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PubMed2001

Sorption of naphthalene and phenanthrene by soil humic acids.

Humic acids are a major fraction of soil organic matter (SOM), and sorption of hydrophobic organic chemicals by humic acids influences their behavior and fate in soil. A clear understanding of the sorption of organic chemicals by humic acids will help to determine their sorptive mechanisms in SOM and soil. In this paper, we determined the sorption of two hydrophobic organic compounds, naphthalene and phenanthrene by six pedogenetically related humic acids. These humic acids were extracted from different depths of a single soil profile and characterized by solid-state CP/MAS 13C nuclear magnetic resonance (NMR). Aromaticity of the humic acids increased with soil depth. Similarly, atomic ratios of C/H and C/O also increased with depth (from organic to mineral horizons). All isotherms were nonlinear. Freundlich exponents (N) ranged from 0.87 to 0.95 for naphthalene and from 0.86 to 0.92 for phenanthrene. The N values of phenanthrene were consistently lower than naphthalene for a given humic acid. For both compounds, N values decreased with increasing aromaticity of the humic acids, such an inverse relationship was never reported before. These results support the dual-mode sorption model where partitioning occurs in both expanded (flexible) and condensed (rigid) domains while nonlinear sorption only in condensed domains of SOM. Sorption in the condensed domains may be a cause for slow desorption, and reduced availability and toxicity with aging.

Adsorption↗

PubMed2001

Heavy metal budgets for two headwater forested catchments in background areas of Finland.

Mean annual (1994-1996) budgets for Cd, Cu, Ni, Pb and Zn at two background, forested catchments, VK and HJ, in Finland are presented. Budgets for plots (VK3, HJ1 and HJ4) included throughfall (TF), litterfall (LF) and soil leaching fluxes, and for catchments terrestrial retention and leaching and lake sedimentation fluxes. Total deposition (TD) loads were relatively low (Cd < 0.1, Cu < 2, Ni < 1, Pb < 3 and Zn < 5 mg m-2 year-1) and that even in these areas almost half of the TD was in the form of dry deposition. Retention of TD within catchments was > or = 77% for all metals, except for Ni at VK (54%). For Cu and Pb, the retention was 94-97%. Most of the retention (74-97%) took place in the terrestrial part of the catchment, lake sedimentation accounting for the remainder. Plot-scale soil leaching fluxes at 40 cm of Cd, Cu (VK3) and Ni (VK3) were greater (> or = 100%) than TD inputs. Most of the catchment retention must therefore have taken place either deeper in the soil or in the lowland peatland areas. The humus layer was particularly effective in retaining Cu and Cd (65-81% and 51-78% of total inputs to the forest floor (TF + LF)). The retention of Pb by the humus layer was less than expected (26-54% of TF + LF). Litterfall was a particularly important internal flux for Zn.

Air Pollutants↗

PubMed2003

Influence of particle characteristics and organic matter content on the bioavailability and bioaccumulation of pyrene by clams.

Hydrophobic chemicals are known to associate with sediment particles including those from both suspended particulate matter and bottom deposits. The complex and variable composition of natural particles makes it very difficult therefore, to predict the bioavailability of sediment-bound contaminants. To overcome these problems we have previously devised a test system using artificial particles, with or without humic acids, for use as an experimental model of natural sediments. In the present work we have applied this experimental technique to investigate the bioavailability and bioaccumulation of pyrene by the freshwater fingernail clam Sphaerium corneum. The uptake and accumulation of pyrene in clams exposed to the chemical in the presence of a sample of natural sediment was also investigated. According to the results obtained, particle surface properties and organic matter content are the key factors for assessing the bioavailability and bioaccumulation of pyrene by clams.

Absorption↗

PubMed2003

Effects of organic acids on adsorption of lead onto montmorillonite, goethite and humic acid.

