic and ion exchange interactions contributed to CPX adsorption. Negative charge-assisted hydrogen bonds also participated in the adsorption process, resulting in the high adsorption amount of anionic CPX onto the negatively charged GMA30 under basic solutions. HA could impact CPX adsorption not only as a competitive adsorbate but also as an additional adsorbent. At pH 5.6, the additional adsorption sites provided by adsorbed HA molecules on the resins dominated and thus facilitated the adsorption process. While at pH 10, HA inhibited the adsorption of CPX by directly competing for ion exchange sites and coexisting with CPX in the solution. The ratio of the amount of CPX adsorbed by dissolved HA to that by the resin reached as high as 1.61 for GMA90. The adsorbed HA molecules onto the resins could provide additional adsorption sites for CPX as proven by the enhanced CPX adsorption in HA-preloading systems at pH 5.6. PMID:27464502

  1. Effect of humic acid on ciprofloxacin removal by magnetic multifunctional resins

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Cheng, Jiade; Jin, Jing; Zhou, Qing; Ma, Yan; Zhao, Qingqing; Li, Aimin

    2016-07-01

    Background organic matter significantly influences the removal of emerging contaminants in natural water. In this work, the adsorption of ciprofloxacin (CPX) onto a series of magnetic multifunctional resins (GMA10-GMA90) in the presence and absence of humic acid (HA) was conducted to demonstrate the effect of HA. Both hydrophobic and ion exchange interactions contributed to CPX adsorption. Negative charge-assisted hydrogen bonds also participated in the adsorption process, resulting in the high adsorption amount of anionic CPX onto the negatively charged GMA30 under basic solutions. HA could impact CPX adsorption not only as a competitive adsorbate but also as an additional adsorbent. At pH 5.6, the additional adsorption sites provided by adsorbed HA molecules on the resins dominated and thus facilitated the adsorption process. While at pH 10, HA inhibited the adsorption of CPX by directly competing for ion exchange sites and coexisting with CPX in the solution. The ratio of the amount of CPX adsorbed by dissolved HA to that by the resin reached as high as 1.61 for GMA90. The adsorbed HA molecules onto the resins could provide additional adsorption sites for CPX as proven by the enhanced CPX adsorption in HA-preloading systems at pH 5.6.

  2. Responses of root physiological characteristics and yield of sweet potato to humic acid urea fertilizer

    PubMed Central

    Kou, Meng; Tang, Zhonghou; Zhang, Aijun; Li, Hongmin; Wei, Meng

    2017-01-01

    Humic acid (HA), not only promote the growth of crop roots, they can be combined with nitrogen (N) to increase fertilizer use efficiency and yield. However, the effects of HA urea fertilizer (HA-N) on root growth and yield of sweet potato has not been widely investigated. Xushu 28 was used as the experimental crop to investigate the effects of HA-N on root morphology, active oxygen metabolism and yield under field conditions. Results showed that nitrogen application alone was not beneficial for root growth and storage root formation during the early growth stage. HA-N significantly increased the dry weight of the root system, promoted differentiation from adventitious root to storage root, and increased the overall root activity, total root length, root diameter, root surface area, as well as root volume. HA-N thus increased the activity of superoxide dismutase (SOD), peroxidase (POD), and Catalase (CAT) as well as increasing the soluble protein content of roots and decreasing the malondialdehyde (MDA) content. HA-N significantly increased both the number of storage roots per plant increased by 14.01%, and the average fresh weight per storage root increased by 13.7%, while the yield was also obviously increased by 29.56%. In this study, HA-N increased yield through a synergistic increase of biological yield and harvest index. PMID:29253886

  3. Investigating organic molecules responsible of auxin-like activity of humic acid fraction extracted from vermicompost.

    PubMed

    Scaglia, Barbara; Nunes, Ramom Rachide; Rezende, Maria Olímpia Oliveira; Tambone, Fulvia; Adani, Fabrizio

    2016-08-15

    This work studied the auxin-like activity of humic acids (HA) obtained from vermicomposts produced using leather wastes plus cattle dung at different maturation stages (fresh, stable and mature). Bioassays were performed by testing HA concentrations in the range of 100-6000mgcarbonL(-1). (13)C CPMAS-NMR and GC-MS instrumental methods were used to assess the effect of biological processes and starting organic mixtures on HA composition. Not all HAs showed IAA-like activity and in general, IAA-like activity increased with the length of the vermicomposting process. The presence of leather wastes was not necessary to produce the auxin-like activity of HA, since HA extracted from a mix of cattle manure and sawdust, where no leather waste was added, showed IAA-like activity as well. CPMAS (13)CNMR revealed that HAs were similar independently of the mix used and that the humification process involved the increasing concentration of pre-existing alkali soluble fractions in the biomass. GC/MS allowed the identification of the molecules involved in IAA-like effects: carboxylic acids and amino acids. The concentration of active molecules, rather than their simple presence in HA, determined the bio-stimulating effect, and a good linear regression between auxin-like activity and active stimulating molecules concentration was found (R(2)=-0.85; p<0.01, n=6). Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Effects of sewage sludge amendment on the properties of two Brazilian oxisols and their humic acids.

    PubMed

    Bertoncini, E I; D'Orazio, V; Senesi, N; Mattiazzo, M E

    2008-07-01

    The effect of sewage sludge (SS) amendment on the general properties of the top layers of a sandy and a clayey oxisols and on the nature of their humic acid (HA) fractions was evaluated by chemical and physico-chemical techniques. The amended soils, especially the sandy soil, benefited of SS amendment by increasing their pH to above neutrality and enhancing the contents of C, N, P, and Ca and cation exchange capacity. The SS-HA-like sample showed larger H and N contents and a greater aliphatic character and humification degree than the HAs isolated from non-amended soils. The composition and structure of amended soil HAs were affected by SS application as a function of soil type and layer. In particular, N-containing groups and aliphatic structures of SS-HA-like sample appears to be partially incorporated in the amended soil HAs, and these effects were more evident in the HAs from the sandy oxisol.

  5. Humic acids as pseudocapacitive electrolyte additive for electrochemical double layer capacitors

    NASA Astrophysics Data System (ADS)

    Wasiński, Krzysztof; Walkowiak, Mariusz; Lota, Grzegorz

    2014-06-01

    Novel electrolyte additive for electrochemical capacitors has been reported. It has been demonstrated for the first time that addition of humic acids (HA) to KOH-based electrolyte significantly increases capacitance of symmetrical capacitors with electrodes made of activated carbon. Specific capacitances determined by means of galvanostatic charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy consistently showed increases for HA concentrations ranging from 2% w/w up to saturated solution with maximum positive effect observed for 5% w/w of the additive. The capacitance increase has been attributed to complex faradaic processes involving oxygen-containing groups of HA molecules. Due to abundant resources, low cost and easy processability the reported solution can find application in electrochemical capacitor technologies.

  6. Nanoecotoxicity Assessment of Graphene Oxide and its Relationship with Humic Acid.

    PubMed

    Castro, Vera L; Clemente, Zaira; Jonsson, Claudio; Silva, Mariana; Vallim, José Henrique; de Medeiros, Aline Maria Zigiotto; Martinez, Diego Stéfani T

    2018-04-02

    The risk assessment of nanomaterials (NMs) is essential for regulatory purposes and for sustainable nanotechnological development. Although the application of the graphene oxide (GO) has been widely exploited, its environmental risk is not well understood since several environmental conditions can affect the behavior and toxicity of it. In the present work, the GO effect from aquatic ecosystems was assessed considering the interaction with humic acid (HA) on nine organisms: Raphidocelis subcapitata (green algae), Lemna minor (aquatic plant), Lactuca sativa (lettuce), Daphnia magna (planktonic microcrustacea), Artemia salina (brine shrimp), Chironomus sancticaroli (chironomidae), Hydra attenuata (freshwater polyp), and Caenorhabditis elegans and Panagrolaimus sp (nematodes). The No Observed Effect Concentration (NOEC) was calculated for each organism. The different criteria used to calculate NOEC values were transformed and plotted as a log-logistic function. The hypothetical hazardous concentration values HC5-50 were respectively 0.023 (0.005-0.056) and 0.10 (0.031-0.31) mg L -1 for GO with and without humic acid, respectively. The safest scenario associated to the Predictive No Effect Concentration (PNEC) values for GO in the aquatic compartment were estimated as 20 - 100 µg L -1 (in the absence of humic acid) and 5 - 23 µg L -1 (in the presence of humic acid). Finally, the approach presented in this study contributed to the risk assessment of GO-based nanomaterials and the establishment of nano-regulations. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  7. A comparison of water solubility enhancements of organic solutes by aquatic humic materials and commercial humic acids

    USGS Publications Warehouse

    Chlou, C.T.; Kile, D.E.; Brinton, T.I.; Malcolm, R.L.; Leenheer, J.A.; MacCarthy, P.

    1987-01-01

    Water solubility enhancements of 1,1-bis(p-chloro-phenyl)-2,2,2-trichloroethane (p,p???-DDT), 2,4,5,2???,5???-pentachlorobiphenyl (2,4,5,2???,5???-PCB), and 2,4,4???-tri-chlorobiphenyl (2,4,4???-PCB) by dissolved organic matter have been studied with the following samples: (1) acidic water samples from the Suwannee River, Georgia, and the Sopchoppy River, Florida; (2) a humic extract of a nearly neutral pH water from the Calcasieu River, Louisiana; (3) commercial humic acids from the Aldrich Chemical Co. and Fluka-Tridom Chemical Corp. The calculated partition coefficients on a dissolved organic carbon basis (Kdoc) for organic solutes with water samples and aquatic humic extracts from this and earlier studies indicate that the enhancement effect varies with the molecular composition of the aquatic humic materials. The Kdoc values with water and aquatic humic samples are, however, far less than the observed Kdoc values obtained with the two commercial samples, by factors of about 4-20. In view of this finding, one should be cautious in interpreting the effects of the dissolved organic matter on solubility enhancement of organic solutes on the basis of the use of commercial humic acids.

  8. Adsorption of lignite-derived humic acids on coal-based mesoporous activated carbons.

    PubMed

    Lorenc-Grabowska, Ewa; Gryglewicz, Grazyna

    2005-04-15

    The adsorption by a coal-based mesoporous activated carbon of humic acids (HAs) isolated from two Polish lignites was studied. For comparison, a commercial Aldrich humic acid was also included into this study. The differences in chemical structure and functional groups of HAs were determined by elemental analysis and infrared spectroscopy DRIFT. Two activated carbons used differed in terms of mesopore volume, mesopore size distribution, and chemical properties of the surface. The kinetics of adsorption of HAs have been discussed using three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model. It was found that the adsorption of HAs from alkaline solution on mesoporous activated carbon proceeds according to the pseudo-second-order model. The correlation coefficients were close to 1. The intraparticle diffusion of HA molecules within the carbon particle was identified to be the rate-limiting step. Comparing the two activated carbons, the carbon with a higher volume of pores with widths of 10-50 nm showed a greater removal efficiency of HA. An increase in the Freundlich adsorption capacity with decreasing carbon content of HA was observed. Among the HAs studied, S-HA shows characteristics indicating the highest contribution of small-size fraction. The S-HA was removed by both activated carbons to the highest extent. The effect of pH solution on the adsorption of HA was examined over the range pH 5.4-12.2. It was found that the extent of adsorption decreased with decreasing pH of the solution.

  9. Trihalomethane formation potential of aquatic and terrestrial fulvic and humic acids: Sorption on activated carbon.

    PubMed

    Abouleish, Mohamed Y Z; Wells, Martha J M

    2015-07-15

    Humic substances (HSs) are precursors for the formation of hazardous disinfection by-products (DBPs) during chlorination of water. Various surrogate parameters have been used to investigate the generation of DBPs by HS precursors and the removal of these precursors by activated carbon treatment. Dissolved organic carbon (DOC)- and ultraviolet absorbance (UVA254)-based isotherms are commonly reported and presumed to be good predictors of the trihalomethane formation potential (THMFP). However, THMFP-based isotherms are rarely published such that the three types of parameters have not been compared directly. Batch equilibrium experiments on activated carbon were used to generate constant-initial-concentration sorption isotherms for well-characterized samples obtained from the International Humic Substances Society (IHSS). HSs representing type (fulvic acid [FA], humic acid [HA]), origin (aquatic, terrestrial), and geographical source (Nordic, Suwannee, Peat, Soil) were examined at pH6 and pH9. THMFP-based isotherms were generated and compared to determine if DOC- and UVA254-based isotherms were good predictors of the THMFP. The sorption process depended on the composition of the HSs and the chemical nature of the activated carbon, both of which were influenced by pH. Activated carbon removal of THM-precursors was pH- and HS-dependent. In some instances, the THMFP existed after UVA254 was depleted. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Effect of humic acid preloading on phosphate adsorption onto zirconium-modified zeolite.

    PubMed

    Lin, Jianwei; Zhang, Zhe; Zhan, Yanhui

    2017-05-01

    A zirconium-modified zeolite (ZrMZ) was prepared, and then, humic acid (HA) was immobilized on the ZrMZ surface to prepare HA-loaded ZrMZ (HA-ZrMZ). The obtained ZrMZ and HA-ZrMZ were characterized by energy dispersive X-ray spectroscopy, elemental analyzer, N 2 adsorption/desorption isotherms, pH at the point of zero charge, and X-ray photoelectron spectroscopy. The adsorption characteristics of phosphate on ZrMZ and HA-ZrMZ were comparatively investigated in batch mode. The adsorption mechanism of phosphate on ZrMZ and HA-ZrMZ was investigated by ionic strength effect and 31 P nuclear magnetic resonance. The mechanism for phosphate adsorption onto ZrMZ was the formation of inner-sphere phosphate complexes at the solid/solution interface. The preloading of HA on ZrMZ reduced the phosphate adsorption capacity, and the more the HA loading amount, the lower the phosphate adsorption capacity. However, the preloading of HA on ZrMZ did not change the phosphate adsorption mechanism; i.e., the formation of inner-sphere phosphate surface complexes was still responsible for the adsorption of phosphate on HA-ZrMZ. The decreased phosphate adsorption capacity for ZrMZ after HA coating could be attributed to the fact that the coating of HA on ZrMZ reduced the amount of binding active sites available for phosphate adsorption, changed the adsorbent surface charges, and reduced the specific surface areas and pore volumes of ZrMZ.

  11. Influence of humic acid imposed changes of ferrihydrite aggregation on microbial Fe(III) reduction

    NASA Astrophysics Data System (ADS)

    Amstaetter, Katja; Borch, Thomas; Kappler, Andreas

    2012-05-01

    Microbial reduction of Fe(III) minerals at neutral pH is faced by the problem of electron transfer from the cells to the solid-phase electron acceptor and is thought to require either direct cell-mineral contact, the presence of Fe(III)-chelators or the presence of electron shuttles, e.g. dissolved or solid-phase humic substances (HS). In this study we investigated to which extent the ratio of Pahokee Peat Humic Acids (HA) to ferrihydrite in the presence and absence of phosphate influences rates of Fe(III) reduction by Shewanella oneidensis MR-1 and the identity of the minerals formed. We found that phosphate generally decreased reduction rates by sorption to the ferrihydrite and surface site blocking. In the presence of low ferrihydrite concentrations (5 mM), the addition of HA helped to overcome this inhibiting effect by functioning as electron shuttle between cells and the ferrihydrite. In contrast, at high ferrihydrite concentrations (30 mM), the addition of HA did not lead to an increase but rather to a decrease in reduction rates. Confocal laser scanning microscopy images and ferrihydrite sedimentation behaviour suggest that the extent of ferrihydrite surface coating by HA influences the aggregation of the ferrihydrite particles and thereby their accessibility for Fe(III)-reducing bacteria. We further conclude that in presence of dissolved HA, iron reduction is stimulated through electron shuttling while in the presence of only sorbed HA, no stimulation by electron shuttling takes place. In presence of phosphate the stimulation effect did not occur until a minimum concentration of 10 mg/l of dissolved HA was reached followed by increasing Fe(III) reduction rates up to dissolved HA concentrations of approximately 240 mg/l above which the electron shuttling effect ceased. Not only Fe(III) reduction rates but also the mineral products changed in the presence of HA. Sequential extraction, XRD and 57Fe-Mössbauer spectroscopy showed that crystallinity and grain

  12. Binding characteristics of Cu2+ to natural humic acid fractions sequentially extracted from the lake sediments.

    PubMed

    He, En; Lü, Changwei; He, Jiang; Zhao, Boyi; Wang, Jinghua; Zhang, Ruiqing; Ding, Tao

    2016-11-01

    Humic acids (HAs) determine the distribution, toxicity, bioavailability, and ultimate fate of heavy metals in the environment. In this work, ten HA fractions (F1-F10) were used as adsorbent, which were sequentially extracted from natural sediments of Lake Wuliangsuhai, to investigate the binding characteristics of Cu 2+ to HA. On the basis of the characterization results, differences were found between the ten extracted HA fractions responding to their elemental compositions and acidic functional groups. The characterization results reveal that the responses of ten extracted HA fractions to their elemental compositions and acidic functional groups were different. The O/C and (O + N)/C ratio of F1-F8 approximately ranged from 0.66 to 0.53 and from 0.72 to 0.61, respectively; the measured results showed that the contents of phenolic groups and carboxyl groups decreased from 4.46 to 2.60 mmol/g and 1.60 to 0.58 mmol/g, respectively. The binding characteristics of Cu 2+ to the ten HA fractions were well modeled by the bi-Langmuir model; the binding behavior of Cu 2+ to all the ten HA fractions were strongly impacted by pH and ionic strength. The FTIR and SEM-EDX image of HA fractions (pre- and post-adsorption) revealed that carboxyl and phenolic groups were responsible for the Cu 2+ sorption on the ten sequentially extracted HA fractions process, which is the same with the analysis of the ligand binding and bi-Langmuir models Accordingly, the adsorption capacity of the former HA fractions on Cu 2+ were higher than the latter ones, which may be attributed to the difference of carboxyl and phenolic group contents between the former and latter extracted HA fractions. Additionally, the functional groups with N and S should not be neglected. This work is hopeful to understand the environmental effect of humic substances, environmental geochemical behavior, and bioavailability of heavy metals in lakes.

  13. Uranium (VI) transport in saturated heterogeneous media: Influence of kaolinite and humic acid.

    PubMed

    Chen, Chong; Zhao, Kang; Shang, Jianying; Liu, Chongxuan; Wang, Jin; Yan, Zhifeng; Liu, Kesi; Wu, Wenliang

    2018-05-07

    Natural aquifers typically exhibit a variety of structural heterogeneities. However, the effect of mineral colloids and natural organic matter on the transport behavior of uranium (U) in saturated heterogeneous media are not totally understood. In this study, heterogeneous column experiments were conducted, and the constructed columns contained a fast-flow domain (FFD) and a slow-flow domain (SFD). The effect of kaolinite, humic acid (HA), and kaolinite/HA mixture on U(VI) retention and release in saturated heterogeneous media was examined. Media heterogeneity significantly influenced U fate and transport behavior in saturated subsurface environment. The presence of kaolinite, HA, and kaolinite/HA enhanced the mobility of U in heterogeneous media, and the mobility of U was the highest in the presence of kaolinite/HA and the lowest in the presence of kaolinite. In the presence of kaolinite, there was no difference in the amount of U released from the FFD and SFD. However, in the presence of HA and kaolinite/HA, a higher amount of U was released from the FFD. The findings in this study showed that medium structure and mineral colloids, as well as natural organic matter in the aqueous phase had significant effects on U transport and fate in subsurface environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Effect of fulvic and humic acids on iron and manganese homeostasis in rats.

    PubMed

    Szabó, József; Vucskits, András Valentin; Berta, Erzsébet; Andrásofszky, Emese; Bersényi, András; Hullár, István

    2017-03-01

    The objective of this study was to investigate the effects of fulvic acid (FA) and humic acid (HA) as the two main compounds of humic substances, separately on Fe and Mn homeostasis. Seventy-two male Wistar rats were randomly divided into 9 experimental groups. The control diet (AIN-93G formula) and diets supplemented with 0.1%, 0.2%, 0.4% and 0.8% HA or FA were fed for 26 days. Fe and Mn concentrations of the large intestinal content, liver, kidney, femur and hair were determined. No significant differences were observed in the production parameters. The effects of FA and HA on iron homeostasis were significantly different. FA proved to be a good iron source, and slightly increased the iron content of liver and kidney, but - up to a dietary iron level of 52.7 mg/kg - it did not influence the efficiency of iron absorption. Above a dietary iron level of 52.7 mg/kg down-regulation of Fe absorption can be assumed. HA significantly stimulated the iron uptake and there was no down-regulation of Fe absorption up to 0.8% dietary HA supplementation level (61.5 mg Fe/kg diet). In the HA groups the iron content of the liver and kidney decreased significantly, suggesting that in spite of the better Fe absorption, the HA-Fe complex does not provide iron to the investigated organs. Neither FA nor HA supplementation influenced the Fe content of the femur and hair and slightly decreased the Mn concentration in the large intestinal content. This effect was significant (with a 22.7% Mn concentration decrease) only at the HA supplementation rate of 0.8%. Neither FA nor HA influenced significantly the Mn concentrations of the liver, kidney and femur. The Mn concentration of the hair in rats receiving FA- or HA-supplemented diets was higher than in the control rats; however, this result needs further confirmation.

  15. Effect of environmental factors on the complexation of iron and humic acid.

    PubMed

    Fang, Kai; Yuan, Dongxing; Zhang, Lei; Feng, Lifeng; Chen, Yaojin; Wang, Yuzhou

    2015-01-01

    A method of size exclusion chromatography coupled with ultraviolet spectrophotometry and off-line graphite furnace atomic absorption spectrometry was developed to assess the complexation properties of iron (Fe) and humic acid (HA) in a water environment. The factors affecting the complexation of Fe and HA, such as ionic strength, pH, temperature and UV radiation, were investigated. The Fe-HA complex residence time was also studied. Experimental results showed that pH could influence the deprotonation of HA and hydrolysis of Fe, and thus affected the complexation of Fe and HA. The complexation was greatly disrupted by the presence of NaCl. Temperature had some influence on the complexation. The yield of Fe-HA complexes showed a small decrease at high levels of UV radiation, but the effect of UV radiation on Fe-HA complex formation at natural levels could be neglected. It took about 10 hr for the complexation to reach equilibrium, and the Fe-HA complex residence time was about 20 hr. Complexation of Fe and HA reached a maximum level under the conditions of pH 6, very low ionic strength, in the dark and at a water temperature of about 25°C, for 10 hr. It was suggested that the Fe-HA complex could form mainly in freshwater bodies and reach high levels in the warm season with mild sunlight radiation. With changing environmental parameters, such as at lower temperature in winter or higher pH and ionic strength in an estuary, the concentration of the Fe-HA complex would decrease. Copyright © 2014. Published by Elsevier B.V.

  16. Modeling the oxidation kinetics of sono-activated persulfate's process on the degradation of humic acid.

    PubMed

    Songlin, Wang; Ning, Zhou; Si, Wu; Qi, Zhang; Zhi, Yang

    2015-03-01

    Ultrasound degradation of humic acid has been investigated in the presence of persulfate anions at ultrasonic frequency of 40 kHz. The effects of persulfate anion concentration, ultrasonic power input, humic acid concentration, reaction time, solution pH and temperature on humic acid removal efficiency were studied. It is found that up to 90% humic acid removal efficiency was achieved after 2 h reaction. In this system, sulfate radicals (SO₄⁻·) were considered to be the mainly oxidant to mineralize humic acid while persulfate anion can hardly react with humic acid directly. A novel kinetic model based on sulfate radicals (SO₄⁻·) oxidation was established to describe the humic acid mineralization process mathematically and chemically in sono-activated persulfate system. According to the new model, ultrasound power, persulfate dosage, solution pH and reaction temperature have great influence on humic acid degradation. Different initial concentration of persulfate anions and humic acid, ultrasonic power, initial pH and reaction temperature have been discussed to valid the effectiveness of the model, and the simulated data showed new model had good agreement with the experiments data.

  17. Humic acid provenance influence to the adsorption capacity in uranium and thorium removal

    NASA Astrophysics Data System (ADS)

    Prasetyo, E.

    2018-01-01

    It is common knowledge that humic acid is organic compound without certain chemical composition since it is derived from different organic materials. Further this raises question whether the different humic acid sample used could lead to different adsorbent properties e.g. adsorption capacity. To address the problem, this paper is aimed to clarify the relation between the provenances of humic acid and synthesized adsorbent properties especially adsorption capacities by quantitative and qualitative functional groups determination including discussion on their effect to the metal ion adsorption mechanism using three humic acid samples. Two commercial samples were derived from recent compost while the other extracted from tertiary carbonaceous mudstone strata.

  18. The impact of humic and fulvic acids on the dynamic properties of liposome membranes: the ESR method.

    PubMed

    Man, Dariusz; Pisarek, Izabella; Braczkowski, Michał; Pytel, Barbara; Olchawa, Ryszard

    2014-06-01

    This paper presents the results of research on the influence of two fractions of humic substances (HS): fulvic acids (FA) and humic acids (HA), as a function of concentration, on the liposome membranes formed from egg yolk lecithin (EYL). The concentration of HS in relation to EYL changed from 0% to 10% by weight. The influence of HS on various areas of membranes: interphase water-lipid, in the lipid layer just below the polar part of the membrane and in the middle of the lipid bilayer, was investigated by different spin labels (TEMPO, DOXYL 5, DOXYL 16). The study showed that HA slightly decreased the fluidity of the analyzed membranes on the surface layer, while FA significantly liquidated the center of the lipid bilayer. The strong effect of both fractions of HS on the concentration of free radicals as a function of time was also described.

  19. Simultaneous analysis of small organic acids and humic acids using high performance size exclusion chromatography.

    PubMed

    Qin, Xiaopeng; Liu, Fei; Wang, Guangcai; Weng, Liping

    2012-12-01

    An accurate and fast method for simultaneous determination of small organic acids and much larger humic acids was developed using high performance size exclusion chromatography. Two small organic acids, i.e. salicylic acid and 2,3-dihydroxybenzoic acid, and one purified humic acid material were used in this study. Under the experimental conditions, the UV peaks of salicylic acid and 2,3-dihydroxybenzoic acid were well separated from the peaks of humic acid in the chromatogram. Concentrations of the two small organic acids could be accurately determined from their peak areas. The concentration of humic acid in the mixture could then be derived from mass balance calculations. The measured results agreed well with the nominal concentrations. The detection limits are 0.05 mg/L and 0.01 mg/L for salicylic acid and 2,3-dihydroxybenzoic acid, respectively. Applicability of the method to natural samples was tested using groundwater, glacier, and river water samples (both original and spiked with salicylic acid and 2,3-dihydroxybenzoic acid) with a total organic carbon concentration ranging from 2.1 to 179.5 mg C/L. The results obtained are promising, especially for groundwater samples and river water samples with a total organic carbon concentration below 9 mg C/L. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Effective removal of phosphate from aqueous solution using humic acid coated magnetite nanoparticles.

    PubMed

    Rashid, Mamun; Price, Nathaniel T; Gracia Pinilla, Miguel Ángel; O'Shea, Kevin E

    2017-10-15

    Effective removal of excess phosphate from water is critical to counteract eutrophication and restore water quality. In this study, low cost, environmentally friendly humic acid coated magnetite nanoparticles (HA-MNP) were synthesized and applied for the remediation of phosphate from aqueous media. The HA-MNPs, characterized by FTIR, TEM and HAADF-STEM showed the extensive coating of humic acid on the magnetite surface. The magnetic nanoparticles with diameters of 7-12 nm could be easily separated from the reaction mixture by using a simple hand held magnet. Adsorption studies demonstrate the fast and effective separation of phosphate with maximum adsorption capacity of 28.9 mg/g at pH 6.6. The adsorption behavior follows the Freundlich isotherm suggesting the formation of non-uniform multilayers of phosphate on the heterogeneous surface of HA-MNP. The adsorption kinetic fits the pseudo-second order model well with rate constants of 0.206 ± 0.003, 0.073 ± 0.002 and 0.061 ± 0.003 g mg -1 min -1 for phosphate (P) concentrations of 2, 5 and 10 mg/L respectively. The removal of phosphate was found higher at acidic and neutral pH compared to basic conditions. The nanoparticles exhibit good selectivity and adsorption efficiency for phosphate in presence of co-existing ions such as Cl - , SO 4 2- and NO 3 - with some inhibition effect by CO 3 2- . The effect of temperature on the adsorption reveals that the process is endothermic and spontaneous. HA-MNPs are promising, simple, environmentally friendly materials for the removal of phosphate from aqueous media. Copyright © 2017. Published by Elsevier Ltd.

  1. Study on kinetics of adsorption of humic acid modified by ferric chloride on U(VI)

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Y.; Lv, J. W.; Song, Y.; Dong, X. J.; Fang, Q.

    2017-11-01

    In order to reveal the adsorption mechanism of the ferric chloride modified humic acid on uranium, the influence of pH value and contact time of adsorption on uranium was studied through a series of batch experiments. Meanwhile, the adsorption kinetics was analyzed with pseudo-first order kinetic model and pseudo-second order kinetic model. The results show that adsorption is affected by the pH value of the solution and by contract time, and the best condition for adsorption on uranium is at pH=5 and the adsorption equilibrium time is about 80 min. Kinetics of HA-Fe adsorption on uranium accords with pseudo-second order kinetic model. The adsorption is mainly chemical adsorption, and complexes were produced by the reaction between uranium ions and the functional groups on the surface of HA-Fe, which can provide reference for further study of humic acid effecting on the migration of U(VI) in soil.

  2. Root-Shoot Signaling crosstalk involved in the shoot growth promoting action of rhizospheric humic acids

    PubMed Central

    Olaetxea, Maite; Mora, Verónica; García, Andrés Calderin; Santos, Leandro Azevedo; Baigorri, Roberto; Fuentes, Marta; Garnica, María; Berbara, Ricardo Luis Louro; Zamarreño, Angel Maria; Garcia-Mina, Jose M.

    2016-01-01

    ABSTRACT Numerous studies have shown the ability of humic substances to improve plant development. This action is normally reflected in an enhancement of crop yields and quality. However, the mechanisms responsible for this action of humic substances remain rather unknown. Our studies have shown that the shoot promoting action of sedimentary humic acids is dependent of its ability to increase root hydraulic conductivity through signaling pathways related to ABA, which in turn is affected in roots by humic acids in an IAA-NO dependent way. Furthermore, these studies also indicate that the primary action of humic acids in roots might also be physical, resulting from a transient mild stress caused by humic acids associated with a fouling-cleaning cycle of wall cell pores. Finally the role of alternative signal molecules, such as ROS, and corresponding signaling pathways are also discussed and modeled in the context of the above-mentioned framework. PMID:26966789

  3. Molecular characteristics of humic acids isolated from vermicomposts and their relationship to bioactivity.

    PubMed

    Martinez-Balmori, Dariellys; Spaccini, Riccardo; Aguiar, Natália Oliveira; Novotny, Etelvino Henrique; Olivares, Fábio Lopes; Canellas, Luciano Pasqualoto

    2014-11-26

    Vermitechnology is an effective composting method, which transforms biomass into nutrient-rich organic fertilizer. Mature vermicompost is a renewable organic product containing humic substances with high biological activity. The aim of this study was to assess the chemical characteristics and the bioactivity of humic acids isolated from different vermicomposts produced with either cattle manure, sugar cane bagasse, sunflower cake from seed oil extraction, or filter cake from a sugar cane factory. More than 200 different molecules were found, and it was possible to identify chemical markers on humic acids according to the nature of the organic source. The large hydrophobic character of humic extracts and the preservation of altered lignin derivatives confer to humic acids the ability to induce lateral root emergence in maize seedlings. Humic acid-like substances extracted from plant biomass residues represent an additional valuable product of vermicomposting that can be used as a plant growth promoter.

  4. Characterization of pH-fractionated humic acids with respect to their dissociation behaviour.

    PubMed

    Klučáková, Martina

    2016-04-01

    Humic acids were divided into several fractions using buffer solutions as extraction agents with different pH values. Two methods of fractionation were used. The first one was subsequent dissolution of bulk humic acids in buffers adjusted to different pH. The second one was sequential dissolution in buffers with increasing pH values. Experimental data were compared with hypothesis of partial solubility of humic acids in aqueous solutions. Behaviour of humic fractions obtained by sequential dissolution, original bulk sample and residual fractions obtained by subsequent dissolution at pH 10 and 12 agrees with the hypothesis. Results demonstrated that regardless the common mechanism, solubility and dissociation degree of various humic fractions may be very different and can be estimated using parameters of the model based on the proposed mechanism. Presented results suggest that dissolving of solid humic acids in water environment is more complex than conventional solubility behaviour of sparingly soluble solids.

  5. Root-Shoot Signaling crosstalk involved in the shoot growth promoting action of rhizospheric humic acids.

    PubMed

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

    2016-01-01

    Numerous studies have shown the ability of humic substances to improve plant development. This action is normally reflected in an enhancement of crop yields and quality. However, the mechanisms responsible for this action of humic substances remain rather unknown. Our studies have shown that the shoot promoting action of sedimentary humic acids is dependent of its ability to increase root hydraulic conductivity through signaling pathways related to ABA, which in turn is affected in roots by humic acids in an IAA-NO dependent way. Furthermore, these studies also indicate that the primary action of humic acids in roots might also be physical, resulting from a transient mild stress caused by humic acids associated with a fouling-cleaning cycle of wall cell pores. Finally the role of alternative signal molecules, such as ROS, and corresponding signaling pathways are also discussed and modeled in the context of the above-mentioned framework.

  6. Sorption of Cu(2+) on humic acids sequentially extracted from a sediment.

    PubMed

    Yang, Kun; Miao, Gangfen; Wu, Wenhao; Lin, Daohui; Pan, Bo; Wu, Fengchang; Xing, Baoshan

    2015-11-01

    In addition to the diverse properties of humic acids (HAs) extracted from different soils or sediments, chemical compositions, functional groups and structures of HAs extracted from a single soil or sediment could also be diverse and thus significantly affect sorption of heavy metals, which is a key process controlling the transfer, transformation and fate of heavy metals in the environment. In this study, we sequentially extracted four HA fractions from a single sediment and conducted the sorption experiments of Cu(2+) on these HA fractions. Our results showed that aromaticity and acidic group content of HA fraction decreased with increasing extraction. Earlier extracted HA fraction had higher sorption capacity and affinity for Cu(2+). There were two fractions of adsorbed Cu(2+) on HAs, i.e., ion exchanged fraction and surface bonded fraction, which can be captured mechanically by the bi-Langmuir model with good isotherm fitting. The ion exchanged fraction had larger sorption capacity but lower sorption affinity, compared with the surface bonded fraction. The dissociated carboxyl groups of HAs were responsible for both fractions of Cu(2+) sorption, due to the more Cu(2+) sorption on the earlier extracted HA fraction with more carboxyl groups and at higher pH. The intensive competition between H(+) and the exchangeable Cu(2+) could result in the decrease of ion exchanged capacity and affinity for Cu(2+) on HAs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Potential Regulatory Role of Gibberellic and Humic Acids in Sprouting of Chlorophytum borivilianum Tubers

    PubMed Central

    Puteh, Adam; Hassan, Siti Aishah

    2014-01-01

    Tubers of safed musli (Chlorophytum borivilianum) were immersed in three different concentrations of gibberellic acid (GA3) or humic acid (HA) prior to planting. The highest concentration of GA3 (20 mg L−1) and all concentrations of HA (5, 10, and 15%) appeared to hasten tuber sprouting and promote uniform sprouting pattern. The use of 20 mg L−1 GA3 or 15% HA successfully improved sprouting and mean sprouting time. Safed musli growth and development was improved through the increase in the number of leaves, total leaf area, leaf area index, and total fibrous root length. This directly influenced the number of new tubers formed. The use of 20 mg L−1 GA3 or 15% HA gave similar response with nonsignificant difference among them. However, due to the cost of production, the result from this study suggests that 15% HA should be used to obtain improved sprouting percentage, homogeneous stand establishment, efficient plant growth and development, and increased yield of safed musli. PMID:24688363

  8. Humic Acid Confers HIGH-AFFINITY K+ TRANSPORTER 1-Mediated Salinity Stress Tolerance in Arabidopsis.

    PubMed

    Khaleda, Laila; Park, Hee Jin; Yun, Dae-Jin; Jeon, Jong-Rok; Kim, Min Gab; Cha, Joon-Yung; Kim, Woe-Yeon

    2017-12-31

    Excessive salt disrupts intracellular ion homeostasis and inhibits plant growth, which poses a serious threat to global food security. Plants have adapted various strategies to survive in unfavorable saline soil conditions. Here, we show that humic acid (HA) is a good soil amendment that can be used to help overcome salinity stress because it markedly reduces the adverse effects of salinity on Arabidopsis thaliana seedlings. To identify the molecular mechanisms of HA-induced salt stress tolerance in Arabidopsis, we examined possible roles of a sodium influx transporter HIGH-AFFINITY K+ TRANSPORTER 1 (HKT1). Salt-induced root growth inhibition in HKT1 overexpressor transgenic plants (HKT1-OX) was rescued by application of HA, but not in wild-type and other plants. Moreover, salt-induced degradation of HKT1 protein was blocked by HA treatment. In addition, the application of HA to HKT1-OX seedlings led to increased distribution of Na+ in roots up to the elongation zone and caused the reabsorption of Na+ by xylem and parenchyma cells. Both the influx of the secondary messenger calcium and its cytosolic release appear to function in the destabilization of HKT1 protein under salt stress. Taken together, these results suggest that HA could be applied to the field to enhance plant growth and salt stress tolerance via post-transcriptional control of the HKT1 transporter gene under saline conditions.

  9. Humic acids contribution to sedimentary organic matter on a shallow continental shelf (northern Adriatic Sea)

    NASA Astrophysics Data System (ADS)

    Giani, M.; Rampazzo, F.; Berto, D.

    2010-12-01

    The shallow northern Adriatic Sea receives large river runoff, predominantly from the Po River, which is the main allochthonous source of nutrients and organic matter. The origin and quality of organic matter deposited in the sediments can influence the degradation processes and oxygen consumption in the bottom waters as well as the fate of many pollutants. Therefore the humic acids (HA) were quantified in surface and sub-surface sediments collected in an area of the north-western Adriatic platform south of Po River. HA showed to have a relevant contribution to sedimentary organic matter. HA content in sediments were positively correlated with the organic carbon concentration and negatively with redox potential and pH, particularly in sub-surface reduced sediments, suggesting their important role in the diagenetic processes taking place in anoxic conditions. Elemental composition of HA extracted from surface and sub-surface sediments showed a wide range of variation of the C org/N ratios which could be due to a mixed (terrestrial and marine) origin and/or an elevated bacteria degradation of nitrogen during diagenesis processes in sediments. The spectroscopic ratios A 2/A 4 and A 4/A 6 of HA confirmed a mixed origin with a high degree of condensation of the HA extracted from sediments.

  10. Aminopropyl-Silica Hybrid Particles as Supports for Humic Acids Immobilization.

    PubMed

    Sándor, Mónika; Nistor, Cristina Lavinia; Szalontai, Gábor; Stoica, Rusandica; Nicolae, Cristian Andi; Alexandrescu, Elvira; Fazakas, József; Oancea, Florin; Donescu, Dan

    2016-01-08

    A series of aminopropyl-functionalized silica nanoparticles were prepared through a basic two step sol-gel process in water. Prior to being aminopropyl-functionalized, silica particles with an average diameter of 549 nm were prepared from tetraethyl orthosilicate (TEOS), using a Stöber method. In a second step, aminopropyl-silica particles were prepared by silanization with 3-aminopropyltriethoxysilane (APTES), added drop by drop to the sol-gel mixture. The synthesized amino-functionalized silica particles are intended to be used as supports for immobilization of humic acids (HA), through electrostatic bonds. Furthermore, by inserting beside APTES, unhydrolysable mono-, di- or trifunctional alkylsilanes (methyltriethoxy silane (MeTES), trimethylethoxysilane (Me₃ES), diethoxydimethylsilane (Me₂DES) and 1,2-bis(triethoxysilyl)ethane (BETES)) onto silica particles surface, the spacing of the free amino groups was intended in order to facilitate their interaction with HA large molecules. Two sorts of HA were used for evaluating the immobilization capacity of the novel aminosilane supports. The results proved the efficient functionalization of silica nanoparticles with amino groups and showed that the immobilization of the two tested types of humic acid substances was well achieved for all the TEOS/APTES = 20/1 (molar ratio) silica hybrids having or not having the amino functions spaced by alkyl groups. It was shown that the density of aminopropyl functions is low enough at this low APTES fraction and do not require a further spacing by alkyl groups. Moreover, all the hybrids having negative zeta potential values exhibited low interaction with HA molecules.

  11. Aminopropyl-Silica Hybrid Particles as Supports for Humic Acids Immobilization

    PubMed Central

    Sándor, Mónika; Nistor, Cristina Lavinia; Szalontai, Gábor; Stoica, Rusandica; Nicolae, Cristian Andi; Alexandrescu, Elvira; Fazakas, József; Oancea, Florin; Donescu, Dan

    2016-01-01

    A series of aminopropyl-functionalized silica nanoparticles were prepared through a basic two step sol-gel process in water. Prior to being aminopropyl-functionalized, silica particles with an average diameter of 549 nm were prepared from tetraethyl orthosilicate (TEOS), using a Stöber method. In a second step, aminopropyl-silica particles were prepared by silanization with 3-aminopropyltriethoxysilane (APTES), added drop by drop to the sol-gel mixture. The synthesized amino-functionalized silica particles are intended to be used as supports for immobilization of humic acids (HA), through electrostatic bonds. Furthermore, by inserting beside APTES, unhydrolysable mono-, di- or trifunctional alkylsilanes (methyltriethoxy silane (MeTES), trimethylethoxysilane (Me3ES), diethoxydimethylsilane (Me2DES) and 1,2-bis(triethoxysilyl)ethane (BETES)) onto silica particles surface, the spacing of the free amino groups was intended in order to facilitate their interaction with HA large molecules. Two sorts of HA were used for evaluating the immobilization capacity of the novel aminosilane supports. The results proved the efficient functionalization of silica nanoparticles with amino groups and showed that the immobilization of the two tested types of humic acid substances was well achieved for all the TEOS/APTES = 20/1 (molar ratio) silica hybrids having or not having the amino functions spaced by alkyl groups. It was shown that the density of aminopropyl functions is low enough at this low APTES fraction and do not require a further spacing by alkyl groups. Moreover, all the hybrids having negative zeta potential values exhibited low interaction with HA molecules. PMID:28787834

  12. Optimized Extraction Method To Remove Humic Acid Interferences from Soil Samples Prior to Microbial Proteome Measurements.

    PubMed

    Qian, Chen; Hettich, Robert L

    2017-07-07

    The microbial composition and their activities in soil environments play a critical role in organic matter transformation and nutrient cycling. Liquid chromatography coupled to high-performance mass spectrometry provides a powerful approach to characterize soil microbiomes; however, the limited microbial biomass and the presence of abundant interferences in soil samples present major challenges to proteome extraction and subsequent MS measurement. To this end, we have designed an experimental method to improve microbial proteome measurement by removing the soil-borne humic substances coextraction from soils. Our approach employs an in situ detergent-based microbial lysis/TCA precipitation coupled to an additional cleanup step involving acidified precipitation and filtering at the peptide level to remove most of the humic acid interferences prior to proteolytic peptide measurement. The novelty of this approach is an integration to exploit two different characteristics of humic acids: (1) Humic acids are insoluble in acidic solution but should not be removed at the protein level, as undesirable protein removal may also occur. Rather it is better to leave the humics acids in the samples until the peptide level, at which point the significant differential solubility of humic acids versus peptides at low pH can be exploited very efficiently. (2) Most of the humic acids have larger molecule weights than the peptides. Therefore, filtering a pH 2 to 3 peptide solution with a 10 kDa filter will remove most of the humic acids. This method is easily interfaced with normal proteolytic processing approaches and provides a reliable and straightforward protein extraction method that efficiently removes soil-borne humic substances without inducing proteome sample loss or biasing protein identification in mass spectrometry. In general, this humic acid removal step is universal and can be adopted by any workflow to effectively remove humic acids to avoid them negatively competing

  13. Insights into the Role of Humic Acid on Pd-catalytic Electro-Fenton Transformation of Toluene in Groundwater

    PubMed Central

    Liao, Peng; Al-Ani, Yasir; Malik Ismael, Zainab; Wu, Xiaohui

    2015-01-01

    A recently developed Pd-based electro-Fenton (E-Fenton) process enables efficient in situ remediation of organic contaminants in groundwater. In the process, H2O2, Fe(II), and acidic conditions (~pH 3) are produced in situ to facilitate the decontamination, but the role of ubiquitous natural organic matters (NOM) remain unclear. This study investigated the effect of Aldrich humic acid (HA) on the transformation of toluene by the Pd-based E-Fenton process. At pH 3 with 50 mA current, the presence of HA promoted the efficiency of toluene transformation, with pseudo-first-order rate constants increase from 0.01 to 0.016 as the HA concentration increases from 0 to 20 mg/L. The HA-enhanced toluene transformation was attributed to the accelerated thermal reduction of Fe(III) to Fe(II), which led to production of more hydroxyl radicals. The correlation of the rate constants of toluene transformation and HA decomposition validated hydroxyl radical (·OH) as the predominant reactive species for HA decomposition. The finding of this study highlighted that application of the novel Pd-based E-Fenton process in groundwater remediation may not be concerned by the fouling from humic substances. PMID:25783864

  14. Insights into the role of humic acid on Pd-catalytic electro-Fenton transformation of toluene in groundwater.

    PubMed

    Liao, Peng; Al-Ani, Yasir; Malik Ismael, Zainab; Wu, Xiaohui

    2015-03-18

    A recently developed Pd-based electro-Fenton (E-Fenton) process enables efficient in situ remediation of organic contaminants in groundwater. In the process, H₂O₂, Fe(II), and acidic conditions (~pH 3) are produced in situ to facilitate the decontamination, but the role of ubiquitous natural organic matters (NOM) remain unclear. This study investigated the effect of Aldrich humic acid (HA) on the transformation of toluene by the Pd-based E-Fenton process. At pH 3 with 50 mA current, the presence of HA promoted the efficiency of toluene transformation, with pseudo-first-order rate constants increase from 0.01 to 0.016 as the HA concentration increases from 0 to 20 mg/L. The HA-enhanced toluene transformation was attributed to the accelerated thermal reduction of Fe(III) to Fe(II), which led to production of more hydroxyl radicals. The correlation of the rate constants of toluene transformation and HA decomposition validated hydroxyl radical (·OH) as the predominant reactive species for HA decomposition. The finding of this study highlighted that application of the novel Pd-based E-Fenton process in groundwater remediation may not be concerned by the fouling from humic substances.

  15. Effect of Humic Acid on the Removal of Chromium(VI) and the Production of Solids in Iron Electrocoagulation.

    PubMed

    Pan, Chao; Troyer, Lyndsay D; Liao, Peng; Catalano, Jeffrey G; Li, Wenlu; Giammar, Daniel E

    2017-06-06

    Iron-based electrocoagulation can be highly effective for Cr(VI) removal from water supplies. However, the presence of humic acid (HA) inhibited the rate of Cr(VI) removal in electrocoagulation, with the greatest decreases in Cr(VI) removal rate at higher pH. This inhibition was probably due to the formation of Fe(II) complexes with HA that are more rapidly oxidized than uncomplexed Fe(II) by dissolved oxygen, making less Fe(II) available for reduction of Cr(VI). Close association of Fe(III), Cr(III), and HA in the solid products formed during electrocoagulation influenced the fate of both Cr(III) and HA. At pH 8, the solid products were colloids (1-200 nm) with Cr(III) and HA concentrations in the filtered fraction being quite high, while at pH 6 these concentrations were low due to aggregation of small particles. X-ray diffraction and X-ray absorption fine structure spectroscopy indicated that the iron oxides produced were a mixture of lepidocrocite and ferrihydrite, with the proportion of ferrihydrite increasing in the presence of HA. Cr(VI) was completely reduced to Cr(III) in electrocoagulation, and the coordination environment of the Cr(III) in the solids was similar regardless of the humic acid loading, pH, and dissolved oxygen level.

  16. Influence of humic acids of different origins on oxidation of phenol and chlorophenols by permanganate.

    PubMed

    He, Di; Guan, Xiaohong; Ma, Jun; Yang, Xue; Cui, Chongwei

    2010-10-15

    The influences of humic acids (HAs) of different origins, including two commercial HAs, three soil HAs and one aquatic HA, on phenols oxidation by permanganate were studied. The apparent second-order rate constants of 2-chlorophenol (2-CP)/phenol oxidation by permanganate in the presence of HAs at pH 7 followed the order of commercial HA (Shanghai)>soil HAs>commercial HA (Fluka)>aquatic HA. Moreover, the commercial HA (Shanghai) could accelerate the oxidation of different chlorophenols (CP) significantly under neutral condition. The FTIR analysis demonstrated greater content of CC moieties and less amount of carboxylate, aliphatic groups and polysaccharide-like substances in soil HAs than in aqueous HA, suggesting that the increase of aromaticity in HA was beneficial to the oxidation of phenols by permanganate. The apparent second-order rate constants of 2-CP/phenol oxidation by permanganate in the presence of HAs correlated well with specific visible absorption (SVA) at 665 nm of HAs. High positive correlation coefficients (R(2)>0.75) implied that pi-electrons of HA strongly influenced the reactivity of 2-CP/phenol towards permanganate oxidation, which agreed well with positive correlation between Fluorescence Regional Integration (FRI) and the apparent second-order rate constants. The pi-pi interaction between HAs and phenols, the steric hindrance effect and the dissociation of phenols may affect the oxidation of phenols by permanganate in the presence of HA at pH=7.0. 2010 Elsevier B.V. All rights reserved.

  17. Low humic acids promote in vitro lily bulblet enlargement by enhancing roots growth and carbohydrate metabolism * #

    PubMed Central

    Wu, Yun; Xia, Yi-ping; Zhang, Jia-ping; Du, Fang; Zhang, Lin; Ma, Yi-di; Zhou, Hong

    2016-01-01

    Bulblet development is a problem in global lily bulb production and carbohydrate metabolism is a crucial factor. Micropropagation acts as an efficient substitute for faster propagation and can provide a controllable condition to explore bulb growth. The present study was conducted to investigate the effects of humic acid (HA) on bulblet swelling and the carbohydrate metabolic pathway in Lilium Oriental Hybrids ‘Sorbonne’ under in vitro conditions. HA greatly promoted bulblet growth at 0.2, 2.0, and 20.0 mg/L, and pronounced increases in bulblet sucrose, total soluble sugar, and starch content were observed for higher HA concentrations (≥2.0 mg/L) within 45 d after transplanting (DAT). The activities of three major starch synthetic enzymes (including adenosine 5'-diphosphate glucose pyrophosphorylase, granule-bound starch synthase, and soluble starch synthase) were enhanced dramatically after HA application especially low concentration HA (LHA), indicating a quick response of starch metabolism. However, higher doses of HA also caused excessive aboveground biomass accumulation and inhibited root growth. Accordingly, an earlier carbon starvation emerged by observing evident starch degradation. Relative bulblet weight gradually decreased with increased HA doses and thereby broke the balance between the source and sink. A low HA concentration at 0.2 mg/L performed best in both root and bulblet growth. The number of roots and root length peaked at 14.5 and 5.75 cm, respectively. The fresh bulblet weight and diameter reached 468 mg (2.9 times that under the control treatment) and 11.68 mm, respectively. Further, sucrose/starch utilization and conversion were accelerated and carbon famine was delayed as a result with an average relative bulblet weight of 80.09%. To our knowledge, this is the first HA application and mechanism research into starch metabolism in both in vitro and in vivo condition in bulbous crops. PMID:27819136

  18. Low humic acids promote in vitro lily bulblet enlargement by enhancing roots growth and carbohydrate metabolism.

    PubMed

    Wu, Yun; Xia, Yi-Ping; Zhang, Jia-Ping; Du, Fang; Zhang, Lin; Ma, Yi-di; Zhou, Hong

    Bulblet development is a problem in global lily bulb production and carbohydrate metabolism is a crucial factor. Micropropagation acts as an efficient substitute for faster propagation and can provide a controllable condition to explore bulb growth. The present study was conducted to investigate the effects of humic acid (HA) on bulblet swelling and the carbohydrate metabolic pathway in Lilium Oriental Hybrids 'Sorbonne' under in vitro conditions. HA greatly promoted bulblet growth at 0.2, 2.0, and 20.0 mg/L, and pronounced increases in bulblet sucrose, total soluble sugar, and starch content were observed for higher HA concentrations (≥2.0 mg/L) within 45 d after transplanting (DAT). The activities of three major starch synthetic enzymes (including adenosine 5'-diphosphate glucose pyrophosphorylase, granule-bound starch synthase, and soluble starch synthase) were enhanced dramatically after HA application especially low concentration HA (LHA), indicating a quick response of starch metabolism. However, higher doses of HA also caused excessive aboveground biomass accumulation and inhibited root growth. Accordingly, an earlier carbon starvation emerged by observing evident starch degradation. Relative bulblet weight gradually decreased with increased HA doses and thereby broke the balance between the source and sink. A low HA concentration at 0.2 mg/L performed best in both root and bulblet growth. The number of roots and root length peaked at 14.5 and 5.75 cm, respectively. The fresh bulblet weight and diameter reached 468 mg (2.9 times that under the control treatment) and 11.68 mm, respectively. Further, sucrose/starch utilization and conversion were accelerated and carbon famine was delayed as a result with an average relative bulblet weight of 80.09%. To our knowledge, this is the first HA application and mechanism research into starch metabolism in both in vitro and in vivo condition in bulbous crops.

