Artefacts in XAD-8 NOM fractionation

The XAD-8 resin has been widely used during the last decades to characterize and isolate natural organic matter (NOM) in water. The present work focuses on the performance and limitations of the XAD-8 method. A number of different NOM samples (mostly RO-isolates) have been XAD-8 fractionated with the purpose to study (1) the impact of DOC concentration of the samples on the quality of the resulting fractions and (2) the stability of NOM in the different fractions during the XAD-8 fractionation procedure and storage. Focus is placed on the method's independence of NOM concentration, the stability (quantity and quality) of the hydrophilic fraction during the fractionation, the relationship between hydrophilic and hydrophobic fractions, and the stability of the obtained fractions after the fractionation is completed.

The main conclusions are that the division into hydrophobic and hydrophilic fractions are not independent of the NOM concentration and not constant during the procedure, furthermore that the XAD-8 fractions may undergo irreversible alteration of structure due to the procedure or storage that will influence on the interpretation of the data. The possible consequences for the interpretation of results and further analysis or use of the XAD-8 based fractions are discussed.     

Dynamic fractionation of trace metals in soil and sediment samples using rotating coiled column extraction and sequential injection microcolumn extraction: A comparative study

Dynamic fractionation has been recognized as an appealing alternative to conventional equilibrium-based sequential extraction procedures (SEPs) for partitioning of trace elements (TE) in environmental solid samples. This paper reports the first attempt for harmonization of flow-through dynamic fractionation using two novel methods, the so-called sequential injection microcolumn (SIMC) extraction and rotating coiled column (RCC) extraction. In SIMC extraction, a column packed with the solid sample is clustered in a sequential injection system, while in RCC, the particulate matter is retained under the action of centrifugal forces. In both methods, the leachants are continuously pumped through the solid substrates by the use of either peristaltic or syringe pumps.A five-step SEP was selected for partitioning of Cu, Pb and Zn in water soluble/exchangeable, acid-soluble, easily reducible, easily oxidizable and moderately reducible fractions from 0.2 to 0.5 g samples at an extractant flow rate of 1.0 mL min⁻¹ prior to leachate analysis by inductively coupled plasma-atomic emission spectrometry.Similarities and discrepancies between both dynamic approaches were ascertained by fractionation of TE in certified reference materials, namely, SRM 2711 Montana Soil and GBW 07311 sediment, and two real soil samples as well. Notwithstanding the different extraction conditions set by both methods, similar trends of metal distribution were in generally found. The most critical parameters for reliable assessment of mobilisable pools of TE in worse-case scenarios are the size-distribution of sample particles, the density of particles, the content of organic matter and the concentration of major elements. For reference materials and a soil rich in organic matter, the extraction in RCC results in slightly higher recoveries of environmentally relevant fractions of TE, whereas SIMC leaching is more effective for calcareous soils.     

Direct (1)H NMR spectroscopy of dissolved organic matter in natural waters

Nuclear magnetic resonance (NMR) spectroscopy arguably provides the greatest insight into the overall chemical composition of dissolved organic matter (DOM). However, in a standard 5 mm NMR probe, a sample of sea water at natural abundance only contains ca. 500-600 ng of organic matter, distributed among the heterogeneous components of DOM. Additionally, the intensity of the water signal, which may be many orders of magnitude greater than the signals from DOM, makes the detection and analysis of DOM at natural abundance extremely demanding. Here, we demonstrate, that although challenging, the application of an improved water suppression technique allows NMR spectra of DOM to be obtained directly (i.e without pre-concentration) for major bodies of water, including rivers, lakes and the ocean. The technique described here provides a compositional overview of an intact sample, permitting researchers to investigate and assess the impact of concentration, isolation and extraction procedures that are employed routinely. Also the technique permits NMR to be performed on 'precious' samples for which traditional isolations are not possible, for example, water from ice cores and pore water, which are key in hydrology and for paleoclimatic reconstruction.     

