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PubMed2006

Photodegradation of endocrine disrupting chemical nonylphenol by simulated solar UV-irradiation.

The photolysis of nonylphenol (NP) was investigated using a solar simulator in the absence/presence of dissolved organic matter (DOM), HCO3-, NO3- and Fe(III) ions. The effects of different parameters such as initial pH, initial concentration of substrate, temperature, and the effect of hydrogen peroxide concentration on photodegradation of nonylphenol in aqueous solution have been assessed. The results indicate that the oxidation rate increases in the presence of H2O2, Fe(III) and DOM with dissolved organic carbon concentrations not higher than 3 mg L(-1). Phenol, 1,4-dihydroxylbenzene and 1,4-benzoquinone were identified as intermediate products of photodegradation of nonylphenol, through an HPLC method. In addition, the disappearance of the estrogenic activity of nonylphenol during irradiation using YES test was investigated. Based upon the YES test results, there was a strong decrease of estrogenic activity of nonylphenol after 80 h irradiation in the presence of hydrogen peroxide.

Bicarbonates↗

PubMed2005

Effect of sewage sludge or compost on the sorption and distribution of copper and cadmium in soil.

The application of biosolids such as sewage sludge is a concern, because of the potential release of toxic metals after decomposition of the organic matter. The effect of application of sewage sludge (Sw) and compost (C) to the soil (S) on the Cu and Cd sorption, distribution and the quality of the dissolved organic matter (DOM) in the soil, was investigated under controlled conditions. Visible spectrophotometry, infrared spectroscopy, sorption isotherms (simple and competitive sorption systems), and sequential extraction methods were used. The E4/E6 (lambda at 465 and 665 nm) ratio and the infrared spectra (IR) of DOM showed an aromatic behaviour in compost-soil (C-S); in contrast sewage sludge-soil (Sw-S) showed an aliphatic behaviour. Application of either Sw or C increased the Cu sorption capacity of soil. The Cd sorption decreased only in soil with a competitive metal system. The availability of Cu was low due to its occurrence in the acid soluble fraction (F3). The Cu concentration varied in accordance with the amounts of Cu added. The highest Cd concentration was found in the exchangeable fraction (F2). The Sw and C applications did not increase the Cd availability in the soil.

Adsorption↗

PubMed2003

Treatability of organic fractions derived from secondary effluent by reverse osmosis membrane.

Dissolved organic matters (DOMs) from two batches of secondary effluent collected from a local water reclamation plant were fractionated using column chromatographic method with non-ionic resins XAD-8, AG MP-50 and IRA-96. Seven isolated fractions were obtained from the fractionation study and these fractions were quantified using DOC, UV(254) and SUVA values. The fractionation study revealed that the secondary effluent samples comprised about 47.3-60.6% of hydrophobic and 39.4-52.7% of hydrophilic solutes. The treatability of each isolated fraction was investigated by subjecting each fraction to reverse osmosis (RO) treatment individually. It was noted that RO process could achieve high DOC rejections for acid and neutral fractions (ranging from 80% to 98% removal) probably due to the negative charge of RO membrane. The results obtained also indicated that hydrophobicity of DOMs is significant in determining treatability of organic species by RO process. The performance of RO in terms of DOC rejection of un-fractionated secondary effluent was also investigated to assess possible effects of interactions among organic fractions on their treatability by RO process. It was noted that DOC rejection associated with the un-fractionated secondary effluent was generally higher (ranging from 2% to 45%) than the corresponding rejection obtained from each individual fraction isolated from the secondary effluent. This finding suggested there is a beneficial interaction among the fractions that in turn has contributed towards a better overall DOC rejection performance by RO treatment.

Chromatography↗

PubMed2004

(Un)certainty of overall binding constants of Al with dissolved organic matter determined by the Scatchard approach.