  19. Use of Fenton reagent combined with humic acids for the removal of PFOA from contaminated water.

    PubMed

    Santos, Aurora; Rodríguez, Sergio; Pardo, Fernando; Romero, Arturo

    2016-09-01

    Perfluorinated compounds (PFCs) are receiving significant attention due to its global distribution, high persistence, and bioaccumulation properties. Among them, perfluorooctanoic acid (PFOA) is one of the most commonly found in the environment. The strong bond C-F in PFOA is extremely difficult to degrade, therefore advanced oxidation processes (AOPs) at room temperature and pressure are not able to oxidize them, as was noticed here using Fenton like reagent (FR) or persulfate (PS) at 25°C. On the contrary, by using persulfate activated by heat (100mM and T=70°C) a complete defluorination of PFOA 0.1mM was noticed after 18h, with a sequential degradation mechanism of losing one CF2 unit from PFOA and its intermediates (perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPA) and perfluorobutanoic acid (PFBA)). Since this thermal treatment is not usually desirable from an economical point of view, alternative process has been tested. For this scope, a hybrid process is proposed in this work, by adding humic acid, HA, (600mgL(-1)) and FR, (165mM in H2O2 and 3mM in Fe(3+)) to the 0.1mM PFOA solution. It was found that the HA was oxidized by FR. PFOA was entrapped quantitatively and irreversibly during HA oxidation, resulting PFOA non-available to the aqueous phase. Oxidized HA with PFOA entrapped precipitates. Both, the leftover Fe(III) acting as a coagulant and neutral pH enhance the separation of this solid phase. The precipitation noticed by adding HA to the PFOA solution in absence of FR was negligible. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Reduction and Reoxidation of Humic Acid: Influence on Spectroscopic Properties and Proton Binding

    SciTech Connect

    Maurer, F.; Christl, I; Kretzschmar, R

    2010-01-01

    Previous studies on proton and metal binding to humic substances have not considered a potential influence of reduction and oxidation of functional groups. Therefore, we investigated how proton binding of a purified soil humic acid was affected by reduction. Reduction of the humic acid was carried out using an electrochemical cell that allowed us to measure the amounts of electrons and protons involved in reduction reactions. We further applied spectroscopic methods (UV-vis, fluorescence, FT-IR, C-1s NEXAFS) to detect possible chemical changes in the humic acid induced by reduction and reoxidation. The effect of reduction on proton binding was determined withmore » acid-base titrations in the pH range 4-10 under controlled redox conditions. During reduction, 0.54 mol kg{sup -1} protons and 0.55 mol kg{sup -1} electrons were transferred to humic acid. NICA-Donnan modeling revealed an equivalent increase in proton-reactive sites (0.52 mol kg{sup -1}) in the alkaline pH-range. Our results indicate that reduction of humic acid increased the amount of proton-reactive sites by 15% compared to the untreated state. Spectroscopic differences between the untreated and reduced humic acid were minor, apart from a lower UV-vis absorption of the reduced humic acid between 400 and 700 nm.« less

  1. EFFECT OF HUMIC ACID ON UPTAKE AND TRANSFER OF COPPER FROM MICROBES TO CILIATES TO COPEPODS

    EPA Science Inventory

    This research is part of an ongoing project designed to determine the effect of humic acid on the uptake and transfer of metals by marine organisms at the lower end of the food chain. Binding affinities for Cu, Cd, Zn, and Cr to Suwannee River humic acid were determined at variou...

  2. KINETIC ASPECTS OF CATION-ENHANCED AGGREGATION IN AQUEOUS HUMIC ACIDS. (R822832)

    EPA Science Inventory

    The cation-enhanced formation of hydrophobic domains in aqueous humic acids has been shown to be a slow process, consistent with the evolution and disintegration of humic acid configurations over periods lasting from days to weeks. After the addition of a magnesium salt to a humi...

  3. Renoprotective Effect of Humic Acid on Renal Ischemia-Reperfusion Injury: An Experimental Study in Rats.

    PubMed

    Akbas, Alpaslan; Silan, Coskun; Gulpinar, Murat Tolga; Sancak, Eyup Burak; Ozkanli, Sidika Seyma; Cakir, Dilek Ulker

    2015-12-01

    Humic acid is an antioxidant molecule used in agriculture and livestock breeding, as well as in medicine. Our aim was to investigate the potential renoprotective effects of humic acid in a renal ischemia reperfusion model. Twenty-one rats were randomly divided into three equal groups. Intraperitoneal serum or humic acid was injected at 1, 12, and 24 h. Non-ischemic group I was evaluated as sham. The left renal artery was clamped in serum (group II) and intraperitoneal humic acid (group III) to subject to left renal ischemic reperfusion procedure. Ischemia and reperfusion time was 60 min for each. Total antioxidant status, total oxidative status, oxidative stress index, and ischemia-modified albumin levels were analyzed biochemically from the serum samples. Kidneys were evaluated histopatologically and immunohistochemically. Biochemical results showed that total oxidative status, ischemia-modified albumin, and oxidative stress index levels were significantly decreased, but total antioxidant status was increased in the humic acid group (III) compared with the ischemia group (II) On histopathological examination, renal tubular dilatation, tubular cell damage and necrosis, dilatation of Bowman's capsule, hyaline casts, and tubular cell spillage were decreased in the humic acid group (III) compared with the ischemia group (II). Immunohistochemical results showed that apoptosis was deteriorated in group III. Renal ischemia reperfusion injury was attenuated by humic acid administration. These observations indicate that humic acid may have a potential therapeutic effect on renal ischemia reperfusion injury by preventing oxidative stress.

  4. CHARACTERIZATION OF HUMIC ACID SIZE FRACTIONS BY SEC AND MALS (R822832)

    EPA Science Inventory

    Latahco silt-loam humic acid was separated on a preparatory scale by size exclusion chromatography (SEC) on a gravity-fed Sepharose column. Four fractions from this separation were collected and further analyzed, along with whole humic acid, by high-performance SEC coupled with a...

  5. The role of humic acids and biochar as specific sorbents of pesticides in soil

    NASA Astrophysics Data System (ADS)

    Ćwieląg-Piasecka, Irmina; Dębicka, Magdalena; Medyńska-Jureszek, Agnieszka; Weber, Jerzy; Jamroz, Elżbieta

    2017-04-01

    Pesticides are widely used in agriculture to prevent or control different pests and increase yield as well as products quality. Despite of the strict regulations concerning sustainable use of plant protection products, their residues are very often present in soil. Depending on their chemical and physical properties, they undergo various transformations in the soil. This results in their retention on different sorbents, degradation by microorganisms or leaching to the groundwater. Biochar is a carbon-rich byproduct of thermal biomass conversion, and due to its high sorption properties can be an efficient sorbent for pesticides in soil. The aim of the research was to compare the effect of two types of organic sorbents - humic acids (HA) and biochar (BC) - in sorption-desorption processes of different pesticides, which residues are commonly present in arable soils and thus are potentially harmful for the environment. The humic acids were extracted from topsoil horizon of arable cambisoil derived from loam (Lower Silesia, Poland) by Shnitzer's method, then purified using XAD resin and freeze-dried. Biochar was produced from wheat straw in gasification process at 550˚C, remaining 30 minutes in the reactor. Investigated pesticides belong to three different chemical classes: carbamates (carbaryl and carbofuran), phenoxyacetic acids (2,4-D and MCPA) and aniline derivatives (metolachlor), and are active substances of commonly used plant protection products in agriculture. To obtain the experimental goal the sorption experiment was conducted. To the investigated organic matter samples (HA or BC) aliquots of pesticides solutions in 10M CaCl2 were added and the mixtures were shaken for 24h. Afterwards the samples were centrifuged and supernatants analyzed by LC-MS/MS for the pesticides content. After that the same samples were refilled with CaCl2 and analyzed in the same way for desorption studies. Humic acids exhibited strong affinity for the ionic substances (2,4-D, MCPA

  6. Induction of systemic resistance of benzothiadiazole and humic Acid in soybean plants against fusarium wilt disease.

    PubMed

    Abdel-Monaim, Montaser Fawzy; Ismail, Mamdoh Ewis; Morsy, Kadry Mohamed

    2011-12-01

    The ability of benzothiadiazole (BTH) and/or humic acid (HA) used as seed soaking to induce systemic resistance against a pathogenic strain of Fusarium oxysporum was examined in four soybean cultivars under greenhouse conditions. Alone and in combination the inducers were able to protect soybean plants against damping-off and wilt diseases compared with check treatment. These results were confirmed under field conditions in two different locations (Minia and New Valley governorates). The tested treatments significantly reduced damping-off and wilt diseases and increased growth parameters, except the number of branches per plant and also increased seed yield. Application of BTH (0.25 g/L) + HA (4 g/L) was the most potent in this respect. Soybean seed soaking in BTH + HA produced the highest activities of the testes of oxidative enzymes followed by BTH in the four soybean cultivars. HA treatment resulted in the lowest increases of these oxidative enzymes. Similar results were obtained with total phenol but HA increased total phenol more than did BTH in all tested cultivars.

  7. Column experiments to investigate transport of colloidal humic acid through porous media during managed aquifer recharge

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Zhou, Jingjing; Zhang, Wenjing; Huan, Ying; Yu, Xipeng; Li, Fulin; Chen, Xuequn

    2017-01-01

    Colloids act as vectors for pollutants in groundwater, thereby creating a series of environmental problems. While managed aquifer recharge plays an important role in protecting groundwater resources and controlling land subsidence, it has a significant effect on the transport of colloids. In this study, particle size and zeta potential of colloidal humic acid (HA) have been measured to determine the effects of different hydrochemistry conditions. Column experiments were conducted to examine the effects on the transport of colloidal HA under varying conditions of pH (5, 7, 9), ionic strength (<0.0005, 0.02, 0.05 M), cation valence (Na+, Ca2+) and flow rate (0.1, 0.2, 0.4 ml/min) through collectors (glass beads) to model the properties and quality of artificial recharge water and changes in the hydrodynamic field. Breakthrough curves showed that the behavior of colloidal HA being transported varied depending on the conditions. Colloid transport was strongly influenced by hydrochemical and hydrodynamic conditions. With decreasing pH or increasing ionic strength, a decrease in the peak effluent concentration of colloidal HA and increase in deposition could be clearly seen. Comparison of different cation valence tests indicated that changes in transport and deposition were more pronounced with divalent Ca2+ than with monovalent Na+. Changes in hydrodynamic field (flow rate) also had an impact on transportation of colloidal HA. The results of this study highlight the need for further research in this area.

  8. Enhanced photochemical conversion of NO2 to HONO on humic acids in the presence of benzophenone.

    PubMed

    Han, Chong; Yang, Wangjin; Yang, He; Xue, Xiangxin

    2017-12-01

    The photochemical conversion of NO 2 to HONO on humic acids (HA) in the presence of benzophenone (BP) was investigated using a flow tube reactor coupled to a NO x analyzer at ambient pressure. BP significantly enhanced the reduction of NO 2 to HONO on HA under simulated sunlight, as shown by the increase of NO 2 uptake coefficient (γ) and HONO yield with the mass ratio of BP to HA. The γ and HONO yield on the mixtures of HA and BP obviously depended on the environmental conditions. Both γ and HONO yield increased with the increase of irradiation intensity and temperature, whereas they decreased with pH. The γ exhibited a negative dependence on the NO 2 concentration, which had slight influences on the HONO yield. There were maximum values for the γ and HONO yield at relative humidity (RH) of 22%. Finally, atmospheric implications about the photochemical reaction of NO 2 and HA in the presence of photosensitive species were discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Nanotoxicity of graphene oxide: Assessing the influence of oxidation debris in the presence of humic acid.

    PubMed

    Clemente, Zaira; Castro, Vera Lúcia S S; Franqui, Lidiane S; Silva, Cristiane A; Martinez, Diego Stéfani T

    2017-06-01

    This study sought to evaluate the toxicological effects of graphene oxide (GO) through tests with Danio rerio (zebrafish) embryos, considering the influence of the base washing treatment and the interaction with natural organic matter (i.e., humic acid, HA). A commercial sample of GO was refluxed with NaOH to remove oxidation debris (OD) byproducts, which resulted in a base washed GO sample (bw-GO). This process decreased the total oxygenated groups in bw-GO and its stability in water compared to GO. When tested in the presence of HA, both GO and bw-GO stabilities were enhanced in water. Although the embryo exposure showed no acute toxicity or malformation, the larvae exposed to GO showed a reduction in their overall length and acetylcholinesterase activity. In the presence of HA, GO also inhibited acid phosphatase activity. Our findings indicate a mitigation of material toxicity after OD removal. The difference in the biological effects may be related to the materials' bioavailability and biophysicochemical interactions. This study reports for the first time the critical influence of OD on the GO material biological reactivity and HA interaction, providing new data for nanomaterial environmental risk assessment and sustainable nanotechnology. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Uptake of Cr3+ from aqueous solution by lignite-based humic acids.

    PubMed

    Arslan, G; Pehlivan, E

    2008-11-01

    Humic acid (HA) produced from brown coal, a relatively abundant and inexpensive material is currently being investigated as an adsorbent to remove toxic metals from aqueous solution. The influence of five parameters (contact time, solution pH, initial metal concentration, temperature and amount of adsorbent) on the removal at 20+/-1 degrees C was studied. HAs were prepared from lignites by using alkaline extraction, sedimentation and acidic precipitation. Adsorption equilibrium was achieved in about 60 min for Cr3+ ion. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The maximum adsorption capacity of 0.17 mmol for Ilgin (HA1), 0.29 mmol for Beysehir (HA2) and 0.18 mmol Ermenek (HA3) and 0.17 mmol of Cr3+/g for activated carbon (AC) was achieved, respectively at pH of 4.1. More than 84% of Cr3+ was removed by HA2, 54% by HA3 and 51% by HA1 and 50% by AC from aqueous solution. The adsorption was strongly dependent on pH but independent of ionic strength and metal ions. The adsorption of Cr3+ was higher between pH 4.1 and 5.1 for all HAs and maximum sorption was observed at pH 4.1. The rise in temperature caused a slight decrease in the value of the equilibrium constant (Kc) for the sorption of Cr3+ ion. Complex mechanisms including ion exchange, complexation and adsorption and size exclusion are possible for sorption of Cr3+ ion on HAs.

  11. Characterization of pH-fractionated humic acids derived from Chinese weathered coal.

    PubMed

    Zhang, Shuiqin; Yuan, Liang; Li, Wei; Lin, Zhian; Li, Yanting; Hu, Shuwen; Zhao, Bingqiang

    2017-01-01

    To reduce the compositional and structural heterogeneity of humic acids (HAs) and achieve better use of HA resources, in this study, we report a new sequential dissolution method for HAs derived from Chinese weathered coal. This method was used to separate HAs into seven fractions by adjusting the pH (3-10) of the extraction solution. The results showed that the HA fractions derived from Chinese weathered coal were concentrated up to 90.31% in the lower pH solutions (3-7). The compositional and structural characteristics of the HA fractions were determined by elemental analysis; ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), and solid-state 13 C-nuclear magnetic resonance (NMR) spectroscopies; and other techniques. The results showed significant differences among the HA fractions. The concentrations of the total acidic groups and the carboxyl groups decreased with the increasing pH of the extraction solution. However, the HA fractions derived from extraction solutions with pH 3-4 had relatively lower aromaticity but a higher protonated carbon content. The HA fractions derived from extraction solutions with pH 6-7 had the highest aromaticity and the greatest abundance of COO/N-C=O. This study demonstrated that adjusting the pH of the extraction solution is one way to fractionate HAs from Chinese weathered coal and to obtain HA fractions with compositions and structures that could serve as useful material for study and utilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Role of humic acid on oral drug delivery of an antiepileptic drug.

    PubMed

    Mirza, Mohd Aamir; Agarwal, Suraj Prakash; Rahman, Md Akhlaquer; Rauf, Abdur; Ahmad, Niyaz; Alam, Aftab; Iqbal, Zeenat

    2011-03-01

    Humic acid (HA) is omnipresent in natural organic matter that is a macromolecular, negatively charged polyelectrolyte that contains a hydrophobic core. It is also present in a significant amount in Shilajit (used frequently in traditional medicines), which is used in this study as a source of extraction. HA is evaluated for the oral drug delivery of carbamazepine (CBZ). HA is used in this study to increase the dissolution, intestinal permeation, and pharmacodynamic response of CBZ (bio pharmaceutics classification system (BCS) II) by the technique of complexation and other related mechanism reported with humic substances. Different complexation techniques were explored in this study for the entrapment of CBZ, which was authenticated by molecular modeling and conformational analysis. These were further characterized using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Solubility analysis and dissolution release profile were carried out to access the in vitro parameters. For ex vivo studies, rat gut intestinal permeability was done. And finally pharmacodynamic evaluation (maximal electroshock method) was carried out for optimized complexes. Molecular modeling approach and instrumental analysis (DSC, XRD, and FT-IR) confirmed the entrapment of CBZ inside the complexing agent. Increased solubility (∼1742%), sustained release (∼78%), better permeability (∼3.5 times), and enhanced pharmacodynamic responses conferred the best to 1:2 freeze dried (FD) and then 1:2 kneading (KD) complexes compared with pure CBZ. Now it could be concluded that HA may be tried as a complexing agent for antiepileptic drug and other classes of low water-soluble drug.

  13. The influence of mechanochemical modification on prevention of toxic ability of humic acids towards phenanthrene in aquatic environment

    NASA Astrophysics Data System (ADS)

    Shekhovtsova, N. S.; Maltseva, E. V.; Glyzina, T. S.; Ovchinnikova, I. S.

    2015-11-01

    The aim of the research work is to quantify interaction between phenanthrene with modified humic acids in aquatic environment. The changes in the structure and properties of humic acids after modifications were studied with 1H NMR spectroscopy and potentiometric titration methods. Our research demonstrates that the application of thiourea as a modified agent increases the binding capacity of humic acids towards phenanthrene.

  14. Effects of humic acid on phytodegradation of petroleum hydrocarbons in soil simultaneously contaminated with heavy metals.

    PubMed

    Park, Soyoung; Kim, Ki Seob; Kim, Jeong-Tae; Kang, Daeseok; Sung, Kijune

    2011-01-01

    The use of humic acid (HA) to enhance the efficiency of phytodegradation of petroleum hydrocarbons in soil contaminated with diesel fuel was evaluated in this study. A sample of soil was artificially contaminated with commercially available diesel fuel to an initial total petroleum hydrocarbons (TPH) concentration of 2300 mg/kg and four heavy metals with concentrations of 400 mg/kg for Pb, 200 mg/kg for Cu, 12 mg/kg for Cd, and 160 mg/kg for Ni. Three plant species, Brassica campestris, Festuca arundinacea, and Helianthus annuus, were selected for the phytodegradation experiment. Percentage degradation of TPH in the soil in a control pot supplemented with HA increased to 45% from 30% without HA. The addition of HA resulted in an increases in the removal of TPH from the soil in pots planted with B. campestris, E arundinacea, and H. annuus, enhancing percentage degradation to 86%, 64%, and 85% from 45%, 54%, and 66%, respectively. The effect of HA was also observed in the degradation of n-alkanes within 30 days. The rates of removal of n-alkanes in soil planted with B. campestris and H. annuus were high for n-alkanes in the range of C11-C28. A dynamic increase in dehydrogenase activity was observed during the last 15 days of a 30-day experimental period in all the pots amended with HA. The enhanced biodegradation performance for TPHs observed might be due to an increase in microbial activities and bioavailable TPH in soils caused by combined effects of plants and HA. The results suggested that HA could act as an enhancing agent for phytodegradation of petroleum hydrocarbons in soil contaminated with diesel fuel and heavy metals.

  15. Impact of humic acid on the degradation of levofloxacin by aqueous permanganate: Kinetics and mechanism.

    PubMed

    Xu, Ke; Ben, Weiwei; Ling, Wencui; Zhang, Yu; Qu, Jiuhui; Qiang, Zhimin

    2017-10-15

    Levofloxacin (LF) is a frequently detected fluoroquinolone in surface water, and permanganate (MnO 4 - ) is a commonly used oxidant in drinking water treatment. This study investigated the impact of humic acid (HA) on LF degradation by aqueous MnO 4 - from both kinetic and mechanistic aspects. In the absence of HA, the second-order rate constant (k) of LF degradation by MnO 4 - was determined to be 3.9 M -1  s -1 at pH 7.5, which increased with decreasing pH. In the presence of HA, the pseudo-first-order rate constant (k obs ) of LF degradation at pH 7.5 was significantly increased by 3.8- and 2.8-fold at [HA] o :[KMnO 4 ] o (mass ratio) = 0.5 and 1, respectively. Secondary oxidant scavenging and electron paramagnetic resonance tests indicated that HA could form a complex with Mn(III), a strongly oxidative intermediate produced in the reaction of MnO 4 - with HA, to induce the successive formation of superoxide radicals (O 2 - ) and hydroxyl radicals (OH). The resulting OH primarily contributed to the accelerated LF degradation, and the complex [HA-Mn(III)] could account for the rest of acceleration. The degradation of LF and its byproducts during MnO 4 - oxidation was mainly through hydroxylation, dehydrogenation and carboxylation, and the presence of HA led to a stronger destruction of LF. This study helps better understand the degradation of organic micropollutants by MnO 4 - in drinking water treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. A multi-method analysis of the interaction between humic acids and heavy metal ions.

    PubMed

    Ke, Tao; Li, Lu; Rajavel, Krishnamoorthy; Wang, Zhenyu; Lin, Daohui

    2018-03-08

    Understanding of the interaction between humic acids (HAs) and heavy metal ions (HMIs) is essential for the assessment of environmental and health risks of HMIs. Multiple analyses, including fluorescence quenching of HAs; solution pH, zeta potential, and hydrodynamic size changes; and coprecipitation of HAs and HMIs, were carried out to investigate the interaction between two HAs and four HMIs (Ag + , Pb 2+ , Cd 2+ , and Cr 3+ ). The HA-HMI interaction mainly included chemical complexation, H + -HMI exchange, electrostatic attraction, and flocculation. The chemical complexation between HAs and HMIs revealed by the Stern-Volmer quenching constant was ordered as Ag < Cd < Pb < Cr. HMIs replaced protons in the acidic functional groups of HAs and thus lowered the pH of the solution. The electrostatic interaction between the negatively charged HAs and HMIs reduced the electronegativity of HAs. Interaction with HMIs, especially the high-valent ions, induced aggregation of HAs, causing precipitation of both HAs and HMIs in the sorptive solution. Cr 3+ flocculated and precipitated HAs, but at high concentrations, it reversed the surface charge of HAs and resuspended them. The HA-HMI interaction increased as the HA acidity and solution pH increased.

  17. Speciation of chromium compounds from humic acid-zeolite Y to an ionic liquid during extraction.

    PubMed

    Huang, Hsin-Liang; Wei, Yu Jhe

    2018-03-01

    By synchrotron X-ray absorption spectroscopy, chemical structures of hexavalent chromium (Cr(VI))/trivalent chromium (Cr(III)) adsorbed on humic acid (HA)-zeolite Y and extracted in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate ([C 4 mim][BF 4 ])) have been studied. By combining the competitive adsorption results and reduction of Cr(VI)-HA with the carboxyl groups of HA, Cr(III)-HA (58%) was shown to be the major compound in HA-zeolite Y using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy. In an ionic liquid phase, the reduction of Cr(VI)-HA to Cr(III)-HA and the desorption of Cr(III) from HA were caused by [C 4 mim][BF 4 ]. The 9 F nuclear magnetic resonance (NMR) spectra show that the perturbation of the [C 4 mim][BF 4 ] anion was affected by the extractable chromium species. The formation of a Cr(III) ion affected the increase in the bond distance for the 1st shell CrO of the chromium species in [C 4 mim][BF 4 ] using extended X-ray absorption fine structure (EXAFS) spectroscopy. The changes in the non-extractable chromium species remaining in HA-zeolite Y were also caused by [C 4 mim][BF 4 ] during extraction. The desorption of the absorbed Cr(III) on HA and zeolite Y was observed to form Cr(III) ions. As the percentage of Cr(III) ions remaining in HA-zeolite Y increased, a slightly greater bond distance for CrO was found at 2.01 Å. The enhanced reduction of Cr(VI)-HA and desorption of Cr(III) adsorbed on the HA and zeolite Y to form Cr(III) ions were affected by [C 4 mim][BF 4 ]. Increased mobility of Cr(III) in the simulated soil can promote the migration of Cr(III) ions into the H 2 O during soil washing for remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. The onset of anthracene phototoxicity to Lemna gibba and the protective effects of humic acid

    SciTech Connect

    Gensemer, R.W.; Dixon, D.G.; Greenberg, B.M.

    1994-12-31

    The toxicity of anthracene to the freshwater duckweed Lemna gibba is strongly photo-induced in the presence of light containing natural levels of ultraviolet (UV) radiation. This was demonstrated using 8-day static renewal bioassays at an anthracene concentration of 2 mg-L{sup {minus}1}. Plants were incubated under simulated solar radiation (SSR) which mimics UV levels found in natural sunlight at a visible:UV-A:UV-B ratio of 100:10:1. Anthracene phototoxicity was expressed as inhibition of population growth and fluorescence induction decreases in chlorophyll content, and changes in low-temperature chlorophyll fluorescence emission scans. Furthermore, adding 6.2 mg-L-1 of an artificial humic acid ameliorated anthracene phototoxicity evenmore » though HA is also photo modified by UV light. However, anthracene inhibited photosynthesis days before the endpoint assays were performed. Therefore, the authors repeated these experiments at short time intervals following exposure to both light and chemical. Anthracene phototoxicity occurred after only 1 hour as detected by chlorophyll fluorescence induction, whereas chlorophyll contents and low-temperature fluorescence emission scans were not affected until 24--48 hours, respectively. Humic acid again ameliorated anthracene toxicity by delaying the negative physiological events by approximately 24 hours.« less

  19. Effects of humic acids on the aggregation and sorption of nano-TiO2.

    PubMed

    Li, Yanjie; Yang, Chen; Guo, Xuetao; Dang, Zhi; Li, Xiaoqin; Zhang, Qian

    2015-01-01

    In this study, humic acids (HAs) from three sources, peat, sediment and straw, used to coat nano-TiO2 were investigated. The results indicated that HAs isolated from peat were aromatic-rich, whereas those isolated from sediment and straw were aliphatic-rich. The nano-TiO2 sedimentation experiments indicated that the presence of aromatic-rich HAs was more capable of stabilizing nano-TiO2 particles than was the presence of aliphatic-rich HAs. This result is because the deionized phenolic groups in the HAs were preferentially adsorbed on the nano-TiO2 surfaces, which generated a higher charge density on the nano-TiO2 surfaces and caused stronger repulsive forces among particles. Furthermore, the aromatic-rich TiO2-HA complexes exhibited a greater sorption capacity than the aliphatic-rich TiO2-HAs complexes and nonlinear phenanthrene sorption because of their higher affinity and the condensed state of aromatic fractions. Note that natural organic matters, such as humic acids, in aquatic environments can not only increase the stability of nanoparticles but can also influence the mobility of hydrophobic organic compounds (HOCs). Copyright © 2014. Published by Elsevier Ltd.

  20. Mobilization of arsenic and heavy metals from polluted soils by humic acid

    NASA Astrophysics Data System (ADS)

    Reyes, Arturo; Fuentes, Bárbara; Letelier, María Victoria; Cuevas, Jacqueline

    2017-04-01

    The existence of soils contaminated with harmful elements by mining activities is a global environmental concern. The northern part of Chile has several heavy metal contaminated sites due to former copper and gold artisanal mining activities. Therefore, a complete characterization of abandoned sites and the implementation of remediation technologies are of interest for regulators, the industry, and the population. The objective of the study was to test the use of humic acid as a washing treatment to reduce the heavy metal concentration of soil samples impacted by mine waste material. A stratified random sampling was conducted on the target site to determine the physical and chemical composition of mine waste and soil material. The sampling consisted of taking 37 samples at 0-20 cm depths in a 10,000 square-meter area. The samples were dried and sieved at 2 mm. The batch washing experiments were conducted in triplicate at pH 7.0. A 1:10 solid to liquid ratio and three humic acid dose (0, 50, and 100 mg/l) were used. After shaking (24 h, room temperature) and subsequently filtration (0.22 μm), the supernatants were analyzed for heavy metals, redox potential and pH. The heavy metals mobility was assessed using extraction methods before and after treatments. The soils had alkaline pH values, conductivity ranged between 8 and 35 mS/cm, with low organic matter. Total concentrations of Vanadium (V) (10.80 to 175.00 mg/kg), Lead (Pb) (7.31 to 90.10 mg/kg), Antimonium (Sb) (0.83 to 101.00 mg/kg), and Arsenic (As) (9.53 to 2691.00 mg/kg) exceeded several times the EPA`s recommended values for soils. At 100 mg/L HA the removal efficiencies for V, Pb, Sb, and As were 32, 68, 77, and 82% respectively. According to the extraction procedure V, Pb, Sb, and As species are mainly as oxidizable and residual fractions. According to the results, the target mine site is contaminated with harmful elements. It can be concluded that the use of humic acid is a good alternative as a

  1. Metal loading levels influence on REE distribution on humic acid: Experimental and Modelling approach

    NASA Astrophysics Data System (ADS)

    Marsac, R.; Davranche, M.; Gruau, G.; Dia, A.

    2009-04-01

    In natural organic-rich waters, rare earth elements (REE) speciation is mainly controlled by organic colloids such as humic acid (HA). Different series of REE-HA complexation experiments performed at several metal loading (REE/C) displayed two pattern shapes (i) at high metal loading, a middle-REE (MREE) downward concavity, and (ii) at low metal loading, a regular increase from La to Lu (e.g. Sonke and Salters, 2006; Pourret et al., 2007). Both REE patterns might be related to REE binding with different surface sites on HA. To understand REE-HA binding, REE-HA complexation experiments at various metals loading were carried out using ultrafiltration combined with ICP-MS measurements, for the 14 REE simultaneously. The patterns of the apparent coefficients of REE partition between HA and the inorganic solution (log Kd) evolved regularly according to the metal loading. The REE patterns presented a MREE downward concavity at low loading and a regular increase from La to Lu at high loading. The dataset was modelled with Model VI by adjusting two specific parameters, log KMA, the apparent complexation constant of HA low affinity sites and DLK2, the parameter increasing high affinity sites binding strength. Experiments and modelling provided evidence that HA high affinity sites controlled the REE binding with HA at low metal loading. The REE-HA complex could be as multidentate complexes with carboxylic or phenolic sites or potentially with sites constituted of N, P or S as donor atoms. Moreover, these high affinity sites could be different for light and heavy REE, because heavy REE have higher affinity for these sites, in low density, and could saturate them. These new Model VI parameter sets allowed the prediction of the REE-HA pattern shape evolution on a large range of pH and metal loading. According to the metal loading, the evolution of the calculated REE patterns was similar to the various REE pattern observed in natural acidic organic-rich waters (pH<7 and DOC>10

  2. Mitigation in Multiple Effects of Graphene Oxide Toxicity in Zebrafish Embryogenesis Driven by Humic Acid.

    PubMed

    Chen, Yuming; Ren, Chaoxiu; Ouyang, Shaohu; Hu, Xiangang; Zhou, Qixing

    2015-08-18

    Graphene oxide (GO) is a widely used carbonaceous nanomaterial. To date, the influence of natural organic matter (NOM) on GO toxicity in aquatic vertebrates has not been reported. During zebrafish embryogenesis, GO induced a significant hatching delay and cardiac edema. The intensive interactions of GO with the chorion induces damage to chorion protuberances, excessive generation of (•)OH, and changes in protein secondary structure. In contrast, humic acid (HA), a ubiquitous form of NOM, significantly relieved the above adverse effects. HA reduced the interactions between GO and the chorion and mitigated chorion damage by regulating the morphology, structures, and surface negative charges of GO. HA also altered the uptake and deposition of GO and decreased the aggregation of GO in embryonic yolk cells and deep layer cells. Furthermore, HA mitigated the mitochondrial damage and oxidative stress induced by GO. This work reveals a feasible antidotal mechanism for GO in the presence of NOM and avoids overestimating the risks of GO in the natural environment.

  3. Effect of humic acids on the metabolism of Chlorella vulgaris in a model experiment

    NASA Astrophysics Data System (ADS)

    Toropkina, M. A.; Ryumin, A. G.; Kechaikina, I. O.; Chukov, S. N.

    2017-11-01

    The effect of humic acids (HAs) on physiological processes (photosynthesis, respiration, and abundance) of green microalga Chlorella vulgaris has been studied, and the relationships between the physiological activity of HAs and their structural parameters have been investigated. It has been found that the optimum range of HA concentrations for the growth of C. vulgaris is 0.01-0.03%. In this range, the highest positive effect on total photosynthesis increment is due to hydrophilic HA preparations from fallow soddypodzolic soil (Albic Retisol) and virgin gray soil (Luvic Greyzemic Phaeozem). The minimum stimulation of respiration is noted for all HA preparations in the region of the maximum photosynthesis stimulation. At concentrations above 0.003%, all HA preparations have a negative effect: the rate of photosynthesis in C. vulgaris cells decreases, and their respiration is strongly enhanced. The abundance of C. vulgaris under the effect of all of the studied preparations under illumination increases more rapidly than in the dark. A high positive coefficient of correlation is found between the hydrophilicity of HAs calculated from 13C NMR data and the photosynthesis rate in C. vulgaris.

  4. Removing uranium (VI) from aqueous solution with insoluble humic acid derived from leonardite.

    PubMed

    Meng, Fande; Yuan, Guodong; Larson, Steven L; Ballard, John H; Waggoner, Charles A; Arslan, Zikri; Han, Fengxiang X

    2017-12-01

    The occurrence of uranium (U) and depleted uranium (DU)-contaminated wastes from anthropogenic activities is an important environmental problem. Insoluble humic acid derived from leonardite (L-HA) was investigated as a potential adsorbent for immobilizing U in the environment. The effect of initial pH, contact time, U concentration, and temperature on U(VI) adsorption onto L-HA was assessed. The U(VI) adsorption was pH-dependent and achieved equilibrium in 2 h. It could be well described with pseudo-second-order model, indicating that U(VI) adsorption onto L-HA involved chemisorption. The U(VI) adsorption mass increased with increasing temperature with maximum adsorption capacities of 91, 112 and 120 mg g -1 at 298, 308 and 318 K, respectively. The adsorption reaction was spontaneous and endothermic. We explored the processes of U(VI) desorption from the L-HA-U complex through batch desorption experiments in 1 mM NaNO 3 and in artificial seawater. The desorption process could be well described by pseudo-first-order model and reached equilibrium in 3 h. L-HA possessed a high propensity to adsorb U(VI). Once adsorbed, the release of U(VI) from L-HA-U complex was minimal in both 1 mM NaNO 3 and artificial seawater (0.06% and 0.40%, respectively). Being abundant, inexpensive, and safe, L-HA has good potential for use as a U adsorbent from aqueous solution or immobilizing U in soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Towards multimodal HPLC separations on humic acid-bonded aminopropyl silica: RPLC and HILIC behavior.

    PubMed

    Gezici, Orhan; Kara, Hüseyin

    2011-09-15

    The stationary phase characteristics of the material obtained through immobilization of humic acid (HA) to aminopropyl silica (APS) via amide-bond formation were investigated. The material was characterized in terms of elemental analysis, FTIR, thermogravimetric analyses, pH point of zero charge measurements, potentiometric titrations, and contact angle measurements. Amount of HA bonded to APS was determined from the elemental analysis results, and found as 170 mgHA/gAPS. Stability of the material was studied in aqueous media at different pH values, and amount of HA released at pH=8 did not exceed 2% of the total immobilized HA. Stationary phase characteristics of the well-characterized material were investigated in an HPLC system by using some low-molecular weight polar compounds (i.e. some nucleosides and nucleobases) as test solutes. Effect of some experimental variables such as column conditioning, composition of mobile phase, and temperature on the chromatographic behavior of the studied compounds was studied. Role of ammonium solutions at different pH values on retentive properties of the species was also studied. Retention factors (k') versus volume percentage of organic modifier exhibited a U-curve, which was evaluated as an indication for RPLC/HILIC mixed-mode behavior of the stationary phase. Orthogonality between RPLC and HILIC modes was analyzed through geometric approach, and found as 48.5%. Base-line separation for the studied groups of compounds was achieved under each studied mode, and some differentiations were observed in elution order of the compounds depending on the HPLC mode applied. Chromatograms recorded under RPLC and HILIC modes were compared with those recorded on APS under similar conditions, and thus the influence/importance of HA immobilization process was evaluated in detail. In light of the obtained results, immobilized HA is represented as a useful stationary phase for HPLC separations. Copyright © 2011 Elsevier B.V. All rights

  6. Effect of humic acid on the sorption of perfluorooctane sulfonate (PFOS) and perfluorobutane sulfonate (PFBS) on boehmite.

    PubMed

    Wang, Fei; Shih, Kaimin; Leckie, James O

    2015-01-01

    The sorption of PFOS and PFBS on boehmite was significantly retarded by the competitive sorption of humic acid (HA), implying that PFOS and PFBS are likely more mobile in water and groundwater systems enriched with HA. The sorption behavior of PFOS and PFBS on the HA-modified boehmite surface were also found to differ due to their different chain lengths. For a partially HA-modified boehmite surface, the isotherm study showed that PFOS had a much higher maximum sorption capacity than PFBS and that PFOS might possess additional surface interactions besides electrostatic interaction. For a HA-saturated boehmite, a linear sorption isotherm was found for PFOS while nearly no PFBS sorption was observed. This indicates that sorption behavior between PFOS and the sorbed HA on boehmite was dominated by hydrophobic interactions, instead of electrostatic interaction. In addition, a conceptual model combining hydrophobic and electrostatic interaction was established to explain the sorption behavior of PFOS and PFBS on HA-modified boehmite. Finally, the results revealed that the sorption of PFOS and PFBS on HA-modified boehmite is pH-dependent. The neutralization of negative sites on HA-modified boehmite reduced the electrostatic repulsion and enhanced the partitioning of PFBS on the sorbed HA. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Neuroprotective effect of humic Acid on focal cerebral ischemia injury: an experimental study in rats.

    PubMed

    Ozkan, Adile; Sen, Halil Murat; Sehitoglu, Ibrahim; Alacam, Hasan; Guven, Mustafa; Aras, Adem Bozkurt; Akman, Tarik; Silan, Coşkun; Cosar, Murat; Karaman, Handan Isin Ozisik

    2015-02-01

    Stroke is still a major cause of death and permanent neurological disability. As humic acids are well-known antioxidant molecules, the purpose of this study was to investigate the potential neuroprotective effects of humic acid in a focal cerebral ischemia model. Twenty-four rats were divided equally into three groups. A middle cerebral artery occlusion model was performed in this study where control (group II) and humic acid (group III) were administered intraperitoneally following an ischemic experimental procedure. Group I was evaluated as sham. Malondialdehyde (MDA), superoxide dismutase (SOD), and nuclear respiratory factor-1 (NRF-1) levels were analyzed biochemically on the right side of the ischemic cerebral hemisphere, while ischemic histopathological studies were completed on the left side to investigate the antioxidant status. Biochemical results showed that SOD and NRF-1 levels were significantly increased in the humic acid group (III) compared with the control group (II) while MDA levels were significantly decreased. On histopathological examination, cerebral edema, vacuolization, degeneration, and destruction of neural elements were decreased in the humic acid group (III) compared with the control group (II). Cerebral ischemia was attenuated by humic acid administration. These observations indicate that humic acid may have potential as a therapeutic agent in cerebral ischemia by preventing oxidative stress.

  8. Evaluation of a proposed standardized analytical method for the determination of humic and fulvic acids in commercial products

    USDA-ARS?s Scientific Manuscript database

    A constraint to growth of the commercial humic products industry has been the lack of a widely accepted procedure for determining humic acid and fulvic acid concentrations of the products, which has raised regulatory issues. On behalf of the U.S.-based Humic Products Trade Association, we developed ...

  9. Effects of heating on composition, degree of darkness, and stacking nanostructure of soil humic acids.

    PubMed

    Katsumi, Naoya; Yonebayashi, Koyo; Okazaki, Masanori

    2016-01-15

    Wildfires and prescribed burning can affect both the quality and the quantity of organic matter in soils. In this study, we investigated qualitative and quantitative changes of soil humic substances in two different soils (an Entisol from a paddy field and an Inceptisol from a cedar forest) under several controlled heating conditions. Soil samples were heated in a muffle furnace at 200, 250, or 300 °C for 1, 3, 5, or 12h. The humic acid and fulvic acid contents of the soil samples prior to and after heating were determined. The degree of darkness, elemental composition, carbon and nitrogen stable isotope ratios, (13)C nuclear magnetic resonance spectra, and X-ray diffraction patterns of humic acids extracted from the soils before and after heating were measured. The proportion of humic acids in total carbon decreased with increasing heating time at high temperature (300 °C), but increased with increasing heating time at ≤ 250 °C. The degree of darkness of the humic acids increased with increasing heating time and temperature. During darkening, the H/C atomic ratios, the proportion of aromatic C, and the carbon and nitrogen stable isotope ratios increased, whereas the proportions of alkyl C and O-alkyl C decreased. X-ray diffraction analysis verified that a stacking nanostructure developed by heating. Changes in the chemical structure of the humic acids from the heated soils depended on the type of soil. The major structural components of the humic acids from the heated Entisol were aromatic C and carboxylic C, whereas aliphatic C, aromatic C, and carboxylic C structural components were found in the humic acids from the heated Inceptisol. These results suggest that the heat-induced changes in the chemical structure of the humic acids depended on the source plant. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. An experimental and modeling study of humic acid concentration effect on H(+) binding: Application of the NICA-Donnan model.

    PubMed

    Vidali, Roza; Remoundaki, Emmanouela; Tsezos, Marios

    2009-11-15

    Humic substances are the most abundant components of the colloidal and the dissolved fraction of natural organic matter (NOM) and they are characterized by a strong binding capacity for both metals and organic pollutants, affecting their mobility and bioavailability. The understanding of the humic acidic character is the first necessary step for the study of the mechanisms of binding of other positively charged soluble metal species by humic molecules. The present work, which constitutes part of the Ph.D. thesis of Roza Vidali, reports results on the influence of the concentration of humic acids on the binding of protons obtained through both an experimental and a modeling approach. A reference purified peat humic acid (PPHA) isolated by the International Humic Substances Society (IHSS) and a humic acid from a Greek soil (GHA) were experimentally studied at various humic acid concentrations, ranging from 20 to 200mgL(-1). The proton binding isotherms obtained at different humic acid concentrations have shown that proton binding is dependent on the concentration of both humic acids. Proton binding experimental data were fitted to the NICA-Donnan model and the model parameter values were calculated for humic acid concentrations of 20 and >or=100mgL(-1). The results obtained for the NICA-Donnan parameters at humic acid concentrations >or=100mgL(-1) are in excellent agreement with those reported in the literature. However, these model parameter values cannot be used for modeling and predicting cation binding in natural aquatic systems, where humic acid concentrations are much lower. Two sets of the NICA-Donnan parameters are reported: one for humic acid concentrations of >or=100mgL(-1) and one for humic acid concentration of 20mgL(-1). The significance of the parameters values for each concentration level is also discussed.

  11. Effects of Humic Acids Isolated from Peat of Various Origin on in Vitro Production of Nitric Oxide: a Screening Study.

    PubMed

    Trofimova, E S; Zykova, M V; Ligacheva, A A; Sherstoboev, E Yu; Zhdanov, V V; Belousov, M V; Yusubov, M S; Krivoshchekov, S V; Danilets, M G; Dygai, A M

    2016-09-01

    A screening study of biological activity of native humic acids isolated from peat was performed; several physical and chemical parameters of their structures were studied by UV- and infrared spectroscopy. Spectroscopy yielded similar shape of light absorption curves of humic acids of different origin, which can reflect similarity of general structural principles of these substances. Alkaline humic acids have more developed system of polyconjugation, while molecular structures of pyrophosphate humic acids were characterized by higher aromaticity and condensation indexes. Biological activity of the studied humic acids was assessed by NO-stimulating capacity during their culturing with murine peritoneal macrophages in a wide concentration range. It was shown that due to dose-dependent enhancement of NO production humic acids can change the functional state of macrophages towards development of pro-inflammatory properties. These changes were associated with high activity of humic acids isolated by pyrophosphate extraction, which allows considering effects of isolation method on biological activity.

  12. Mitigation of Humic Acid Inhibition in Anaerobic Digestion of Cellulose by Addition of Various Salts.

    PubMed

    Azman, Samet; Khadem, Ahmad F; Zeeman, Grietje; van Lier, Jules B; Plugge, Caroline M

    2015-03-25

    Humic compounds are inhibitory to the anaerobic hydrolysis of cellulosic biomass. In this study, the impact of salt addition to mitigate the inhibitory effects of humic compounds was investigated. The experiment was conducted using batch tests to monitor the anaerobic hydrolysis of cellulose in the presence of humic acid. Sodium, potassium, calcium, magnesium and iron salts were tested separately for their efficiency to mitigate humic acid inhibition. All experiments were done under mesophilic conditions (30 °C) and at pH 7. Methane production was monitored online, using the Automatic Methane Potential Test System. Methane production, soluble chemical oxygen demand and volatile fatty acid content of the samples were measured to calculate the hydrolysis efficiencies. Addition of magnesium, calcium and iron salts clearly mitigated the inhibitory effects of humic acid and hydrolysis efficiencies reached up to 75%, 65% and 72%, respectively, which were similar to control experiments. Conversely, potassium and sodium salts addition did not mitigate the inhibition and hydrolysis efficiencies were found to be less than 40%. Mitigation of humic acid inhibition via salt addition was also validated by inductively coupled plasma atomic emission spectroscopy analyses, which showed the binding capacity of different cations to humic acid.

  13. Mitigation of Humic Acid Inhibition in Anaerobic Digestion of Cellulose by Addition of Various Salts

    PubMed Central

    Azman, Samet; Khadem, Ahmad F.; Zeeman, Grietje; van Lier, Jules B.; Plugge, Caroline M.

    2015-01-01

    Humic compounds are inhibitory to the anaerobic hydrolysis of cellulosic biomass. In this study, the impact of salt addition to mitigate the inhibitory effects of humic compounds was investigated. The experiment was conducted using batch tests to monitor the anaerobic hydrolysis of cellulose in the presence of humic acid. Sodium, potassium, calcium, magnesium and iron salts were tested separately for their efficiency to mitigate humic acid inhibition. All experiments were done under mesophilic conditions (30 °C) and at pH 7. Methane production was monitored online, using the Automatic Methane Potential Test System. Methane production, soluble chemical oxygen demand and volatile fatty acid content of the samples were measured to calculate the hydrolysis efficiencies. Addition of magnesium, calcium and iron salts clearly mitigated the inhibitory effects of humic acid and hydrolysis efficiencies reached up to 75%, 65% and 72%, respectively, which were similar to control experiments. Conversely, potassium and sodium salts addition did not mitigate the inhibition and hydrolysis efficiencies were found to be less than 40%. Mitigation of humic acid inhibition via salt addition was also validated by inductively coupled plasma atomic emission spectroscopy analyses, which showed the binding capacity of different cations to humic acid. PMID:28955013

  14. Effect of molecular weight of hyaluronic acid (HA) on viscoelasticity and particle texturing feel of HA dermal biphasic fillers.

    PubMed

    Chun, Cheolbyong; Lee, Deuk Yong; Kim, Jin-Tae; Kwon, Mi-Kyung; Kim, Young-Zu; Kim, Seok-Soon

    2016-01-01

    Hyaluronic acid (HA) dermal biphasic fillers are synthesized for their efficacy in correcting aesthetic defects such as wrinkles, scars and facial contouring defects. The fillers consist of crosslinked HA microspheres suspended in a noncrosslinked HA. To extend the duration of HAs within the dermis and obtain the particle texturing feel, HAs are crosslinked to obtain the suitable mechanical properties. Hyaluronic acid (HA) dermal biphasic fillers are prepared by mixing the crosslinked HA microspheres and the noncrosslinked HAs. The elastic modulus of the fillers increased with raising the volume fraction of the microspheres. The mechanical properties and the particle texturing feel of the fillers made from crosslinked HA (1058 kDa) microspheres suspended in noncrosslinked HA (1368 kDa) are successfully achieved, which are adequate for the fillers. Dermal biphasic HA fillers made from 1058 kDa exhibit suitable elastic moduli (211 to 420 Pa) and particle texturing feel (scale 7 ~ 9).

  15. Environmentally relevant concentrations of aminopolycarboxylate chelating agents mobilize Cd from humic acid.

    PubMed

    North, Ashley E; Sarpong-Kumankomah, Sophia; Bellavie, Andrew R; White, Wade M; Gailer, Jürgen

    2017-07-01

    Although Cd is a pollutant of public health relevance, many dietary sources from which it can be absorbed into human tissues remain unknown. While it is well established that the biogeochemical cycle of Cd involves its complexation with environment-derived ligands (e.g., humic acids, HAs) and anthropogenic ones (e.g., chelating agents, CAs), the interaction of Cd with both of these ligands is less well understood. To gain insight, a HA-Cd complex was injected on a size-exclusion chromatography (SEC) column coupled on-line with a flame atomic absorption spectrometer (FAAS) using 10mmol/L Tris buffer (pH8.0) as the mobile phase. This approach allowed us to observe the intact HA-Cd complex and the retention behavior of Cd as a function of 2-20μmol/L concentrations of ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA) or methylglycinediacetic acid (MGDA) that were added to the mobile phase. An increase of the retention time of Cd was indicative of a partial or complete abstraction of Cd from HA. Our results revealed that all CAs abstracted Cd from the HA-Cd complex at concentrations of 5μmol/L, while MGDA and DTPA were effective at 2μmol/L. The bioavailability of some of the on-column formed CA-Cd complexes explains the previously reported increased accumulation of Cd in periphyton in the ecosystem downstream of wastewater treatment plants. In addition, our results imply that the use of effluents which contain CAs and Cd for the irrigation of food crops can introduce Cd into the food supply and compromise food safety. Copyright © 2017. Published by Elsevier B.V.

  16. Impact of humic/fulvic acid on the removal of heavy metals from aqueous solutions using nanomaterials: a review.

    PubMed

    Tang, Wang-Wang; Zeng, Guang-Ming; Gong, Ji-Lai; Liang, Jie; Xu, Piao; Zhang, Chang; Huang, Bin-Bin

    2014-01-15

    Nowadays nanomaterials have been widely used to remove heavy metals from water/wastewater due to their large surface area and high reactivity. Humic acid (HA) and fulvic acid (FA) exist ubiquitously in aquatic environments and have a variety of functional groups which allow them to complex with metal ions and interact with nanomaterials. These interactions can not only alter the environmental behavior of nanomaterials, but also influence the removal and transportation of heavy metals by nanomaterials. Thus, the interactions and the underlying mechanisms involved warrant specific investigations. This review outlined the effects of HA/FA on the removal of heavy metals from aqueous solutions by various nanomaterials, mainly including carbon-based nanomaterials, iron-based nanomaterials and photocatalytic nanomaterials. Moreover, mechanisms involved in the interactions were discussed and potential environmental implications of HA/FA to nanomaterials and heavy metals were evaluated. © 2013.

  17. Sorption-desorption of imidacloprid onto a lacustrine Egyptian soil and its clay and humic acid fractions.

    PubMed

    Kandil, Mahrous M; El-Aswad, Ahmed F; Koskinen, William C

    2015-01-01

    Sorption-desorption of the insecticide imidacloprid 1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2-imidazolidinimine onto a lacustrine sandy clay loam Egyptian soil and its clay and humic acid (HA) fractions was investigated in 24-h batch equilibrium experiments. Imidacloprid (IMDA) sorption-desorption isotherms onto the three sorbents were found to belong to a non-linear L-type and were best described by the Freundlich model. The value of the IMDA adsorption distribution coefficient, Kd(ads), varied according to its initial concentration and was ranged 40-84 for HA, 14-58 for clay and 1.85-4.15 for bulk soil. Freundlich sorption coefficient, Kf(ads), values were 63.0, 39.7 and 4.0 for HA, clay and bulk soil, respectively. The normalized soil Koc value for imidacloprid sorption was ∼800 indicating its slight mobility in soils. Nonlinear sorption isotherms were indicated by 1/n(ads) values <1 for all sorbents. Values of the hysteresis index (H) were <1, indicating the irreversibility of imidacloprid sorption process with all tested sorbents. Gibbs free energy (ΔG) values indicated a spontaneous and physicosorption process for IMDA and a more favorable sorption to HA than clay and soil. In conclusion, although the humic acid fraction showed the highest capacity and affinity for imidacloprid sorption, the clay fraction contributed to approximately 95% of soil-sorbed insecticide. Clay and humic acid fractions were found to be the major two factors controlling IMDA sorption in soils. The slight mobility of IMDA in soils and the hysteresis phenomenon associated with the irreversibility of its sorption onto, mainly, clay and organic matter of soils make its leachability unlikely to occur.

  18. Humic Acid Effects on the Transport of Colloidal Particles in Unsaturated Porous Media: Humic Acid Dosage, pH, and Ionic Strength Dependence

    NASA Astrophysics Data System (ADS)

    Morales, V. L.; Gao, B.; Steenhuis, T. S.

    2008-12-01

    Soil colloids and biocolloids can facilitate contaminant transport within the soil profile through the complexation of pollutants previously thought to have limited mobility. Dissolved organic substances are qualitatively known to alter the behavior of colloids and surface chemistry of soil particles in aquatic environments when adsorbed to their surfaces. Specifically, it has been observed that even small amounts of adsorbed humic acids result in a pronounced increase in colloid mobility in saturated porous systems, presumably by a combination of electrostatic and steric stabilization. However, the degree to which adsorbed humic acids stabilize colloidal suspension is highly sensitive to the system's solution chemistry; mainly in terms of pH, ionic strength, and metal ions present. The objective of this study is to expound quantitatively on the role that combined stabilizing and destabilizing solution chemistry components have on humic acid-colloid transport in unsaturated media by isolating experimentally some underlying mechanisms that regulate colloid transport in realistic aquatic systems. We hypothesize that in chemically heterogeneous porous media, with ionic strength values above 0 and pH ranges from 4 to 9, the effect of humic acid on colloid suspensions cannot be simply characterized by increased stability and mobility. That a critical salt concentration must exists for a given humic acid concentration and pH, above which the network of humic acid collapses by forming coordination complexes with other suspended or adsorbed humic acids, thus increasing greatly the retention of colloids in the porous medium by sweep flocculation. In addition, capillary forces in unsaturated media may contribute further to overcome repulsive forces that prevent flocculation of humic acid-colloid complexes. The experimental work in this study will include: jar tests to determine critical solution concentration combinations for desired coagulation/flocculation rates, column

  19. Effects of peat fires on the characteristics of humic acid extracted from peat soil in Central Kalimantan, Indonesia.

