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PubMed1985

Preconcentration of cadmium, chromium, copper and lead in drinking water on the polyacrylic ester resin, XAD-7.

The conditions (e.g. pH, resin, particle size, foreign ions) affecting the uptake of Cd(II), Cr(III), Cu(II) and Pb(II) from aqueous solution by the SM-7 (also called XAD-7) resin, were studied. Based on these studies, a two-column method was developed to overcome the effect of complexation by humic substances. The method was successfully tested with the NBS multielement water standard, SRM 1643a, and was subsequently applied to enrich Cd(II), Cr(III), Cu(II) and Pb(II) in 15 drinking water samples from Hamilton, Ontario. The metals were determined using graphite furnace atomic absorption spectrometry. The results for the drinking water samples showed that leaching of copper and lead occurred from the distribution system.

Acrylic Resins↗

PubMed1987

Determination of methyl- and ethylmercury in natural waters at sub-nanogram per liter using SCF-adsorbent preconcentration procedure.

An analytical procedure for determining methyl- and ethylmercury (MeHg/EtHg) in natural waters is described. MeHg/EtHg was preconcentrated from water on a sulfhydryl cotton fiber (SCF) adsorbent and eluted with a small volume of a mixture of 1 M hydrochloric acid and 2 M sodium chloride. The eluate was extracted with benzene. The measurements of MeHg/EtHg in benzene extract were determined by gas chromatography with electron capture detector. The detection limit for MeHg/EtHg was about 0.04 ng L-1 using a 20 L water sample. The precision was about 20%. The application of the proposed method to one snow and four freshwater samples varying in humus content is described. The MeHg concentrations found in different freshwater samples were ranged from 0.09 to 0.22 ng L-1 and the recoveries of spiked MeHg were ranged from 42 to 68% which were strongly correlated to the content of humic substances. The MeHg concentration found in snow was 0.28 ng L-1 and the recovery was 79%. The analytical results of MeHg concentration in freshwater samples are discussed in relation to the pH used in the preconcentration, the humus content, the fraction of methylmercury in organic bound mercury and mercury in fish.

Adsorption↗

PubMed2005

The influence of ferrous/ferric ions on the efficiency of photocatalytic oxidation of pollutants in groundwater.

The complex influence of ferrous/ferric ions on the efficiency of aqueous photocatalytic oxidation (PCO) of 2-ethoxyethanol (2-EE), methyl tert-butyl ether (MTBE) and humic substances (HS) was established. A drastic efficiency increase at lower concentration of ferrous/ferric ions was observed to change to a sharp decrease at higher concentrations for 2-EE and MTBE, whereas for HS only an inhibitive effect of Fe2+/3+ on the PCO efficiency was noticed. The authors proposed an explanation for the observed phenomena based on the different sensitivities of pollutants towards radical-oxidation reactions and the competitive adsorption of metallic ions and pollutants on the TiO2 surface.

Catalysis↗

PubMed2001

Further formation of trihalomethanes in drinking water during heating.

This study was aimed at investigating the further formation of trihalomethanes (THM) in drinking water when it is being heated at home. Experimental results confirmed that there could be a further significant formation during heating drinking water. Overall variation of THM concentration in water during the heating depended on its formation rate and volatilisation rate. The rate of THM formation was mainly affected by not only both the concentrations of THM precursors, such as humic substances and residual chlorine, but also temperature and reaction time. The rate of THM volatilisation depended on water temperature and the extent of water agitation in the water heaters. It was concluded that the THM residuals in drinking water could be effectively eliminated to a very low level, if the boiling of water was kept in the open for few minutes after water boiling.

Temperature↗

PubMed2001

Molecular shape analysis of a Maillard reaction intermediate.

The Maillard (browning) reaction involving the polycondensation of sugars and amino acids is believed to be an important abiotic pathway for humic substance formation in nature. However, a major drawback is that the Maillard reaction is extremely slow at temperatures encountered under normal environmental conditions. In order to elucidate some details of this process molecular shape analysis was applied to investigate the initial reaction between D-glucose and glycine to form the Amadori compound fructosylglycine which is an intermediate product in the Maillard reaction. The structure of the Amadori compound was optimized at a quantum mechanical level and its ground state electron energy calculated. Molecular Iso-Density Contours (MIDCO's), electron density contour surfaces of constant electron density, were constructed for D-glucose, glycine and fructosylglycine in order to study the steric conditions for the reaction. The calculations indicate that the Amadori compound and water on one hand and the separate entities D-glucose and glycine on the other hand are very similar to each other in terms of their ground state energy. This agrees with the experimental observation that the reaction between D-glucose and glycine to form the Amadori compound is slow.

