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The East Siberian Arctic Shelf (ESAS) is the broadest and shallowest continental shelf in the World Ocean. It is characterized by both the highest rate of coastal erosion and a large volume of riverine input of terrigenous dissolved organic matter (DOM). DOM plays a significant role in marine aquatic ecosystems. The colored (chromophoric) fraction of DOM (CDOM) directly affects the quantity and spectral quality of available light, thereby impacting both primary production and UV exposure in aquatic ecosystems. A multi-year study of DOM optical parameters and the spectral characteristics of the DOM chromophoric fraction were carried out in the vast ESAS in the summer-fall seasons. The spectral characteristics of CDOM were applied to identify different biogeochemical provinces in the surveyed area. The analysis of CDOM spectral characteristics showed that the major part of the Laptev and East Siberian Sea shelf (making up the ESAS) is influenced by terrigenous DOM with high aromaticity, stemming from riverine discharge. The atmospheric circulation regime is the dominant factor controlling CDOM spatial distribution on the ESAS. A western and an eastern regime of ESAS, separated around 165–170° E, were identified with distinctly different DOM optical properties. Strong correlation between DOC and CDOM concentrations in surface shelf waters influenced by terrigenous discharge indicates feasibility of estimating DOC content from the CDOM assessed in situ using a WETStar fluorometer. The direct estimation of optical characteristics of DOM in ESAS waters provided by this study will also be useful for validation and calibration of remote sensing data.

Humic acids (HA) are natural organic compounds that are important components of organic matter. The accumulation, distribution, and fate of tritium-labeled HA prepared from coal were analyzed using wheat (Triticum aestivum L.) seedlings. There was a period of rapid accumulation of HA followed by a slower one in the period from 1 to 24h. There was a significant decrease in HA accumulation at low temperature, indicating that the slower rate of HA accumulation represented a membrane-mediated process. HA distribution in plant tissues was analyzed using autoradiography. In all cases, HA concentration was considerably higher in the roots than in the shoots. Detailed examination of autoradiograms showed that there was preferential accumulation of HA in the apices of roots and shoots of wheat seedlings. Lipid fractions were extracted from seedlings and analyzed with thin layer chromatography and gas chromatography–mass spectrometry. These analyses revealed that labeled HA were present in the neutral lipid fraction consisting mainly of alkanes and alkenes, which are usually found in plant waxes, associated with the cuticle and suberized tissues. Based on these data, it is suggested that HA-derived hydrocarbons may be used in wax biosynthesis. This role could explain the mitigating activity of humic substances under stress conditions.

The problem of permeable reactive barrier (PRB) capture and release behavior is investigated by means of an approximate analytical approach exploring the invariance of steady-state solutions of the advection–dispersion equation to conformal mapping. PRB configurations considered are doubly-symmetric funnel-and-gate as well as less frequent drain-and-gate systems. The effect of aquifer heterogeneity on contaminant plume spreading is hereby incorporated through an effective transverse macro-dispersion coefficient, which has to be known. Results are normalized and graphically represented in terms of a relative capture efficiency M of contaminant mass or groundwater passing a control plane (transect) at a sufficient distance up-stream of a PRB as to comply with underlying assumptions. Factors of safety FS are given as the ratios of required capture width under advective–dispersive and purely advective transport for achieving equal capture efficiency M. It is found that M also applies to the release behavior down-stream of a PRB, i.e., it describes the spreading and dilution of PRB treated groundwater possibly containing incompletely remediated contamination and/or remediation reaction products. Hypothetical examples are given to demonstrate results.

The possible use of the concentration of intracellular adenosine triphosphate (ATP) as a parameter enabling quick and adequate evaluation of the metabolic activity of methanogenic cells was demonstrated in the work. This approach was used to analyze the effect of introducing potassium humate and fulvic acids (1&ndash, 10 g/L) into media with four different methanogenic consortia producing biogas. The ATP concentration was analyzed by the bioluminescent luciferin&ndash, luciferase method at the beginning and end of the process. During the entire process, the biogas composition, biogas efficiency, and the kinetics of methanogenesis in the presence of humic compounds were determined. The increase in the concentration of potassium humate led to a decrease in the overall energy status of the cells and reduced methanogenesis efficiency. However, fulvic acids introduced into the media stimulated methanogenesis in half of the tested consortia, which was accompanied by an increase in ATP concentration in cell samples. So, a positive correlation between the metabolic activity of cells in biogas formation and the concentration of ATP was observed. ATP concentration control appears to be an attractive tool for finding compounds that suppress methanogenesis in landfills.

Purpose Humic substances (HS) being natural polyelectrolyte macromolecules with complex and disordered molecular structures are a key component of the terrestrial ecosystem. They have remarkable influence on environmental behavior of iron, the essential nutrient for plants. They might be considered as environmental friendly iron deficiency correctors free of synthetic iron (III) chelates disadvantages. The main goal of this study was to obtain water-soluble iron-rich humic compounds (IRHCs) and to evaluate their efficiency as chlorosis correctors.

