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At least 631 records · Page 35Linked to original sources

PubMed2005

Continuous on-line determination of methyl tert-butyl ether in water samples using ion mobility spectrometry.

A rapid analytical procedure for the on-line determination of methyl tert-butyl ether (MTBE) in water samples was developed. A new membrane extraction unit was used to extract the MTBE from water samples. The concentration of MTBE was determined using ion mobility spectrometry with 63Ni ionization and corona discharge ionization without chromatographic separation. Both ionization methods permit the sensitive determination of MTBE. A detection limit of 100 microg/L was established for the on-line procedure. Neither the inorganic compounds, humic substances nor gasoline were found to exert a significant influence on the peak intensity of the MTBE. The screening procedure can be used for concentrations of monoaromatic compounds (benzene, toluene, xylene) up to 600 microg/L. No sample preparation is required and the analysis results are available within 5 min. In order to determine concentrations between 10 microg/L and 100 microg/L, a discontinuous procedure was developed on the basis of the same experimental set-up.

Benzene↗

PubMed2004

Determination of solid-liquid partition coefficients (Kd) for the herbicides isoproturon and trifluralin in five UK agricultural soils.

Isoproturon and trifluralin are herbicides of contrasting chemical characters and modes of action. Standard batch sorption procedures were carried out to investigate the individual sorption behaviour of 14C-isoproturon and 14C-trifluralin in five agricultural soils (1.8-4.2% OC), and the soil solid-liquid partition coefficients (Kd values) were determined. Trifluralin exhibited strong partitioning to the soil solid phase (Kd range 106-294) and low desorption potential, thus should not pose a threat to sensitive waters via leaching, although particle erosion and preferential flow pathways may facilitate transport. For isoproturon, soil adsorption was low (Kd range 1.96-5.75) and desorption was high, suggesting a high leaching potential, consistent with isoproturon being the most frequently found pesticide in UK surface waters. Soil partitioning was directly related to soil organic carbon (OC) content. Accumulation isotherms were modelled using a dual-phase adsorption model to estimate adsorption and desorption rate coefficients. Associations between herbicides and soil humic substances were also shown using gel filtration chromatography.

Adsorption↗

PubMed2005

Ectomycorrhizas impede phytoremediation of polycyclic aromatic hydrocarbons (PAHs) both within and beyond the rhizosphere.

Exploitation of mycorrhizas to enhance phytoremediation of organic pollutants has received attention recently due to their positive effects on establishment of plants in polluted soils. Some evidence exist that ectomycorrhizas enhance the degradation of pollutants of low recalcitrance, while less easily degradable polyaromatic molecules have been degraded only by some of these fungi in vitro. Natural polyaromatic (humic) substances are degraded more slowly in soil where ectomycorrhizal fungi are present, thus phytoremediation of recalcitrant pollutants may not benefit from the presence of these fungi. Using a soil spiked with three polycyclic aromatic hydrocarbons (PAHs) and an industrially polluted soil (1 g kg(-1) of summation operator12 PAHs), we show that the ectomycorrhizal fungus Suillus bovinus, forming hydrophobic mycelium in soil that would easily enter into contact with hydrophobic pollutants, impedes rather than promotes PAH degradation. This result is likely to be a nutrient depletion effect caused by fungal scavenging of mineral nutrients.

Biodegradation, Environmental↗

PubMed2006

Occurrence of laccases in lichenized ascomycetes of the Peltigerineae.

Following our previous findings of high extracellular redox activity in lichens, the results of the work presented here identify the enzymes involved as laccases. Despite numerous data on laccases in fungi and flowering plants, this is the first report of the occurrence of laccases in lichenized ascomycetes. Extracellular laccase activity was measured in 40 species of lichens from different taxonomic groupings and contrasting habitats. Out of 20 species tested from suborder Peltigerineae, 18 displayed laccase activity, while activity was absent in species tested from other lichen groups. Identification of the enzymes as laccases was confirmed by the ability of lichen leachates to readily metabolize substrates such as 2,2'-azino(bis-3-ethylbenzthiazoline-6-sulfonate) (ABTS), syringaldazine and o-tolidine in the absence of hydrogen peroxide, sensitivity of the enzymes to cyanide and azide, the enzymes having typical laccase pH and temperature optima, and an absorption spectrum with a peak at 614nm. Desiccation and wounding stimulated laccase activity. Laccase activity was not increased after treatment with normal inducers of laccase synthesis, suggesting that they are constitutively expressed. Electrophoresis showed that the active form of laccase from Peltigera malacea was a tetramer with an unusually high molecular mass of 340kDa and an isoelectric point (pI) of 4.7. The finding of abundant extracellular redox enzymes known to actively produce reactive oxygen species suggest that their roles may include increasing nutrient supply to lichens by delignification, and deterring pathogens by contributing to the oxidative burst. Furthermore, once released into the environment, they may participate in the carbon cycle by facilitating the breakdown or formation of humic substances.

