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PubMedDate not supplied

Contribution of stack gases and solid process wastes to the organic pollutant output of thermal waste treatment plants.

Within the scope of fundamental investigations as well as individual research projects (W. Knorr, B. Hentschel, C. Marb. S. Schädel, M. Swerev, O. Vierle, J.-P. Lay, 1999. Rückstände aus der Müllverbrennung-Chancen für eine stoffliche Verwertung von Aschen und Schlacken. Initiativen zum Umweltschutz, 13 ed., Deutsche Bundesstiftung Ulmwelt, Erich Schmidt, Berlin), the Bavarian State Office for Environmental Protection performs emission measurements at thermal waste treatment plants to optimize operation, to accompany and support development of new technologies, and to study the effect of this kind of waste treatment technology on the environment. Based on recent studies (October 1995-July 1999) at six municipal solid waste incinerators (MSWI) in Bavaria all emission streams (solid and gas) are characterized with respect to organic pollutant contents and compared to the emissions of waste pyrolysis. The significant ranges of pollutant concentration as well as the specific congener patterns observed are similar for all MSWI, regardless of differences in technical design and waste input, but differ markedly from those of the pyrolysis products. The overall approach, including the sampling of all output streams and the determination of mass streams and volume flow rates, allows the calculation of the total output of different organic pollutants for waste incineration plants aand to estimate the relative contribution of each of the emission streams to the total pollutant load. Removal efficiencies are also calculated for the air pollution control (APC) systems of the different MSWI plants.

Air Movements↗
PubMed2002

Correction for water vapor in the measurement of atmospheric trace gases.

The presence of water vapor in a sample of air reduces the concentration of a trace gas measured from the sample. We present a methodology to correct for this effect for those cases when the concentration of the trace gas has already been measured from a wet sample. The conversion or correction factor that takes the wet mole fraction to a dry mole fraction is determined by the mixing ratio of water vapor inside the sampling canister. For those samples where the water vapor is saturated inside the canister, the water vapor mixing ratio is largely determined by laboratory conditions; for the unsaturated samples, the mixing ratio is determined by station conditions. If the meteorology at the sampling station is known, the equations presented here can be used directly to calculate the appropriate correction factor. For convenience, we use climatological data to derive average monthly correction factors for seven common global sampling sites: Barrow, AK, US (71 degrees N, 157degrees W); Cape Meares, OR, US (45 degrees N, 124 degrees W); Mauna Loa, HI, US (19 degrees N, 155 degrees W); Ragged Point, Barbados (13 degrees N, 59 degrees W); American Samoa (14 degrees S, 171 degrees W); Cape Grim, Tasmania, Australia (41 degrees S, 145 degrees E); South Pole (90 degrees S). These factors adjust wet mole fractions upwards within a range of 0.002% for the South Pole to over 0.8% for saturated sites. We apply the correction factors to wet nitrous oxide (N2O) mole fractions. The corrected data are more consistent with our understanding of N2O sources.

Air Pollutants↗
PubMed1997

The urinary excretion of solvents and gases for the biological monitoring of occupational exposure: a review.

'In the field' application of the measurement of urinary excretion of unmodified solvent for the biological monitoring of exposed workers has been investigated in many recent papers. The results obtained for several solvents are reviewed. The values of correlation coefficients (r) and regression lines obtained for benzene, toluene, xylene, styrene, n-hexane, cyclohexane, 2- and 3-methylpentane, methyl chloride, tetrachloroethylene, carbon tetrachloride, methyl chloroform, p-dichlorobenzene, nitrous oxide, halothane, isoflurane, enflurane, acetone, methyl ethyl ketone and methyl isobutyl ketone are presented. The correlations observed were generally good: r values range from 0.50-0.97, and the majority are between 0.84 and 0.90. The regression lines reported for the same solvent in different studies present some variability: this is possibly due to an inadequate control of factors influencing the relationship between external dose and absorption, such as differences in body burden, work load, individual characteristics, etc. These factors are discussed. As a whole, results reported in the literature show that measuring of urinary excretion of unmodified solvents provides a highly sensitive and specific exposure index, and can also be applied for the biological monitoring of occupational exposure to low levels of solvents or to solvent mixtures. Nevertheless, for an adequate assessment of biological limit values, further studies evaluating the reproducibility of regression lines are needed, given that the aspects influencing the correlation between external dose and urinary excretion are fully controlled. Another crucial aspect is the correlation with early effects: even though this has yet to be evaluated for several solvents, for others such as styrene and perchloroethylene a good correlation was obtained, further supporting the usefulness of the measurement of urinary excretion of solvent for the biological monitoring of occupational exposure.

Absorption↗
PubMed1999

Effect of filling gases on the backscatter from contrast microbubbles: theory and in vivo measurements.

Two surfactant-based contrast agents, ST44 and ST68, were produced according to US Patent # 5,352,436 and filled with either air, C4F10 (perfluorobutane) or SF6 (sulfur hexaflouride). Ten rabbits received i.v. injections of each agent/gas combination with 5 repetitions of each dose (range: 0.005-0.13 mL/kg). A custom-made 10-MHz cuff transducer was placed around the surgically exposed distal aorta and audio Doppler signals were acquired in vivo. Quantitative in vivo dose responses were calculated off-line using spectral power analysis and compared to a theoretical model of microbubble dissolution and enhancement. For qualitative comparisons, 10 rabbits were imaged pre- and postcontrast administration (dose: 0.1 mL/kg) in gray-scale and colour. All agent/gas combinations produced marked Doppler enhancement with air bubbles enhancing least of all (p < 0.0001) and ST68-SF6 best of all (maximum: 27.6 +/- 2.04 dB; p < 0.012). There were no significant differences between other agent/gas combinations (0.30 < p < 0.70). Theoretical enhancement was within 1 order of magnitude of the experimental observations (i.e., deviations of up to 10 dB). The duration of contrast enhancement was 1-2 min for air-filled bubbles, 3-5 min for SF6-filled bubbles and more than 7 min for C4F10-filled bubbles. In conclusion, ST68-SF6 microbubbles produced most in vivo enhancement of the agent/gas combinations studied. Theory matched the measurements within an order of magnitude.