Mossbauer spectroscopy of frozen aqueous solutions was demonstrated as an efficient stepwise control technique in the new one-pot synthesis of biocompatible feroxyhyte (δ ′-FeOOH) nanoparticles in situ stabilized by humic substances. Formation of ultradispersed Fe(OH)2 as an intermediate product and its interaction with humic substances were ascertained. The interaction of the surface of Fe(OH)2 with humic substances was considered as a starting point in the mechanism of in situ stabilization and further growth control of humic-stabilized feroxyhyte nanoparticles.

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

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.

a b s t r a c t In this study we explored a possibility for enhancing aqueous sorption of humic substances (HS) onto hydroxylated surfaces (e.g., silica gel) by increasing modification rate of their most abundant functional groups - carboxyls with mineral-adhesive alkoxysilyl moieties. The synthesis included treatment of dried humic material with 3-aminopropyl trimethoxy silane (APTS) capable of forming amide bonds with carboxyl groups of HS under anhydrous conditions. The reaction was run at six different HS to APTS ratio for achieving different modification degrees of the carboxyl groups in the humic backbone. The obtained derivatives were characterized using elemental analysis, 13C NMR Spectroscopy, Fourier transform infrared spectroscopy, and size exclusion chromatography that confirmed quantitative incor- poration of alkoxysilyl-moieties into HS structure. Aqueous adsorption was investigated in 0.028 M phosphate buffer using silica gel as a surrogate for mineral surface. Both distribution coefficients as well adsorption capacities paralleled the amount of alkoxysilyl-moieties incorporated into backbone of the parental HS. The adsorption capacity reached its maximum value of 210 mg of HS per g of SiO2 for the APTS derivative synthesized at the equimolar reagent ratio. This value was comparable to the amount of the same HS immobilized onto the APTS-treated silica gel (265 mg of HS per g of SiO2). Adsorption of alkoxysilyl-derivatives was found to be irreversible under conditions studied. Conclusively, we believe that the directed modification of HS by incorporating alkoxysilyl-moieties is well suited for producing humic derivatives with controllable affinity for aqueous sorption onto hydroxylated surfaces.

The structure of humic acids (HAs) in zonal soil types—soddy-podzolic soils (two samples), gray forest soil (one sample), and chernozems (two samples)—was quantitatively studied by 13C NMR spectros-copy. In the series considered, the content of unsubstituted carbon in the aromatic fragments of HAs increased, and the fraction of unsubstituted aliphatic structures decreased. HAs of soddy-podzolic soils were found to be enriched with carbohydrate fragments compared to HAs of chernozems and gray forest soil. The carbon skeleton of HAs from typical rich chernozem contained significantly more aliphatic and carbohydrate fragments compared to typical chernozem, which probably reflected the lower degree of HA transformation in rich chernozem.

Elemental analysis of water-soluble humic substances extracted from three sod-podzolic soils was carried out. Data on elemental composition were compared to those of humic and fulvic acids extracted from the same soils.

The alteration of organic matter from three sod-podzolic soils in the course of the extraction of water-soluble humic substances was studied by means of size-exclusion chromatography using a combined UV-DOC detector. A comparison of water-soluble humic substances with humic and fulvic acids extracted from the same soils was carried out.

An approach to optimizing conditions of acquiring Electrospray Ionization Fourier Transform Ion Cyclotron Resonance mass spectra (ESI FTICR MS) was suggested. This method was employed to study the influence of cone voltage and the composition of the solution on peak intensity in ESI FTICR mass spectra of natural water humic substances. A presence of water in methanol solution was shown to reduce signal intensity significantly. The highest integral intensity of peaks selected was reached on 110 mg/l sample solution in acetonitrile and cone voltage 3.0 kV. The number of peaks to which molecular formulas were assigned, including doubly-charged peaks, was increased using these conditions.

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

Preparations of humic acids (HAs) were isolated from a gray forest soil by sequential alkaline extraction. From a sample of 500 g, HA preparations of 2.24, 0.23, and 0.20 g were obtained from the first, second, and third alkaline extracts, respectively. The structure of the preparations was determined by 13 C NMR spectroscopy. At each next extraction step, the portion of aliphatic fragments in the HA preparations increased and the content of aromatic structures decreased. The conclusion was drawn that a single extraction is sufficient for obtaining a representative HA sample.

It was shown with the isolation of a humic acid (HA) preparation from a typical chernozem by sequential alkaline extraction as an example that the preparative yield of HAs decreased at each sequential extraction stage by 3–4 times. On the basis of studying the obtained preparations using elemental analysis, gel-penetration chromatography, and 13C NMR spectroscopy, the tendencies of the changes in the structural-group and molecular-weight compositions of the HAs from one extraction stage to the next one were revealed. The conclusion was drawn that a single extraction is sufficient for obtaining a representative HA sample.