Flow injection flame atomic absorption determination of Cu, Mn and Zn partitioning in seawater by on-line room temperature sonolysis and minicolumn chelating resin methodology

A flow-injection system is developed for Cu, Mn and Zn partitioning in seawater by flame atomic absorption spectrometry. The first approach is where the trace metal species are fractionated in situ, but analysis is performed by using a flow injection manifold in the laboratory. This operational mode is used for the determination of the dissolved labile metallic fraction and is based on the elution of this fraction from a minicolumn packed with a chelating resin containing iminodiacetic acid groups (Serdolit Chelite Che) loaded in situ with the sample. The second is used for the determination of total dissolved concentrations of trace metals. This last mode is based on the retention/preconcentration of total dissolved metals on the chelating resin after on-line sonolysis of seawater samples acidified with diluted nitric acid to breakdown the metal-organic matter complexes. The figures of merit for Cu, Mn and Zn determinations in both fractions are given and the obtained values are discussed. The fractionation scheme is applied to the analysis of coastal seawater samples collected in Galicia (Northwest, Spain). The results of fractionation showed that Mn and Zn are mainly in the labile fraction, while Cu was mainly present in the organic fraction.     

Troubleshooting in the trace analysis of organochlorine pesticides in water samples

Summary As a consequence of the high toxicity of organochlorine pesticides their presence in water for human consumption is limited by legislation. To determine these compounds at trace levels, an extraction procedure and a highly sensitive analytical technique is necessary. In this work we have used laminar disks for the solid-phase extraction of 21 organochlorine pesticides from water. The analytical technique selected is gas chromatography with electron-capture detection. A solid-phase extraction procedure is proposed, and some problems has been encountered. Low recovery of some pesticides has been obtained, because of their adsorption by the walls of containers. To prevent this adsorption, addition of 20% methanol before the sampling step is proposed. Adsorption of pesticides by the organic matter present in water samples was also observed. Pesticides can be adsorbed by the membrane filters usually used to remove suspended particulate matter from water samples. Different kinds of filters have been tested, and the occurrence of the problem has been confirmed. The use of laminar disks in this work has overcome this problem.     

Determination of nitrated-polyaromatic hydrocarbons (nitro-PAHs) in environmental samples by high resolution chromatographic techniques

An analytical procedure is described for the fractionation of organic compounds present in environmental samples and the determination of nitro polyaromatic hydrocarbons (nitro-PAHs). Both low and high resolution liquid chromatography are employed for the prefractionation of the soluble organic fraction (SOF) extracted from particulate matter or gaseous pollutants collected on adsorption traps. High resolution gas chromatography is used to analyze four fractions containing alkanes, PAHs, nitro-PAHs, and other polar PAHs. Nitrogen-containing species are separated by GC and detected specifically using an alkali flame (NPD) detector. Flame ionization (FID) detection, GC-MS of positive ions, and negative ion chemical ionization MS of the whole fraction is used for the identification and quantitation of the various components. The composition of SOF extracted from particulate matter emitted from diesel exhausts is elucidated and a large number of nitro-PAHs identified by the combination of the various techniques.     

Fluorescence spectroscopy applied to the optimisation of a desalting step by electrodialysis for the characterisation of marine organic matter

The isolation and characterisation of marine dissolved organic matter (DOM) are still not readily achieved today. The study of this chemically complex material is particularly difficult, especially as it is hindered by the high salinity of seawater. It is therefore essential to develop a method in which a sufficient quantity of marine organic matter can be collected for structural analyses. Reverse osmosis (RO) is often used for the concentration of DOM from freshwaters, due to the fact that DOM is not modified during RO and that DOC recoveries are high (about 80%). Unfortunately, RO cannot be used directly to isolate marine DOM, since both salts and organic matter are concentrated during the process. Therefore, marine samples have to be desalted before their concentration by RO.     

