Multi-site proton interactions with natural organic matter

Water samples from various locations in Norway were used to isolate natural organic matter (NOM). The NOM was isolated using both reverse osmosis and low-pressure low-temperature evaporation for each sample site. These samples were titrated from −log[H⁺] 3 to 11 at 0.1 unit intervals. The data were analyzed using the Discrete Site Analysis (DISI) technique for pK_a intervals of 0.2. The acidity constants are grouped into four classes: strong (pK_a < 5), intermediate strong (5.1 < pK_a < 7.5), intermediate weak (7.6 < pK_a < 9.2), and weak (pK_a > 9.3). All samples, regardless of isolation method, were found to contain strong and weak ligands, along with some intermediate ligands. For the same sample site, the concentration of these ligands were found to be dependent on isolation method and titration direction (acid then base vs. base then acid). In addition, the concentration and classes of ligands present were found to vary between sample sites. Suwannee River fulvic acid was analyzed as a reference sample, and was qualitatively similar to the NOM samples but quantitatively different. Overall, the differences in pKa spectra due to isolation method and/or titration direction are almost as significant as differences between sample location, but there are no consistent trends in effects of isolation method or titration direction on characterization of NOM.     

Characterization of natural organic matter from eight Norwegian surface waters: The effect of ash on molecular size distributions and CHN content

Natural organic matter (NOM) was isolated by reverse osmosis (RO) from eight surface waters in southern Norway. The freeze-dried samples were reconstituted in deionized water and part of the sample was dialysed against HCl. Samples of both the dialysed and non-dialysed materials were then ultrafiltered to give fractions: >50 000 dal., <50 000 but >10 000 dal. and <10 000 dal. nominal molecular weights (NMW). Dialysis against acid reduced the ash content of the samples by 68±14%. Non-dialysed NOM has a preponderance of carbon in the largest fraction (52.7±30%), while after dialysis, the smallest fraction of NOM has the greatest carbon content (52.2±9.7%). In addition to altering the overall apparent size distributions of the NOM fractions, dialysis generally reduces the amount of nitrogen relative to carbon in the NOM samples. The latter observation appears to be the result of losses of small molecular size organic matter that is enriched in nitrogen.     

Characterisation of NOM by adsorption parameters and effective diffusivities

Adsorption equilibria were studied with RO isolates for both activated carbon and activated alumina. Maximum carbon loadings on the order of 65 mg/g DOC were obtained, while the maximum loadings of activated alumina were about 30 mg/g DOC. In the latter case the slope of the isotherms was generally steeper, indicating weaker adsorbabilities of some of the NOM compounds on the metal oxide adsorbent. Since NOM must be regarded as a multi-component system with respect to adsorption, the data were evaluated by the adsorption analysis procedure. The results were used for a theoretical comparison of NOM adsorption based on the same initial concentration of all samples. The method of colloidal titration was applied to the RO isolates in the range pH = 3–8. Poly-DADMAC was used as a cationic polymer, and a streaming current instrument was used for end point detection. The results which are termed anionic colloidal charge (ACC) values increase with increasing pH for pH = 3–6 while they are about constant for pH = 6–8. At the samples' original pH, the specific ACC values found range from 5.2 to 7.6 meq/g DOC. Mass transfer coefficients for NOM adsorption on granular activated carbon were determined for both RO and EVAP isolates, respectively. The data were used to derive effective diffusivities for each sample. The results differ by a factor of about 2 with the Maridalsvann sample having the highest and the Humex sample having the lowest diffusivity. Furthermore, the results for the EVAP isolates are in 8 of 9 cases higher than for the RO samples. Based on a comparison with known macromolecules, average molecular weight values were estimated to be on the order of 700–4800 Dalton.     

Isolation of natural organic matter — The influence on the assimilable organic carbon

The biofilm formation potential (BFP), determined by the assimilable organic carbon (AOC), was measured in water samples containing natural organic matter (NOM), and in “identical” samples reconstructed from NOM isolated by reverse osmosis (RO) and dissolved in distilled water. The results showed identical BFP in natural and reconstructed NOM water samples within the standard deviation of the AOC measurements. These results indicate that the composition of the NOM is the single most important parameter for the BFP of natural waters, and that the RO isolation of NOM produces a powder which, after dissolution in distilled water, is representative for the natural water containing NOM with regard to BFP determined by AOC.     