A range of labeled humic substances was obtained by the tritium thermal activation method. The high specific radioactivity and radiochemical purity allowed direct determination of the hydrophobicity and surface activity of humic substances, and investigation of the behavior of humic substances in bacteria and plants.

Natural organic matter as complex biogeochemical non-repetitive material was investigated with ion mobility mass spectrometry (IMS) and ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) approaches in order to unravel the existence of multiply charged state constituents. Hereby we describe and assign the potential molecular formulae of these doubly charged species, derived from FTICR-MS, and the existence of these species was confirmed via IMS. The parallel application of these powerful techniques enabled the boundaries of the understanding of natural organic matter to be pushed further.

The effect of humic acids (HA) on neptunium redox behavior and sorption onto hematite, -Fe2O3, and goethite, -FeOOH, colloids was established in batch sorption experiments that were carried out in broad pH interval. The sorption isotherms were provided for two samples of HA: commercial sample of leonardite humic acid and its hydroquinone-enriched derivative obtained using formaldehyde copolycondensation. The distribution of Np fitted the distribution of hydroquinone-enriched HA at low pH values in case of both solids while the influence of parent HA on Np sorption was negligible. This is due to Np(V) reduction upon interaction with hydroquinone-enriched derivative having higher reducing capacity compared to the parent HA. The order of components addition was found to be significant for Np retention. © 2007 Elsevier B.V. All rights reserved.

Humic substances play an important role in the speciation of actinides in the environment due to complexing, redox and sorptive interactions. This work is devoted to plutonium(V) reduction studies in solutions containing different humic substances, eluted from Mollisol and Sod-podzolic soil samples, as compared to real Pu distribution is contaminated soils. On the basis of kinetic curve slopes, the reducing ability is increased in the order: HA < FA ∼ low molecular weight fraction. The data obtained show that the different humic compounds play different roles in Pu(V) migration ability due to differing reducing and complexing properties.

Alkoxysilylated humic derivatives were used to create covalently bound humic coatings on silica gel. The corresponding reaction was conducted in an aqueous milieu that was feasible due to the water solubility of these derivatives. The alkoxysilylated humic derivatives were obtained by alkoxysilylation of leonardite humic acid (HA) and hydroquinone-modified HA (HQ) with enhanced redox properties. The silica gel coated with covalently bound HA and HQ was tested for sequestration of aqueous Np(V) and Pu(V) under anaerobic conditions. Greater sequestration with respect to Pu(V) (up to 97%) as compared to Np(V) (up to 60%) was demonstrated for samples of silica gel coated with HA and HQ, whereas sorption of both actinides on pure silica gel did not exceed 20%. Results provide bench-scale proof that alkoxysilylated humic derivatives can be used as reagents for the in situ installation of permeable reactive barriers designed to remediate actinide-contaminated groundwater.

Natural humic materials are known to cause a reduction of penta- and hexavalent plutonium; however, contradicting results have been previously reported for neptunium. The goal of this study was to determine if incorporation of additional reducing centers into humic structure would yield material with enhanced reducing performance with respect to higher valent actinides, nominally, Pu(V) and Np(V). Hydroquinone-moieties were used as the redox centers. They were incorporated into humic structures using formaldehyde condensation at different monomer-to-humic ratios to obtain materials of different reducing properties. Reduction of model actinides by the hydroquinone-enriched humic materials was studied under both oxic and anoxic conditions at acidic and neutral pH values. Redox speciation of plutonium and neptunium was monitored using solvent extraction techniques and liquid scintillation counting. It was shown that both nonmodified leonardite humic acid and all the obtained derivatives were able to reduce Pu(V) quantitatively both at neutral and acidic pH and under oxic and anoxic conditions. The reduction rate increased with an increase in the degree of modification of the humic material and reached its maximum for HQ500 derivative. For neptunium, reduction was observed only under anoxic conditions at acidic pH. The hydroquinone-modified derivatives had much higher reducing performance when compared to nonmodified leonardite humic acid. The results obtained show good prospects for a use of hydroquinone-modified humic materials as reactive agents for remediation of actinide contaminated aquifers.

