[en] Five column experiments have been carried out to investigate the effect of flow rate on the breakthrough curves (BTCs) of phosphate, fulvic acid, and uranium(VI) onto a silica column. Both BTCs of phosphate and fulvic acid, and three BTCs of uranium(VI) in the presence and absence of phosphate or fulvic acid at high flow rate published in the previous paper were compared with corresponding initial parts of BTCs at low flow rate in this paper. Each BTC in this paper was expressed as both C/C_o-t and C/C_o-V/V_o plots, where C and C_o are the concentrations in the influent and the effluent respectively, t and V are the time and the effluent volume from the start of injection of pulse solution respectively, V_o is the pore volume of the SiO₂ column. Based on the experimental results and the relationship among V, t, and flow rate F, it was found that there are advantages to using C/C_o-V/V_o plot as BTC to study the effect of flow rate. Based on these comparisons of C/C_o-V/V_o plots at different flow rates and the theoretical analysis from the Bohart-Adams sorption model, it was found that the right shift (increase in V/V_o of breakthrough), the left shift (decrease in V/V_o of breakthrough), and the non-shift (non-change in V/V_o of breakthrough) of initial parts of BTCs with increasing flow rate are certain to occur instead of only left shift and that three different trends of shifts can be mainly attributed to different rate-controlling mechanisms of sorption process. (author)

No abstract available

[en] This work contributed to the adsorption of radiocobalt on goethite as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of fulvic acid (FA) under ambient conditions. The results indicated that adsorption of Co(II) was dependent on ionic strength and foreign ions at low pH values (pH < 7.8), and independent of ionic strength and foreign ions at high pH values (pH > 7.8). Outer-sphere surface complexation and/or ion exchange were the main mechanisms of Co(II) adsorption on goethite at low pH values, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH values. The presence of FA enhanced Co(II) adsorption at low pH values, but reduced Co(II) adsorption at high pH values. The thermodynamic data (ΔH⁰, ΔS⁰, ΔG⁰) were calculated from the temperature dependent adsorption isotherms, and the results suggested that adsorption process of Co(II) on goethite was spontaneous and endothermic. The results are crucial to understand the physicochemical behavior of Co(II) in the nature environment. (author)

[en] Four different sources of humic substances were studied to determine the effects of ozonation on molecular weight distributions, based on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Solutions of two soil-derived fulvic acids and a one soil-derived humic acid, as well as dissolved organic matter (DOM) associated with a natural water source were studied. Both gel permeation chromatography (GPC) and ultrafiltration (UF) were employed to define apparent molecular weight (AMW). Applied ozone doses ranged from 2.0 to 2.5 mg O₃/mg DOC. Overall samples of untreated and ozonated waters, as well as individual molecular weight fractions, were characterized according to DOC, uv absorbance, and THMFP. Ozonation resulted in a significant disappearance of higher AMW material with a corresponding increase in lower AMW material. Although little overall reduction in DOC concentration was observed, significant overall reductions in UV absorbance and THMFP levels were observed

[en] A laboratory study was conducted on the ozonation of an aquatic fulvic acid extracted from a forest pond near Poitiers in France. The rate of molecular ozone consumption was fast during the first minutes, and ozonation led to a slight increase of the lower apparent molecular weight, an enhancement of carboxyl content, and aldehyde formation. By ozonation of a bromide-containing solution of fulvic acid, some brominated organics were formed, while ozonation without bromide led to a reduction of the organic halide formation potential of a fulvic acid, especially in the presence of bicarbonate ions. The increase of GAC-filtration efficiency following ozonation was found to be the result of a biodegradability enhancement of fulvic acid by ozone. Manganese oxidation by ozone was partially inhibited by fulvic acid, particularly in the absence of bicarbonate ions

[en] Sorption of Th(IV) on Zr₂O(PO₄)₂ as a function of contact time, reaction temperature, pH, ionic strength and solid-to-liquid ratio (m/V) is studied under ambient condition by using batch technique. Effects of fulvic acid (FA), phosphate, sulfate and citrate on Th(IV) sorption are investigated in detail. A pseudo-second-order rate equation is used to simulate the kinetic sorption. The removal of Th(IV) increases with increasing pH and hardly depends on ionic strength. Sorption of Th(IV) increases with increasing m/V and reaction temperature. The presence of FA and phosphate enhances the sorption of Th(IV) on Zr₂O(PO₄)₂ while sulfate and citrate decrease the sorption. The Langmuir and Freundlich models are used to simulate the sorption isotherm of Th(IV) on Zr₂O(PO₄)₂ at different temperatures. The thermodynamic data (i.e., ΔH⁰, ΔS⁰, ΔG⁰) are calculated from temperature dependent sorption isotherms. The results suggest that the sorption process of Th(IV) on Zr₂O(PO₄)₂ is spontaneous and endothermic. (author)

