Speciation of elements in atmospheric particulate matter by XANES

The atmospheric particulate matter samples were collected in Shanghai, China. The X-ray absorption near-edge structure (XANES) spectra of Cr, Mn, Cu and Zn were measured. The XANES spectroscopy was used as a fingerprint to compare with that of reference materials to obtain speciation information. The oxidation state of these elements and main chemical components in the samples were described using the method. The results show that in our samples the oxidation state of Cr is trivalent, Mn mainly exists in the divalent state, Cu also exists in the divalent state, and Zn mainly exists in the zinc sulfate. For the XANES spectra of samples with different particle size and from different sampling site, we did not find their obvious differences. When we compared the XANES spectra of our samples with those of standard reference material SRM 1648, we found that they are similar in regards to the determined elements. The elemental concentrations in the samples were determined by proton induced X-ray emission (PIXE). The difference of elemental concentrations was observed in the different samples.     

Neutron activation analysis: Still a reference method for air particulate matter measurements

At ITN, PM10 and PM2.5 aerosols were collected on Nuclepore^® polycarbonate filters of 47 mm diameter, using Gent samplers at 15–17 l/min air flux. Filters were analyzed by INAA and PIXE. The availability of certified filters was very scarce, viz.: (1) fly ash embedded in a methyl cellulose 47 mm foil 10 µm thick, BCR CRM128, (2) particle-size reduced air particulate matter (APM) to simulate PM2.5 aerosol matter deposited on a 47 mm polycarbonate filter membrane, NIST SRM 2783. The high price and scarcity of APM standards did not permit their frequent use for analytical quality control. At ITN, to control the filter results' accuracy, the chemical elements potassium, iron and zinc, determined by both techniques, were systematically compared. After a few improvements introduced in INAA, this technique was now considered at ITN as the reference technique in air particulate measurements. Comparison of INAA to PIXE was discussed. Compared to previously reported situation it was concluded that the results were in better agreement for iron and zinc, and potassium values were still biased to the same extent as before.     

Investigation of different types of filters for atmospheric trace elements analysis by three analytical techniques

Different atmospheric aerosol samples were collected on three types of filters. Disks of both loaded and clean areas of each kind of filter were investigated by XRF, PIXE and Scanning Electron Microscope (SEM) methods. The blank concentration values of the elements Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br and Pb in the three types of fiters are discussed. It is found that for trace elemental analysis, the Nuclepore membrane filters are the most suitable for sampling. These have much lower blank element concentration values than the glass fibres and ash free filters. It was found also that the PIXE method is a more reliable analytical technique for atmospheric aerosol particles than the other methods.     

Comparison of different types of filters for atmospheric trace element analysis by three analytical methods

Different atmospheric aerosol samples were collected on three types of filters. From both of the loaded and clean areas of each kind of filter, different disks were cut and investigated by XRF, PIXE and scanning electron microscopy (SEM). The blank concentration values of the elements Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Br and Pb in the three types of filter are discussed. It is found that for trace elemental analysis, the Nuclepore membrane filters are the most suitable for sampling. These filters have much lower blank element concentrations than the glass fiber and ash free filters. It was found also that PIXE is a more reliable analytical technique for atmospheric aerosol particles than the other methods used.     

ToF-SIMS analysis of chemical composition of atmospheric aerosols in Beijing

Atmospheric aerosols collected from each season in urban Beijing have been studied using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The chemical composition of atmospheric aerosol particles during various atmospheric pollution levels was analyzed and distinguished by principal component analysis (PCA). The differences and sources of the components of the aerosol particles were explored. The results showed that the fine particulate matter from heavily polluted days mainly consists of inorganic salts and organic compounds, such as hydrocarbons, nitrogen- or sulfur-containing hydrocarbons, and their oxides. Samples collected from clean days in the four seasons were also analyzed. Only the samples collected in spring showed a significant difference from the other three seasons. We concluded that the main source of pollution in the Beijing urban area was fossil fuel combustion from motor vehicles.     