Actinides in their higher valence states (e.g., MO2+ and MO2(2+), where M can be Np, Pu, etc) possess a higher potential for migration and in turn pose a substantial environmental threat. To minimize this potential for migration, reducing them to lower oxidation states (e.g., their tetravalent state) can be an attractive and efficient remedial process. These lower oxidation states are often much less soluble in natural aqueous media and are, therefore, less mobile in the environment. The research presented here focuses on assessing the performance of quinonoid-enriched humic derivatives with regardsto complexing and/ or reducing Np(V) present in solution. These "designer" humics are essentially derived reducing agents that can serve as reactive components of a novel humic-based remediation technology. The derivatives are obtained by incorporating different quinonoid-moieties into leonardite humic acids. Five quinonoid-derivatives are tested in this work and all five prove more effective as reducing agents for selected actinides than the parent leonardite humic acid, and the hydroquinone derivatives are better than the catechol derivatives. The reduction kinetics and the Np(V) species formed with the different derivatives are studied via a batch mode using near-infrared (NIR)-spectroscopy. Np(V) reduction by the humic derivatives under anoxic conditions at 293 K and at pH 4.7 obeys first-order kinetics. Rate constants range from 1.70 x 10(-6) (parent humic acid) to 1.06 x 10(-5) sec(-1) (derivative with maximum hydroquinone content). Stability constants for Np(V)-humic complexes calculated from spectroscopic data produce corresponding Logbeta values of 2.3 for parent humic acid and values ranging from 2.5 to 3.2 at pH 4.7 and from 3.3 to 3.7 at pH 7.4 for humic derivatives. Maximum constants are observed for hydroquinone-enriched derivatives. It is concluded that among the humic derivatives tested, the hydroquinone-enriched ones are the most useful for addressing remedial needs of actinide-contaminated aquifers.

The spatial moments of a contaminant plume undergoing bio-attenuation are coupled to the moments of microbial populations effecting that attenuation. In this paper, a scalable inverse method is developed for estimating field-scale Monod parameters such as the maximum microbial growth rate (μmax), the contaminant half saturation coefficient (Ks), and the contaminant yield coefficient (Ys). The method uses spatial moments that characterize the distribution of dissolved contaminant and active microbial biomass in the aquifer. A finite element model is used to generate hypothetical field-scale data to test the method under both homogeneous and heterogeneous aquifer conditions. Two general cases are examined. In the first, Monod parameters are estimated where it is assumed a microbial population comprised of a single bacterial species is attenuating one contaminant (e.g., an electron donor and an electron acceptor). In a second case, contaminant attenuation is attributed to a microbial consortium comprised of two microbial species, and Monod parameters for both species are estimated. Results indicate the inverse method is only slightly sensitive to aquifer heterogeneity and that estimation errors decrease as the sampling time interval decreases with respect to the groundwater travel time between sample locations. Optimum conditions for applying the scalable inverse method in both space and time are investigated under both homogeneous and heterogeneous aquifer conditions.

The products of the oxidative coupling of phenols are frequently used as synthetic analogues to natural humic substances (HS) for biomedical research. However, their molecular compositions and exact structures remain largely unknown. The objective of this study was to develop a novel approach for the molecular-level analysis of phenolic polymerisates that is capable of inventorying molecular constituents and resolving their distinct structural formulas. For this purpose, we have synthesized the model HS using the oxidative coupling of a specifically designed phenylpropanoic monomer, 3-(4-hydroxy-3-methoxyphenyl)-3-oxopropionic acid, to hydroquinone. We have characterized the synthesized model HS using high resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), (1)H NMR spectroscopy, and controllable hydrogen/deuterium (H/D) exchange. We succeeded in the molecular inventory of the model HS. The assigned molecular formulas occupied the substantial space of CHO compositions in the Van Krevelen diagram with a maximum density found in the regions of tannins and lignins, resembling those of natural HS. To identify the exact structural formulas of the individual constituents in the model HS, we have applied selective H/D exchange of non-labile backbone protons by a choice of basic or acidic catalytic conditions followed by FTICR MS. The determined formulas allowed us to verify the proposed pathways of hydroxylation and carboxylation in the course of the phenolic coupling and to identify the acetylation of aromatic rings as an important side reaction. We conclude that the proposed analytical approach may be used to identify the molecular carriers of biological activity within the phenolic polymerisates and eventually within natural HS.

The reduction of Cr(VI) by humic substances from leonardite and peat was investigated by capillary zone electrophoresis at various pHs. Both humic materials reduced Cr(VI) at pH 5.4, but not at basic pH. The capacity of leonardite humic substances to reduce Cr(VI) was lower than that of peat humic substances. Fe(III) accelerated the reduction of Cr(VI) by peat humic substances, but not by leonardite humic substances. Cr(VI) reduction mechanisms are proposed. The coal humic substances seem more suitable for remediation of Cr(VI)-contaminated sites.

Three samples of high-molecular-weight humin-like substances were obtained by solid-phase cultivation of Coriolus hirsutus and/or Cerrena maxima on oat straw. The yield of humin-like substances amounted to 1.38–2.26% of the weight of the plant substrate consumed. These substances, produced both by individual and mixed cultures of the basidiomycetes, were shown to be similar in their structure and physicochemical properties. According to the data of IR and 13C-NMR spectroscopy, the substances contained aromatic fragments and were close to soil humic acids. Studies of the dynamics of laccase production suggested that the humin-like substances were produced via direct degradation of lignin macromolecules with direct involvement of extracellular laccase.

