Role Of Humic Acid Research Articles

Strong adsorption of DNA molecules on humic acids

Analysing soil microbial communities is often hampered by DNA adsorption on soil organic compounds such as humic acids. However the role of humic acids in DNA adsorption and stability in soils remains controversial. To characterize DNA–humic acid interactions, we studied DNA adsorption on two commercially available humic acids and a soil humic acid extracted from an Andosol. Desorption of the adsorbed DNA using 4 different solutions—distilled water, 0.1 M NaCl, 0.1 M sodium phosphate buffer (pH 6.0), and 1% sodium dodecyl sulfate solution—was also studied to understand the mechanism of DNA adsorption on humic acids. Here, we show that humic acids play an important role in DNA adsorption to soils. DNA molecules were adsorbed on the humic acids, with adsorption increasing proportionally with the DNA concentrations in the solution. The adsorption on all humic acid samples was fitted with Freundlich equation, and the parameters obtained from the equation indicated a high affinity between the humic acids and DNA molecules. The total amount of DNA desorbed by the 4 solutions was less than 2% of the total DNA adsorbed on all the humic acids. The results demonstrate that DNA molecules are able to bind strongly to humic acids by ligand binding, hydrophobic interaction, aggregation, or precipitation.

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

Context: 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). Objective: 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. Methods: 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. Results: 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. Conclusion: 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.

In situ remediation of metal-contaminated soils with organic amendments: Role of humic acids in copper bioavailability

The purposes of this study were to determine the Cu(II) binding behavior of humic acids (HAs) isolated from biosolid compost (BI), leonardite (LE), a metal-contaminated soil, and the soil remediated with either BI or LE in relation to their structural properties, and to explore the role exerted by the HA fractions in controlling soil Cu(II) bioavailability. Potentiometric titrations at pH 5 and ionic strength 0.1 M and the Langmuir model were used to obtain the Cu(II) complexing capacity of the HAs examined and the conditional stability constant of the Cu(II)–HA complexes. The Cu(II) complexing capacity increased as the content of acidic ligands, especially COOH groups, aromaticity, and humification degree increased, following the order BI-HA < BI-amended soil HAs < unamended soil HA < LE-amended soil HAs < LE-HA. In contrast, the conditional stability constant of Cu(II)–HA complexes increased in the opposite order, probably due to an increased chelating effect. Compared to LE, amendment with BI was slightly more effective in decreasing soil CaCl 2-extractable Cu content. The results obtained suggested that the pH of the soil-amendment system is the most important chemical property governing Cu(II) solubility and bioavailability in metal-contaminated soils remediated with BI and LE, although soil organic matter and the HA fraction may also be important factors. In particular, binding sites formed by N-, S-, and O-containing acidic functional moieties in HAs may play an important role in the Cu(II) behavior.

Effects and mechanism of humic acid on chromium(VI) removal by zero-valent iron (Fe 0) nanoparticles

The present study dealt with the performance evaluation of the nanoscale Fe 0 systems for the remediation of chromium contaminated groundwater in the ambient environment. The role of humic acid (HA) in the Cr(VI) removal and the reduction mechanism were investigated. HA was found to exert an obvious inhibitory effect on Cr(VI) removal by Fe 0 nanoparticles, and the Cr(VI) removal efficiencies decreased from 71.6%, 58.4%, 57.8% to 38.5% with the increasing HA concentrations (0, 5, 10, 20 to 40 mg L −1). A dual effect of humic acid on chromium(VI) reduction by Fe 0 nanoparticles was observed. HA adsorbed on the surface of Fe 0 nanoparticles and occupied the active surface sites, leading to the decrease in Cr(VI) reduction rates. Greater was the adsorbed HA, the more obvious was the inhibitory effect. However, the HA adsorption on iron surface areas was one of the factors leading to the decreased reduction rate. The appropriate starch dosage (0.5 g per 0.3 g nanoscale Fe 0 particles) could definitely eliminate the inhibitory effect of humic acid.

The Role of Humic Acid in Palm Kernel Cake Fermented by Aspergillus niger for Poultry Ration

2 Abstract: An experiment was conducted to improve the nutrient content of palm kernel cake through fermentation by Aspergillus niger with combination humid acid dosage and fermented time. The experiment used Complete Randomize Design (CRD) with 3 x 3 factorial and twice replication. The first factor was humic acid dosage: (1) 0 ppm, (2) 100 ppm and (3) 200 ppm. The second factor was fermented time: (1) 5 day, (2) 7 day and (3) 9 day. The parameters were dry matter, crude protein and crude fiber. The result of study showed that there was no significantly (p>0.05) interaction between humic acid dosage and fermented time to dry matter, but against crude protein and crude fiber, there were highly significant interaction (p 0.05) effected to dry matter, but against crude protein and crude fiber, there were significant (p<0.01) effect. Fermented time showed that there were highly significant (p<0.01) effect to dry matter, crude protein and crude fiber. The conclusion was palm kernel cake which was fermented by Aspergilus niger showed that humic acid 100 ppm and fermented time 7 day had a better content. This condition can be seen in crude protein 23,20%, crude fiber 10,59% and dry matter 42.38%.