Speciation of copper and zinc in size-fractionated atmospheric particulate matter using total reflection mode X-ray absorption near-edge structure spectrometry

The health effects of aerosol depend on the size distribution and the chemical composition of the particles. Heavy metals of anthropogenic origin are bound to the fine aerosol fraction (PM_2.5). The composition and speciation of aerosol particles can be variable in time, due to the time-dependence of anthropogenic sources as well as meteorological conditions. Synchrotron-radiation total reflection X-ray fluorescence (SR-TXRF) provides very high sensitivity for characterization of atmospheric particulate matter. X-ray absorption near-edge structure (XANES) spectrometry in conjunction with TXRF detection can deliver speciation information on heavy metals in aerosol particles collected directly on the reflector surface. The suitability of TXRF-XANES for copper and zinc speciation in size-fractionated atmospheric particulate matter from a short sampling period is presented. For high size resolution analysis, atmospheric aerosol particles were collected at different urban and rural locations using a 7-stage May cascade impactor having adapted for sampling on Si wafers. The thin stripe geometry formed by the particulate matter deposited on the May-impactor plates is ideally suited to SR-TXRF. Capabilities of the combination of the May-impactor sampling and TXRF-XANES measurements at HASYLAB Beamline L to Cu and Zn speciation in size-fractionated atmospheric particulate matter are demonstrated. Information on Cu and Zn speciation could be performed for elemental concentrations as low as 140 pg/m³. The Cu and Zn speciation in the different size fraction was found to be very distinctive for samples of different origin. Zn and Cu chemical state typical for soils was detected only in the largest particles studied (2–4 μm fraction). The fine particles, however, contained the metals of interest in the sulfate and nitrate forms.     

Atmospheric trace metal characterization in industrial area of Lisbon, Portugal

Summary A set of 15 atmospheric aerosol samples was collected in an industrial area of Lisbon, Portugal and then analyzed by instrumental neutron activation analysis (INAA). Both fine and coarse aerosol samples were collected during November and December 2001 on polycarbonate filters with Gent samplers. The INAA methodology utilized both thermal and epithermal neutron irradiations. Compton suppressed and normal gamma-ray spectra were acquired simultaneously for each measurement and the elemental concentrations of 30 elements were determined. Enrichment factors, wind speed comparison and receptor modeling techniques were applied to obtain the different source contributions of the aerosols. Crustal, marine and anthropogenic sources were identified. The anthropogenic elements have origin mainly in the area close to the sampling site (<5 km), with the exception of Ca and V. A direct relationship was observed between the anthropogenic atmospheric aerosol concentrations and wind speed.     

Combined application of INAA and PIXE for studying the regional aerosol composition in Southern Africa

As part of the SAFARI-92 biomass buming experiment, aerosol collections were carried out with several size-fractionating sampling devices at a number of sites in Southern Africa. One of the samplers used at all ground-based sites was a stacked filter unit (SFU). The SFU samples were analyzed by both INAA and PIXE analysis. The present paper gives an intercomparison of the analytical results obtained in order to assess the accuracy and to check the quality assurance of the analytical procedures. Twenty-one common elements were determined by both INAA and PIXE. Concentrations of 13 elements (i.e., Na, Mg, Al, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Zn and Br) were generally measured with sufficient precision in both techniques for performing the intercomparison. The INAA and PIXE data were compared in terms of PIXE/INAA concentration ratios on a sample by sample basis for the coarse and fine size fraction separately. the atmospheric concentrations for K, Mn and Fe agreed within 5–10%, the agreement between the data for the other common elements was typically better than 15%. Possible explanations for lower than 1.0 ratios for Cl, Br and Na are presented. The common elements were classified into groups according to their detectability and sensitivity in each technique.     

Preparation and characterization of a new set of IAEA reference air filters using instrumental neutron activation analysis, proton-induced X-ray emission and Rutherford backscattering

A new set of reference air filters was prepared for proficiency testing of laboratories involved in air pollution studies organized by the International Atomic Energy Agency (IAEA). The set consists of one filter loaded with airborne particulate matter (APM) and one blank filter. Target values and their standard deviations were established using instrumental neutron activation analysis (INAA) and proton induced X-ray emission (PIXE) with proven accuracy. Rutherford backscattering (RBS) was used to help in deriving the necessary corrections in PIXE. Losses of individual elements from APM due to the wet deposition procedure were evaluated.     

Application of the Sulfuric Acid-Halide Salt Reaction to the Analysis of Sulfuric Acid Containing Aerosols

Abstract

A new X-ray fluorescence method for the determination of sulfuric acid in sulfuric acid containing aerosols is presented. The technique makes use of the reaction between sulfuric acid and potassium chloride yielding volatile hydrogen chloride and thus changing the C1/K ratio. Nuclepore^R membrane filters are first loaded with potassium chloride and then used for the collection of the aerosol under study. The chlorine and potassium X-ray signals are measured before and after the sampling of the acid aerosol, and the decrease in the Cl/K intensity ratio is taken as a measure for the amount of sulfuric acid collected.     