Eleven well characterized humic substances (HSs) were adsorbed from aqueous solution onto a Na-kaolin clay. The adsorption affinity (K L ), maximum adsorption capacity (b), a coefficient of desorption hysteresis (H), and the concentration of irreversibly adsorbed HS (IHS) were derived from adsorption-desorption isotherms. These parameters were correlated with structural features of the HS. The adsorption affinity was shown to correlate directly with the aromaticity of the HS and inversely with their polarity, expressed as the O/C atomic ratio. A dependency between polarity and maximum adsorption capacity was not confirmed. The parameters b, H, Rand IHS expose close correlation with the molecular weight (MW) and the partial negative charge of HS (Z) at the operating pH value. The following quantitative relationship was obtained: b = 715 - 0.06 × MW -529 × Z (r = 0.92). It allows a selection of HS with respect to the largest content of organic matter in HS-kaolin clay complexes. Among the HS studied the high molecular weight materials enriched with C-and H-substituted aromatics, such as coal and peat humic acids (HAs), are shown to be the most preferential materials for preparing stable HS-clay complexes.

Nuclear magnetic resonance (NMR) resonance integrals obtained from one-dimensional NMR spectra provide semiquantitative contents of humic constituents with limited resolution in structural detail. When supplemented by connectivity information available from homo- and heteronuclear two-dimensional NMR spectra a more reliable assignment of humic substructures becomes available. This is demonstrated with a comparative one- and two-dimensional NMR analysis of a fulvic and a humic acid obtained from Eriophorum peat. An example of a detailed analysis of the proton chemical shift region normally attributed to carbohydrates shows substantial contributions from amino acids, amino and desoxy sugars, and highly oxidized aliphatic chains of intermediate length. The very good resolution of structural detail by a combined analysis of all NMR spectra shows that the effect of the fractionation procedure on the composition and chemical structure of humic materials is very significant. The comparison of the partial structures comprising humic acid (HA) and fulvic acid (FA) of the peat humic materials studied indicates that FA is diagenetically downstream of HA, favoring the biopolymer degradation (BD) model of humification.

The objectives of this study were to identify molecular features characteristic to arctic DOM from the Kolyma River basin and to elucidate structural imprints induced by a choice of the sorption technique. To achieve this goal, DOM was isolated from the Kolyma River basin with a use of three nonionic sorbents: Amberlite XAD-8 resin, PPL- and C18 - SPE cartridges, and one anion exchanging resin-diethylaminoethyl (DEAE) -cellulose. The structural studies were conducted with a use of electrospray ionization Fourier Transform Ion Cyclotron Resonance (ESI FT-ICR) mass spectrometry and liquid state (1)H NMR spectroscopy. The DOM isolates obtained with a use of PPL and C18 cartridges were characterized with higher content of aliphatic compounds as compared to XAD-8 and DEAE-isolates. In total, for all arctic DOM isolates we observed predominance of hydrogen saturated compounds with high H/C values of identified formulas from FT-ICR MS data. (1)H NMR spectroscopy studies have confirmed this trend and revealed high contribution of alkyl-chain protons into the spectral density of the arctic DOM reaching 43% for PPL isolates.

The objective was to study plutonium partitioning between immobile and mobile humic materials at the water-solid interfaces. Immobilization of the humic materials on solid supports was performed in situ using self-adhesive silanized humic derivatives. The presence of the humic adlayers on solid supports was shown to significantly enhance Pu sorption and its retention under both steady state and dynamic conditions. While plutonium may exist in multiple oxidations states plus colloidal forms, the major thrust in this work was to study the behavior of most mobile--the PuO2(+) form in dilute solutions. The values of the plutonium partition coefficients (Kd) between water and humics-coated silica gels after 10 days exposure reached 1.6 × 10(4) L · kg(-1) at pH 7.5 under anaerobic conditions with a total plutonium concentration of 1.2 × 10(-8) M exceeding those for the uncoated SiO2 (6.3 × 10(2) L · kg(-1)). Column tests showed substantial sequestration of water-borne plutonium (up to 73%) on the humics-coated silica gels. Remobilization experiments conducted under batch conditions at different pH values (3.5, 4.5, 7.5) showed that no more than 3% of the sequestered Pu was remobilized from the humics-coated silica gels by treatment with dissolved humic materials at environmentally relevant pH of 7.5. Consequently, silanized humic materialas can be seen as both molecular probes and as potent candidate materials for scavenging mobile Pu from an aqueous phase.