In vitro enhancement effect of humic acid on the progression of lung cancer cells

Humic acid, a group of polymer, resulting from the decomposition of organic matter has been implicated as a possible etiological factor for Black foot disease and cancer. However, the role of humic acid in carcinogenesis is not well clarified. In this study, we evaluated the enhancement effect of humic acid on the progression of A549 human lung cancer cells. Our findings showed that humic acid increased the migration, adhesion and invasion of A549 cells significantly after treatment at the concentration of 50 and 100 μg/ml for 24 and 48 h as compared with the untreated group. Results of zymography assay indicated that humic acid enhanced the activity of matrix metalloproteinase 9 (MMP-9). By western blotting analysis, humic acid increased the expression of phosphorylated focal adhesion kinase (FAK) and integrin α2 that may mediate cell motility and adhesion. Since the activation of signal pathways such as phosphoinositide 3-kinase/Akt (PI3K/Akt) and mitogen-activated protein kinases (MAPKs) may play a role in the cell invasion, we detected the expression of phosphorylated Akt and phosphorylated MAPKs including extracellular signal-regulated kinase (ERK), Jun N-terminus kinase (JNK), and p38. The result indicated that all kinases stated above were activated by humic acid in A549 cells. However, by adding an inhibitor respectively in the invasion assay, only Akt, ERK, and JNK pathways were found to be involved in the enhancing the invasion of A549 cells by humic acid. In addition, results of electrophoretic mobility shift assay (EMSA) demonstrated that humic acid increased nuclear extract binding to the DNA probe of activator protein 1 (AP-1) and nuclear factor κB (NFκB) respectively, implying that humic acid enhanced the progression of A549 lung cancer cells through activating multiple signaling pathways including ERK, JNK, and PI3K/Akt and increasing the transcription activation of AP-1 and NFκB.

The Role of Humic Acid, Silicon, and pH in Accrual of Periphytic Biomass in a Subalpine Stream, Colorado Front Range

ABSTRACT The role of humic acid (HA) in biomass accrual in biofilms has been investigated in North Boulder Creek, Colorado, for several years with inconclusive results. In 2006–2007, we used vials containing agar and nutrients capped by a porous substrata, upon which biofilms developed, to test for the biostimulatory effect of silicon (Si), HA, and pH at this same site. Biomass accrual was measured after three weeks as chlorophyll a. In 2006 we tested the hypothesis that HA diffusing through fused silica discs (FSDs) mobilized Si and thus promoted biomass accrual. We also compared biomass accrual on FSDs to that on open-celled styrofoam discs, which contained no Si. No statistical difference was found. While HA seems to mobilize Si from FSDs, a positive effect on biomass accrual could not be demonstrated. In 2007 we performed a factorial experiment to test for interactions between HA and pH. Without HA, biomass accrual was significantly higher at pH 5.0 than at pH 7.0. With HA, no significant differences of biomass accrual were found among three levels of pH (5.0, 6.0, and 7.0). HA seemed to negate the positive effect of lower pH on biomass accrual.

Adhesion of Escherichia coli to Iron‐Coated Sand in the Presence of Humic Acid: A Column Experiment

Column experiments were performed to examine the influence of humic acid on the attachment of Escherichia coli to iron-coated sand. Results show that, in the coated sand, the average mass recovery was 2.9% in deionized water and increased sharply to 94.6% at a humic acid concentration of 16 mg/L. In leaching solution containing both humic acid and phosphate, the mass recovery increased from 26.0 to 94.6%, by increasing the portion of humic acid from 0 to 100% (from 0 to 16 mg/L). In addition, the mass recovery (94.6%) at a humic acid concentration of 16 mg/L was much larger than that (26.0%) at the same concentration of phosphate. This study presents information regarding the role of humic acid in the adhesion of bacteria to iron-coated sand and helps to enhance the knowledge of bacterial removal in positively charged porous media.