[en] The molecular size distribution and fluorescence properties of soil Fulvic Acids (FA) were characterized by using Gel Filtration Chromatography (GFC) and luminescence spectroscopy. The objectives of this work were to fractionate the FA extracted from a forest soil into different nominal molecular size using GFC system and to characterize the fluorescence properties (excitation, emission and synchronous) of these fractions using luminescence spectrometer. The GFC column was calibrated with polyethylene glycols, acetone and dextrane Blue. The total permeation volume of the GFC system was 404 mL and the void volume 130 mL. The GFC molecular weight of the soil FA was in the range of 190∼8,900 Dalton and the molecular weight at the peak on the chromatogram was 930 Dalton. The fluorescence intensity ratio (I_498nm/I_392nm) was found to be increased with an increasing molecular weight. This results may suggest that the fulvic acid fractions with high molecular weight have large amount of the condensed aromatic compound

[en] The abundance of humic-like substances in the atmosphere has received considerable attention since these substances play an important role in various atmospheric processes. The wide variety of quantitative techniques used to study humic-like substances produce dissimilar results, making data comparison difficult. Also, global background concentrations and the transfer of atmospheric humic-like substances are poorly known. Here, we compared resins to extract humic-like substances in aerosols, and we measured contents in aerosols from Mt. Fuji. Results show that diethylaminoethyl cellulose resins extracted more humic-like substances than the diethylaminoethyl resin (hydroxylated methacrylic polymer). The mean humic-like substances concentrations in the free troposphere in East Asia is similar to that in Europe, suggesting that the global background level of humic-like substances is 0.05 μg C m⁻³, based on the humic-like substances concentrations on Mt. Fuji and Mt. Sonnblick. Humic-like substances concentrations, especially fulvic acids concentration, at the summit of Mt. Fuji increased when air masses came from the continent along with the carbon monoxide and ozone.

[en] The Medoc Landes of France are characterized by a covering of quartz sand and the presence of groundwater very close to the surface. The soils that develop there are fairly hydromorphic podzols. The best-drained podzols have a cemented spodic horizon. The organic matter present takes the form of coatings, and consists mainly of fulvic acids that are only slightly biodegradable. The most hydromorphic podzols have a loose B₂h horizon formed from mineral particles and rather humified organic matter. The latter is labile and has a relatively short mean residence time. (author)

[en] This study investigated the optical properties of dissolved organic matter (DOM) using the fluorescence excitation–emission matrix (EEM) method combined with parallel factor (PARAFAC) analysis. The examined DOM samples included Suwannee River fulvic acid (SRFA) and Nordic Reservoir natural organic matter (NRNOM). The optical properties of the DOM were determined from the behavior of individual groups of DOM fluorophores responding to different ionization states. The PARAFAC examination revealed that there were six independent EEM components in the SRFA that behaved differently in terms of pH influence on their fluorescence intensity. The dominant EEM peak locations (λ_ex/λ_em) of these components were (230, 330) nm/420 nm (Component 1), (250, 350) nm/450 nm (Component 2), (240, 340) nm/460 nm (Component 3), (220, 280) nm/380 nm (Component 4), (270, 400) nm/490 nm (Component 5), and (280, 340) nm/540 nm (Component 6). However, only four EEM components were observed in the NRNOM, which are similar to Components 1, 2, 3 and 4 in the SRFA. It can be speculated that Components 1, 2, 3 and 6 can be categorized as traditional terrestrial humic-like chromophores, while they are composed of different fractions of carboxylic-like and phenolic-like chromophores; Component 4 can be categorized as protein-like fluorophores primarily composed of carboxylic-like chromophores, and Component 5 can be categorized as a microbial humic-like component that is overwhelmingly composed of phenolic-like fluorophores. The results demonstrated that PARAFAC analysis is a promising approach for characterizing the fine functions in DOM. -- Highlights: • Optical property of DOM responding to ionized states is deconvoluted by PARAFAC. • Six components in DOM are discerned via individual component behavior with pH. • EEM-PARAFAC is a promising approach to characterize the fine functions in DOM