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PubMed2002

Leaching of metals from fly ashes in the presence of complexing agents.

The leachability of some metals (Al, As, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Ti, Zn) from fly ashes was studied in the presence of ethylenediamine tetraacetic acid (EDTA) and naturally occurring complexing agents-humic acids (HAs). Secondary complex-forming equilibria taking place in the leachates increase significantly the leached amounts of most metals. Kinetic experiments showed that almost the whole "available" amounts of metals are leached from fly ash within a time period of several hours (mostly within 20 h), with exceptions of matrix constituents (typically aluminium), which are released more slowly.

Chelating Agents↗

PubMed2002

Effects of competitive ions, humic acid, and pH on removal of ammonium and phosphorous from the synthetic industrial effluent by ion exchange resins.

The removal of the ammonium and phosphorous from the synthetic industrial effluent by the ion exchange resins was studied in this paper, aiming at the determination of the effects of competitive ions, humic acid, pH and resin amount. The kinetic experiments show that the equilibrium time for the removal of both contaminants in the absence and presence of the competing matters was 4 h. Na+ and K+ significantly reduced the ammonium removal percentage, while the existence of Mg2+, Ca2+ and humic acid also had a negative influence. Adsorption of ammonium ions in both absence and presence of Na+ and K+ observed the linear isotherm, however, it did not follow commonly used isotherms in the presence of Na+, K+, Mg2+, Ca2+ and humic acid. The phosphorous removal decreased in the presence of the competitive matters, such as Cl-, CO3(2-), SO4(2-) and humic acid. Higher pH can cause higher phosphorous removal percentage. A decrease in the solution pH was observed in the phosphorous removal experiments, possibly due to the ion exchange and the adsorption of OH-. Uptake of humic acid by the resins was observed. Finally, a series of fixed-bed experiments were performed, showing that the performance was dependent on the empty bed contact time (EBCT). Higher EBCT would cause higher bed volumes of both treated ammonium and phosphorous.

Humic Substances↗

PubMed2001

Influence of one or two successive annual applications of organic fertilisers on the enzyme activity of a soil under barley cultivation.

The effect of cow manure and two rates of addition of municipal solid waste (MSW) compost on the enzymatic activity of a soil supporting barley cultivation was studied and compared with mineral fertilisation (MF). The experiment was carried out in unirrigated land in field conditions for two years. One set of plots was fertilised only once, at the start of the experiment, while another set of plots was fertilised annually (before each sowing). In general, the organic amendments stimulated soil enzyme activity but mineral fertilisation did not. The annual addition of large quantities of MSW compost, in general, led to lower levels of enzyme activity than similar rates of amendment in the plots receiving a single addition, probably because of the toxic effect which the heavy metals incorporated with the MSW compost had on microbial development. In the second year, plot receiving a single application of organic amendment showed higher protease hydrolysing casein, beta-glucosidase and dehydrogenase activities than control or soil with mineral fertilisation. This implied that the addition of organic waste, and particularly MSW compost, had a catalysing effect in the soil which lasted for the following years. Barley yields obtained with organic amendments were, in general, similar to, or even higher, than those obtained with mineral fertilisation. The annual addition of high doses of compost had an inhibitory effect on enzyme activity and barley yield (compared with the results obtained with the low addition of compost) due to the negative effect of the heavy metals incorporated with the compost.

Agriculture↗

PubMed2002

The influence of humic acids derived from earthworm-processed organic wastes on plant growth.