Adsorption isotherms for Pb onto six soil components (quartz, feldspar, kaolinite, montmorillonite, goethite and humic acid) were studied. The influence of pH, EDTA and citric acid on the adsorption of Pb onto montmorillonite, goethite and humic acid were considered. Results indicate that the experimental data fit the Langmuir Adsorption Isotherm. The adsorption capacity for Pb at pH 6 was found to be in the order: humic acid (22.7 mg g(-1)) > goethite (11.04 mg g(-1)) > montmorillonite (10.4 mg g(-1)) > kaolinite (0.91 mg g(-1)) > feldspar (0.503 mg g(-1)) > quartz (0.148 mg g(-1)). Generally, the amount of Pb adsorbed onto montmorillonite, goethite and humic acid decreased with increasing concentrations of EDTA and citric acid and with increases in alkality. However, there were two exceptions: (1) addition of citric acid increased the amount of Pb adsorbed onto humic acid; and (2) the amount of Pb adsorbed onto goethite decreased with increasing pH in the presence of EDTA. Some mechanisms involved in the adsorption reactions are discussed.

Adsorption↗

PubMed1997

Use of biologically reclaimed minerals for continuous hydroponic potato production in a CELSS.

Plant-derived nutrients were successfully recycled in a Controlled Ecological Life Support System (CELSS) using biological methods. The majority of the essential nutrients were recovered by microbiologically treating the plant biomass in an aerobic bioreactor. Liquid effluent containing the nutrients was then returned to the biomass production component via a recirculating hydroponic system. Potato (Solanum tuberosum L.) cv. Norland plants were grown on those nutrients in either a batch production mode (same age plants on a nutrient solution) or a staggered production mode (4 different ages of plants on a nutrient solution). The study continued over a period of 418 days, within NASA Breadboard Project's Biomass Production Chamber at the Kennedy Space Center. During this period, four consecutive batch cycles (104-day harvests) and 13 consecutive staggered cycles (26-day harvests) were completed using reclaimed minerals and compared to plants grown with standard nutrient solutions. All nutrient solutions were continually recirculated during the entire 418 day study. In general, tuber yields with reclaimed minerals were within 10% of control solutions. Contaminants, such as sodium and recalcitrant organics tended to increase over time in solutions containing reclaimed minerals, however tuber composition was comparable to tubers grown in the control solutions.

Biomass↗

PubMed2000

Analysis of potentiometric titrations of heterogeneous natural polyelectrolytes in terms of counterion condensation theory: application to humic acid.

A model, developed within the framework of the counterion condensation theory of linear polyelectrolytes, is presented in this paper to describe the acid-base properties of linear polyelectrolytes, consisting of several types of functional ionizable groups. This formalism has been successfully applied to Fluka humic acid under salt-free conditions, as well as in the presence of supporting simple 1:1 salt (KNO3) at three different concentrations. As part of this approach, the charge density of the humic acid is obtained from the activity coefficient measurements of potassium counterions at different humic acid concentrations at a constant degree of dissociation of the polyelectrolyte. The humic acid average charge density was found to be 0.80 +/- 0.05. Using the present model, we are able to satisfactorily describe the experimental data obtained from acid-base potentiometric titrations. Four main functional groups making up the polymer are determined through their fractional abundances (Xi) and intrinsic pK (pK0i) values. The fractional abundances remained constant and independent of the ionic strength, indicating that the humic acid constitution does not depend on the concentration of excess salts. The pK0i values show a small change with ionic strength, which can be explained by the polyelectrolytic behavior of the solution.

Algorithms↗

PubMed2000

Polychlorinated biphenyl (PCB) recovery from spiked organic matrix using accelerated solvent extraction (ASE) and Soxhlet extraction.

The recovery of five PCB congeners from PCB spiked organic matrices was studied using Accelerated solvent extraction (ASE) and Soxhlet extraction (SE). The chromatogram of ASE extract was found to be relatively clean and similar to that of SE extract. ASE extraction efficiency was dependent on the operation temperature and sample size loading. ASE showed extraction efficiency comparable or slightly higher to that of SE for the PCB spiked organic matrix. PCB recovery from spiked matrix was dependent on the type and molecular weight of congener, and nature of matrix. For some selected PCB congeners, ortho-substitution did influence the PCB recovery from graphite matrix.

Coal↗

PubMed2001

The influence of different soil constituents on the reaction kinetics of wet oxidation of the creosote compound quinoline.