Analytical isolation, separation and identification of mutagens from nonvolatile organics of drinking water

A general procedure has been developed for the concentration/fractionation of mutagenic residue organics from small, less than 50L, and large, to 1200L, volumes of drinking water obtained from a variety of sources. This procedure features concentration of the residue organics chromatographically by passage of the water through XAD-2 and XAD-7 resins in specially designed columns, details of which are given. The residue organics are eluted from the resins via organic solvents, followed by solvent removal and subsequent bioassay for mutagenicity. Then the residue organics are fractionated via a coupled bioassay/analytical fractionation method which progressively focuses to the bioactive constituents of the complex mixture of residue organics. In this report, results for the optimal operation and validation of the concentration system are given, using drinking water derived from an industrially polluted river system, a wilderness river system and a major aquifer system. The predominant type of mutagenesis observed for the residue organics isolated from these samples was direct-acting to the Salmonella tester strain, TA98, which was decreased by the addition of the metabolic activation system from the livers of rats previously treated with Arochlor 1254. Some TA100 direct-acting mutagenesis was observed for all samples. Fractionation of the residue organics indicated the mutagens to be nonpolar. Samples of residue organics collected over a period of a year from each type of drinking water showed no discernable pattern of mutagenesis versus season. The methodologies described in this paper provide a comprehensive approach for the concentration/isolation of residue organics from drinking water for studies to identify biohazardous compounds and to characterize these compounds biologically.     

Distribution and Composition of Organic Matter in Oil- and Bitumen-cotaining Rocks in Deposits of Different Ages

The core samples of oil- and bitumen-containing rocks from Tatarstan's deposits of different ages were studied by thermal analysis methods (DTA, TG, DTG). Based on the obtained data, a procedure was elaborated for determining the enclosed organic matter content and the index of its fraction composition. A significant increase of the organic matter content in the core and its enrichment in high-molecular aromatic structures were shown to occur for the oil-containing rock samples when passing from the Devonian to Carboniferous and Permian deposits. The core samples of the Devonian oil-containing rocks may be divided into three groups: the samples taken from the zones where waste water flooding has been started relatively recently (1), or fresh water flooding has been carried on for a long time (2) and the samples of rock containing clay minerals as impurities. Thus, thermal analysis can be used in geochemical studies to identify the organic matter enclosed by oil- and bitumen-containing rocks. This revised version was published online in August 2006 with corrections to the Cover Date.     

吹扫捕集-气相色谱/质谱法分析汉江有机污染物

采用恒温水浴吹扫捕集-气相色谱/质谱(P&T-GC/MS)法分析汉江水中挥发性有机物,提高了挥发性有机物分析的灵敏度;选用低空白的纯净水,降低了分析的干扰。采用避光的方法以及将水样直接过柱,提高了半挥发性有机物的回收率。用改进了的方法分析汉江水共检出有机物36种。此方法同样适用于其它地表水中有机物的分析。     

Use of diffusive gradients in thin films and tangential flow ultrafiltration for fractionation of Al(III) and Cu(II) in organic-rich river waters

Diffusive gradients in thin films (DGT) and tangential-flow ultrafiltration (TF-UF) were combined for fractionation of Al and Cu in river water containing high content of dissolved organic carbon. A procedure based on ultrafiltration data is proposed to determine diffusion coefficients of the analytes in water samples and model solutions containing both free metal (M) and complex (metal - humic substance). Aiming to evaluate the accuracy of the proposed approach, the DGT results were compared with those from a protocol for determination of labile Al and Cu based on solid phase extraction (SPE). Good agreement between data from DGT and SPE were attained for model solutions. For analysis of real organic-rich water samples, differences between DGT and SPE measurements were consistent with the time-scales of the techniques. The concentration of labile Al determined by DGT were lower than the total dissolved concentrations (determined by inductively coupled plasma mass spectrometry) and exceeded the ultrafiltered concentration, indicating that inorganic Al species (species small enough to pass through 1 kDa membrane) were minor species as compared with Al organic complexes. For both Al and Cu, there were species not measured by DGT as they are not sufficiently labile.     