Some effects of humic acids, formed during the breakdown of organic wastes by earthworms (vermicomposting), on plant growth were evaluated. In the first experiment, humic acids were extracted from pig manure vermicompost using the classic alkali/acid fractionation procedure and mixed with a soilless container medium (Metro-Mix 360), to provide a range of 0, 50, 100, 150, 200, 250, 500, 1,000, 2,000, and 4,000 mg of humate per kg of dry weight of container medium, and tomato seedlings were grown in the mixtures. In the second experiment, humates extracted from pig manure and food wastes vermicomposts were mixed with vermiculite to provide a range of 0, 50, 125, 250, 500, 1,000, and 4,000 mg of humate per kg of dry weight of the container medium, and cucumber seedlings were grown in the mixtures. Both tomato and cucumber seedlings were watered daily with a solution containing all nutrients required to ensure that any differences in growth responses were not nutrient-mediated. The incorporation of both types of vermicompost-derived humic acids, into either type of soilless plant growth media, increased the growth of tomato and cucumber plants significantly, in terms of plant heights, leaf areas, shoot and root dry weights. Plant growth increased with increasing concentrations of humic acids incorporated into the medium up to a certain proportion, but this differed according to the plant species, the source of the vermicompost, and the nature of the container medium. Plant growth tended to be increased by treatments of the plants with 50-500 mg/kg humic acids, but often decreased significantly when the concentrations of humic acids derived in the container medium exceeded 500-1,000 mg/kg. These growth responses were most probably due to hormone-like activity of humic acids from the vermicomposts or could have been due to plant growth hormones adsorbed onto the humates.

Animals↗

PubMed2002

Characterization of carex peat using extinction values of humic acids.

Recent developments in technology and soil science have drawn particular attention to peatlands and their behaviour, properties and utilisation. Further, characteristics of peat are very important in evaluating it as a plant growth medium. The objective of this study was to characterise a number of samples collected from different depths of five different profiles of Yeniçağa peat (carex) by measuring the organic carbon, total nitrogen, and extinction values (Er) of their humic acid fractions (HAs) in comparison with decomposition degrees. Peat samples having a high decomposition degree were near to the Er45 axis in the ordinate and had high Er67 values, whereas peats with low decomposition degree were far from the Er45 axis and had low Er67 values.

Humic Substances↗

PubMed2003

Quantitative estimation of peat, brown coal and lignite humic acids using chemical parameters, 1H-NMR and DTA analyses.

Humic acids extracted from peats (P), brown coals (BC) and lignites (L), were characterized using different (chemical, 1H-nuclear magnetic resonance spectroscopy and differential thermal analysis) techniques. Fourteen variables were obtained from these analyses and only five were selected because uncorrelated in multiple partial correlation. The chosen variables were C concentration, aliphatic and aromatic components and the heat of reaction of the second exothermic peak. The multivariate discriminant analysis was performed on these variables and a discriminant function was obtained which was able to efficiently separate the P, BC and L. This function enables simple predictions on samples of unknown origin. The straightforward method proposed and the results obtained are discussed.

Coal↗

PubMed2003

Use of silica-immobilized humin for heavy metal removal from aqueous solution under flow conditions.

Humin extracted from Sphagnum peat moss was immobilized in a silica matrix and column experiments were performed in order to evaluate the removal and recovery of metal ions from aqueous solution under flow conditions. These experiments also allowed testing the recycling capacity of the column. Single-element solutions of Cu(II) and Pb(II), and a multi-metal solution containing Cd(II), Cu(II), Pb(II), Ni(II), and Cr(III) were passed through the columns at a flow rate of 2 ml/min. A 0.5 M sodium citrate solution was used as the stripping agent in the metal-ion recovery process. Humin immobilized in the silica matrix exhibited a similar, and in some cases, even a higher capacity than other biosorbents for the removal of metal ions from aqueous solutions under flow conditions. The sodium citrate was effective in removing Cu(II), Pb(II), Cd(II), and Ni(II) from the metal saturated column. The selectivity of the immobilized biomass was as follows: Cr(III)>Pb(II)>Cu(II)>Cd(II)>Ni(II). This investigation provides a new, environmentally friendly and cost-effective possibility to clean up heavy-metal contaminated wastewaters by using the new silica-immobilized humin material.

Adsorption↗

PubMed2003

Recoupled long-range C-H dipolar dephasing in solid-state NMR, and its use for spectral selection of fused aromatic rings.