One of the best approaches to date to obtain overall binding constants (Ko) for Al and dissolved organic matter (DOM) from acidic soil solutions is to collect 'free' Al data with diffusive gradients in thin films (DGT) and to infer the Ko values by fitting a continuous distribution model based on Scatchard plots. Although there is clear established literature demonstrating the usefulness of the Scatchard approach, relatively little attention has been given to a realistic assessment of the uncertainties associated with the final fitted Ko values. In this study we present an uncertainty analysis of the fitted Ko values using a synthetic dataset with different levels of random noise and a real data set using DGT data from an acidic soil solution. The parameters in the continuous distribution model and their corresponding upper and lower 95% uncertainty bounds were determined using the Shuffled Complex Evolution Metropolis (SCEM) algorithm. Although reasonable fits of the distribution model to the experimental data were obtained in all cases, an appreciable uncertainty in the resulting Ko values was found due to three main reasons. Firstly, obtaining 'free' Al data even with the DGT method is relatively difficult, leading to uncertainty in the data. Secondly, before Scatchard plots can be constructed, the maximum binding capacity (MBC) must be estimated. Any uncertainty in this MBC propagates into uncertainty associated with the final plots. Thirdly, as the final fitted Ko values are largely based on extrapolation, a small uncertainty in the fit of the binding data results in an appreciable uncertainty in the obtained Ko. Therefore, while trends in Ko for Al and DOM could easily be discerned and compared, the uncertainty in the Ko values hinders the application in quantitative speciation calculation. More comprehensive speciation models that avoid the use of Ko seem to fit better for this purpose.

Aluminum↗

PubMed2001

Photodegradation study of the antifouling booster biocide dichlofluanid in aqueous media by gas chromatographic techniques.

The aquatic photochemical behavior of the biocide dichlofluanid has been studied under natural sunlight conditions as well as under artificial solar irradiation in different types of natural waters (sea, river and lake water) as well as in distilled water. In order to examine the effect of dissolved organic matter (DOM), the photodegradation of the tested biocide was investigated also in the presence of various concentrations of humic and fulvic acids. It was found that the photodegradation proceeds via first-order reaction in all cases and that the presence of various concentrations of DOM inhibits the photolysis reaction. Kinetic experiments are monitored with GC-ECD with half-lives varied between 8 and 83 h. The major photodecomposition products identified by GC-MS were dichlorofluoromethane, aniline, and DMSA. Based on this byproduct identification a possible degradation pathway is proposed for the photolysis of dichlofluanid in aqueous media.

Aniline Compounds↗

PubMed1998

Carotid body dopaminergic mechanisms are functional after acclimatization to hypoxia in goats.

Ventilatory acclimatization to sustained hypoxia (VASH) is the time-dependent increase in ventilation that occurs during prolonged exposure to hypoxia. We tested the hypothesis that carotid body (CB) dopaminergic mechanisms are down-regulated during VASH, which would allow CB afferent discharge and ventilation to increase beyond the initial response to hypoxia. Domperidone (DOM; 1.0 mg.kg-1) was administered intravenously to block CB dopamine (DA) receptors after VASH was complete in awake goats. DOM caused a significant augmentation of the ventilatory response to hypoxia in acclimatized goats, failing to support the hypothesis. We conclude that inhibitory CB dopaminergic function is not significantly reduced following prolonged hypoxia, and that down-regulation of CB dopaminergic mechanisms may not be involved in VASH in the goat.

Acclimatization↗

PubMed2001

Dissolved organic carbon losses from grazed grasslands under different management regimes.

Dissolved organic matter (DOM) is fundamental to many biogeochemical processes in soils and natural waters. Despite the large number of studies reporting on DOM losses from forest soils and in surface waters there is little published data on exports from managed grasslands. The objective of our study was to determine the extent of short-term exports of dissolved organic carbon (DOC) from managed grazed grasslands and to evaluate the influence of fertilizer management and drainage regime. DOC discharged from grazed grassland plots, with a range of management strategies. was determined over 2 months. Total export varied from 42 to 118 kgCha(-1), and was greater from some plots than literature estimates for annual losses from all catchment types. There was a significant (P = 0.048) positive correlation between DOC export and rates of nitrogen application for treatments with no artificial drainage. Increased dry matter production arising from increased fertilizer-N inputs is suggested as an important factor in this relationship. DOC export was significantly (P = 0.032) reduced by artificial drainage and adsorption of DOC to soil surfaces and the restriction of decomposition due to waterlogging are suggested as two possible explanations.

