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C Vandecasteele

Publications and source records attributed to C Vandecasteele.

At least 37 records · Page 2Linked to original sources
PubMed2002

Characterisation and treatment of roads covered with zinc ashes, muffle furnace fragments and lead slags from former non-ferrous metal industries in Belgium.

Zinc ashes, muffle furnace fragments and lead slags from non-ferrous industries were applied to pave roads in the North of Belgium. From an inventory it appeared that there are at least 490 km of such roads. In our survey the materials on these roads were characterised. The total metal concentration, the availability and the leaching as a function of time were determined. It appeared that these materials contain high concentrations of heavy metals, some of which are readily available. The high leaching of some metals makes them as such unsuitable as secondary construction material. Methods for the application of these materials for road construction were examined where the materials replaced part of the sand and gravel fraction in lean concrete and in bituminous mixtures, or where they replaced the sand in sand-cement mixtures, all these to be used for road foundations, cycle tracks, etc. When lead slags were applied in lean concrete, a material was obtained complying with the standards for secondary construction materials and with sufficient compressive strength for road foundations. When zinc ashes or muffle fragments were used to replace sand in sand-cement mixtures, again a suitable construction material was obtained. The other combinations tried out were rather unsuccessful, because of high metal leaching and/or poor compressive strength.

Belgium↗
PubMed2001

Flux decline during nanofiltration of organic components in aqueous solution.

Flux decline due to interaction of the membrane with the feed solution is a major drawback for the use of nanofiltration in environmental applications. This paper studies different mechanisms of flux decline for the nanofiltration of aqueous solutions containing organic compounds. The resistance model for flux decline is used: different mechanisms contribute through an increase of the resistance of the membrane against mass transport. The focus in this research is on pore blocking and adsorption inside the membrane pores. Osmotic pressure is also taken into account as it decreases the driving force. The nanofiltration membranes used were NF70 (Dow), UTC-20 and UTC-60 (Toray Ind.), and NTR 7450 (Nitto-Denko). Experiments with different organic components in aqueous solution showed that adsorption resulted in a strong decrease of the water flux. The results of the flux decline as a function of the concentration could well be fitted with the Freundlich equation for adsorption. The components that showed the largest effect had the highest polarity (permanent dipole moment or polarizability), which indicates that adsorption is favored by the polarity of the components in solution. Moreover, the molecules with a size similar to the pore size had a stronger effect on the water flux than other molecules. This can be explained by blocking of the pores by adsorbed compounds.

Adsorption↗
PubMed2001

Soil- and plant-based countermeasures to reduce 137Cs and 90Sr uptake by grasses in natural meadows: the REDUP project.

The effectiveness of a set of soil- and plant-based countermeasures to reduce 137Cs and 90Sr transfer to plants was tested in natural meadows in the area affected by Chernobyl fallout. Countermeasures comprised the use of agricultural practices (disking + ploughing, liming and NPK fertilisation), addition of soil amendments and reseeding with a selection of grass species. Disking + ploughing was the most effective treatment, whereas the K fertiliser doses applied were insufficient to produce a significant increase in K concentration in soil solution. The application of some agricultural practices was economically justifiable for scenarios with a high initial transfer, such as 137Cs-contaminated organic soils. The use of soil amendments did not lead to a further decrease in transfer. Laboratory experiments demonstrated that this was because of their low radionuclide sorption properties. Finally, experiments examining the effect of plant species on radionuclide transfer showed that both transfer and biomass can depend on the plant species, indicating that those with high radionuclide root uptake should be avoided when reseeding after ploughing.

Agriculture↗
PubMed2001

Evaluation of the use of a sequential extraction procedure for the characterization and treatment of metal containing solid waste.

Metal containing wastes like MSWI fly ashes and blast furnace sludge form a major environmental problem as they are polluted with heavy metals. The ash has to be landfilled or can be used as a construction material, but a pretreatment is in general necessary. Washing of the ashes with water in order to dissolve soluble salts or extracting the heavy metals with chemicals are possibilities. Blast furnace sludge contains large quantities of iron and carbon and could be recycled in the blast furnace, if the zinc content were not that high. Using a hydrometallurgical process the zinc can be removed from the sludge particles. In order to evaluate such treatment methods knowledge of the leaching behaviour of the studied material is very important. One of the factors influencing the leaching behaviour is the composition and mineralogy of the solids. A sequential extraction procedure, whereby the material is sequentially leached with different leaching solutions, can be used as an aid to characterize the material and to determine which chemical conditions are needed to obtain a sufficient extraction efficiency. To verify the accuracy of the sequential extraction procedure, a method is tested on MSWI fly ash and evaluated by comparing the results with those of leaching experiments whereby the final pH of the leaching solutions is varied over a wide range. Based upon this evaluation some suggestions for the use of the sequential extraction procedure are made and an adapted procedure is suggested, and applied to a blast furnace sludge.