Speciation of arsenic in coarse and fine urban aerosols using sequential extraction combined with liquid chromatography and atomic fluorescence detection

An analytical procedure for speciation of As in urban aerosol samples was developed. The aerosols were collected by sequential filtration through membrane filters. Part of each filter was investigated by INAA for the total amount of As. Another part of the filters was treated by a sequential extraction procedure to differentiate between water-extractable, phosphate-extractable and refractory chemical forms. Water-extractable forms were further differentiated into anionic As species by HPLC-HGAFS. Extractability of As into water exhibited a clear dependency on the aerosol size fraction (12% in coarse fraction and 50% in fine fraction). Dependency of the phosphate extractable As on the aerosol size fraction seems not to be significant (10–15% in both size fractions). The remaining amount, i.e., about 78% of the coarse As and about 40% of the fine As was considered to be refractory or environmentally immobile As. Water-extractable As forms could only be attributed to arsenate.     

Speciation of arsenic in coarse and fine urban aerosols using sequential extraction combined with liquid chromatography and atomic fluorescence detection

An analytical procedure for speciation of As in urban aerosol samples was developed. The aerosols were collected by sequential filtration through membrane filters. Part of each filter was investigated by INAA for the total amount of As. Another part of the filters was treated by a sequential extraction procedure to differentiate between water-extractable, phosphate-extractable and refractory chemical forms. Water-extractable forms were further differentiated into anionic As species by HPLC-HGAFS. Extractability of As into water exhibited a clear dependency on the aerosol size fraction (12% in coarse fraction and 50% in fine fraction). Dependency of the phosphate extractable As on the aerosol size fraction seems not to be significant (10-15% in both size fractions). The remaining amount, i.e., about 78% of the coarse As and about 40% of the fine As was considered to be refractory or environmentally immobile As. Water-extractable As forms could only be attributed to arsenate.     

Direct on-strip analysis of size- and time-resolved aerosol impactor samples using laser induced fluorescence spectra excited at 263 and 351 nm

We report a novel atmospheric aerosol characterization technique, in which dual wavelength UV laser induced fluorescence (LIF) spectrometry marries an eight-stage rotating drum impactor (RDI), namely UV-LIF-RDI, to achieve size- and time-resolved analysis of aerosol particles on-strip. The UV-LIF-RDI technique measured LIF spectra via direct laser beam illumination onto the particles that were impacted on a RDI strip with a spatial resolution of 1.2 mm, equivalent to an averaged time resolution in the aerosol sampling of 3.6 h. Excited by a 263 nm or 351 nm laser, more than 2000 LIF spectra within a 3-week aerosol collection time period were obtained from the eight individual RDI strips that collected particles in eight different sizes ranging from 0.09 to 10 μm in Djibouti. Based on the known fluorescence database from atmospheric aerosols in the US, the LIF spectra obtained from the Djibouti aerosol samples were found to be dominated by fluorescence clusters 2, 5, and 8 (peaked at 330, 370, and 475 nm) when excited at 263 nm and by fluorescence clusters 1, 2, 5, and 6 (peaked at 390 and 460 nm) when excited at 351 nm. Size- and time-dependent variations of the fluorescence spectra revealed some size and time evolution behavior of organic and biological aerosols from the atmosphere in Djibouti. Moreover, this analytical technique could locate the possible sources and chemical compositions contributing to these fluorescence clusters. Advantages, limitations, and future developments of this new aerosol analysis technique are also discussed.     

Trace element determination in aerosols from the Antarctic Peninsula by neutron activation analysis

The knowledge of the composition of atmospheric aerosols in remote areas, like the Antarctic Peninsula is of great importance for the study of long-range transport of atmospheric contaminants and also from the climatological point of view. Instrumental neutron activation analysis was applied in the present work to determine the elements Al, V, Mn, Na, Cl, Ca, Au, Br, Sb, Sc, Fe, Zn, K, Th and La in aerosol samples collected in the Brazilian Antarctic Station Comandante Ferraz (62° S, 58° W) located on King George Island in the Antarctic Peninsula. The sources of the aerosols were investigated by means of Enrichment Factors and Principal Factor Analysis. Both methods yielded similar results. Sea and soil were identified as the major sources of aerosols, in the samples collected at the Brazilian Station.     