Capillary zone electrophoretic studies on Norwegian surface water natural organic matter

Capillary zone electrophoresis (CZE) is a useful tool for the analysis of the electrophoretic behavior of anionic polyelectrolytes like humic substances. CZE was used to compare natural organic matter (NOM) with high ash content obtained by reverse osmosis (RO) and low temperature, low pressure evaporation (Ev.) from different Norwegian surface water sources. The quantitative relation between the resulting electrophoretic signals (peak height and area) and the carbon amount of the injected NOM samples was found linear. The NOM gave homogeneous signals in CZE, with a distribution of the detection signals around an average electrophoretic mobility (AEM) corresponding to the charge density distribution of the NOM, governed by the distribution of their molecular sizes and acidities. Like humic substances, NOM only appears as anions in capillary electrophoresis (CE), but the high ash content of these samples and the presence of metals strongly influenced their mobilities at lower pH. CZE could be used as a tool for the rapid evaluation of the average net charge and the molecular radius of the NOM at pH 5.1.     

Basic characterization of Norwegian NOM samples — Similarities and differences

NOM (natural organic matter) samples, isolated by reverse osmosis (RO), and nine NOM samples, concentrated by low-pressure, low-temperature evaporation (EVA) from various origin in Norway, were characterized by different methods. The methods included elemental content of the freeze-dried samples (C, H, N, and O), elemental content of the redissolved samples (DOC, Na, Ca, Cu, Fe, and Mn), specific spectral absorbance at λ = 254 nm (A(254 nm)/DOC) and at λ = 436 nm (A(436 nm)/DOC), UV/Vis-spectra, specific fluorescence (excitation and emission spectra), proton capacity, Cu-complexation capacity, and content of hydrolysable amino acids and carbohydrates. In addition, chromatographic characterization by gel chromatography and reversed-phase chromatography was done. Studies on adsorption and flocculation abilities and the formation of trihalomethanes (THM) and organic halogens adsorbable on activated carbon (AOX) upon chlorination were also investigated. Comparison of the results showed that the samples were different according to the origin of the sample, isolation procedure, and time of sampling. The differences are not the same for all parameters used. Standardized procedures have to be applied to redissolve the organic material in water in order to compare data. For the samples investigated, it was shown that parameters like elemental analysis (H/C ratio), the specific spectral absorption in the UV range, proton capacity, complexation capacity and anionic particle charge, amount of hydrolysable amino acids and carbohydrates, adsorption behaviour on activated carbon, and the THM-FP are sensitive parameters to show differences concerning origin and isolation procedure.     

Natural organic matter in drinking water — The “NOM-typing project”, background and basic characteristics of original water samples and NOM isolates

The complex nature of natural organic matter (NOM), and the impact of this matter on drinking water quality, necessitate international co-operative efforts. After several decades of struggle, many experienced NOM scientists world wide recognize the need for international sample references, or better yet, to work together on the same set of samples. The aim of the “NOM-typing project” was a multi-method characterization of a limited number of NOM samples, isolated from different water sources. The background of the project and the nature of the sampling sites are described here, and some data comparing the composition of the samples, before and after the isolation, are presented. The techniques used for isolation were reverse osmosis (RO) and evaporation (EVA). The NOM samples were isolated from eight different locations in the southern part of Norway. The nature of the corresponding catchments differs, however, all samples were from areas with no influence of agriculture or local industry. The key issue of the project was that all samples were isolated with exactly the same methods and by the same team. In spite of the uniformity of the isolation technique used for the nine samples, the recoveries of the material differ from sample to sample. Generally, the loss of NOM is in the range of 10%, however, for one sample, the loss was as high as 35%. These discrepancies are probably partly because of differences in the nature of the NOM and partly due to differences in the general composition of the ambient water. There are a few remarkable differences between the nine samples. There was a high percentage of ash in isolates from acidified areas. These are also the samples where the loss of NOM during the isolation process was highest. The density of the RO-isolates differs 10-fold between the samples. The lipophilisity of the NOM samples, expressed as relative solubility in octanol, differs more than 30-fold.     