Chemistry Techniques, Analytical↗
PubMed1999

Oxidation of arsenic bearing fly ash as pretreatment before solidification.

When a waste fly ash, containing large amounts of As(2)O(3), is solidified using cement and lime, the arsenic concentration in the leachate (extraction test DIN 38 414 S4) is determined by the solubility of CaHAsO(3) and can be lowered to a value of ca. 5 mg/l, in a saturated solution of Ca(OH)(2). One of the criteria for landfilling of hazardous waste is, however, that the arsenic concentration in the leachate must be lower than 1 mg/l. In this paper, it is shown that oxidation of the waste before solidification, whereby As(III) is oxidised to As(V) using H(2)O(2), lowers the leaching of arsenic, and other contaminants, from the solidified product. With the speciation program MINTEQA2, it is calculated that the solubility of As(V) in the presence of a pure Ca(3)(AsO(4))(2) precipitate is lower than the solubility of As(III) in the presence of a pure CaHAsO(3) precipitate. The arsenic concentration in the presence of both a Ca(OH)(2) and a Ca(3)(AsO(4))(2) precipitate can even be lowered to 0.47 mg/l (pH 12.5). The As concentration in the leachate of the extraction test on an oxidised S/S sample was indeed lowered to ca. 0.5 mg/l, which is a reduction by a factor of 10 compared to the concentration of ca. 5 mg/l, obtained in the leachate of the extraction test on a non-oxidised S/S sample. This is in very good agreement with the calculated value of 0.47 mg/l. Also, the pretreatment decreased the cumulative fraction of arsenic released over the entire test period of a semi-dynamic leach test by a factor of 7. At all times during the test, the As concentration did not exceed the norm of 1 mg/l.

Algorithms↗
PubMed1998

Dermal and respiratory sensitization to chromate in a cement floorer.

BACKGROUND: To report a well-documented case of both allergic contact dermatitis and occupational asthma due to chromate exposure in a 48-year-old floorer. METHODS AND RESULTS: A 48-year-old floorer, occupationally exposed to cement and with a documented chromate contact dermatitis, reported dyspnea and wheezing after work. These conditions were demonstrated by self-measured sequential peak expiratory flows. A first bronchial provocation (BPT) with potassium dichromate (K2Cr2O7) (0.3% nebulized for a total of 60 minutes) led to pronounced and sustained decreases in forced expiratory volume in 1 second (FEV1) and forced vital capacity, accompanied by pruritus, a decrease in arterial PO2, a slight rise in temperature, and peripheral blood leukocytosis. (This concentration of K2Cr2O7 is not recommended for BPT). Bronchoalveolar lavage performed 2 days later showed 18% eosinophils. Tow years later, a BPT with a lower dose of K2Cr2O7 (0.01% for the total of 31 min) led to an "earl late" reaction (FEV1 dropped by 195 compared with the initial FEV1 value), accompanied by pruritus. A BPT with dry cement, containing 12 ppm hexavalent chromium, was borderline (FEV1 dropped by 13%), and a similar result (FEV1 dropped by 14%) was obtained after smoking five cigarettes, laced with 10 mg of cement per cigarette. CONCLUSIONS: This report illustrates that a subject, with allergic contact dermatitis to chromates, may develop a respiratory allergic reaction to an airborne source of this metal. The main novelty of our report is that the smoking of cigarettes contaminated with cement may have been significant factor in the causation or elicitation of these reactions.

Asthma↗
PubMed1995

A sensitivity study of the SCK.CEN BIOSPHERE model for performance assessment of near-surface repositories.

At SCK.CEN a model has been developed on behalf of NIRAS/ONDRAF for the performance assessment of near-surface repositories, consisting of several submodels. This article deals with the submodels BIOSPHERE, describing the transfer and accumulation of the radionuclides in the biosphere and DOSE, calculating effective individual doses to the critical group. An extensive literature review was performed in order to determine best-estimate values and uncertainty ranges (probability density functions) of biosphere parameter values, specific to conditions that may prevail at potential disposal sites in Belgium. In this paper the BIOSPHERE and DOSE models are described and default and site-specific values (probability density functions where appropriate) of the parameters involved are indicated for the radionuclides 129I, 239Pu, and 94Nb. A combined uncertainty/sensitivity analysis based on the pdf of the site-specific parameter values has been carried out. Median values and 95% confidence intervals of the site-specific doses are indicated and most influential parameters to the uncertainty identified. Site-specific median dose values are also compared with generic doses.