    PubMed

    Yustiawati; Kihara, Yusuke; Sazawa, Kazuto; Kuramitz, Hideki; Kurasaki, Masaaki; Saito, Takeshi; Hosokawa, Toshiyuki; Syawal, M Suhaemi; Wulandari, Linda; Hendri I; Tanaka, Shunitz

    2015-02-01

    When peat forest fires happen, it leads to burn soil and also humic acids as a dominant organic matter contained in peat soil as well as the forest. The structure and properties of humic acids vary depending on their origin and environment, therefore the transformation of humic acid is also diverse. The impacts of the peat fires on peat soil from Central Kalimantan, Indonesia were investigated through the characterization of humic acids, extracted from soil in burnt and unburnt sites. The characterization of humic acids was performed by elemental composition, functional groups, molecular weight by HPSEC, pyrolysate compounds by pyrolysis-GC/MS, fluorescence spectrum by 3DEEM spectrofluorometer, and thermogravimetry. The elemental composition of each humic substance indicated that the value of H/C and O/C of humic acids from burnt sites were lower than that from unburnt sites. The molecular weight of humic acids from burnt sites was also lower than that from unburnt sites. Pyrolysate compounds of humic acids from unburnt sites differed from those of humic acids from burnt soil. The heating experiment showed that burning process caused the significant change in the properties of humic acids such as increasing the aromaticity and decreasing the molecular weight.

  20. Effects of long-term fertilization on soil humic acid composition and structure in Black Soil

    PubMed Central

    Zhang, Jiuming; Wang, Jingkuan; An, Tingting; Wei, Dan; Chi, Fengqin; Zhou, Baoku

    2017-01-01

    The composition and structure of humic acid (HA) can be affected by fertilization, but the short-term effects are difficult to detect using traditional analysis methods. Using a 35-year long-term experiment in Black Soil, the molecular structure of HA was analyzed with Fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance spectroscopy (NMR), and fluorescence spectroscopy. Variation in HA was analyzed after long-term fertilization, including fertilization with manure (M), inorganic N, P and K fertilizer (NPK), manure combined with inorganic N, P, and K fertilizer (MNPK), and a no-fertilizer control (CK). The application of each fertilizer treatment increased crop yields compared with the CK treatment, and the MNPK treatment increased crop yield the most. The ratio of main IR absorption peak of HA at 2,920 cm−1 compared with the peak at 2,850 cm−1 (2920/2850) was higher in the NPK and MNPK treatments compared with the CK treatment. The application of manure (MNPK and M treatments) increased the ratio of hydrogen to carbon (H/C) in HA, and raised the ratio of the main IR absorption peak of HA at 2920 cm−1 to that at 1720 cm−1 (2920/1720). Manure treatments also raised the ratio of aliphatic carbon (C) to aromatic C, alkyl C to alkoxy C and hydrophobic C to hydrophilic C and the fluorescence index (f 450/500), but decreased the degree of aromatization of HA, when compared with the CK treatment. The ratio between each type of C in HA was similar among all the fertilizer treatments, but NPK had a lower ratio of H/C and a lower content of aliphatic C compared with the CK treatment. These results indicated that the molecular structure of HA in Black Soil tends to be aliphatic, simpler, and younger after the application of manure. While the application of inorganic fertilizers increased in the degree of condensation of HA and made HA structure complicated. The application of manure alone or combined with inorganic fertilizers may be an

  1. The stabilization of tannery sludge and the character of humic acid-like during low temperature pyrolysis.

    PubMed

    Ma, Hongrui; Gao, Mao; Hua, Li; Chao, Hao; Xu, Jing

    2015-11-01

    Tannery sludge contained plenty of organic matter, and the organic substance stability had direct impact on its derived chars' utilization. In this paper, the stabilization of tannery sludge and the variation of humic acid-like (HAL) extracted by different methods were investigated in a magnetic stirring reactor under low temperature pyrolysis of 100-400 °C. Results showed that the aromatic structure of pyrolysis chars increased with the increase of temperature and time. The char contained highly aromatic structure and relatively small dissolved organic matters (DOM) at 300 °C. The similar behaviors appeared in two HAL series by different extraction methods. The N content, H/C value, and aliphatic structures of HAL decreased with the increase of pyrolysis temperature, while the C/N value and aromatic structures increased with the rise of pyrolysis temperature. The composition and functional groups of HAL were similar with the purchased humic acid (HA). The fluorescence spectra revealed that two main peaks were found at Ex/Em = 239/363-368 nm and 283/359-368 nm in each HAL series from raw and 100 °C pyrolysis tannery sludge, representing a protein-like matter. The new peak appeared at Ex/Em = 263-283/388 nm in each HAL series from 200 °C pyrolysis tannery sludge-represented humic acid-like matter. The fluorescence intensity increased strongly compared to the other two peak intensity. Therefore, the humification of organic matter was increased by pyrolyzing. Notably, the HAL from 200 °C pyrolysis tannery sludge contained simple molecular structure, and the polycondensation increased but with a relative lower humification degree compared to soil HAL and purchased HA. Therefore, the sludge needs further oxidation. The humic substance was negligible by direct extraction when the temperature was 300 and 400 °C.

  2. Effect of dissolved humic acid on the Pb bioavailability in soil solution and its consequence on ecological risk.

    PubMed

    An, Jinsung; Jho, Eun Hea; Nam, Kyoungphile

    2015-04-09

    Current risk characterization in ecological risk assessment does not consider bioavailability of heavy metals, which highly depends on physicochemical properties of environmental media. This study was set to investigate the effect of humic acid (HA), used as a surrogate of organic matter, on Pb toxicity and the subsequent effect on risk characterization in ecological risk assessment. Pb toxicity was assessed using Microtox(®) in the presence and absence of two different forms of HA, particulate HA (pHA) and dissolved HA (dHA). With increasing contact time, the EC10 values increased (i.e., the toxic effects decreased) and the dissolved Pb concentrations of the filtrates decreased. The high correlation (R = 0.88, p < 0.001) between toxic effects determined using both the mixture and its filtrate as exposure media leads us to conclude that the Pb toxicity highly depends on the soluble fraction. Also, reduced Pb toxicity with increasing dHA concentrations, probably due to formation of Pb-dHA complexes, indicated that Pb toxicity largely comes from free Pb ions. Overall, this study shows the effect of HA on metal toxicity alleviation, and emphasizes the need for incorporating the bioavailable heavy metal concentrations in environmental media as a point of exposure in ecological risk assessment. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Hydrothermal Alteration Promotes Humic Acid Formation in Sediments: A Case Study of the Central Indian Ocean Basin

    NASA Astrophysics Data System (ADS)

    Sarma, Nittala S.; Kiran, Rayaprolu; Rama Reddy, M.; Iyer, Sridhar D.; Peketi, A.; Borole, D. V.; Krishna, M. S.

    2018-01-01

    Anomalously high concentrations of humic-rich dissolved organic matter (DOM) in extant submarine hydrothermal vent plumes traveled far from source are increasingly being reported. This DOM, able to mobilize trace metals (e.g., Fe2+) has been hypothesized as originating from organic matter produced by thermogenic bacteria. To eliminate a possible abiogenic origin of this DOM, study is required of well-preserved organic compounds that can be attributed to thermogenic bacteria. The Central Indian Ocean Basin (CIOB) is part of a diffuse plate boundary and an intraplate deformation zone. Coarse fraction (>63 µ) characteristics, mineralogy, magnetic susceptibility, and geochemistry were examined in sediments of a core raised close to a north-south fracture zone near the Equator. Two horizons of distinctly brown-colored sediments were shown as hydrothermally altered from their charred fragments and geochemistry (CaCO3, Corg, Ti/Al, Al/(Al + Fe + Mn), Sr/Ba, Mg/Li, Mn micronodules, Fe/Mn). We examined whether humic substances were preserved in these sediments, and if so whether their carbon isotope distribution would support their hydrothermal origin. Alkali extraction of sediments afforded humic acids (HA) in yields up to 1.2% in the brown sediments. The remaining portions of the core had nil or low concentrations of HA. The carbon of hydrothermal HA is isotopically heavier (average δ13C, ˜ -16.3‰) compared to nonhydrothermal HA (-18.1‰), suggesting that they were probably formed from organic matter that remained after elimination of lighter carbon enriched functional groups during diagenesis. The results provide compelling evidence of HA formation from lipids originating from thermogenic bacteria.

  4. Microbial reduction of Fe(III)-bearing clay minerals in the presence of humic acids

    NASA Astrophysics Data System (ADS)

    Liu, Guangfei; Qiu, Shuang; Liu, Baiqing; Pu, Yiying; Gao, Zhanming; Wang, Jing; Jin, Ruofei; Zhou, Jiti

    2017-03-01

    Both Fe(III)-bearing clay minerals and humic acids (HAs) are abundant in the soils and sediments. Previous studies have shown that bioreduction of structural Fe(III) in clay minerals could be accelerated by adding anthraquinone compound as a redox-active surrogate of HAs. However, a quinoid analogue could not reflect the adsorption and complexation properties of HA, and little is known about the effects of real HAs at environmental concentration on bioreduction of clay minerals. Here, it was shown that 10-200 mg l-1 of natural or artificially synthesized HAs could effectively stimulate the bioreduction rate and extent of Fe(III) in both iron-rich nontronite NAu-2 and iron-deficient montmorillonite SWy-2. After adsorption to NAu-2, electron-transfer activities of different HA fractions were compared. Additionally, Fe(II) complexation by HAs also contributed to improvement of clay-Fe(III) bioreduction. Spectrosopic and morphological analyses suggested that HA addition accelerated the transformation of NAu-2 to illite, silica and siderite after reductive dissolution.

  5. Cadmium Phytoavailability and Enzyme Activity under Humic Acid Treatment in Fluvo-aquic Soil

    NASA Astrophysics Data System (ADS)

    Liu, Borui; Huang, Qing; Su, Yuefeng

    2018-01-01

    A pot experiment was conducted to investigate the cadmium (Cd) availability to pakchois (Brassica chinensis L.) as well as the enzyme activities in fluvo-aquic soil under humic acid treatment. The results showed that the phytoavailability of Cd in soil decreased gradually as humic acid concentration rose (0 to 12 g·kg-1), while the activities of urease (UE), alkaline phosphatase (ALP) and catalase (CAT) kept increasing (P < 0.05). The correlation analysis indicated that humic acid was effective for reducing the devastation to soil enzymes due to the Cd pollution. In conclusion, humic acid is effective for the reduction of both Cd phytoavailability and the damage to enzyme activities due to Cd pollution in fluvo-aquic soil

  6. Study of coagulation processes of selected humic acids under copper ions influence*

    NASA Astrophysics Data System (ADS)

    Boguta, Patrycja; Sokolowska, Zofia

    2013-04-01

    Humic acids have limited sorption capacity and big dose of metal or other mineral component which can be sorbed on humic acids, can cause saturation of negative, surface charge of humic acids leading to destabilization of dissolved humic acids compounds. Destabilisation can be observed as coagulation and floculation proces of humic acids. However there are a lot of mechanisms which causing precipitation of humic acids. Thereby, in order to full description of coagulation process, different methods should be applied. Ordinarily, humic acids coagulation is studied by measurement of absorbance, transmittance or carbon loss in solution. Meanwhile, very significant information is also variation of metal content in soil solution and information whether metal goes to precipitate together with humic acids or stays in dissolved form in solution. So, that, from one side, processes of stronger accumulation of metal can lead to soil degradation and micronutrient deficiency for plants. However, there is also possibility to stay metal in solution in toxic and bioavailable form for plants. Main aim of this paper was to study coagulation process of different humic acids extracted from mucking peats under copper ions influence at adjusted pH to 5. In order to this, four peaty-muck soils were taken from selected places in east part of Poland (meadows and river valleys). These soils differed by humification degree, secondary transformation, density and pH. At next step, humic acids were extracted from soils using sodium hydroxide (NaOH) extractant. After exact purification by washing with HF-HCl mixture and water, humic acids were liofilized. Solutions of humic acids were prepared at concentration 40 mg/dm3 with addition of different amount of copper ions to obtain final concentration of Cu(II) ranged from 0-40mg/dm3. After 24 hours solutions were investigated using measurements of absorbance at 470nm (UV-VIS spectrometer Jasco V-530), measurements of organic carbon in solution

  7. [Effect of humic acids on migration and transformation of NH4(+) -N in saturated aquifer].

    PubMed

    Meng, Qing-Jun; Zhang, Yan; Feng, Qi-Yan; Zhang, Shuang-Sheng

    2011-11-01

    Isothermal adsorption experiment was used to study the adsorbing process of NH4(+) -N in quartz sands under the conditions with and without humic acid; the Langmuir and Freundlich equations were used to fit the absorption result and the maximum adsorption capacity of NH4(+) -N by quarts sands was calculated. Through the soil column experiments, the concentration of NH4(+) -N, NO3(-) -N and NO2(-) -N in effluent water in the tested soil column was investigated, and the effect of humic acid on migration and transformation of NH4(+) -N in saturated aquifer was analyzed, and Pseudo-second-order Kinetics Equation and Two-step Adsorption Kinetics Rate Equation were applied to fit the kinetic processes. The results showed that both Langmuir and Freundlich models can well describe the isothermal adsorption process of NH4(+) -N on the surface of quartz sands, which means that NH4(+) -N adsorbed by the quartz sand was mainly in the form of monolayer adsorption. The humic acid could increase the adsorption capacity of NH4(+) -N on quartz sand, and the saturated adsorption capacity was 0.354 mg x g(-1) under the condition with humic acid and 0.205 mg x g(-1) with the absence of humic acid. The experiment indicated that humic acid increased the adsorption capacity of NH4(+) -N on the surface of quartz sand by increasing adsorption space in the initial stage. After saturation, humic acid influenced the migration and transformation of NH4(+) -N to NO3(-) -N and NO2(-) -N probably through providing carbon source and energy for microorganisms such as nitrifying bacteria and then resulting in lower NH4(+) -N concentration in effluent water. Both Pseudo-second-order Kinetics Equation and Two-step Adsorption Kinetics Rate Equations can well describe the process of NH4(+) -N adsorption kinetics on quartz sand (R2 = 0.997 7 and R2 = 0.998 1 with humic acid; R2 = 0.992 3 and R2 = 0.994 4 without humic acid), indicating that this process was chemical adsorption. By comparing the

  8. Humic acids enhance the microbially mediated release of sedimentary ferrous iron.

    PubMed

    Chang, Chun-Han; Wei, Chia-Cheng; Lin, Li-Hung; Tu, Tzu-Hsuan; Liao, Vivian Hsiu-Chuan

    2016-03-01

    Iron (Fe) is an essential element for many organisms, but high concentrations of iron can be toxic. The complex relation between iron, arsenic (As), bacteria, and organic matter in sediments and groundwater is still an issue of environmental concern. The present study addresses the effects of humic acids and microorganisms on the mobilization of iron in sediments from an arsenic-affected area, and the microbial diversity was analyzed. The results showed that the addition of 50, 100, and 500 mg/L humic acids enhanced ferrous iron (Fe(II)) release in a time-dependent and dose-dependent fashion under anaerobic conditions. A significant increase in the soluble Fe(II) concentrations occurred in the aqueous phases of the samples during the first 2 weeks, and aqueous Fe(II) reached its maximum concentrations after 8 weeks at the following Fe(II) concentrations: 28.95 ± 1.16 mg/L (original non-sterilized sediments), 32.50 ± 0.71 mg/L (50 mg/L humic acid-amended, non-sterilized sediments), 37.50 ± 1.85 mg/L (100 mg/L humic acid-amended, non-sterilized sediments), and 39.00 ± 0.43 mg/L (500 mg/L humic acid-amended, non-sterilized sediments). These results suggest that humic acids can further enhance the microbially mediated release of sedimentary iron under anaerobic conditions. By contrast, very insignificant amounts of iron release were observed from sterilized sediments (the abiotic controls), even with the supplementation of humic acids under anaerobic incubation. In addition, the As(III) release was increased from 50 ± 10 μg/L (original non-sterilized sediments) to 110 ± 45 μg/L (100 mg/L humic acid-amended, non-sterilized sediments) after 8 weeks of anaerobic incubation. Furthermore, a microbial community analysis indicated that the predominant class was changed from Alphaproteobacteria to Deltaproteobacteria, and clearly increased populations of Geobacter sp., Paludibacter sp., and Methylophaga sp. were found after adding humic acids

  9. Effect of humic acids with different characteristics on fermentative short-chain fatty acids production from waste activated sludge.

    PubMed

    Liu, Kun; Chen, Yinguang; Xiao, Naidong; Zheng, Xiong; Li, Mu

    2015-04-21

    Recently, the use of waste activated sludge to bioproduce short-chain fatty acids (SCFA) has attracted much attention as the sludge-derived SCFA can be used as a preferred carbon source to drive biological nutrient removal or biopolymer (polyhydroxyalkanoates) synthesis. Although large number of humic acid (HA) has been reported in sludge, the influence of HA on SCFA production has never been documented. This study investigated the effects on sludge-derived SCFA production of two commercially available humic acids (referred to as SHHA and SAHA purchased respectively from Shanghai Reagent Company and Sigma-Aldrich) that differ in chemical structure, hydrophobicity, surfactant properties, and degree of aromaticity. It was found that SHHA remarkably enhanced SCFA production (1.7-3.5 folds), while SAHA had no obvious effect. Mechanisms study revealed that all four steps (solubilization, hydrolysis, acidification, and methanogenesis) involved in sludge fermentation were unaffected by SAHA. However, SHHA remarkably improved the solubilization of sludge protein and carbohydrate and the activity of hydrolysis enzymes (protease and α-glucosidase) owing to its greater hydrophobicity and protection of enzyme activity. SHHA also enhanced the acidification step by accelerating the bioreactions of glyceradehyde-3P → d-glycerate 1,3-diphosphate, and pyruvate → acetyl-CoA due to its abundant quinone groups which served as electron acceptor. Further investigation showed that SHHA negatively influenced the activity of acetoclastic methanogens for its competition for electrons and inhibition on the reaction of acetyl-CoA → 5-methyl-THMPT, which caused less SCFA being consumed. All these observations were in correspondence with SHHA significantly enhancing the production of sludge derived SCFA.

  10. Application of a set of complementary techniques to understand how varying the proportion of two wastes affects humic acids produced by vermicomposting

    SciTech Connect

    Fernández-Gómez, Manuel J., E-mail: manuelj.fernandez@eez.csic.es; Nogales, Rogelio; Plante, Alain

    2015-01-15

    Highlights: • A set of techniques was used to characterize humic acids content of vermicomposts. • The properties of the humic acids produced from different waste mixtures were similar. • This set of techniques allowed distinguishing the humic acids of each vermicomposts. • Increasing humic acid contents in initial mixtures would produce richer vermicomposts. - Abstract: A better understanding of how varying the proportion of different organic wastes affects humic acid (HA) formation during vermicomposting would be useful in producing vermicomposts enriched in HAs. With the aim of improving the knowledge about this issue, a variety of analytical techniques [UV–visiblemore » spectroscopic, Fourier transform infrared, fluorescence spectra, solid-state cross-polarization magic-angle spinning (CPMAS) {sup 13}C nuclear magnetic resonance (NMR) spectra, and thermal analysis] was used in the present study to characterize HAs isolated from two mixtures at two different ratios (2:1 and 1:1) of tomato-plant debris (TD) and paper-mill sludge (PS) before and after vermicomposting. The results suggest that vermicomposting increased the HA content in the TD/PS 2:1 and 1:1 mixtures (15.9% and 16.2%, respectively), but the vermicompost produced from the mixture with a higher amount of TD had a greater proportion (24%) of HAs. Both vermicomposting processes caused equal modifications in the humic precursors contained in the different mixtures of TD and PS, and consequently, the HAs in the vermicomposts produced from different waste mixtures exhibited analogous characteristics. Only the set of analytical techniques used in this research was able to detect differences between the HAs isolated from each type of vermicompost. In conclusion, varying the proportion of different wastes may have a stronger influence on the amount of HAs in vermicomposts than on the properties of HAs.« less

  11. A comparative study of ozonation, iron coated zeolite catalyzed ozonation and granular activated carbon catalyzed ozonation of humic acid.

    PubMed

    Gümüş, Dilek; Akbal, Feryal

    2017-05-01

    This study compares ozonation (O 3 ), iron coated zeolite catalyzed ozonation (ICZ-O 3 ) and granular activated carbon catalyzed ozonation (GAC-O 3 ) for removal of humic acid from an aqueous solution. The results were evaluated by the removal of DOC that specifies organic matter, UV 254 absorbance, SUVA (Specific Ultraviolet Absorbance at 254 nm) and absorbance at 436 nm. When ozonation was used alone, DOC removal was 21.4% at an ozone concentration of 10 mg/L, pH 6.50 and oxidation time of 60 min. The results showed that the use of ICZ or GAC as a catalyst increased the decomposition of humic acid compared to ozonation alone. DOC removal efficiencies were 62% and 48.1% at pH 6.5, at a catalyst loading of 0.75 g/L, and oxidation time of 60 min for ICZ and GAC, respectively. The oxidation experiments were also carried out using <100 kDa and <50 kDa molecular size fractions of humic acid in the presence of ICZ or GAC. Catalytic ozonation also yielded better DOC and UV 254 reduction in both <50 kDa and <100 kDa fractions of HA compared to ozonation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Humic acids as electron acceptors for anaerobic microbial oxidation of vinyl chloride and dichloroethene

    USGS Publications Warehouse

    Bradley, P.M.; Chapelle, F.H.; Lovley, D.R.

    1998-01-01

    Anaerobic oxidation of [1,2-14C]vinyl chloride and [1,2- 14C]dichloroethene to 14CO2 under humic acid-reducing conditions was demonstrated. The results indicate that waterborne contaminants can be oxidized by using humic acid compounds as electron acceptors and suggest that natural aquatic systems have a much larger capacity for contaminant oxidation than previously thought.

  13. Dicarboxylic acids generated by thermal alteration of kerogen and humic acids

    NASA Technical Reports Server (NTRS)

    Kawamura, Kimitaka; Kaplan, I. R.

    1987-01-01

    Significant amounts (up to 2 percent of organic geopolymers) of low-molecular-weight (LMW) dicarboxylic acids (C2-C10) have been detected during thermal alteration (270 C, 2 h) of kerogens and humic acids isolated from young or ancient lithified sediments. Their distribution is characterized by the predominance of oxalic acid followed by succinic, fumaric, and methylsuccinic acids. These acids are probably released by the breakdown of macromolecular structures, which have incorporated biogenic organic compounds, including diacids, during early digenesis in sediments. Because of their reactivity, LMW diacids may play geochemically important roles under natural conditions.

  14. Reducing Capacities and Distribution of Redox-Active Functional Groups in Low Molecular Weight Fractions of Humic Acids.

    PubMed

    Yang, Zhen; Kappler, Andreas; Jiang, Jie

    2016-11-15

    Humic substances (HS) are redox-active organic compounds with a broad spectrum of molecular sizes and reducing capacities, that is, number of electrons donated or accepted. However, it is unknown which role the distribution of redox-active functional groups in different molecule sizes plays for HS redox reactions in varying pore sizes microenvironments. We used dialysis experiments to separate bulk humic acids (HA) into low molecular weight fractions (LMWF) and retentate, for example, the remaining HA in the dialysis bag. LMWF accounted for only 2% of the total organic carbon content of the HA. However, their reducing capacities per gram of carbon were up to 33 times greater than either those of the bulk HA or the retentate. For a structural/mechanistic understanding of the high reducing capacity of the LMWF, we used fluorescence spectroscopy. We found that the LWMF showed significant fluorescence intensities for quinone-like functional groups, as indicated by the quinoid π-π* transition, that are probably responsible for the high reducing capacities. Therefore, the small-sized HS fraction can play a major role for redox transformation of metals or pollutants trapped in soil micropores (<2.5 nm diameter).

  15. The Role of Concentration and Solvent Character in the Molecular Organization of Humic Acids.

    PubMed

    Klučáková, Martina; Věžníková, Kateřina

    2016-10-27

    The molecular organization of humic acids in different aqueous solutions was studied over a wide concentration range (0.01-10 g·dm -3 ). Solutions of humic acids were prepared in three different media: NaOH, NaCl, and NaOH neutralized by HCl after dissolution of the humic sample. Potentiometry, conductometry, densitometry, and high resolution ultrasound spectrometry were used in order to investigate conformational changes in the humic systems. The molecular organization of humic acids in the studied systems could be divided into three concentration ranges. The rearrangements were observed at concentrations of ~0.02 g·dm -3 and ~1 g·dm -3 . The first "switch-over point" was connected with changes in the hydration shells of humic particles resulting in changes in their elasticity. The compressibility of water in the hydration shells is less than the compressibility of bulk water. The transfer of hydration water into bulk water increased the total compressibility of the solution, reducing the ultrasonic velocity. The aggregation of humic particles and the formation of rigid structures in systems with concentrations higher than 1 g·dm -3 was detected.

  16. Concept model of the formation process of humic acid-kaolin complexes deduced by trichloroethylene sorption experiments and various characterizations.

    PubMed

    Zhu, Xiaojing; He, Jiangtao; Su, Sihui; Zhang, Xiaoliang; Wang, Fei

    2016-05-01

    To explore the interactions between soil organic matter and minerals, humic acid (HA, as organic matter), kaolin (as a mineral component) and Ca(2+) (as metal ions) were used to prepare HA-kaolin and Ca-HA-kaolin complexes. These complexes were used in trichloroethylene (TCE) sorption experiments and various characterizations. Interactions between HA and kaolin during the formation of their complexes were confirmed by the obvious differences between the Qe (experimental sorbed TCE) and Qe_p (predicted sorbed TCE) values of all detected samples. The partition coefficient kd obtained for the different samples indicated that both the organic content (fom) and Ca(2+) could significantly impact the interactions. Based on experimental results and various characterizations, a concept model was developed. In the absence of Ca(2+), HA molecules first patched onto charged sites of kaolin surfaces, filling the pores. Subsequently, as the HA content increased and the first HA layer reached saturation, an outer layer of HA began to form, compressing the inner HA layer. As HA loading continued, the second layer reached saturation, such that an outer-third layer began to form, compressing the inner layers. In the presence of Ca(2+), which not only can promote kaolin self-aggregation but can also boost HA attachment to kaolin, HA molecules were first surrounded by kaolin. Subsequently, first and second layers formed (with inner layer compression) via the same process as described above in the absence of Ca(2+), except that the second layer continued to load rather than reach saturation, within the investigated conditions, because of enhanced HA aggregation caused by Ca(2+). Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Clarithromycin and tetracycline binding to soil humic acid in the absence and presence of calcium

    NASA Astrophysics Data System (ADS)

    Christl, Iso; Ruiz, Mercedes; Schmidt, J. R.; Pedersen, Joel A.

    2017-04-01

    Many organic micropollutants including antibiotics contain positively charged moieties and are present as organic cations or zwitterions at environmentally relevant pH conditions. In this study, we investigated the pH-, ionic strength-, and concentration-dependent binding of the two antibiotics clarithromycin and tetracycline to dissolved humic acid in the absence and presence of Ca2+. The investigated compounds strongly differ in their chemical speciation. Clarithromycin can be present as neutral and cationic species, only. But tetracycline can form cations, zwitterions as well as anions and is able to form various calcium complexes. The pH-dependence of binding to soil humic acid was observed to be strongly linked to the protonation behavior for both antibiotics. The presence of Ca2+ decreased clarithromycin binding to soil humic acid, but increased tetracycline binding with increasing Ca2+ concentration. The experimental observations were well described with the NICA-Donnan model considering the complete aqueous speciation of antibiotics and allowing for binding of cationic and zwitterionic species to soil humic acid. Our results indicate that clarithromycin is subject to competition with Ca2+ for binding to soil humic acid and that the electrostatic interaction of positively charged tetracycline-Ca complexes with humic acid enhances tetracycline binding in presence of Ca2+ rather than the formation of ternary complexes, except at very low tetracycline concentrations. We conclude that for the description of ionizable organic micropollutant binding to dissolved natural organic matter, the complete speciation of both sorbate and sorbent has to be considered.

  18. Clarithromycin and Tetracycline Binding to Soil Humic Acid in the Absence and Presence of Calcium.

    PubMed

    Christl, Iso; Ruiz, Mercedes; Schmidt, J R; Pedersen, Joel A

    2016-09-20

    Numerous ionizable organic micropollutants contain positively charged moieties at pH values typical of environmental systems. Describing organic cation and zwitterion interaction with dissolved natural organic matter requires explicit consideration of the pH-dependent speciation of both sorbate and sorbent. We studied the pH-, ionic strength-, and concentration-dependent binding of relatively large, organic cations and zwitterions (viz., the antibiotics clarithromycin and tetracycline) to dissolved humic acid in the absence and presence of Ca(2+) and evaluated the ability of the NICA-Donnan model to describe the data. Clarithromycin interaction with dissolved humic acid was well described by the model including the competitive effect of Ca(2+) on clarithromycin binding over a wide range of solution conditions by considering only the binding of the cationic species to low proton-affinity sites in humic acid. Tetracycline possesses multiple ionizable moieties and forms complexes with Ca(2+). An excellent fit to experimental data was achieved by considering tetracycline cation interaction with both low and high proton-affinity sites of humic acid and zwitterion interaction with high proton-affinity sites. In contrast to clarithromycin, tetracycline binding to humic acid increased in the presence of Ca(2+), especially under alkaline conditions. Model calculations indicate that this increase is due to electrostatic interaction of positively charged tetracycline-Ca complexes with humic acid rather than due to the formation of ternary complexes, except at very low TC concentrations.

  19. Enhanced adsorption of humic acids on ordered mesoporous carbon compared with microporous activated carbon.

    PubMed

    Liu, Fengling; Xu, Zhaoyi; Wan, Haiqin; Wan, Yuqiu; Zheng, Shourong; Zhu, Dongqiang

    2011-04-01

    Humic acids are ubiquitous in surface and underground waters and may pose potential risk to human health when present in drinking water sources. In this study, ordered mesoporous carbon was synthesized by means of a hard template method and further characterized by X-ray diffraction, N2 adsorption, transition electron microscopy, elemental analysis, and zeta-potential measurement. Batch experiments were conducted to evaluate adsorption of two humic acids from coal and soil, respectively, on the synthesized carbon. For comparison, a commercial microporous activated carbon and nonporous graphite were included as additional adsorbents; moreover, phenol was adopted as a small probe adsorbate. Pore size distribution characterization showed that the synthesized carbon had ordered mesoporous structure, whereas the activated carbon was composed mainly of micropores with a much broader pore size distribution. Accordingly, adsorption of the two humic acids was substantially lower on the activated carbon than on the synthesized carbon, because of the size-exclusion effect. In contrast, the synthesized carbon and activated carbon showed comparable adsorption for phenol when the size-exclusion effect was not in operation. Additionally, we verified by size-exclusion chromatography studies that the synthesized carbon exhibited greater adsorption for the large humic acid fraction than the activated carbon. The pH dependence of adsorption on the three carbonaceous adsorbents was also compared between the two test humic acids. The findings highlight the potential of using ordered mesoporous carbon as a superior adsorbent for the removal of humic acids. Copyright © 2011 SETAC.

  20. Kinetics and thermodynamics of interaction between sulfonamide antibiotics and humic acids: Surface plasmon resonance and isothermal titration microcalorimetry analysis.

    PubMed

    Xu, Juan; Yu, Han-Qing; Sheng, Guo-Ping

    2016-01-25

    The presence of sulfonamide antibiotics in the environments has been recognized as a crucial issue. Their migration and transformation in the environment is determined by natural organic matters that widely exist in natural water and soil. In this study, the kinetics and thermodynamics of interactions between humic acids (HA) and sulfamethazine (SMZ) were investigated by employing surface plasmon resonance (SPR) combined with isothermal titration microcalorimetry (ITC) technologies. Results show that SMZ could be effectively bound with HA. The binding strength could be enhanced by increasing ionic strength and decreasing temperature. High pH was not favorable for the interaction. Hydrogen bond and electrostatic interaction may play important roles in driving the binding process, with auxiliary contribution from hydrophobic interaction. The results implied that HA existed in the environment may have a significant influence on the migration and transformation of organic pollutants through the binding process. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Environmentally relevant concentration of arsenic trioxide and humic acid promoted tumor progression of human cervical cancer cells: In vivo and in vitro studies.

    PubMed

    Tsai, Min-Ling; Yen, Cheng-Chieh; Lu, Fung-Jou; Ting, Hung-Chih; Chang, Horng-Rong

    2016-09-01

    In a previous study, treatment at higher concentrations of arsenic trioxide or co-exposure to arsenic trioxide and humic acid was found to be inhibited cell growth of cervical cancer cells (SiHa cells) by reactive oxygen species generation. However, treatment at lower concentrations slightly increased cell viability. Here, we investigate the enhancement of progression effects of environmentally relevant concentration of humic acid and arsenic trioxide in SiHa cell lines in vitro and in vivo by measuring cell proliferation, migration, invasion, and the carcinogenesis-related protein (MMP-2, MMP-9, and VEGF-A) expressions. SiHa cells treated with low concentrations of humic acid and arsenic trioxide alone or in co-exposure significantly increased reactive oxygen species, glutathione levels, cell proliferation, scratch wound-healing activities, migration abilities, and MMP-2 expression as compared to the untreated control. In vivo the tumor volume of either single drug (humic acid or arsenic trioxide) or combined drug-treated group was significantly larger than that of the control for an additional 45 days after tumor cell injection on the back of NOD/SCID mice. Levels of MMP-2, MMP-9, and VEGF-A, also significantly increased compared to the control. Histopathologic effects of all tumor cells appeared round in cell shape with high mitosis, focal hyperkeratosis and epidermal hyperplasia in the skin, and some tumor growth in the muscle were observed. Our results may indicate that exposure to low concentrations of arsenic trioxide and humic acid is associated with the progression of cervical cancer. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1121-1132, 2016. © 2015 Wiley Periodicals, Inc.

  2. Secondary Structures in a Freeze-Dried Lignite Humic Acid Fraction Caused by Hydrogen-Bonding of Acidic Protons with Aromatic Rings.

    PubMed

    Cao, Xiaoyan; Drosos, Marios; Leenheer, Jerry A; Mao, Jingdong

    2016-02-16

    A lignite humic acid (HA) was separated from inorganic and non-HA impurities (i.e., aluminosilicates, metals) and fractionated by a combination of dialysis and XAD-8 resin. Fractionation revealed a more homogeneous structure of lignite HA. New and more specific structural information on the main lignite HA fraction is obtained by solid-state nuclear magnetic resonance (NMR) spectroscopy. Quantitative (13)C multiple cross-polarization (multiCP) NMR indicated oxidized phenyl propane structures derived from lignin. MultiCP experiments, conducted on potassium HA salts titrated to pH 10 and pH 12, revealed shifts consistent with carboxylate and phenolate formation, but structural changes associated with enolate formation from aromatic beta keto acids were not detected. Two-dimensional (1)H-(13)C heteronuclear correlation (2D HETCOR) NMR indicated aryl-aliphatic ketones, aliphatic and aromatic carboxyl groups, phenol, and methoxy phenyl ethers. Acidic protons from carboxyl groups in both the lignite HA fraction and a synthetic HA-like polycondensate were found to be hydrogen-bonded with electron-rich aromatic rings. Our results coupled with published infrared spectra provide evidence for the preferential hydrogen bonding of acidic hydrogens with electron-rich aromatic rings rather than adjacent carbonyl groups. These hydrogen-bonding interactions likely result from stereochemical arrangements in primary structures and folding.

  3. Humic Acids as Therapeutic Compounds in Lead Intoxication.

    PubMed

    Krempaská, Klára; Vaško, Ladislav; Vašková, Janka

    2016-01-01

    The toxicity of lead and its compounds is well known, causing anemia by inhibiting the synthesis of porphyrins. The neurotoxic effects, particularly in the young, alter the structure of cell membranes and DNA. Chronic exposure to lead has adverse effects on the body by disrupting the mechanisms of energy production and tissue damage, in particular in its links with thiol groups and competition for binding sites with zinc. This review is therefore a description of the mechanism of lead toxicity as well as of possible interventions for the detoxification of the body. Part of the clinical intervention is the provision of chelates that form insoluble complexes with lead and eliminate the load in tissues. Most of these chelating agents have a number of side effects. It is therefore not surprising that active compounds with distinctive antioxidant and chelating properties are being sought after. The possibility of administering lower amounts, and the corresponding decrease in side effects, would be important for clinical practice. Both prospective studies and our initial studies on humic acids have highlighted positive effects based on their antioxidant and chelating properties.

  4. Decreased solubilization of Pu(IV) polymers by humic acids under anoxic conditions

    NASA Astrophysics Data System (ADS)

    Xie, Jinchuan; Lin, Jianfeng; Liang, Wei; Li, Mei; Zhou, Xiaohua

    2016-11-01

    Pu(IV) polymer has a very low solubility (log[Pu(IV)aq]total = -10.4 at pH 7.2 and I = 0). However, some aspects of their environmental fate remain unclear. Humic acids are able to complex with Pu4+ ions and their dissolved species (<10 kD) in the groundwater (neutral to alkaline pH) may cause solubilization of the polymers. Also, humic acids have the native reducing capacity and potentially reduce the polymeric Pu(IV) to Pu(III)aq (log[Pu(III)aq]total = -5.3 at pH 7.2 and I = 0). Solubilization and reduction of the polymers can enhance their mobility in subsurface environments. Nevertheless, humic acids readily coat the surfaces of metal oxides via electrostatic interaction and ligand exchange mechanisms. The humic coatings are expected to prevent both solubilization and reduction of the polymers. Experiments were conducted under anoxic and slightly alkaline (pH 7.2) conditions in order to study whether humic acids have effects on stability of the polymers. The results show that the polymeric Pu(IV) was almost completely transformed into aqueous Pu(IV) in the presence of EDTA ligands. In contrast, the dissolved humic acids did not solubilize the polymers but in fact decreased their solubility by one order of magnitude. The humic coatings were responsible for the decreased solubilization. Such coatings limited the contact between the polymers and EDTA ligands, especially at the relatively high concentrations of humic acids (>0.57 mg/L). Solubilization of the humic-coated polymers was thus inhibited to a significant extent although EDTA, having the great complexation ability, was present in the humic solutions. Reduction of Pu(IV) polymers by the humic acids was also not observed in the absence of EDTA. In the presence of EDTA, the polymers were partially reduced to Pu(III)aq by the humic acids of 0.57 mg/L and the percentage of Pu(III)aq accounted for 51.7% of the total aqueous Pu. This demonstrates that the humic acids were able to reduce the aqueous Pu

  5. Adsorption and desorption of phthalic acid esters on graphene oxide and reduced graphene oxide as affected by humic acid.

    PubMed

    Lu, Lun; Wang, Jun; Chen, Baoliang

    2018-01-01

    The implications of humic acid (HA) regarding surface properties of graphene materials and their interactions with phthalic acid esters (PAEs) are not vivid. We report the role of HA on graphene oxide (GO) and reduced graphene oxide (RGO) for sorption-desorption behavior of PAEs. Besides higher surface area and pore volume, the hydrophobic π-conjugated carbon atoms on RGO ensured prominent adsorption capacity towards PAEs in comparison to hydrophilic GO, highlighting the hydrophobic effect. After adjusting for the hydrophobic effect by calculating the hexadecane-water partition coefficient (K HW ) normalized adsorption coefficient (K d /K HW ), the dimethyl phthalate (DMP) molecule portrayed a higher adsorption affinity towards RGO by π-π electron donor-acceptor (EDA) interaction for active sites on graphene interface via sieving effect. In contrast to RGO, the weak π-π EDA interactions and H-bonding was observed between the carbonyl groups of PAEs and oxygen containing functional groups on GO. There was no obvious change in morphologies of GO and RGO before and desorption as revealed by SEM and TEM images, as desorption hysteresis did not occur in all conditions. The presence of HA also resulted in shielding effect thereby decreasing the adsorption rate and capacity of diethyl phthalate (DEP) on GO and RGO, while it had little effect on DMP, probably due to the adsorbed HA as new active sites. The desorption of DMP and DEP on RGO in presence of HA was quick and enhanced. These results should be important for evaluating the fate and health risk of graphene materials and PAEs in the environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Copper binding to soil fulvic and humic acids: NICA-Donnan modeling and conditional affinity spectra.

    PubMed

    Xu, Jinling; Tan, Wenfeng; Xiong, Juan; Wang, Mingxia; Fang, Linchuan; Koopal, Luuk K

    2016-07-01

    Binding of Cu(II) to soil fulvic acid (JGFA), soil humic acids (JGHA, JLHA), and lignite-based humic acid (PAHA) was investigated through NICA-Donnan modeling and conditional affinity spectrum (CAS). It is to extend the knowledge of copper binding by soil humic substances (HS) both in respect of enlarging the database of metal ion binding to HS and obtaining a good insight into Cu binding to the functional groups of FA and HA by using the NICA-Donnan model to unravel the intrinsic and conditional affinity spectra. Results showed that Cu binding to HS increased with increasing pH and decreasing ionic strength. The amount of Cu bound to the HAs was larger than the amount bound to JGFA. Milne's generic parameters did not provide satisfactory predictions for the present soil HS samples, while material-specific NICA-Donnan model parameters described and predicted Cu binding to the HS well. Both the 'low' and 'high' concentration fitting procedures indicated a substantial bidentate structure of the Cu complexes with HS. By means of CAS underlying NICA isotherm, which was scarcely used, the nature of the binding at different solution conditions for a given sample and the differences in binding mode were illustrated. It was indicated that carboxylic group played an indispensable role in Cu binding to HS in that the carboxylic CAS had stronger conditional affinity than the phenolic distribution due to its large degree of proton dissociation. The fact was especially true for JGFA and JLHA which contain much larger amount of carboxylic groups, and the occupation of phenolic sites by Cu was negligible. Comparable amounts of carboxylic and phenolic groups on PAHA and JGHA, increased the occupation of phenolic type sites by Cu. The binding strength of PAHA-Cu and JGHA-Cu was stronger than that of JGFA-Cu and JLHA-Cu. The presence of phenolic groups increased the chance of forming more stable complexes, such as the salicylate-Cu or catechol-Cu type structures. Copyright © 2016

  7. Humic Acids Enhanced U(VI) Attenuation in Acidic Waste Plumes: An In-situ Remediation Approach

    NASA Astrophysics Data System (ADS)

    Wan, J.; Dong, W.; Tokunaga, T. K.

    2010-12-01

    In the process of extracting plutonium for nuclear weapons production during the Cold War, large volumes of acidic waste solutions containing low-level radionuclides were discharged for decades into unlined seepage basins in several US Department of Energy (DOE) weapon facilities such as the Savannah River Site (SRS), Oak Ridge (OR), and 300 Area of the Hanford Site. Although the basins have been capped and some sites have gone through many years of active remediation, groundwaters currently remain acidic with pH values as low as 3.0 near the basins, and uranium concentrations remain much higher than its maximum contaminant level (MCL). A sustainable U biogeochemical remediation method has not yet been developed, especially under acidic conditions (pH 3-5). Bioreduction-based U remediation requires permanent maintenance of reducing conditions through indefinite supply of electron donor, and when applied in acidic plumes a high-cost pretreatment procedure is required. Methods based on precipitation of phosphate minerals depend on maintenance of high P concentrations. Precipitating of uranyl vanadates can lower U to below its MCL, but this approach is only effective at near-neutral pH. There is an urgent need for developing a sustainable method to control U mobility in acidic conditions. In this paper, we propose a method of using humic acids (HAs) to attenuate contaminant U mobility in acidic waste plumes. Our laboratory experiment results show that HAs are able to strongly and quickly adsorb onto aquifer sediments from the DOE’s SRS and OR. With a moderate addition of HA, U adsorption increased to near 100% at pH below 5.0. Because U partitioning onto the HA modified mineral surfaces is so strong, U concentration in groundwaters can be sustainably reduced to below its MCL. We conducted flow through experiments for U desorption by acidic groundwater leaching at pH 3.5 and 4.5 from HA-treated SRS contaminated sediments. The results show that desorption of both U

  8. Phytoremediation of Cu and Zn by vetiver grass in mine soils amended with humic acids.

    PubMed

    Vargas, Carmen; Pérez-Esteban, Javier; Escolástico, Consuelo; Masaguer, Alberto; Moliner, Ana

    2016-07-01

    Phytoremediation of contaminated mine soils requires the use of fast-growing, deep-rooted, high-biomass, and metal-tolerant plants with the application of soil amendments that promote metal uptake by plants. A pot experiment was performed to evaluate the combined use of vetiver grass (Chrysopogon zizanioides) and humic acid for phytoremediation of Cu and Zn in mine soils. Vetiver plants were grown in soil samples collected from two mine sites of Spain mixed with a commercial humic acid derived from leonardite at doses of 0, 2, 10, and 20 g kg(-1). Plant metal concentrations and biomass were measured and metal bioavailability in soils was determined by a low molecular weight organic acid extraction. Results showed that humic acid addition decreased organic acid-extractable metals in soil. Although this extraction method is used to estimate bioavailability of metals, it was not a good estimator under these conditions due to competition with the strong chelators in the added humic acid. High doses of humic acid also promoted root growth and increased Cu concentrations in plants due to formation of soluble metal-organic complexes, which enhanced removal of this metal from soil and its accumulation in roots. Although humic acid was not able to improve Zn uptake, it managed to reduce translocation of Zn and Cu to aerial parts of plants. Vetiver resulted unsuitable for phytoextraction, but our study showed that the combined use of this species with humic acid at 10-20 g kg(-1) could be an effective strategy for phytostabilization of mine soils.

  9. Humic and fulvic acids: sink or source in the availability of metals to the marine bivalves Macoma balthicaand Potamocorbula amurensis?

    USGS Publications Warehouse

    Decho, Alan; Luoma, Samuel N.

    1994-01-01

    Humic acids (HA) and fulvic acids (FA) are common forms of organic matter in marine sedirnents, and are routinely ingested by deposit- and suspension-feeding animals. These compounds may be a sink for metals, implying that once metals are bound to humic substances they are no longer available to food webs. A series of experiments was conducted to quantitatively examine this premise using 2 estuarine bivalves from San Francisco Bay, USA: the suspension feeder Potarnocorbula arnurensis and the facultative deposit feeder Macoma balthica. HA and FA, isolated from marine sediments, were bound as organic coatings to either hydrous ferric oxides (HFO) or silica particles. Cd and Cr(II1) were adsorbed to the organic coatings or directly to uncoated HFO and silica particles. Pulse-chase laboratory feeding expenments using '"'Cd and "Cr(III) were then conducted to determine absorption efficiencies of Cd and Cr for individual specimens using each of the partlcle types. The results demonstrated that: (1) absorption of Cr(I1I) from all types of non-living particles was consistently low (< 11%). Ingested Cd showed greater bioavailability than Cr(IIl), perhaps due to differences in metal chemistry. (2) Bivalves absorbed Cd bound to uncoated HFO or silica particles (i.e. with no HA or FA present). (3) The presence of organic coatings on part~cles reduced Cd bioavailabhty compared with uncoated particles. (4) Both geochemical and biological conditions affected the food chain transfer of Cd. The data suggest that in marine systems inorganic and organic-coated particles are predominantly a sink for Cr in sediments. In the transfer of Cd to consumer animals, inorganic particles and humic substances can act as a link (although not a highly efficient one) under oxidized conditions.

  10. Direct solid surface fluorescence spectroscopy of standard chemicals and humic acid in ternary system

    NASA Astrophysics Data System (ADS)

    Mounier, S.; Nicolodelli, G.; Redon, R.; Milori, D. M. B. P.

    2017-04-01

    The front face fluorescence spectroscopy is often used to quantify chemicals in well-known matrices as it is a rapid and powerful technique, with no sample preparation. However it was not used to investigate extracted organic matter like humic substances. This work aims to fully investigate for the first time front face fluorescence spectroscopy response of a ternary system including boric acid, tryptophan and humic substances, and two binaries system containing quinine sulfate or humic substance in boric acid. Pure chemicals, boric acid, tryptophan, quinine sulfate and humic acid were mixed together in solid pellet at different contents from 0 to 100% in mass. The measurement of excitation emission matrix of fluorescence (3D fluorescence) and laser induced fluorescence were then done in the front face mode. Fluorescence matrices were decomposed using the CP/PARAFAC tools after scattering treatments. Results show that for 3D fluorescence there is no specific component for tryptophan and quinine sulfate, and that humic substances lead to a strong extinction effect for mixture containing quinine sulfate. Laser induced fluorescence gives a very good but non-specific related response for both quinine sulfate and tryptophan. No humic substances fluorescence response was found, but extinction effect is observed as for 3D fluorescence. This effect is stronger for quinine sulfate than for tryptophan. These responses were modeled using a simple absorbance versus emission model.

  11. Carbon isotope composition of dissolved humic and fulvic acids in the Tokachi River system.

    PubMed

    Nagao, Seiya; Kodama, Hiroki; Aramaki, Takafumi; Fujitake, Nobuhide; Uchida, Masao; Shibata, Yasuyuki

    2011-07-01

    This study reports carbon isotopic ratios (Δ(14)C and δ(13)C) of dissolved humic and fulvic acids in the Tokachi River system, northern Japan. These acids have a refractory feature and they represent the largest fraction of dissolved organic matter in aquatic environments. The acids were isolated using the XAD extraction method from river water samples collected at three sites (on the upper and lower Tokachi River, and from one of its tributaries) in June 2004 and 2005. δ(13)C values were -27.8 to -26.9 ‰ for humic and fulvic acids. On the other hand, the Δ(14)C values ranged from -247 to +26 ‰ and the average values were -170 ± 79 ‰ for humic acid and -44 ± 73 ‰ for fulvic acid. The difference was attributed to the residence time of fulvic acid in the watershed being shorter than that of humic acid. The large variation suggested that humic substances have a different pathway in each watershed environment.

  12. Limitations in the use of commercial humic acids in water and soil research

    USGS Publications Warehouse

    Malcolm, R.L.; MacCarthy, P.

    1986-01-01

    Seven samples of commercial "humic acids", purchased from five different suppliers, were studied, and their characteristics were compared with humic and fulvic acids isolated from streams, soils, peat, leonardite, and a dopplerite sample. Cross-polarization and magic-angle spinning 13C NMR spectroscopy clearly shows pronounced differences between the commercial materials and all other samples. Elemental and infrared spectroscopic data do not show such clear-cut differences but can be used as supportive evidence, with the 13C NMR data, to substantiate the above distinctions. As a result of these differences and due to the general lack of information relating to the source, method of isolation, or other pretreatment of the commercial materials, these commercial products are not considered to be appropriate for use as analogues of true soil and water humic substances, in experiments designed to evaluate the nature and reactivity of humic substances in natural waters and soils.

  13. Enhanced removal of humic acid from aqueous solution by novel stabilized nano-amorphous calcium phosphate: Behaviors and mechanisms

    NASA Astrophysics Data System (ADS)

    Jiang, Ling; Li, Yiming; Shao, Yi; Zhang, Yong; Han, Ruiming; Li, Shiyin; Wei, Wei

    2018-01-01

    Stabilized nano-amorphous calcium phosphate (nACP) was prepared using polyethylene glycol as stabilizer to obtain a nanosized amorphous adsorbent. The produced nACP was evaluated by using XRD, FTIR, SEM and X-ray photoelectron spectroscopy (XPS). The sedimentation test demonstrated that nACP exhibited better stability than crystallized hydroxyapatite. The adsorption efficiency of the nACP material for aqueous humic acid (HA) was evaluated from the point of view of medium pH, adsorption time, temperature, and ionic strength, as well as the presences of metal ions. The results of the study showed very good adsorption performance towards aqueous HA. The Sips modeling results revealed that the stabilized nACP adsorbent had a considerably high adsorption capacity (248.3 mg/g) for HA at 298 K. The adsorption data fitted well into pseudo-second order and Elovich kinetic models. XPS analyses indicated that HA retention on nACP material might be due to the surface complexation reaction between oxygen-containing group and calcium of HA and nACP, respectively. Moreover, the HA adsorption capacity of nACP could still keep more than 86% after four adsorption-desorption cycles. By taking into account all results it was concluded that the nACP adsorbent leveraged its stability in combination with its high uptake capacity to offer a great promise for HA adsorption from water.

  14. Complexation studies with lanthanides and humic acid analyzed by ultrafiltration and capillary electrophoresis-inductively coupled plasma mass spectrometry.

    PubMed

    Kautenburger, Ralf; Beck, Horst Philipp

    2007-08-03

    For the long-term storage of radioactive waste, detailed information about geo-chemical behavior of radioactive and toxic metal ions under environmental conditions is necessary. Humic acid (HA) can play an important role in the immobilisation or mobilisation of metal ions due to complexation and colloid formation. Therefore, we investigate the complexation behavior of HA and its influence on the migration or retardation of selected lanthanides (europium and gadolinium as homologues of the actinides americium and curium). Two independent speciation techniques, ultrafiltration and capillary electrophoresis coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS) have been compared for the study of Eu and Gd interaction with (purified Aldrich) HA. The degree of complexation of Eu and Gd in 25 mg l(-1) Aldrich HA solutions was determined with a broad range of metal loading (Eu and Gd total concentration between 10(-6) and 10(-4) mol l(-1)), ionic strength of 10 mM (NaClO4) and different pH-values. From the CE-ICP-MS electropherograms, additional information on the charge of the Eu species was obtained by the use of 1-bromopropane as neutral marker. To detect HA in the ICP-MS and separate between HA complexed and non complexed metal ions in the CE-ICP-MS, we have halogenated the HA with iodine as ICP-MS marker.