Glucose↗

PubMed2002

Stability of Ca2+-, Cd2+-, and Cu2+-illite complexes.

In this study, using ion selective electrode techniques, we investigated the influence of pH on metal-ion, Ca2+, Cd2+, and Cu2+, adsorption by Fithian illite. The results showed that Fithian illite exhibited at least two types of metal-ion adsorption sites, high and low strength with the strength of metal-ion-illite surface complexes following the order of Cu2+ > Cd2+ > Ca2+ (strongest to weakest acids) at any of the pH values tested. The ability of metal-ions to form complexes with illite surfaces was affected by type of metal-ions and pH, especially for low metal-ion affinity sites. These sites formed stronger metal-ion complexes at high pH than at low pH, which implicated clay edge sites and indicated that H+ competed with metal-ions for available complexation sites. The data also showed that illite functional groups forming the strongest metal-ion complex did not appear to be pH-sensitive, which implicated wedge siloxane cavities or extremely low pKa clay-edge OH functional groups, but the total number of such sites were very small. The magnitude of the metal-ion-illite stability constants, as metal-ion solution concentration approached zero, on a log-scale, varied from 3.52 to 4.21 for Ca2+, 4.38 to 5.18 for Cd2+, and from 5.23 to 5.83 for Cu2+. These constants were approximately an order of magnitude smaller than those representing illite with sorbed humic fractions. The above results along with the results from our previous studies imply that metal-ion mobility and bioavailability would be affected by soil mineral surface properties, which would be significantly influenced by sorption of humic substances.

Adsorption↗

PubMed2005

Blackfoot disease and arsenic: a never-ending story.

Blackfoot disease (BFD) is an endemic peripheral vascular disease confined to the southwestern coast of Taiwan. This article reviews the epidemiology, clinical manifestations and diagnosis, pathology, etiology and pathogenesis of this disease. Sporadic cases of BFD occurred as early as in the early 20th century, and peak incidence was noted between 1956 and 1960, with prevalence rates ranging from 6.51 to 18.85 per 1,000 population in different villages. Typical clinical symptoms and signs of progressive arterial occlusion mainly found in the lower extremities, but in rare cases, the upper extremities might also be involved. Ulceration, gangrene and spontaneous or surgical amputation were typical fate. An extensive pathological study concluded that 30% of the BFD patients had histologic lesions compatible with thromboangiitis obliterans and 70% showed changes of arteriosclerosis obliterans. Epidemiologic studies carried out since mid-20th century revealed that BFD was associated with the consumption of inorganic arsenic from the artesian wells. Recent studies confirmed the existence of preclinical peripheral vascular disease, subclinical arterial insufficiency and defects in cutaneous microcirculation in the residents of the endemic villages. A more recent study suggested that the methylation capacity of arsenic can interact with arsenic exposure in the development of peripheral vascular disease among residents of BFD-endemic areas. The incidence of BFD decreased dramatically after the implementation of tap water in these villages over the past 2-3 decades. The atherogenicity of arsenic could be associated with its effects of hypercoagulability, endothelial injury, smooth muscle cell proliferation, somatic mutation, oxidative stress, and apoptosis. However, its interaction with some trace elements and its association with hypertension and diabetes mellitus could also explain part of its higher risk of developing atherosclerosis. Although humic substances have also been suggested as a possible cause of BFD, epidemiologic studies are required to confirm its etiologic role.

Arsenic↗

PubMed2004

Solid-phase microextraction and gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in environmental solid matrices.

A solid-phase microextraction (SPME) and gas chromatography-mass spectrometry method for determining polycyclic aromatic hydrocarbons (PAHs) in environmental solid matrices is developed. Investigated matrices include seaweed (Undaria pinnatifida and Himanthalia elongata), humic substances (isolated from a wetland out-flow and purchased from Aldrich), and soil. Optimal conditions for a good SPME efficiency of 16 hydrocarbon compounds are obtained using a 100- micro m polydimethylsiloxane fiber directly immersed in aqueous carrier medium. The method is remarkable for presenting short extraction times and considerably high sensitivities. The SPME results obtained by using internal calibration give the total analyte concentration based on the identical partitioning behavior of native and spiked pollutants. The detection limits range from 0.001 to 0.1 mg of PAH per kilogram of dry matrix. SPME external calibration provides information regarding freely dissolved analytes. The detection limits range from 0.001 to 0.05 micro g of PAH per liter of carrier medium. The SPME with external calibration procedure can be applied to measure free concentrations of a target compound spiked into a carrier medium and onto a matrix. Based on a comparison of results obtained for the two samples, the partitioning of the target analyte between the matrix and the carrier medium is calculated.