Creosote contaminated sites have become a widespread problem in industrialized countries. Recently, wet oxidation using high temperature, pressure, water and oxygen followed by activated sludge treatment proved to be an efficient method for removing a wide selection of creosote compounds in contaminated soils. Wet oxidation of the creosote compound quinoline was carried out in the presence of montmorillionite, quartz and humic acid. The products derived from wet oxidation were identified and treated biologically by activated sludge testing their biodegradability. The influence on the oxidation kinetics of quinoline during wet oxidation was pH dependent. Humic acid supported the oxidation of quinoline, whereas the addition of montmorillionite and quartz had either an inhibiting effect or led only to a slight increase in oxidation. In mixtures of soil constituents, especially at low contents of humic acid, the adsorption of quinoline on montmorillionite prevented oxidation at neutral pH. Thus, alkaline extraction of both quinoline and humic acid was needed for an efficient oxidation. A proposed reaction mechanism suggests that quinoline was oxidized by hydroxyl radicals formed during the oxidation of the humic acid. A wide selection of reaction products (mainly carboxylic acids, benzene and pyridine derivatives) derived from the wet oxidation of humic acid and quinoline. The reaction products from humic acid degradation had a rate limiting effect on the wet oxidation of quinoline leaving small residues of quinoline after the treatment. On the contrary, these reaction products also improved the biodegradation of products from the quinoline oxidation due to co-digestion of carboxylic acids. Therefore, the presence of soil components (mainly humic acid) improved the combined wet oxidation and biological activated sludge treatment of quinoline.

Biodegradation, Environmental↗

PubMed2001

Release of Cr(III) from Cr(III) picolinate upon metabolic activation.

Hexavalent and trivalent chromium are released into the environment from a number of different industrial activities. It is known that Cr(VI) can be reduced and subsequently complexed by humic acids to produce Cr(III) humic acid complexes in the soil and aquatic environments. The metabolic fate of Cr(III) humic acid complexes and other Cr(III) organic complexes in mammalian systems is unknown. Therefore, Cr(III) picolinate was chosen as a model complex for Cr(III) humic acid complexes and other environmentally relevant Cr(III) complexes. Both human hepatocyte microsomes and primary cultures of chick hepatocytes were used to generate metabolites of Cr(III) picolinate. The results from both of these treatments show that a significant amount of Cr(III) is released (66 and 100%, respectively) and that N-1-methylpicotinamide is the primary organic metabolite from this compound. These data suggest that the populations of humans who are exposed Cr(III) picolinate or other environmentally relevant organic Cr(III) complexes, such as Cr(III) humic acid complexes, are potentially accumulating high levels of Cr(III) intracellularly. This intracellular accumulation of Cr(III) can result in the formation of covalent bonds between Cr(III) and DNA and/or other macromolecules, causing genotoxic effects. These data should be considered when assessing the risk of an area contaminated with chromium.

Animals↗

PubMed2002

Solubility enhancement of PCDD/F in the presence of dissolved humic matter.

From previous studies, we, the authors collected and arranged the octanol-water partition coefficients (K(ow)), water solubility (S0), and dissolved humic matter (DHM)-water partition coefficients (K(oc)) for 95 organic compounds, and presented the correlations between each physical property. The K(oc) and K(ow) of dioxins estimated were significantly increased while S0 was decreased on increasing the chlorine number. In the presence of DHM, solubility enhancement (Sw/S0, Sw is the actual solubility in the presence of DHM) in highly chlorinated PCDD/F such as HpCDDs and OCDD is higher than that in low chlorinated ones. It means that dioxins abundant wastes (fly ash) should not be codisposed with organic abundant wastes (sewage sludge, food waste or bottom ash, etc.) to minimize the leachability of dioxins.

Benzofurans↗

PubMed2003

Electrokinetic remediation of clayey soils containing copper(II)-oxinate using humic acid as a surfactant.

The utility of humic acid (HA) as a surfactant for use in the electrokinetic remediation (ER) of the clayey soils containing copper(II)-oxinate (Cu(OX)(2)) was examined. A small simulator of ER was devised, which consisted of three types of artificial soils on the basis of the commercial kaolin: kaolin, kaolin + HA and kaolin + Cu(OX)(2). The layers of kaolin containing HA and Cu(OX)(2) were sandwiched between two kaolin layers. In all experiments, a constant dc voltage gradient of 2.2V/cm was applied through the soil for 30h, and the pH of the solution in the anodic chamber was maintained at 7.0. Generally, HA has a negative charge at a neutral pH. However, the HA was mainly transferred to the cathodic chamber. This shows that the driving force of the HA in the system used herein is predominantly due to electroosmotic flow. Moreover, the amount of Cu(OX)(2) removed from the clayey soils in the presence of HA was three times larger than those in the absence of HA. This can be attributed to the fact that the water solubility of Cu(OX)(2) is enhanced by the presence of HA. Thus, we conclude that HA has a potential for use as an amendment for the ER of hydrophobic chemicals, such as Cu(OX)(2).

