L. Van Vaeck

The gas-particle distribution of organic aerosol constituents: measurement of the volatilisation artefact in Hi-Vol cascade impactor sampling

Abstract In order to determine quantitatively the volatilisation losses of organic aerosol constituents upon prolonged Hi-Vol sampling, an Integrated Gas Phase-Aerosol Sampling System was developed. The volatilisation artefact being measured, the actual distribution of the volatile organic compounds between the gas and the particulate phase as it exists in the atmosphere could be studied. Sampling was performed in a suburban and in a rural site during the four seasons. Determinations of the major organic aerosol components, including a series of unbranched aliphatic hydrocarbons, carboxylic acids and polycyclic aromatic hydrocarbons (PAH), were carried out by mass fragmentography. The volatilisation artefact is found to be important for the compounds with intermediate vapor pressure, e.g. n- alkanes from eicosane to tetracosane, acids from lauric to stearic acid, PAH from phenanthrene /anthracene to benz(a)anthracene/chrysene. The obvious influence of parameters such as the sampled volume and the average ambient air temperature is clearly reflected in the obtained data. The implications of these results with respect to the optimisation of Hi-Vol sampling procedures and to the use of the profile concept for emission source characterisation are discussed, as well as the problems, involved with the correction of particle size distribution data for aerosol constituents subjected to the volatilisation artefact. Generally, the particle size distribution profiles tend to widen as a consequence of the preferential depletion of the sub-μm fraction. The measured gas-particle distribution in the atmosphere reflects some important physico-chemical processes in aerosol formation and ageing. The gas-particle conversion of a young condensation aerosol in the suburb is compared to that of the aged, diluted one at the rural station. Aerodynamic elution of the most volatile n- alkanes is observed at the latter site.

Cascade impactor measurements of the size distribution of the major classes of organic pollutants in atmospheric particulate matter

Abstract Airborne particulate matter from a suburban area was fractionated in a 6-stage high volume cascade impactor and analysed for about 60 organic pollutants by programmed multiple ion detection gas chromatography-mass spectrometry. The distribution, as a function of particle size, has been measured for the aliphatic hydrocarbons, carboxylic acids, polynuclcar aromatic hydrocarbons (PAH) as well as some aza-heterocyclic polyaromatics. The observed distribution patterns are very similar. Most aliphatic hydrocarbons (85–90°) are found on particles below 3μm. The carboxylic acids are found for 90–95% below 3 μm. The PAH distribution is strongly subjected to seasonal variations : 95–98% below 3 μm and 70–80% below 1μm in winter. For the PAH eight different, but closely related types of distributions were measured. In winter, the distributions shift toward the smaller particles. Indications for artefacts produced by volatilisation are advanced : the lower PAH show a flatter distribution in the smaller size range. Also, the alternating concentration levels of even and uneven n -alkenes could be due to selective losses for the even alkenes, since there is a correlation with the molar heat of vaporisation of the homolog series.

Characteristic parameters of particle size distributions of primary organic constituents of ambient aerosols

and Meteorology for Roane County, Tennessee, During 1975”; Oak Ridge National Laboratory: Oak Ridge, TN, 1977. (17) Turner, W. A.; Spengler, J. D.; Dockery, D. W.; Colome, S. D. J . Air. Pollut. Control. Assoc. 1979,‘29 (7), 747-749. (18) Treitman, R. D.; Spengler, J. D.; Tosteson, T. D. “Quality Assurance Project Plan”; Research Triangle Institute, U.S. Environmental Protection Agency Research Triangle Park, NC, 1981. (19) Biddeson, D. L.; Eaton, W. C. “Performance and Systems Audit of the Respirable Particulate Exposure Study”; Research Triangle Institute, U.S. Environmental Protection Agency: Research Triangle Park, NC, 1981. (20) Eaton, W. C.; Arey, F. K.; McKee, J. L. “Systems Audit, 1982, Harvard School of Public Health Six-City Study”; Research Triangle Institute, U.S. Environmental Protection Agency: Research Triangle Park, NC, 1982. (21) Quackenboss, J. J.; Karanek, M. S.; Spengler, J. D.; Letz, R. E. Environ. Int. 1982,8, 249-258. (22) Ju, C.; Spengler, J. D. Environ. Sei. Technol. 1981, 15, 595-596. (23) Tosteson, T. D.; Spengler, J. D. Environmetrics ’81, Society for Industrial and Applied Mathematics, Alexandria, VA, 1981. (24) Spengler, J. D.; Dockery, D. W.; Turner, W. A.; Wolfson, J. M.; Ferris, B. G., Jr. Atmos. Environ. 1981, 15, 23-30. (25) Letz, R. L.; Ryan, P. B.; Spengler, J. D. Environ. Monit. Assess. 1984, 4 (4), 351-359. (26) Duan, N. Environ. Int. 1982, 8, 305-309. (27) Tosteson, T. D.; Spengler, J. D.; Weker, R. A. Environ. Int.