Calibration↗

PubMed2002

Luminescence intensity in coral skeletons from Mona Island in the Caribbean Sea and its link to precipitation and wind speed.

This study investigates the potential of using changes of interannual luminescence intensity in hermatypic Montastraea coral skeletons in the northeastern Caribbean as a proxy of precipitation and (trade) wind speed. In order to find wavelength pairs that are well suited to detect variations in the concentration of incorporated terrestrial humic substances in coral skeletons, and thus to reconstruct past run-off and rainfall, three-dimensional excitation-emission matrix fluorescence spectra of seawater samples were investigated on their relationships to local precipitation. Three prominent excitation-emission peaks at 310/430, 425/480 and 390/530 nm were identified. The fluorescence intensities of the wavelength pair 310/430 nm showed a weak relationship, while the wavelength pairs at 425/480 and 390/530 nm showed strong relationships with local precipitation. Variations in luminescence intensities from scans on the coral surface along the growth axis using the wavelengths identified were then compared with instrumental records of regional precipitation and wind speed. In the coral skeleton as well, the wavelength pairs at 425/480 and 390/530 nm were more strongly correlated with regional precipitation and wind speed. This indicates that these two wavelength pairs are well suited to reconstruct past precipitation and wind speed. In order to evaluate the use as a proxy of trade wind variability in the Caribbean, tropical Atlantic region, variations in luminescence intensity were compared with a record of trade wind variability from the southern Caribbean. The two records are strongly correlated, which suggests that luminescence intensity in coral skeletons, at least from Mona Island, can be used as proxy of trade wind variability and precipitation.

Anthozoa↗

PubMed2002

Uranium speciation and bioavailability in aquatic systems: an overview.

The speciation of uranium (U) in relation to its bioavailability is reviewed for surface waters (fresh- and seawater) and their sediments. A summary of available analytical and modeling techniques for determining U speciation is also presented. U(VI) is the major form of U in oxic surface waters, while U(IV) is the major form in anoxic waters. The bioavailability of U (i.e., its ability to bind to or traverse the cell surface of an organism) is dependent on its speciation, or physicochemical form. U occurs in surface waters in a variety of physicochemical forms, including the free metal ion (U4+ or UO2(2+)) and complexes with inorganic ligands (e.g., uranyl carbonate or uranyl phosphate), and humic substances (HS) (e.g., uranyl fulvate) in dissolved, colloidal, and/or particulate forms. Although the relationship between U speciation and bioavailability is complex, there is reasonable evidence to indicate that UO2(2+) and UO2OH+ are the major forms of U(VI) available to organisms, rather than U in strong complexes (e.g., uranyl fulvate) or adsorbed to colloidal and/or particulate matter. U(VI) complexes with inorganic ligands (e.g., carbonate or phosphate) and HS apparently reduce the bioavailability of U by reducing the activity of UO2(2+) and UO2OH+. The majority of studies have used the results from thermodynamic speciation modeling to support these conclusions. Time-resolved laser-induced fluorescence spectroscopy is the only analytical technique able to directly determine specific U species, but is limited in use to freshwaters of low pH and ionic strength. Nearly all of the available information relating the speciation of U to its bioavailability has been derived using simple, chemically defined experimental freshwaters, rather than natural waters. No data are available for estuarine or seawater. Furthermore, there are no available data on the relationship between U speciation and bioavailability in sediments. An understanding of this relationship has been hindered due to the lack of direct quantitative U speciation techniques for particulate phases. More robust analytical techniques for determining the speciation of U in natural surface waters are needed before the relationship between U speciation and bioavailability can be clarified.

Animals↗

PubMed2006

Exocellular electron transfer in anaerobic microbial communities.