Ascomycota↗

PubMed2004

Larvicidal Cry proteins from Bacillus thuringiensis are released in root exudates of transgenic B. thuringiensis corn, potato, and rice but not of B. thuringiensis canola, cotton, and tobacco.

Larvicidal proteins encoded by cry genes from Bacillus thuringiensis were released in root exudates from transgenic B. thuringiensis corn, rice, and potato but not from B. thuringiensis canola, cotton, and tobacco. Nonsterile soil and sterile hydroponic solution in which B. thuringiensis corn, rice, or potato had been grown were immunologically positive for the presence of the Cry proteins; from B. thuringiensis corn and rice, the soil and solution were toxic to the larva of the tobacco hornworm (Manduca sexta), and from potato, to the larva of the Colorado potato beetle (Leptinotarsa decemlineata), representative lepidoptera and coleoptera, respectively. No toxin was detected immunologically or by larvicidal assay in soil or hydroponic solution in which B. thuringiensis canola, cotton, or tobacco, as well as all near-isogenic non-B. thuringiensis plant counterparts or no plants, had been grown. All plant species had the cauliflower mosaic virus (CaMV) 35S promoter, except rice, which had the ubiquitin promoter from maize. The reasons for the differences between species in the exudation from roots of the toxins are not known. The released toxins persisted in soil as the result of their binding on surface-active particles (e.g. clay minerals, humic substances), which reduced their biodegradation. The release of the toxins in root exudates could enhance the control of target insect pests, constitute a hazard to nontarget organisms, and/or increase the selection of toxin-resistant target insects.

Bacterial Proteins↗

PubMed2006

Drain blocking: an effective treatment for reducing dissolved organic carbon loss and water discolouration in a drained peatland.

Peatlands are an important terrestrial carbon store. However, heightened levels of degradation in response to environmental change have resulted in an increased loss of dissolved organic carbon (DOC) and an associated rise in the level of discolouration in catchment waters. A significant threat to peatland sustainability has been the installation of artificial drainage ditches. However, recent restoration schemes have pursued drain blocking as a possible strategy for reducing degradation, fluvial carbon loss and water discolouration. This paper investigates the effect of open cut drainage and the impact of drain blocking on DOC and colour dynamics in blanket peat soil-water solutions. Three treatments (intact peat, drained peat and drain-blocked peat) were monitored in an upland blanket peat catchment in the UK. DOC and colour values were significantly higher on the drained slopes compared with those of the intact peat, which in turn had greater DOC and colour values than the drain-blocked slopes. Consequently, drain blocking is shown to be a highly successful technique in reducing both the DOC concentration and level of discolouration in soil waters, even to values lower than those observed for the intact site, which suggests a process of store exhaustion and flushing may operate. The colour per carbon unit (C/C) ratio was significantly higher at the drain-blocked site than either the intact or the drained treatments, while the E4/E6 ratio (fulvic acid/humic acid) was significantly lower at the blocked site compared to the two other treatments. The high C/C and low E4/E6 ratios indicate that drain blocking also modifies the composition of DOC, such that darker-coloured humic substances become more dominant compared to the intact site. This implies disturbance to DOC production and/or transportation processes operating within the peat.

Carbon↗

PubMed2006

Photochemical reduction and reoxidation of aqueous mercuric chloride in the presence of ferrioxalate and air.

In this study, ferric oxalate is used to represent the photosensitive Fe(III) complexes as well as the diacid compounds which are at significant concentrations in cloud and rain droplets. Because of the common carboxylate functional group; ferric oxalate is also used as a model to represent humic substances found in natural water. UVA irradiation of aqueous acidic mercuric chloride (pH 1-4) in the presence of an excess of ferrioxalate results in partial reduction of the mercuric ion to elemental mercury. The pseudo-first-order rate constant "kobs" for the photoreduction reaction is pH-dependent as is the yield of residual Hg(II). When exposed to visible irradiation the rate is about 10 times slower and no reaction was observed in the dark. The inferred mechanism of photoreduction involves the reaction of Hg(II) with a secondary photoproduct, the strongly reducing radical anion CO2-*. In the presence of dissolved oxygen, competition for CO2-* between Hg(II) and O2 reduces the rate and efficiency of mercuric ion reduction. The O2-*/HO2 products do not reduce Hg(II). On the contrary, their disproportionation leads to the formation of H2O2 which causes a re-oxidation of Hg(0) at pH values of <or=4. Chloride ion decreases the rate of the reduction of Hg(II).