Conversion of polycyclic aromatic hydrocarbons on diesel particulate matter upon exposure to ppm levels of ozone

Diesel exhaust particlulate matter samples were collected from a dilution tunnel using a Hi-Vol cascade impactor. The fraction of the aerosol with aerodynamic diameter below 0.5 μm, retained on the glass fiber back-up filter, was exposed to a flow of ozonised particle free air for periods of 0.5–4 h (1.5 ppm of O3, flow rate about 40 m3 h−1). Both exposed and non-exposed reference niters were Soxhlet-extracted with benzene and methanol, and the polycyclic aromatic hydrocarbon fraction (PAH) was isolated by a liquid-liquid partition procedure described in the literature, using cyclohexane and dimethylformamid-water as solvents, modified for quantitative recovery of PAH. The conversion yields of PAH upon exposure to O3 were determined by single ion monitoring mass spectrometry using a fused silica capillary column for their separation. Significant conversion was observed for PAH from molecular weight 226 to 276. Approximate half lives are of the order of 0.5–1 h for most PAH measured. This high reactivity of PAH on a carbonaceous matrix is probably related to the large specific surface of soot particles as well as to their high adsorptive capacity for gaseous compounds. Lower molecular weight PAH up to chrysene also undergo important physical losses by volatilisation and the extent to which chemical transformations occurred could not be determined accurately. Different reactivities are observed for several isomeric pairs of PAH: benzo(a)pyrene is much faster converted than benzo(e)pyrene, benz(a)anthracene reacts faster than chrysene. The benzo-fluoranthenes are most resistant toward O3 attack. The implications of these results with respect to atmospheric degradation of PAH, as well as to the occurrence of artefactual conversion upon Hi-Vol sampling are discussed.

On the size distribution of polycyclic aromatic hydrocarbon containing particles from a coke oven emission source

Abstract Two samples of particulate matter from a coke oven emission source were collected with an Andersen cascade impactof to obtain size-graded fractions. Analysis of 12 major polycyclic aromatic hydrocarbons was performed for all stages, by means of a gas chromatograph-mass spectrometer used in the mass fragmentography mode. Results illustrate that over 90% of polycyclic aromatic hydro-carbons is found on the particles smaller than 3 μm, which means that most of these compounds are within the respiratory size range. Similar size distribution curves were obtained for both the lower and higher molecular weight compounds.

Distribution of calcium in a subset of chronic hibernating myocardium in man.

SummaryThe structural correlates of ‘chronic hibernating myocardium’ in man consist of myocardial cells which transformed from a functional state (rich in contractile material) to a surviving state (poor in contractile material, rich in glycogen). Since the calcium-handling organelles such as SR, sarcolemma and mitochondria underwent structural changes in cells so affected, the distribution of calcium was investigated in biopsies obtained from ‘hibernating’ areas. The material was processed for microscopic localization of total calcium (laser microprobe mass analysis, LAMMA) and of exchangeable calcium (phosphate-pyroantimonate precipitation method, PPA). Subcellular distribution of total calcium as assessed by LAMMA revealed that in the structurally affected cells the areas in which sarcomeres were replaced by glycogen contained significantly more calcium than all other areas probed such as mitochondria, remaining sarcomeres at the cell periphery and subcellular areas of normally structured cells. Calcium precipitate, obtained after PPA assessment, was localized at the sarcolemma but was virtually absent in the mitochondria of affected cells. The high calcium content in the myolytic areas of affected cells most probably belongs to a pool of bound calcium. The observations that calcium is retained at the sarcolemma and that mitochondria are devoid of precipitate favour the hypothesis that cells structurally affected as such are not ischaemic and are still able to regulate their calcium homeostasis.