Exocellular electron transfer plays an important role in anaerobic microbial communities that degrade organic matter. Interspecies hydrogen transfer between microorganisms is the driving force for complete biodegradation in methanogenic environments. Many organic compounds are degraded by obligatory syntrophic consortia of proton-reducing acetogenic bacteria and hydrogen-consuming methanogenic archaea. Anaerobic microorganisms that use insoluble electron acceptors for growth, such as iron- and manganese-oxide as well as inert graphite electrodes in microbial fuel cells, also transfer electrons exocellularly. Soluble compounds, like humic substances, quinones, phenazines and riboflavin, can function as exocellular electron mediators enhancing this type of anaerobic respiration. However, direct electron transfer by cell-cell contact is important as well. This review addresses the mechanisms of exocellular electron transfer in anaerobic microbial communities. There are fundamental differences but also similarities between electron transfer to another microorganism or to an insoluble electron acceptor. The physical separation of the electron donor and electron acceptor metabolism allows energy conservation in compounds as methane and hydrogen or as electricity. Furthermore, this separation is essential in the donation or acceptance of electrons in some environmental technological processes, e.g. soil remediation, wastewater purification and corrosion.

Anaerobiosis↗

PubMed2007

Identification of acetate-utilizing Bacteria and Archaea in methanogenic profundal sediments of Lake Kinneret (Israel) by stable isotope probing of rRNA.

Acetate is an important intermediate in the decomposition of organic matter in anoxic freshwater sediments. Here, we identified distinct microorganisms active in its oxidation and transformation to methane in the anoxic methanogenic layers of Lake Kinneret (Israel) profundal sediment by rRNA-based stable isotope probing (RNA-SIP). After 18 days of incubation with amended [U-(13)C]acetate we found that archaeal 16S rRNA was (13)C-labelled to a far greater extent than bacterial rRNA. We identified acetoclastic methanogens related to Methanosaeta concilii as being most active in the degradation and assimilation of acetate. Oxidation of the acetate-methyl group played only a minor role, but nevertheless 'heavy'(13)C-labelled bacterial rRNA templates were identified. 'Heavy' bacteria were mainly affiliated with the Betaproteobacteria (mostly Rhodocyclales and Nitrosomonadales), the Nitrospira phylum (related to 'Magnetobacterium bavaricum' and Thermodesulfovibrio yellowstonii), and also with the candidate phylum 'Endomicrobia'. However, the mode of energy gain that allowed for the assimilation of (13)C-acetate by these bacterial groups remains unknown. It may have involved syntrophic oxidation of acetate, reduction of chlorinated compounds, reduction of humic substances, fermentation of organic compounds, or even predation of (13)C-labelled Methanosaeta spp. In summary, this SIP experiment shows that acetate carbon was predominantly consumed by acetoclastic methanogens in profundal Lake Kinneret sediment, while it was also utilized by a small and heterogeneous community of bacteria.

Acetates↗

PubMed2006

Fungal laccases - occurrence and properties.

Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds.

Biotechnology↗

PubMed2000

Dissimilatory metal reduction by the facultative anaerobe Pantoea agglomerans SP1.

Anaerobic enrichments with acetate as the electron donor and Fe(III) as the terminal electron acceptor were obtained from sediments of Salt Pond, a coastal marine basin near Woods Hole, Mass. A pure culture of a facultatively anaerobic Fe(III) reducer was isolated, and 16S rRNA analysis demonstrated that this organism was most closely related to Pantoea (formerly Enterobacter) agglomerans, a member of the family Enterobacteriaceae within the gamma subdivision of the Proteobacteria. This organism, designated strain SP1, can grow by coupling the oxidation of acetate or H(2) to the reduction of a variety of electron acceptors, including Fe(III), Mn(IV), Cr(VI), and the humic substance analog 2,6-anthraquinone disulfonate, but not sulfate. To our knowledge, this is the first mesophilic facultative anaerobe reported to couple acetate oxidation to dissimilatory metal reduction.

Acetates↗

PubMed2005

Abundance, activity, and community structure of pelagic methane-oxidizing bacteria in temperate lakes.

The abundance and activity of methane-oxidizing bacteria (MOB) in the water column were investigated in three lakes with different contents of nutrients and humic substances. The abundance of MOB was determined by analysis of group-specific phospholipid fatty acids from type I and type II MOB, and in situ activity was measured with a 14CH4 transformation method. The fatty acid analyses indicated that type I MOB most similar to species of Methylomonas, Methylomicrobium, and Methylosarcina made a substantial contribution (up to 41%) to the total bacterial biomass, whereas fatty acids from type II MOB generally had very low concentrations. The MOB biomass and oxidation activity were positively correlated and were highest in the hypo- and metalimnion during summer stratification, whereas under ice during winter, maxima occurred close to the sediments. The methanotroph biomass-specific oxidation rate (V) ranged from 0.001 to 2.77 mg CH4-C mg(-1) C day(-1) and was positively correlated with methane concentration, suggesting that methane supply largely determined the activity and biomass distribution of MOB. Our results demonstrate that type I MOB often are a large component of pelagic bacterial communities in temperate lakes. They represent a potentially important pathway for reentry of carbon and energy into pelagic food webs that would otherwise be lost as evasion of CH4.