Agriculture↗

PubMed1999

Differentiating with fluorescence spectroscopy the sources of dissolved organic matter in soils subjected to drying

The relative fluorescence, normalised on dissolved organic carbon (DOC), and a humification index, based on the location of the fluorescence emission spectra, were used to investigate the possible sources of the increase in dissolved organic matter (DOM) when a soil is dried. From these 2 parameters it could be seen that air drying resulted in a minor increase of more humified material in DOM while the effect of oven drying was mainly due to cell lysis.

Journal Article↗

PubMed1999

Environmental fate of amitrole: influence of dissolved organic matter

In this study the environmental fate of amitrole in terrestrial and aquatic model ecosystems was investigated. Under aerobic conditions mineralization of amitrole is the main degradation pathway. The experiments revealed that the leaching behaviour is low in the presence or the absence of dissolved organic matter (DOM) despite the high water solubility due to a strong binding of amitrole to soil constituents. Under anaerobic conditions the addition of DOM increases the transport of amitrole in soil columns. The tests with water/sediment model ecosystems showed that the mineralization of amitrole is lower in comparison to aerobic soil experiments. Up to 80.6% of the applied 14C-labelled amitrole transfer into the sediment and about 1/3 of this amount formed bound residues, which are not extractable.

Journal Article↗

PubMed2000

A comparative characterization of dissolved organic matter by means of original aqueous samples and isolated humic substances.

The aim of our study is to test the use of less time-consuming spectroscopic methods applied on original water samples in order to obtain information about DOM composition without any sample preparation. These results were directly compared with results from a conventional isolation and characterization procedure of dissolved humic substances (fulvic acids--FA) isolated from the same water sample. FAs were characterized by UV-, fluorescence-, FTIR spectroscopy and elemental composition. UV absorbance and fluorescence behavior of FAs and original water samples follow the same pattern. A lower UV absorbance and a lower humification index (derived from the synchronous fluorescence spectra) of about 15% is typical for water samples compared to the FAs. We computed linear relationships between properties of the original water sample (UV-, synchronous fluorescence spectra) and the isolated FA (IR absorption, C/N ratio). The application of synchronous fluorescence and UV spectroscopy of aqueous samples has been proved to result in similar information about DOM composition as the characterization of isolated humic substances concerning the content of aromatic structures and the degree of humification.

Adsorption↗

PubMed2000

Sorption of phenols to dissolved organic matter investigated by solid phase microextraction.

The sorption of phenol and different halogenated phenols to natural organic matter of a brown water lake (HO14), of a compost extract, of Aldrich humic acid (Aldrich-HA), and to the protein bovine serum albumin (BSA) was investigated using solid phase microextraction (SPME). The limit of determination for the SPME analysis was < 15 microg/l for all phenols investigated. The extraction coefficients K(F) were calculated according to a first-order extraction kinetics. In general, the extraction equilibrium was established faster due to the presence of dissolved organic matter (DOM). The highest sorption capacity of phenols was observed for BSA with log K(OC) values in the range between 2 and 6. For the compost extract and HO14 only a small sorption of the investigated phenols was determined. On the other hand, Aldrich humic acid showed a reasonable sorption of phenols with log K(OC) values between 2 and 3. The sorption to DOM decreased when the pH of the solution was increased.

Adsorption↗

PubMed2003

Solubility of metals in an anoxic sediment during prolonged aeration.

This work was conducted to study the evolution of the solubility of selected metals during the aeration of an anoxic sediment. Batch experiments were carried out for 76 days with a metal-polluted dredged sediment. The pH, Eh and concentration of Al, Cu, Fe, Hg, Pb and Zn were periodically recorded. Results showed that during the early stages of aeration, the solubility of metals increased rapidly but was then followed by fast re-adsorption. As a consequence, after 14 days most of the metals excepted Cu and Zn were present at low or undetectable concentrations in solution. Re-adsorption of Zn was observed to be much slower during the first two weeks, whereas solubilisation of Cu increased gradually during months after land disposal. According to speciation calculations, Cu solubilisation was in part due to complexation in solution by carbonates. In the case of Hg, although complexation by dissolved organic matter (DOM) could be expected, re-adsorption was the dominant process. However, more knowledge about the behaviour of the DOM present in anoxic sediments is needed in order to make more quantitative statements about the mobility of heavy metals contained in dredged material.