外加盐对壳聚糖树脂吸附游离酸的影响

利用电化实验技术,跟踪观察交联壳聚糖树脂在不同环境体系吸附低浓度游离酸的行为。讨论了在三元体系（酸 水 盐）和四元体系（酸 水 有机物 盐）中,交联壳聚糖树脂吸附游离酸的规律。利用固-液相互作用方程,求取吸附剂-吸附质相互作用能。实验结果表明,交联壳聚糖树脂在三元体系和四元体系中吸附游离酸,表观吸附速率常数（k)随着外加盐浓度的增大而减小。发现表观吸附速率常数（k)与吸附剂-吸附质相互作用能（U）存在线性关系。     

Assessment of the distribution of pesticides on soil particle fractions in simulated irrigation run-off using centrifugal SPLITT fractionation and ELISA

This study was designed to measure the distribution of pesticides within the mobile phase of simulated irrigation run-off water, using centrifugal split-flow thin-channel (SPLITT) fractionation, a novel technique providing a gentle separation of natural sediment and suspended particles. Particular attention is paid to the extraction of pesticide residues for enzyme-linked immunosorbent assay (ELISA) analysis; ELISA was used because of the limited sample size.Centrifugal SPLITT fractionation combined laminar flow hydrodynamics and centrifugal sedimentation to obtain a continuous binary separation of suspended particles. The non-destructive technique allowed an accurate separation of particles into fractions with divisions at 0.5, 2 and 10 μm, with those above 25 μm being performed by wet sieving. ELISA was used to analyse the concentration of endosulfan and diuron for each fraction generated by the SPLITT technique.This data can be used to determine the role that particulate fines and colloidal fractions play in the transport of bound organic pollutants within the environment and to examine prospects for remediation on farms.     

Radioecological Research on the Marine Environment Facing the Italian Base in Antarctica (1989–91)

Abstract

The results of the analysis of both natural (Th-232, U-238 and K-40) and artificial (Cs-137) radioactivity contained in samples collected during the 1989–90 and 1990–91 PNRA Scientific Campaigns in the Terra Nova Bay (Ross Sea) marine ecosystem, are presented in this paper. The data refers to samples of sea water, pack water, sediments and organisms belonging to demersal ichthyofauna (Pagothenia bernacchii, Chionodraco hamatus) and soft bottom macrofauna (Adamussium colbecki) collected in different coastal and off shore stations of the area investigated. Some sea water samples collected on the way to subAntarctic areas were also considered. The radiocontamination detected in sediments was correlated to the quantities of organic matter, organic carbon and nitrogen contained in the samples. Additionally, Cs-137 concentration factors were calculated for the different biological specimens and their anatomical components. Data values, with special consideration for anthropogenic Cs-137, are compared to results obtained from similar matrixes collected in the Northern Hemisphere in temperate waters before and after the accident at the Chernobyl nuclear plant.     

Distribution of mercury in soil organic matter fractions obtained by dissolution/precipitation method

Sequential multistep procedure, usually used for the fractionation and characterization of soil organic matter was tested for Hg content in the individual steps and fractions. Under general laboratory conditions serious problems have arosen during the attempt in the Hg mass balance calculation. Several sources of Hg contamination were recognized. The most serious was the background concentration of Hg even in research grade chemicals (what is in general not declared) and laboratory air. The work on operational Hg speciation as non-humic bound, humic acid, fulvic acid bound proceeds from the established status-quo on distribution of mercury of soil organic matter.     

Precision of Isolation of Aquatic Humic Matter by Xad-Resin Technology from NMR Spectroscopy's Point of View

Abstract

The most crucial question in the aquatic humus chemistry is a reliable and selective separation and fractionation of the humic solutes from other organic and inorganic constituents. The dilute solutions of natural dissolved organic matter must in a way or another be concentrated before fractionation and molecular characterization. The most popular method for this purpose is the application of non-ionic macroporous resins at preadjusted acidity. The routine is fractionate further at strongly acidic conditions the obtained mixture of hydrophobic humic solutes into so-called humic and fulvic acids. Quantitatively and in the light of elemental analysis and basic functional groups this fractionation seems to be reliable. However, from the point of view of the structural composition, the precision of the procedure was not so self-evident. The data of nuclear magnetic resonance spectroscopy has proved that it is slightly erratic to repeat from the standard homogeneous water sample the isolation-fractionation for obtaining structurally wholly identical humic and fulvic acids. This deviation was not solely as a result of the technique itself, but also of the highly sensitive nature of the humic solutes.     