  15. Humic acid inhibits HBV-induced autophagosome formation and induces apoptosis in HBV-transfected Hep G2 cells

    PubMed Central

    Pant, Kishor; Yadav, Ajay K.; Gupta, Parul; Rathore, Abhishek Singh; Nayak, Baibaswata; Venugopal, Senthil K.

    2016-01-01

    Hepatitis B Virus (HBV) utilizes several mechanisms to survive in the host cells and one of the main pathways being autophagosome formation. Humic acid (HA), one of the major components of Mineral pitch, is an Ayurvedic medicinal food, commonly used by the people of the Himalayan regions of Nepal and India for various body ailments. We hypothesized that HA could induce cell death and inhibit HBV-induced autophagy in hepatic cells. Incubation of Hep G2.2.1.5 cells (HepG2 cells stably expressing HBV) with HA (100 μM) inhibited both cell proliferation and autophagosome formation significantly, while apoptosis induction was enhanced. Western blot results showed that HA incubation resulted in decreased levels of beclin-1, SIRT-1 and c-myc, while caspase-3 and β-catenin expression were up-regulated. Western blot results showed that HA significantly inhibited the expression of HBx (3-fold with 50 μM and 5-fold with 100 μM) compared to control cells. When HA was incubated with HBx-transfected Hep G2 cells, HBx-induced autophagosome formation and beclin-1 levels were decreased. These data showed that HA induced apoptosis and inhibited HBV-induced autophagosome formation and proliferation in hepatoma cells. PMID:27708347

  16. Investigations on humic acid removal from water using surfactant-modified zeolite as adsorbent in a fixed-bed reactor

    NASA Astrophysics Data System (ADS)

    Elsheikh, Awad F.; Ahmad, Umi Kalthom; Ramli, Zainab

    2017-10-01

    Natural organic matter (NOM) is ubiquitous in aquatic environments and has recently become an issue of worldwide concern in drinking water treatment. The major component of NOM is humic acids (HA). In this study, a natural zeolite (mordenite) was modified employing hexadecyltrimethylammonium bromide (HDTMA) to enhance greater efficient sites for sorption of HA. The natural zeolite and surfactant-modified zeolite (SMZ) were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FT-IR), N2 Adsorption-desorption isotherms and BET-specific surface area, thermographic analysis, derivative thermographic analysis (TGA-DTA) and Field emission scanning electron microscopy (FESEM). A fixed-bed reactor was used for the removal of HA and the effects of different experimental parameters such as HDTMA loading levels, HA solution flow rate, solution pH and eluent concentration were investigated. The results indicated that the SMZ bed with HDTMA loading of 75% of external cation exchange capacity (ECEC) at a flow rate of 2 BV/h and pH of 10 showed the greatest enhanced removal efficiency of HA while ethanol solutions (25%v/v) with feed flow rate of 2 BV/h were sufficient for complete regeneration of SMZ and desorption of HA. Measurements of surface area of SMZ indicated that a monolayer formation of the surfactant at those conditions allowed the optimum removal of HA.

  17. Compositional and functional features of humic acid-like fractions from vermicomposting of sewage sludge and cow dung.

    PubMed

    Li, Xiaowei; Xing, Meiyan; Yang, Jian; Huang, Zhidong

    2011-01-30

    The chemical changes occurring in five different substrates of sewage sludge spiked with different proportions of cow dung after vermicomposting with Eisenia foetida for 90 days were investigated. Their humic acid-like (HAL) fractions were isolated to determine the elemental and functional composition, and structural and functional characteristics using ultraviolet/visible, Fourier transform infrared (FT-IR) and fluorescence spectroscopies and scanning electron microscopy. After vermicomposting, the total organic C and C/N ratio decreased, and the total extractable C and humic acid (HA) C increased in all substrates. In the HAL fractions, the C and H contents, C/N and C/O and aliphatic structures, proteinaceous components and carbohydrates decreased, while the O and N and acidic functional group contents and C/H ratio, aromaticity and polycondensation structures increased. Further, the results suggest that the addition of cow dung to sewage sludge could improve the quality of organic matter humification of the substrates. The structures of HAL fractions in vermicomposts resembled those typical of soil HA, especially the vermicompost of cow dung alone. Scanning electron microscopy showed the microstructure of HAL fraction in final product became close-grained and lumpy. Overall results indicate that vermicomposting was an efficient technology for promoting organic matter (OM) humification in sewage sludge and cow dung alone, as well as in mixtures of both materials, improving their quality and environmental safety as a soil OM resource for utilization as soil amendments. Copyright © 2010 Elsevier B.V. All rights reserved.

  18. Protective role of humic acids against picloram-induced genomic instability and DNA methylation in Phaseolus vulgaris.

    PubMed

    Taspinar, Mahmut Sinan; Aydin, Murat; Sigmaz, Burcu; Yildirim, Nalan; Agar, Guleray

    2017-10-01

    Picloram (4-amino-3,5,6-trichloropicolinic acid) is a liquid auxinic herbicide used to control broad-leaved weeds. Picloram is representing a possible hazard to ecosystems and human health. Therefore, in this study, DNA methylation changes and DNA damage levels in Phaseolus vulgaris exposed to picloram, as well as whether humic acid (HA) has preventive effects on these changes were investigated. Random amplified polymorphic DNA (RAPD) techniques were used for identification of DNA damage and coupled restriction enzyme digestion-random amplification (CRED-RA) techniques were used to detect the changed pattern of DNA methylation. According to the obtained results, picloram (5, 10, 20, and 40 mg/l) caused DNA damage profile changes (RAPDs) increasing, DNA hypomethylation and genomic template stability (GTS) decreasing. On the other hand, different concentrations of applied HA (2, 4, 6, 8, and 10%) reduced hazardous effects of picloram. The results of the experiment have explicitly indicated that HAs could be an alternative for reducing genetic damage in plants. In addition to the alleviate effects of humic acid on genetic damage, its epigenetic effect is hypomethylation.

  19. Effect of humic acid & bacterial exudates on sorption-desorption interactions of 90Sr with brucite.

    PubMed

    Ashworth, Hollie; Abrahamsen-Mills, Liam; Bryan, Nick; Foster, Lynn; Lloyd, Jonathan R; Kellet, Simon; Heath, Sarah

    2018-05-18

    One of the nuclear fuel storage ponds at Sellafield (United Kingdom) is open to the air, and has contained a significant inventory of corroded magnox fuel and sludge for several decades. As a result, some fission products have also been released into solution. 90Sr is known to constitute a small mass of the radionuclides present in the pond, but due to its solubility and activity, it is at risk of challenging effluent discharge limits. The sludge is predominantly composed of brucite (Mg(OH)2), and organic molecules are known to be present in the pond liquor with occasional algal blooms restricting visibility. Understanding the chemical interactions of these components is important to inform ongoing sludge retrievals and effluent management. Additionally, interactions of radionuclides with organics at high pH will be an important consideration for the evolution of cementitious backfilled disposal sites in the UK. Batch sorption-desorption experiments were performed with brucite, 90Sr and natural organic matter (NOM) (humic acid (HA) and Pseudanabaena catenata cyanobacterial growth supernatant) in both binary and ternary systems at high pH. Ionic strength, pH and order of addition of components were varied. 90Sr was shown not to interact strongly with the bulk brucite surface in binary systems under pH conditions relevant to the pond. HA in both binary and ternary systems demonstrated a strong affinity for the brucite surface. Ternary systems containing HA demonstrated enhanced sorption of 90Sr at pH 11.5 and vice versa, likely via formation of strontium-humate complexes regardless of the order of addition of components. The distribution coefficients show HA sorption to be reversible at all pH values studied, and it appeared to control 90Sr behaviour at pH 11.5. Ternary systems containing cyanobacterial supernatant demonstrated a difference in 90Sr behaviour when the culture had been subjected to irradiation in the first stages of its growth.

  20. Pyrene fate affected by humic acid amendment in soil slurry systems.

    PubMed

    Liang, Yanna; Sorensen, Darwin L; McLean, Joan E; Sims, Ronald C

    2008-09-10

    Humic acid (HA) has been found to affect the solubility, mineralization, and bound residue formation of polycyclic aromatic hydrocarbons (PAHs). However, most of the studies on the interaction between HA and PAH concentrated on one or two of the three phases. Few studies have provided a simple protocol to demonstrate the overall effects of HA on PAH distribution in soil systems for all three phases. In this study, three doses of standard Elliott soil HA (ESHA), 15, 187.5, and 1,875 mug ESHA/g soil slurry, were amended to soil slurry systems. 14C-pyrene was added to the systems along with non-radiolabeled pyrene; 14C and 14CO2 were monitored for each system for a period of 120 days. The highest amendment dose significantly increased the 14C fraction in the aqueous phase within 24 h, but not after that time. Pyrene mineralization was significantly inhibited by the highest dose over the 120-day study. While organic solvent extractable 14C decreased with time in all systems, non-extractable or bound 14C was significantly enhanced with the highest dose of ESHA addition. Amendment of the highest dose of ESHA to pyrene contaminated soil was observed to have two major functions. The first was to mitigate CO2 production significantly by reducing 14CO2 from 14C pyrene mineralization. The second was to significantly increase stable bound 14C formation, which may serve as a remediation end point. Overall, this study demonstrated a practical approach for decontamination of PAH contaminated soil. This approach may be applicable to other organic contaminated environments where active bioremediation is taking place.

  1. Tetracycline adsorption on kaolinite: pH, metal cations and humic acid effects.

    PubMed

    Zhao, Yanping; Geng, Jinju; Wang, Xiaorong; Gu, Xueyuan; Gao, Shixiang

    2011-07-01

    Contamination of environmental matrixes by human and animal wastes containing antibiotics is a growing health concern. Because tetracycline is one of the most widely-used antibiotics in the world, it is important to understand the factors that influence its mobility in soils. This study investigated the effects of pH, background electrolyte cations (Li(+), Na(+), K(+), Ca(2+) and Mg(2+)), heavy metal Cu(2+) and humic acid (HA) on tetracycline adsorption onto kaolinite. Results showed that tetracycline was greatly adsorbed by kaolinite over pH 3-6, then decreased with the increase of pH, indicating that tetracycline adsorption mainly through ion exchange of cations species and complexation of zwitterions species. In the presence of five types of cations (Li(+), Na(+), K(+), Ca(2+) and Mg(2+)), tetracycline adsorption decreased in accordance with the increasing of atomic radius and valence of metal cations, which suggested that outer-sphere complexes formed between tetracycline and kaolinite, and the existence of competitor ions lead to the decreasing adsorption. The presence of Cu(2+) greatly enhanced the adsorption probably by acting as a bridge ion between tetracycline species and the edge sites of kaolinite. HA also showed a major effect on the adsorption: at pH < 6, the presence of HA increased the adsorption, while the addition of HA showed little effect on tetracycline adsorption at higher pH. The soil environmental conditions, like pH, metal cations and soil organic matter, strongly influence the adsorption behavior of tetracycline onto kaolinite and need to be considered when assessing the environmental toxicity of tetracycline.

  2. Reduction of toxic Cr(VI)-humic acid in an ionic liquid

    NASA Astrophysics Data System (ADS)

    Huang, Hsin-Liang; Huang, Hsin-Hung; Wei, Yu Jhe

    2017-07-01

    Remediation of soil contaminated by toxic hexavalent chromium species associated with humic acid (Cr(VI)-HA) and absorbed Cr(VI) in pores frequently experiences technical difficulties. In the present work, a feasibility study for extraction of the Cr(VI) species from a molecular sieve MCM-41 (Mobil Composition of Matter No. 41) that was used to simulate the pore system of soil, with a green solvent (ionic liquid), 1-butyl-3-methylimidazolium chloride ([C4mim][Cl]), was carried out. After a 30-min extraction, approximately 70% of the Cr(VI) species can be extracted. By component fitted X-ray absorption near edge structure (XANES) spectroscopy, about 48% of the Cr(VI)-HA are reduced to form less toxic species (Cr(III)-HA) during extraction with [C4mim][Cl]. Note that the Cr-O in the [C4mim][Cl] phase has a slightly greater bond distance (BD) (0.162 nm) possibly due to the fact of that the fraction of Cr(III) is increased in the extraction process. The non-extractable chromium remaining in MCM-41 has a much greater fraction of Cr(III) (78%) and its BD is further increased to 0.195 nm. The coordination numbers of chromium for the 1st shell Cr-O in the Cr(VI) and Cr(III) species are in the range of 2.4-2.9, suggesting that chromium is chelated with HA and adsorbed in MCM-41. The 1H NMR data also suggest that the enhanced reduction of the Cr(VI) species may be related to interactions between chromium species and electron-rich imidazole ring of the [C4mim]+. This work also exemplifies that the fate of toxic chromium species in the complicated remediation of contaminated soils can be revealed in a molecule-scale study by synchrotron X-ray absorption spectroscopy.

  3. Effect of humic acid on pyrene removal from water by polycation-clay mineral composites and activated carbon.

    PubMed

    Radian, Adi; Mishael, Yael

    2012-06-05

    Pyrene removal by polycation-montmorillonite (MMT) composites and granulated activated carbon (GAC) in the presence of humic acid (HA) was examined. Pyrene, HA, and sorbent interactions were characterized by FTIR, fluorescence and zeta measurements, adsorption, and column filtration experiments. Pyrene binding coefficients to the macromolecules were in the order of PVPcoS (poly-4-vinylpiridine-co-styrene) > HA > PDADMAC (poly diallyl-dimethyl-ammonium-chloride), correlating to pyrene-macromolecules compatibility. Electrostatic interactions explained the high adsorption of HA to both composites (∼100%), whereas HA adsorption by GAC was low. Pyrene removal by the composites, unlike GAC, was enhanced in the presence of HA; removal by PDADMAC-MMT increased from ∼50 (k(d) = 2.2 × 10(3) kg/L) to ∼70% (k(d) = 2.4 × 10(3) kg/L) in the presence of HA. This improvement was attributed to the adsorption of pyrene-HA complexes. PVPcoS-MMT was most efficient in removing pyrene (k(d) = 1.1 × 10(4) kg/L, >95% removal) which was explained in terms of specific π donor-π acceptor interactions. Pyrene uptake by column filters of GAC reached ∼50% and decreased to ∼30% in the presence of HA. Pyrene removal by the PVPcoS-MMT filter was significantly higher (100-85% removal), exhibiting only a small decrease in the presence of HA. The utilization of HA as an enhancing agent in pollutant removal is novel and of major importance in water treatment.

  4. Effects of humic acids with different polarities on the photocatalytic activity of nano-TiO2 at environment relevant concentration.

    PubMed

    Wu, Wei; Shan, Guoqiang; Xiang, Qian; Zhang, Yinqing; Yi, Shujun; Zhu, Lingyan

    2017-10-01

    Large volume production and application of nano-TiO 2 make it inevitably release to natural waters and its environmental behaviors would be affected by natural organic matters. In this study, the mechanisms of humic acid (HA) affecting the photocatalytic performance of nano-TiO 2 were elucidated by using three HA fractions from the same source but with different polarities. Bulk HA was fractionated on a silica gel column to get three fractions with polarity increasing in the order of FA, FB and FC. FA was fulvic acid-like while FB and FC were humic acid-like. All the three fractions (at 0.1 mg/L) promoted the generation of hydroxyl radicals (OHs) by nano-TiO 2 , and thus in turn facilitated the photocatalytic degradation of bispheol A (BPA). FA and FC displayed a stronger promotion effect than FB and the bulk HA. Online in situ flow cell ATR-FTIR and XPS analyses indicated that HA fractions could form charge-transfer complex with nano-TiO 2 surface through the phenolic hydroxyl and carboxylic groups, which favored the separation of photogenerated electron-hole pairs. Through step methylation experiments, it was verified that the phenolic hydroxyl and carboxylic groups of HA fractions played important roles in promoting the photocatalytic performance of nano-TiO 2 , and the effect of carboxylic group was more significant than the phenolic hydroxyl group. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Isolation of Soil Bacteria Adapted To Degrade Humic Acid-Sorbed Phenanthrene

    PubMed Central

    Vacca, D. J.; Bleam, W. F.; Hickey, W. J.

    2005-01-01

    The goal of these studies was to determine how sorption by humic acids affected the bioavailability of polynuclear aromatic hydrocarbons (PAHs) to PAH-degrading microbes. Micellar solutions of humic acid were used as sorbents, and phenanthrene was used as a model PAH. Enrichments from PAH-contaminated soils established with nonsorbed phenanthrene yielded a total of 25 different isolates representing a diversity of bacterial phylotypes. In contrast, only three strains of Burkholderia spp. and one strain each of Delftia sp. and Sphingomonas sp. were isolated from enrichments with humic acid-sorbed phenanthrene (HASP). Using [14C]phenanthrene as a radiotracer, we verified that only HASP isolates were capable of mineralizing HASP, a phenotype hence termed “competence.” Competence was an all-or-nothing phenotype: noncompetent strains showed no detectable phenanthrene mineralization in HASP cultures, but levels of phenanthrene mineralization effected by competent strains in HASP and NSP cultures were not significantly different. Levels and rates of phenanthrene mineralization exceeded those predicted to be supported solely by the metabolism of phenanthrene in the aqueous phase of HASP cultures. Thus, competent strains were able to directly access phenanthrene sorbed by the humic acids and did not rely on desorption for substrate uptake. To the best of our knowledge, this is the first report of (i) a selective interaction between aerobic bacteria and humic acid molecules and (ii) differential bioavailability to bacteria of PAHs sorbed to a natural biogeopolymer. PMID:16000791

  6. Adsorption of imidazolinone herbicides on smectite-humic acid and smectite-ferrihydrite associations.

    PubMed

    Leone, P; Nègre, M; Gennari, M; Boero, V; Celis, R; Cornejo, J

    2002-01-16

    Adsorption of imazapyr (IMZ), imazethapyr (IMZT), and imazaquin (IMZQ) was studied on two smectite-humic acid and two smectite-ferrihydrite binary systems prepared by treating a Wyoming smectite with a humic acid extracted from soil (4 and 8% w/w of the smectite) and with just-precipitated synthetic ferrihydrite (8 and 16% w/w of the smectite). Adsorption of the three herbicides on the smectite was not measurable at pH >4.5, presumably because of negative charges on the surface of the smectite. Adsorption on the smectite-humic acid systems was also not measurable, presumably because of negative charges on the surface, despite the high affinity of the three herbicides for humic acid, the adsorption order of which was IMZ < IMZT < IMZQ. Adsorption decreased in the order IMZ < IMZT < IMZQ on the smectite-ferrihydrite systems and IMZQ < IMZT < IMZ on ferrihydrite, although here the differences were small. These results show that even though pure smectite cannot adsorb herbicides, it modifies the adsorption capacity of ferrihydrite. The mutual interaction of active phases such as humic acid, ferrihydrite, and smectite alters the characteristics of the resulting surface and hence the adsorption process. Investigations of herbicide adsorption have been seen to produce more reliable results if conducted on polyphasic systems rather than on single soil components.

  7. Eu(III) uptake on rectorite in the presence of humic acid: a macroscopic and spectroscopic study.

    PubMed

    Chen, Changlun; Yang, Xin; Wei, Juan; Tan, Xiaoli; Wang, Xiangke

    2013-03-01

    This work contributed to the comprehension of humic acid (HA) effect on Eu(III) uptake to Na-rectorite by batch sorption experiments, model fitting, scanning electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. At low pH, the presence of HA enhanced Eu(III) sorption on Na-rectorite, while reduced Eu(III) sorption at high pH. The experimental data of Eu(III) sorption in the absence and presence of HA were simulated by the diffuse-layer model well with the aid of FITEQL 3.2 software. The basal spacing of rectorite became large after Eu(III) and HA sorption on Na-rectorite. Some of Eu(III) ions and HA might be intercalated into the interlayer space of Na-rectorite. EXAFS analysis showed that the R(Eu-O) (the bond distance of Eu and O in the first shell of Eu) and N values (coordination number) of Eu(III)-HA-rectorite system were smaller than those of Eu(III)-rectorite system. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Distribution and speciation of mercury affected by humic acid in mariculture sites at the Pearl River estuary.

    PubMed

    Ding, Lingyun; Zhao, Kaiyun; Zhang, Lijuan; Liang, Peng; Wu, Shengchun; Wong, Ming Hung; Tao, Huchun

    2018-05-14

    At the Pearl River Estuary of southern China, mercury and its environmental problems have long been a great concern. This study investigated the distribution and speciation of mercury compounds that are significantly influenced by the increasing content of humic acid (HA, a model natural organic matter) in this region. The inorganic mercury and methyl mercury, being adsorbed and converted at different HA levels, were studied in sediments and surface water at both mariculture and their reference sites. In mariculture sediments with higher HA content (up to 4.5%), more mercury were adsorbed at different compound levels, promoting the methylation and accumulation of mercury (P < 0.05) at the sediment-water interface. Seasonal shift in environmental temperature might control the HA content, subsequently favouring mercury methylation (maximum 1.75 ± 0.08 mg L -1 d -1 ) under warm weather conditions. In reference sites received less HA wastes, lower adsorption capacity and methylation rate were observed for mercury in sediments and surface water. Our work points to the significant roles of HA on mercury distribution and speciation both spatially and seasonally, thus addressing the impacts of mariculture activities on estuary eco-system. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Sorption and toxicity reduction of pharmaceutically active compounds and endocrine disrupting chemicals in the presence of colloidal humic acid.

    PubMed

    Kim, Injeong; Kim, Hyo-Dong; Jeong, Tae-Yong; Kim, Sang Don

    This study investigated the toxicity changes and sorption of pharmaceuticals and endocrine disrupters in the presence of humic acid (HA). For the sorption experiment, a dead end filtration (DEF) system was used to separate bound and free-form target compounds. An algae growth inhibition test and E-screen assay were conducted to estimate the toxic effect of pharmaceutically active compounds (PhACs) and endocrine disrupting chemicals (EDCs), respectively. The permeate concentration was confirmed using liquid chromatography-mass spectrometry. In the sorption test, we observed significant sorption of PhACs and EDCs on colloidal HA, except for sulfamethoxazole (SMX). The values of log KCOC derived from DEF determinations ranged from 4.40 to 5.03. The removal efficiency varied with the HA concentration and the target chemical properties. Tetracycline and 4-octylphenol showed the highest sorption or removal efficiency (≈50%), even at 5 mg C/L HA. The algal growth inhibition of PhACs and the estrogenic effects of EDCs were significantly decreased in proportion to HA concentrations, except for SMX. In addition, the chemical analysis results showed a positive relationship with the bioassay results. Consequently, the sorption of PhACs and EDCs onto colloidal HA should be emphasized in natural environments because it significantly reduces bioavailable concentrations and toxicity to aquatic organisms.

  10. Contribution of coated humic acids calculated through their surface coverage on nano iron oxides for ofloxacin and norfloxacin sorption.

    PubMed

    Peng, Hongbo; Liang, Ni; Li, Hao; Chen, Fangyuan; Zhang, Di; Pan, Bo; Xing, Baoshan

    2015-09-01

    Sorption of organic contaminants on organo-mineral complexes has been investigated extensively, but the sorption contribution of mineral particles was not properly addressed before calculating KOC, especially for ionic organic contaminants. We measured the surface coverage of a humic acid (HA) on nano iron oxides (n-Fe2O3) in a series of synthesized organo-mineral complexes. The contribution of the coated HA to ofloxacin (OFL) and norfloxacin (NOR) sorption in HA-n-Fe2O3 complexes was over 80% of the total sorption with the surface coverage of 36% and fOC of 1.6%. All the coated HA showed higher sorption to NOR and OFL in comparison to the original HA, suggesting HA fractionation and/or physical re-conformation during organo-mineral complex formation. The decreased KOC with multilayer coating may suggest the importance of site-specific interactions for OFL sorption, while the increased KOC with multilayer coating may suggest the importance of partitioning in hydrophobic region for NOR sorption. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Response surface methodology investigation into the interactions between arsenic and humic acid in water during the coagulation process.

    PubMed

    Watson, Malcolm Alexander; Tubić, Aleksandra; Agbaba, Jasmina; Nikić, Jasmina; Maletić, Snežana; Molnar Jazić, Jelena; Dalmacija, Božo

    2016-07-15

    Interactions between arsenic and natural organic matter (NOM) are key limiting factors during the optimisation of drinking water treatment when significant amounts of both must be removed. This work uses Response Surface Methodology (RSM) to investigate how they interact during their simultaneous removal by iron chloride coagulation, using humic acid (HA) as a model NOM substance. Using a three factor Box-Behnken experimental design, As and HA removals were modelled, as well as a combined removal response. ANOVA results showed the significance of the coagulant dose for all three responses. At high initial arsenic concentrations (200μg/l), As removal was significantly hindered by the presence of HA. In contrast, the HA removal response was found to be largely independent of the initial As concentration, with the optimum coagulant dose increasing at increasing HA concentrations. The combined response was similar to the HA removal response, and the interactions evident are most interesting in terms of optimising treatment processes during the preparation of drinking water, highlighting the importance of utilizing RSM for such investigations. The combined response model was successfully validated with two different groundwaters used for drinking water supply in the Republic of Serbia, showing excellent agreement under similar experimental conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Three-dimensional fluorescence analysis of chernozem humic acids and their electrophoretic fractions

    NASA Astrophysics Data System (ADS)

    Trubetskoi, O. A.; Trubetskaya, O. E.

    2017-09-01

    Polyacrylamide gel electrophoresis in combination with size-exclusion chromatography (SEC-PAGE) has been used to obtain stable electrophoretic fractions of different molecular size (MS) from chernozem humic acids (HAs). Three-dimensional fluorescence charts of chernozem HAs and their fractions have been obtained for the first time, and all fluorescence excitation-emission maxima have been identified in the excitation wavelength range of 250-500 nm. It has been found that fractionation by the SEC-PAGE method results in a nonuniform distribution of protein- and humin-like fluorescence of the original HA preparation among the electrophoretic fractions. The electrophoretic fractions of the highest and medium MSs have only the main protein-like fluorescence maximum and traces of humin-like fluorescence. In the electrophoretic fraction of the lowest MS, the intensity of protein-like fluorescence is low, but the major part of humin-like fluorescence is localized there. Relationships between the intensity of protein-like fluorescence and the weight distribution of amino acids have been revealed, as well as between the degree of aromaticity and the intensity of humin-like fluorescence in electrophoretic fractions of different MSs. The obtained relationships can be useful in the interpretation of the spatial structural organization and ecological functions of soil HAs.

  13. [Adsorption of aflatoxin on montmorillonite modified by low-molecular-weight humic acids].

    PubMed

    Yao, Jia-Jia; Kang, Fu-Xing; Gao, Yan-Zheng

    2012-03-01

    The adsorption of a typical biogenic toxin aflatoxin B1 on montmorillonite modified by low-molecular-weight humic acids (M(r) < 3 500) was investigated. The montmorillonite rapidly adsorbed the aflatoxin B1 until amounting to the maximal capacity, and then the adsorbed aflatoxin B1 slowly released into solution and reached the sorption equilibrium state after 12 h. The sorption isotherm of aflatoxin B1 by montmorillonite could be well described by Langmiur model, while the sorption isotherm by humic acid-modified montmorillonite was well fitted by using the Freundlich model. The modification of the montmorillonite with humic acids obviously enhanced its adsorption capacity for aflatoxin B1, and the amounts of aflatoxin adsorbed by modified montmorillonite were obviously higher than those by montmorillonite. The sorption enhancement by humic acid modification was attributed to (1) the enlarged adsorption sites which owed to the surface collapse of crystal layers induced by organic acids, and (2) the binding of aflatoxin with the humic acid sorbed on mineral surface. In addition, the adsorption amounts of aflatoxin by montmorillonite and modified montmorillonite increased with the increase of pH values in solution, and more significant enhancement was observed for the latter than the former, which attributed to the release of humic acids from the modified montmorillonite with the high pH values in solution. This indicates that increasing the pH values resulted in the enhanced hydrophilic property and the release of the organic acids presented in modified montmorillonite, and more sorption sites were available for aflatoxin on the modified montmorillonite. Results of this work would strengthen our understanding of the behavior and fate of biological contaminants in the environment.

  14. Evaluating the sorption of organophosphate esters to different sourced humic acids and its effects on the toxicity to Daphnia magna.

    PubMed

    Pang, Long; Liu, Jingfu; Yin, Yongguang; Shen, Mohai

    2013-12-01

    Because of large usage as flame retardants and additives, organophosphate esters (OPEs) are widely detected in the environment and regarded as emerging contaminants. However, the sorption of OPEs to organic matter and its effects have scarcely been studied. In the present study, the sorption of 9 commonly used OPEs to 4 representative humic acids--Elliott Soil humic acid, Suwannee River humic acid, Aldrich humic acid, and Acros humic acid--in the range of 0 mg/L to 50 mg/L dissolved organic carbon (DOC), was evaluated with negligible-depletion solid-phase microextraction and verified by its impacts on the toxicity to the aquatic invertebrate Daphnia magna. Whereas OPEs with a high octanol/water partition coefficient (log K(OW)=4.51-6.64) were associated with humic acids mainly by hydrophobic interaction with DOC partition coefficient (K(DOC)) in the range of 10²·²² to 10⁵·³¹, the sorption of low-K(OW) OPEs (log K(OW)=-0.65 to 2.59) to humic acids was not hydrophobic interaction-dominant, with K(DOC) in the range of 10³·⁴⁷ to 10⁴·²⁹. These results were corroborated by the effects of humic acids on the acute toxicity of 3 high-K(OW) OPEs to D. magna. The sorption of OPEs to Suwannee River humic acid was weak and had negligible effects on the toxicity of high-K(OW) OPEs; the presence of terrestrial Acros humic acid (50 mg/L DOC), however, significantly decreased the toxicity by 53% to 60%. The results indicated that the strong sorption between high-K(OW) OPEs and terrestrial humic acid might affect their transportation and bioavailability. © 2013 SETAC.

  15. Transformation of Flame Retardant Tetrabromobisphenol A by Aqueous Chlorine and the Effect of Humic Acid.

    PubMed

    Gao, Yuan; Pang, Su-Yan; Jiang, Jin; Ma, Jun; Zhou, Yang; Li, Juan; Wang, Li-Hong; Lu, Xue-Ting; Yuan, Li-Peng

    2016-09-06

    In this work, it was found that the most widely used brominated flame retardant tetrabromobisphenol A (TBrBPA) could be transformed by free chlorine over a wide pH range from 5 to 10 with apparent second-order rate constants from 138 to 3210 M(-1)·s(-1). A total of eight products, including one quinone-like compound (i.e., 2,6-dibromoquinone), two dimers, and several simple halogenated phenols (e.g., 4-(2-hydroxyisopropyl)-2,6-dibromophenol, 2,6-dibromohydroquinone, and 2,4,6-tribromophenol), were detected by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) using a novel precursor ion scan (PIS) approach. A tentative reaction pathway was proposed: chlorine initially oxidized TBrBPA leading to the formation of a phenoxy radical, and then this primary radical and its secondary intermediates (e.g., 2,6-dibromo-4-isopropylphenol carbocation) formed via beta-scission subsequently underwent substitution, dimerization, and oxidation reactions. Humic acid (HA) considerably inhibited the degradation rates of TBrBPA by chlorine even accounting for oxidant consumption. A similar inhibitory effect of HA was also observed in permanganate and ferrate oxidation. This inhibitory effect was possibly attributed to the fact that HA competitively reacted with the phenoxy radical of TBrBPA and reversed it back to parent TBrBPA. This study confirms that chlorine can transform phenolic compounds (e.g., TBrBPA) via electron transfer rather than the well-documented electrophilic substitution, which also have implications on the formation pathway of halo-benzoquinones during chlorine disinfection. These findings can improve the understanding of chlorine chemistry in water and wastewater treatment.

  16. Evaluation of adsorption capacities of humic acids extracted from Algerian soil on polyaniline for application to remove pollutants such as Cd(II), Zn(II) and Ni(II) and characterization with cavity microelectrode.

    PubMed

    Terbouche, Achour; Ramdane-Terbouche, Chafia Ait; Hauchard, Didier; Djebbar, Safia

    2011-01-01

    The adsorption capacities of new humic acids isolated from Yakouren forest (YHA) and Sahara (Tamenrasset: THA) soils (Algeria) and commercial humic acid (PFHA) on polyaniline emeraldine base (PEB) were studied at pH 6.6. Also the adsorption of heavy metals such as Cd2+, Zn2+ and Ni2+ on humic acid-polyaniline systems (HA-PEB) was investigated at the same conditions. HA-PEB compounds were characterized by scanning electron microscopy (SEM), infrared spectrometry and cavity microelectrode. In addition, batch adsorption and cavity microelectrode were used in the adsorption study of Cd2+, Zn2+ and Ni2+ on HA-PEB. To develop biocaptors of polluting metals using a cavity microelectrode modified by HA-PEB systems, the adsorption kinetic and adsorption capacity were investigated. The SEM analysis showed that the presence of humic acid affected the PEB surface and caused the formation of a granular morphology. The maximum adsorption capacities (q(max)) of PFHA, THA and YHA determined by adsorption isotherms were 91.31, 132.1 and 151.0 mg/g, respectively. Batch adsorption results showed that q(max) of Cd2+, Zn2+ and Ni2+ on HA-PEB followed the order: THA-PEB > YHA-PEB > PFHA-PEB. The voltammograms obtained with HA-PEB modified cavity microelectrode showed the appearance of new redox couples reflecting the adsorption of HA on PEB. Metal-humic acid-polyaniline voltammograms were characterized by appearance of oxidation-reduction couples or reduction wave corresponding to metal. Finally, the result may be exploited to develop a biocaptor based on the cavity microelectrode amended by THA-PEB and YHA-PEB.

  17. The impact of humic acid on chromium phytoextraction by aquatic macrophyte Lemna minor.

    PubMed

    Kalčíková, Gabriela; Zupančič, Marija; Jemec, Anita; Gotvajn, Andreja Žgajnar

    2016-03-01

    Studies assessing chromium phytoextration from natural waters rarely consider potential implications of chromium speciation in the presence of ubiquitous humic substances. Therefore, the present study investigated the influence of environmentally relevant concentration of humic acid (TOC = 10 mg L(-1)) on chromium speciation (Cr = 0.15 mg L(-1)) and consequently on phytoextraction by aquatic macrophyte duckweed Lemna minor. In absence of humic acid, only hexavalent chromium was present in water samples and easily taken up by L. minor. Chromium uptake resulted in a significant reduction of growth rate by 22% and decrease of chlorophyll a and chlorophyll b contents by 48% and 43%, respectively. On the other hand, presence of humic acid significantly reduced chromium bioavailability (57% Cr uptake decrease) and consequently it did not cause any measurable effect to duckweed. Such effect was related to abiotic reduction of hexavalent chromium species to trivalent. Hence, findings of our study suggest that presence of humic acid and chromium speciation cannot be neglected during phytoextraction studies. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Synergistic Removal of Pb(II), Cd(II) and Humic Acid by Fe3O4@Mesoporous Silica-Graphene Oxide Composites

    PubMed Central

    Wang, Yilong; Liang, Song; Chen, Bingdi; Guo, Fangfang; Yu, Shuili; Tang, Yulin

    2013-01-01

    The synergistic adsorption of heavy metal ions and humic acid can be very challenging. This is largely because of their competitive adsorption onto most adsorbent materials. Hierarchically structured composites containing polyethylenimine-modified magnetic mesoporous silica and graphene oxide (MMSP-GO) were here prepared to address this. Magnetic mesoporous silica microspheres were synthesized and functionalized with PEI molecules, providing many amine groups for chemical conjugation with the carboxyl groups on GO sheets and enhanced the affinity between the pollutants and the mesoporous silica. The features of the composites were characterized using TEM, SEM, TGA, DLS, and VSM measurements. Series adsorption results proved that this system was suitable for simultaneous and efficient removal of heavy metal ions and humic acid using MMSP-GO composites as adsorbents. The maximum adsorption capacities of MMSP-GO for Pb(II) and Cd (II) were 333 and 167 mg g−1 caculated by Langmuir model, respectively. HA enhances adsorption of heavy metals by MMSP-GO composites due to their interactions in aqueous solutions. The underlying mechanism of synergistic adsorption of heavy metal ions and humic acid were discussed. MMSP-GO composites have shown promise for use as adsorbents in the simultaneous removal of heavy metals and humic acid in wastewater treatment processes. PMID:23776514

  19. Removal of toxic metals from leachates from hazardous solid wastes and reduction of toxicity to microtox by the use of calcium alginate beads containing humic acid.

    PubMed

    Pandey, Ashok K; Pandey, Shri Dhar; Misra, Virendra

    2002-06-01

    Improper disposal of hazardous wastes can lead to release of potentially harmful substances through leaching such as heavy metals, which ultimately contaminate soil, sediment surface water, and groundwater through runoff. To remove these toxic metals and avoid any adverse effect on the ecosystem, a novel approach involving calcium alginate (CA) beads containing humic acid (HA) was used. For this, 10% leachates of the waste obtained from two major industrial units with electroplating processess were prepared at neutral pH and analyzed by atomic absorption spectrophotometry (AAS). Both leachates contained Cd, Cu, Cr, Ni, Mn, Fe, and Zn. The concentrations of Ni, Mn, Fe, and Zn in the waste were found to be significant. The leachates analyzed were passed through columns packed with calcium alginate beads with or without humic acid. The concentrations of various metals in beads and in different fractions collected after adsorption were measured. Data recorded indicate that calcium alginate beads containing humic acids are more efficient in removal of all metals in substantial amounts from the two leachates. Along with removal of metals, this process led to considerable detoxification of the leachates as tested by Microtox assay, indicated by earlier protection and higher EC(50). The significance of the results in relation to removal of toxic metals by beads containing humic acid is discussed. (c) 2002 Elsevier Science (USA).

  20. Biochemical changes in grape rootstocks resulted from humic acid treatments in relation to nematode infection.

    PubMed

    Kesba, Hosny H; El-Beltagi, Hossam S

    2012-04-01

    To investigate the effect of humic acid on nematode infected, resistant and susceptible grapes in relation to lipid peroxidation and antioxidant mechanisms on selected biochemical parameters known as proactive substances. The grape rootstocks, superior, superior/freedom and freedom were reacted differently to Meloidogyne incognita and Rotylenchulus reniformis according to rootstock progenitor. Two weeks after inoculation, two commercial products of humic acid were applied at the rate of (2, 4 mL or grams/plant) as soil drench. After 4 months, nematode soil populations were extracted and counted. A subsample of roots from each plant was stained and gall numbers, embedded stages per root were calculated, final population, nematode build up (Pf/Pi), average of eggs/eggmass were estimated. Subsamples of fresh root of each treatment were chemically analyzed. Freedom reduced significantly the nematode criteria and build up. Humic acid granules appeared to be more suppressive to nematode build up on superior and the higher dose on superior/freedom than liquid treatments. On freedom, all treatments reduced significantly the nematode build up regardless to the material nature. The higher dose was more effective than the lower one. As a result of humic acid applications, the malondialdehyde (MDA) and H2O2 contents were significantly reduced after humic acid treatments while the antioxidant compounds glutathione (GSH), ascorbic acid (ASA) and total phenol contents were significantly increased when compared with check. Antioxidant defense enzymes ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase (PPO)showed significant increase in their specific activities in treated plants compared with nematode treated check. Humic acid treatments improve the yield of grape by increasing the contents of antioxidant compounds and the specific activities of antioxidant enzymes.

  1. Humic acid batteries derived from vermicomposts at different C/N ratios

    NASA Astrophysics Data System (ADS)

    Shamsuddin, R. M.; Borhan, A.; Lim, W. K.

    2017-06-01

    Humic acid is a known fertilizer derived from decomposed organic matters. Organic wastes are normally landfilled for disposal which had contributed negatively to the environment. From waste-to-wealth perspective, such wastes are potential precursors for compost fertilizers. When worms are added into a composting process, the process is termed as vermicomposting. In this work, humic acid from vermicompost derived from campus green wastes was developed into a battery. This adds value proposition to compost instead of being traditionally used solely as soil improver. This research work aimed to study the correlation between electrical potential generated by humic acid at different Carbon to Nitrogen (C/N) ratios of vermicompost at 20, 25, 30 and 35. The temperature and pH profiles of composting revealed that the compost was ready after 55 days. The humic acid was extracted from compost via alkaline extraction followed by precipitation in a strong acid. The extracted humic acid together with other additives were packed into a compartment and termed as vermibattery. Another set of battery running only on the additives was also prepared as a control. The net voltage produced by a single vermibattery cell with Zn and PbO electrodes was in the range of 0.31 to 0.44 V with compost at C/N ratio of 30 gave the highest voltage. The battery can be connected in series to increase the voltage generation. Quality assessment on the compost revealed that the final carbon content is between 16 to 23 wt%, nitrogen content of 0.4 to 0.5 wt%, humic acid yield of 0.7 to 1.5 wt% and final compost mass reduction of 10 to 35 wt%. Composting campus green wastes carries multi-fold benefits of reducing labour requirement, generating fertilizer for campus greenery and green battery construction.

  2. Biochemical changes in grape rootstocks resulted from humic acid treatments in relation to nematode infection

    PubMed Central

    Kesba, Hosny H; El-Beltagi, Hossam S

    2012-01-01

    Objective To investigate the effect of humic acid on nematode infected, resistant and susceptible grapes in relation to lipid peroxidation and antioxidant mechanisms on selected biochemical parameters known as proactive substances. Methods The grape rootstocks, superior, superior/freedom and freedom were reacted differently to Meloidogyne incognita and Rotylenchulus reniformis according to rootstock progenitor. Two weeks after inoculation, two commercial products of humic acid were applied at the rate of (2, 4 mL or grams/plant) as soil drench. After 4 months, nematode soil populations were extracted and counted. A subsample of roots from each plant was stained and gall numbers, embedded stages per root were calculated, final population, nematode build up (Pf/Pi), average of eggs/eggmass were estimated. Subsamples of fresh root of each treatment were chemically analyzed. Results Freedom reduced significantly the nematode criteria and build up. Humic acid granules appeared to be more suppressive to nematode build up on superior and the higher dose on superior/freedom than liquid treatments. On freedom, all treatments reduced significantly the nematode build up regardless to the material nature. The higher dose was more effective than the lower one. As a result of humic acid applications, the malondialdehyde (MDA) and H2O2 contents were significantly reduced after humic acid treatments while the antioxidant compounds glutathione (GSH), ascorbic acid (ASA) and total phenol contents were significantly increased when compared with check. Antioxidant defense enzymes ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase (PPO)showed significant increase in their specific activities in treated plants compared with nematode treated check. Conclusions Humic acid treatments improve the yield of grape by increasing the contents of antioxidant compounds and the specific activities of antioxidant enzymes. PMID:23569915

  3. The application of bioflocculant for the removal of humic acids from stabilized landfill leachates.

    PubMed

    Zouboulis, Anastasios I; Chai, Xiao-Li; Katsoyiannis, Ioannis A

    2004-01-01

    The evaluation of bioflocculant, in comparison with traditional inorganic coagulants, for the removal of humic acids from landfill leachates stabilized by biological treatment, was performed using conventional jar-test coagulation experiments. The optimized conditions (pH and coagulant dosage) were identified for the treatment of synthetic solutions as well as for biologically pre-treated landfill leachates. It was found that the application of bioflocculant was quite efficient in the removal of humic acids from synthetic solutions as well as in the reduction of COD content from real landfill leachates. The optimal pH value was found to be between 7 and 7.5, while a 20 mg/l bioflocculant dosage was sufficient in providing more than 85% humic acid removal. The results were comparable with those obtained by the application of conventional coagulants such as alum or polyaluminum chloride; therefore, bioflocculant can be considered as a viable alternative in the treatment of landfill leachates applying coagulation.

  4. The effect of humic acids on biodegradation of polycyclic aromatic hydrocarbons depends on the exposure regime.

    PubMed

    Tejeda-Agredano, Maria-Carmen; Mayer, Philipp; Ortega-Calvo, Jose-Julio

    2014-01-01

    Binding of polycyclic aromatic hydrocarbons (PAHs) to dissolved organic matter (DOM) can reduce the freely dissolved concentration, increase apparent solubility or enhance diffusive mass transfer. To study the effects of DOM on biodegradation, we used phenanthrene and pyrene as model PAHs, soil humic acids as model DOM and a soil Mycobacterium strain as a representative degrader organism. Humic acids enhanced the biodegradation of pyrene when present as solid crystals but not when initially dissolved or provided by partitioning from a polymer. Synchronous fluorescence spectrophotometry, scintillation counting and a microscale diffusion technique were applied in order to determine the kinetics of dissolution and diffusive mass transfer of pyrene. We suggest that humic acids can enhance or inhibit biodegradation as a result of the balance of two opposite effects, namely, solubilization of the chemicals on the one hand and inhibition of cell adhesion to the pollutant source on the other. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. [Analysis on the impact of composting with different proportions of corn stalks and pig manure on humic acid fractions and IR spectral feature].

    PubMed

    Sun, Xiang-Ping; Li, Guo-Xue; Xiao, Ai-Ping; Shi, Hong; Wang, Yi-Ming; Li, Yang-Yang

    2014-09-01

    Using pig manure and corn straw as raw materials for high-temperature composting, setting three different treat- ments: C/N 15, C/N 25, and C/N 35. Composting period is 120 days, which contains 30 days for ventilation cycle by forced continuous ventilation. Sampled on 0, 22, 30, 60, 90, 120th days, they were analyzed by elemental analysis and IR spectroscopy to study effect of different lignin content on compost humic acid (HA) composition and molecular structure. The results showed that the change in composting humic acid C focused on the first 30 days, while after composting, the O/C of compost HA increased, H/C decreased, and N content increased. Low C/N (15) and higher C/N ratio (35) had higher degree of oxidation than the C/N 25 in compost HA. FTIR indicated that the infrared spectrum shapes with different lignin content treatment are similar during the composting process, but the peak intensity is obviously different. Research results proved that the composting stage is more conducive to enhanced aromatic in compost HA. After composting, C/N 15 had less polysaccharide and fat ingredients and more aromatic structural components in compost HA, compared with C/N 25 and 35. In addition, compost HA of C/N 15 had higher degree of humification and its structure was more stable.

  6. Coagulation behavior of humic acid in aqueous solutions containing Cs+, Sr2+ and Eu3+: DLS, EEM and MD simulations.

    PubMed

    Tan, Liqiang; Tan, Xiaoli; Mei, Huiyang; Ai, Yuejie; Sun, Lu; Zhao, Guixia; Hayat, Tasawar; Alsaedi, Ahmed; Chen, Changlun; Wang, Xiangke

    2018-05-01

    The coagulation behaviors of humic acid (HA) with Cs + (10-500 mM), Sr 2+ (0.8-10.0 mM) and Eu 3+ (0.01-1.0 mM) at different pH values (2.8, 7.1 and 10.0) were acquired through a dynamic light scattering (DLS) technique combined with spectroscopic analysis and molecular dynamic (MD) simulations. The coagulation rate and the average hydrodynamic diameter () increased significantly as the concentration of nuclides increased. could be scaled to time t as ∝ t a at higher Sr 2+ concentrations, which shows that HA coagulation is consistent with the diffusion-limited colloid aggregation (DLCA) model. Trivalent Eu 3+ induced HA coagulation at a much lower concentration than bivalent Sr 2+ and monovalent Cs + . The coagulation value ratio of Sr 2+ and Eu 3+ to Cs + is almost proportional to Z -6 , indicating that the HA coagulation process is generally consistent with the Schulze-Hardy rule. Spectroscopic analysis indicated that the complexation between nuclides and carboxylic/phenolic groups of HA molecules played important roles in the coagulation of HA. MD modelling suggested that Sr 2+ and Eu 3+ ions increased the coagulation process through the formation of intra- or inter-molecular bridges between negatively charged HA molecules, whereas for Cs + , no inter-molecular bridges were formed. This work offers new insight into the interactions between HA and radionuclides and provides a prediction for the roles of HA in the transportation and elimination of radionuclides in severely polluted environments. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Humic acids decrease uptake and distribution of trace metals, but not the growth of radish exposed to cadmium toxicity.

    PubMed

    Ondrasek, Gabrijel; Rengel, Zed; Romic, Davor

    2018-04-30

    Naturally-occurring highly-complexed and polymerised organics such as humic acids (HA), due to their large negative charge, play a crucial role in biogeochemistry of trace metals (TM). Toxic (Cd) as well as essential (Zn, Cu, Mn) TM bind strongly to HA, but how these organo-metalic forms influence metal uptake by plants is poorly understood. A solution culture study was conducted to characterize the effects of different concentrations of HA (0-225mg/L) on the growth and element uptake/distribution in roots, shoots and hypocotyls of radish (Raphanus sativus L.) exposed to Cd (0.5mg/L) contamination. After 10-d-exposure to applied treatments, Cd induced phytotoxicity; in contrast, different concentrations of HA had no influence on biomass, but decreased concentration of most TM in examined tissues (Cu by 4.2-fold, Zn by 2.2-fold, Cd by 1.6-fold and Mn by 34%) and their total plant accumulation (Cu by 73%, Cd by 39%, Zn by 29% and Mn by 22%). HA influenced the transport/distribution of TM, decreasing accumulation in roots and increasing their translocation/deposition in shoots, with no effect on TM content in edible hypocotyls. Chemical speciation modelling of the rooting medium confirmed predominance of free metallic forms in the control (no HA) and the pronounced organo-metal complexation in the HA treatments. The results provide evidence of strong capacity of HA to decrease phytoavailability and uptake of Cd, Zn, Cu and Mn while being non-toxic even at relatively high concentration (225mg/L). Thus, HA, as naturally present soil components, control mobility and phyto-extraction of most TM as well as their phyto-accumulation. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. Cotransport of bacteria with hematite in porous media: Effects of ion valence and humic acid.

    PubMed

    Yang, Haiyan; Ge, Zhi; Wu, Dan; Tong, Meiping; Ni, Jinren

    2016-01-01

    This study investigated the influence of multiple colloids (hematite and humic acid) on the transport and deposition of bacteria (Escherichia coli) in packed porous media in both NaCl (5 mM) and CaCl2 (1 mM) solutions at pH 6. Due to the alteration of cell physicochemical properties, the presence of hematite and humic acid in cell suspensions significantly affected bacterial transport and deposition in quartz sand. Specifically, the presence of hematite (5 mg/L) decreased cell transport (increased cell deposition) in quartz sand in both NaCl and CaCl2 solutions, which could be attributed to the less negative overall zeta potentials of bacteria induced by the adsorption of positively charged hematite onto cell surfaces. The presence of a low concentration (0.1 mg/L) of humic acid in bacteria and hematite mixed suspensions reduced the adsorption of hematite onto cell surfaces, leading to increased cell transport in quartz sand in NaCl solutions, whereas, in CaCl2 solutions, the presence of 0.1 mg/L humic acid increased the formation of hematite-cell aggregates and thus decreased cell transport in quartz sand. When the concentration of humic acid was increased to 1 mg/L, enhanced cell transport was observed in both NaCl and CaCl2 solutions. The decreased adsorption of hematite onto cell surfaces as well as the competition of deposition sites on quartz sand with bacteria by the suspended humic acid contributed to the increased cell transport. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Structural and functional comparison of mobile and recalcitrant humic fractions from agricultural soils

    USDA-ARS?s Scientific Manuscript database

    Mobile humic acid (MHA) and calcium humate (CaHA) are humic fractions sequentially extracted from soil samples. MHA is extracted by dilute NaOH, and CaHA is subsequently extracted by dilute NaOH from the dilute HCl-washed soil residues of the first extraction. This chapter reviews the recent advance...

  10. Effect of Fusarium oxysporum f. sp. lycopersici on the degradation of humic acid associated with Cu, Pb, and Ni: an in vitro study.

    PubMed

    Corrales Escobosa, Alma Rosa; Landero Figueroa, Julio Alberto; Gutiérrez Corona, J Félix; Wrobel, Katarzyna; Wrobel, Kazimierz

    2009-08-01

    The intent of this work was to gain further insight on the fungus-assisted degradation/solubilization of humic acid and the related changes in metal-binding profiles. In the experimental design, Aldrich reagent humic acid (HA) or HA enriched with Cu, Pb, and Ni (HA(Me)) was added to Fusarium oxysporum f. sp. lycopersici cultures in vitro. The cultures were supplied by different carbon- and nitrogen-containing nutrients (glucose, Glc, or glutamate, Glu and ammonium, NH4+, or nitrate, NO3-, ions, respectively) in order to examine their possible effect on HA and HA(Me) decomposition. During the first 48 h of fungus growth, gradual acidification to pH 2 was observed in medium containing Glc + NH4+, while for other cultures, alkalinization to pH 9 occurred and then, the above conditions were stable up to at least 200 h. Size exclusion chromatography (SEC) with UV/Vis detection showed progressive degradation and solubilization of both HA and HA(Me) with the increasing time of fungus growth. However, the molecular mass distributions of HA-related soluble species were different in the presence of metals (HA(Me)) as referred to HA and were also influenced by the composition of growth medium. The solubilization of Pb, Cu, and Ni and their association with HA molecular mass fractions were studied using inductively coupled plasma mass spectrometry (ICP-MS) detection. Under acidic conditions, relatively high concentrations of low-molecular-mass metallic species were found in culture supernatants, while in alkaline media, metal solubilization was generally poorer. In contrast to low pH culture, SEC-ICP-MS results obtained in alkaline supernatants indicated metal binding to degradation products of humic substances of MM > 5 kDa. In summary, the results of this study suggest that fungus-assisted degradation of HA and HA(Me) might be controlled using appropriate N- and C- sources required for fungus growth, which in turn would affect molecular mass distribution of soluble metallic

  11. A nuclear magnetic resonance study of the dynamics of organofluorine interactions with a dissolved humic acid.

    PubMed

    Longstaffe, James G; Courtier-Murias, Denis; Simpson, Andre J

    2016-02-01

    A quantitative understanding of the dynamics of the interactions between organofluorine compounds and humic acids will contribute to an improved understanding of the role that Natural Organic Matter plays as a mediator in the fate, transport and distribution of these contaminants in the environment. Here, Nuclear Magnetic Resonance (NMR) spectroscopy-based diffusion measurements are used to estimate the association dynamics between dissolved humic acid and selected organofluorine compounds: pentafluoroaniline, pentafluorophenol, potassium perfluorooctane sulfonate, and perfluorooctanoic acid. Under the conditions used here, the strength of the association with humic acid increases linearly as temperature decreases for all compounds except for perfluorooctanoic acid, which exhibits divergent behavior with a non-linear decrease in the extent of interaction as temperature decreases. A general interaction mechanism controlled largely by desolvation effects is suggested for all compounds examined here except for perfluorooctanoic acid, which exhibits a specific mode of interaction consistent with a proteinaceous binding site. Reverse Heteronuclear Saturation Transfer Difference NMR is used to confirm the identity and nature of the humic acid binding sites. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Effects of Humic Acid and Sunlight on the Generation and Aggregation State of Aqu/C60 Nanoparticles

    EPA Science Inventory

    Aqueous suspensions of nanoscale C60 aggregates (aqu/C60) were produced by stirring in water with Suwanee River Humic Acid (humic acid) and water from Call’s Creek, a small stream near Athens, GA. Time course experiments were conducted to determine the effects of sunlight and sol...