Adsorption↗

PubMed2002

5-HT2A receptor-stimulated phosphoinositide hydrolysis in the stimulus effects of hallucinogens.

The role of 5-HT2A-mediated stimulation of phosphoinositide hydrolysis in the discriminative effects of hallucinogens was investigated in PC12 cells stably expressing the rat 5-HT2A receptor (PC12-5-HT2A cells). The hallucinogenic compounds, D-lysergic acid diethylamide (LSD), (-)2,5-dimethoxy-4-methylamphetamine (DOM), psilocybin, N,N-dimethyltryptamine (DMT), 5-methoxy-N,N-dimethyltryptamine (MDMT) and N,N-diethyltryptamine (DET), all caused a concentration-dependent increase in the generation of [3H]inositol phosphates. The nonhallucinogenic compounds, 6-fluoro-N,N-diethyltryptamine (6-F-DET), lisuride and quipazine, also displayed significant efficacy in stimulating phosphoinositide hydrolysis, while 2-bromo-lysergic acid diethylamide (BOL), which is not a hallucinogen, did not alter inositol phosphate generation. The beta-carbolines, harmaline and harmane, also did not alter phosphoinositide hydrolysis. Comparison of these results with previous drug discrimination studies indicated the apparent lack of correlation between the degree of substitution in LSD- and DOM-trained animals and efficacy in stimulating phosphoinositide hydrolysis. The present study indicates that 5-HT2A-mediated stimulation of phosphoinositide hydrolysis does not appear to be the sole critical signaling mechanism involved in the discriminative effects of hallucinogens.

Animals↗

PubMedDate not supplied

Initial characterization of PMMA as a discriminative stimulus.

The phenylisopropylamine PMMA or N-methyl-1-(4-methoxyphenyl)-2-aminopropane, a structural hybrid of paramethoxyamphetamine (PMA) and methamphetamine, has been previously shown to unexpectedly lack amphetamine-like or hallucinogen-like stimulus properties in animals. For example, in tests of stimulus generalization, neither a (+)amphetamine stimulus nor a DOM stimulus generalized to PMMA. It has also been shown, however, that stimulus generalization does occur in animals trained to discriminate the designer drug MDMA ("Ecstasy" or N-methyl-1-(3,4-methylenedioxyphenyl)-2-aminopropane) from vehicle. In order to further characterize this unique agent, we trained a group of six Sprague-Dawley rats to discriminate 1.25 mg/kg of PMMA (ED50 = 0.44 mg/kg) from saline vehicle. The PMMA stimulus failed to generalize to the phenylisopropylamine stimulant (+)amphetamine, or to the phenylisopropylamine hallucinogen DOM. Stimulus generalization occurred to (+/-)MDMA (ED50 = 1.32 mg/kg) and S(+)MDMA (ED50 = 0.48 mg/kg). Partial generalization occurred with R(+)MDMA, PMA, 3.4-DMA, and fenfluramine. The PMMA stimulus also generalized to the alpha-ethyl homolog of PMMA (EH/PMMA, ED50 = 1.29 mg/kg). Taken together, the results of these studies suggest that PMMA is an MDMA-like agent that lacks the amphetamine-like stimulant character of MDMA. These findings support our previous suggestion that PMMA be considered the structural parent of the MDMA-like family of designer drugs.

Animals↗

PubMed2000

Protection by two complexing agents, thiosulphate and dissolved organic matter, against the physiological effects of silver nitrate to rainbow trout (Oncorhynchus mykiss) in ion-poor water.