This work introduces a simple new solid-state 13C NMR method for distinguishing various types of aromatic residues, e.g. those of lignin from fused rings of charcoal. It is based on long-range dipolar dephasing, which is achieved by recoupling of long-range C-H dipolar interactions, using two 1H 180 degrees pulses per rotation period. This speeds up dephasing of unprotonated carbon signals approximately threefold compared to standard dipolar dephasing without recoupling and thus provides much more efficient differential dephasing. It also reduces the effects of spinning-speed dependent effective proton-proton dipolar couplings on the heteronuclear dephasing. Signals of unprotonated carbons with two or more protons at a two-bond distance dephase to <3% within less than 0.9 ms, significantly faster than those of aromatic sites separated from the nearest proton by three or more bonds. Differential dephasing among different unprotonated carbons is demonstrated in a substituted anthraquinone and 3-methoxy benzamide. The data yield a calibration curve for converting the dephasing rates into estimated distances from the carbon to the nearest protons. This can be used for peak assignment in heavily substituted or fused aromatic molecules. Compared to lignin, slow dephasing is observed for the aromatic carbons in wood charcoal, and even slower for inorganic carbonate. Direct 13C polarization is used on these structurally complex samples to prevent loss of the signals of interest, which by design originate from carbons that are distant from protons and therefore crosspolarize poorly. In natural organic matter such as humic acids, this combination of recoupled dipolar dephasing and direct polarization at 7-kHz MAS enables selective observation of signals from fused rings that are characteristic of charcoal.

Anisotropy↗

PubMed2001

Human cell mutagenicity of chlorinated and unchlorinated water and the disinfection byproduct 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX).

Extracts of three water samples--humic acid-enriched water-both peatland water and drinking water, both with and without chlorination were tested for mutagenicity at the tk locus in MCL-5 cells, a line of human B-lymphoblastoid cells that express cytochrome P450 enzymes and microsomal epoxide hydrolase. Our results show that chlorination caused a 5.5-fold increase (P<0.0001) in the mutagenicity of the humic acid-enriched water. The unchlorinated peatland water was mutagenic at the two highest doses (240 and 480 microg equivalent total organic carbon (TOC)/ml), possibly due to polycyclic aromatic hydrocarbons (PAH) that were measured in the peat. In contrast, the chlorinated peatland water was non-mutagenic at low doses, while at the highest dose (240 microg equivalent TOC/ml) the sample was so toxic that an insufficient number of cells survived treatment to allow plating. The chlorinated and unchlorinated drinking water were both non-mutagenic. 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a potent bacterial mutagen and chlorine-disinfection byproduct, was also tested in MCL-5 cells as well as in two other human B-lymphoblastoid cell-lines, AHH-1 TK+/- and h1A1v2 cells, which differ from each other and from MCL-5 cells in the amounts of cytochrome P450 enzymes they can express. MX was mutagenic to all three cell-lines, but there was no apparent correlation between cytochrome P450 enzyme expression and the mutagenicity of MX. Overall, our results show that samples of chlorinated humic acid-enriched water and MX, a model chlorine-disinfection byproduct, are moderately mutagenic to human cells.

B-Lymphocytes↗

PubMed2001

Infrared and chemometrics study of the interaction between heavy metals and organic matter in soils.

The study of the behavior of heavy metals in soils requires the knowledge of the complexation between soil constituents and metals and this information is not available from conventional analytical techniques such as atomic absorption. Since metals do not absorb mid infrared radiation, we wanted to characterize them using their interaction with the organic matter of soils. The use of chemometrics treatment of the spectroscopic data has demonstrated firstly that the interaction between soil constituents and metals takes place preferentially via organic matter, secondly the high difference between the complexation of lead and zinc into organic matter should be noted. The study of the infrared spectra shows that two bands at 1670-1690 and 1710 cm(-1) vary according to the concentration of lead, which seems to be preferentially complexed by the salicylate functionality.

France↗

PubMed2000

Electron paramagnetic resonance (EPR) studies on stable and transient radicals in humic acids from compost, soil, peat and brown coal.