Air Pollutants, Radioactive↗
PubMed1990

Determination of trace amounts of cadmium, lead, copper and zinc in natural waters by inductively coupled plasma atomic emission spectrometry with thermospray nebulisation, after enrichment on Chelex-100.

Enrichment on Chelex-100, followed by evaporation when necessary, was used for the pre-concentration of Cd, Pb, Cu and Zn from natural waters. The measurements were carried out with inductively coupled plasma atomic emission spectrometry using a thermospray nebulisation system to reach the required sensitivity. The detection limits corresponding to three times the standard deviation of the blank (in 1% v/v HNO3) after a 30-fold enrichment are 0.02 microgram l-1 for Cd, 0.33 microgram l-1 for Pb and 0.03 microgram l-1 for Cu and Zn. Matrix effects, which are fairly serious with thermospray nebulisation, were taken into account by using the standard additions method. Results obtained for several river water samples were compared with those found by analysis of the non-enriched sample with inductively coupled plasma mass spectrometry or graphite furnace atomic absorption spectrometry. In all instances the agreement was satisfactory.

Cadmium↗
PubMed1989

Determination of iron, cobalt, copper, zinc, rubidium, molybdenum, and cesium in human serum by inductively coupled plasma mass spectrometry.

A method was developed for the determination of seven trace elements (Fe, Co, Cu, Zn, Rb, Mo, and Cs) in human serum by inductively coupled plasma mass spectrometry (ICP-MS). Sample preparation was kept as limited as possible. As the only sample pretreatment serum samples were diluted with nitric acid and indium was added as an internal standard. The results for iron, cobalt, copper, and zinc were corrected for interferences from polyatomic ions by using a blank solution containing the same concentration of sodium, sulfur, chlorine, and calcium as human serum. For copper and zinc the corrections are small, whereas for iron and cobalt they are important. No interferences occur for the considered isotopes of rubidium, molybdenum, and cesium. In order to test the accuracy and precision of the analytical technique, a "second-generation biological reference material (human serum)" was analyzed. The results obtained by ICP-MS for the seven elements considered showed good agreement with the certified values.

Humans↗
PubMed1988

Element concentrations in the air of an indoor shooting range.

Elemental emissions during firing in a shooting range were measured for different types of ammunition. When using Hirtenberger bullets, lead, barium, antimony and to a lesser extent copper and arsenic were the primary metal pollutants. Stationary sampling at three locations in the range did not reveal large concentration gradients. Large concentration variations were observed by sampling before, during and after shooting. Lead and antimony concentrations peak at 5060 and 119 micrograms m-3, respectively. Soil elements such as aluminium, sodium and calcium are enriched during shooting, probably due to soil resuspension by the shooters and the bullets hitting the sand backstop. After shooting has ceased the concentrations fall to within pre-shooting levels within a couple of hours. Measurement of the aerodynamic particle size shows low mass median diameters for the elements emitted during firing and larger diameters for the soil-associated elements. The peak airborne concentrations measured by stationary sampling, and human exposure measured by a personal sampler carried by an instructor were compared with threshold limit values. During the shooting the TLV is significantly exceeded for lead.

Air↗
PubMed1987

Clinical comparison of 11C-ACPC (aminocyclopentane carboxylic acid) and 13N-ammonia as tumour tracers.

Positron emission tomography is a potential method for exploring the biochemical behaviour of tumours. In 28 patients with known neoplastic lesions a comparison was made between two agents which are known to be accumulated in malignant tumours, viz. 13N-ammonia and 11C-aminocyclopentane carboxylic acid (ACPC). Absolute concentration of both agents in various tumoural tissues and normal organs was calculated. As a rule a parallelism was found between the two tracers as to their accumulation in a given tumour, although the concentration was often higher for ACPC. In normal tissues the ACPC accumulation was either lower or at most equal to NH3 levels. As tumour tracer ACPC is superior to NH3 because of its higher absolute accumulation in many neoplastic lesions and its lower uptake in various non-tumorous tissues. ACPC concentration in tumours seems to be largely independent of blood flow.

Abdominal Neoplasms↗
PubMed1986

Microscale synthesis of nitrogen-13-labeled cisplatin.