By transforming the time-based x-axis of electropherograms in capillary zone electrophoresis (CZE) into the corresponding effective mobility-scale, we propose a simple and robust data representation for a better qualitative and quantitative capillary electrophoresis (CE) analysis. The time scale of the raw electrophoretic data (detection signal versus time) is transformed into an effective electrophoretic mobility scale (mu eff-scale) with account of the electroosmotic flow (EOF) peak or of an internal standard of known effective mobility. With the new scaling (detection signals versus effective mobility), the obtained electropherograms are more representative of the velocity-based electrophoretic separation and the comparison of complete electropherograms is directly possible. This is of importance when tracking peaks in real samples where alteration in EOF stability can occur or when comparing electrophoretic runs from different experimental setups (independence in column length and voltage). Beside the qualitative possibilities, a quantitative improvement is achieved in the mu eff-scale with significant better peak area reproducibility and equal to more precision in quantitative analysis than with the primary time-scale integration.

In freshwater ecosystems, dissolved humic substances (HS) can sorb hydrophobic organic chemicals and thereby reduce their bioconcentration and toxicity. The extent of the sorption depends both on the concentration and on the origin of HS. This paper summarizes work that characterized HS from different origins by various spectroscopic and chemical properties, and related these properties to (1) the sorption of polycyclic aromatic hydrocarbons (PAHs) by HS (measured by a fluorescence quenching method), (2) effects of HS on the bioconcentration of PAHs and (3) effects of HS on the toxicity of PAHs. The most powerful predictor of the association between 26 different HS and the PAHs pyrene, fluoranthene, and anthracene was the content of aromatic carbons of the HS. The influence of HS on the bioconcentration of PAHs was investigated by measuring the effect of seven different humic and fulvic acids on the uptake of pyrene and benzo[a]pyrene into the nematode Caenorhabditis elegans. Again, parameters describing aromatic properties of the HS, such as the content of aromatic carbons, or the specific absorptivity at 254 nm gave the best prediction of HS effects on bioconcentration. Studies on the effect of HS on the toxicity of PAHs (impact on grazing activity of Daphnia magna) gave similar results: The detoxifying ability (= reduction of toxicity) of HS could be correlated to the quotient between aromatic carbons and aliphatic carbons in the HS. Taking these results together, we can describe the relationship between structure and effects of HS on bioavailability and toxicity of PAHs as follows: HS associate with PAHs, making the PAHs unavailable for uptake into organisms, and consequently reducing toxic effects of the PAHs. Aromatic properties of the HS can be used to predict the effect of HS in each of these steps.

An approach to the generation of size exclusion chromatographic (SEC) descriptors of humic substances (HS) is proposed. It implies a calculation of initial, central and normalised statistical moments and some of their ratios from the raw SEC-data. The proposed descriptors extend the pool of common molecular weight (MW) characteristics (average MW’s and their ratios) up to 20 parameters, which is important for the purposes of classification and prognostic modelling. Original software was developed to facilitate the computation of molecular weight distribution (MWD) and SEC-descriptors of HS from raw chromatographic data. The developed approach was applied to two model compounds and three humic materials. The discriminatory power of the calculated descriptors was roughly estimated on the example of three humic materials of different origin with the use of a multivariate variance analysis. Weight average MW and a ratio of the z- to weight average distribution coefficients were found to be the best discriminators, whereas the significance level of discrimination provided by the second moment and Mz/Mw-ratio was lower than 95%. ©2000 Elsevier Science B.V. All rights reserved.

Coal humic acids are successfully tested for the first time as new nontoxic agents for the preparation of core-shell iron oxide magnetic nanoparticles.

The use of size exclusion chromatography (SEC) to support a theory of conformational changes in humic acids induced by organic acids is reviewed. Particular attention is given to an evaluation of the role of non-size exclusion effects in SEC experiments. In this review, results from SEC studies are interpreted in terms of electrostatic, salt, and specific sorption effects that influence the behavior of the HS on the gel. That interpretation has been proven by experimental results from SEC-fractionation of HS in the absence of organic acids, and this has revealed similar interactions between the HS and the gel. The preference here is for the theory of non-size exclusion effects based on considerations of HS as natural polyelectrolytes.

Parameters are proposed to describe the distribution of the effective electrophoretic mobilities of various anionic polyelectrolytes such as poly(styrene-4-sulfonates) and humic substances of different origins analyzed by capillary zone electrophoresis. The first step of the data treatment is a baseline correction and conversion of the electrophoretic raw time data to effective electrophoretic mobilities (μ-scale), taking into account the electroosmotic flow. With this new μ-scaling, the electropherograms are more representative of velocity-based separation phenomena than those using migration times, and a direct comparison of electropherograms is possible. Four different average electrophoretic mobilities were defined: the number-average effective mobility (μn), the weight-average effective mobility (μw), the z-average effective mobility (μz), and the peak-average electrophoretic mobility (μp). The polydispersity of the mobility of mixtures was described by the μw/μ⊓, μz/μw, and μp/μw ratios. These parameters were used to describe the electrophoretic mobility distributions of different fractions of restricted molecular size: those obtained by ultrafiltration from a soil humic acid at neutral pH and reference humic substances of the International Humic Substances Society at different values of pH and ionic strength. The data clearly show the influence of both molecular size and charge distribution of the analyzed mixtures on the mobility distributions.