Fluorescence analysis for multi-site aluminum binding to natural organic matter

Natural organic matter (NOM) samples isolated from different water sources in Norway were compared using their fluorescence properties. Fluorescence surfaces were observed at pH 4.36 and deconvoluted using SIMPLISMA (Windig and Guilment 1991). There were a total of seven different fluorophores observed for these samples and each sampling site had between four and six of the fluorescent components. These components were observed to bind Al during titrations at the same pH. Multiresponse titration curves were fit using the method of Smith and Kramer (1998) and most of the binding strengths are similar to values for Suwannee River fulvic acid (logK' between 4.8 and 5.5), but there are strong sites (logK' = 7) and weak sites (logK' between 3 and 4) also observed. Results depended on the isolation method used; reverse osmosis and low pressure evaporation yielded different values but with no consistent trends.     

Biota-sediment accumulation factors for Dechlorane Plus in bottom fish from an electronic waste recycling site,South China

Biota-sediment accumulation factors (BSAFs) for Dechlorane Plus (DP), a highly chlorinated flame retardant, were determined in three bottom fish species, i.e., crucian carp, mud carp, and northern snakehead from an electronic waste recycling site in South China. The average BSAFs are 0.007, 0.01, and 0.06 for syn-DP, and 0.003, 0.025, and 0.001 for anti-DP in crucian carp, mud carp, and northern snakehead, respectively, suggesting low bioaccumulation potential of DP isomers in these fish. However, the bioaccumulation factors (BAFs) determined previously in the same sample set indicated that both DP isomers were highly bioaccumulative (BAFs > 5000) in most of the samples. This implies that BSAF values may be inherently inconsistent affecting their reliability as a bioaccumulation indicator. The BSAFs for DP isomers are two orders of magnitude lower than those (average of 0.43–2.28) for extremely hydrophobic polychlorinated biphenyls (CBs 199, 203, 207 and 208), but are comparable to those (average of 0.0001–0.009) for decabromodiphenyl ether (BDE 209) determined in the same sample set. Despite of the different chemical structures of the three compound classes, significantly negative correlations between logarithm of octanol–water partition coefficients (log K_OWs) and BSAFs of these chemicals were found, indicating that hydrophobicity is one of the key factors influencing the bioaccumulation of these compounds.     

The removal of metals and ammonium by natural glauconite

Glauconite deposits, naturally occurring aluminosilicates rich in iron and potassium, are abundant in New Jersey, Delaware, and Maryland. The presence of these deposits has been shown to be responsible for a high content of sodium in ground water for certain region of Maryland. The ammonium and metal (Pb, Zn, and Cd) removal capability was investigated in both batch and column reactors using natural, NaCl- and NaOH-treated glauconite-bearing sand. Ammonium removal by glauconite is a typical ion exchange process. Both ion exchange and adsorption are responsible for matal removal. Important factors such as pH, sample source, and method of pretreatment were studied. The metal removal follows the order of Pb(II) > Zn(II) > Cd(II). The surface acidity of the glauconite is characterized by an acidmetric-alkalimetric titration. The acidity constants, pK₁ⁱ, and pK₂ⁱ, and 3.6 and 6.0, respectively.     

Basic characterization of reference NOM from Central Europe — Similarities and differences