Quantitative EPR method was applied to characterise four types of humic acids (HA) derived from composts, soil, peat and soft brown coal. For each sample of HA the level of native (indigenous) radicals was estimated. Interactions of the HA with various gaseous agents and organic solvents were investigated. Strong effects of gaseous ammonia and aliphatic amines on spin concentration enhancement were observed; additionally, higher values of g-value were found to be associated with the formed 'transient' radicals. Correlation of copper(II) ions uptake by different HA with effect diminishing primary spin concentration was established. It was recognised that the radical centres, which are enhanced by 'ammonia effect' are quenched in the formed HA-Cu(II) complexes. The both opposite effects are competitive from each other, where 'copper(II) quenching effect' prevails. Reaction of nitrogen dioxide with the humic acids was also examined. The presence of diketones and/or other compounds with active methylene group results in formation of the iminoxy radicals; these radicals are immobilized in the solid (macromolecular) matrix of the humic acids.

Coal↗

PubMed2002

Effect of long-term silver exposure on survival and ionoregulatory development in rainbow trout (Oncorhynchus mykiss) embryos and larvae, in the presence and absence of added dissolved organic matter.

Developing rainbow trout were chronically exposed to silver (as AgNO(3)) from fertilization to swim-up, in moderately hard water (120 mg CaCO(3)(x)l(-1)) in the presence and absence of an additional 12 mg C/L of dissolved organic carbon (DOC, as humic acid, Aldrich). Nominal silver concentrations were 0, 0.1 and 10 microg l(-1) total silver in a flow-through set-up maintained at 12 degrees C. The objectives of the study were to investigate the possible protective effects of DOC on growth, mortality, time to hatch and swim-up, and sublethal ionoregulatory disturbances during chronic exposure to ionic silver. Throughout development, there was a large increase in % daily mortality at 10 microg(x)l(-1) total silver (in the absence of DOC), that was associated with an ionoregulatory disturbance, in particular a 35% reduction in whole body Na(+) just prior to hatch. At nominal 10 microg(x)l(-1) total silver, the presence of additional DOC (reducing dissolved silver to 4.7+/-0.3 microg l(-1)) resulted in a significant reduction in % daily mortality up to hatch, demonstrating a protective effect of DOC. Interestingly, DOC did not appear to mitigate the ionoregulatory disturbance, with the exception of whole body [Cl(-)] on day 44 of exposure. Exposure to 0.1 microg(x)l(-1) total silver (in the absence of DOC) resulted in a statistically significant reduction in growth, and DOC did not prevent an ionoregulatory disturbance [based upon (J(in) Na(+)), whole body Na(+),K(+) ATPase activity and whole body (Na(+))] at this silver concentration relative to controls+DOC. DOC exerted a direct effect on growth and ionoregulatory development that complicates interpretation of the data, however, these data indicate that protective effects of DOC (in the form of Aldrich humic acid) during chronic silver exposure appear to be less than that observed during acute exposure. The ultimate goal of this and future studies is to develop a model that can predict chronic toxicity on a site-specific basis, taking into account protective effects of various ligands present in different waters, as is presently being employed for some metals during acute exposure.

Animals↗

PubMed2002

Influence of dissolved humic acid on hydrophobic chemical uptake in juvenile rainbow trout.