  13. Chemical and spectroscopic characterization of humic acids extracted from the bottom sediments of a Brazilian subtropical microbasin

    NASA Astrophysics Data System (ADS)

    Giovanela, M.; Crespo, J. S.; Antunes, M.; Adamatti, D. S.; Fernandes, A. N.; Barison, A.; da Silva, C. W. P.; Guégan, R.; Motelica-Heino, M.; Sierra, M. M. D.

    2010-09-01

    Humic substances (HS) perform a fundamental role in aquatic environments, exhibiting different levels of reactivity in retaining metal ions and organic pollutants. Also, they control the primary production of these ecosystems and act in the carbon sequestering process. In order to improve our understanding vis-à-vis the structural and functional features of HS from aquatic systems, this study aimed to chemically and spectroscopically characterize humic acids (HA) isolated from bottom sediment samples of a stream in a Brazilian subtropical microbasin by elemental analysis, and infrared (FT-IR), ultraviolet and visible (UV-Vis) and solid-state 13C nuclear magnetic resonance (CP-MAS 13C NMR) spectroscopies, thermogravimetry (TG), and scanning electron microscopy (SEM). Although all samples originated from the same environment, the data showed that the HA have distinct chemical and spectroscopic properties, and that the location and characteristics of the sampling points from which the sediments were collected played an important role in the differences observed. Furthermore, vascular plant matter is probably the main contributor to these samples.

  14. Effect of Humic Acid on As Redox Transformation and Kinetic Adsorption onto Iron Oxide Based Adsorbent (IBA)

    PubMed Central

    Fakour, Hoda; Lin, Tsair-Fuh

    2014-01-01

    Due to the importance of adsorption kinetics and redox transformation of arsenic (As) during the adsorption process, the present study elucidated natural organic matter (NOM) effects on As adsorption-desorption kinetics and speciation transformation. The experimental procedures were conducted by examining interactions of arsenate and arsenite with different concentrations of humic acid (HA) as a model representative of NOM, in the presence of iron oxide based adsorbent (IBA), as a model solid surface in three environmentally relevant conditions, including the simultaneous adsorption of both As and HA onto IBA, HA adsorption onto As-presorbed IBA, and As adsorption onto HA-presorbed IBA. Experimental adsorption-desorption data were all fitted by original and modified Lagergren pseudo-first and -second order adsorption kinetic models, respectively. Weber’s intraparticle diffusion was also used to gain insight into the mechanisms and rate controlling steps, which the results suggested that intraparticle diffusion of As species onto IBA is the main rate-controlling step. Different concentrations of HA mediated the redox transformation of As species, with a higher oxidation ability than reduction. The overall results indicated the significant effect of organic matter on the adsorption kinetics and redox transformation of As species, and consequently, the fate, transport and mobility of As in different environmentally relevant conditions. PMID:25325357

  15. Direct and indirect photodegradation of estriol in the presence of humic acid, nitrate and iron complexes in water solutions.

    PubMed

    Chen, Yong; Zhang, Kai; Zuo, Yuegang

    2013-10-01

    The photochemical behavior of a natural estrogen estriol (E3) was investigated in the presence of the natural photoreactive constituents including nitrate, iron(III), and humic acid (HA). The direct photodegradation of E3 increased with increasing incident light intensity, decreasing initial concentration of E3 and increasing pH in the range of 6.0 to 10.0. The direct photodegradation of the deprotonated speciation of E3 was much faster than that of its protonated form. The presence of NO3(-) and iron(III) promoted the photochemical loss of E3 in the aqueous solutions. The quenching experiments verified that hydroxyl radicals were predominantly responsible for the indirect photodegradation of E3. HA could act as photosensitizer, light screening agent and free radical quencher. For the first time, the enhancement or inhibition effect of HA on photodegradation was found to depend on the irradiation light intensity. HA enhanced the photodegradation of E3 under sunlight or weak irradiation of simulated sunlight. In contrast, under high irradiation light intensity, HA inhibited the photodegradation. The hydroxylation photoproducts were identified using GC-MS and the photodegradation pathway of E3 was proposed. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Effect of goethite coating and humic acid on the transport of bacteriophage PRD1 in columns of saturated sand

    NASA Astrophysics Data System (ADS)

    Foppen, J. W. A.; Okletey, S.; Schijven, J. F.

    2006-05-01

    The transport of bacteriophage PRD1, a model virus, was studied in columns containing sediment mixtures of quartz sand with goethite-coated sand and using various solutions consisting of monovalent and divalent salts and humic acid (HA). Without HA and in the absence of sand, the inactivation rate of PRD1 was found to be as low as 0.014 day - 1 (at 5 ± 3 °C), but in the presence of HA it was much lower (0.0009 day - 1 ), indicating that HA helps PRD1 to survive. When the fraction of goethite in the sediment was increased, the removal of PRD1 also increased. However, in the presence of HA, C/ C0 values of PRD1 increased by as much as 5 log units, thereby almost completely eliminating the effect of addition of goethite. The sticking efficiency was not linearly dependent on the amount of goethite added to the quartz sand; this is apparently due to surface charge heterogeneity of PRD1. Our results imply that, in the presence of dissolved organic matter (DOM), viruses can be transported for long distances thanks to two effects: attachment is poor because DOM has occupied favourable sites for attachment and inactivation of virus may have decreased. This conclusion justifies making conservative assumptions about the attachment of viruses when calculating protection zones for groundwater wells.

  17. Sorption of triclosan onto activated carbon, kaolinite and montmorillonite: effects of pH, ionic strength, and humic acid.

    PubMed

    Behera, Shishir Kumar; Oh, Seok-Young; Park, Hung-Suck

    2010-07-15

    Sorption of triclosan on three sorbents, viz., activated carbon, kaolinite and montmorillonite was studied as a function of pH, ionic strength and humic acid (HA) concentration through controlled batch experiments. Triclosan sorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the sorbents and degree of ionization of the sorbate. Sorption capacity of the sorbents increased with an increase in the ionic strength of solution. At low pH (pH 3), the overall increase in triclosan sorption was 1.2, approximately 4 and 3.5 times, respectively for activated carbon, kaolinite and montmorillonite when ionic strength was increased from 1x10(-3) to 5x10(-1) M. Triclosan sorption onto activated carbon decreased from 31.4 to 10.6 mg g(-1) by increasing the HA concentration to 200 mg C L(-1). However, during sorption onto kaolinite and montmorillonite, the effect of HA was very complex probably due to (i) hydrophobicity (log K(ow)=4.76) of triclosan; and (ii) complexation of HA with triclosan. Though triclosan sorption onto activated carbon is higher, the potential of kaolinite and montmorillonite in controlling the transport of triclosan in subsurface environment can still be appreciable. 2010 Elsevier B.V. All rights reserved.

  18. 13C-NMR spectra and contact time experiment for Skjervatjern fulvic and humic acids

    USGS Publications Warehouse

    Malcolm, R.L.

    1992-01-01

    The T(CP) and T(1p) time constants for Skjervatjern fulvic and humic acids were determined to be short with T(CP) values ranging from 0.14 ms to 0.53 ms and T(1p) values ranging from 3.3 ms to 5.9 ms. T(CP) or T(1p) time constants at a contact time of 1 ms are favorable for quantification of 13C-NMR spectra. Because of the short T(CP) values, correction factors for signal intensity for various regions of the 13C-NMR spectra would be necessary at contact times greater than 1.1 ms or less than 0.9 ms. T(CP) and T(1p) values have a limited non-homogeneity within Skjervatjern fulvic and humic acids. A pulse delay or repeat time of 700 ms is more than adequate for quantification of these 13C-NMR spectra. Paramagnetic effects in these humic substances are precluded due to low inorganic ash contents, low contents of Fe, Mn, and Co, and low organic free-radical contents. The observed T(CP) values suggest that all the carbon types in Skjervatjern fulvic and humic acids are fully cross-polarized before significant proton relaxation occurs. The 13C-NMR spectra for Skjervatjern fulvic acid is similar to most aquatic fulvic acids as it is predominantly aliphatic, low in aromaticity (fa1 = 24), low in phenolic content, high in carboxyl content, and has no resolution of a methoxyl peak. The 13C-NMR spectra for Skjervatjern humic acid is also similar to most other aquatic humic acids in that it is also predominantly aliphatic, high in aromaticity (fa1 = 38), moderate in phenolic content, moderate in carboxyl content, and has a clear resolution of a methoxyl carbon region. After the consideration of the necessary 13C-NMR experimental conditions, these spectra are considered to be quantitative. With careful consideration of the previously determined 13C-NMR experimental conditions, quantitative spectra can be obtained for humic substances in the future from the HUMEX site. Possible changes in humic substances due to acidification should be determined from 13C-NMR data.

  19. 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.

  20. The Implications of Fe2O3 and TiO2 Nanoparticles on the Removal of Trichloroethylene by Activated Carbon in the Presence and Absence of Humic Acid

    EPA Science Inventory

    The implications of Fe2O3 and TiO2 nanoparticles (NPs) on a granular activated carbon (GAC) adsorber and their impact on the removal of Trichloroethylene (TCE) were investigated in the presence of humic acid (HA). The surface charge of the GAC and NPs was obtained in the presence...

  1. Optimized Extraction Method To Remove Humic Acid Interferences from Soil Samples Prior to Microbial Proteome Measurements

    SciTech Connect

    Qian, Chen; Hettich, Robert L.

    The microbial composition and their activities in soil environments play a critical role in organic matter transformation and nutrient cycling, perhaps most specifically with respect to impact on plant growth but also more broadly to global impact on carbon and nitrogen-cycling. Liquid chromatography coupled to high performance mass spectrometry provides a powerful approach to characterize soil microbiomes; however, the limited microbial biomass and the presence of abundant interferences in soil samples present major challenges to soil proteome extraction and subsequent MS measurement. To address some of the major issues, we have designed and optimized an experimental method to enhance microbialmore » proteome extraction concomitant with minimizing the soil-borne humic substances co-extraction from soils. Among the range of interferences, humic substances are often the worst in terms of adversely impacting proteome extraction and mass spectrometry measurement. Our approach employs an in-situ detergent-based microbial lysis / TCA precipitation coupled with an additional acidification precipitation step at the peptide level which efficiently removes humic acids. By combing filtration and pH adjustment of the final peptide solution, the remaining humic acids can be differentially precipitated and removed with a membrane filter, thereby leaving much cleaner proteolytic peptide samples for MS measurement. As a result, this modified method is a reliable and straight-forward protein extraction method that efficiently removes soil-borne humic substances without inducing proteome sample loss or reducing or biasing protein identification in mass spectrometry.« less

  2. Optimized Extraction Method To Remove Humic Acid Interferences from Soil Samples Prior to Microbial Proteome Measurements

    DOE PAGES

    Qian, Chen; Hettich, Robert L.

    2017-05-24

    The microbial composition and their activities in soil environments play a critical role in organic matter transformation and nutrient cycling, perhaps most specifically with respect to impact on plant growth but also more broadly to global impact on carbon and nitrogen-cycling. Liquid chromatography coupled to high performance mass spectrometry provides a powerful approach to characterize soil microbiomes; however, the limited microbial biomass and the presence of abundant interferences in soil samples present major challenges to soil proteome extraction and subsequent MS measurement. To address some of the major issues, we have designed and optimized an experimental method to enhance microbialmore » proteome extraction concomitant with minimizing the soil-borne humic substances co-extraction from soils. Among the range of interferences, humic substances are often the worst in terms of adversely impacting proteome extraction and mass spectrometry measurement. Our approach employs an in-situ detergent-based microbial lysis / TCA precipitation coupled with an additional acidification precipitation step at the peptide level which efficiently removes humic acids. By combing filtration and pH adjustment of the final peptide solution, the remaining humic acids can be differentially precipitated and removed with a membrane filter, thereby leaving much cleaner proteolytic peptide samples for MS measurement. As a result, this modified method is a reliable and straight-forward protein extraction method that efficiently removes soil-borne humic substances without inducing proteome sample loss or reducing or biasing protein identification in mass spectrometry.« less

  3. Impact of humic acid on the photoreductive degradation of perfluorooctane sulfonate (PFOS) by UV/Iodide process.

    PubMed

    Sun, Zhuyu; Zhang, Chaojie; Chen, Pei; Zhou, Qi; Hoffmann, Michael R

    2017-12-15

    Iodide photolysis under UV illumination affords an effective method to produce hydrated electrons (e aq - ) in aqueous solution. Therefore, UV/Iodide photolysis can be utilized for the reductive degradation of many recalcitrant pollutants. However, the effect of naturally occurring organic matter (NOM) such as humic and fulvic acids (HA/FA), which may impact the efficiency of UV/Iodide photoreduction, is poorly understood. In this study, the UV photoreductive degradation of perfluorooctane sulfonate (PFOS) in the presence of I - and HA is studied. PFOS undergoes a relatively slow direct photoreduction in pure water, a moderate level of degradation via UV/Iodide, but a rapid degradation via UV/Iodide/HA photolysis. After 1.5 h of photolysis, 86.0% of the initial [PFOS] was degraded in the presence of both I - and HA with a corresponding defluorination ratio of 55.6%, whereas only 51.7% of PFOS was degraded with a defluorination ratio of 4.4% via UV/Iodide illumination in the absence of HA. The relative enhancement in the presence of HA in the photodegradation of PFOS can be attributed to several factors: a) HA enhances the effective generation of e aq - due to the reduction of I 2 , HOI, IO 3 - and I 3 - back to I - ; b) certain functional groups of HA (i.e., quinones) enhance the electron transfer efficiency as electron shuttles; c) a weakly-bonded association of I - and PFOS with HA increases the reaction probability; and d) absorption of UV photons by HA itself produces e aq - . The degradation and defluorination efficiency of PFOS by UV/Iodide/HA process is dependent on pH and HA concentration. As pH increases from 7.0 to 10.0, the enhancement effect of HA improves significantly. The optimal HA concentration for the degradation of 0.03 mM PFOS is 1.0 mg L -1 . Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Application of a continuous distribution model for proton binding by humic acids extracted from acidic lake sediments

    NASA Astrophysics Data System (ADS)

    Rhea, James R.; Young, Thomas C.

    1987-10-01

    The proton binding characteristics of humic acids extracted from the sediments of Cranberry Pond, an acidic water body located in the Adirondack Mountain region of New York State, were explored by the application of a multiligand distribution model. The model characterizes a class of proton binding sites by mean log K values and the standard deviations of log K values about the mean. Mean log K values and their relative abundances were determined directly from experimental titration data. The model accurately predicts the binding of protons by the humic acids for pH values in the range 3.5 to 10.0.

  5. Application of a continuous distribution model for proton binding by humic acids extracted from acidic lake sediments

    SciTech Connect

    Rhea, J.R.; Young, T.C.

    1987-01-01

    The proton binding characteristics of humic acids extracted from the sediments of Cranberry Pond, an acidic water body located in the Adirondack Mountain region of New York State, were explored by the application of a nultiligand distribution model. The model characterizes a class of proton binding sites by mean log K values and the standard deviations of log K values and the mean. Mean log K values and their relative abundances were determined directly from experimental titration data. The model accurately predicts the binding of protons by the humic acids for pH values in the range 3.5 to 10.0.

  6. Sorption and complexation of Eu(III) on alumina: effects of pH, ionic strength, humic acid and chelating resin on kinetic dissociation study.

    PubMed

    Wang, X; Xu, D; Chen, L; Tan, X; Zhou, X; Ren, A; Chen, Ch

    2006-04-01

    The effects of pH (pH=2-12), ionic strength (0.01-2 mol/l NaNO(3)) and humic acid on the sorption and complexation of Eu(III) on alumina were investigated by using batch techniques. The experiments were carried out at room temperature and under ambient conditions. The results indicate that the sorption of Eu(III) on alumina is strongly influenced by humic acid. The sorption of Eu(III) on alumina is significantly dependent on pH values and independent of ionic strength. The sorption of Eu(III) on alumina may be attributed to surface complexation. The species of Eu(III) on HA-alumina colloids is dominated by both HA and alumina, and the addition sequences of HA or Eu(III) to the ternary system do not influence the sorption of Eu(III) to HA-coated alumina. Kinetic dissociation of Eu(III) from bare and HA-coated alumina was also studied by using the chelating resin. The result was discussed by a pseudo-first-order kinetics model.

  7. Influence of humic acids on the adsorption of Basic Yellow 28 dye onto an iron organo-inorgano pillared clay and two hydrous ferric oxides.

    PubMed

    Zermane, Faiza; Cheknane, Benamar; Basly, Jean Philippe; Bouras, Omar; Baudu, Michel

    2013-04-01

    Effect of humic acids (HAs), macromolecules from natural organic matter, on the adsorption of Basic Yellow 28 is the aim of the present work. Three adsorbents were investigated in this study: an iron organo-inorgano pillared clay and two synthetic Hydrous Iron Oxide (Goethite and HFO). The surface charge was positive in the pH range of this study for the pillared clay; in contrast, it changes from positive to negative when the pH value increased (pH>9) for the two (oxy)hydroxides. Pseudo-first order kinetic rate constants and adsorption capacities increase from humic acid to BY 28. Adsorption isotherms of BY 28 and HA in single component were analysed using the Freundlich equation. Adsorption capacities increased sharply when the pH value of the dye solution was raised from 3 to 9. Increasing the pH medium from 3 to 9 reduces the HA adsorption capacities onto Fe-SMPM and iron oxyhydroxides, respectively. Fitting between measured and predicted sorption capacities of BY 28 and HA in a binary component system indicates that the Sheindorf-Rebuhn-Sheintuch (SRS) model, an extended Freundlich model, is able to describe the simultaneous adsorption of BY 28 and HA. Humic acids favourably affect the adsorption of BY 28, and a cooperative mechanism could be suggested. The synergetic effect existing between BY 28 and HA is shown by the interaction coefficients η12, which are generally high and increase with pH. Some phenomena have been advanced to explain this mechanism. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. C-1s NEXAFS spectroscopy reveals chemical fractionation of humic acid by cation-induced coagulation

    SciTech Connect

    Christl,I.; Kretzschmar, R.

    2007-01-01

    The influence of cation-induced coagulation on the chemical composition of dissolved and coagulated fractions of humic acid was investigated in batch coagulation experiments for additions of aluminum at pH 4 and 5, iron at pH 4, and calcium and lead at pH 6. The partitioning of organic carbon and metals was determined by analyzing total organic carbon and total metal contents of the dissolved phase. Both the dissolved and the coagulated humic acid fractions were characterized using synchrotron scanning transmission X-ray microscopy (STXM) and C-1s near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Intensities of {pi}* transitions of carboxyl carbon andmore » {sigma}* transitions of alkyl, O-alkyl, and carboxyl carbon decreased with increasing metal concentration for the dissolved humic acid fractions. This decrease was accompanied by an increase of the respective intensities in the coagulated fraction as shown for lead. Intensities of aromatic and phenolic carbon were affected to a larger extent only by aluminum and iron additions. The changes observed in the C-1s NEXAFS spectra coincided with an increasing removal of organic carbon from the dissolved phase with increasing total metal concentrations. We conclude that humic acid was chemically fractionated by cation-induced coagulation, which preferentially removed functional groups involved in metal-cation binding from solution.« less

  9. Chitosan, the marine functional food, is a potent adsorbent of humic acid.

    PubMed

    Chen, Jeen-Kuan; Yeh, Chao-Hsien; Wang, Lian-Chen; Liou, Tzong-Horng; Shen, Chia-Rui; Liu, Chao-Lin

    2011-12-01

    Chitosan is prepared by the deacetylation of chitin, the second-most abundant biopolymer in nature, and has applicability in the removal of dyes, heavy metals and radioactive waste for pollution control. In weight-reduction remedies, chitosan is used to form hydrogels with lipids and to depress the intestinal absorption of lipids. In this study, an experimental method was implemented to simulate the effect of chitosan on the adsorption of humic acid in the gastrointestinal tract. The adsorption capacity of chitosan was measured by its adsorption isotherm and analyzed using the Langmuir equation. The results showed that 3.3 grams of humic acid was absorbed by 1 gram of chitosan. The adsorption capacity of chitosan was much greater than that of chitin, diethylaminoethyl-cellulose or activated charcoal. Cellulose and carboxymethyl-cellulose, a cellulose derivative with a negative charge, could not adsorb humic acid in the gastrointestinal tract. This result suggests that chitosan entraps humic acid because of its positive charge.

  10. Coagulant properties of Moringa oleifera protein preparations: application to humic acid removal.

    PubMed

    Santos, Andréa F S; Paiva, Patrícia M G; Teixeira, José A C; Brito, António G; Coelho, Luana C B B; Nogueira, Regina

    2012-01-01

    This work aimed to characterize the coagulant properties of protein preparations from Moringa oleifera seeds in the removal of humic acids from water. Three distinct preparations were assayed, namely extract (seeds homogenized with 0.15 M NaCl), fraction (extract precipitated with 60% w/v ammonium sulphate) and cMoL (protein purified with guar gel column chromatography). The extract showed the highest coagulant activity in a protein concentration between 1 mg/L and 180 mg/L at pH 7.0. The zeta potential of the extract (-10 mV to -15 mV) was less negative than that of the humic acid (-41 mV to -42 mV) in a pH range between 5.0 and 8.0; thus, the mechanism that might be involved in this coagulation activity is adsorption and neutralization of charges. Reduction of total organic carbon (TOC) and dissolved organic carbon (DOC) was observed in water samples containing 9 mg/L carbon as humic acid when treated with 1 mg/L of the extract. A decrease in colour and in the aromatic content of the treated water was also observed. These results suggested that the extract from M. oleifera seeds in a low concentration (1 mg/L) can be an interesting natural alternative for removing humic acid from water in developing countries. The extract dose determined in the present study does not impart odour or colour to the treated water.

  11. Effect of Humic Acid and Sunlight on the Generation of aqu/C60

    EPA Science Inventory

    Little is known about the effect of sunlight and natural organic matter, such as humic acid, on the aqueous suspension of fullerene C60. This knowledge gap limits our ability to determine the environmental impact of potential environmental releases of these materials. Aqueous sus...

  12. THE ROLE OF SELECTED CATIONS IN THE FORMATION OF PSEUDOMICELLES IN AQUEOUS HUMIC ACID (R822832)

    EPA Science Inventory

    The fluorescence intensity enhancement of a pyrene probe in aqueous humic acid solutions was assessed in terms of added lanthanide and thorium cations. Among the trivalent ions it was found that size played a role, with the small Lu3+ ion producing the greatest increase in pyrene...

  13. Influence of humic acid addition on the degradation of pharmaceuticals by biofilms in effluent wastewater.

    PubMed

    Tang, Kai; Escola Casas, Monica; Ooi, Gordon T H; Kaarsholm, Kamilla M S; Bester, Kai; Andersen, Henrik R

    2017-05-01

    The degradation of organic micropollutants in wastewater treatment is suspected to depend on co-degradation i.e. be dependent on concentrations of substrate. This complicates predicting and modelling their fate. The effect of humic acid, as a model for complex organic substrate, was investigated in relation to the biodegradation of pharmaceuticals by suspended biofilm carriers adapted to polishing effluent water from a tertiary sewage treatment plant. Twelve out of 22 investigated pharmaceuticals were significantly biodegradable. The biodegradation rate constants of ten of those compounds were increasing with increased humic acid concentrations. At the highest humic acid concentration (30mgC/L), the biodegradation rate constants were four times higher than the biodegradation rate constants without added humic acid. This shows that the presence of complex substrate stimulates degradation via a co-metabolism-like mechanism and competitive inhibition does not occur. Increases of rate constant per mgC/L are tentatively calculated. Copyright © 2017 Elsevier GmbH. All rights reserved.

  14. Chitosan, the Marine Functional Food, Is a Potent Adsorbent of Humic Acid

    PubMed Central

    Chen, Jeen-Kuan; Yeh, Chao-Hsien; Wang, Lian-Chen; Liou, Tzong-Horng; Shen, Chia-Rui; Liu, Chao-Lin

    2011-01-01

    Chitosan is prepared by the deacetylation of chitin, the second-most abundant biopolymer in nature, and has applicability in the removal of dyes, heavy metals and radioactive waste for pollution control. In weight-reduction remedies, chitosan is used to form hydrogels with lipids and to depress the intestinal absorption of lipids. In this study, an experimental method was implemented to simulate the effect of chitosan on the adsorption of humic acid in the gastrointestinal tract. The adsorption capacity of chitosan was measured by its adsorption isotherm and analyzed using the Langmuir equation. The results showed that 3.3 grams of humic acid was absorbed by 1 gram of chitosan. The adsorption capacity of chitosan was much greater than that of chitin, diethylaminoethyl-cellulose or activated charcoal. Cellulose and carboxymethyl-cellulose, a cellulose derivative with a negative charge, could not adsorb humic acid in the gastrointestinal tract. This result suggests that chitosan entraps humic acid because of its positive charge. PMID:22363235

  15. DYNAMIC CONDUCTIVITY MEASUREMENTS IN HUMIC AND FULVIC ACID SOLUTIONS. (R828158)

    EPA Science Inventory

    Conductivity changes of dilute aqueous humic and fulvic acids solutions were monitored after the addition of small quantities of Cu, Cd, Pb, and Zn. The solutions were stirred at a constant and reproducible rate, and measurements proceeded until stable conductivities were atta...

  16. Removal of dissolved humic acid from water by photocatalytic oxidation using a silver orthophosphate semiconductor

    SciTech Connect

    Hatakeyama, Keisuke, E-mail: hatakeyamak@pref.tottori.jp; Okuda, Masukazu; Kuki, Takahiro

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► The photocatalytic property of a silver orthophosphate (Ag{sub 3}PO{sub 4}) was investigated for humic acid degradation. ► The Ag{sub 3}PO{sub 4} shows high photocatalytic activity under visible light. ► The photocatalytic activity was greatly improved by employing the precipitation method. -- Abstract: In order to remove dissolved organic matter such as humic acid from water, a silver orthophosphate (Ag{sub 3}PO{sub 4}) was newly employed as a heterogeneous photocatalyst. Here, Ag{sub 3}PO{sub 4} was prepared by simple ion-exchange and precipitation methods, and the physico-chemical properties were characterized by X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, scanningmore » electron microscopy, particle distribution measurements and Brunauer–Emmett–Teller (BET) analysis. The degradation of humic acid was faster over Ag{sub 3}PO{sub 4} catalyst than over conventional TiO{sub 2} (P-25). The total photocatalytic properties were improved by employing not an ion-exchange method but a precipitation method; humic acid degradation was performed with a removal ratio of dissolved organic carbon of 75% under visible light (λ = 451 nm) for 2-h irradiation.« less

  17. THE EFFECT OF MOLECULAR SIZE ON HUMIC ACID ASSOCIATIONS (R822832)

    EPA Science Inventory

    Abstract

    Aqueous solutions of two humic acids were subjected to UV photolysis, resulting in chain scission of the solute. The molecular fragments were found to have diminished detergent properties, indicated by a reduced tendency to associate with small hydrophobic spe...

  18. Bond Dissociation Free Energies (BDFEs) of the Acidic H-A Bonds in HA(*)(-) Radical Anions by Three Different Pathways.

    PubMed

    Zhao, Yongyu; Bordwell, Frederick G.

    1996-09-20

    Cleavage of radical anions, HA(*)(-), have been considered to give either H(*) + A(-) (path a) or H(-) + A(*) (path b), and factors determining the preferred mode of cleavage have been discussed. It is conceivable that cleavage to give a proton and a radical dianion, HA(*)(-) right harpoon over left harpoon H(+) + A(*)(2)(-) (path c), might also be feasible. A method, based on a thermodynamic cycle, to estimate the bond dissociation free energy (BDFE) by path c has been devised. Comparison of the BDFEs for cleavage of the radical anions derived from 24 nitroaromatic OH, SH, NH, and CH acids by paths a, b, c has shown that path c is favored thermodynamically.

  19. Impact of humic acids on the colonic microbiome in healthy volunteers.

    PubMed

    Swidsinski, Alexander; Dörffel, Yvonne; Loening-Baucke, Vera; Gille, Christoph; Reißhauer, Anne; Göktas, Onder; Krüger, Monika; Neuhaus, Jürgen; Schrödl, Wieland

    2017-02-07

    To test the effects of humic acids on innate microbial communities of the colon. We followed the effects of oral supplementation with humic acids (Activomin ® ) on concentrations and composition of colonic microbiome in 14 healthy volunteers for 45 d. 3 × 800 mg Activomin ® were taken orally for 10 d followed by 3 × 400 mg for 35 d. Colonic microbiota were investigated using multicolor fluorescence in situ hybridization (FISH) of Carnoy fixated and paraffin embedded stool cylinders. Two stool samples were collected a week prior to therapy and one stool sample on days 10, 31 and 45. Forty-one FISH probes representing different bacterial groups were used. The sum concentration of colonic microbiota increased from 20% at day 10 to 30% by day 31 and remained stable until day 45 (32%) of humic acid supplementation ( P < 0.001). The increase in the concentrations in each person was due to growth of preexisting groups. The individual microbial profile of the patients remained unchanged. Similarly, the bacterial diversity remained stable. Concentrations of 24 of the 35 substantial groups increased from 20% to 96%. Two bacterial groups detected with Bac303 ( Bacteroides ) and Myc657 (mycolic acid-containing Actinomycetes ) FISH probes decreased ( P > 0.05). The others remained unaffected. Bacterial groups with initially marginal concentrations (< 0.1 × 10 9 /mL) demonstrated no response to humic acids. The concentrations of pioneer groups of Bifidobacteriaceae , Enterobacteriaceae and Clostridium difficile increased but the observed differences were statistically not significant. Humic acids have a profound effect on healthy colonic microbiome and may be potentially interesting substances for the development of drugs that control the innate colonic microbiome.

  20. Impact of humic acids on the colonic microbiome in healthy volunteers

    PubMed Central

    Swidsinski, Alexander; Dörffel, Yvonne; Loening-Baucke, Vera; Gille, Christoph; Reißhauer, Anne; Göktas, Onder; Krüger, Monika; Neuhaus, Jürgen; Schrödl, Wieland

    2017-01-01

    AIM To test the effects of humic acids on innate microbial communities of the colon. METHODS We followed the effects of oral supplementation with humic acids (Activomin®) on concentrations and composition of colonic microbiome in 14 healthy volunteers for 45 d. 3 × 800 mg Activomin® were taken orally for 10 d followed by 3 × 400 mg for 35 d. Colonic microbiota were investigated using multicolor fluorescence in situ hybridization (FISH) of Carnoy fixated and paraffin embedded stool cylinders. Two stool samples were collected a week prior to therapy and one stool sample on days 10, 31 and 45. Forty-one FISH probes representing different bacterial groups were used. RESULTS The sum concentration of colonic microbiota increased from 20% at day 10 to 30% by day 31 and remained stable until day 45 (32%) of humic acid supplementation (P < 0.001). The increase in the concentrations in each person was due to growth of preexisting groups. The individual microbial profile of the patients remained unchanged. Similarly, the bacterial diversity remained stable. Concentrations of 24 of the 35 substantial groups increased from 20% to 96%. Two bacterial groups detected with Bac303 (Bacteroides) and Myc657 (mycolic acid-containing Actinomycetes) FISH probes decreased (P > 0.05). The others remained unaffected. Bacterial groups with initially marginal concentrations (< 0.1 × 109/mL) demonstrated no response to humic acids. The concentrations of pioneer groups of Bifidobacteriaceae, Enterobacteriaceae and Clostridium difficile increased but the observed differences were statistically not significant. CONCLUSION Humic acids have a profound effect on healthy colonic microbiome and may be potentially interesting substances for the development of drugs that control the innate colonic microbiome. PMID:28223733

  1. Potential origin and formation for molecular components of humic acids in soils

    NASA Astrophysics Data System (ADS)

    Hatcher, Patrick; DiDonato, Nicole; Waggoner, Derek

    2016-04-01

    Humification is defined as the process by which plant and microbial debris are transformed in to humic substances. Proposed pathways for the formation of humic substances, include the lignin and lignin decomposition theories, the lignin-polyphenol theory as well as the melanoidin pathway. It is generally accepted that a combination of several of these pathways with some modifications may be responsible for producing humic substances. The current study examines humic acids from numerous soil samples to demonstrate their molecular composition. In addition we provide an explanation for the formation of these molecules that introduces a new perspective of the humification process. Our work utilizes advanced analytical techniques such as ESI-FTICR-MS and solid state NMR to more completely characterize humic acids at the molecular level. Methods Humic acids were extracted from soils using 0.5 M NaOH followed by treatment with a Dowex™ ion-exchange resin to remove sodium ions. Solid State 13C NMR spectra were obtained on a Bruker 400 MHz Avance II spectrometer equipped with a 4 mm solid state MAS probe. ESI-FTICR-MS analysis was conducted in the negative ion mode on a Bruker Daltonics 12 Tesla Apex Qe FTICR-MS instrument equipped with an Apollo II ESI source. Results: Soil humic acids from numerous soils were investigated in this study. The molecular formulas calculated from ultrahigh resolution mass spectra of well humified soils fall clearly into two predominant regions consisting of condensed aromatic molecules as well as high H/C, low O/C carboxyl-containing aliphatic molecules (CCAM). In contrast, the spectral data for humic acids from a poorly humified spodosol soil show a less dramatic separation of these regions, with relatively more molecular formula plotting in the lignin-like region and relatively fewer condensed aromatic molecules. From the mass spectral observations made for the humic acids, we can readily discern a relationship based on degree of

  2. The aqueous photolysis of α-pinene in solution with humic acid

    USGS Publications Warehouse

    Goldberg, Marvin C.; Cunningham, Kirkwood M.; Aiken, George R.; Weiner, Eugene R.; ,

    1992-01-01

    Terpenes are produced abundantly by environmental processes but are found in very low concentrations in natural waters. Aqueous photolysis of solutions containing α-pinene, a representative terpene, in the presence of humic acid resulted in degradation of the pinene. Comparison of this reaction to photolysis of α-pinene in the presence of methylene blue leads to the conclusion that the reactive pathway for the abiotic degradation of α-pinene is due to reaction with singlet oxygen produced by irradiation of the humic material. The initial product of single oxygen and α-pinene is a hydroperoxide. Since humic materials are prevalent in most natural waters, this mechanism of photodecomposition for α-pinene probably also applies to other terpenes in surface waters and may be reasonably considered to contribute to their low environmental concentration.

  3. Coagulation removal of humic acid-stabilized carbon nanotubes from water by PACl: influences of hydraulic condition and water chemistry.

    PubMed

    Ma, Si; Liu, Changli; Yang, Kun; Lin, Daohui

    2012-11-15

    Discharged carbon nanotubes (CNTs) can adsorb the widely-distributed humic acid (HA) in aquatic environments and thus be stabilized. HA-stabilized CNTs can find their way into and challenge the potable water treatment system. This study investigated the efficiency of coagulation and sedimentation techniques in the removal of the HA-stabilized multi-walled carbon nanotubes (MWCNTs) using polyaluminum chloride (PACl) as a coagulant, with a focus on the effects of hydraulic conditions and water chemistry. Stirring speeds in the mixing and reacting stages were gradually changed to examine the effect of the hydraulic conditions on the removal rate. The stirring speed in the reacting stage affected floc formation and thereby had a greater impact on the removal rate than the stirring speed in the mixing stage. Water chemistry factors such as pH and ionic strength had a significant effect on the stability of MWCNT suspension and the removal efficiency. Low pH (4-7) was favorable for saving the coagulant and maintaining high removal efficiency. High ionic strength facilitated the destabilization of the HA-stabilized MWCNTs and thereby lowered the required PACl dosage for the coagulation. However, excessively high ionic strength (higher than the critical coagulation concentration) decreased the maximum removal rate, probably by inhibiting ionic activity of PACl hydrolyzate in water. These results are expected to shed light on the potential improvement of coagulation removal of aqueous stabilized MWCNTs in water treatment systems. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Effect of humic acid on nickel(II) sorption to Ca-montmorillonite by batch and EXAFS techniques study.

    PubMed

    Hu, Jun; Tan, Xiaoli; Ren, Xuemei; Wang, Xiangke

    2012-09-21

    The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA-montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni-HA-montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of ∼6 O atoms at the interatomic distances of ∼2.04 Å in an octahedral structure. At high pH, binary Ni-montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni-Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA-Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni-Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni-Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.

  5. Two-dimensional correlation spectroscopic analysis on the interaction between humic acids and TiO2 nanoparticles.

    PubMed

    Chen, Wei; Qian, Chen; Liu, Xiao-Yang; Yu, Han-Qing

    2014-10-07

    The elucidation of the interaction between TiO2 nanoparticles (NPs) and natural organic matter (NOM) can help one to better understand the fates, features, and environmental impacts of NPs. In this work, two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (CoS) assisted by the fluorescence excitation-emission matrix (EEM) method is used to explore the interaction mechanism of humic acid (HA) with TiO2 NPs at a molecular level. The results show that the C═O bonds (carboxylate, amide, quinone, or ketone) and C-O bonds (phenol, aliphatic C-OH, and polysaccharide) of HA play important roles in their interaction with TiO2 NPs. The adsorption process of HA onto the surface of TiO2 NPs is different from the bonding process of the two species in solution. The forms of the relevant groups of HA and their consequent reaction with TiO2 NPs are affected to a great extent by the solution pH and the surface charge of NPs. The 2D-FTIR-CoS method is found to be able to construct a comprehensive picture about the NOM-TiO2 NPs interaction process. This 2D-FTIR-CoS approach might also be used to probe other complicated interaction processes in natural and engineered environments.

  6. Chlorpyrifos-methyl solubilisation by humic acids used as bio-surfactants extracted from lignocelluloses and kitchen wastes.

    PubMed

    Scaglia, Barbara; Baglieri, Andrea; Tambone, Fulvia; Gennari, Mara; Adani, Fabrizio

    2016-09-01

    Chlorpyrifos-methyl (CLP-m) is a widely used organophosphate insecticide that can accumulate in soil and become toxic to humans. CLP-m can be removed from soil by its solubilisation using synthetic surfactants. However, synthetic surfactants can accumulate in soil causing contamination phenomena themselves. Bio-surfactants can be used as an alternative to synthetic ones, reducing costs and environmental issues. In this work, humic acid (HA) extracted from raw biomasses, i.e. lignocelluloses (HAL) and lignocelluloses plus kitchen food waste (HALF), corresponding composts (C) (HALC and HALFC) and leonardite (HAc), were tested in comparison with commercial surfactants, i.e. SDS, Tween 20 and DHAB, to solubilize CLP-m. Results obtained indicated that only biomass-derived HA, composted biomass-derived HA, and SDS solubilized CLP-m: SDS = 0.006; HAL = 0.007; HALC = 0.009 g; HALF = 0.025; HALFC = 0.024) (g CLP-m g(-1) surfactant). Lignocelluloses HAs (HAL, HALF) solubilized CLP-m just as well as SDS while lignocellulosic plus kitchen food waste HA (HALF, HALFC) showed a three times higher CLP-m solubilisation capability. This difference was attributed to the higher concentration of alkyl-Carbon that creates strong links with CLP-m in the hydrophobic micelle-core of the surfactants. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Size and shape of soil humic acids estimated by viscosity and molecular weight.

    PubMed

    Kawahigashi, Masayuki; Sumida, Hiroaki; Yamamoto, Kazuhiko

    2005-04-15

    Ultrafiltration fractions of three soil humic acids were characterized by viscometry and high performance size-exclusion chromatography (HPSEC) in order to estimate shapes and hydrodynamic sizes. Intrinsic viscosities under given solute/solvent/temperature conditions were obtained by extrapolating the concentration dependence of reduced viscosities to zero concentration. Molecular mass (weight average molecular weight (M (w)) and number average molecular weight (M (n))) and hydrodynamic radius (R(H)) were determined by HPSEC using pullulan as calibrant. Values of M (w) and M (n) ranged from 15 to 118 x 10(3) and from 9 to 50 x 10(3) (g mol(-1)), respectively. Polydispersity, as indicated by M (w)/M (n), increased with increasing filter size from 1.5 to 2.4. The hydrodynamic radii (R(H)) ranged between 2.2 and 6.4 nm. For each humic acid, M (w) and [eta] were related. Mark-Houwink coefficients calculated on the basis of the M (w)-[eta] relationships suggested restricted flexible chains for two of the humic acids and a branched structure for the third humic acid. Those structures probably behave as hydrated sphere colloids in a good solvent. Hydrodynamic radii of fractions calculated from [eta] using Einstein's equation, which is applicable to hydrated sphere colloids, ranged from 2.2 to 7.1 nm. These dimensions are fit to the size of nanospaces on and between clay minerals and micropores in soil particle aggregates. On the other hand, the good agreement of R(H) values obtained by applying Einstein's equation with those directly determined by HPSEC suggests that pullulan is a suitable calibrant for estimation of molecular mass and size of humic acids by HPSEC.

  8. Protonated o-semiquinone radical as a mimetic of the humic acids native radicals: A DFT approach to the molecular structure and EPR properties

    NASA Astrophysics Data System (ADS)

    Witwicki, Maciej; Jezierska, Julia

    2012-06-01

    Organic radicals are known to be an indispensable component of the humic acids (HA) structure. In HA two forms of radicals, stable (native) and short-lived (transient), are identified. Importantly, these radical forms can be easily differentiated by electron paramagnetic resonance (EPR) spectroscopy. This article provides a DFT-based insight into the electronic and molecular structure of the native radicals. The molecular models including an increase of the radical aromaticity and the hydrogen bonding between the radical and other functional groups of HA are taken under investigation. In consequence the interesting pieces of information on the structure of the native radical centers in HA are revealed and discussed, especially in terms of differences between the electronic structure of the native and transient forms.

  9. The Relative Abundance of Oxygen Alkyl-Related Groups in Aliphatic Domains Is Involved in the Main Pharmacological-Pleiotropic Effects of Humic Acids

    PubMed Central

    Vashishta, Aruna; Fuentes, Marta; Baigorri, Roberto; Garcia-Mina, Jose M.; Yvin, Jean-Claude

    2013-01-01

    Abstract Despite the rather common presence of humic acid (HA), our full knowledge of its biological effect is still lacking. In this article, we first performed a physicochemical characterization of several HAs, and next, we evaluated their ability to affect interleukin-2 secretion, antibody secretion, wound healing (an in vitro model using HaCaT cells), cancer growth (the Lewis lung carcinoma model), and protection against hepatotoxicity. In all tested reactions, HA showed significant stimulation on immune reactions, including suppression of cancer growth and inhibition of lipopolysaccharide-induced hepatotoxicity. These effects were dependent on its chemical properties. The pleiotropic effects of HA observed in this article suggest the possible role of these compounds in human nutrition. PMID:23875902

  10. Sorption of selected organic compounds from water to a peat soil and its humic-acid and humin fractions: Potential sources of the sorption nonlinearity

    USGS Publications Warehouse

    Chiou, C.T.; Kile, D.E.; Rutherford, D.W.; Sheng, G.; Boyd, S.A.

    2000-01-01

    The sorption isotherms of ethylene dibromide (EDB), diuron (DUN), and 3,5-dichlorophenol (DCP) from water on the humic acid and humin fractions of a peat soil and on the humic-acid of a muck soil have been measured. The data were compared with those of the solutes with the whole peat from which the humic-acid (HA) and humin (HM) fractions were derived and on which the sorption of the solutes exhibited varying extents of nonlinear capacities at low relative concentrations (C(e)/S(w)). The HA fraction as prepared by the density-fractionated method is relatively pure and presumably free of high- surface-area carbonaceous material (HSACM) that is considered to be responsible for the observed nonlinear sorption for nonpolar solutes (e.g., EDB) on the peat; conversely, the base-insoluble HM fraction as prepared is presumed to be enriched with HSACM, as manifested by the greatly higher BET- (N2) surface area than that of the whole peat. The sorption of EDB on HA exhibits no visible nonlinear effect, whereas the sorption on HM shows an enhanced nonlinearity over that on the whole peat. The sorption of polar DUN and DCP on HA and HM display nonlinear effects comparable with those on the whole peat; the effects are much more significant than those with nonpolar EDB. These results conform to the hypothesis that adsorption onto a small amount of strongly adsorbing HSACM is largely responsible for the nonlinear sorption of nonpolar solutes on soils and that additional specific interactions with the active groups of soil organic matter are responsible for the generally higher nonlinear sorption of the polar solutes.

  11. BIOAVAILABILITY AND TROPHIC TRANSFER OF HUMIC-BOUND COPPER FROM BACTERIA TO ZOOPLANKTON

    EPA Science Inventory

    The effect of humic acid (HA) on uptake and transfer of Cu by selected marine organisms from the microbial loop was determined. Bacteria grown to stationary phase in cultures with and without 15 ug Cu l -1 and with and without 10 mg Suwannee River Humic Acid (SRHA) l -1 were fed ...

  12. The effect of humic acid on the aggregation of titanium dioxide nanoparticles under different pH and ionic strengths.

    PubMed

    Zhu, Miao; Wang, Hongtao; Keller, Arturo A; Wang, Tao; Li, Fengting

    2014-07-15

    With the increasingly widespread use of titanium dioxide nanoparticles (TiO2 NPs), the particles' environmental impacts have attracted concern, making it necessary to understand the fate and transport of TiO2 NPs in aqueous media. In this study, we investigated TiO2 NP aggregation caused by the effects of humic acid (HA), ionic strength (IS) and different pH using dynamic light scattering (DLS) to monitor the size distribution of the TiO2 NPs continuously. It was determined that HA can influence the stability of TiO2 NPs through charge neutralization, steric hindrance and bridging effects. In the absence of IS, aggregation was promoted by adding HA only when the pH (pH=4) is less than the point of zero charge for the TiO2 NPs (pHPZC≈6) because HA reduces the zeta potential of the TiO2 NPs via charge neutralization. At pH=4 and when the concentration of HA is 94.5 μg/L, the zeta potential of TiO2 NPs is close to zero, and they reach an aggregation maximum. A higher concentration of HA results in more negatively charged TiO2 NP surfaces, which hinder their aggregation. When the pH is 5.8, HA enhances the negative zeta potential of the TiO2 NPs and increases their stability via electrostatic repulsion and steric hindrance. When the pH (pH=8) is greater than pHpzc, the zeta potential of the TiO2 NPs is high (~40 mV), and it barely changes with increasing HA concentration. Thus, the TiO2 NPs are notably stable, and their size does not grow at pH8. The increase in the critical coagulation concentration (CCC) of TiO2 NPs indicated that there is steric hindrance after the addition of HA. HA can enhance the coagulation of TiO2 NPs, primarily due to bridging effect. These findings are useful in understanding the size change of TiO2 NPs, as well as the removal of TiO2 NPs and HA from aqueous media. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. UPTAKE OF LIPOPHILIC CADMIUM COMPLEXES BY THREE GREEN ALGAE: INFLUENCE OF HUMIC ACID AND ITS pH DEPENDENCE(1).

    PubMed

    Boullemant, Amiel; Le Faucheur, Séverine; Fortin, Claude; Campbell, Peter G C

    2011-08-01

    Cadmium forms neutral, lipophilic CdL2 (0) complexes with diethyldithiocarbamate (L = DDC) and with ethylxanthate (L = XANT). In a synthetic solution and in the absence of natural dissolved organic matter (DOM), for a given total Cd concentration, uptake of these complexes by unicellular algae is much faster than the uptake of the free Cd(2+) cation. The objective of the present study was to determine how this enhanced uptake of the lipophilic CdL2 (0) complexes was affected by the presence of natural DOM (Suwannee River humic acid, SRHA). Experiments were performed with Cd(DDC)2 (0) and Cd(XANT)2 (0) at two pH values (7.0 and 5.5) and with the three chlorophytes [Chlamydomonas reinhardtii P. A. Dang., Pseudokirchneriella subcapitata (Korshikov) Hindák, Chlorella fusca var. vacuolata Shihira et R. W. Krauss]. Short-term uptake (30-40 min) of the CdL2 (0) complexes was followed in the absence and presence of SRHA (6.5 mg C · L(-1) ). Acidification from pH 7.0 to 5.5 decreased CdL2 (0) uptake by the three algae, in the presence or absence of humic acid (HA). The dominant effect of the HA was to decrease Cd uptake, due to its interaction with the CdL2 (0) complexes in solution. However, if uptake of the free CdL2 (0) complexes was compared in the presence and absence of HA, in four of eight cases initial uptake rate constants (ki ) were significantly higher (P < 0.05) in the presence of the HA, suggesting the operation of an interfacial effect of the HA at the algal cell membrane, favoring uptake of CdL2 (0) . Overall, the experimental results suggest that neutral metal complexes will be less bioavailable in natural waters than they are in synthetic laboratory media in the absence of natural DOM. © 2011 Phycological Society of America.

  14. Effect of anions and humic acid on the performance of nanoscale zero-valent iron particles coated with polyacrylic acid.

    PubMed

    Kim, Hong-Seok; Ahn, Jun-Young; Kim, Cheolyong; Lee, Seockheon; Hwang, Inseong

    2014-10-01

    Effects of anions (NO3(-), HCO3(-), Cl(-), SO4(2-)) and humic acid on the reactivity and core/shell chemistries of polyacrylic acid-coated nanoscale zero-valent iron (PAA-NZVI) and inorganically modified NZVI (INORG-NZVI) particles were investigated. The reactivity tests under various ion concentrations (0.2-30mN) revealed the existence of a favorable molar ratio of anion/NZVI that increased the reactivity of NZVI particles. The presence of a relatively small amount of humic acid (0.5mgL(-1)) substantially decreased the INORG-NZVI reactivity by 76%, whereas the reactivity of PAA-NZVI decreased only by 12%. The XRD and TEM results supported the role of the PAA coating of PAA-NZVI in impeding the oxidation of the Fe(0) core by groundwater solutes. This protective role provided by the organic coating also resulted in a 2.3-fold increase in the trichloroethylene (TCE) reduction capacity of PAA-NZVI compared to that of INORG-NZVI in the presence of anions/humic acid. Ethylene and ethane were simultaneously produced as the major reduction products of TCE in both NZVI systems, suggesting that a hydrodechlorination occurred without the aid of metallic catalysts. The PAA coating, originally designed to improve the mobility of NZVI, enhanced TCE degradation performances of NZVI in the presence of anions and humic acid. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Role of Secondary Particle Formation in the Persistence of Silver Nanoparticles in Humic Acid Containing Water under Light Irradiation.

    PubMed

    Zhang, Tuoya; Lu, Dawei; Zeng, Lixi; Yin, Yongguang; He, Yujian; Liu, Qian; Jiang, Guibin

    2017-12-19

    The wide use of silver nanoparticles (AgNPs) leads to the increasing release of AgNPs into the environment. Dissolved organic matter (DOM) is a key factor affecting the behaviors and fate of AgNPs in the aquatic environment. However, the mechanisms for the DOM-mediated transformations of AgNPs are still not fully understood. In this study, we investigated the persistence of AgNPs in the aquatic environment in the presence of different concentrations of humic acid (HA) over periods of time up to 14 days. The Ag species were monitored and characterized by absorption spectrometry, transmission electron microscopy (TEM), inductively coupled plasma mass spectrometry (ICP-MS), and multicollector ICP-MS (MC-ICP-MS). Results showed that the long-term persistence of AgNPs in HA-containing water was determined by two critical concentrations of HA. When the HA concentration exceeded a lower critical value, AgNPs could be persistent in the solution, and a large number of AgNPs were formed secondarily from the HA-induced reduction of the Ag + ions released from the primary AgNPs, causing a redistribution of the particle size. With the HA concentration above a higher critical value, AgNPs could persist in the solution without a significant change in particle size. Notably, we used Ag isotope fractionation to investigate the transformation mechanism of AgNPs. The natural isotopic analysis by MC-ICP-MS revealed that the size redistribution of AgNPs caused significant Ag isotope fractionation, which gave additional evidence for the proposed mechanisms. This study provides new insights into the environmental fate of engineered AgNPs and highlights the usefulness of stable isotope fractionation in environmental nanotechnology.