Biomass↗

PubMed2002

Metabolic diversity in aromatic compound utilization by anaerobic microbes.

A vast array of structurally diverse aromatic compounds is continually released into the environment due to the decomposition of green plants and as a consequence of human industrial activities. Increasing numbers of bacteria that utilize aromatic compounds in the absence of oxygen have been brought into pure culture in recent years. These include most major metabolic types of anaerobic heterotrophs and acetogenic bacteria. Diverse microbes utilize aromatic compounds for diverse purposes. Chlorinated aromatic compounds can serve as electron acceptors in dehalorespiration. Humic substances serve as electron shuttles to enable the use of inorganic electron acceptors, such as insoluble iron oxides, that are not always easily reduced by microbes. Substituents that are attached to aromatic rings may serve as carbon or energy sources for microbes. Examples include acyl side chains and methyl groups. Finally, aromatic compounds can be completely degraded to serve as carbon and energy sources. Routes by which various types of aromatic compounds, including toluene, ethylbenzene, phenol, benzoate, and dihydroxylated compounds, are degraded have been elucidated in recent years. Biochemical strategies employed by microbes to destabilize the aromatic ring in preparation for degradation have become apparent from this work.

Anaerobiosis↗

PubMed2003

Sorption of phenanthrene and atrazine by plant cuticular fractions.

Several studies have shown selective preservation of plant cuticular materials in soils. However, very little is known about their function as sorbents for the hydrophobic organic contaminants (HOCs) in the soil. In this study, we investigated the sorption and desorption of phenanthrene and atrazine by cuticular fractions of pepper (bulk, dewaxed, nonsaponifiable, and nonhydrolyzable) to better understand the sorptive activity of cuticular matter in soils. The bulk and dewaxed cuticles exhibited carbon-normalized distribution coefficients (Koc) for phenanthrene and atrazine in the range of that reported for soil humic substances, although both samples were rich in aliphatic structures. No hysteresis was observed in the desorption isotherms of either solute. The nonhydrolyzable residue exhibited a very high Koc value for atrazine, whereas the nonsaponifiable sample be exhibited the lowest Koc value for both sorbates. Based on solubility parameter data, it is suggested that the nonsponifiable sample be considered an intermediate between the physical and chemical mixture of pectin and cutan/lignin-like fractions, whereas the dewaxed cuticle is a chemical blending of cutin and pectin. The n-hexane-normalized sorption data suggest that the pepper cuticle can interact specifically with atrazine. This study leads to the conclusion that the contribution of aliphatic-rich plant biopolymers to the sorption of HOCs can be significant because of their preservation and accumulation in soils.

Adsorption↗

PubMedDate not supplied

Photodegradation of selected herbicides in various natural waters and soils under environmental conditions.

The photochemical degradation of herbicides belonging to different chemical groups has been investigated in different types of natural waters (ground, river, lake, marine) and distilled water as well as in soils with different texture and composition. Studied herbicides and chemical groups included atrazine, propazine, and prometryne (s-triazines); propachlor and propanil (acetanilides); and molinate (thiocarbamate). The degradation kinetics were monitored under natural conditions of sunlight and temperature. Photodegradation experiments were performed in May through July 1998 at low concentrations in water samples (2-10 mg/L) and soil samples (5-20 mg/kg), which are close to usual field dosage. The photodegradation rates of all studied herbicides in different natural waters followed a pseudo-first order kinetics. The half-lives of the selected herbicides varied from 26 to 73 calendar days in waters and from 12 to 40 d in soil surfaces, showing that the degradation process depends on the constitution of the irradiated media. The presence of humic substances in the lake, river, and marine water samples reduces degradation rates in comparison with the distilled and ground water. On the contrary, the degradation in soil is accelerated as the percentage of organic matter increases. Generally, the photodegradation process in soil is faster than in water. The major photodegradation products identified by using gas chromatography-mass spectrometry (GC-MS) techniques were the hydroxy and dealkylated derivatives for s-triazines, the dechlorinated and hydroxy derivative for the anilides, and the keto-derivative for the thiocarbamate, indicating a similar mode of degradation for each chemical category.

Gas Chromatography-Mass Spectrometry↗