The FA and HA fractions represent 20 to 50% of the DOC of the original samples, depending on the origin, and serve as reference materials. The original aqueous samples and the aqueous solutions of the reference materials were characterized with methods suited for measuring samples at natural concentrations. The DOC normalized values of the spectral absorbances (λ = 254 nm; λ = 436 nm) in the original water samples were highest for the brown water and brown coal water and lowest for the secondary effluents. The FA fractions were similar in the UV-absorbance with the exception of the low-absorbing groundwater FA, reflecting a low density of double bonds. The DOC-normalized proton capacity of the FA fractions (10 to 20 μmol/mg) was highest for the brown coal, brown water, and soil-derived samples and again lowest for the groundwater FA. The high values are due to a higher contribution of the weak acids of phenolic type. Specific data for copper complexation capacity (0.5 to 2.5 μmol/mg) went parallel to the proton capacity. The characterization of the FAs by gel chromatography with organic carbon detection revealed three major fractions. The refractory part at short retention time dominated in the brown water and soil-derived samples, whereas the fractions for the lower molecular mass acids at long retention times were dominant in the secondary effluent and the brown coal isolate. Comparison with UV-detected chromatograms revealed a strong decrease in the specific absorbance of the secondary effluent. Up to 3% of the total mass of the FAs could be identified as hydrolyzable amino acids with the highest yield in the sample from secondary effluent and the lowest one in the groundwater sample. The nitrogen content was always higher in the FAs compared to the HAs of the same origin. The application of gel chromatography fluorescence and fluorescence decay time distribution analysis turned out to be a useful tool to differentiate between the different fractions of NOM, the isolates obtained by different methods (e.g., XAD-8, membrane separation) and the fractions of the samples from different origin and age. This is of special value, for the information can also be obtained for samples with natural NOM concentrations, even though further investigations required for full understanding of the data. This work is part of a multi-disciplinary research program (ROSIG: Refraktäre Organische Säuren in Gewässern), funded by the German Research Association (DFG).     

Direct N2O emission from agricultural soils in Poland between 1960 and 2009

Nitrogen fertilization (N) is commonly known as a main source of direct nitrous oxide (N₂O) emission from agricultural soils. An area of 38 % of the total land surface of Poland was covered by agricultural soils in 2009. In this paper, we aimed at analyzing data regarding the land exploitation for 13 selected subareas of Poland between 1960 and 2009. Seven out of the 13 subareas studied are located in the West (area A), and six subareas are located in southeast of Poland (area B). The total area covered by large farms (>20 ha) differed largely, between area A (10.6 %) and area B (0.9 %) in 2009. Both areas varied in terms of the amount of fertilizers used annually, average crop yield and crop structure. Average direct emissions of N₂O from agricultural soils were 1.66 ± 0.09 kg N₂O–N ha^?1 a^?1 for area A, 1.39 ± 0.07 kg N₂O–N ha^?1 a^?1 for area B and 1.46 ± 0.07 kg N₂O–N ha^?1 a^?1 for the whole country between 1960 and 2009.     

Characterization of natural organic matter by pyrolysis/GC-MS

Natural organic matter (NOM) in nine water samples selected for the NOM typing project were characterized by pyrolysis in conjunction with gas chromatography and mass spectrometry (GC-MS). NOM samples both isolated by reverse osmosis and evaporation techniques were subjected to high temperature pyrolysis and the products obtained were assigned to one of the four main types: biopolymers carbohydrates, proteinaceous materials, N-acetylamino sugars, and polyhydroxy aromatics. These biopolymers in the water samples were quantified and the quantities were used in characterization. Principal component analysis was employed in revealing the similarities and differences between the samples and between the separation techniques. The results indicate that there are little differences between the samples, and the NOM separated by evaporation preserves most of the organic material compared to the reverse osmosis technique.     

Characterization of Norwegian natural organic matter: Size,diffusion coefficients,and electrophoretic mobilities

Eighteen Norwegian NOM samples were analyzed by AFM, TEM, FCS, and CE. The TEM and AFM gave complementary, but not identical, information regarding the conformation of the NOM. A large majority of the material in all samples appeared as points with a size of approximately 2 nm or less. FCS gave values for diffusion coefficients which were in the range 2.1–3.0 × 10⁻¹⁰ m² s⁻¹. This corresponds to molecular diameters of between 1.6 and 2.0 nm, in reasonable agreement with both TEM and AFM. Electropherograms, using absorbance at 200 nm, were all dissimilar except for the Gjerstad and Hellerudmyra sample pairs, for which no major differences were observed. CE was also carried out using both fluorescence (excitation at 325, 457, and 488 nm) and UV-absorbance (200, 210, 254, and 288 nm) detection on three of the NOM samples. The different modes of detection and wavelengths gave qualitatively similar electropherograms. Calculated EPMs of the major sample components were in the range -2.0 to -5.0 10⁻⁸ m² s⁻¹ V⁻¹.     