This study measured the chemical uptake of three hydrophobic chemicals (1,2,4-trichlorobenzene (1,2,4-TCB), 1,2,3,4,5-pentachlorobenzene (PeCB) and 2,2',4,4',6,6'-hexachlorobiphenyl (HCBP) with differing octanol-water partition coefficients (log K(ow) values of 3.95, 5.05 and 7.55, respectively) in juvenile rainbow trout (Oncorhynchus mykiss) after 2-day and 4-day aqueous exposures. Because of the affinity of hydrophobic compounds for dissolved organic carbon (DOC) and previous work demonstrating that fish gills take up these three hydrophobic chemicals, we predicted that chemical uptake into the fish would be lowered by the addition of humic acid to the water (1.54, 4.81 and 14.3 mg/l) compared with control fish (no humic acid added to the water). As predicted, humic acid concentrations of >or=4.81 mg/l significantly reduced the whole body concentrations of all three chemicals when compared with 1.54 mg/l humic acid. This effect of humic acid was greatest for HCBP, the chemical with the highest log K(ow), such that chemical uptake was reduced by 3.4-fold for 14.3 mg/l humic acid compared with the control exposure. However, an unexpected finding was that, compared with the control exposure, the lowest concentration of humic acid tested (1.54 mg/l humic acid) significantly increased chemical uptake by up to 112% for the two chemicals with the lower log K(ow), PeCB and 1,2,4-TCB, and did not affect uptake of the high log K(ow) chemical HCBP. We conclude that the ability of DOC to inhibit aqueous uptake of hydrophobic chemicals was dependent on both the concentration of DOC and the log K(ow) of the chemical, but that low humic acid concentrations of approximately 1.5 mg/l can significantly increase uptake of certain chemicals with a log K(ow) between 4 and 5.

Animals↗

PubMed2000

Direct in situ measurements of labile inorganic and organically bound metal species in synthetic solutions and natural waters using diffusive gradients in thin films.

The emerging technique of DGT (diffusive gradients in thin films) is shown to be capable of performing new speciation measurements in situ in natural waters. In DGT, metals are bound to a resin layer after passing through a well-defined diffusion layer. Cd was measured in solutions containing glycine, EDTA, and fulvic (FA) and humic acids (HA) by atomic absorption spectroscopy (AAS), anodic stripping voltammetry (ASV), and DGT. DGT measured similar labile fractions to ASV, with detailed differences being consistent with a thicker diffusion layer allowing more dissociation of labile complexes and a slower diffusion of FA and HA complexes through the gel. When single measurements are made in complex solutions with DGT, precise quantification is impossible due to uncertainties concerning the distribution of species with different diffusion coefficients. A new procedure was proposed based on the advantage of DGT of being able to control the pore size of the diffusive gel layer. Small (inorganic) species diffuse freely through all gels but larger FA and HA (organic) complexes diffuse less freely in more constrained gels. When measurements were made on known solutions of Cu and FA or HA, it was possible to quantify the inorganic and organic species separately. They agreed well with predictions made using the WHAM speciation code. Multiple DGT units were also deployed in situ in a stream with high dissolved organic carbon (14.6 mg/L). The systematic differences between the devices with different gel compositions enabled determination, for the first time, of the in situ concentrations of both labile inorganic and organic species in natural water. A single DGT device with a constrained gel can be used to quantify inorganic species directly, providing absolute accuracy is not required. This ability of DGT to measure well-defined fractions of metals in situ using a simple device gives it considerable potential as a regulatory tool. A direct speciation measurement may be preferable to modeling approaches which require diverse input data that are difficult to determine.

Benzopyrans↗

PubMed2000

Tandem-cartridge solid-phase extraction followed by GC/MS analysis for measuring partition coefficients of association of polycyclic aromatic hydrocarbons to humic acid.

A tandem-cartridge solid-phase extraction system combining reversed-phase separation and dynamic ion exchange followed by GC/MS analysis was studied for measuring partition coefficients (Kdoc) of association of polycyclic aromatic hydrocarbons (PAHs) to humic acid. Time course batch experiments revealed that the association of PAHs to humic acid included a slow stage with equilibrium time of 5-7 days. The disequlibrium and retention of the PAH-humic acid associate during reversed-phase separation lead to systematic negative error for the measured partition coefficients; more accurate results were achieved with a three-cartridge tandem system in which the negative error was assessed and corrected via the PAH analytes measured on the second reversed-phase cartridge. The potential and advantages of use of C18 disk cartridges instead of conventional C18 cartridges to set up the tandem system for measuring the partition coefficients were also studied. With the tandem-cartridge system, the measured partition coefficients did not change with most experimental conditions, but a trend of decreasing partition coefficients with humic acid concentration was observed, implying possible nonlinear association of the PAHs and humic acid.