Aerosol collection by cascade impaction and filtration: Influence of different sampling systems on the measured organic pollutant levels

Abstract A comparison is made between the analytical data obtained for the organic composition of airborne particulate matter collected with a high volume cascade impactor and a filtration sampler. The concentrations of individual organic pollutants are determined by gas chromatography—mass spectrometry. The total suspended particulate matter concentrations agree within 10% or better for the two samplers. The individual concentrations of pollutants agree in most cases within 20 to 30%. It is concluded that both sampling and analytical procedures give consistent results for organic compounds of low volatility. These are preferentially associated with the smaller particles ( μ m) whose collection efficiency is not affected by differences in upper cut-off diameter of the two samplers. Deviations in concentration levels beyond 20 to 30% occur for organic compounds of high volatility such as the lower molecular weight polyaromatics, the lower carboxylic acids and the aliphatics. Therefore, it is believed that volatilisation of compounds from the filter substrate may be an important source of errors in the measurement of organic pollutant levels in aerosols.

Microprobe speciation analysis of inorganic solids by Fourier transform laser mass spectrometry

Fourier transform (FT) laser microprobe mass spectrometry (LMMS) aims at the characterization of local constituents at the surface of solids. Signals from structural fragments specify the main building blocks of the analyte while adduct ions, consisting of one or two intact analyte molecules and a stable ion, allow specific identification of the molecule. A series of inorganic reference compounds including binary salts, oxides, and oxy salts was analyzed to assess the FT LMMS capabilities for the determination of the inorganic molecular composition. Compounds from different classes can be tentatively identified by deductive reasoning while those with the same elements in different stoichiometries require comparison with reference spectra.

Toxicological implications of the organic fraction of aerosols: a chemist's view

Abstract In the first part of this review, the analytical methodology used to determine the particle size distributions of organic pollutants in particulate matter is described. Several problems affecting the precision of this procedure are discussed: the calibration of commercial Hi-Vol cascade impactors, physical and chemical sampling artifacts, recovery of organics from particles, and analytical methods for quantitation. In combination with the ICRP model for the retention of particles in the human respiratory tract, deposited concentrations of organic pollutants can be calculated, which are of great toxicological significance. The application of this model to the polydisperse aerosol fractions collected by cascade impaction was validated using particle size distributions from the literature, which have been measured in very small particle size intervals. Results for suburban and rural aerosol samples are briefly discussed. Reliable estimates of the average daily intake (ADI) of organic pollutants by respiration will require the experimental determination of the absorption efficiency. As a first approximation for organic pollutants, the ADI can be set at 4 C ng, where C is the total concentration of the compound in the aerosol. The second part of this review is concerned with the chemical reactivity of organic aerosol constituents in the atmosphere as well as on sampling substrates. The use of the Ames Salmonella microbiological assay has shown significant direct mutagenic activity of the frameshift type in aerosol extracts from different sources, which cannot be attributed to known carcinogenic polycyclic aromatic hydrocarbons (PAH). Thus, it was realized that aerosol particles might contain secondary pollutants as the result of gas-particle interactions in emission stacks, plumes or during atmospheric transport. Laboratory experiments were performed to evaluate the chemical reactivity of PAH towards several gaseous pollutants (SO 2 , NO 2 , O 3 ) under simulated atmospheric conditions both on filter substrates and on PAH-enriched aerosol samples. The results were most encouraging: the carcinogen benzo[ a ]pyrene, for example, could be degraded rapidly by ozone to a series of polar compounds; the direct mutagenicity of the reaction mixture was found to be caused by the presence of a benzo[ a ]pyrene-epoxide, in small amounts. However, it is expected that the efficiency of chemical transformation of PAH in aerosols will largely depend on several factors: particle size and specific surface area will affect the conversion of PAH in a heterogeneous system; the close interaction between aerosol matrix and the adsorbed organics can induce a different chemical behaviour of PAH from that observed in model systems.

Microscopical speciation analysis with laser microprobe mass spectrometry and static secondary ion mass spectrometry

This paper presents a set of data which compares the potential and limitations of laser microprobe mass spectrometry (TOF-LMMS and FT-LMMS) and static secondary ion mass spectrometry (S-SIMS) for inorganic speciation at a microscopical level. In general LMMS yields prominent signals of adduct ions consisting of the intact molecule combined with a stable ion, which allows a direct identification of the analyte. S-SIMS also yields abundant diagnostic signals to specify the molecular composition. However, adduct ions are not always present, which means that the identification often relies on fingerprinting. Results further indicate that the potential and the application area of S-SIMS and FT-LMMS are complementary to one another.