Adult rainbow trout (Oncorhynchus mykiss) were exposed in ion-poor water ( approximately 50 microM Ca) to silver added as AgNO(3) or to AgNO(3) plus either thiosulphate (Na(2)S(2)O(3)) or dissolved organic matter (DOM). The effects of these exposures were assessed through repetitive blood sampling over 4 days. Trout exposed to 0.1 microM AgNO(3) alone accumulated large amounts of Ag on their gills and in their plasma, showed progressive losses of plasma Na and Cl, and had elevated concentrations of plasma glucose. In one set of exposures trout exposed to AgNO(3) alone also had increased cough rates, slightly higher ventilation rates, somewhat lower arterial oxygen tensions, and increased blood lactate concentrations. In contrast, trout exposed to 0.1 microM AgNO(3) plus 5 microM thiosulphate or 35 mg C l(-1) DOM accumulated less Ag on their gills and in their plasma, and showed no adverse ionoregulatory or respiratory effects due to Ag. These results demonstrate ionoregulatory and sometimes respiratory effects in fish exposed to ionic Ag(+) in ion-poor water, depending on water chemistry, and demonstrate the protective effects of synthetic and natural complexing agents through a reduction in the amount of ionic Ag(+) available to bind at the gills.

Animals↗

PubMed1982

Stimulatory control of prolactin by dopamine.

1. In addition to evidence that dopamine (DA) inhibits prolactin (PRL) via the tuberinfundibular system, there is also evidence for excitatory effects of DA via that system as well as evidence for regulation by DA sites lying behind the blood brain barrier. 2. Apomorphine (APO) was given to rats pretreated with either a peripheral (domperidone, DOM) or a central (haloperidol, HAL) DA blocker and prolactin responses examined. 3. Both DOM and HAL caused prolactin elevation. 4. Further elevation of prolactin was produced by APO in HAL treated animals, indicating an excitatory dopamine effect on prolactin.

Animals↗

PubMed2002

An experimental investigation of the relation between catastrophizing and activity intolerance.

The present study examined the value of a measure of catastrophizing as a predictor of activity intolerance in response to delayed onset muscle soreness (DOMS). A sample of 50 (17 men, 33 women) sedentary undergraduates participated in an exercise protocol designed to induce muscle soreness and were asked to return 2 days later to perform the same physical maneuvers. Participants performed five strength exercises that emphasized the eccentric component of the muscle contraction in order to induce DOMS. Dependent variables of interest were the proportion reduction in total weight lifted, and the number of repetitions. Analyses revealed that catastrophizing, assessed prior to the first exercise bout, was significantly correlated with negative mood, pain and with reduction in weight lifted. Regression analyses revealed that catastrophizing predicted reductions in weight lifted even after controlling for pain and negative mood. These findings extend previous research in demonstrating that catastrophizing is associated with objective indices of activity intolerance associated with pain. Implications of these findings for understanding pain-related disability are addressed.

Adolescent↗

PubMedDate not supplied

Low doses of non-NMDA glutamate receptor agonists alter neurobehavioural development in the rat.

While it is known that glutamate is critical to CNS development and function, less is known about the role of kainate receptors, a subclass of ionotropic glutamate receptors, during ontogeny. This is especially true with respect to the emergence and expression of behaviour. It is also known that the neonatal CNS differs from that of adults with respect to excitatory amino acid (EAA) toxicity. Our aim was to determine the effects of early low-dose stimulation of kainate receptors on physical and behavioural development in the rat. Saline, one of two subtoxic doses of domoic acid (DOM) (5 and 20 microg/kg), or in a parallel study, saline, or one of two pharmacologically equivalent doses of kainic acid (KA) (25 and 100 microg/kg), were systemically administered once daily from postnatal days (PNDs) 8-14. While DOM or KA had no effect on typical measures of toxicity such as weight gain, acoustic startle, ultrasonic vocalizations (UVs), or maternal retrieval, these doses were shown to be physiologically relevant, producing particular group differences in eye opening, conditioned place preference, and activity levels. We conclude that administration of very low doses of selective kainate receptor agonists during the second postnatal week produces changes in neurobehavioural development in the rat.

Aging↗