Aluminum Silicates↗

PubMed2003

Role of humic acid entrapped calcium alginate beads in removal of heavy metals.

Most of the available techniques for removal of heavy metals from solution such as leachates from waste sites are very expensive. The technique described in this paper is designed to study the removal of humic acid by alginate beads and the subsequent binding of the metals within the beads thus decreasing the leachability of heavy metals from a hazardous waste site. The entry of 500 mg/l humic acid into 3% calcium alginate beads in 24 h showed a distinct fluorescence as compared to the fluorescence shown by the entry of 100 and 250 mg/l of humic acid into alginate beads. Further, on treatment of calcium alginate beads containing 500 mg/l humic acid with metals such as Cu, Mn, Zn, Cr and Fe, quenching of fluorescence was noticed, which was maximum with Cu and minimum with Fe.

Alginates↗

PubMed2003

Effect of sequestration on PAH degradability with Fenton's reagent: roles of total organic carbon, humin, and soil porosity.

The phenomenon of contaminant sequestration-and the physicochemical soil parameters which drive this process-has recently been studied by several authors with regard to microbial contaminant degradation. Very little work has been done to determine the effects of contaminant sequestration on the chemical treatability (oxidizability) of soil contaminants; the current study was conducted to address this data gap. A suite of six model soils, ranging in organic matter content from 2.32 to 24.28%, were extensively characterized. Measured parameters included: (1) levels of total organic carbon (TOC); (2) contents of humic acid (HA); fulvic acid (FA) and humin; and (3) total porosity and surface area. Each soil was then spiked with coal tar and, after varying periods of aging/sequestration, subjected to slurry-phase Fenton's reagent oxidation. Percent recoveries of 12 PAHs, ranging from 3 to 6 aromatic rings, were determined. Results indicated that the susceptibility of each PAH to chemical oxidation was a function of TOC in four of the soils (those with TOC greater than approximately 5%), but was strongly dependent on soil porosity for low-TOC soils. The importance of these two parameters changed with increasing sequestration time, with the relative contribution of porosity-mediated sequestration becoming more important over time. Porosity-mediated effects were more rapid and significant with lower-molecular-weight PAHs (e.g. those with three or four aromatic rings) than with higher-molecular-weight, more hydrophobic compounds. These observations are discussed in light of current physicochemical models of the contaminant sequestration process.

Benzopyrans↗

PubMed1980

Degradation of humic acids, extracted from manure and soil by some streptomycetes and fungi.

Humate-decomposing microorganisms were isolated from alluvial soil, farmyard manure and peat by direct plating and enrichment techniques. Peat was found to harbour more of these organisms than soil and manure. Out of 21 actinomycetes and 6 fungi 9 and 3 isolates, respectively, were found to utilize manure-humate as a sole source of carbon and to a less extent as a source of both carbon and nitrogen in liquid medium. These efficient cultures were identified as Streptomyces spec. (A 11 and A 12). Str. candidus, Str. violaceoruber (A 41 and A 42), Str. rubescens, Str. garyphalus, Str. viridochromogenes, Fusarium solani, Aspergillus fumigatus, and Penicillium roseopurpureum. Additional sources of carbon and nitrogen stimulated microbial degradation of humate. Only five isolates formed a zone of decolourization on humate-containing solid medium. Soil humic acid was utilized by Str. candidus as a sole source of carbon and nitrogen, however, F. solani utilized it only in the presence of additional carbon and nitrogen sources. Extent of soil-humate degradation was less than manure-humate.

Culture Media↗

PubMed2003

A possible purification method of DNAs' fragments from humic matters in soil extracts using novel stimulus responsive polymer adsorbent.