Partition coefficients for the binding affinities of pyrene, fluoranthene, and anthracene to 26 different humic materials were determined by fluorescence quenching. Sources included isolated humic acids, fulvic acids, and combined humic and fulvic fractions from soil, peat, and freshwater as well as Aldrich humic acid. Each of the humic materials was characterized by elemental composition, ultraviolet absorbance at 280 nm, molecular weight, and for 19 samples, composition of main structural fragments determined by 13C solution-state NMR. The magnitude of the Koc values correlated strongly with the independent descriptors of aromaticity of humic materials, including atomic H/C ratio, absorptivity at 280 nm, and three interdependent 13C NMR descriptors (CAr-H,R, ΣCAr, ΣCAr/ΣCAlk). Statistical comparison of humic sources grouped by the origin revealed that binding affinities were best predicted by the 13C NMR descriptors, with a slight prevalence of ΣCAr/ΣCAlk ratio, while molecular weight was the poorest pr...

Size exclusion chromatography (SEC) is a powerful tool for the determination of molecular size of compounds. However, the conducted SEC analysis of 35 humic substances (HS) samples demonstrated, that it has some severe pitfalls for the molecular weight characterization of HS resulting from a lack of appropriate standards. To overcome this problem, a new approach to calculation of molecular weight from the SEC data was developed. It is based on the correction of the experimentally determined distribution coefficient ( K d ) values according to the predictive equations derived either from the data on charge density and hydrophobicity of the analyte or from the values of its characteristic structural parameters. Verification of both predictive equations using model compounds has displayed much better prognostic potential of the polynomial equation developed with a use of integral structural parameters of the analyte. Application of this predictive equation to synthetic polyelectrolytes gave satisfactory estimates for all the polymers with K d >0.15. The model calculation for an averaged sample of HS allowed to estimate a difference between the ideal and experimental values of K d (Δ K d ) by a value of 0.02. The correspondent correction of the SEC-data of 35 HS samples showed overestimation of the values of molecular weight of HS determined by the standard data handling technique. The obtained model estimations are to be verified along with the further development of the model based on the adjustment of the model assumptions to specific polyelectrolytic properties of HS.

A method to enumerate labile hydrogens in all constituents of molecular ensemble of natural organic matter (NOM) based on our previously developed simple hydrogen/deuterium (H/D) exchange (electrospray ionization (ESI) ion source (Kostyukevich et al. Anal. Chem. 2013, 85, 5330) and ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry is presented. The method was applied for analysis of Suwannee River fulvic acid (SRFA), which is an International Humic Substances Society standard, as well as Siberian crude oil; and lignosulfonate. We found that SRFA and lignosulfonate molecules contain 2–5 labile hydrogens, and their number increases with the number of oxygens in the molecule. Also, we observed that compounds of Siberian crude oil ionizing in positive-ESI mode do not have labile hydrogens, while compounds ionizing in negative-ESI mode have one labile hydrogen that detaches during ESI ionization.

In order to understand humic substance (HS) uptake by plants and its entrance into the plant vascular system, a microautoradiography approach using tritium-labeled HS was applied. Wheat seedlings were used as test plants. The data obtained clearly demonstrated preferential radial transport of HS by the apoplastic pathway. Epidermal and cortex cells did not remove significant proportions of humic substances, and the endodermis was shown to be the major control point for their radial transport.

A study of nitrogen release from native and aminoorganosilane derivatives of humic substances (HS) has been conducted. It was demonstrated that dissolution of humics in water resulted in nitrogen release mainly in the form of ammonium ions, whereas under soil conditions, nitrogen detected in soil extract was presented mainly in nitrate form due to nitrification processes. The amount of nitrogen transformed into nitrate form from aminoorganosilane-modified HS varied from 36 to 58% of introduced and was significantly less than that for (NH4)2SO4 (98%), demonstrating that further study of aminoorganosilane-modified HS as slow-nitrogen-release additional fertilizing or supplements to main nitrogen fertilizers is very promising.

Humic substances (HS) are self-assemblies of natural polyelectrolytes occurring throughout the environment. They have been known to play important biospheric roles by mediating uptake of nutrients by plants, regulating biogeochemical cycles of elements, mitigating adverse impact of contaminants, and structuring soils. Until recently, it was believed that these are mostly molecular (complexing) interactions which drive substantial impact of HS on stability of colloids, bioavailability of nutrients, and toxicity of contaminants. The advent of nanotechnology supplied new tools for exploring mechanisms of HS interactions with metals and metal oxides on molecular and nanoscale. The new findings unraveled a great potential of HS in the field of matrix-assisted synthesis of metal-containing nanoparticles (NPs). This chapter gives examples of those syntheses for producing NPs with superparamagnetic properties and of enhanced bioavailability to plants, which demonstrates potential for a transfer in technological applications.