A microscale synthesis of [13N]cisplatin (cis-dichlorodiammineplatinum(II), cis-DDP) from cyclotron-produced [13N]ammonia is presented. Temperature, reaction time, ratios, and concentration of reactants have been optimized for each step of the synthesis. Purification is performed by ion exchange chromatography. Radiochemical purity and optimization processes are controlled by high performance liquid chromatography and high performance thin layer chromatography--22 mCi [13N]cisplatin in 10 ml of solution is produced. The entire procedure takes approximately 15 min and the specific activity is approximately 300 mCi/mumole at EOB.

Ammonia↗
PubMed1985

Production and quality control of 15O2 and C15O2 for medical use.

The remotely controlled on-line production with a cyclotron of 15O2 and C15O2 for routine medical use is described. The radiochemical purities have been determined and compared with literature data. The impurities formed during irradiation can be removed with appropriate traps. The toxic gases ozone, nitrogen dioxide and carbon monoxide are formed in the target at concentration levels above the "Threshold Limit Value". Therefore a chemical quality control procedure has been developed. A copper oxide-iron oxide trap was found to improve the radiochemical and chemical purity of the C15O2.

Carbon Dioxide↗
PubMed1985

Fully automatic, microprocessor-controlled system for the production of 11CO2, 11CH3I and 11C-labeled radiopharmaceuticals.

An automated system for the production of 11C-labeled radiopharmaceuticals, using 11C-CH3I as a precursor, has been developed. The whole procedure, including irradiation, production of 11C-CH3I, synthesis of the labeled molecule and isolation of the final product is controlled by a microprocessor. Between 30 and 80 mCi of 5 different radiopharmaceuticals are produced routinely with this system.

Carbon Dioxide↗
PubMed1985

Kinetics of 13N-ammonia incorporation in human tumours.

After intravenous injection of 13N-labelled ammonia time-activity curves were obtained in a series of malignant neoplasms in man from serial cross-sectional scans through the tumour, using positron emission tomography. Low noise images with virtually no artefacts were obtained using a maximum likelihood reconstruction technique. Tracer concentration was expressed as a fraction of the injected dose ml-1 of tumour tissue. In a first group (eight observations) maximum activity [0.9 to 5.2 (mean: 3.3) X 10(-5) of administered dose ml-1 of tumour tissue] was attained approximately 1 to 3 min post injection. This peak was followed by a clearance phase with a half-time varying between 28.3 and 112 (mean: 73.1) min. In a second group (of six cases) after an initial rapid rise of the activity, no clearance was detectable during the time of observation, tracer concentration remaining in plateau or even continuing to rise slightly. Maximum activity in this group ranged from 1.1 to 5.3 (mean: 2.6) X 10(-5) of the administered dose ml-1 of tissue. So far no relation has been established between the height and/or shape of the 13NH3 time-activity curve and a particular tumour type.

Adult↗
PubMed1984

Enzymatic synthesis of C-11 formaldehyde: concise communication.

We present an enzymatic synthesis of C-11 formaldehyde from C-11 methanol, with immobilized alcohol oxidase and catalase: a rapid, simple procedure, with a high and reproducible yield. Carbon-11 methanol is oxidized to C-11 formaldehyde by passage over a column on which the enzymes alcohol oxidase and catalase are immobilized. The catalase increases reaction velocity by recycling the oxygen, and prevents destruction of the alcohol oxidase by eliminating the excess of hydrogen peroxide. The yield of the enzyme-catalyzed oxidation was 80-95%. A specific activity of 400-450 mCi/mumole was obtained at EOB + 20 min. Various immobilization techniques and the optimal reaction conditions of the immobilized enzymes are investigated.

Alcohol Oxidoreductases↗
PubMed1983

The production in high yield of N'-(4-[11C]methyl)-imipramine.

A method for the routine production in high yield of N'-(4-[11C]methyl)-imipramine is presented. The label is incorporated by reaction of C-11 methyl iodide (11CH3I) upon desipramine in dimethylsulfoxide. Quaternization of the tertiary amine by 11CH3I is minimized by using an excess of desipramine. The reaction proceeds at room temperature for 10 min and the product is isolated by means of high-performance liquid chromatography (HPLC). The entire production takes only 40 min and results in a radiochemical yield of 60%. About 60 mCi of labeled product are available for medical application; the specific activity, at the time of use, is 50 mCi/mumole. The product was characterized by chromatographic and spectrometric methods.

Carbon Radioisotopes↗