Humic acids role in Br accumulation along two ombrotrophic peat bog profiles

Scientific results about the role of peatlands as sink or source of bromine are rather antithetic. Although several attempts have been performed to correlate Br content and peat decomposition/humification, the role of humic acids (HAs) as possible sink of this element has not been previously investigated. Two peat cores (2H and 2T), collected from the ombrotrophic bog Etang de la Gruère (Switzerland), were divided in several slices from which humic acids were successively extracted. Bromine content was determined in both peat and corresponding HAs samples using an Energy-dispersive miniprobe X-ray fluorescence multielement analysis (EMMA-XRF). Data show a greater “affinity” of Br for HAs rather than for corresponding bulk peat samples, especially in the first 24 cm of depth where Br concentration in HAs is 3.5 times higher than the one in peat; in particular, approximately 40% (average value) of the total Br in peat is stably incorporated into HAs molecules. Further, the observed correlation between the Br content in HAs and the Pb enrichment factor in peat, especially in the upper part of both profiles, suggests a possible role of HAs as geochemical sink of Br atmospheric deposition. Consequently, humification processes occurring in peat could promote Br accumulation in HAs, thus reflecting the deposition rate of this trace element.

Rodenticide–humic acid adsorption mechanisms and role of humic acid on their toxicity on human keratinocytes: chromatographic approach to support the biological data

Humic substances are the most important soil components affecting the behaviour and performances of herbicides in the soil–water–organism system. In this paper, a chromatographic approach was used for analysis of anticoagulant rodenticide–humic acid adsorption mechanisms. Using an equilibrium perturbation method, it was clearly shown that: (i) humic acid can be adsorbed on the C18 stationary phase, and (ii) all the rodenticides can be adsorbed on the humic acid adsorbed on the C18 stationary phase. This approach allowed the determination of the adsorption constant values between the anticoagulant rodenticides and humic acid as well as the corresponding thermodynamic data of this adsorption mechanism. The role of humic acid on the toxicity of these rodenticides on human keratinocytes was also clearly described in relation to these physico-chemical data.

Effects of natural organic matter and solution chemistry on the deposition and reentrainment of colloids in porous media.

The role of humic acid in the transport of negatively charged colloids through porous media was examined. Adsorption of humic acid on latex colloids and silica collectors reduced the deposition of suspended particles and enhanced the reentrainment of deposited particles in porous media. These effects are considered to arise from additional electrostatic and steric contributions to the repulsive interaction energy due to the adsorption of negatively charged humic acid on both the suspended particles and the media collectors. At low ionic strength reversible deposition in shallow secondary minima is hypothesized to be the principal attachment mechanism, independent of the presence of humic acid. It is proposed that under these solution conditions, particle deposition and reentrainment are the result of a dynamic process, in which particles are continuously captured and released from secondary minima. At higher ionic strengths, deposition may be regarded as a combination of two mechanisms: capture in the primary well and capture in the secondary minimum. Theoretical calculations of the attachment efficiency were conducted using two existing mathematical models. The first model is based on deposition in the primary well (interaction force boundary layer, IFBL), and the second model is based on the Maxwell kinetic theory and deposition in the secondary minimum (Maxwell model). Simulations conducted with the Maxwell model provide significantly better fits of the experimental results than those conducted with the IFBL model.

Peranan Mikoriza VA, Rhizobium dan Asam Humat pada Pertumbuhan dan Kadar Hara Beberapa Spesies Legum Penutup Tanah

The utilization of acid mineral soil often faces the problem of Al toxicity and low available P. The efforts to improve root function and neutralize the effect of high available Al are becoming important for increasing the growth of legumes, particularly as the cover crops at the plantation on acid soil. This research was aimed to find the effect of VA mycorrhyza inoculation, rhizobium, and humic acid on the growth and nutrient content of four different legume species. It was a three factor factorial experiment arranged in a completely randomized design with three replications. The first factor was four legume species: Calopogonium mucunoides, CaloPogonium ceurelieum, Centrosema pubescens and Puerari iavanica the second factor was four different inoculants: none (M0), MVA (M1), rhizobium (Mz), MVA + rhizobium (M3); the third factor was two rates of humic acid application: without (Ho) and with humic acid (H1) The results proved the positive effect of those three factors on the growth of shoot and roots. The responses of root growth on microorganism inoculations and humic acid were different among the legume cover crop species. The role of humic acid was significantly better if there was a synergism between MV A and rhizobium. Key words: Mycorrhyza, Rhizobium, Humic acid, Legume cover crop

Biogeohydrodynamic in the forested humid tropical environment: the case study of the Nsimi small experimental watershed (south Cameroon)

Biogeohydrodynamic in the forested humid tropical environment: the case study of the Nsimi small experimental watershed (south Cameroon)

Catalysis of PAH biodegradation by humic acid shown in synchrotron infrared studies.

The role of humic acid (HA) in the biodegradation of toxic polycyclic aromatic hydrocarbons (PAHs) has been the subject of controversy, particularly in unsaturated environments. By utilizing an infrared spectromicroscope and a very bright, nondestructive synchrotron photon source, we monitored in situ and, over time, the influence of HA on the progression of degradation of pyrene (a model PAH) by a bacterial colony on a magnetite surface. Our results indicate that HA dramatically shortens the onset time for PAH biodegradation from 168 to 2 h. In the absence of HA, it takes the bacteria about 168 h to produce sufficient glycolipids to solubilize pyrene and make it bioavailable for biodegradation. These results will have large implications for the bioremediation of contaminated soils.