  16. Metabolism, survival, and gene expression of Pseudomonas putida to hematite nanoparticles mediated by surface-bound humic acid

    SciTech Connect

    Ouyang, Kai; Walker, Sharon L.; Yu, Xiao-Ying

    Natural organic matter (NOM) is likely to coat naturally occurring nanoparticles (NNPs) in the soil environment and poses distinct effects on the interaction between NPs and soil microorganisms, however such topic has not been well investigated. This study explored the influence of nanoparticle surface-bound humic acid (HA, as a model NOM) on the toxicity of hematite NPs (i.e., nano-Fe2O3) to Pseudomonas putida (P. putida). Results showed that nano-Fe2O3 could inhibit the bacterial growth with an IC50 of 23.58 mg L-1, while nanoparticle surface-bound HA could significantly alleviate the P. putida toxicity of nano-Fe2O3. IC50 of nano-Fe2O3 increased to 4774.23 mgmore » L-1 as a result of surface-saturation by HA. Co-precipitation experiment and transmission electron microscopy observation revealed that nanoparticle surface-bound HA prevented the adhesion of nano-Fe2O3 to the cells as well as limited cell internalization of nanoparticles due to the increased electrostatic repulsion. The generation of intracellular reactive oxygen species (ROS) was significantly limited by the nanoparticle surface-bound HA. The prevention of adhesion and inhibition of ROS generation could account for the HA-mitigated nanotoxicity. Interfacial interactions between hematite NPs and cell membrane were also evaluated on the basis of the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, and the magnitude of interaction energy barrier correlated well with the 48 h LC50 data of hematite NPs to P. putida. This result implies that metal oxide NPs with strong association with the cell surface might induce more severe cytotoxicity in microorganisms.« less

  17. Humic acid effect on catalase activity and the generation of reactive oxygen species in corn (Zea mays).

    PubMed

    Cordeiro, Flávio Couto; Santa-Catarina, Claudete; Silveira, Vanildo; de Souza, Sonia Regina

    2011-01-01

    Humic acids (HAs) have positive effects on plant physiology, but the molecular mechanisms underlying these events are only partially understood. The induction of root growth and emission of lateral roots (LRs) promoted by exogenous auxin is a natural phenomenon. Exogenous auxins are also associated with HA. Gas nitric oxide (NO) is a secondary messenger produced endogenously in plants. It is associated with metabolic events dependent on auxin. With the application of auxin, NO production is significantly increased, resulting in positive effects on plant physiology. Thus it is possible to evaluate the beneficial effects of the application of HA as an effect of auxin. To investigate the effects of HA the parameters of root growth, Zea mays was studied by evaluating the application of 3 mM C L⁻¹ of HA extracted from Oxisol and 100 µM SNP (sodium nitroprusside) and the NO donor, subject to two N-NO₃⁻, high dose (5.0 mM N-NO₃⁻) and low dose (5.0 mM N-NO₃⁻). Treatments with HA and NO were positively increased, regardless of the N-NO₃⁻ taken, as assessed by fresh weight and dry root, issue of LRs. The effects were more pronounced in the treatment with a lower dose of N-NO₃⁻. Detection of reactive oxygen species (ROS) in vivo and catalase activity were evaluated; these tests were associated with root growth. Under application of the bioactive substances tested, detection of ROS and catalase activity increased, especially in treatments with lower doses of N-NO₃⁻. The results of this experiment indicate that the effects of HA are dependent on ROS generation, which act as a messenger that induces root growth and the emission of LRs.

  18. Effects of humic acid and heavy metals on the sorption of polar and apolar organic pollutants onto biochars.

    PubMed

    Wang, Fei; Sun, Hongwen; Ren, Xinhao; Liu, Yarui; Zhu, Hongkai; Zhang, Peng; Ren, Chao

    2017-12-01

    The effects of humic acid (HA) and heavy metals (Cu 2+ and Ag + ) on the sorption of polar and apolar organic pollutants onto biochars that were produced at temperatures of 200 °C (BC200) and 700 °C (BC700) were studied. Due to the plentiful polar functional groups on BC200, cationic propranolol exhibited higher levels of sorption than naphthalene on BC200 while naphthalene and propranolol showed similar sorption capacities on BC700. HA changed the characteristics of biochars and generally inhibited the sorption of target organic pollutants on biochars; however, enhancement occurred in some cases depending on the pollutants involved and their concentrations, biochars used and the addition sequences and concentrations of HA. On BC200, HA modifications mainly influenced sorption by decreasing its polarity and increasing its aromaticity, while on BC700, the surface area and pore volume greatly decreased due to the pore-blocking effects of HA. Residue dissolved HA in solution may also contribute to sorption inhibition. Complexation between polar functional groups on BC200 and heavy metals slightly enhanced the sorption of neutral naphthalene and significantly enhanced that of anionic 4-nitro-1-naphtol, while limited the sorption of cationic propranolol. Heavy metals together with their associated water molecules decreased the sorption of target chemicals on BC700 via pore-filling or pore-mouth-covering. Inhibition of heavy metals for 4-nitro-1-naphthol was found to be the weakest due to the bridge effects of heavy metals between 4-nitro-1-naphtol and BC700. The higher polarizability of Ag + led to the increase of its sorption on biochars in the presence of organic aromatic pollutants. The results of the present study shed light on the sorption mechanisms of bi-solute systems and enable us to select suitable biochar sorbents when chemicals co-exist. Copyright © 2017. Published by Elsevier Ltd.

  19. Removal of humic acid using TiO2 photocatalytic process--fractionation and molecular weight characterisation studies.

    PubMed

    Liu, Sanly; Lim, May; Fabris, Rolando; Chow, Christopher; Chiang, Ken; Drikas, Mary; Amal, Rose

    2008-05-01

    The photocatalytic removal of humic acid (HA) using TiO2 under UVA irradiation was examined by monitoring changes in the UV(254) absorbance, dissolved organic carbon (DOC) concentration, apparent molecular weight distribution, and trihalomethane formation potentials (THMFPs) over treatment time. A resin fractionation technique in which the samples were fractionated into four components: very hydrophobic acids (VHA), slightly hydrophobic acids, hydrophilic charged (CHA) and hydrophilic neutral (NEU) was also employed to elucidate the changes in the chemical nature of the HA components during treatment. The UVA/TiO2 process was found to be effective in removing more than 80% DOC and 90% UV(254) absorbance. The THMFPs of samples were decreased to below 20 microg l(-1) after treatments, which demonstrate the potential to meet increasingly stringent regulatory level of trihalomethanes in water. Resin fractionation analysis showed that the VHA fraction was decreased considerably as a result of photocatalytic treatments, forming CHA intermediates which were further degraded with increased irradiation time. The NEU fraction, which comprised of non-UV-absorbing low molecular weight compounds, was found to be the most persistent component.

  20. Competition effects in cation binding to humic acid: Conditional affinity spectra for fixed total metal concentration conditions

    NASA Astrophysics Data System (ADS)

    David, Calin; Mongin, Sandrine; Rey-Castro, Carlos; Galceran, Josep; Companys, Encarnació; Garcés, José Luis; Salvador, José; Puy, Jaume; Cecilia, Joan; Lodeiro, Pablo; Mas, Francesc

    2010-09-01

    Information on the Pb and Cd binding to a purified Aldrich humic acid (HA) is obtained from the influence of different fixed total metal concentrations on the acid-base titrations of this ligand. NICA (Non-Ideal Competitive Adsorption) isotherm has been used for a global quantitative description of the binding, which has then been interpreted by plotting the Conditional Affinity Spectra of the H + binding at fixed total metal concentrations (CAScTM). This new physicochemical tool, here introduced, allows the interpretation of binding results in terms of distributions of proton binding energies. A large increase in the acidity of the phenolic sites as the total metal concentration increases, especially in presence of Pb, is revealed from the shift of the CAScTM towards lower affinities. The variance of the CAScTM distribution, which can be used as a direct measure of the heterogeneity, also shows a significant dependence on the total metal concentration. A discussion of the factors that influence the heterogeneity of the HA under the conditions of each experiment is provided, so that the smoothed pattern exhibited by the titration curves can be justified.

  1. Quenching of fluorescence of phenolic compounds and modified humic acids by cadmium ions.

    PubMed

    Tchaikovskaya, O N; Nechaev, L V; Yudina, N V; Mal'tseva, E V

    2016-08-01

    The interaction of a number of phenolic compounds, being 'model fragments' of humic acids, with cadmium ions was investigated. The fluorescence quenching method was used to determine the complexation constants of these compounds with cadmium ions. It was established that bonding of phenolic compounds by cadmium ions at рН 7 is weak and reaches a maximum value of 15% for interaction with resorcinol. It was demonstrated that modification of humic acids by the mechanoactivation method increases by three times bonding of cadmium ions, which is caused by strengthening the acid properties of carboxyl and hydroxyl groups at the aromatic ring. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  2. Water solubility enhancement of some organic pollutants and pesticides by dissolved humic and fulvic acids

    USGS Publications Warehouse

    Chiou, C.T.; Malcolm, R.L.; Brinton, T.I.; Kile, D.E.

    1986-01-01

    Water solubility enhancements by dissolved humic and fulvic acids from soil and aquatic origins and by synthetic organic polymers have been determined for selected organic pollutants and pesticides (p,p???-DDT, 2,4,5,2???,5???-PCB, 2,4,4???-PCB, 1,2,3-trichlorobenzene, and lindane). Significant solubility enhancements of relatively water-insoluble solutes by dissolved organic matter (DOM) of soil and aquatic origins may be described in terms of a partition-like interaction of the the solutes with the microscopic organic environment of the high-molecular-weight DOM species; the apparent solute solubilities increase linearly with DOM concentration and show no competitive effect between solutes. With a given DOM sample, the solute partition coefficient (Kdom) increases with a decrease of solute solubility (Sw) or with an increase of the solute's octanol-water partition coefficient (Kow). The Kdom values of solutes with soil-derived humic acid are approximately 4 times greater than with soil fulvic acid and 5-7 times greater than with aquatic humic and fulvic acids. The effectiveness of DOM in enhancing solute solubility appears to be largely controlled by the DOM molecular size and polarity. The relative inability of high-molecular-weight poly(acrylic acids) to enhance solute solubility is attributed to their high polarities and extended chain structures that do not permit the formation of a sizable intramolecular nonpolar environment.

  3. Biouptake, toxicity and biotransformation of triclosan in diatom Cymbella sp. and the influence of humic acid.

    PubMed

    Ding, Tengda; Lin, Kunde; Bao, Lianjun; Yang, Mengting; Li, Juying; Yang, Bo; Gan, Jay

    2018-03-01

    Triclosan is one of the most frequently detected emerging contaminants in aquatic environment. In this study, we investigated the biouptake, toxicity and biotransformation of triclosan in freshwater algae Cymbella sp. The influence of humic acid, as a representative of dissolved organic matter, was also explored. Results from this study showed that triclosan was toxic to Cymbella sp. with 72 h EC 50 of 324.9 μg L -1 . Humic acid significantly reduced the toxicity and accumulation of triclosan in Cymbella sp. SEM analysis showed that Cymbella sp. were enormously damaged under 1 mg L -1 triclosan exposure and repaired after the addition of 20 mg L -1 humic acid. Triclosan can be significantly taken up by Cymbella sp. The toxicity of triclosan is related to bioaccumulated triclosan as the algal cell numbers decreased when intracellular triclosan increased. A total of 11 metabolites were identified in diatom cells and degradation pathways are proposed. Hydroxylation, methylation, dechlorination, amino acids conjunction and glucuronidation contributed to the transformative reactions of triclosan in Cymbella sp., producing biologically active products (e.g., methyl triclosan) and conjugation products (e.g., glucuronide or oxaloacetic acid conjugated triclosan), which may be included in the detoxification mechanism of triclosan. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Sorption of Eu(III) on humic acid or fulvic acid bound to hydrous alumina studied by SEM-EDS, XPS, TRLFS, and batch techniques.

    PubMed

    Tan, X L; Wang, X K; Geckeis, H; Rabung, Th

    2008-09-01

    To identify the effect of humic acid (HA) and fulvic acid (FA) on the sorption mechanism of Eu(III) on organic--inorganic colloids in the environment at a molecular level, surface adsorbed/ complexed Eu(III) on hydrous alumina, HA-, and FA-hydrous alumina hybrids were characterized by using X-ray photoelectron spectroscopy (XPS) and time-resolved laser fluorescence spectroscopy (TRLFS). The experiments were performed in 0.1 mol/L KNO3 or 0.1 mol/L NaClO4 under ambient conditions. The pH values were varied between 2 and 11 at a fixed Eu(III) concentration of 6.0 x 10(-7) mol/L and 4.3 x 10(-5) mol/L. The different Eu(III)/FA(HA)/hydrous alumina complexes were characterized by their fluorescence emission spectra ((5D0-F1)/ (5D0 --> 7F2)) and binding energy of Eu(III). Inner-sphere surface complexation may contribute mainly to Eu(III) sorption on hydrous alumina, and a ternary surface complex is formed at the HA/ FA-hydrous alumina hybrid surfaces. The sorption and species of Eu(III) in ternary Eu-HA/FA-hydrous alumina systems are not dominated by either HA/FA or hydrous alumina, but are dominated by both HA/FA and hydrous alumina. The results are important for understanding the sorption mechanisms and the nature of surface adsorbed Eu(III) species and trivalent chemical homologues of Eu(III) in the natural environment.

  5. Co-remediation of the lead-polluted garden soil by exogenous natural zeolite and humic acids.

    PubMed

    Shi, Wei-yu; Shao, Hong-bo; Li, Hua; Shao, Ming-an; Du, Sheng

    2009-08-15

    The current study reported the co-remediation effect on the lead-polluted garden soil by zeolite and humic acids (HA), which was from comparing with the remediation of single zeolite in term of the lead fraction of sequential extraction in the soil and the distribution of lead in different parts of rape. Mixed treatment (zeolite and HA) and single treatment (zeolite) were, respectively, applied to the artificially polluted garden soil to examine the difference of their remediation effects in pot experiment. Results indicated that the co-remediation led to significantly greater (p<0.01) reduction in the lead concentration in plants than by singly adding to zeolite. The co-application of zeolite and HA reduced the available fraction of lead compounds, but slightly increased (p<0.01) the water-soluble fraction of lead compounds in the garden soil, compared with the application of single zeolite, especially in the severe lead-polluted soil (> or =1000 mg kg(-1)). This method might be an efficient way to remediate the lead-polluted soils on a large scale, although zeolite is a kind of hazardous material.

  6. Key role of pH in the photochemical conversion of NO2 to HONO on humic acid

    NASA Astrophysics Data System (ADS)

    Han, Chong; Yang, Wangjin; Wu, Qianqian; Yang, He; Xue, Xiangxin

    2016-10-01

    The heterogeneous photochemical reactions of NO2 with humic acid (HA) were performed using a flow tube reactor coupled to a NOx analyzer. The effects of the pH on the uptake coefficient (γ) of NO2 and HONO and NO yields were investigated in detail. With increasing the pH in the range of 2-12, γ was almost constant with an average value of (4.21 ± 0.46) × 10-6, whereas the HONO yield and NO yield linearly decreased from (81.07 ± 4.07)% and (10.35 ± 3.86)% to (13.87 ± 9.15)% and (1.51 ± 0.94)%, respectively. According to the characterization of HA compositions and possible reaction paths, it can be concluded that the pH may influence the transfer of protons and the equilibrium of HONO with NO2- by varying the contents of carboxyl and phenol groups in HA, which should primarily contribute to the change in the HONO yield with the pH.

  7. Influence of surfactants and humic acids on Artemia Franciscana's embryonic phospho-metabolite profile as measured by 31P NMR.

    PubMed

    Deese, Rachel D; Weldeghiorghis, Thomas K; Haywood, Benjamin J; Cook, Robert L

    2017-05-01

    Surfactants, such as triton X-100 (Tx-100), cetylpyridinium chloride (CPC), and sodium dodecyl sulfate (SDS) are known to be toxic to Artemia Franciscana (Artemia) - an organism, frequently used to monitor the health of the aquatic environment. The phospho-metabolite profile of a living organism is often indicative of imbalances that may have been caused by environmental stressors, such as surfactants. This study utilizes in vivo 31 P NMR to monitor temporal changes in the phospho-metabolite profile of Artemia caused by Tx-100, CPC, and SDS and the ability of humic acid (HA) to mitigate the toxicity of these surfactants. It was found that, while Tx-100 does not have any effect on the phospho-metabolite profile, both CPC and SDS cause a complete retardation in growth of the phosphodiester (PDE) peak in the 31 P NMR spectrum, which is indicative of the inhibited cell replication. This growth inhibition was independently verified by the decreased guanosine triphosphate (GTP) concentration in the CPC and SDS-exposed Artemia. In addition, upon introduction of HA to the CPC and SDS-exposed Artemia, an increase of PDE peak over time is indicative of HA mitigating toxicity. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. The chemical structure of highly aromatic humic acids in three volcanic ash soils as determined by dipolar dephasing NMR studies

    USGS Publications Warehouse

    Hatcher, P.G.; Schnitzer, M.; Vassallo, A.M.; Wilson, M.A.

    1989-01-01

    Dipolar dephasing 13C NMR studies of three highly aromatic humic acids, one from a modern soil and two from paleosols, have permitted the determination of the degree of aromatic substitution. From these data and the normal solid-state 13C NMR data we have been able to develop a model for the average chemical structure of these humic acids that generally correlates well with permanganate oxidation data. The models depict these humic acids as benzene di- and tricarboxylic acids interconnected by biphenyl linkages. An increasing degree of substitution is observed with increasing geologic age. These structures may be characteristic of the resistant aromatic part of the "core" of humic substances that survives degradation. ?? 1989.

  9. 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.

  10. Photochemical Study of Silver Nanoparticles Formed from the Reduction of Silver Ions by Humic Acid

    NASA Astrophysics Data System (ADS)

    Leslie, Renee M.

    This study focuses on the ability of silver ions and humic acid to form silver nanoparticles in the presence of UV and visible light. Silver nanoparticles have a number of industrial applications due primarily to their antimicrobial properties, but these properties pose an environmental threat. Silver nanoparticles can directly disrupt sensitive ecosystems by harming bacteria. Consumption of silver nanoparticles results in silver ions and silver nanoparticles entering waterways; the presence of silver ions raises the question of whether nanoparticles can reform in environmental waters. As our data show, silver nanoparticles can form from the reduction of silver ions by humic acid after irradiation with UV and visible light. In order to better understand the mechanism of these naturally synthesized silver nanoparticles, we investigated the effects of reactant concentration, experimental conditions and presence of ions/reactive species. We monitored silver nanoparticle growth with UV-visible spectroscopy. The evolution in time of nanoparticle size was monitored by dynamic light scattering (DLS).

  11. Investigation of pyrolysis kinetics of humic acids from low rank Anatolian coal by thermal analysis

    SciTech Connect

    Tonbul, Y.; Erdogan, S.

    2007-07-01

    Thermogravimetric analysis (TGA) of humic acid samples from low rank Anatolian (east of Turkey, Bingol) coal were investigated under atmospheric pressure. The samples were subjected for the decomposition of organic matter ambient to 800{sup o} C at four different heating rates (5, 10, 15, and 20 degrees C min{sup -1}). The humic acid samples were started at decomposition between 170 - 206{sup o}C and amount of residues varied 55-60% according to heating rate. Each of samples showed a single step mass loss. TG/DTG data of samples were analyzed to determine activation energy values by Coats and Redfern method and Arrheniusmore » method. Activation energy values are similar obtained from Coats and Redfern method and Arrhenius method and varied from 25 to 29 kJ mol{sup -1}.« less

  12. Anoxic and oxic removal of humic acids with Fe@Fe2O3 core-shell nanowires: a comparative study.

    PubMed

    Wu, Hao; Ai, Zhihui; Zhang, Lizhi

    2014-04-01

    In this study we comparatively investigate the removal of humic acids with Fe@Fe2O3 core-shell nanowires under anoxic and oxic conditions. The products of humic acids after reacting with Fe@Fe2O3 core-shell nanowires under anoxic and oxic conditions were carefully examined with three-dimensional excitation emission matrix fluorescence spectroscopy and gas chromatography mass spectrometry. It was found that humic acids were removed by Fe@Fe2O3 core-shell nanowires via adsorption under anoxic condition. Langmuir adsorption isotherm was applicable to describe the adsorption processes. Kinetics of humic acids adsorption onto Fe@Fe2O3 core-shell nanowires was found to follow pseudo-second-order rate equation. By contrast, the oxic removal of humic acids with Fe@Fe2O3 core-shell nanowires involved adsorption and subsequent oxidation of humic acids because Fe@Fe2O3 core-shell nanowires could activate molecular oxygen to produce reactive oxygen species to oxidize humic acids. This subsequent oxidation of humic acids could improve the oxic removal rate to 2.5 times that of anoxic removal, accompanying with about 8.4% of mineralization. This study provides a new method for humic acids removal and also sheds light on the effects of humic acids on the pollutant removal by nano zero-valent iron. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Efficient biodegradation of acephate by Pseudomonas pseudoalcaligenes PS-5 in the presence and absence of heavy metal ions [Cu(II) and Fe(III)], and humic acid.

    PubMed

    Singh, Simranjeet; Kumar, Vijay; Upadhyay, Niraj; Singh, Joginder; Singla, Sourav; Datta, Shivika

    2017-08-01

    The present study was intended to investigate the biodegradation of acephate in aqueous media in the presence and in the absence of metal ions [Fe(III) and Cu(II)], and humic acid (HA). Biodegradations were performed using Pseudomonas pseudoalcaligenes PS-5 (PS-5) isolated from the heavy metal polluted site. Biodegradations were monitored by UV-Visible, FTIR, and electron spray ionization-mass spectrometry (ESI-MS) analyses. ESI-MS analysis revealed that PS-5 degraded acephate to two metabolites showing intense ions at mass-to-charge ratios ( m / z ) 62 and 97. The observed kinetic was the pseudo-first order, and half-life periods ( t 1/2 ) were 2.79 d -1 (of PS-5 + acephate), 3.45 d -1 [of PS-5 + acephate + Fe(III)], 3.16 d -1 [of PS-5 + acephate + Cu(II)], and 5.54 d -1 (of PS-5 + acephate + HA). A significant decrease in degradation rate of acephate was noticed in the presence of HA, and the same was confirmed by UV-Visible and TGA analyses. Strong aggregation behavior of acephate with humic acid in aqueous media was the major cause behind the slow degradation rate of acephate . New results on acephate metabolism by strain PS-5 in the presence and in the absence of metal ions [Fe(III) and Cu(II)] and humic acid were obtained. Results confirmed that Pseudomonas pseudoalcaligenes strain PS-5 was capable of mineralization of the acephate without formation of toxic metabolite methamidophos. More significantly, the Pseudomonas pseudoalcaligenes strain PS-5 could be useful as potential biological agents in effective bioremediation campaign for multi-polluted environments.

  14. Phosphate Changes Effect of Humic Acids on TiO2 Photocatalysis: From Inhibition to Mitigation of Electron-Hole Recombination.

    PubMed

    Long, Mingce; Brame, Jonathon; Qin, Fan; Bao, Jiming; Li, Qilin; Alvarez, Pedro J J

    2017-01-03

    A major challenge for photocatalytic water purification with TiO 2 is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron-hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated. This ratio was very high, up to 5.72 at 30 mg/L HA and pH 4.8 without phosphate, but was decreased to 0.76 (5 mg/L HA, pH 8.4) with 2 mM phosphate. The latter ratio indicates a surprising favorable effect of HA on TiO 2 photocatalysis. FTIR analyses suggest that this favorable effect is likely due to a change in the conformation of adsorbed HA, from a multiligand exchange arrangement to a complexation predominantly between COOH groups in HA and the TiO 2 surface in the presence of phosphate. This configuration can reduce hole consumption and facilitate electron transfer to O 2 by the adsorbed HA (indicated by linear sweep voltammetry), which mitigates electron-hole recombination and enhances contaminant degradation. A decrease in HA surface adsorption and hole scavenging (the predominant inhibitory mechanisms of HA) by phosphate (2 mM) was indicated by a 50% decrease in the photocatalytic degradation rate of HA and 80% decrease in the decay rate coefficient of interfacial-related photooxidation in photocurrent transients. These results, which were validated with other compounds (FFA and cimetidine), indicate that anchoring phosphate - or anions that exert similar effects on the TiO 2 surface - might be a feasible strategy to counteract the inhibitory effect of NOM during photocatalytic water treatment.

  15. Antagonistic effects of humic acid and iron oxyhydroxide grain-coating on biochar nanoparticle transport in saturated sand.

    PubMed

    Wang, Dengjun; Zhang, Wei; Zhou, Dongmei

    2013-05-21

    Biochar land application may result in multiple agronomic and environmental benefits (e.g., carbon sequestration, improving soil quality, and immobilizing environmental contaminants). However, our understanding of biochar particle transport is largely unknown in natural environments with significant heterogeneity in solid (e.g., patches of iron oxyhydroxide coating) and solution chemistry (e.g., the presence of natural organic matter), which represents a critical knowledge gap in assessing the environmental impact of biochar land application. Transport and retention kinetics of nanoparticles (NPs) from wheat straw biochars produced at two pyrolysis temperatures (i.e., 350 and 550 °C) were investigated in water-saturated sand columns at environmentally relevant concentrations of dissolved humic acid (HA, 0, 1, 5, and 10 mg L(-1)) and fractional surface coverage of iron oxyhydroxide coatings on sand grains (ω, 0.16, 0.28, and 0.40). Transport of biochar NPs increased with increasing HA concentration, largely because of enhanced repulsive interaction energy between biochar NPs and sand grains. Conversely, transport of biochar NPs decreased significantly with increasing ω due to enhanced electrostatic attraction between negatively charged biochar NPs and positively charged iron oxyhydroxides. At a given ω of 0.28, biochar NPs were less retained with increasing HA concentration due to increased electrosteric repulsion between biochar NPs and sand grains. Experimental breakthrough curves and retention profiles were well described using a two-site kinetic retention model that accounted for Langmuirian blocking or random sequential adsorption at one site. Consistent with the blocking effect, the often observed flat retention profiles stemmed from decreased retention rate and/or maximum retention capacity at a higher HA concentration or smaller ω. The antagonistic effects of HA and iron oxyhydroxide grain-coating imparted on the mobility of biochar NPs suggest that

  16. Photodegradation of lambda-cyhalothrin and cypermethrin in aqueous solution as affected by humic acid and/or copper: intermediates and degradation pathways.

    PubMed

    Xie, Jimin; Wang, Pingli; Liu, Jun; Lv, Xiaomeng; Jiang, Deli; Sun, Cheng

    2011-11-01

    The influence of coexisting humic acids (HA) or Cu²⁺ on the photodegradation of pesticides lambda-cyhalothrin (λ-CHT) and cypermethrin (CPM) in aqueous solution was studied under xenon lamp irradiation. The removal efficiency of pesticides λ-CHT and CPM were enhanced in the presence of either Cu²⁺ or HA but restrained in the presence of both Cu²⁺ and HA. The photodegradation of λ-CHT and CPM followed first-order reaction kinetics. The photodegradation intermediates of λ-CHT and CPM were determined using gas chromatography/mass spectrometry. Possible photodegradation pathways included decarboxylation, ester bond cleavage, dechlorination, and phenyl group removal. Copyright © 2011 SETAC.

  17. Determination of total antioxidant capacity of humic acids using CUPRAC, Folin-Ciocalteu, noble metal nanoparticle- and solid-liquid extraction-based methods.

    PubMed

    Karadirek, Şeyda; Kanmaz, Nergis; Balta, Zeynep; Demirçivi, Pelin; Üzer, Ayşem; Hızal, Jülide; Apak, Reşat

    2016-06-01

    Total antioxidant capacity (TAC) of humic acid (HA) samples was determined using CUPRAC (CUPric Reducing Antioxidant Capacity), FC (Folin-Ciocalteu), QUENCHER-CUPRAC, QUENCHER-FC, Ag-NP (Silver nanoparticle)‒ and Au-NP (Gold nanoparticle)‒based methods. Conventional FC and modified FC (MFC) methods were applied to solid samples. Because of decreased solubility of Folin-Ciocalteu's phenol reagent in organic solvents, solvent effect on TAC measurement was investigated using QUENCHER-CUPRAC assay by using ethanol:distilled water and dimethyl sulfoxide:distilled water with varying ratios. To see the combined effect of solubilization (leaching) and TAC measurement of humic acids simultaneously, QUENCHER experiments were performed at 25°C and 50°C; QUENCHER-CUPRAC and QUENCHER-FC methods agreed well and had similar precision in F-statistics. Although the Gibbs free energy change (ΔG°) of the oxidation of HA dihydroxy phenols with the test reagents were negative, the ΔG° was positive only for the reaction of CUPRAC reagent with isolated monohydric phenols, showing CUPRAC selectivity toward polyphenolic antioxidants. This is the first work on the antioxidant capacity measurement of HA having a sparingly soluble matrix where enhanced solubilization of bound phenolics is achieved with coupled oxidation by TAC reagents. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Colloidal behavior of goethite nanoparticles modified with humic acid and implications for aquifer reclamation

    NASA Astrophysics Data System (ADS)

    Tiraferri, Alberto; Saldarriaga Hernandez, Laura Andrea; Bianco, Carlo; Tosco, Tiziana; Sethi, Rajandrea

    2017-03-01

    Nanosized colloids of iron oxide adsorb heavy metals, enhance the biodegradation of contaminants, and represent a promising technology to clean up contaminated aquifers. Goethite particles for aquifer reclamation were recently synthesized with a coating of humic acids to reduce aggregation. This study investigates the stability and the mobility in porous media of this material as a function of aqueous chemistry, and it identifies the best practices to maximize the efficacy of the related remediation. Humic acid-coated nanogoethite (hydrodynamic diameter ˜90 nm) displays high stability in solutions of NaCl, consistent with effective electrosteric stabilization. However, particle aggregation is fast when calcium is present and, to a lesser extent, also in the presence of magnesium. This result is rationalized with complexation phenomena related to the interaction of divalent cations with humic acid, inducing rapid flocculation and sedimentation of the suspensions. The calcium dose, i.e., the amount of calcium ions with respect to solids in the dispersion, is the parameter governing stability. Therefore, more concentrated slurries may be more stable and mobile in the subsurface than dispersions of low particle concentration. Particle concentration during field injection should be thus chosen based on concentration and proportion of divalent cations in groundwater.

  19. Humic acids-based hierarchical porous carbons as high-rate performance electrodes for symmetric supercapacitors.

    PubMed

    Qiao, Zhi-jun; Chen, Ming-ming; Wang, Cheng-yang; Yuan, Yun-cai

    2014-07-01

    Two kinds of hierarchical porous carbons (HPCs) with specific surface areas of 2000 m(2)g(-1) were synthesized using leonardite humic acids (LHA) or biotechnology humic acids (BHA) precursors via a KOH activation process. Humic acids have a high content of oxygen-containing groups which enabled them to dissolve in aqueous KOH and facilitated the homogeneous KOH activation. The LHA-based HPC is made up of abundant micro-, meso-, and macropores and in 6M KOH it has a specific capacitance of 178 F g(-1) at 100 Ag(-1) and its capacitance retention on going from 0.05 to 100 A g(-1) is 64%. In contrast, the BHA-based HPC exhibits a lower capacitance retention of 54% and a specific capacitance of 157 F g(-1) at 100 A g(-1) which is due to the excessive micropores in the BHA-HPC. Moreover, LHA-HPC is produced in a higher yield than BHA-HPC (51 vs. 17 wt%). Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids.

    PubMed

    Olaetxea, Maite; Mora, Verónica; Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Zamarreño, Angel M; Iriarte, Juan C; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón; Baigorri, Roberto; García-Mina, Jose M

    2015-12-01

    The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. © 2015 American Society of Plant Biologists. All Rights Reserved.

  1. Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids1

    PubMed Central

    Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón

    2015-01-01

    The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. PMID:26450705

  2. Sorption of Th (IV) to silica as a function of pH, humic/fulvic acid, ionic strength, electrolyte type.

    PubMed

    Chen, Changlun; Wang, Xiangke

    2007-02-01

    The removal behavior of thorium (Th(IV)) has been investigated in multicomponent systems containing silica (SiO2) as the model of inorganic particles because of its widespread presence in the earth's crust and soil humic acid (HA)/fulvic acid (FA) by batch experiments. The influence of pH from 2 to 12, ionic strength from 0.02 to 0.2 M KNO3, soil HA/FA concentration from 8.3 to 22.5 mg/L, and foreign cations (Li+, Na+, K+) and anions (NO3(-), Cl-) on the sorption of Th(IV) onto SiO2 was also tested. The sorption isotherms of Th(IV) at approximately constant pH (3.50+/-0.02) were determined and analyzed regressively with three kinds of sorption isotherm models, i.e., linear, Langmuir, and Freundlich models. The results demonstrated that the sorption of Th(IV) onto SiO2 increased steeply with increasing pH from 2 to 4. Generally, humic substances (HSs) were shown to enhance Th(IV) sorption at low pH, but to reduce Th(IV) sorption at intermediate and high pH. It was a hypothesis that the significantly positive influence of HA/FA at pH from 2 to 4 on the sorption of Th(IV) onto SiO2 was attributed to strong surface binding of HA/FA on SiO2 and subsequently the formation of ternary surface complexes such as [triple bond]MO-O-HA-Th or [triple bond]MO-O-FA-Th. The results also demonstrated that the sorption was strongly dependent on the concentration of HA/FA, and independent of ionic strength and foreign ions under our experimental conditions.

  3. Insight into the heterogeneous adsorption of humic acid fluorescent components on multi-walled carbon nanotubes by excitation-emission matrix and parallel factor analysis.

    PubMed

    Yang, Chenghu; Liu, Yangzhi; Cen, Qiulin; Zhu, Yaxian; Zhang, Yong

    2018-02-01

    The heterogeneous adsorption behavior of commercial humic acid (HA) on pristine and functionalized multi-walled carbon nanotubes (MWCNTs) was investigated by fluorescence excitation-emission matrix and parallel factor (EEM- PARAFAC) analysis. The kinetics, isotherms, thermodynamics and mechanisms of adsorption of HA fluorescent components onto MWCNTs were the focus of the present study. Three humic-like fluorescent components were distinguished, including one carboxylic-like fluorophore C1 (λ ex /λ em = (250, 310) nm/428nm), and two phenolic-like fluorophores, C2 (λ ex /λ em = (300, 460) nm/552nm) and C3 (λ ex /λ em = (270, 375) nm/520nm). The Lagergren pseudo-second-order model can be used to describe the adsorption kinetics of the HA fluorescent components. In addition, both the Freundlich and Langmuir models can be suitably employed to describe the adsorption of the HA fluorescent components onto MWCNTs with significantly high correlation coefficients (R 2 > 0.94, P< 0.05). The dissimilarity in the adsorption affinity (K d ) and nonlinear adsorption degree from the HA fluorescent components to MWCNTs was clearly observed. The adsorption mechanism suggested that the π-π electron donor-acceptor (EDA) interaction played an important role in the interaction between HA fluorescent components and the three MWCNTs. Furthermore, the values of the thermodynamic parameters, including the Gibbs free energy change (ΔG°), enthalpy change (ΔH°) and entropy change (ΔS°), showed that the adsorption of the HA fluorescent components on MWCNTs was spontaneous and exothermic. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Humic and fulvic acids: sink or source in the availability of metals to the marine bivalves Macoma balthica and Potamocorbula amurensis?

    USGS Publications Warehouse

    Decho, Alan W.; Luoma, Samuel N.

    1994-01-01

    Humic acids (HA) and fulvic acids (FA) are common forms of organic matter in marine sediments, and are routinely ingested by deposit- and suspension-feeding animals. These compounds may be a sink for metals, implying that once metals are bound to humic substances they are no longer available to food webs. A series of experiments was conducted to quantitatively examine this premise using 2 estuarine bivalves from San Francisco Bay, USA: the suspension feeder Potarnocorbula arnurensis and the facultative deposit feeder Macoma balthica. HA and FA, isolated from marine sediments, were bound as organic coatings to either hydrous ferric oxides (HFO) or silica particles. Cd and Cr(II1) were adsorbed to the organic coatings or directly to uncoated HFO and silica particles. Pulse-chase laboratory feeding expenments using 109Cd and 51Cr(III) were then conducted to determine absorption efficiencies of Cd and Cr for individual specimens using each of the particle types. The results demonstrated that: (1) absorption of Cr(I1I) from all types of non-living particles was consistently low (< 11%). Ingested Cd showed greater bioavailability than Cr(IIl), perhaps due to differences in metal chemistry. (2) Bivalves absorbed Cd bound to uncoated HFO or silica particles (i.e. with no HA or FA present). (3) The presence of organic coatings on particles reduced Cd bioavailabhty compared with uncoated particles. (4) Both geochemical and biological conditions affected the food chain transfer of Cd. The data suggest that in marine systems inorganic and organic-coated particles are predominantly a sink for Cr in sediments. In the transfer of Cd to consumer animals, inorganic particles and humic substances can act as a link (although not a highly efficient one) under oxidized conditions.

  5. The transformation of triclosan by laccase: Effect of humic acid on the reaction kinetics, products and pathway.

    PubMed

    Dou, Rong-Ni; Wang, Jing-Hao; Chen, Yuan-Cai; Hu, Yong-You

    2018-03-01

    This study systematically explored the effect of humic acid (HA) (as model of natural organic matter) on the kinetics, products and transformation pathway of triclosan (TCS) by laccase-catalyzed oxidation. It was found that TCS could be effectively transformed by laccase-catalysis, with the apparent second-order rate constant being 0.056 U -1 mL min -1 . HA inhibited the removal rate of TCS. HA-induced inhibition was negatively correlated with HA concentration in the range of 0-10 mg L -1 and pH-dependent from 3.5 to 9.5. FT-IR and 13 C NMR spectra showed a decrease of aromatic hydroxyl (phenolic) groups and an increase of aromatic ether groups, indicating the cross-linking of HA via C-O-C and C-N-C bonds during enzyme-catalyzed oxidation. Ten principle oxidative products, including two quinone-like products (2-chlorohydroquinone, 2-chloro-5-(2,4-dichlodichlorophenoxy)-(1,4)benzoquinone), one chlorinated phenol (2,4-dichlorophenol (2,4-DCP)), three dimers, two trimmers and two tetramers, were detected by gas chromatograghy/mass spectrometry (GC-MS) and high performance liquid chromatography/quadrupole time-of-flight/mass spectrometry (HPLC/Q-TOF/MS). The presence of HA induced significantly lesser generation of self-polymers and enhanced cross-coupling between HA and self-polymers via C-O-C, C-N-C and C-C coupling pathways. A plausible transformation pathway was proposed as follows: TCS was initially oxidized to form reactive phenoxyl radicals, which self-coupled to each other subsequently by C-C and C-O pathway, yielding self-polymers. In addition, the scission of ether bond was also observed. The presence of HA can promote scission of ether bond and further oxidation of phenoxyl radicals, forming hydroxylated or quinone-like TCS. This study shed light on the behavior of TCS in natural environment and engineered processes, as well provided a perspective for the water/wastewater treatment using enzyme-catalyzed oxidation techniques. Copyright © 2017 Elsevier Ltd

  6. Charge characteristics of humic and fulvic acids: comparative analysis by colloid titration and potentiometric titration with continuous pK-distribution function model.

    PubMed

    Bratskaya, S; Golikov, A; Lutsenko, T; Nesterova, O; Dudarchik, V

    2008-09-01

    Charge characteristics of humic and fulvic acids of a different origin (inshore soils, peat, marine sediments, and soil (lysimetric) waters) were evaluated by means of two alternative methods - colloid titration and potentiometric titration. In order to elucidate possible limitations of the colloid titration as an express method of analysis of low content of humic substances we monitored changes in acid-base properties and charge densities of humic substances with soil depth, fractionation, and origin. We have shown that both factors - strength of acidic groups and molecular weight distribution in humic and fulvic acids - can affect the reliability of colloid titration. Due to deviations from 1:1 stoichiometry in interactions of humic substances with polymeric cationic titrant, the colloid titration can underestimate total acidity (charge density) of humic substances with domination of weak acidic functional groups (pK>6) and high content of the fractions with molecular weight below 1kDa.

  7. Effect of soil humic and fulvic acids, pH and ionic strength on Th(IV) sorption to TiO2 nanoparticles.

    PubMed

    Tan, Xiaoli; Wang, Xiangke; Chen, Changlun; Sun, Aihua

    2007-04-01

    Thorium is considered as a chemical analog of other tetravalent actinides. Herein, the sorption of Th(IV) on TiO(2) in the presence or absence of soil fulvic acid (FA)/humic acid (HA) as a function of pH, ionic strength and FA/HA concentration has been studied by a batch method. The morphology was characterized by scanning electron microscopy (SEM). The results indicate that sorption of Th(IV) on TiO(2) increases from 0% to approximately 94% at pH 1 approximately 4, and then maintains level with increasing pH values. Both FA and HA have a positive effect on Th(IV) sorption at low pH values and the contribution of FA on Th(IV) sorption is rather higher than that of HA at pH<4. The sorption is weakly dependent on the concentration of KNO(3) in solution, but the cations K(+), Na(+) and Li(+) influence Th(IV) sorption more obviously. The batch results indicate that the inner sphere complex formation is formed at bare surfaces or FA/HA-bound TiO(2) particle surfaces. Results of SEM analysis show that the particle sizes of TiO(2), Th-TiO(2) and Th-HA-TiO(2) colloids are quite different. Surface complexation may be considered as the main sorption mechanism.

  8. Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid

    NASA Astrophysics Data System (ADS)

    Joseph, C.; Van Loon, L. R.; Jakob, A.; Steudtner, R.; Schmeide, K.; Sachs, S.; Bernhard, G.

    2013-05-01

    The diffusion of U(VI) (c0 = 1 × 10-6 mol/L) in compacted Opalinus Clay from the Mont Terri underground laboratory, Switzerland, was studied in the absence and presence of humic acid (10 mg/L) at two different temperatures (25 °C, 60 °C) under anaerobic conditions. As background electrolyte synthetic Opalinus Clay pore water (pH 7.6, I = 0.36 mol/L) was used. The diffusion-accessible porosity, ɛ, was determined for each Opalinus Clay bore core sample by through-diffusion experiments with tritiated water (HTO) before the U(VI) diffusion experiments were carried out. The values for the effective diffusion and distribution coefficients De and Kd obtained for U(VI) and humic acid at 25 °C as well as at 60 °C showed that humic acid has no significant influence on the U(VI) diffusion. The diffusion profiles of humic acid in Opalinus Clay at 25 and 60 °C indicate the contributions of two different humic acid particle size fractions (<1 kDa and 10-100 kDa). The small-sized humic acid fraction diffused through the whole Opalinus Clay samples at both temperatures within the 3 month duration of the U(VI) diffusion experiments. At 60 °C, diffusion profiles of two different U(VI) species were observed. In a separate experiment the U(VI) speciation in the source reservoir solution at 60 °C was analyzed by laser-induced fluorescence spectroscopy, photon correlation spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector. The two diffusion profiles could be attributed to an unknown colloidal and a known aquatic U(VI) species (Ca2UO2(CO3)3(aq)). The diffusion results showed that the interaction of U(VI) and of the large-sized humic acid colloid fraction with the clay is stronger at 60 °C. An increase of Kd from 0.025 ± 0.003 m3/kg at 25 °C to 0.25 ± 0.05 m3/kg for U(VI)colloidal at 60 °C was determined. In addition, the value for De of U(VI) increased with increasing temperature. Using the De values at 25 and 60 °C, a preliminary

  9. Effects of organic ligands on fractionation of rare earth elements (REEs) in hydroponic plants: an application to the determination of binding capacities by humic acid for modeling.

    PubMed

    Ding, ShiMing; Liang, Tao; Zhang, ChaoSheng; Yan, JunCai; Zhang, ZiLi

    2006-12-01

    Previous studies have revealed the fractionation processes of rare earth elements (REEs) in hydroponic plants, with a heavy REE (HREE, the elements from Gd to Lu) enrichment in leaves. In this study, effects on the HREE enrichment in soybean leaves with additions of carboxylic acids (acetate, malate, citrate, NTA, EDTA and DTPA) and two soil humic acids (HAs) were investigated. REE speciation in carboxylic acid and HA solutions was simulated using Visual MINTEQ and Model V, respectively. The results showed that the effects caused by carboxylic acids were strongly dependent on the differences between their binding strengths for light REEs (LREEs, the elements from La to Eu) and those for HREEs. A good correlation existed between these effects and the changes of free REE ions in solutions. This relationship was also observed for the HA treatments, provided that the intrinsic equilibrium constants of REEs for cation-proton exchange with HA (i.e., pK(MHA)) in Model V were estimated using a free-energy relationship with the stability constants for REE complexation with lactic acid. It is suggested that this set of pK(MHA) values is more suitable for use in Model V for the simulation of REE complexation with HA.

  10. FT-IR and C-13 NMR analysis of soil humic fractions from a long term cropping systems study

    USDA-ARS?s Scientific Manuscript database

    Increased knowledge of humic fractions is important due to its involvement in many soil ecosystem processes. Soil humic acid (HA) and fulvic acid (FA) from a nine-year agroecosystem study with different tillage, cropping system, and N source treatments were characterized using FT-IR andsolid-state ...

  11. Humic acid facilitates the transport of ARS-labeled hydroxyapatite nanoparticles in iron oxyhydroxide-coated sand

    USGS Publications Warehouse

    Wang, Dengjun; Bradford, Scott A.; Harvey, Ronald W.; Gao, Bin; Cang, Long; Zhou, Dongmei

    2012-01-01

    Hydroxyapatite nanoparticles (nHAP) have been widely used to remediate soil and wastewater contaminated with metals and radionuclides. However, our understanding of nHAP transport and fate is limited in natural environments that exhibit significant variability in solid and solution chemistry. The transport and retention kinetics of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated packed columns that encompassed a range of humic acid concentrations (HA, 0–10 mg L–1), fractional surface coverage of iron oxyhydroxide coatings on sand grains (λ, 0–0.75), and pH (6.0–10.5). HA was found to have a marked effect on the electrokinetic properties of ARS-nHAP, and on the transport and retention of ARS-nHAP in granular media. The transport of ARS-nHAP was found to increase with increasing HA concentration because of enhanced colloidal stability and the reduced aggregate size. When HA = 10 mg L–1, greater ARS-nHAP attachment occurred with increasing λ because of increased electrostatic attraction between negatively charged nanoparticles and positively charged iron oxyhydroxides, although alkaline conditions (pH 8.0 and 10.5) reversed the surface charge of the iron oxyhydroxides and therefore decreased deposition. The retention profiles of ARS-nHAP exhibited a hyperexponential shape for all test conditions, suggesting some unfavorable attachment conditions. Retarded breakthrough curves occurred in sands with iron oxyhydroxide coatings because of time-dependent occupation of favorable deposition sites. Consideration of the above effects is necessary to improve remediation efficiency of nHAP for metals and actinides in soils and subsurface environments.

  12. Humic acid facilitates the transport of ARS-labeled hydroxyapatite nanoparticles in iron oxyhydroxide-coated sand.

    PubMed

    Wang, Dengjun; Bradford, Scott A; Harvey, Ronald W; Gao, Bin; Cang, Long; Zhou, Dongmei

    2012-03-06

    Hydroxyapatite nanoparticles (nHAP) have been widely used to remediate soil and wastewater contaminated with metals and radionuclides. However, our understanding of nHAP transport and fate is limited in natural environments that exhibit significant variability in solid and solution chemistry. The transport and retention kinetics of Alizarin red S (ARS)-labeled nHAP were investigated in water-saturated packed columns that encompassed a range of humic acid concentrations (HA, 0-10 mg L(-1)), fractional surface coverage of iron oxyhydroxide coatings on sand grains (λ, 0-0.75), and pH (6.0-10.5). HA was found to have a marked effect on the electrokinetic properties of ARS-nHAP, and on the transport and retention of ARS-nHAP in granular media. The transport of ARS-nHAP was found to increase with increasing HA concentration because of enhanced colloidal stability and the reduced aggregate size. When HA = 10 mg L(-1), greater ARS-nHAP attachment occurred with increasing λ because of increased electrostatic attraction between negatively charged nanoparticles and positively charged iron oxyhydroxides, although alkaline conditions (pH 8.0 and 10.5) reversed the surface charge of the iron oxyhydroxides and therefore decreased deposition. The retention profiles of ARS-nHAP exhibited a hyperexponential shape for all test conditions, suggesting some unfavorable attachment conditions. Retarded breakthrough curves occurred in sands with iron oxyhydroxide coatings because of time-dependent occupation of favorable deposition sites. Consideration of the above effects is necessary to improve remediation efficiency of nHAP for metals and actinides in soils and subsurface environments.

  13. Humic acids from particulate organic matter in the Saguenay Fjord and the St. Lawrence Estuary investigated by advanced solid-state NMR

    NASA Astrophysics Data System (ADS)

    Mao, J.-D.; Tremblay, L.; Gagné, J.-P.; Kohl, S.; Rice, J.; Schmidt-Rohr, K.

    2007-11-01

    Detailed structural information on two humic acids extracted from two sinking particulate matter samples at a water depth of 20 m in the Saguenay Fjord (F-20-HA) and the St. Lawrence Estuary (E-20-HA) (Canada), was obtained by advanced solid-state NMR. Spectral-editing analyses provided numerous structural details rarely reported in geochemical studies. The NMR data account almost quantitatively for the elemental compositions. The two humic acids were found to be quite similar, consisting of four main structural components: peptides (ca. 39 ± 3% vs. 34 ± 3% of all C for E-20-HA and F-20-HA, respectively); aliphatic chains, 14-20 carbons long (ca. 25 ± 5% vs. 17 ± 5% of all C); aromatic structures (ca. 17 ± 2% vs. 26 ± 2% of all C); and sugar rings (14 ± 2% vs. 15 ± 2% of all C). Peptides were identified by 13C{ 14N} SPIDER NMR, which selects signals of carbons bonded to nitrogen, and by dipolar DEPT, which selects CH-group signals, in particular the NCH band of peptides. The SPIDER spectra also indicate that heterocycles constitute a significant fraction of the aromatic structures. The aliphatic (CH 2) n chains, which are highly mobile, contain at least one double bond per two chains and end in methyl groups. 1H spin diffusion NMR experiments showed that these mobile aliphatic chains are in close (<10 nm) proximity to the other structural components. A major bacterial contribution to these two samples could explain why the samples, which have different dominant organic matter sources (terrestrial vs. marine), are similar to each other as well as to degraded algae and particles from other waters. The NMR data suggest structures containing mobile lipids in close proximity to peptides and carbohydrates (e.g., peptidoglycan) as found in bacterial cell walls. Measured yields of muramic acid and D-amino acids confirmed the presence of bacterial cell wall components in the studied samples.

  14. Stimulus-responsive zinc oxide-functionalized macromolecular humic acid nanocarrier for enhancement of antibacterial activity of ciprofloxacin hydrochloride.

    PubMed

    Murugesan, Gowri; Latha, Nachimuthu; Suganya, Kannan; Murugan, Marudhamuthu; Munusamy, Murugan A; Rajan, Mariappan

    2018-07-15

    Macromolecular of naturally occurring humic acid (HA) have garnered interest in the chemical, biological and medicine industry owing to their unique behavior, i.e., strong adsorptive and non-toxic nature. Here, we investigated the functionalization of organic (HA) with inorganic (ZnO) hybrid nanoparticles for topical and site-targeted delivery of ciprofloxacin by simple emulsification techniques. Ciprofloxacin (CIPRO)-encapsulated hybrid nanocarrier constitute an attractive novel drug delivery vehicle for sustained release of antibiotics to bacterial infection sites in an extended and controlled manner. The analytical characteristics of the designed system were thoroughly investigated by FTIR, XRD, SEM/EDAX, and TEM. The drug release of ciprofloxacin over 24h was 87.5%, 98.03%, 97.44%, and 97.24% for pH2.5, 5.5, 6.8, and 8.0, respectively. The antibacterial activities results confirmed that the CIPRO-encapsulated hybrid nanocarrier showed excellent growth inhibition against microorganisms. This hybrid nanocarrier loaded with antibiotics represents a promising approach for targeted and controlled drug delivery to infected sites. Copyright © 2018 Elsevier B.V. All rights reserved.

  15. Coating carbon nanotubes with humic acid using an eco-friendly mechanochemical method: Application for Cu(II) ions removal from water and aquatic ecotoxicity.

    PubMed

    Côa, Francine; Strauss, Mathias; Clemente, Zaira; Rodrigues Neto, Laís L; Lopes, Josias R; Alencar, Rafael S; Souza Filho, Antônio G; Alves, Oswaldo L; Castro, Vera Lúcia S S; Barbieri, Edison; Martinez, Diego Stéfani T

    2017-12-31

    In this work, industrial grade multi-walled carbon nanotubes (MWCNT) were coated with humic acid (HA) for the first time by means of a milling process, which can be considered an eco-friendly mechanochemical method to prepare materials and composites. The HA-MWCNT hybrid material was characterized by atomic force microscopy (AFM), scanning electron microscopies (SEM and STEM), X-ray photoelectron spectroscopy (XPS), termogravimetric analysis (TGA), and Raman spectroscopy. STEM and AFM images demonstrated that the MWCNTs were efficiently coated by the humic acid, thus leading to an increase of 20% in the oxygen content at the nanotube surface as observed by the XPS data. After the milling process, the carbon nanotubes were shortened as unveiled by SEM images and the values of ID/IG intensity ratio increased due to shortening of the nanotubes and increasing in the number defects at the graphitic structure of carbon nanotubes walls. The analysis of TGA data showed that the quantity of the organic matter of HA on the nanotube surface was 25%. The HA coating was responsible to favor the dispersion of MWCNTs in ultrapure water (i.e. -42mV, zeta-potential value) and to improve their capacity for copper removal. HA-MWCNTs hybrid material adsorbed 2.5 times more Cu(II) ions than oxidized MWCNTs with HNO 3 , thus evidencing that it is a very efficient adsorbent material for removing copper ions from reconstituted water. The HA-MWCNTs hybrid material did not show acute ecotoxicity to the tested aquatic model organisms (Hydra attenuata, Daphnia magna, and Danio rerio embryos) up to the highest concentration evaluated (10mgL -1 ). The results allowed concluding that the mechanochemical method is effective to coat carbon nanotubes with humic acid, thus generating a functional hybrid material with low aquatic toxicity and great potential to be applied in environmental nanotechnologies such as the removal of heavy metal ions from water. Copyright © 2017 Elsevier B.V. All rights

  16. Humic acids: Structural properties and multiple functionalities for novel technological developments.

    PubMed

    de Melo, Bruna Alice Gomes; Motta, Fernanda Lopes; Santana, Maria Helena Andrade

    2016-05-01

    Humic acids (HAs) are macromolecules that comprise humic substances (HS), which are organic matter distributed in terrestrial soil, natural water, and sediment. HAs differ from the other HS fractions (fulvic acid and humins) in that they are soluble in alkaline media, partially soluble in water, and insoluble in acidic media. Due to their amphiphilic character, HAs form micelle-like structures in neutral to acidic conditions, which are useful in agriculture, pollution remediation, medicine and pharmaceuticals. HAs have undefined compositions that vary according to the origin, process of obtainment, and functional groups present in their structures, such as quinones, phenols, and carboxylic acids. Quinones are responsible for the formation of reactive oxygen species (ROS) in HAs, which are useful for wound healing and have fungicidal/bactericidal properties. Phenols and carboxylic acids deprotonate in neutral and alkaline media and are responsible for various other functions, such as the antioxidant and anti-inflammatory properties of HAs. In particular, the presence of phenolic groups in HAs provides antioxidant properties due to their free radical scavenging capacity. This paper describes the main multifunctionalities of HAs associated with their structures and properties, focusing on human health applications, and we note perspectives that may lead to novel technological developments. To the best of our knowledge, this is the first review to address this topic from this approach. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Photocatalytic degradation of humic acid in saline waters. Part 1. Artificial seawater: influence of TiO2, temperature, pH, and air-flow.