Simultaneous analysis of small organic acids and humic acids using high performance size exclusion chromatography

An accurate and fast method for simultaneous determination of small organic acids and much larger humic acids was developed using high performance size exclusion chromatography. Two small organic acids, i.e. salicylic acid and 2,3‐dihydroxybenzoic acid, and one purified humic acid material were used in this study. Under the experimental conditions, the UV peaks of salicylic acid and 2,3‐dihydroxybenzoic acid were well separated from the peaks of humic acid in the chromatogram. Concentrations of the two small organic acids could be accurately determined from their peak areas. The concentration of humic acid in the mixture could then be derived from mass balance calculations. The measured results agreed well with the nominal concentrations. The detection limits are 0.05 mg/L and 0.01 mg/L for salicylic acid and 2,3‐dihydroxybenzoic acid, respectively. Applicability of the method to natural samples was tested using groundwater, glacier, and river water samples (both original and spiked with salicylic acid and 2,3‐dihydroxybenzoic acid) with a total organic carbon concentration ranging from 2.1 to 179.5 mg C/L. The results obtained are promising, especially for groundwater samples and river water samples with a total organic carbon concentration below 9 mg C/L.     

Ultrasound-assisted method for determination of chemical oxygen demand

A method for determination chemical oxygen demand (COD) assisted by use of ultrasound has been successfully evaluated for the first time. The method uses instrumentation simpler and cheaper and, in some instances, safer than that used by previous methods for the same purpose. The new device used for sonication is an all-glass cylindrical sonotrode that can be introduced directly into the reaction mixture. Use of this device enables more efficient interaction between sample and ultrasonic energy. The optimized experimental conditions are high ultrasonic power (55% amplitude, 0.9-second pulses each second), high sulfuric acid concentration (>60%), and a sonication time of 2 min. Under these conditions the method has limitations similar to those of the official COD method with regard to the type of organic compound. It works adequately with easily oxidized organic matter (potassium hydrogen phthalate and dextrose) and other organic compounds difficult to oxidize by conventional methods (e.g. phenol and acetic acid) but the COD values obtained with volatile compounds and difficult organic matter are poor. Chloride is tolerated up to a concentration of 7000 mg L(-1) without any masking agent. Gasification of the sample is recommended to improve results; use of air and argon resulted in no significant differences - bubbling with air during sonication resulted in COD values for certified materials and real wastewater samples statistically identical with the certified COD values and those obtained by the classic (open reflux) method. The use of ultrasound energy for COD determination thus seems to be an interesting and promising alternative to conventional oxidation methods used for the same purpose.     

Measurement of the carbonaceous component in the Milan urban particulate matter

The carbonaceous component in the Milan urban particulate matter, i.e. the two components black carbon (BC) and organic carbon (OC), has been measured by means of a thermogravimetric analyzer combined with an infrared spectrophotometer (TGA/FT-IR). While black carbon may be considered a primary pollutant, organic carbon includes both primary emissions and secondary organic aerosols. Since carbonaceous aerosol (including a small quantity of inorganic carbon, too) makes up roughly from 25% to 50% of the average annual PM 2.5 mass concentration, a deeper understanding of this component is required. The TGA/FT-IR technique, employed for the first time to our knowledge for the quantification of the particulate matter carbonaceous component, allows, thought the results here presented are preliminary, to assess the two components BC and OC in a simple way especially if compared with the methods reported in the literature. The total carbon (TC) determinations performed by TGA/FT-IR on Milan urban particulate matter are in good agreement with the results obtained by a total organic carbon (TOC) analyzer operating directly on the solid sample.