This study proposes a novel fluorescence spectroscopy approach that opens up additional possibilities for using pyrene as a polarity probe. In contrast to the standard approach that is based on measuring the ratio of pyrene vibronic peak intensities, our approach uses the ratio of pyrene integral fluorescence intensity upon excitation into vibronically coupled first and second singlet states: transition probabilities from the ground to those excited electronic states demonstrate opposite trends with environmental polarity variations. In our work, the existence of this effect has been demonstrated for aqueous solutions of pyrene with varying concentrations of humic substances. This provides independent evidence of the non-zero fluorescence quantum yield of pyrene molecules bound by humic substances and indicates their lower environmental polarity. Moreover, the obtained results lay the groundwork for development of a reliable approach to quantitative characterization of pyrene interaction with humic substances.

Four mumijo samples originated from different mountain ranges were studied using size-exclusion chromatography (SEC), Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), and 1H and 13C NMR spectroscopy. All the used analytical techniques demonstrated that the mumijo samples studied consist of a “high-molecular” fulvic-like and a low-molecular components. The second component is shown using FTICR MS and NMR methods to be predominantly a range of vegetative and animal metabolites.

In nature, many functional nanoarchitectures are self-assembled due to supramolecular interactions of natural organic matter and surfaces of mineral particles. However, direct evidence for molecular mechanisms responsible for these interactions is still missing. Here, we developed silanol derivatives of humic substances capable of self-assembling onto hydroxylated surfaces. By using humic substances from peat and coal and DNA array glass slides, we show that humic adlayers were homogeneous on macroscale, but separated into domains of nanosize in coal HS and submicro size in peat HS. The peat adlayers were characterized with larger roughness of 11 nm versus 5 nm for coal. Measurement of the contact angle showed that application of humic coatings leads to an increase in hydrophobicity of glass. It was shown that treatment of soil aggregates with silanol derivatives of humic acids increases water stability of the aggregates.

Humic substances (HS) of different origins have been labeled with tritium by the thermal activation method. Specific radioactivity of labeled HS ( 3 H-HS) was sufficiently high and varied from 0.14 to 0.6 TBq/g. Parent HS and 3 H-HS were analyzed by size exclusion chromatography with radioactivity and UV detection. The results allowed concluding that (1) neither partial decomposition nor polymerization of HS occurred during labeling and (2) tritium labeled molecules have a regular distribution among HS fractions of different molecular weights. The performed correlation analysis revealed that there was no significant relationship between HS properties and specific radioactivity of the obtained 3 H-HS. Thus universality of the developed technique for radioactive labeling of HS with tritium could be demonstrated.

The ultrahigh-resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrum of natural organic matter (NOM) contains several thousand peaks with dozens of molecules matching the same nominal mass. Such a complexity poses a significant challenge for automatic data interpretation, in which the most difficult task is molecular formula assignment, especially in the case of heavy and/or multielement ions. In this study, a new universal algorithm for automatic treatment of FTICR mass spectra of NOM and humic substances based on total mass difference statistics (TMDS) has been developed and implemented. The algorithm enables a blind search for unknown building blocks (instead of a priori known ones) by revealing repetitive patterns present in spectra. In this respect, it differs from all previously developed approaches. This algorithm was implemented in designing FIRAN-software for fully automated analysis of mass data with high peak density. The specific feature of FIRAN is its ability to assign formulas to heavy and/or multielement molecules using "virtual elements" approach. To verify the approach, it was used for processing mass spectra of sodium polystyrene sulfonate (PSS, M(w) = 2200 Da) and polymethacrylate (PMA, M(w) = 3290 Da) which produce heavy multielement and multiply-charged ions. Application of TMDS identified unambiguously monomers present in the polymers consistent with their structure: C(8)H(7)SO(3)Na for PSS and C(4)H(6)O(2) for PMA. It also allowed unambiguous formula assignment to all multiply-charged peaks including the heaviest peak in PMA spectrum at mass 4025.6625 with charge state 6- (mass bias -0.33 ppm). Application of the TMDS-algorithm to processing data on the Suwannee River FA has proven its unique capacities in analysis of spectra with high peak density: it has not only identified the known small building blocks in the structure of FA such as CH(2), H(2), C(2)H(2)O, O but the heavier unit at 154.027 amu. The latter was identified for the first time and assigned a formula C(7)H(6)O(4) consistent with the structure of dihydroxyl-benzoic acids. The presence of these compounds in the structure of FA has so far been numerically suggested but never proven directly. It was concluded that application of the TMDS-algorithm opens new horizons in unfolding molecular complexity of NOM and other natural products.