    PubMed

    Al-Rasheed, Radwan; Cardin, David J

    2003-06-01

    We report the first systematic study on the photocatalytic oxidation of humic acid (HA) in artificial seawater (ASW). TiO(2) (Degussa P25) dispersions were used as the catalyst with irradiation from a medium-pressure mercury lamp. The optimum quantity of catalyst was found to be between 2 and 2.5 gl(-1); while the decomposition was fastest at low pH values (pH 4.5 in the range examined), and the optimum air-flow, using an immersion well reactor with a capacity of 400 ml, was 850 ml min(-1). Reactivity increased with air-flow up to this figure, above which foaming prevented operation of the reactor. Using pure oxygen, an optimal flow rate was observed at 300 ml min(-1), above which reactivity remains essentially constant. Following treatment for 1 h, low-salinity water (2700 mg l(-1)) was completely mineralised, whereas ASW (46000 mg l(-1)) had traces of HA remaining. These effects are interpreted and kinetic data presented. To avoid problems of precipitation due to change of ionic strength humic substances were prepared directly in ASW, and the effects of ASW on catalyst suspension and precipitation have been taken into account. The Langmuir-Hinshelwood kinetic model has been shown to be followed only approximately for the catalytic oxidation of HA in ASW. The activation energy for the reaction derived from an Arrhenius treatment was 17 (+/-0.6) kJ mol(-1).

  18. Influence of herbicide structure, clay acidity, and humic acid coating on acetanilide herbicide adsorption on homoionic clays.

    PubMed

    Liu, Weiping; Gan, Jianying; Yates, Scott R

    2002-07-03

    Adsorption of chloroacetanilide herbicides on homoionic montmorillonite was studied by coupling batch equilibration and FT-IR analysis. Adsorption decreased in the order metolachlor > acetochlor > alachlor > propachlor on Ca(2+)- or Mg(2+)-saturated clays and in the order metolachlor > alachlor > acetachlor > propachlor on Al(3+)- or Fe(3+)-saturated clays. FT-IR spectra showed that the carbonyl group of the herbicide molecule was involved in bonding. For the same herbicide, adsorption of alachlor, acetachlor, and metolachlor on clay followed the order Ca(2+) approximately Mg(2+) < Al(3+) < or = Fe(3+), which coincided with the increasing acidity of homoionic clays. Adsorption of propachlor, however, showed an opposite dependence, suggesting a different governing interaction. In clay and humic acid mixtures, herbicide adsorption was less than that expected from independent additive adsorption by the individual constituents, and the deviation was dependent on the clay-to-humic acid ratio, with the greatest deviation consistently occurring at a 60:40 clay-to-humic acid ratio.

  19. The effect of nanoparticles and humic acid on technology critical element concentrations in aqueous solutions with soil and sand.

    PubMed

    Stepka, Zane; Dror, Ishai; Berkowitz, Brian

    2018-01-01

    As a consequence of their growing use in electronic and industrial products, increasing amounts of technology critical elements (TCEs) are being released to the environment. Currently little is known about the fate of many of these elements. Initial research on their potential environmental impact identifies TCEs as emerging contaminants. TCE movement in the environment is often governed by water systems. Research on "natural" waters so far demonstrates that TCEs tend to be associated with suspended particulate matter (SPM), which influences TCE aqueous concentrations (here: concentration of TCEs in dissolved form and attached to SPM) and transport. However, the relative potential of different types of SPM to interact with TCEs is unknown. Here we examine the potential of various types of particulate matter, namely different nanoparticles (NPs; Al 2 O 3, SiO 2 , CeO 2 , ZnO, montmorillonite, Ag, Au and carbon dots) and humic acid (HA), to impact TCE aqueous concentrations in aqueous solutions with soil and sand, and thus influence TCE transport in soil-water environments. We show that a combination of NPs and HA, and not NPs or HA individually, increases the aqueous concentrations of TCEs in soil solutions, for all tested NPs regardless of their type. TCEs retained on SPM, however, settle with time. In solutions with sand, HA alone is as influential as NPs+HA in keeping TCEs in the aqueous phase. Among NPs, Ag-NPs and Au-NPs demonstrate the highest potential for TCE transport. These results suggest that in natural soil-water environments, once TCEs are retained by soil, their partitioning to the aqueous phase by through-flowing water is unlikely. However, if TCEs are introduced to soil-water environments as part of solutions rich in NPs and HA, it is likely that NP and HA combinations can increase TCE stability in the aqueous phase and prevent their retention on soil and sand, thus facilitating TCE transport. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Glyphosate detection with ammonium nitrate and humic acids as potential interfering substances by pulsed voltammetry technique.

    PubMed

    Martínez Gil, Pablo; Laguarda-Miro, Nicolas; Camino, Juan Soto; Peris, Rafael Masot

    2013-10-15

    Pulsed voltammetry has been used to detect and quantify glyphosate on buffered water in presence of ammonium nitrate and humic substances. Glyphosate is the most widely used herbicide active ingredient in the world. It is a non-selective broad spectrum herbicide but some of its health and environmental effects are still being discussed. Nowadays, glyphosate pollution in water is being monitored but quantification techniques are slow and expensive. Glyphosate wastes are often detected in countryside water bodies where organic substances and fertilizers (commonly based on ammonium nitrate) may also be present. Glyphosate also forms complexes with humic acids so these compounds have also been taken into consideration. The objective of this research is to study the interference of these common pollutants in glyphosate measurements by pulsed voltammetry. The statistical treatment of the voltammetric data obtained lets us discriminate glyphosate from the other studied compounds and a mathematical model has been built to quantify glyphosate concentrations in a buffer despite the presence of humic substances and ammonium nitrate. In this model, the coefficient of determination (R(2)) is 0.977 and the RMSEP value is 2.96 × 10(-5) so the model is considered statistically valid. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. On the role of humic acids' carboxyl groups in the binding of charged organic compounds.

    PubMed

    Smilek, Jiří; Sedláček, Petr; Kalina, Michal; Klučáková, Martina

    2015-11-01

    Interactions of humic acids (HAs) with two cationic dyes (methylene blue and rhodamine 6G) were studied using a unique combination of diffusion and partitioning studies in HAs, containing hydrogels and batch sorption experiments. In order to investigate the involvement of carboxyl groups of HAs in these interactions, all experiments were performed for both, the original lignite HAs and HAs with selectively methylated carboxyls. The results of the diffusion experiments confirm that the interactions between the solute and humic substances have a strong impact on the rate of diffusion process. Surprisingly, the effect is almost equally approved for original and methylated HAs. On the other hand, the results of batch sorption experiments show strong improvement of the sorption capacity (methylated HAs), which is explained by changed morphology of alkylated HAs. The comparison of the results of diffusion and adsorption experiments shows that the diffusion experiments simulate the transport of solutes in natural humics containing environment more reasonably. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Speciation of sulfur in humic and fulvic acids using X-ray absorption near-edge structure (XANES) spectroscopy

    NASA Astrophysics Data System (ADS)

    Morra, Matthew J.; Fendorf, Scott E.; Brown, Paul D.

    1997-02-01

    Sulfur species in soils and sediments have previously been determined indirectly using destructive techniques. A direct and more accurate method for S speciation would improve our understanding of S biogeochemistry. X-ray absorption near edge structure (XANES) spectroscopy was performed on purified humic and fulvic acids from terrestrial and aquatic environments. This methodology allows direct determination of S species using the relationship that exists with the energy required for core electron transitions and in some cases, correlation with additional spectral features. Soil, peat, and aquatic humic acids were dominated by sulfonates with an oxidation state of +5, but also contained ester-bonded sulfates with an oxidation state of +6. Leonardite humic acid contained ester-bonded sulfate and an unidentified S compound with an oxidation state of +4.0. In contrast, high-valent S in soil, peat, and aquatic fulvic acids was exclusively in the form of sulfonic acids. Reduced S species were also present in both humic and fulvic acids. XANES is a valuable method for the speciation of S in humic materials and of potential use in S speciation of unfractionated soils.

  3. Enhanced humification by carbonated basic oxygen furnace steel slag--I. Characterization of humic-like acids produced from humic precursors.

    PubMed

    Qi, Guangxia; Yue, Dongbei; Fukushima, Masami; Fukuchi, Shigeki; Nie, Yongfeng

    2012-01-01

    Carbonated basic oxygen furnace steel slag (hereinafter referred to as "steel slag") is generated during iron and steel manufacturing and is often classified as waste. The effect of steel slag on humification process was investigated. Catechol, glycine and glucose were used as model humic precursors from degraded biowastes. To verify that humification occurred in the system, humic-like acids (HLAs) were isolated and characterized structurally by elemental analysis, FTIR spectra, solid-state CP-MAS (13)C NMR spectra, and TMAH-Py-GC/MS. Characteristics of the steel slag-HLA were compared with those of HLAs formed in the presence of zeolite and birnessite, and with that of mature compost humic acid. The results showed that steel slag-HLA, like zeolite- and birnessite-HLA, is complex organic material containing prominent aromatic structures. Steel slag substantially accelerated the humification process, which would be highly significant for accelerating the stabilization of biowastes during composting (e.g. municipal solid waste, sewage sludge, and food waste). Copyright © 2011 Elsevier Ltd. All rights reserved.

  4. STXM/C 1s-NEXAFS study of Eu(III) and Uranyl humic acid aggregates at different pH

    NASA Astrophysics Data System (ADS)

    Plaschke, M.; Rothe, J.; Denecke, M. A.; Geckeis, H.

    2010-04-01

    Humic acids (HA) are chemically heterogeneous and structurally ill-defined biopolymers which are able to bind traces of actinides or lanthanides. Due to their dimensions in the colloidal size range they may affect transport of these elements in aquatic systems. Eu(III)- and UO22+-HA aggregates have been investigated by Scanning Transmission X-ray Microscopy (STXM) and C 1s-NEXAFS under systematic variation of pH. In the Eu(III)- and UO22+-HA systems aggregate morphologies at near neutral pH were similar to those observed in previous studies: optically dense zones (high absorption at the carbon K-edge) are embedded in a matrix of less dense material. C 1s-NEXAFS signatures observed in the different zones, i.e., the intensity of the characteristic complexation feature previously experimentally described and recently theoretically characterized, strongly depends on sample pH. In the alkaline regime (pH 9) with added carbonate, co-precipitation of Eu(III)-carbonate (or ternary carbonate/(oxo)hydroxide complexes) with the Eu(III)-HA majority fraction is observed but Eu(III) binding to HA over carbonate in the dense zones seems to be favoured. The UO22+-HA system exhibits in alkaline solution more compact morphologies combined with a strong metal ion complexation effect in the NEXAFS. Eu(III) and UO22+ polyacrylic acid (PAA) aggregates used as HA model systems show similar spectral trends; these aggregates exhibit highly branched morphologies without segregation into zones with different NEXAFS signatures. The chemical environment such as pH or the type of metal cation strongly influences both HA aggregate morphologies and NEXAFS spectral signatures. These can, in turn, be used as indicators of the strength of lanthanide or actinide ion bound HA interaction.

  5. Influence of Humic Acid on Stability and Attachment of nTiO2 Particles to Sand at Different pH

    NASA Astrophysics Data System (ADS)

    Cheng, T.

    2015-12-01

    Stability of nano-scale or micro-scale titanium dioxide particles (nTiO2) and their attachment to sediment grains have important implications to the fate and transport of nTiO2 in subsurface environments. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the stability and transport of negatively charged colloids, may influence nTiO2 in different manners. The objective of this study is to investigate the effects of pH and humic acid (HA) on the stability and attachment of nTiO2 to sand, with special attention to low HA concentration ranges that are relevant to groundwater conditions. Stability and attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand were experimentally measured under a range of low HA concentrations at pH 5 and 9. Results showed that HA can either promote or hinder nTiO2 stability, depending on pH and HA concentration. We also found that HA can either enhance or reduce nTiO2 attachment to Fe oxyhydroxide coating at pH 5, depending on HA concentration. Results further showed that at pH 5, Fe oxyhydroxide coating reduced nTiO2 attachment to sand in the absence of HA but increased nTiO2 attachment in the presence of low concentration of HA. Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was invoked to analyze particle-to-particle and particle-to-sand interactions in order to elucidate the roles of pH, HA, quartz, and Fe coating in nTiO2 stability and attachment. Overall, this study showed that changes in zeta potential of nTiO2 and Fe coating due to pH changes and/or HA adsorption are the key factors that influence stability and attachment of nTiO2.

  6. 15N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose

    USGS Publications Warehouse

    Thorn, K.A.; Kennedy, K.R.

    2002-01-01

    The five major reductive degradation products of TNT-4ADNT (4-amino-2,6-dinitrotoluene), 2ADNT (2-amino-4,6-dinitrotoluene), 2,4DANT (2,4-diamino-6-nitrotoluene), 2,6DANT (2,6-diamino-4-nitrotoluene), and TAT (2,4,6-triaminotoluene)-labeled with 15N in the amine positions, were reacted with the IHSS soil humic acid and analyzed by 15N NMR spectrometry. In the absence of catalysts, all five amines underwent nucleophilic addition reactions with quinone and other carbonyl groups in the soil humic acid to form both heterocyclic and nonheterocyclic condensation products. Imine formation via 1,2-addition of the amines to quinone groups in the soil humic acid was significant with the diamines and TAT but not the monoamines. Horseradish peroxidase (HRP) catalyzed an increase in the incorporation of all five amines into the humic acid. In the case of the diamines and TAT, HRP also shifted the binding away from heterocyclic condensation product toward imine formation. A comparison of quantitative liquid phase with solid-state CP/MAS 15N NMR indicated that the CP experiment underestimated imine and heterocyclic nitrogens in humic acid, even with contact times optimal for observation of these nitrogens. Covalent binding of the mono- and diamines to 4-methylcatechol, the HRP catalyzed condensation of 4ADNT and 2,4DANT to coniferyl alcohol, and the binding of 2,4DANT to lignocellulose with and without birnessite were also examined.

  7. Effects of humic acids from landfill leachate on plants: An integrated approach using chemical, biochemical and cytogenetic analysis.

    PubMed

    Morozesk, Mariana; Bonomo, Marina Marques; Souza, Iara da Costa; Rocha, Lívia Dorsch; Duarte, Ian Drumond; Martins, Ian Oliveira; Dobbss, Leonardo Barros; Carneiro, Maria Tereza Weitzel Dias; Fernandes, Marisa Narciso; Matsumoto, Silvia Tamie

    2017-10-01

    Biological process treatment of landfill leachate produces a significant amount of sludge, characterized by high levels of organic matter from which humic acids are known to activate several enzymes of energy metabolism, stimulating plant growth. This study aimed to characterize humic acids extracted from landfill sludge and assess the effects on plants exposed to different concentrations (0.5, 1, 2 and 4 mM C L -1 ) by chemical and biological analysis, to elucidate the influence of such organic material and minimize potential risks of using sludge in natura. Landfill humic acids showed high carbon and nitrogen levels, which may represent an important source of nutrients for plants. Biochemical analysis demonstrated an increase of enzyme activity, especially H + -ATPase in 2 mM C L -1 landfill humic acid. Additionally, cytogenetic alterations were observed in meristematic and F 1 cells, through nuclear abnormalities and micronuclei. Multivariate statistical analysis provided integration of physical, chemical and biological data. Despite all the nutritional benefits of humic acids and their activation of plant antioxidant systems, the observed biological effects showed concerning levels of mutagenicity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Influence of pH, soil humic/fulvic acid, ionic strength, foreign ions and addition sequences on adsorption of Pb(II) onto GMZ bentonite.

    PubMed

    Wang, Suowei; Hu, Jun; Li, Jiaxing; Dong, Yunhui

    2009-08-15

    This work contributed to the adsorption of Pb(II) onto GMZ bentonite in the absence and presence of soil humic acid (HA)/fulvic acid (FA) using a batch technique. The influences of pH from 2 to 12, ionic strengths from 0.004M to 0.05M NaNO(3), soil HA/FA concentrations from 1.6 mg/L to 20mg/L, foreign cations (Li+, Na+, K+), anions (Cl(-), NO(3)(-)), and addition sequences on the adsorption of Pb(II) onto GMZ bentonite were tested. The adsorption isotherms of Pb(II) were determined at pH 3.6+/-0.1 and simulated with the Langmuir, Freundlich, and D-R adsorption models, respectively. The results demonstrated that the adsorption of Pb(II) onto GMZ bentonite increased with increasing pH from 2 to 6. HA was shown to enhance Pb(II) adsorption at low pH, but to reduce Pb(II) adsorption at high pH, whereas FA was shown to decrease Pb(II) adsorption at pH from 2 to 11. The results also demonstrated that the adsorption was strongly dependent on ionic strength and slightly dependent on the concentration of HA/FA. The adsorption of Pb(II) onto GMZ bentonite was dependent on foreign ions in solution. The addition sequences of bentonite/Pb(II)/HA had no effect on the adsorption of Pb(II).

  9. Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation.

    PubMed

    Liu, Xianli; Xu, Dong; Wu, Feng; Liao, Zhenhuan; Liu, Jiantong; Deng, Nansheng

    2004-03-01

    Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals (*OH) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that *OH photoproduction increased from 1.80 to 2.74 microM by increasing the HA concentration from 10 to 40 mg L(-1) at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of *OH in the HA solution with Fe(III) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of *OH in HA solution with algae with or without Fe(III) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of *OH in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest *OH photoproduction at pH 4.0.

  10. Rapid and efficient removal of Pb(II) from aqueous solutions using biomass-derived activated carbon with humic acid in-situ modification.

    PubMed

    Guo, Zizhang; Zhang, Jian; Kang, Yan; Liu, Hai

    2017-11-01

    This study developed an humic acid (HA) in-situ modified activated carbon adsorbent (AC-HA) for the rapid and efficient removal of Pb(II) from aqueous media, and adsorption mechanisms are discussed. The physicochemical characteristics of activated carbons (AC) were investigated via N 2 adsorption/desorption, scanning electron microscopy (SEM), Boehm's titration method and Fourier transform infrared spectroscopy (FTIR). AC-HA exhibited richer oxygen-containing functional groups than the original AC. In addition, the removal performance of AC-HA (250.0mg/g) toward Pb(II) was greatly improved compared with the original AC (166.7mg/g). The batch adsorption study results revealed that the Pb(II) adsorption data were best fit by the pseudo-second-order model of kinetics and Langmuir isotherm of isothermals, and therefore, the effect of the solution pH was studied. The superior performance of AC-HA was attributed to the HA modification, which contains numbers of groups and has a strong π-π interaction binding energy with AC and Pb(II) species. The adsorption mechanisms were confirmed via the XPS study. More importantly, the modified method is simple and has a low cost of production. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Humic Acid Increases Amyloid β-Induced Cytotoxicity by Induction of ER Stress in Human SK-N-MC Neuronal Cells

    PubMed Central

    Li, Hsin-Hua; Lu, Fung-Jou; Hung, Hui-Chih; Liu, Guang-Yaw; Lai, Te-Jen; Lin, Chih-Li

    2015-01-01

    Humic acid (HA) is a possible etiological factor associated with for several vascular diseases. It is known that vascular risk factors can directly increase the susceptibility to Alzheimer’s disease (AD), which is a neurodegenerative disorder due to accumulation of amyloid β (Aβ) peptide in the brain. However, the role that HA contributes to Aβ-induced cytotoxicity has not been demonstrated. In the present study, we demonstrate that HA exhibits a synergistic effect enhancing Aβ-induced cytotoxicity in cultured human SK-N-MC neuronal cells. Furthermore, this deterioration was mediated through the activation of endoplasmic reticulum (ER) stress by stimulating PERK and eIF2α phosphorylation. We also observed HA and Aβ-induced cytotoxicity is associated with mitochondrial dysfunction caused by down-regulation of the Sirt1/PGC1α pathway, while in contrast, treating the cells with the ER stress inhibitor Salubrinal, or over-expression of Sirt1 significantly reduced loss of cell viability by HA and Aβ. Our findings suggest a new mechanism by which HA can deteriorate Aβ-induced cytotoxicity through modulation of ER stress, which may provide significant insights into the pathogenesis of AD co-occurring with vascular injury. PMID:25961951

  12. [Apply fourier transform infrared spectra coupled with two-dimensional correlation analysis to study the evolution of humic acids during composting].

    PubMed

    Bu, Gui-jun; Yu, Jing; Di, Hui-hui; Luo, Shi-jia; Zhou, Da-zhai; Xiao, Qiang

    2015-02-01

    The composition and structure of humic acids formed during composting play an important influence on the quality and mature of compost. In order to explore the composition and evolution mechanism, municipal solid wastes were collected to compost and humic and fulvic acids were obtained from these composted municipal solid wastes. Furthermore, fourier transform infrared spectra and two-dimensional correlation analysis were applied to study the composition and transformation of humic and fulvic acids during composting. The results from fourier transform infrared spectra showed that, the composition of humic acids was complex, and several absorbance peaks were observed at 2917-2924, 2844-2852, 2549, 1662, 1622, 1566, 1454, 1398, 1351, 990-1063, 839 and 711 cm(-1). Compared to humic acids, the composition of fulvci acids was simple, and only three peaks were detected at 1725, 1637 and 990 cm(-1). The appearance of these peaks showed that both humic and fulvic acids comprised the benzene originated from lignin and the polysaccharide. In addition, humic acids comprised a large number of aliphatic and protein which were hardly detected in fulvic acids. Aliphatic, polysaccharide, protein and lignin all were degraded during composting, however, the order of degradation was different between humic and fulvci acids. The result from two-dimensional correlation analysis showed that, organic compounds in humic acids were degraded in the following sequence: aliphatic> protein> polysaccharide and lignin, while that in fulvic acids was as following: protein> polysaccharide and aliphatic. A large number of carboxyl, alcohols and ethers were formed during the degradation process, and the carboxyl was transformed into carbonates. It can be concluded that, fourier transform infrared spectra coupled with two-dimensional correlation analysis not only can analyze the function group composition of humic substances, but also can characterize effectively the degradation sequence of these

  13. Structure and catalytic activities of ferrous centers confined on the interface between carbon nanotubes and humic acid

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhou, Xiaoyan; Wang, Dongqi; Yin, Jun-Jie; Chen, Hanqing; Gao, Xingfa; Zhang, Jing; Ibrahim, Kurash; Chai, Zhifang; Feng, Weiyue; Zhao, Yuliang

    2015-01-01

    Preparation of heterogeneous catalysts with active ferrous centers is of great significance for industrial and environmental catalytic processes. Nanostructured carbon materials (NCM), which possess free-flowing π electrons, can coordinate with transition metals, provide a confinement environment for catalysis, and act as potential supports or ligands to construct analogous complexes. However, designing such catalysts using NCM is still seldom studied to date. Herein, we synthesized a sandwich structured ternary complex via the coordination of Fe-loaded humic acid (HA) with C&z.dbd;C bonds in the aromatic rings of carbon nanotubes (CNTs), in which the O/N-Fe-C interface configuration provides the confinement environment for the ferrous sites. The experimental and theoretical results revealed octahedrally/tetrahedrally coordinated geometry at Fe centers, and the strong hybridization between CNT C π* and Fe 3d orbitals induces discretization of the atomic charges on aromatic rings of CNTs, which facilitates O2 adsorption and electron transfer from carbon to O2, which enhances O2 activation. The O2 activation by the novel HA/Fe-CNT complex can be applied in the oxidative degradation of phenol red (PR) and bisphenol A (BPA) in aqueous media.Preparation of heterogeneous catalysts with active ferrous centers is of great significance for industrial and environmental catalytic processes. Nanostructured carbon materials (NCM), which possess free-flowing π electrons, can coordinate with transition metals, provide a confinement environment for catalysis, and act as potential supports or ligands to construct analogous complexes. However, designing such catalysts using NCM is still seldom studied to date. Herein, we synthesized a sandwich structured ternary complex via the coordination of Fe-loaded humic acid (HA) with C&z.dbd;C bonds in the aromatic rings of carbon nanotubes (CNTs), in which the O/N-Fe-C interface configuration provides the confinement environment for the

  14. Nature differences of humic acids fractions induced by extracted sequence as explanatory factors for binding characteristics of heavy metals.

    PubMed

    Shi, Wenjing; Lü, Changwei; He, Jiang; En, He; Gao, Manshu; Zhao, Boyi; Zhou, Bin; Zhou, Haijun; Liu, Hualin; Zhang, Yu

    2018-06-15

    The composition and structure of Humic acid (HA) is so heterogeneous that it brings significant barriers to investigate the interaction between HA and heavy metal ions. The isolation of HA with relatively homogeneity is a key to reveal the binding mechanisms between HA and heavy metals. In this work, ten HA fractions (HAs) were obtained by sequential alkali extraction procedure and nature differences of the extracted HAs were considered as explanatory factors for binding characteristics of Cu 2+ , Pb 2+ and Cd 2+ . The results indicate that more large molecular weight (MW) HA subunits, less carboxyl and phenolic group contents, weaker aromaticity and polarity were measured with increasing extractions, inducing weaker binding capacity of HAs. Ligand binding and bi-Langmuir models indicated that the sorption capacity and binding affinity of earlier extracted HAs were higher than the latter ones. The peak area changes at 3427, 1599, and 619 cm -1 pre- and post-adsorption in FTIR spectra suggested carboxyl, phenolic and nitrogen-containing groups were involved in the adsorption process. At the same time, the peak area difference between HAs and HAs-metal (ΔS) of phenolic groups were 8.22-20.50, 6.81-21.11 and 10.66-19.80% for Cu 2+ , Pb 2+ and Cd 2+ , respectively, ΔS of carboxyl groups 6.64-17.03, 8.96-16.82 and 9.45-17.85% for Cu 2+ , Pb 2+ and Cd 2+ , respectively, ΔS of nitrogen-containing groups 0.33-0.48, 0.20-1.38 and 0.31-0.59% for Cu 2+ , Pb 2+ and Cd 2+ , respectively. ΔS of phenolic and carboxyl groups were larger than those of nitrogen-containing groups, implying that these two groups were the predominant binding sites suppliers for metal ions, which were also supported by the results of correlation analysis. This work is helpful to insight the environmental impacts of natural organic matter and the fate of heavy metals in natural environment. Copyright © 2018 Elsevier Inc. All rights reserved.

  15. Nanoparticle-assisted photo-Fenton reaction for photo-decomposition of humic acid

    NASA Astrophysics Data System (ADS)

    Banik, Jhuma; Basumallick, Srijita

    2017-11-01

    We report here the synthesis of CuO-doped ZnO composite nanomaterials (NMs) by chemical route and demonstrated for the first time that these NMs are efficient catalysts for H2O2-assisted photo-decomposition (photo-Fenton type catalyst) of humic acid, a natural pollutant of surface water by solar irradiation. This has been explained by faster electron transfer to OH radical at the p-n hetero-junction of this composite catalyst. Application of this composite catalyst in decomposing humus substances of local pond water by solar energy has been demonstrated.

  16. HA Antibody-Mediated FcγRIIIa Activity Is Both Dependent on FcR Engagement and Interactions between HA and Sialic Acids.

    PubMed

    Cox, Freek; Kwaks, Ted; Brandenburg, Boerries; Koldijk, Martin H; Klaren, Vincent; Smal, Bastiaan; Korse, Hans J W M; Geelen, Eric; Tettero, Lisanne; Zuijdgeest, David; Stoop, Esther J M; Saeland, Eirikur; Vogels, Ronald; Friesen, Robert H E; Koudstaal, Wouter; Goudsmit, Jaap

    2016-01-01

    Interactions with receptors for the Fc region of IgG (FcγRs) have been shown to contribute to the in vivo protection against influenza A viruses provided by broadly neutralizing antibodies (bnAbs) that bind to the viral hemagglutinin (HA) stem. In particular, Fc-mediated antibody-dependent cellular cytotoxicity (ADCC) has been shown to contribute to protection by stem-binding bnAbs. Fc-mediated effector functions appear not to contribute to protection provided by strain-specific HA head-binding antibodies. We used a panel of anti-stem and anti-head influenza A and B monoclonal antibodies with identical human IgG1 Fc domains and investigated their ability to mediate ADCC-associated FcγRIIIa activation. Antibodies which do not interfere with sialic acid binding of HA can mediate FcγRIIIa activation. However, the FcγRIIIa activation was inhibited when a mutant HA, unable to bind sialic acids, was used. Antibodies which block sialic acid receptor interactions of HA interfered with FcγRIIIa activation. The inhibition of FcγRIIIa activation by HA head-binding and sialic acid receptor-blocking antibodies was confirmed in plasma samples of H5N1 vaccinated human subjects. Together, these results suggest that in addition to Fc-FcγR binding, interactions between HA and sialic acids on immune cells are required for optimal Fc-mediated effector functions by anti-HA antibodies.

  17. Influence of humic acid concentration on nTiO2 attachment to quartz sand and Fe-coated quartz sand

    NASA Astrophysics Data System (ADS)

    Cheng, T.; Wu, Y.

    2016-12-01

    The transport of nano-scale or micro-scale titanium dioxide particles (nTiO2) in subsurface environments are strongly influenced by nTiO2 attachment to sediment grains. The objective of this study is to investigate the role of humic acid (HA) in the attachment of nTiO2 to sand at low HA concentrations that are relevant to typical groundwater conditions, so that mechanisms that control nTiO2 immobilization and transport in groundwater can be elucidated. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the transport of negatively-charged colloids, may influence nTiO2 in different manners. Attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand are experimentally measured under a range of HA concentrations at fixed pH. Experimental results show that at pH 5, negatively-charged HA strongly adsorbs to positively-charged nTiO2 and Fe oxyhydroxide, which, at low HA concentrations, partially neutralizes the positive charges on nTiO2 and Fe oxyhydroxide, and therefore decreases the repulsive electrostatic forces between the surfaces, resulting in relatively high nTiO2 attachment. At high HA concentrations, adsorbed HA reverses the surface charges of nTiO2 and Fe oxyhydroxide, and makes nTiO2 and Fe oxyhydroxide strongly negatively charged, resulting in low nTiO2 attachment. At pH 9, HA, nTiO2, and Fe oxyhydroxide are all negatively charged, and HA adsorption is low and does not have a strong impact on the attachment of nTiO2. This study demonstrates that the changes in surface charges of nTiO2 and Fe oxyhydroxide coating caused by HA adsorption could be a key factor that controls the attachment of nTiO2 to sediment grains.

  18. Stability of nTiO2 particles and their attachment to sand: Effects of humic acid at different pH.

    PubMed

    Wu, Yang; Cheng, Tao

    2016-01-15

    The fate and transport of nano-scale or micro-scale titanium dioxide particles (nTiO2) in subsurface environments are strongly influenced by the stability of nTiO2 and their attachment to sediment grains. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the stability and transport of negatively-charged colloids, may influence nTiO2 in different manners. The objective of this study is to investigate the effects of pH and humic acid (HA) on the stability and attachment of nTiO2 to sand at HA concentrations that are relevant to typical groundwater conditions, so that mechanisms that control nTiO2 immobilization and transport in natural systems can be elucidated. Stability and attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand are experimentally measured under a range of HA concentrations at pH5 and 9. Results show that at pH5, negatively-charged HA strongly adsorbs to positively-charged nTiO2 and Fe oxyhydroxide, which, at low HA concentrations, partially neutralizes the positive charges on nTiO2 and Fe oxyhydroxide, and therefore decreases the repulsive electrostatic forces between the surfaces, resulting in nTiO2 aggregation and attachment. At high HA concentrations, adsorbed HA reverses the surface charges of nTiO2 and Fe oxyhydroxide, and makes nTiO2 and Fe oxyhydroxide strongly negatively charged, resulting in stable nTiO2 suspension and low nTiO2 attachment. At pH9, HA, nTiO2, and Fe oxyhydroxide are all negatively charged, and HA adsorption is low and does not have a strong impact on the stability and attachment of nTiO2. Overall, this study shows that changes in surface charges of nTiO2 and Fe oxyhydroxide coating caused by HA adsorption is a key factor that influences the stability and attachment of nTiO2. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Adsorption of MCPA on goethite and humic acid-coated goethite.

    PubMed

    Iglesias, A; López, R; Gondar, D; Antelo, J; Fiol, S; Arce, F

    2010-03-01

    Anionic pesticides are adsorbed on the mineral oxide fraction of the soil surface but considerably less on the organic fraction, so that the presence of organic matter causes a decrease in the amount of pesticide adsorbed, and may affect the mechanism of adsorption. In the present study we investigated the adsorption of the weak acid pesticide MCPA on the surface of goethite and of humic acid-coated goethite, selected as models of the mineral oxide fraction and organic components present in soil systems. Adsorption of the anionic form of the pesticide on goethite fitted an S-type isotherm and the amount adsorbed increased as the ionic strength decreased and the pH of the medium decreased. Application of the charge distribution multi site complexation model (CD-MUSIC model) enabled interpretation of the results, which suggested the formation of inner and outer sphere complexes between the pesticide and the singly-coordinated surface sites of goethite. Less pesticide was adsorbed on the humic acid-coated goethite than on the bare goethite and the pattern fitted an L-type isotherm, which indicates a change in the mechanism of adsorption. Simplified calculations with the CD-MUSIC model enabled interpretation of the results, which suggested that the pesticide molecules form the same type of surface complexes as in the previous case. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  20. Effects of the addition and aging of humic acid-based amendments on the solubility of Cd in soil solution and its accumulation in rice.

    PubMed

    Yu, Yao; Wan, Yanan; Camara, Aboubacar Younoussa; Li, Huafen

    2018-04-01

    Humic substances can reduce mobility and bio-accessibility of Cd in soil and therefore inhibit its uptake by rice, which is a major source of human Cd intake. Yet, the effects of aging humic substances are not fully understood. A rice pot experiment was conducted to evaluate the effects of humic acid-based amendments on the mobility of Cd in soil solution and its uptake by rice when amendments were freshly added or aged for 130 d. The results showed that the aged and the unaged amendments generally decreased Cd concentration in soil solution, but the effect declined with time. Unaged HA-K (humic-potassium) reduced Cd concentration by 88% for the first sampling, but this dropped to 46% for the last sampling, compared to that of the control. All amendments, whether aged or not, reduced the content of Cd in rice seedlings, as well as in mature plants. Aged and unaged woody peat reduced the Cd content in seedlings by 79% and in grains by 70%, respectively. Aging of amendments caused lower pH and higher Cd concentration in the soil solution for all amendments and accordingly, the Cd content in rice seedlings or each part of mature plants in the aged group was higher than that of the unaged group. The applied amendments might reduce the solubility of Cd through the alteration in soil pH, and thus inhibit the uptake of Cd by rice, but the effects diminished with aging. Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Effects of dietary humic and butyric acid on growth performance and response to lipopolysaccharide in young pigs

    USDA-ARS?s Scientific Manuscript database

    Humic acid (MFG) and fat protected butyric acid (BA) has been shown to modulate energy metabolism and inflammation. Therefore, the objectives of this study were to determine the effects of MFG and BA, alone and in combination, on growth performance and response to lipopolysaccharide (LPS) induced in...

  2. Influence of Humic Acids Extracted from Peat by Different Methods on Functional Activity of Macrophages in Vitro.

    PubMed

    Trofimova, E S; Zykova, M V; Ligacheva, A A; Sherstoboev, E Y; Zhdanov, V V; Belousov, M V; Yusubov, M S; Krivoshchekov, S V; Danilets, M G; Dygai, A M

    2017-04-01

    We studied activation of macrophages with humic acids extracted from peat of large deposits in the Tomsk region by two extraction methods: by hydroxide or sodium pyrophosphate. Humic acid of lowland peat types containing large amounts of aromatic carbon, phenolic and alcohol groups, carbohydrate residues and ethers, irrespectively of the extraction methods contained LPS admixture that probably determines their activating properties. Humic acid of upland peat types characterized by high content of carbonyl, carboxyl, and ester groups enhance NO production and reduce arginase expression, but these effects were minimized when sodium hydroxide was used as an extraction solvent. Pyrophosphate samples of the upland peat types were characterized by aromaticity and diversity of functional groups and have a significant advantage because of they induce specific endotoxin-independent stimulating action on antigen presenting cells.

  3. The influence of dissolved and surface-bound humic acid on the toxicity of TiO₂ nanoparticles to Chlorella sp.

    PubMed

    Lin, Daohui; Ji, Jing; Long, Zhifeng; Yang, Kun; Wu, Fengchang

    2012-09-15

    NOM is likely to coat TiO₂ nanoparticles (nano-TiO₂) discharged into the aquatic environment and influence the nanotoxicity to aquatic organisms, which however has not been well investigated. This study explored the influence of nanoparticle surface-bound humic acid (HA, as a model NOM) as well as dissolved HA on the toxicity of nano-TiO₂ to Chlorella sp., with a specific focus on adhesion of the nanoparticles to the algae. Results showed that nano-TiO₂ and the dissolved HA could inhibit the algal growth with an IC₅₀ of 4.9 and 8.4 mg L⁻¹, respectively, while both dissolved and nanoparticle surface-bound HA could significantly alleviate the algal toxicity of nano-TiO₂. IC₅₀ of nano-TiO₂ increased to 18 mg L⁻¹ in the presence of 5 mg L⁻¹ of the dissolved HA and to 48 mg L⁻¹ as the result of surface-saturation by HA. Co-precipitation experiment and transmission electron microscopy observation revealed that both dissolved and nanoparticle surface-bound HA prevented the adhesion of nano-TiO₂ to the algal cells due to the increased electrosteric repulsion. The generation of intracellular reactive oxygen species (ROS) was significantly limited by the dissolved and nanoparticle surface-bound HA. The prevention of adhesion and inhibition of ROS generation could account for the HA-mitigated nanotoxicity. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. Effect of Humic Acids and pesticides on Agricultural Soil Structure and Stability and Its Implication on Soil Quality

    NASA Astrophysics Data System (ADS)

    Gaonkar, O. D.; Nambi, I. M.; G, S. K.

    2016-12-01

    The functional and morphological aspects of soil structure determine the soil quality. The dispersion of colloidal soil particles, especially the clay fraction and rupture of soil aggregates, both of which play an important role in soil structure development, lead to degradation of soil quality. The main objective of this work was to determine the effect of behaviour of soil colloids on the agricultural soil structure and quality. The effect of commercial humic acid, organophosphate pesticides and soil natural organic matter on the electrical and structural properties of the soil colloids was also studied. Agricultural soil, belonging to the sandy loam texture class from northern part of India was considered in this study. In order to understand the changes in the soil quality in the presence and absence of humic acids, the soil fabric and structure was analyzed by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM). Electrical properties of natural soil colloids in aqueous suspensions were assessed by zeta potential measurements at varying pH values with and without the presence of humic acids and pesticides. The influence of natural organic matter was analyzed by oxidizing the natural soil organic matter with hydrogen peroxide. The zeta potential of the soil colloids was found to be negative in the pH range studied. The results indicated that hydrogen peroxide treatment lead to deflocculation of colloidal soil particles. In addition, the humic acids undergoes effective adsorption onto the soil surface imparting more negative zeta potential to the colloidal soil particles. The soil hydrophilicity decreased in the presence of humic acids which was confirmed by surface free energy determination. Thus, it can be concluded that the presence of humic acids altered the soil fabric and structure, thereby affecting the soil quality. This study assumes significance in understanding the soil aggregation and the

  5. Pb(II), Cr(VI) and atrazine sorption behavior on sludge-derived biochar: role of humic acids.

    PubMed

    Zhou, Fengsa; Wang, Hong; Fang, Sheng'en; Zhang, Weihua; Qiu, Rongliang

    2015-10-01

    Pyrolyzing municipal wastewater treatment sludge into biochar can be a promising sludge disposal approach, especially as the produced sludge-derived biochar (SDBC) is found to be an excellent sorbent for heavy metals and atrazine. The aim of this study was to investigate how and why the coexisting humic acids influence the sorption capacity, kinetic, and binding of these contaminants on SDBC surface. Results showed humic acids enhanced Pb(II)/Cr(VI) sorption binding, and increased the corresponding Pb(II) Langmuir sorption capacity at pH 5.0 from 197 to 233 μmol g(-1), and from 688 to 738 μmol g(-1) for Cr(VI) at pH 2.0. It can be mainly attributed to the sorbed humic acids, whose active functional groups can offer the additional sites to form stronger inner-sphere complexes with Pb(2+), and supply more reducing agent to facilitate the transformation of Cr(VI) to Cr(III). However, humic acids reduced the atrazine adsorption Freundlich constant from 1.085 to 0.616 μmol g(-1). The pore blockage, confirmed by the decreased BET-specific surface area, as well as the more hydrophilic surface with more sorbed water molecules may be the main reasons for that suppression. Therefore, the coexisting humic acids may affect heavy metal stabilization or pesticide immobilization during SDBC application to contaminated water or soils, and its role thus should be considered especially when organic residues are also added significantly to increase the humic acid content there.

  6. Association of 16 priority polycyclic aromatic hydrocarbons with humic acid and humin fractions in a peat soil and implications for their long-term retention.

    PubMed

    Chen, Weixiao; Wang, Hui; Gao, Qian; Chen, Yin; Li, Senlin; Yang, Yu; Werner, David; Tao, Shu; Wang, Xilong

    2017-11-01

    To elucidate the environmental fate of polycyclic aromatic hydrocarbons (PAHs) once released into soil, sixteen humic acids (HAs) and one humin (HM) fractions were sequentially extracted from a peat soil, and sixteen priority PAHs in these humic substances (HSs) were analyzed. It was found that the total concentration of 16 PAHs (∑16PAHs) increased evidently from HA1 to HA16, and then dramatically reached the highest value in HM. The trend of ∑16PAHs in HAs relates to surface carbon and C-H/C-C contents, the bulk aliphatic carbon content and aliphaticity, as well as the condensation enhancement of carbon domains, which were derived from elemental composition, XPS, 13 C NMR, as well as thermal analyses. HM was identified to be the dominant sink of 16 PAHs retention in soil, due to its aliphatic carbon-rich chemical composition and the highly condensed physical makeup of its carbon domains. This study highlights the joint roles of the physical and chemical properties of HSs in retention of PAHs in soil and the associated mechanisms; the results are of significance for PAH-polluted soil risk assessment and remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Application of a set of complementary techniques to understand how varying the proportion of two wastes affects humic acids produced by vermicomposting.

    PubMed

    Fernández-Gómez, Manuel J; Nogales, Rogelio; Plante, Alain; Plaza, César; Fernández, José M

    2015-01-01

    A better understanding of how varying the proportion of different organic wastes affects humic acid (HA) formation during vermicomposting would be useful in producing vermicomposts enriched in HAs. With the aim of improving the knowledge about this issue, a variety of analytical techniques [UV-visible spectroscopic, Fourier transform infrared, fluorescence spectra, solid-state cross-polarization magic-angle spinning (CPMAS) (13)C nuclear magnetic resonance (NMR) spectra, and thermal analysis] was used in the present study to characterize HAs isolated from two mixtures at two different ratios (2:1 and 1:1) of tomato-plant debris (TD) and paper-mill sludge (PS) before and after vermicomposting. The results suggest that vermicomposting increased the HA content in the TD/PS 2:1 and 1:1 mixtures (15.9% and 16.2%, respectively), but the vermicompost produced from the mixture with a higher amount of TD had a greater proportion (24%) of HAs. Both vermicomposting processes caused equal modifications in the humic precursors contained in the different mixtures of TD and PS, and consequently, the HAs in the vermicomposts produced from different waste mixtures exhibited analogous characteristics. Only the set of analytical techniques used in this research was able to detect differences between the HAs isolated from each type of vermicompost. In conclusion, varying the proportion of different wastes may have a stronger influence on the amount of HAs in vermicomposts than on the properties of HAs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Effect of Several Clay Minerals and Humic Acid on the Survival of Klebsiella aerogenes Exposed to Ultraviolet Irradiation1

    PubMed Central

    Bitton, Gabriel; Henis, Y.; Lahav, N.

    1972-01-01

    The effect of various clay minerals and humic acid on the survival of Klebsiella aerogenes exposed to ultraviolet (UV) irradiation was investigated. A protective effect was observed and found to depend on the specific light absorption and light scattering properties of the clay minerals and the humic acid used. The higher the specific absorption, the better was the survival of K. aerogenes after UV irradiation. Bacterial survival was lower in clays saturated with divalent cations (Ca, Zn) than in those homoionic to monovalent cations (K). PMID:5031559

  9. The duration of hyaluronidase and optimal timing of hyaluronic acid (HA) filler reinjection after hyaluronidase injection.

    PubMed

    Kim, H J; Kwon, S B; Whang, K U; Lee, J S; Park, Y L; Lee, S Y

    2018-02-01

    Hyaluronidase injection is a commonly performed treatment for overcorrection or misplacement of hyaluronic acid (HA) filler. Many patients often wants the HA filler reinjection after the use of hyaluronidase, though the optimal timing of reinjection of HA filler still remains unknown. To provide the optimal time interval between hyaluronidase injections and HA filler reinjections. 6 Sprague-Dawley rats were injected with single monophasic HA filler. 1 week after injection, the injected sites were treated with hyaluronidase. Then, HA fillers were reinjected sequentially with differing time intervals from 30 minutes to 14 days. 1 hour after the reinjection of the last HA filler, all injection sites were excised for histologic evaluation. 3 hours after reinjection of HA filler, the appearance of filler material became evident again, retaining its shape and volume. 6 hours after reinjection, the filler materials restored almost its original volume and there were no significant differences from the positive control. Our data suggest that the hyaluronidase loses its effect in dermis and subcutaneous tissue within 3-6 hours after the injection and successful engraftment of reinjected HA filler can be accomplished 6 hours after the injection.

  10. Enrofloxacin sorption on smectite clays: effects of pH, cations, and humic acid.

    PubMed

    Yan, Wei; Hu, Shan; Jing, Chuanyong

    2012-04-15

    Enrofloxacin (ENR) occurs widely in natural waters because of its extensive use as a veterinary chemotherapeutic agent. To improve our understanding of the interaction of this emerging contaminant with soils and sediments, sorption of ENR on homoionic smectites and kaolinite was studied as a function of pH, ionic strength, exchangeable cations, and humic acid concentration. Batch experiments and in situ ATR-FTIR analysis suggested multiple sorption mechanisms. Cation exchange was a major contributor to the sorption of cationic ENR species on smectite. The decreased ENR sorption with increasing ionic strength indicated the formation of outer-sphere complexes. Exchangeable cations significantly influenced the sorption capacity, and the observed order was Cshumic acid had a negligible contribution to the interlayer intercalation. The results of this study provide new insight into the molecular mechanisms of ENR sorption on clay minerals. Copyright © 2012 Elsevier Inc. All rights reserved.

  11. Hybrid Processes Combining Photocatalysis and Ceramic Membrane Filtration for Degradation of Humic Acids in Saline Water.

    PubMed

    Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

    2016-03-01

    This study explored the combined effects of photocatalysis with ceramic membrane filtration for the removal of humic acid in the presence of salt; to simulate saline wastewater conditions. The effects of operating parameters, such as salinity and TiO₂ concentration on permeate fluxes, total organic carbon (TOC), and UV absorbance removal, were investigated. The interaction between the humic acids and TiO₂ photocatalyst played an important role in the observed flux change during ceramic membrane filtration. The results for this hybrid system showed that the TOC removal was more than 70% for both without NaCl and with the 500 ppm NaCl concentration, and 62% and 66% for 1000 and 2000 ppm NaCl concentrations. The reduction in UV absorbance was more complete in the absence of NaCl compared to the presence of NaCl. The operation of the integrated photoreactor-ceramic membrane filter over five repeat cycles is described. It can be concluded that the overall removal performance of the hybrid system was influenced by the presence of salts, as salt leads to agglomeration of TiO₂ particles by suppressing the stabilising effects of electrostatic repulsion and thereby reduces the effective surface contact between the pollutant and the photocatalyst.

  12. Hybrid Processes Combining Photocatalysis and Ceramic Membrane Filtration for Degradation of Humic Acids in Saline Water

    PubMed Central

    Song, Lili; Zhu, Bo; Gray, Stephen; Duke, Mikel; Muthukumaran, Shobha

    2016-01-01

    This study explored the combined effects of photocatalysis with ceramic membrane filtration for the removal of humic acid in the presence of salt; to simulate saline wastewater conditions. The effects of operating parameters, such as salinity and TiO2 concentration on permeate fluxes, total organic carbon (TOC), and UV absorbance removal, were investigated. The interaction between the humic acids and TiO2 photocatalyst played an important role in the observed flux change during ceramic membrane filtration. The results for this hybrid system showed that the TOC removal was more than 70% for both without NaCl and with the 500 ppm NaCl concentration, and 62% and 66% for 1000 and 2000 ppm NaCl concentrations. The reduction in UV absorbance was more complete in the absence of NaCl compared to the presence of NaCl. The operation of the integrated photoreactor-ceramic membrane filter over five repeat cycles is described. It can be concluded that the overall removal performance of the hybrid system was influenced by the presence of salts, as salt leads to agglomeration of TiO2 particles by suppressing the stabilising effects of electrostatic repulsion and thereby reduces the effective surface contact between the pollutant and the photocatalyst. PMID:26938568

  13. Mechanism study of humic acid functional groups for Cr(VI) retention: Two-dimensional FTIR and 13C CP/MAS NMR correlation spectroscopic analysis.

    PubMed

    Zhang, Jia; Chen, Linpeng; Yin, Huilin; Jin, Song; Liu, Fei; Chen, Honghan

    2017-06-01

    Undissolved humic acid (HA) is known to substantially effect the migration and transformation of hexavalent chromium [Cr(VI)] in soils. The mechanisms of Cr(VI) retention in soils by undissolved HA have been reported; however, past studies are inconclusive about the types of HA functional groups that are involved in Cr(VI) retention and the retention mechanisms. Utilizing a two-dimensional correlation spectroscopy (2DCOS) analysis for FTIR and 13 C CP/MAS NMR, this study investigated the variations of HA function groups and molecular structures after reactions with aqueous Cr(VI) under different pH conditions. Based on the changing sequence of functional groups interpreted from the 2DCOS results, a four-step mechanism for Cr(VI) retention was determined as follows: (1) electrostatic adsorption of Cr(VI) to HA surface, (2) complexation of adsorbed Cr(VI) by carboxyl and ester, (3) reduction of complexed Cr(VI) to Cr(III) by phenol and polysaccharide, and (4) complexation of reduced Cr(III) by carboxylic groups. These functional groups that are involved in Cr(VI) retention were determined to occur in aromatic domains. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Influence of extreme concentrations of hydrophilic pore-former on reinforced polyethersulfone ultrafiltration membranes for reduction of humic acid fouling.

    PubMed

    Son, Moon; Kim, Hayoung; Jung, Junhyeok; Jo, Sungsoo; Choi, Heechul

    2017-07-01

    To address the issue of membrane fouling by ubiquitous humic substances, a hydrophilic pore-former-blended polyethersulfone UF membrane was successfully synthesized via the phase inversion method. For the first time, extremely high concentrations of polyvinylpyrrolidone (PVP), up to 20 wt%, were tested as the hydrophilic pore-former in order to determine the optimum concentration for humic acid fouling. Intrinsic membrane parameters such as permeability and selectivity were evaluated using a cross-flow UF filtration setup. Interestingly, as little as 1 wt% added PVP can significantly improve membrane permeability. That tiny amount of added PVP increased membrane flux to 1107 L/m 2 h·bar from zero flux, with over 90% rejection of humic acid. In addition, pure water permeation increased to over 2400 L/m 2 h·bar without sacrificing humic acid rejection (around 90%) when 10 wt% PVP was added; pure water permeation decreased to around 1000 L/m 2 h·bar as added PVP was increased to 20 wt%. The order of water flux increased with the amount of added PVP up to 20 wt% during humic acid fouling while maintaining membrane selectivity. However, the membrane with 10 wt% added PVP showed the best fouling resistance in terms of flux recovery ratio (98%), total flux loss, reversible fouling ratio, and irreversible fouling ratio. Therefore, the addition of 10 wt% PVP is recommended considering cleaning efficiency and the moderately high flux during humic acid fouling for field operation in wastewater reclamation and water treatment processes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties.