Air Pollutants↗

PubMed2005

Effects of cement on redistribution of trace metals and dissolution of organics in sewage sludge and its inorganic waste-amended products.

The suitability of using cement-stabilized sludge products as artificial soils in earth works was evaluated. The sludge products investigated were cemented sludge, cement-treated clay-amended sludge (SS+MC), and cement-treated copper slag-amended sludge (SS+CS). The leachability of lead (Pb), zinc (Zn), copper (Cu), and chromium (Cr) were assessed using the sequential extraction technique, toxicity characteristic leaching procedure (TCLP), NEN 7341 availability test, and column leaching test. The results indicated that Zn leachability was reduced in all the cement-stabilized sludge products. In contrast, Cu was transferred from the organic fraction to the readily leachable phases in the cement-stabilized sludge products and therefore exhibited increased leachability. The increased Cu leachability could be attributed to dissolution of humic substances in the sludge as a result of elevated pH. Good correlation between dissolved organic carbon (DOC) and heavy metal leaching from the cement-stabilized sludge products was observed in the column leaching experiment. Even with a cement percentage as small as 12.5%, calcium silicate hydrate (C-S-H) was formed in the SS+MC and SS+CS products. Inclusion of the marine clay in the SS+MC products could reduce the leaching potentials of Zn, and this was the great advantage of the marine clay over the copper slag for sludge amendment.

Metals, Heavy↗

PubMed2004

Freshwater phytoplankton quantification by chlorophyll a: a comparative study of in vitro, in vivo and in situ methods.

Standard ISO method for chlorophyll a quantification (extraction into ethanol, spectrophotometrical quantification at 665 and 750 nm), spectrofluorometry (reader for 96 wells, excitation 410 nm, emission 670 nm), and a submersible fluorescence probe for in situ phytoplankton quantification (excitation 410, 525, 570, 590, and 610 nm, emission 685 nm) were compared in different freshwater environments-reservoirs and rivers. The ISO method is accepted as a standard method but requires sample handling and transport to the laboratory. Spectrofluorometry is a sensitive method, even for natural phytoplankton populations. Nevertheless, it cannot be recommended for the quantification of cyanobacterial water blooms because colonial and filamentous species such as Microcystis, Anabaena, or Aphanizomenon display unacceptable variability (18-33%). The submersible probe featured high correlation with a standard ISO method (r=0.97, P<0.05). This probe can provide the selective measurement of technologically important phytoplankton groups like cyanobacteria, diatoms, green algae, and cryptophytes in lake vertical profiles of up to 100 m. The limitation of this instrument is the possible reabsorption of the light signal, e.g. in the presence of humic substances, or dense algal blooms. The use of submersible probes for in situ phytoplankton quantification can be recommended as a sensitive tool for water management, especially in the case of drinking water resources.

Chlorophyll↗

PubMed2004

Characterization of natural organic matter fractions separated by ultrafiltration using flow field-flow fractionation.

Natural organic matter (NOM) from two sites in South Australia were separated by Amicon YM and YC ultrafiltration (UF) membranes into five nominal fractions (<0.5, 0.5-3, 3-10, 10-30 and >30 kDa). These nominal fractions were then characterized for size and molecular weight (MW) distributions using flow field-flow fractionation. The results show that separation by UF did not produce fractions with the expected MW and size. Electrophoretic mobility measurements of the NOM fractions adsorbed to colloidal goethite showed no significant difference between the fractions. However solid-state (13)C NMR of the NOM fractions showed that the separation was influenced by molecular structure as well as molecular size. The results suggest that great caution needs to be exercised when interpreting molecular size and speciation results for humic substances obtained by membrane UF.

Adsorption↗

PubMed2004

An electrospray ionization-tandem mass spectrometry method for identifying chlorinated drinking water disinfection byproducts.