Biological vs. chemical properties of natural organic matter isolated from selected Norwegian lakes

Relationships among different spectroscopic, chemical, and biological properties of dissolved natural organic matter (NOM) were investigated. NOM samples were isolated by means of reverse osmosis from eight Norwegian lakes. Elemental composition, absorption spectra (UV, VIS, IR), the influence on algal growth, and accumulation rates of metals by mussels in the presence of NOM were measured. Linear regression and principal components analyses were utilised to assess relationships between the biological and chemical properties. It was concluded that the content of organic matter in the isolates and the aromaticity of NOM, as characterised by UV and VIS spectra, are best correlated with the biological properties.     

Bioaccumulation of PCDD/Fs,PCBs and PBDEs by earthworms in field soils of an E-waste dismantling area in China

A total of 60 paired samples of earthworm, corresponding soil and wormcast were collected to investigate the bioaccumulation tendency of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in earthworms from a typical E-waste dismantling area in east China. Significant correlations were observed for the total concentrations among different matrix types except for PCDD/Fs in soil and earthworm. The bioaccumulation tendency showed some differences among the contaminants. Calculated biota–soil accumulation factors (BSAFs) indicated that PCBs and PBDEs had higher bioaccumulation potential compared to PCDD/Fs, which was somewhat different from laboratory studies. The plot of mean BSAFs versus log K_ow values for PCBs and PBDEs was well fitted by a second-order polynomial with the maximum BSAF at approximately log K_ow of 6.5. While for PCDD/Fs, only a slightly decreasing trend was observed with increasing log K_ow. Composition analysis indicated that tetra-, penta- and hexa-halogenated homologs had higher bioaccumulation levels, indicating that medium-halogenated congeners with log K_ow around 6.5 are more easily accumulated by earthworms. Furthermore, the ratios of BDE-47/-99 and BDE-99/-100 showed some discrepancies with the technical products and other biotic species, suggesting different bioaccumulation potential of PBDEs in earthworm.     

Transport of NOM and trace metals through macropores in the Lake Skjervatjern catchment

In the dystrophic Lake Skjervatjern, located at the west coast of Norway, periods with high precipitation coincide with an increase in the concentrations of natural organic matter (NOM) and several trace elements. The lake has no visual inlets, and, during high flow periods, a major part of the drainage follows macropores, entering the lake 10–40 cm below the surface. Water from the lake and the macropores were fractionated according to size by means of a hollow fiber ultra-filtration technique, during two periods with high precipitation. In the macropores, the high molecular weight form of NOM (nominal molecular cut off > 10 kDa) appears to be an important transporting agent for several trace elements that strongly interact with NOM (e.g., Fe, Al, Pb, Sm, La, Ce, and Eu). In contrast, anionic (V and As) and acid sensitive (Mn and Cs) elements were, generally, at a low molecular weight form (nominal molecular cut off < 3 kDa). The latter showed similar or lower concentrations in the macropores compared to the lake water, and NOM were apparently of small importance as a carrier for V, As, Mn, and Cs. Differences in concentration and size distribution of trace elements between the macropores and the lake basins indicate that parts of NOM and associated trace elements that enter the lake in a high molecular weight form, undergo aggregation and gravitational settling and thereby become a part of the lake sediments.     

Recovery of copper from small grain size fractions of municipal solid waste incineration bottom ash by means of density separation

Small grain size fractions of municipal solid waste incineration (MSWI) bottom ash (BA) contain elemental and chemically bonded metals in appreciable amounts, especially copper. Investigations with a centrifugal concentrator were carried out using samples, which had been treated with different impact devices. Partly the impacts of single devices were visible in outlines, but mostly the surfaces of the metals were still covered with mineral residues. To generate copper rich fractions, parameters of the separation process should ensure mass yields <2%, best between 0.5 and 1%. The density of the concentrates is then generally >3.2 g/cm³. Best results were achieved with material from a special treatment train which is adapted to grain sizes <2 mm. Reliable copper contents between 20 and 40% (single runs >50%) could be realised. However, considering the required mass yields, referred to this subset only 150–170 g copper would be recovered from 1 Mg MSWI BA. Furthermore, this copper is only in parts present in elemental form. A dependable added value of such treatment step seems to be given only, if that enables a recycling of the mineral aggregates (tailings) in parallel to avoid landfill costs.