    PubMed

    Boguta, Patrycja; Sokołowska, Zofia

    2016-01-01

    The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic

  16. Interactions of Zn(II) Ions with Humic Acids Isolated from Various Type of Soils. Effect of pH, Zn Concentrations and Humic Acids Chemical Properties

    PubMed Central

    Boguta, Patrycja; Sokołowska, Zofia

    2016-01-01

    The main aim of this study was the analysis of the interaction between humic acids (HAs) from different soils and Zn(II) ions at wide concentration ranges and at two different pHs, 5 and 7, by using fluorescence and FTIR spectroscopy, as well as potentiometric measurements. The presence of a few areas of HAs structures responsible for Zn(II) complexing was revealed. Complexation at α-sites (low humified structures of low-molecular weight and aromatic polycondensation) and β-sites (weakly humified structures) was stronger at pH 7 than 5. This trend was not observed for γ-sites (structures with linearly-condensed aromatic rings, unsaturated bonds and large molecular weight). The amount of metal complexed at pH5 and 7 by α and γ-structures increased with a decrease in humification and aromaticity of HAs, contrary to β-areas where complexation increased with increasing content of carboxylic groups. The stability of complexes was higher at pH 7 and was the highest for γ-structures. At pH 5, stability decreased with C/N increase for α-areas and -COOH content increase for β-sites; stability increased with humification decrease for γ-structures. The stability of complexes at α and β-areas at pH 7 decreased with a drop in HAs humification. FTIR spectra at pH 5 revealed that the most-humified HAs tended to cause bidentate bridging coordination, while in the case of the least-humified HAs, Zn caused bidentate bridging coordination at low Zn additions and bidentate chelation at the highest Zn concentrations. Low Zn doses at pH 7 caused formation of unidentate complexes while higher Zn doses caused bidentate bridging. Such processes were noticed for HAs characterized by high oxidation degree and high oxygen functional group content; where these were low, HAs displayed bidentate bridging or even bidentate chelation. To summarize, the above studies have showed significant impact of Zn concentration, pH and some properties of HAs on complexation reactions of humic

  17. Dispersion and stability of bare hematite nanoparticles: effect of dispersion tools, nanoparticle concentration, humic acid and ionic strength

    PubMed Central

    Dickson, Dionne; Liu, Guangliang; Li, Chenzhong; Tachiev, Georgio; Cai, Yong

    2012-01-01

    The aggregation and sedimentation of iron oxide nanoparticles (IONPs) can significantly affect the mobility and reactivity of IONPs and subsequently influence the interaction between IONPs and environmental contaminants. Dispersing bare IONPs into a stable suspension within nanoscale range is an important step for studying the interaction of IONPs with contaminants (e.g., toxic metals). In this study, different techniques to disperse bare IONPs (vortex, bath sonication and probe ultrasonication) and the effects of important environmental factors such as dissolved organic matter and ionic strength on the stability of IONPs dispersions were investigated. Vortex minimally dispersed IONPs with hydrodynamic diameter outside the “nanosize range” (698–2400nm). Similar to vortex, bath sonication could not disperse IONPs efficiently. Probe ultrasonication was more effective at dispersing IONPs (50% or more) with hydrodynamic diameters ranging from 120–140 nm with minimal changes in size and sedimentation of IONPs for a prolonged period of time. Over the course of 168 hours, considerable amounts of IONPs remained dispersed in the presence and absence of low ionic strength (0.1 mM of NaCl) and 100 mg/L of humic acid (HA). These results indicate that IONPs can be broken down efficiently into “nanosize range” by probe ultrasonication and a degree of stability can be achieved without the use of synthetic modifiers to enhance colloidal stability. This dispersion tool could be used to develop a laboratory method to study the adsorption mechanism between dispersed bare IONPs and toxic contaminants. PMID:22289174

  18. Humic acid coated Fe3O4 magnetic nanoparticles as highly efficient Fenton-like catalyst for complete mineralization of sulfathiazole.

    PubMed

    Niu, Hongyun; Zhang, Di; Zhang, Shengxiao; Zhang, Xiaole; Meng, Zhaofu; Cai, Yaqi

    2011-06-15

    Humic acid coated Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4)/HA) were prepared for the removal of sulfathiazole from aqueous media. Fe(3)O(4)/HA exhibited high activity to produce hydroxyl (OH) radicals through catalytic decomposition of H(2)O(2). The degradation of sulfathiazole was strongly temperature-dependent and favored in acidic solution. The catalytic rate was increased with Fe(3)O(4)/HA dosage and H(2)O(2) concentration. When 3 g L(-1) of Fe(3)O(4)/HA and 0.39 M of H(2)O(2) were introduced to the aqueous solution, most sulfathiazole was degraded within 1h, and >90% of total organic carbon (TOC) were removed in the reaction period (6h). The major final products were identified as environmentally friendly ions or inorganic molecules (SO(4)(2-), CO(2), and N(2)). The corresponding degradation rate (k) of sulfathiazole and TOC was 0.034 and 0.0048 min(-1), respectively. However, when 3 g L(-1) of bare Fe(3)O(4) were used as catalyst, only 54% of TOC was eliminated, and SO(4)(2-) was not detected within 6h. The corresponding degradation rate for sulfathiazole and TOC was 0.01 and 0.0016 min(-1), respectively. The high catalytic ability of Fe(3)O(4)/HA may be caused by the electron transfer among the complexed Fe(II)-HA or Fe(III)-HA, leading to rapid regeneration of Fe(II) species and production of OH radicals. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Effect of soil application of humic acid on nutrients uptake, essential oil and chemical compositions of garden thyme (Thymus vulgaris L.) under greenhouse conditions.

    PubMed

    Noroozisharaf, Alireza; Kaviani, Maryam

    2018-05-01

    Humic acid is natural biological organic, which has a high effect on plant growth and quality. However, the mechanisms of the promoting effect of humic acid on the volatile composition were rarely reported. In this study, the effects of soil application of humic acid on the chemical composition and nutrients uptake of Thymus vulgaris were investigated. Treatments comprised 0, 50, 75 and 100 g m -2 . Essential oil was extracted by hydrodistillation and analyzed using GC-MS and GC-FID. Essential oil content was enhanced by increase of the humic acid level and its content ranged from 0.8% (control) to 2.0% (75 g m -2 ). Thirty-two volatile compounds were identified and these compounds were considerably affected by humic acid. The highest percentage of thymol (74.15%), carvacrol (6.20%), p -cymene (4.24%), borneol (3.42%), trans -caryophyllene (1.70%) and cis -sabinene hydrate (1.35%) as major compounds were observed in T. vulgaris under 100 g m -2 humic acid. There was a linear relationship ( R 2  = 97%) between humic acid levels and thymol as a major compound. The oils were dominated by oxygenated monoterpenes followed by monoterpene hydrocarbons and sesquiterpene hydrocarbons. Based on the path coefficient analysis, the highest direct effects on essential oil content were observed in monoterpene esters (3.465) and oxygenated sesquiterpenes (3.146). The humic acid application also enhanced the uptake of N, P, K, Mg and Fe in garden thyme. The highest N (2.42%), P (0.75%), K (2.63%), Mg (0.23%) and Fe (1436.58 ppm) were observed in medium supplemented with 100 g m -2 humic acid. In all, the utilization of humic acid could positively change nutrients uptake, essential oil content and its major constituents in T. vulgaris .

  20. 3D bioprinting of methacrylated hyaluronic acid (MeHA) hydrogel with intrinsic osteogenicity.

    PubMed

    Poldervaart, Michelle T; Goversen, Birgit; de Ruijter, Mylene; Abbadessa, Anna; Melchels, Ferry P W; Öner, F Cumhur; Dhert, Wouter J A; Vermonden, Tina; Alblas, Jacqueline

    2017-01-01

    In bone regenerative medicine there is a need for suitable bone substitutes. Hydrogels have excellent biocompatible and biodegradable characteristics, but their visco-elastic properties limit their applicability, especially with respect to 3D bioprinting. In this study, we modified the naturally occurring extracellular matrix glycosaminoglycan hyaluronic acid (HA), in order to yield photo-crosslinkable hydrogels with increased mechanical stiffness and long-term stability, and with minimal decrease in cytocompatibility. Application of these tailor-made methacrylated hyaluronic acid (MeHA) gels for bone tissue engineering and 3D bioprinting was the subject of investigation. Visco-elastic properties of MeHA gels, measured by rheology and dynamic mechanical analysis, showed that irradiation of the hydrogels with UV light led to increased storage moduli and elastic moduli, indicating increasing gel rigidity. Subsequently, human bone marrow derived mesenchymal stromal cells (MSCs) were incorporated into MeHA hydrogels, and cell viability remained 64.4% after 21 days of culture. Osteogenic differentiation of MSCs occurred spontaneously in hydrogels with high concentrations of MeHA polymer, in absence of additional osteogenic stimuli. Addition of bone morphogenetic protein-2 (BMP-2) to the culture medium further increased osteogenic differentiation, as evidenced by increased matrix mineralisation. MeHA hydrogels demonstrated to be suitable for 3D bioprinting, and were printed into porous and anatomically shaped scaffolds. Taken together, photosensitive MeHA-based hydrogels fulfilled our criteria for cellular bioprinted bone constructs within a narrow window of concentration.

  1. 3D bioprinting of methacrylated hyaluronic acid (MeHA) hydrogel with intrinsic osteogenicity

    PubMed Central

    Poldervaart, Michelle T.; Goversen, Birgit; de Ruijter, Mylene; Abbadessa, Anna; Melchels, Ferry P. W.; Öner, F. Cumhur; Dhert, Wouter J. A.; Vermonden, Tina

    2017-01-01

    In bone regenerative medicine there is a need for suitable bone substitutes. Hydrogels have excellent biocompatible and biodegradable characteristics, but their visco-elastic properties limit their applicability, especially with respect to 3D bioprinting. In this study, we modified the naturally occurring extracellular matrix glycosaminoglycan hyaluronic acid (HA), in order to yield photo-crosslinkable hydrogels with increased mechanical stiffness and long-term stability, and with minimal decrease in cytocompatibility. Application of these tailor-made methacrylated hyaluronic acid (MeHA) gels for bone tissue engineering and 3D bioprinting was the subject of investigation. Visco-elastic properties of MeHA gels, measured by rheology and dynamic mechanical analysis, showed that irradiation of the hydrogels with UV light led to increased storage moduli and elastic moduli, indicating increasing gel rigidity. Subsequently, human bone marrow derived mesenchymal stromal cells (MSCs) were incorporated into MeHA hydrogels, and cell viability remained 64.4% after 21 days of culture. Osteogenic differentiation of MSCs occurred spontaneously in hydrogels with high concentrations of MeHA polymer, in absence of additional osteogenic stimuli. Addition of bone morphogenetic protein-2 (BMP-2) to the culture medium further increased osteogenic differentiation, as evidenced by increased matrix mineralisation. MeHA hydrogels demonstrated to be suitable for 3D bioprinting, and were printed into porous and anatomically shaped scaffolds. Taken together, photosensitive MeHA-based hydrogels fulfilled our criteria for cellular bioprinted bone constructs within a narrow window of concentration. PMID:28586346

  2. Effects of Cu2+ and humic acids on degradation and fate of TBBPA in pure culture of Pseudomonas sp. strain CDT.

    PubMed

    Ma, Yini; Zhao, Yingying; Wang, Yongfeng; Li, Xiangzhen; Sun, Feifei; Corvini, Phillippe Francois-Xavier; Ji, Rong

    2017-12-01

    Soil contamination with tetrabromobisphenol A (TBBPA) has caused great concerns; however, the presence of heavy metals and soil organic matter on the biodegradation of TBBPA is still unclear. We isolated Pseudomonas sp. strain CDT, a TBBPA-degrading bacterium, from activated sludge and incubated it with 14 C-labeled TBBPA for 87 days in the absence and presence of Cu 2+ and humic acids (HA). TBBPA was degraded to organic-solvent extractable (59.4%±2.2%) and non-extractable (25.1%±1.3%) metabolites, mineralized to CO 2 (4.8%±0.8%), and assimilated into cells (10.6%±0.9%) at the end of incubation. When Cu 2+ was present, the transformation of extractable metabolites into non-extractable metabolites and mineralization were inhibited, possibly due to the toxicity of Cu 2+ to cells. HA significantly inhibited both dissipation and mineralization of TBBPA and altered the fate of TBBPA in the culture by formation of HA-bound residues that amounted to 22.1%±3.7% of the transformed TBBPA. The inhibition from HA was attributed to adsorption of TBBPA and formation of bound residues with HA via reaction of reactive metabolites with HA molecules, which decreased bioavailability of TBBPA and metabolites in the culture. When Cu 2+ and HA were both present, Cu 2+ significantly promoted the HA inhibition on TBBPA dissipation but not on metabolite degradation. The results provide insights into individual and interactive effects of Cu 2+ and soil organic matter on the biotransformation of TBBPA and indicate that soil organic matter plays an essential role in determining the fate of organic pollutants in soil and mitigating heavy metal toxicity. Copyright © 2017. Published by Elsevier B.V.

  3. The root application of a purified leonardite humic acid modifies the transcriptional regulation of the main physiological root responses to Fe deficiency in Fe-sufficient cucumber plants.

    PubMed

    Aguirre, Elena; Elena, Aguirre; Leménager, Diane; Diane, Leménager; Bacaicoa, Eva; Eva, Bacaicoa; Fuentes, Marta; Marta, Fuentes; Baigorri, Roberto; Roberto, Baigorri; Zamarreño, Angel Ma; García-Mina, José Ma

    2009-03-01

    The aim of this study is to investigate the effect of a well-characterized purified humic acid (non-measurable concentrations of the main plant hormones were detected) on the transcriptional regulation of the principal molecular agents involved in iron assimilation. To this end, non-deficient cucumber plants were treated with different concentrations of a purified humic acid (PHA) (2, 5, 100 and 250 mg of organic carbonL(-1)) and harvested 4, 24, 48, 76 and 92 h from the onset of the treatment. At harvest times, the mRNA transcript accumulation of CsFRO1 encoding for Fe(III) chelate-reductase (EC 1.16.1.7); CsHa1 and CsHa2 encoding for plasma membrane H+-ATPase (EC 3.6.3.6); and CsIRT1 encoding for Fe(II) high-affinity transporter, was quantified by real-time RT-PCR. Meanwhile, the respective enzyme activity of the Fe(III) chelate-reductase and plasma membrane H+-ATPase was also investigated. The results obtained indicated that PHA root treatments affected the regulation of the expression of the studied genes, but this effect was transient and differed (up-regulation or down-regulation) depending on the genes studied. Thus, principally the higher doses of PHA caused a transient increase in the expression of the CsHa2 isoform for 24 and 48 h whereas the CsHa1 isoform was unaffected or down-regulated. These effects were accompanied by an increase in the plasma membrane H+-ATPase activity for 4, 48 and 96 h. Likewise, PHA root treatments (principally the higher doses) up-regulated CsFRO1 and CsIRT1 expression for 48 and 72 h; whereas these genes were down-regulated by PHA for 96 h. These effects were associated with an increase in the Fe(III) chelate-reductase activity for 72 h. These effects were not associated with a significant decrease in the Fe root or leaf concentrations, although an eventual effect on the Fe root assimilation pattern cannot be ruled out. These results stress the close relationships between the effects of humic substances on plant development

  4. Proton and metal ion binding to natural organic polyelectrolytes-II. Preliminary investigation with a peat and a humic acid

    USGS Publications Warehouse

    Marinsky, J.A.; Reddy, M.M.

    1984-01-01

    We summarize here experimental studies of proton and metal ion binding to a peat and a humic acid. Data analysis is based on a unified physico-chemical model for reaction of simple ions with polyelectrolytes employing a modified Henderson-Hasselbalch equation. Peat exhibited an apparent intrinsic acid dissociation constant of 10-4.05, and an apparent intrinsic metal ion binding constant of: 400 for cadmium ion; 600 for zinc ion; 4000 for copper ion; 20000 for lead ion. A humic acid was found to have an apparent intrinsic proton binding constant of 10-2.6. Copper ion binding to this humic acid sample occurred at two types of sites. The first site exhibited reaction characteristics which were independent of solution pH and required the interaction of two ligands on the humic acid matrix to simultaneously complex with each copper ion. The second complex species is assumed to be a simple monodentate copper ion-carboxylate species with a stability constant of 18. ?? 1984.

  5. Compost-derived humic acids as regulators for reductive degradation of nitrobenzene.

    PubMed

    Yuan, Ying; Xi, Beidou; He, Xiaosong; Tan, Wenbing; Gao, Rutai; Zhang, Hui; Yang, Chao; Zhao, Xinyu; Huang, Caihong; Li, Dan

    2017-10-05

    Nitrobenzene (NB) is a major class of contaminants in soil and groundwater. The current methods involved in the reductive degradation of NB suffer either cost-ineffective or slow conversion rate. Here, we investigated the mechanisms regarding compost-derived humic acids (HAs) as cost-effective regulators to enhance the reduction of NB to aniline (AN). Our results show that the compost-derived HAs, which have been reduced by a Pd-H 2 catalytic system, were able to reduce NB to AN, and their redox properties were the main factors governing the reduction of NB to AN. The decreasing reduction of NB was mainly caused by the decreasing phenol content of compost-derived HAs during composting. In addition, the results reveal that the increase in the generation content of AN was mainly attributed to the increase in the quinones, aromaticity and humic-like components of compost-derived HAs. The findings demonstrate that the HAs derived from compost are effective regulators to enhance the reduction of NB to AN, and that they exert a bright application prospect for the remediation of the NB-contaminated soil. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Sorption of estrogens and pesticides from aqueous solution by a humic acid and raw and processed plant materials

    NASA Astrophysics Data System (ADS)

    Loffredo, Elisabetta; Taskin, Eren

    2016-04-01

    The huge number of organic contaminants released in water as a consequence of anthropogenic activities have detrimental effects to environmental systems and human health. Industrial products and byproducts, pharmaceuticals, pesticides, detergents and so on impose increasing costs for wastewater decontamination. Adsorption techniques can be successfully used for the treatment of wastewaters to remove contaminants of various nature. Humic acids (HA) have well-known adsorptive capacities towards hydrophilic and, especially, hydrophobic compounds. In the recent years, alternative low-cost adsorbents, especially originated from agricultural wastes and food industries residues, such as wood chips, almond and coconut shells, peanut and rice husks, are under investigation. Biochar is also considered a promising and relatively low-cost adsorbent, even if there are still knowledge gaps about the influence of feedstock type, pyrolysis conditions, physical and chemical properties on its potential and safe use. In the present work, a HA from a green compost was used along with three other materials of plant origin to remove two estrogens, 4-tert-octylphenol and 17-β-estradiol, and two pesticides, carbaryl and fenuron, from an aqueous solution. The four molecules were spiked in water each at a concentration of 1 mg L-1. The materials were: a biochar obtained from 100% red spruce pellet pyrolysed at 550 °C, spent coffee grounds and spent tea leaves. Kinetics curves and adsorption isotherms studies were performed using a batch equilibrium method. Adsorption data obtained for each compound were fitted to a linear equation and non-linear Freundlich and Langmuir models. Kinetics data of the four compounds onto all adsorbents showed an initial very rapid adsorption which was completed in few hours when it reached equilibrium. The two estrogens were adsorbed onto all materials more quickly than the two less hydrophobic pesticides. Significant differences among adsorbents and the

  7. Developmental toxicity of Japanese medaka embryos by silver nanoparticles and released ions in the presence of humic acid.

    PubMed

    Kim, Jun Y; Kim, Ki-Tae; Lee, Byeong G; Lim, Byung J; Kim, Sang D

    2013-06-01

    The final destination point of nanoparticles is the environment, where they remain a long period; therefore, a deep understanding of the relationship between nanoparticles and the environmental factors is required. Japanese medaka embryos were exposed to two differently prepared AgNPs: freshly prepared AgNPs and aged AgNPs. With these two AgNP preparations, we studied the impacts of humic acid in terms of embryonic toxicity, as well as the behavior of AgNPs. Aged AgNPs exhibited a lower lethal concentration (LC50) value (1.44mg/L) compared to fresh AgNPs (3.53mg/L) through 96h acute toxicity tests, due to the release of silver ions, as confirmed by kinetic analysis. The presence of humic acids considerably reduced the toxicity of aged AgNPs due to complexation with silver ions. Agglomeration, induced by interactions with humic acid, might reduce the bioavailability of AgNPs to Japanese medaka embryos. This study demonstrates that aged AgNPs releasing more silver ions are more toxic than fresh AgNPs, and humic acids play a role in reducing the toxicity of aged AgNPs. Copyright © 2013 Elsevier Inc. All rights reserved.

  8. Interaction of fullerene (C60) nanoparticles with humic acid and alginate coated silica surfaces: measurements, mechanisms, and environmental implications.

    PubMed

    Chen, Kai Loon; Elimelech, Menachem

    2008-10-15

    The deposition kinetics of fullerene (C60) nanoparticles onto bare silica surfaces and surfaces precoated with humic acid and alginate are investigated over a range of monovalent (NaCI) and divalent (CaCl2) salt concentrations using a quartz crystal microbalance. Because simultaneous aggregation of the fullerene nanoparticles occurs, especially at higher electrolyte concentrations, we normalize the observed deposition rates by the corresponding favorable (transport-limited) deposition rates to obtain the attachment efficiencies, alpha. The deposition kinetics of fullerene nanoparticles onto bare silica surfaces are shown to be controlled by electrostatic interactions and van der Waals attraction, consistent with the classical particle deposition behavior where both favorable and unfavorable deposition regimes are observed. The presence of dissolved humic acid and alginate in solution leads to significantly slower deposition kinetics due to steric repulsion. Precoating the silica surfaces with humic acid and alginate exerts similar steric stabilization in the presence of NaCl. In the presence of CaCl2, the deposition kinetics of fullerene nanoparticles onto both humic acid- and alginate-coated surfaces are relatively high, even at relatively low (0.3 mM) calcium concentration. This behavior is attributed to the macromolecules undergoing complex formation with calcium ions, which reduces the charge and steric influences of the adsorbed macromolecular layers.

  9. Mineral phosphate solubilization by Streptomyces sp. CTM396 involves the excretion of gluconic acid and is stimulated by humic acids.

    PubMed

    Farhat, Mounira Ben; Boukhris, Ines; Chouayekh, Hichem

    2015-03-01

    The actinomycetes isolates (128) which were taken from agricultural soil samples and collected near a rock phosphate processing unit were screened for mineral phosphate-solubilizing (MPS) ability. A significant MPS activity was observed for 30 isolates on various phosphate sources when grown in the National Botanical Research Institute's phosphate broth. CTM396 and CTM397 strains which showed the highest MPS abilities were identified by 16S rDNA sequencing as members of the genus Streptomyces. Their MPS activity was proved to be concomitant with a drop in pH due to the secretion of gluconic acid (GA). This was correlated with the simultaneous detection by PCR of genes gdh [encoding the glucose dehydrogenase (GDH) responsible for GA production from glucose] and pqq (involved in biosynthesis of the pyrroloquinoline quinone cofactor of GDH), as well as the highlighting of GHD enzyme activity, for the first time in a Streptomyces sp. strain producing GA. Furthermore, the 0.05% of humic acids proved to have a stimulatory effect on the growth and the ability of CTM396 to solubilize Gafsa rock phosphate. According to this study, it is possible to use humic acids and Gafsa rock phosphate in association with spores of ad hoc Streptomyces strains as natural and efficient amendments to improve plant growth with no need of costly and pollutant transformation of Gafsa rock phosphate. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  10. Evaluating the efficiency of humic acid to remove micro-organisms from denture base material.

    PubMed

    Meriç, Gökçe; Güvenir, Meryem; Süer, Kaya

    2016-09-01

    To evaluate the efficiency of humic acid substances on removing micro-organisms from denture base materials. Old denture wearer needs effective, easy-use and safe denture-cleaning material. Square-shaped, heat-polymerised acrylic resin specimens (n = 550) were prepared and divided into five groups (n = 110 for each) corresponding to the microbial contamination (Candida albicans, Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, Pseudomonas aeruginosa). Contaminated specimens were randomly assigned to the application of five different denture-cleaning agents as follows (n = 20 for each): Kloroben, Corsodyl, Steradent, Corega, experimental solution with humic acid. Ten specimens were assessed as an experimental control carried out simultaneously for the treatment groups for each micro-organism. It was divided into two groups: negative control and positive control (n = 5 for each). All acrylic specimens were incubated 37°C for 24 h (for bacterial strains) and 37°C for 48 h (for yeast strains). After incubation period, all brain-heart infusion broths (BHI) which contain disinfectant acrylic specimens were cultured on 5% sheep blood agar (for bacteria) and Sabouraud dextrose agar (SDA) for yeast using loop. The numbers of colony-forming units per millilitre (CFU/ml) were calculated. The results were analysed by Mann-Whitney U-test and Kruskal-Wallis tests (p = 0.05). Corsodyl and Kloroben completely eliminated the adherence of all investigated micro-organisms (100%) and showed the highest removal activity compared with other cleaning agents (p < 0.05). There was no statistically significant difference between Corsodyl and Kloroben (p ≥ 0.05), and there was no statistically significant difference between Corega, Steradent and experimental solution (p ≥ 0.05). Humic acid could be used as an alternative 'natural' solution for denture-cleaning agent. © 2014 John Wiley & Sons A/S and The Gerodontology Association. Published by John Wiley

  11. Influence of natural humic acids and synthetic phenolic polymers on fibrinolysis

    NASA Astrophysics Data System (ADS)

    Klöcking, Hans-Peter

    The influence of synthetic and natural phenolic polymers on the release of plasminogen activator was studied in an isolated, perfused, vascular preparation (pig ear). Of the tested synthetic phenolic polymers, the oxidation products of caffeic acid (KOP) and 3,4-dihydroxyphenylacetic acid (3,4-DHPOP), at a concentration of 50 µg/ml perfusate, were able to increase the plasminogen activator activity by 70%. The oxidation products of chlorogenic acid (CHOP), hydrocaffeic acid (HYKOP), pyrogallol (PYROP) and gallic acid (GALOP), at the same concentration, exerted no influence on the release of plasminogen activator. Of the naturally occurring humic acids, the influence of sodium humate was within the same order of magnitude as KOP and 3,4-DHPOP. Ammonium humate was able to increase the plasminogen activator release only at a concentration of 100 µg/ml perfusate. In rats, the t-PA activity increased after i.v. application of 10 mg/kg of KOP, Na-HS or NH4-HS.

  12. 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.

  13. Forces of interactions between bare and polymer-coated iron and silica: effect of pH, ionic strength, and humic acids.

    PubMed

    Pensini, Erica; Sleep, Brent E; Yip, Christopher M; O'Carroll, Denis

    2012-12-18

    The interactions between a silica substrate and iron particles were investigated using atomic force microscopy-based force spectroscopy (AFM). The micrometer- and nanosized iron particles employed were either bare or coated with carboxymethyl cellulose (CMC), a polymer utilized to stabilize iron particle suspensions. The effect of water chemistry on the forces of interaction was probed by varying ionic strength (with 100 mM NaCl and 100 mM CaCl₂) or pH (4, 5.5, and 8) or by introducing 10 mg/L of humic acids (HA). When particles were uncoated, the forces upon approach between silica and iron were attractive at pH 4 and 5.5 and in 100 mM CaCl₂ at pH 8, but they were negligible in 100 mM NaCl buffered to pH 8 and repulsive in water buffered to pH 8 and in HA solutions. HA produced electrosteric repulsion between iron particles and silica, likely due to its sorption to iron particles. HA sorption to silica was excluded on the basis of experiments conducted with a quartz-crystal microbalance with dissipation monitoring. Repulsion with CMC-coated iron was attributed to electrosteric forces, which were damped at high ionic strength. An extended DLVO model and a modified version of Ohshima's theory were successfully utilized to model AFM data.

  14. Effect of humic acids on intestinal viscosity, leaky gut and ammonia excretion in a 24 hr feed restriction model to induce intestinal permeability in broiler chickens.

    PubMed

    Maguey-Gonzalez, Jesús A; Michel, Matias A; Baxter, Mikayla F A; Tellez, Guillermo; Moore, Philip A; Solis-Cruz, Bruno; Hernández-Patlan, Daniel; Merino-Guzman, Rubén; Hernandez-Velasco, Xochitl; Latorre, Juan D; Hargis, Billy M; Gomez-Rosales, Sergio; Tellez-Isaias, Guillermo

    2018-04-30

    The purpose of this study was to evaluate the effect of humic acids (HA) on intestinal viscosity, leaky gut and ammonia excretion in a 24 hr feed restriction (FR) model to induce intestinal permeability in chickens. One-day-old male Cobb-Vantress broilers were randomly allocated to one of two groups (n = 25 chickens), with or without 0.2% of isolated HA from worm-compost, and placed in brooder batteries. Chicks had ad libitum access to water and feed for 14 days. Intestinal permeability was induced by 24 hr FR starting at 14 days. At 15 days of age, chickens in both groups were given an appropriate dose of fluorescein isothiocyanate dextran (FITC-d) by oral gavage. Intestine and liver samples were also collected to evaluate viscosity and bacterial translocation (BT), respectively. An increase (p < .05) in intestinal viscosity was observed in the experimental group consuming 0.2% of HA and was confirmed in a published in vitro digestion model that simulates the chemical and physical conditions of the crop, proventriculus and intestine of chickens. Furthermore, the treated group also showed a significant reduction in FITC-d, liver BT and ammonia in the manure. These results suggest that HA have a positive impact in intestinal integrity in chickens. © 2018 Japanese Society of Animal Science.

  15. Role of bovine serum albumin and humic acid in the interaction between SiO2 nanoparticles and model cell membranes.

    PubMed

    Wei, Xiaoran; Qu, Xiaolei; Ding, Lei; Hu, Jingtian; Jiang, Wei

    2016-12-01

    Silica nanoparticles (SiO 2 NPs) can cause health hazard after their release into the environment. Adsorption of natural organic matter and biomolecules on SiO 2 NPs alters their surface properties and cytotoxicity. In this study, SiO 2 NPs were treated by bovine serum albumin (BSA) and humic acid (HA) to study their effects on the integrity and fluidity of model cell membranes. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes in order to avoid the interference of cellular activities. The microscopic observation revealed that the BSA/HA treated (BSA-/HA-) SiO 2 NPs took more time to disrupt membrane than untreated-SiO 2 NPs, because BSA/HA adsorption covered the surface SiOH/SiO - groups and weakened the interaction between NPs and phospholipids. The deposition of SiO 2 NPs on membrane was monitored by a quartz crystal microbalance with dissipation (QCM-D). Untreated- and HA-SiO 2 NPs quickly disrupted the SUV layer on QCM-D sensor; BSA-SiO 2 NPs attached on the membranes but only caused slow vesicle disruption. Untreated-, BSA- and HA-SiO 2 NPs all caused the gelation of the positively-charged membrane, which was evaluated by the generalized polarity values. HA-SiO 2 NPs caused most serious gelation, and BSA-SiO 2 NPs caused the least. Our results demonstrate that the protein adsorption on SiO 2 NPs decreases the NP-induced membrane damage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Effect of humic acid and transition metal ions on the debromination of decabromodiphenyl by nano zero-valent iron: kinetics and mechanisms

    NASA Astrophysics Data System (ADS)

    Tan, Lei; Liang, Bin; Fang, Zhanqiang; Xie, Yingying; Tsang, Eric Pokeung

    2014-12-01

    E-waste sites are one of the main sources of the pollutant decabromodiphenyl ether (BDE209); contaminated farmland and water bodies urgently need to be remediated. As a potential in situ remediation technology, nano zero-valent iron (nZVI) technology effectively removes PBDEs. However, the humic acid (HA) and heavy metals in the contaminated sites affect the remediation effects. In this study, we explored the influence of HA and transition metals on the removal of PBDEs by nZVI. The specific surface area and average size of the nZVI particles we prepared were 35 m2/g and 50-80 nm, respectively. The results showed that HA inhibited the removal of PBDEs; as the concentration of HA increased, its inhibitory effect intensified and the k obs decreased. However, the three metal ions (Cu2+, Co2+, and Ni2+) enhanced the removal of PBDEs. The enhancement effect was followed the order Ni2+ > Cu2+ > Co2+. As the concentration of metal ions increased, the promotion effect improved. The synergistic effect of HA and the metal ions was manifested in the combination of the inhibitory effect and the enhancement effect. The values of the first-order kinetic constants ( k obs) under the combined effect were between the values of the rate constants under the individual components. The inhibitory mechanism was the chemisorption of HA, i.e., the benzene carboxylic and phenolic hydroxyl groups in HA occupied the surfactant reactive sites of nZVI, thus inhibiting the removal of BDE209. The promotion mechanism of Cu2+, Co2+, and Ni2+ can be explained by their reduction to zero valence on the nZVI surface; furthermore, Ni2+ strongly affects the debromination and dehydrogenation of BDE209, leading to a stronger promotability than Cu2+or Co2+.

  17. Sonocatalytic degradation of humic acid by N-doped TiO2 nano-particle in aqueous solution.

    PubMed

    Kamani, Hossein; Nasseri, Simin; Khoobi, Mehdi; Nabizadeh Nodehi, Ramin; Mahvi, Amir Hossein

    2016-01-01

    Un-doped and N-doped TiO2 nano-particles with different nitrogen contents were successfully synthesized by a simple sol-gel method, and were characterized by X-ray diffraction, field emission scanning electron microscopy, Energy dispersive X-ray analysis and UV-visible diffuse reflectance spectra techniques. Then enhancement of sonocatalytic degradation of humic acid by un-doped and N-doped TiO2 nano-particles in aqueous environment was investigated. The effects of various parameters such as initial concentration of humic acid, N-doping, and the degradation kinetics were investigated. The results of characterization techniques affirmed that the synthesis of un-doped and N-doped TiO2 nano-particles was successful. Degradation of humic acid by using different nano-particles obeyed the first-order kinetic. Among various nano-particles, N-doped TiO2 with molar doping ratio of 6 % and band gap of 2.92 eV, exhibited the highest sonocatalytic degradation with an apparent-first-order rate constant of 1.56 × 10(-2) min(-1). The high degradation rate was associated with the lower band gap energy and well-formed anatase phase. The addition of nano-catalysts could enhance the degradation efficiency of humic acid as well as N-doped TiO2 with a molar ratio of 6 %N/Ti was found the best nano-catalyst among the investigated catalysts. The sonocatalytic degradation with nitrogen doped semiconductors could be a suitable oxidation process for removal of refractory pollutants such as humic acid from aqueous solution.

  18. Phototransformation of estrogens mediated by Mn(III), not by reactive oxygen species, in the presence of humic acids.

    PubMed

    Wang, Xinghao; Yao, Jiayi; Wang, Siyuan; Pan, Xiaoxue; Xiao, Ruiyang; Huang, Qingguo; Wang, Zunyao; Qu, Ruijuan

    2018-06-01

    Photodegradation of pollutants is classically explained by reaction with reactive oxygen species. However Mn(III) may also remove pollutants, but direct evidence is actually lacking. Here we investigated the role of soluble Mn(III) on phototransformation of four typical estrogens, namely estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2), in the presence of Mn(II) and humic acid. Conversion rates of 60.2%, 89.0%, 87.6%, and 80.2% were achieved for E1, E2, E3, and EE2, respectively, after 72 h visible light irradiation. A detailed quenching experiments revealed that soluble Mn(III), and not reactive oxygen species, was the oxidant responsible for estrogen removal. The determination of Mn(III) concentration provided direct proof of the role of Mn(III)-based oxidizers in the conversion of estrogens. Soluble Mn(III) can form complexes with humic acid, and about 6.51 μM of Mn(III)-humic acid was formed from 20 μM of Mn(II) in the presence of 5 mg/L of humic acid. Furthermore, product identification and theoretical computation demonstrated that estrogens are mainly converted into oligomers (dimers, trimers, tetramers, etc.) via a single-electron process. According to these results, the oxidation of Mn(II) to Mn(III) is initiated by superoxide ion (O 2 •- ) generated from dissolved oxygen in the presence of humic acid under visible light irradiation. The formed soluble Mn(III) strips the estrogens of a single electron to generate phenoxyl radicals, which undergo oligomerization, while leads to regeneration of Mn(II). Hence, the photochemical Mn(II)-Mn(III) redox cycling may significantly influence the fate and transformation of estrogens in waters. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Sorption of vapors of some organic liquids on soil humic acid and its relation to partitioning of organic compounds in soil organic matter

    USGS Publications Warehouse

    Chlou, G.T.; Kile, D.E.; Malcolm, R.L.

    1988-01-01

    Vapor sorption of water, ethanol, benzene, hexane, carbon tetrachloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, and 1,2-dibromoethane on (Sanhedron) soil humic acid has been determined at room temperature. Isotherms for all organic liquids are highly linear over a wide range of relative pressure (P/P??), characteristic of the partitioning (dissolution) of the organic compounds in soil humic acid. Polar liquids exhibit markedly greater sorption capacities on soil humic acid than relatively nonpolar liquids, in keeping with the polar nature of the soil humic acid as a partition medium. The limiting sorption (partition) capacities of relatively non-polar liquids are remarkably similar when expressed in terms of volumes per unit weight of soil humic acid. The soil humic acid is found to be about half as effective as soil organic matter in sorption of relatively nonpolar organic compounds. The nearly constant limiting sorption capacity for nonpolar organic liquids with soil humic acid on a volume-to-weight basis and its efficiency in sorption relative to soil organic matter provide a basis for predicting the approximate sorption (partition) coefficients of similar compounds in uptake by soil in aqueous systems.

  20. Isotherm modeling of organic activated bentonite and humic acid polymer used as mycotoxin adsorbents.

    PubMed

    Santos, R R; Vermeulen, S; Haritova, A; Fink-Gremmels, J

    2011-11-01

    The aim of the current study was to evaluate and compare two representative samples of different classes of adsorbents intended for use as feed additives in the prevention or reduction of the adverse effects exerted by mycotoxins, specifically ochratoxin A (OTA) and zearalenone (ZEN). The adsorbents, an organically activated bentonite (OAB) and a humic acid polymer (HAP), were tested in a common in vitro model with a pH course comparing the maximum pH changes that can be expected in the digestive system of a monogastric animal, i.e. pH 7.4 for the oral cavity, pH 3.0 for the stomach, and pH 8.4 for the intestines. In the first experiment, the concentration-dependent adsorbent capacity of OAB and HAB were tested using a fixed concentration of either mycotoxin. Thereafter, adsorption was evaluated applying different isotherms models, such as Freundlich, Langmuir, Brunauer-Emmett-Teller (BET) and Redlich-Peterson, to characterize the adsorption process as being either homo- or heterogeneous and representing either mono- or multilayer binding. At the recommended statutory level for the mycotoxins of 0.1 mg kg(-1) OTA and 0.5 mg kg(-1) ZEN, OAB showed an adsorbed capacity of >96% towards both mycotoxins, regardless of the pH. The HAP product was also able to absorb >96% of both mycotoxins at pH 3.0, but extensive desorption occurred at pH 8.4. Based on χ-square (χ(2)) values, Langmuir and Redlich-Peterson equations proved to be the best models to predict monolayer equilibrium sorption of OTA and ZEN onto the organically activated bentonite and the humic acid polymer. The applied methodology has a sufficient robustness to facilitate further comparative studies with different mycotoxin-adsorbing agents.

  1. Kinetics during the redox biotransformation of pollutants mediated by immobilized and soluble humic acids.

    PubMed

    Cervantes, Francisco J; Martínez, Claudia M; Gonzalez-Estrella, Jorge; Márquez, Arturo; Arriaga, Sonia

    2013-03-01

    The aim of this study was to elucidate the kinetic constraints during the redox biotransformation of the azo dye, Reactive Red 2 (RR2), and carbon tetrachloride (CT) mediated by soluble humic acids (HAs) and immobilized humic acids (HAi), as well as by the quinoid model compounds, anthraquinone-2,6-disulfonate (AQDS) and 1,2-naphthoquinone-4-sulfonate (NQS). The microbial reduction of both HAs and HAi by anaerobic granular sludge (AGS) was the rate-limiting step during decolorization of RR2 since the reduction of RR2 by reduced HAi proceeded at more than three orders of magnitute faster than the electron-transferring rate observed during the microbial reduction of HAi by AGS. Similarly, the reduction of RR2 by reduced AQDS proceeded 1.6- and 1.9-fold faster than the microbial reduction of AQDS by AGS when this redox mediator (RM) was supplied in soluble and immobilized form, respectively. In contrast, the reduction of NQS by AGS occurred 1.6- and 19.2-fold faster than the chemical reduction of RR2 by reduced NQS when this RM was supplied in soluble and immobilized form, respectively. The microbial reduction of HAs and HAi by a humus-reducing consortium proceeded 1,400- and 790-fold faster than the transfer of electrons from reduced HAs and HAi, respectively, to achieve the reductive dechlorination of CT to chloroform. Overall, the present study provides elucidation on the rate-limiting steps involved in the redox biotransformation of priority pollutants mediated by both HAs and HAi and offers technical suggestions to overcome the kinetic restrictions identified in the redox reactions evaluated.

  2. Micropore surface area of alkali-soluble plant macromolecules (humic acids) drives their decomposition rates in soil.

    PubMed

    Papa, Gabriella; Spagnol, Manuela; Tambone, Fulvia; Pilu, Roberto; Scaglia, Barbara; Adani, Fabrizio

    2010-02-01

    Previous studies suggested that micropore surface area (MSA) of alkali-soluble bio-macromolecules of aerial plant residues of maize constitutes an important factor that explains their humification in soil, that is, preservation against biological degradation. On the other hand, root plant residue contributes to the soil humus balance, as well. Following the experimental design used in a previous paper published in this journal, this study shows that the biochemical recalcitrance of the alkali-soluble acid-insoluble fraction of the root plant material, contributed to the root maize humification of both Wild-type maize plants and its corresponding mutant brown midrib (bm3), this latter characterized by reduced lignin content. Humic acids (HAs) existed in root (root-HAs) were less degraded in soil than corresponding HAs existed in shoot (shoot-HAs): shoot-HAs bm3 (48%)>shoot-HAs Wild-type (37%)>root-HAs Wild-type (33%)>root-HAs bm3 (22%) (degradability shown in parenthesis). These differences were related to the MSA of HAs, that is, root-HAs having a higher MSA than shoot-HAs: shoot-HAs bm3 (41.43+/-1.2m(2)g(-1))HA-MSAs (r=-0.88, P<0.08, n=4), confirming that MSA was able to explain bio-macromolecules recalcitrance in soil.

  3. Rapid and highly efficient preconcentration of Eu(III) by core-shell structured Fe3O4@humic acid magnetic nanoparticles.

    PubMed

    Yang, Shitong; Zong, Pengfei; Ren, Xuemei; Wang, Qi; Wang, Xiangke

    2012-12-01

    In this study, humic acid-coated Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4)@HA MNPs) were synthesized using a chemical coprecipitation method and characterized in detail. The XRD analysis results showed that HA coating did not change the phase of Fe(3)O(4) cores. The TEM image suggested that Fe(3)O(4)@HA MNPs had nearly uniform size without the observation of aggregation. The Fe(3)O(4)@HA MNPs were stable in solution and could be easily separated from aqueous solution using a magnetic separation method. A batch technique was adopted to investigate the removal efficiency of Fe(3)O(4)@HA MNPs toward Eu(III) under various environmental conditions. The kinetic process of Eu(III) sorption on Fe(3)O(4)@HA MNPs reached equilibrium within <30 min. The fast sorption kinetics and high sorption amount were attributed to the plentiful surface sites provided by the surface-coated HA macromolecules. The Fe(3)O(4)@HA MNPs was able to remove ~99% of Eu(III) in aqueous solution at pH 8.5. Except for SO(4)(2-) anions, the coexisting electrolyte ions had no significant competition effects on the removal of Eu(III) by Fe(3)O(4)@HA MNPs. The obvious sorption-desorption hysteresis suggested that the removal of Eu(III) was dominated by inner-sphere surface complexation. The sorption isotherm agreed well with the Langmuir model, having a maximum sorption capacity of 6.95 × 10(-5) mol g(-1). The leaching test showed that the Eu(III)-loaded Fe(3)O(4)@HA colloids were capable to maintain high thermodynamic stability for long aging times. The findings herein suggested that Fe(3)O(4)@HA MNPs could be potentially used as a highly effective material for the enrichment and preconcentration of radionuclide Eu(III) or other trivalent lanthanides/actinides in geological repositories or in nuclear waste management.

  4. Recycling of wastes from fish beneficiation by composting: chemical characteristics of the compost and efficiency of their humic acids in stimulating the growth of lettuce.

    PubMed

    Busato, Jader Galba; de Carvalho, Caroline Moreira; Zandonadi, Daniel Basilio; Sodré, Fernando Fabriz; Mol, Alan Ribeiro; de Oliveira, Aline Lima; Navarro, Rodrigo Diana

    2017-11-23

    Waste from the beneficiation of fish was composted with crushed grass aiming to characterize their chemical composition and investigate the possibility of the use of the final compost as source of humic acids (HA) able to stimulate the growth of lettuce. Compost presented pH value, C/N ratio, and electrical conductivity that allow its use as an organic fertilizer. The element content was present in the following order of abundance in the compost: P > Ca > N > Mg > K > Fe > Zn > Mn > Mo > Cu, and the humus composition was similar to that observed in others kind of organic residues composted. The high content of oxygen pointed out a high level of oxidation of HA, in line with the predominance of phenolic acidity in the functional groups. The 13 C-NMR spectra showed marked resonances due to the presence of lipids and other materials resistant to degradation as methoxy substituent and N-alkyl groups. A concentration of 20 mg L -1 HA increased significantly both dry and wet root matter in lettuce but the CO 2 assimilation, stomatal conductance, and number of lateral roots of the plants were not affected. However, increases of 64% in the water-use efficiency was observed due to the HA addition, probably related to the root morphology alteration which resulted in 1.6-fold increase of lateral root average length and due to the higher H + extrusion activity. Reuse of residues from the fish beneficiation activity by composting may represent a safe tool to increase the value of recycled organic residues and generate HA with potential use as plant growth stimulants.

  5. Simultaneous removal of As, Cd, Cr, Cu, Ni and Zn from stormwater using high-efficiency industrial sorbents: Effect of pH, contact time and humic acid.

    PubMed

    Genç-Fuhrman, Hülya; Mikkelsen, Peter S; Ledin, Anna

    2016-10-01

    The effect of contact time, solution pH, and the presence of humic acid (HA) on the combined removal of As, Cd, Cr, Cu, Ni and Zn is investigated in batch tests using alumina, granulated activated carbon (GAC), and bauxsol coated sand (BCS) as sorbents. It is found that the equilibrium time for Cd, Cu, Ni and Zn is about 4h, while no clear equilibrium is observed for As and Cr. It is also found that increasing the pH until pH~8 enhanced Cd, Cu, Ni and Zn removal, but increasing the pH above this point had no major effect. In the cases of As and Cr, higher pH values (i.e. >7) decreased their removal. The presence of both 20 and 100mg/L HA suppressed the heavy metal removal except for Cr, and the suppression was higher at the higher HA concentration. Geochemical simulations suggest that this is due to the formation of dissolved HA-metal complexes preventing effective metal sorption. In the case of Cr, the presence of HA increased the removal when using alumina or BCS, while hindering the removal when using GAC. The findings show that the pH-value of the stormwater to be treated must be in the range of 6-7 in order to achieve removal of the full spectrum of metals. The results also show that natural organic matter may severely influence the removal efficiency, such that, for most metals the removal was reduced to the half, while for Cr it was increased to the double for alumina and BCS. Consequently, a properly working filter set up may not work properly anymore when receiving high loads of natural organic acids during the pollen season in spring or during defoliation in autumn and early winter, and during mixing of runoff with snowmelt having a low pH. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. 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) acids by 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.

  7. Effects of Humic Acid and Suspended Solids on the Removal of Heavy Metals from Water by Adsorption onto Granular Activated Carbon

    PubMed Central

    Sounthararajah, Danious P.; Loganathan, Paripurnanda; Kandasamy, Jaya; Vigneswaran, Saravanamuthu

    2015-01-01

    Heavy metals constitute some of the most dangerous pollutants of water, as they are toxic to humans, animals, and aquatic organisms. These metals are considered to be of major public health concern and, therefore, need to be removed. Adsorption is a common physico-chemical process used to remove heavy metals. Dissolved organic carbon (DOC) and suspended solids (SS) are associated pollutants in water systems that can interact with heavy metals during the treatment process. The interactions of DOC and SS during the removal of heavy metals by granular activated carbon were investigated in batch and fixed-bed column experiments. Batch adsorption studies indicated that Langmuir adsorption maxima for Pb, Cu, Zn, Cd, and Ni at pH 6.5 were 11.9, 11.8, 3.3, 2.0, and 1.8 mg/g, respectively. With the addition of humic acid (HA) (DOC representative), they were 7.5, 3.7, 3.2, 1.6, and 2.5 mg/g, respectively. In the column experiment, no breakthrough (complete removal) was obtained for Pb and Cu, but adding HA provided a breakthrough in removing these metals. For Zn, Cd and Ni, this breakthrough occurred even without HA being added. Adding kaolinite (representative of SS) had no effect on Pb and Cu, but it did on the other metals. PMID:26343692

  8. Effects of Humic Acid and Suspended Solids on the Removal of Heavy Metals from Water by Adsorption onto Granular Activated Carbon.

    PubMed

    Sounthararajah, Danious P; Loganathan, Paripurnanda; Kandasamy, Jaya; Vigneswaran, Saravanamuthu

    2015-08-27

    Heavy metals constitute some of the most dangerous pollutants of water, as they are toxic to humans, animals, and aquatic organisms. These metals are considered to be of major public health concern and, therefore, need to be removed. Adsorption is a common physico-chemical process used to remove heavy metals. Dissolved organic carbon (DOC) and suspended solids (SS) are associated pollutants in water systems that can interact with heavy metals during the treatment process. The interactions of DOC and SS during the removal of heavy metals by granular activated carbon were investigated in batch and fixed-bed column experiments. Batch adsorption studies indicated that Langmuir adsorption maxima for Pb, Cu, Zn, Cd, and Ni at pH 6.5 were 11.9, 11.8, 3.3, 2.0, and 1.8 mg/g, respectively. With the addition of humic acid (HA) (DOC representative), they were 7.5, 3.7, 3.2, 1.6, and 2.5 mg/g, respectively. In the column experiment, no breakthrough (complete removal) was obtained for Pb and Cu, but adding HA provided a breakthrough in removing these metals. For Zn, Cd and Ni, this breakthrough occurred even without HA being added. Adding kaolinite (representative of SS) had no effect on Pb and Cu, but it did on the other metals.

  9. Elastin-like Protein-Hyaluronic acid (ELP-HA) Hydrogels with Decoupled Mechanical and Biochemical cues for Cartilage Regeneration

    PubMed Central

    Zhu, Danqing; Wang, Huiyuan; Trinh, Pavin; Heilshorn, Sarah C.; Yang, Fan

    2018-01-01

    Hyaluronic acid (HA) is a major component of cartilage extracellular matrix and is an attractive material for use as 3D injectable matrices for cartilage regeneration. While previous studies have shown the promise of HA-based hydrogels to support cell-based cartilage formation, varying HA concentration generally led to simultaneous changes in both biochemical cues and stiffness. How cells respond to the change of biochemical content of HA remains largely unknown. Here we report an adaptable elastin-like protein-hyaluronic acid (ELP-HA) hydrogel platform using dynamic covalent chemistry, which allows varyiation of HA concentration without affecting matrix stiffness. ELP-HA hydrogels were created through dynamic hydrazone bonds via the reaction between hydrazine-modified ELP (ELP-HYD) and aldehyde-modified HA (HA-ALD). By tuning the stoichiometric ratio of aldehyde groups to hydrazine groups while maintaining ELP-HYD concentration constant, hydrogels with variable HA concentration (1.5%, 3%, or 5%) (w/v) were fabricated with comparable stiffness. To evaluate the effects of HA concentration on cell-based cartilage regeneration, chondrocytes were encapsulated within ELP-HA hydrogels with varying HA concentration. Increasing HA concentration led to a dose-dependent increase in cartilage-marker gene expression and enhanced sGAG deposition while minimizing undesirable fibrocartilage phenotype. The use of adaptable protein hydrogels formed via dynamic covalent chemistry may be broadly applicable as 3D scaffolds with decoupled niche properties to guide other desirable cell fates and tissue repair. PMID:28268018

  10. Effects of Humic and Fulvic Acids on Silver Nanoparticle Stability, Dissolution, and Toxicity

    PubMed Central

    Gunsolus, Ian L.; Mousavi, Maral P. S.; Hussein, Kadir; Bühlmann, Philippe; Haynes, Christy L.

    2015-01-01

    The colloidal stability of silver nanoparticles (AgNPs) in natural aquatic environments influences their transport and environmental persistence, while their dissolution to Ag+ influences their toxicity to organisms. Here, we characterize the colloidal stability, dissolution behavior, and toxicity of two industrially relevant classes of AgNPs (i.e., AgNPs stabilized by citrate or polyvinylpyrrolidone) after exposure to natural organic matter (NOM, i.e., Suwannee River Humic and Fulvic Acid Standards and Pony Lake Fulvic Acid Reference). We show that NOM interaction with the nanoparticle surface depends on (i) the NOM’s chemical composition, where sulfur- and nitrogen-rich NOM more significantly increases colloidal stability, and (ii) the affinity of the capping agent for the AgNP surface, where nanoparticles with loosely bound capping agents are more effectively stabilized by NOM. Adsorption of NOM is shown to have little effect on AgNP dissolution under most experimental conditions, the exception being when the NOM is rich in sulfur and nitrogen. Similarly, the toxicity of AgNPs to a bacterial model (Shewanella oneidensis MR-1) decreases most significantly in the presence of sulfur- and nitrogen-rich NOM. Our data suggest that the rate of AgNP aggregation and dissolution in aquatic environments containing NOM will depend on the chemical composition of the NOM, and that the toxicity of AgNPs to aquatic microorganisms is controlled primarily by the extent of nanoparticle dissolution. PMID:26047330

  11. Sorption mechanism of enrofloxacin on humic acids extracted from Brazilian soils.

    PubMed

    Martínez-Mejía, Mónica J; Sato, Isabela; Rath, Susanne

    2017-07-01

    Veterinary antimicrobials are emerging environmental contaminants of concern. In this study, the sorption of enrofloxacin (ENR) onto humic acids (HAs) extracted from three Brazilian soils was evaluated. HAs were characterized by elemental analysis and solid 13 C nuclear magnetic resonance spectroscopy. The sorption of ENR onto HAs was at least 20-fold higher than onto the soils from which they were separated. Ionic and cation bridging are the primary interactions involved. The interactions driven by cation exchange are predominant on HAs, which appear to have abundant carboxylic groups and a relatively high proportion of H-bond donor moieties with carbohydrate-like structures. Interactions explained by cation bridging and/or surface complexation on HAs are facilitated by moieties containing conjugated ligands, significant content of oxygen-containing functional groups, such as phenolic-OH or lignin-like structures. HAs containing electron-donating phenolic moieties and carboxylic acid ligand groups exhibi