Role of humic acids in the TiO 2-photocatalyzed degradation of tetrachloroethene in water

The effect of humic acids on the TiO 2-mediated photocatalytic degradation of tetrachloroethene (PCE) was kinetically investigated at different pH and initial substrate concentrations. The process occurs through two parallel paths: a major oxidative route leading to mineralization and a reductive route leading to the formation of dichloroacetic acid (DCAA), also undergoing photodegradation. The rate of PCE decomposition was found to decrease in the presence of humic acids adsorbed on the semiconductor surface, while the concentration of the intermediate dichloroacetic acid increased. This is a consequence of the scavenging action of humic acids toward photoproduced surface oxidant species, which makes conduction band electrons more easily available for interface reactions. Kinetic studies on the effect of humic acids in the TiO 2-mediated photodegradation of dichloroacetic acid showed that the progressively greater accumulation of this highly toxic intermediate, observed with increasing humic acids content, was a consequence of both an increase in the rate of its production from PCE and a decrease in the rate of its oxidative photodegradation.

The role of humic acid on sulfate retention and release in a podzol

Sequential leaching experiments were performed to evaluate the effects of humic acid (HA) and pH on SO4 retention and release in a Swedish podzolic B-horizon. Results showed that the presence of HA reduced SO4 retention and that HA was released when SO4 was retained. Increasing HA concentration increased the rate of SO4 release. The ability of HA to compete with SO4 increased with pH. More than 40% of total sorbed SO4 was irreversibly retained.

A Study into the Cause of Decline in pH During Water Distribution

ABSTRACTThis STUDY INVESTIGATES the decline in pH of soft waters during distribution. The fieldwork and laboratory data confirmed and quantified the pH decline in soft water that had had the pH increased by lime addition at the treatment stage. A pH of 9.0 can decline to 7.5 during distribution. The role of humic acid as a causative agent of pH decline is examined in detail by modified jar test experiments and the development of a dialysis technique. The results of these experiments show that binding or complexing occurs between the humic acid and the calcium ions. This complexing generates H+ ions with the consequential decline in pH of the water.

Trace metals in humic acids and their hydrolysis products

The role of humic acids in the transport of trace elements in the Sava river biocycle (near Zagreb, Yugloslavia) has been investigated by means of neutron activation analysis. Humic acids can accumulate certain trace elements, but little is known about their selectivity under certain physicochemical conditions. Humic acids isolated from Sava river sediments were hydrolized to their main components, namely to amino acids (proteins), phenols (and phenolic acids), carbohydrates, polycyclic aromatics, and metals. Degradation of humic acids in the environment occurs by the action of microorganisms, and during this step, certain trace metals become available to Sava river animals through standard physiological processes. In this work neutron activation analysis was applied to the quantitative and qualitative determination of trace metals in humic acids of Sava river origin, and in their hydrolysis products. The trace metals measured were Ag, Fe, Co, Cs, Eu, Sb, Sc, Se, and Sr. The concentrations obtained ranged from 0.05 to 2730 micrograms of a certain microconstituent per gram of sample. The experimental data are compared with the laboratory experiments on the determination of stability constants for metal complexes of humic acids and their hydrolysis product. From these data it is possible to suggest the ecological importance of trace metals bonded to humic acids in a certain region. The results concerning the role of humic acids in the cycle of trace elements in Sava river biocycle are discussed.

Coagulation Behaviour of the Interstratified Clay Minerals in Dilute Suspension

The state of coagulation of the naturally occurring I: M interstratified clay minerals has been studied with kaolinite, acid, alkali, polar and non-polar organic solvents in their dilute H-clay form. The role of humic acids and iron compounds associated with them has also been discussed. It has been observed that the interstratified minerals did not show any coagulation due to mutual interaction with kaolinite. Further, they behaved like montmorillonite in acid and kaolinite in alkaline media. The existence of some specific exchangeable spots which undergo mutual interaction with kaolinite for coagulation is postulated.

Electron intensity, the role of humic acids in extracellular electron transport and chemical determination of pE in natural waters

Experimental systems demonstrate that humic acids are capable of accepting electrons from a wide spectrum of donors and transferring those electrons to a wide spectrum of acceptors, linking normally thermodynamically discrete redox couples. By functioning as a wide redox potential ‘flavoprotein’, humics encompass all the redox potentials pertinent to aquatic systems and hence determine relative electron activity, the negative log of which is pE. A chemically determined, system oxidation-reduction potential allows pE to be used along with pH in developing a biochemical framework for thermodynamically derived predictions of aquatic system behavior.