Identification of chlorinated drinking water disinfection byproducts (DBPs) was investigated by using electrospray ionization-mass spectrometry/mass spectrometry (ESI-MS/MS). Chlorine-containing compounds were found to form chloride ion fragments by MS/MS, which can be used as a 'fingerprint' for chlorinated DBPs. Instrumental parameters that affect the formation of chloride ions by ESI-MS/MS were examined, and appropriate conditions for use in finding specific structural information were evaluated. The results show that maximizing the formation of chloride ions by MS/MS required a relatively high collision energy and collision gas pressure; also, limiting the scan range to m/z 30-40 allowed improved sensitivity for detection; but obtaining structural information required the use of lower collision energies. The conditions obtained were demonstrated to be effective in identifying chlorinated DBPs in a standard sample with relatively low concentrations of each component and in a chlorinated humic substance sample. Sample pretreatment techniques including ultrafiltration and size exclusion chromatography appeared to be helpful for identifying highly polar or high molecular weight chlorine-containing DBPs by ESI-MS/MS.

Chlorine↗

PubMed2005

Hybrid photocatalysis/membrane treatment for surface waters containing low concentrations of natural organic matters.

Since the mid-1990s, numerous studies on the treatment of drinking water by photocatalysis have been reported. Once optimised, the photocatalytic process can completely degrade numerous natural and artificial organic compounds. In this study, a hybrid photocatalysis/membrane process was used as a polishing treatment of surface water containing a small concentration of natural organic matters (i.e. total organic carbon (TOC) concentration of around 3mg/L) which may be difficult to remove using conventional filtration or coagulation. An optimum pH of 4.5 and a TiO(2) concentration of 0.1g/L were found to lead to the highest removal efficiencies. The relative effect of the individual processes featuring in the hybrid system (UV radiation, TiO(2) adsorption and membrane filtration) was also assessed for different pH values. The membrane separation process was accounted to remove around 18% of the initial TOC concentration, while TiO(2) adsorption alone was generally responsible for less than 5% of TOC removal during the 120 min of the experiments. However, when the natural water was only radiated by UV light, up to 70% of TOC was removed. A synergetic effect was observed when the three processes (TiO(2), UV and membrane) were used together. Comparison of removal efficiencies obtained during real and model (International Humic Substance Society) waters treatment by photocatalysis is also presented, revealing the importance of the nature of the feed in this type of treatment.

Catalysis↗

PubMed2006

Sorption of cesium, cobalt and europium on low-rank coal and chitosan.

Potential low-cost sorbents of metals based on combined action of coal and chitosan have been investigated. Sorption of Cs, Co and Eu on oxidized coals in mixture with chitosan was studied as function of pH ( approximately 3-6) in batch experiments using radiotracer method. An improved sorption efficiency of the coal sorbents at neutral pH was obtained in mixture with chitosan, namely for oxihumolite at sorption of Eu and Co. Chitosan prevented deterioration of the sorption ability of coal with pH increase probably via retaining the soluble complexes with humic substances leached from coal by formation of an insoluble complex. The effect of chitosan addition was negligible or reverse in case of lignite upon acidification, where the interaction takes place preferentially on the coal surface and may restrict availability of the binding sites for metal ions.

Adsorption↗

PubMed1998

In vitro cytotoxicity of IgG antibodies on vascular endothelial cells from patients with endemic peripheral vascular disease in Taiwan.

A unique peripheral vascular disorder called 'blackfoot disease' is endemic in a limited area on the south-west coast of Taiwan. Clinically, the signs and symptoms of blackfoot disease (BFD) are similar to those of arteriosclerosis and Buerger's disease. A destruction of vascular endothelial cells (ECs) takes place at an early stage in the affected limbs. Currently, the cause of BFD is believed to be artesian drinking water containing a high concentration of arsenic and/or humic substances, although the mechanism of EC destruction is not entirely understood. The purpose of the present study was to examine the factors related to EC damage in BFD. Thus, we investigated the effects of purified IgG collected from patients with BFD (BFD-IgG) and from normal controls (N-IgG) on cultured EC. We found that: (1) EC binding activity of BFD-IgG was significantly higher than that of N-IgG; (2) BFD-IgG, at a concentration higher than 100 microg/ml but not N-IgG, induced concentration-dependent EC cytotoxicity; (3) BFD-IgG at a concentration of 100 microg/ml stimulated neither the release of von Willebrand factor nor the expression of intercellular adhesion molecule-1 by EC. Fluorescent video microscopic examination revealed an increase in transcapillary and interstitial diffusion of nailfold capillary loops in clinically normal fingers of BFD patients. These findings strongly suggested that immunological mechanisms played a significant role in the pathogenesis of BFD. We propose that only persons who produce the IgG anti-endothelial cell antibody are potential victims of BFD.

Antibodies, Anti-Idiotypic↗

PubMed2000

On-line dual-precolumn-based trace enrichment for the determination of polar and acidic microcontaminants in river water by liquid chromatography with diode-array UV and tandem mass spectrometric detection.