Animals↗
PubMed2001

Removal of styrene vapor from waste gases by a trickle-bed air biofilter.

The trickle-bed air biofilter (TBAB) performance for the removal of high-strength styrene was evaluated under different gas flow rates and influent concentrations. Under pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of styrene loading. More than 90 and 80% removal efficiencies were achieved for influent styrene loadings below 32 and 55g/m(3)/h, respectively. The TBAB appears to be an effective treatment process for controlling high-strength styrene emission under low-to-medium loading conditions, and the effectiveness could be maintained over 140 days of laboratory operation.

Air Movements↗
PubMed2002

In-source H/D exchange and ion-molecule reactions using matrix assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry with pulsed collision and reaction gases.

Controlled in-source ion-molecule reactions are performed for the first time in an external matrix assisted laser desorption ionization (MALDI) source of a Fourier transform ion cyclotron resonance mass spectrometer. The MALDI source with a hexapole ion guide that was originally designed to incorporate pulsed gas to collisionally cool ions (Baykut, G.; Jertz, R.; Witt, M. Rapid Commun. Mass Spectrom. 2000, 14, 1238-1247) has been modified to allow the study of in-source ion-molecule reactions. Upon laser desorption, a reaction gas was introduced through a second inlet and allowed to interact with the MALDI-generated ions trapped in the hexapole ion guide. Performing ion-molecule reactions in the high pressure range of the ion source prior to analysis in the ion cyclotron resonance (ICR) cell allows to maintain the ultra high vacuum in the cell which is crucial for high mass resolution measurements. In addition, due to the reaction gas pressure in the hexapole product ion formation is much faster than would be otherwise possible in the ICR cell. H/D exchange reactions with different peptides are investigated, as are proton-bound complex formations. A typical experimental sequence would be ion accumulation in the hexapole ion guide from multiple laser shots, addition of cooling gas during ion formation, addition of reaction gas, varied time delays for the ion-molecule reactions, and transmission of the product ions into the ICR cell for mass analysis. In this MALDI source H/D exchange reactions for different protonated peptides are investigated, as well as proton-bound complex formations with the reaction gas triethylamine. Amino acid sequence, structural flexibility and folding state of the peptides can be seen to play a part in the reactivity of such ions.

Cyclotrons↗
PubMedDate not supplied

A new approach to evaluate toxicity of gases on mobile cells in culture.

A novel technique is described that measures the degree of toxicity of short-term exposure to gaseous pollutants or other chemical compounds on cultured cells, in 30 min. This technique, based on the study of the mobility properties of activated macrophages, consists of an image analysis procedure incorporating a specific exposure chamber (EC). The EC, which is developed from commercial culture flasks (50 ml, 25 cm(2) of culture surface), was first used to maintain cells in culture conditions, overnight, prior to the assay. In order to measure toxicity, it was then connected to the gaseous pollutant or chemical source. After exposing the culture medium and cells to the gas stream for 10 min, fMLP, a chemotactic factor, was added and the mobility of the macrophages measured by superimposing sequential analogue images captured by a CCD camera that were digitised and analysed using a software developed for this purpose. For example, the effect of ozone on macrophage-like cell (THP-1) was investigated. After exposure to 0.1 and 0.5 ppm, cells lost, respectively 79% and 90% of their mobility, compared to the control sample.

Atmosphere Exposure Chambers↗
PubMed1998

Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica.

Measurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (+/- 0.37) and Ar was 3.8 (+/- 1.1). The ratios of N2/Ar (20.3 +/- 13.8), and O2/Ar (22.5 +/- 4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80-100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 micrograms l-1) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O2, N2, and Ar at levels similar to levels found in Lake Hoare.

Antarctic Regions↗
PubMed1992

Steric factors affecting the discrimination of isomeric and structurally related olefin gases and vapors with a reagent-coated surface acoustic wave sensor.

An investigation of steric factors affecting the olefin-olefin selectivity of a surface acoustic wave (SAW) sensor coated with reagents of the general formula trans-PtCl2(ethylene)-(substituted-pyridine) is described. Detection is based on the mass increase accompanying replacement of ethylene by other gas-phase olefins to form the corresponding olefin-substituted products. Selectivity depends on the relative reaction rates of the different olefins. Within series of structurally similar butenes, acrylates, and aromatic olefins, unusually high selectivity is observed for the less hindered olefins and complete discrimination of isomers is achieved in certain cases. Replacing pyridine by 2-methylpyridine and 2,6-dimethylpyridine in the reagent complex progressively reduces the sensor response. Sensitivities increase with increasing temperature and limits of detection ranging from about 2 to 70 micrograms/L are achieved with modest heating (30-40 degrees C) using a 30-MHz SAW oscillator. Initial results with a 52-MHz sensor shows a 3.4-fold increase in sensitivity compared to the 30-MHz sensor in rough agreement with theory.

Acoustics↗