Environmental Pollutants↗

PubMed2002

Measuring and modeling zinc and cadmium binding by humic acid.

Free metal ions in aqueous and terrestrial systems strongly influence bioavailability and toxicity. Most analytical techniques determine the total metal concentration, including the metal ions bound by dissolved organic matter. Ion activity can be measured with ion-specific electrodes (ISEs) for some metals, but an electrode for Zn is not commercially available. As a result, very few data are available on Zn binding by natural dissolved organic matter. The aim of this study is to determine free Zn concentrations in purified humic acid solutions using the recently developed Donnan membrane technique. However, several analytical aspects of the Donnan membrane technique had to be clarified before reliable data could be composed. Cd was chosen for validation. This study shows that free Cd concentrations as measured by the Donnan membrane technique agreed well with Cd ISE measurements. It is also shown that the Donnan membrane technique could be used at high pH. The Donnan membrane technique provided consistent results in a range of p[Cd2+] = 3-9 and p[Zn2+] = 3-8 at pH 4, 6, and 8. Metal speciation in humic acid solutions was also calculated with the consistent NICA-Donnan model using generic parameters. The model could excellently describe the experimental data without adjusting any of the parameters (R2Cd = 0.971, R2Zn = 0.988).

Algorithms↗

PubMed2002

Hollow fiber-protected liquid-phase microextraction of triazine herbicides.

A new microextraction technique termed hollow fiber-protected liquid-phase microextraction (LPME) was developed. Triazines were employed as model compounds to assess the extraction procedure and were determined by gas chromatography/mass spectrometry. Toluene functioned as both the extraction solvent and the impregnation solvent. Some important extraction parameters, such as effect of salt, agitation, pH, and exposure time were optimized. The new method provided good average enrichment factors of > 150 for eight analytes, good repeatability (RSDs <3.50%, n = 7), and good linearity (r2 > or = 0.9995) for spiked deionized water samples. The limits of detection (LODs) were in the range of 0.007-0.063 microg/L (S/N = 3) under selected ion monitoring mode. In addition to enrichment, hollow fiber-protected LPME also served as a technique for sample cleanup because of the selectivity of the membrane, which prevented large molecules and extraneous materials, such as humic acids in solution, from being extracted. The utilization of this procedure in the extraction of a slurry sample (mixture of soil and water) also gave good precision (RSDs <5.00%, n = 3) and LODs (0.04-0.18 microg/L, S/N = 3). Finally, the comparison of the new method with the static solvent drop LPME and solid-phase microextraction was performed. The results demonstrated that hollow fiber-protected LPME was a fast, accurate, and stable sample pretreatment method that gave very good enrichment factors for the extraction of triazine herbicides from aqueous or slurry samples.

Gas Chromatography-Mass Spectrometry↗

PubMed2002

High-resolution Fourier transform ion cyclotron resonance mass spectrometry of humic and fulvic acids: improvements and comparisons.

Full structural characterization of complex mixtures such as humic acid extracts has been elusive because of insufficient compound resolution with conventional techniques. Using electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry, we were able to resolve individual compounds within humic and fulvic acid mixtures (mass resolving power approximately 80000 at 300 m/z). We examined two samples in detail: (1) dissolved organic matter (primarily fulvic acids) from Suwannee River, GA, and (2) a humic acid extract from a degraded wood collected on Mt. Rainier, WA. Sample conditions (such as solvent, pH, and concentration) and instrument parameters (such as source voltages, trapping potentials, and excitation parameters) were optimized to yield the highest mass resolving power with the least mass discrimination in positive ion mode. High resolving power was achieved with low ion densities combined with coadding numerous scans. The increased resolution allowed molecular-level comparisons of the two samples which in turn could be used to estimate the relative similarity of individual compound distribution as well as an indication of the dominant diagenetic processes in the two source environments.

Benzopyrans↗