Application of a wavelength-dispersive particle-induced X-ray emission system to chemical speciation of phosphorus and sulfur in lake sediment samples

The chemical speciation of phosphorus and sulfur in lake sediment was performed by analyzing Kα X-ray spectra recorded with a high-resolution wavelength-dispersive particle-induced X-ray emission (WD-PIXE) system. The concentrations of phosphorus and sulfur in the sediment were 2500 and 7000 ppm, respectively. To measure both minor elements in a reasonable measurement time, a 2-MeV proton beam with a high current density (6 nA/mm²) was used for the chemical speciation. The possible chemical state change caused by the proton irradiation was studied in order to determine the maximal irradiation time without significant change. We found that the chemical states of phosphorus and sulfur were stable under a beam current density of 6 nA/mm² and a measurement time of 60 min (phosphorus) and 90 min (sulfur). The chemical states of phosphorus and sulfur were determined to be P⁵⁺ and a mixture of S²⁻ and S⁶⁺, respectively.     

Investigation of the electronic structure of paradichlorobenzene using x-ray emission spectroscopy

The Cl Kβ emission spectra from disordered and ordered molecules of paradichlorobenzene were recorded using a high-resolution curved crystal spectrograph. It was possible to separate the component polarized perpendicularly to the molecular plane from the in-plane polarized radiation. Thus information is obtained about the molecular π orbitals. By comparison with the photoelectron spectrum a partial assignment of the structural features of the spectra to the molecular orbitals is achieved.     

Investigation of winter atmospheric aerosol particles in downtown Katowice using XPS and SEM.

X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemical composition of atmospheric particles (PM-10 and PM-2.5), collected in downtown Katowice, Upper Silesia, Poland, in the winter season (November and December 2000). Carbon- and oxygen-containing species dominated the particulate surface with traces of N, S, Si, Cl, Na, Zn, Al, Cu, Fe, Ca, K, Mg, Pb, and P present. Additionally, the size, morphology, and chemical composition of about 300 of the individual atmospheric particles were analyzed by high-resolution scanning electron microscopy and electron probe microanalysis. A number of aluminosilicates and metallic elements such as Fe, K, Mg, Zn, as well as rare earth elements, were detected by SEM. The results obtained show that the analyzed aerosol is of natural and anthropogenic origin. Particles containing sulfur compounds as well as oxygen and sodium in downtown Katowice come mainly from the east and southeast sectors.     

Characterization of novel di- and tricarboxylic acids in fine tropical aerosols

Three unknown di- and tricarboxylic acids were characterized in the fine size fraction of aerosols which were collected during the wet season in the Amazon basin (Rondonia, Brazil). For the structural characterization of the methyl esters of these unknown compounds, mass spectrometry with electron ionization (EI) and tandem mass spectral techniques combined with gas chromatographic (GC) separation were employed. Fragment and parent ion spectra were recorded during elution of the GC peaks by linked scanning of the B and E sectors in combination with high-energy collision-induced dissociation. The fragmentation patterns of significant ions in the first-order EI spectra were also obtained for nonanedioic acid, which was examined as a model compound. The compounds were tentatively identified as 4-acetyloxyheptanedioic acid and cis and trans isomers of 5-hexene-1,1,6-tricarboxylic acid. Since there were indications of biomass burning during the aerosol sampling the di- and tricarboxylic acids characterized in the present work could be markers for biomass burning. Furthermore, the characterization of di- and tricarboxylic acids in the fine size fraction of atmospheric aerosols may be important for assessing the effects of organic aerosols in cloud formation.     

Estimation of trace elements in some anti-epileptic medicinal plants by PIXE

Trace elemental analysis was carried out in various parts of 10 anti-epileptic medicinal plants using PIXE technique. A 3?MeV proton beam was used to excite the samples and spectra were recorded using a Si(Li) detector. Data analysis was done using Gupix Software. The elements Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br and Sr were identified and their concentrations estimated. The presence of some of these trace elements is correlated with the anti-epileptic curative property of these plants.     

Physical and chemical forms of radionuclides of 38S, 38Cl, 39Cl, and 82Br, produced at a high-energy proton accelerator facility

High-energy protons and neutrons produce various radionuclides in the air, mainly through the nuclear spallation of atmospheric elements. Air samples were collected from the EP-2 tunnel of the KEK 12 GeV proton synchrotron facility with a filter pack, which consisted of a membrane filter for aerosols, a Na₂CO₃-impregnated filter for acidic gases, and an activated carbon fiber filter for non-acidic gases. Sulfur-38 was found on the membrane and Na₂CO₃-impregnated filters, ³⁸Cl and ³⁹Cl were on the membrane, Na₂CO₃-impregnated, and ACF filters, and ⁸²Br was only on the ACF filter. The results on the relative abundances of aerosol and gaseous acidic components have indicated that ³⁸Cl produced by thermal neutron capture, which is the main reaction for ³⁸Cl production in the EP-2 tunnel air, are likely not to be present as aerosol or acidic gas. This was similar to the case of ⁸²Br produced by thermal neutron capture.