Dual-pre-column-based trace enrichment combined on-line with liquid chromatography-diode-array UV and tandem mass spectrometric detection was used to determine a wide polarity range of organic microcontaminants in river water. Various sorbents were studied for their extraction efficiency of (highly) polar and acidic compounds and their ability to selectively remove humic substances, which are normally co-extracted and interfere in the UV detection of polar microcontaminants. An optimised on-line dual-pre-column set-up with PLRP-S in the first pre-column and Hysphere-1 in the second pre-column was used to study the analytical performance of the procedure. Tandem MS was used for confirmation purposes and to quantify the organic microcontaminants in river water at the low-ng/l level. In addition, the influence of the type of sample (drinking and river water) on suppression of analyte responses in electrospray ionization MS was studied.

Chromatography, Liquid↗

PubMed2002

Fingerprinting of natural organic matter by capillary zone electrophoresis using organic modifiers and pattern recognition analysis.

Capillary zone electrophoresis was used for characterising nine samples of natural organic matter (NOM) using phosphate buffer (25 mM, pH 7) and various modifiers; methanol (50 mM), acetonitrile (10%,v/v), dimethyl sulfoxide (5%,v/v), and urea (5 M). Principal component analysis (PCA) was used to examine whether the electrophoretic profiles can be utilised as fingerprints for tracing the NOM samples to their source and/or type of location. It was found that all modifiers except methanol affect the electropherograms. Furthermore, it was found that the PCA analysis carried out on the electrophoretic profiles recorded in buffer solution modified by urea gave the best results for fingerprinting. The distribution of the fingerprints suggests a model for the humic substances in which all samples can be regarded as mixtures between two endmembers: autochtonous and allocthoneous NOM.

Acetonitriles↗

PubMed1999

Semi-permeable surface analytical reversed-phase column for the improved trace analysis of acidic pesticides in water with coupled-column reversed-phase liquid chromatography with UV detection. Determination of bromoxynil and bentazone in surface water.

The coupled-column (LC-LC) configuration consisting of a 3 microm C18 column (50 x 4.6 mm I.D.) as the first column and a 5 microm C18 semi-permeable-surface (SPS) column (150 x 4.6 mm I.D.) as the second column appeared to be successful for the screening of acidic pesticides in surface water samples. In comparison to LC-LC employing two C18 columns, the combination of C18/SPS-C18 significantly decreased the baseline deviation caused by the hump of the co-extracted humic substances when using UV detection (217 nm). The developed LC-LC procedure allowed the simultaneous determination of the target analytes bentazone and bromoxynil in uncleaned extracts of surface water samples to a level of 0.05 microg/l in less than 15 min. In combination with a simple solid-phase extraction step (200 ml of water on a 500 mg C18-bonded silica) the analytical procedure provides a high sample throughput. During a period of about five months more than 200 ditch-water samples originating from agricultural locations were analyzed with the developed procedure. Validation of the method was performed by randomly analyzing recoveries of water samples spiked at levels of 0.1 microg/l (n=10), 0.5 microg/l (n=7) and 2.5 microg/l (n=4). Weighted regression of the recovery data showed that the method provides overall recoveries of 95 and 100% for bentazone and bromoxynil, respectively, with corresponding intra-laboratory reproducibilities of 10 and 11%, respectively. Confirmation of the analytes in part of the samples extracts was carried out with GC-negative ion chemical ionization MS involving a derivatization step with bis(trifluoromethyl)benzyl bromide. No false negatives or positives were observed.

Benzothiadiazines↗

PubMed2003

Metal ions binding onto a lignocellulosic substrate extracted from wheat bran: a NICA-Donnan approach.

In this study ion binding to solid organic matter was investigated. We used the NICA-Donnan model to describe the interaction between Cu(II), Pb(II), and Cd(II) ions and a lignocellulosic substrate extracted from wheat bran. Such a material represents a very cheap and flexible substrate, which can be used as a natural filter to remove toxic metal ions from industrial effluents or applied in the decontamination and rehabilitation of abandoned industrial sites. Moreover, such a material also represents a very simple model of natural organic matter derived from lignin and cellulose, for which there is now a lack of thermodynamic data as far as their interaction with toxic metal ions is concerned. Experimental results were obtained in various conditions of pH and ionic strength. In our modeling, we used the acidity constants and the concentration of sites that were determined in a previous work. The parameters deduced from the NICA-Donnan model were also compared to thermodynamic data available for other cases of natural organic matter, mainly humic substances.

Adsorption↗