Novel stimulus responsive, uniformly sized polymer-based adsorbent was prepared for a possible purification method of DNAs from humic matters in soil extracts. The prepared polymer adsorbent has a pair of anion exchangeable and cation exchangeable polymeric selectors, which are reversibly responded by the changes of column temperature as well as pH of mobile phase. At pH 5, DNAs and humic matters were completely adsorbed on the polymer adsorbent at room temperature, while up to 90% of the adsorbed DNAs were released and recovered at 70 degrees C with no release of adsorbed humic matters. Cleaning up of the polymer adsorbent could be performed by washing the adsorbed humic matters with alkaline mobile phase (pH 9) to recover those and realize repeatable use of the adsorbent.

Adsorption↗

PubMed2002

Humic acid induces the generation of nitric oxide in human umbilical vein endothelial cells: stimulation of nitric oxide synthase during cell injury.

Humic acid (HA) has been implicated as an etiological factor in the peripheral vasculopathy of blackfoot disease (BFD). In this study, we examined the effects of HA upon the generation of nitric oxide (NO) during the process of lethal cell injury in cultured human umbilical vein endothelial cells (HUVECs). NO production was measured by the formation of nitrite (NO(2)(-)), the stable end-metabolite of NO. Cell death was assessed by measuring the release of intracellular lactate dehydrogenase (LDH). Treatment HUVECs with HA at a concentration of 50, 100, and 200 microg/ml concentration-dependently increased nitrite levels, reaching a peak at 12 h subsequent to HA treatment, with a maximal response of approximately 400 pmole nitrite (from 1 x 10(4) cells). HA-induced nitrite formation was blocked completely by N(G)-nitro-L-arginine methyl ester (L-NAME) and also by N(G)-methyl-L-arginine (L-NMA), both being specific inhibitors of NO synthase. The LDH released from endothelial cells was evoked at from 24 h after the addition of HA (50, 100, 200 microg/ml) in a concentration- and time-dependent manner. The HA-induced LDH release was also reduced by the presence of both L-NAME and L-NMA. The addition of Ca(2+) chelator (BAPTA) inhibited both nitrite formation and LDH release by HA. Moreover, the antioxidants (superoxide dismutase, vitamin C, vitamin E) and protein kinase inhibitor (H7) effectively suppressed HA-induced nitrite formation. These results suggest that HA treatment of endothelial cells stimulates NO production, which can elicit cell injury via the stimulation of Ca(2+)-dependent NO synthase activity by increasing cytosolic Ca(2+) levels. Because the destruction of endothelial cells has been implicated in triggering the onset of BFD, the induction of excessive levels of NO and consequent endothelial-cell injury may be important to the etiology of HA-induced vascular disorders associated with BFD for humans.

Antioxidants↗

PubMed1999

Humic acid-mediated oxidative damages to human erythrocytes: a possible mechanism leading to anemia in Blackfoot disease.

Humic acid (HA) has been proposed as a factor that causes Blackfoot disease, an endemic peripheral vascular disease prevailing in the southwest coast of Taiwan. However, the relationship between HA and anemia associated with Blackfoot disease remains unclear. In this study, we showed that HA imposed damages on human red blood cells (RBCs), which were manifested as reduction in deformability of RBCs and hemolysis. At concentrations ranging from 10 to 100 microg/ml, HA caused lipid peroxidation in a dose-dependent manner. Such changes were accompanied by a depletion of glutathione and a reduction in activities of the antioxidant enzymes including catalase, superoxide dismutase, and glucose-6-phosphate dehydrogenase. These results indicate that HA initiates oxidative stress on RBCs and results in their dysfunction. Consistent with our previous findings, the present study supports the notion that HA plays an important role in the pathogenesis of Blackfoot disease.

Anemia↗

PubMed1995

Subchronic application of humic acids and associated compounds provokes histological changes of goitre in the rat.

1. Different preparations of humic acids, a pyrogallol oxydation product (PYROP) and resorcinol were administered to male and female rats with the drinking water for 8 to 14 weeks. 2. By histometrical evaluation of the thyroid glands, an increase of the mean epithelial cell height of follicular epithelial cells was established in the 0.1% humic acid groups, 0.1% PYROP group and the 0.004% resorcinol groups. Females seemed to be more sensitive than males. Additionally, in some experiments, a decrease of the mean follicular diameter was found, which was the result of newly formed little follicles. The changes must be considered as a precursor of goitre. 3. In one of the experiments, in which circulating thyroid hormones were investigated, the serum thyroxine level in the male 0.1% humic acid group and the free thyroxine index in the female 0.1% humic group were diminished as compared to the control groups.

Animals↗