An investigation of calibration materials for the measurement of metals in ambient particulate matter on filters by LA-ICP-MS

Three different types of simple and low-cost calibration material for the measurement of the metals content of ambient particulate matter (PM) on filters using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) have been compared: cellulose ester filters spiked with multi-element calibration solutions, pellets of compressed ambient particulate matter certified reference material (CRM), and powdered ambient particulate matter CRM adhered to a surface. Elements determined were As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn, each at approximate levels of 1000?ng per filter. Blank filters spiked with multi-elemental standards were found to be significantly more reproducible and repeatable than materials based on powdered reference materials. However, a comparison of these spiked filters with real samples of ambient PM showed that the analytical sensitivities obtained per mass of analyte were significantly different. It is concluded that the spiked filters could act as very effective quality control standards correcting, to within 1%, drifts in LA-ICP-MS measurements of up to 10%, or as indirect calibration materials supported by additional measurements using traditional wet chemical techniques.     

Determination of metals in thoracic fraction of ambient air particulate matter

The present work deals with the optimization and validation of a method for the quantitative simultaneous ICP determination of metals in ambient air particulate matter. The attention has been focused on the thoracic fraction (PM10) and twelve different metals were chosen on the basis of their toxicity and of their possible use as chemical tracers. The microwave acidic digestion of the samples has been performed in the presence of different reagents and under different conditions and particular attention has been paid to the optimization of the whole analytical procedure and to the evaluation of accuracy and precision related to the single operative steps. The interferences due to the reagents and to the sampling supports have also been evaluated. In addition, the analytical procedure has been checked by examining the equivalence of results related to parallel sampled filters pairs.     

Microwave digestion-ICP-MS for elemental analysis in ambient airborne fine particulate matter: rare earth elements and validation using a filter borne fine particle certified reference material

NIST standard reference material SRM 2783 was employed to validate a high temperature, high pressure, two-stage microwave assisted acid digestion procedure using HNO₃, HF and H₃BO₃ developed for the analysis of trace elements (including rare earths) in atmospheric fine particulate matter (PM_2.5) prior to inductively coupled plasma mass spectrometry (ICP-MS). This method quantitatively solubilized Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sb, Cd, Cs, Ba, Pb, Th, U and several rare earth elements (REEs) (La, Ce, Pr, Nd, Gd, Dy, Er, Sm and Eu) from SRM 1648 and SRM 2783. A small amount of HF in the first stage was required to dissolve silicates necessitating the corresponding addition of H₃BO₃ in second stage to dissolve fluoride precipitates of Mg, La, Ce and Th. The optimized microwave dissolution—ICP-MS method detected Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cd, Mo, Sb, Cs, Ba, La, Ce, Pr, Nd, Sm, Gd, Pb, Th and U at trace to ultra-trace levels in ambient airborne fine particles from three sites in North Carolina. La to light lanthanide signature ratios suggested that soil and motor vehicles are the dominant REE sources in SRM 2783 and PM_2.5 samples collected during this study.     

Method for measurement of polycyclic aromatic hydrocarbons in particulate matter in ambient air

A method for measuring polycyclic aromatic hydrocarbons (PAHs) in ambient air is described. The particulate matter is collected on fibre-glass filters. The loaded filters are placed in tetrahydrofuran and the PAHs dissolved with the aid of ultrasonics and analysed by high-performance liquid chromatography on a reversed-phase column with a methanol-water mixture as mobile phase. The PAHs are detected by use of a UV-detector and the 254-nm mercury emission line. The method is rapid and adequate for measuring about 15 PAH-components in ambient air.     

An optimized method for the determination of volatile and semi-volatile aldehydes and ketones in ambient particulate matter

A method has been developed to measure aldehydes and ketones associated with atmospheric particles. Carbonyl compounds from particulate material collected on Teflon-coated glass-fiber filters were simultaneously extracted and derivatized with an appropriate 2,4-dinitrophenylhydrazine (2,4-DNPH) solution. The efficiency of this procedure utilizing various 2,4-DNPH concentrations and solvent compositions was studied for 13 carbonyl compounds of atmospheric importance. These include formaldehyde, acetaldehyde, acetone, dicarbonyls such as glyoxal and methylglyoxal, and biogenic carbonyls such as pinonaldehyde and nopinone. An extraction solution containing 3 × 10^?2 M 2,4-DNPH, in 60% acetonitrile/40% water, and pH 3 was most efficient in extracting and derivatizing these aldehydes and ketones (83-100% recovery). Improved sample enrichment and 2,4-DNPH purification methods were developed that afforded detection limits of 0.009-5.6 ng m^?3. The relative standard deviation for replicate analyses were 1.9-10.1%. Carbonyl compounds in ambient particulate samples were quantified during a recent field study. Median values for nine carbonyl species ranged from 0.01-33.9 ng m^?3 during the study.     

XPS study of carboxylic acid layers on oxidized metals with reference to particulate materials

Low‐molecular‐weight organic additives such as stearic acid are commonly used as surface additives in powder injection moulding (PIM). It is therefore important to know how the additives interact with the surface of the powder used. In this study, such interactions are studied by means of controlled adsorption of carboxylic acids on the oxides of interest. The oxides are prepared by oxidation of flat samples of Fe, Cr, Mn and Si. Surface chemical characterization is done by means of XPS, the main approach on flat samples being a comparison of angle‐resolved analysis and the use of the Tougaard nanostructure analysis technique. Taking advantage of this comparison, the Tougaard method is then applied in the evaluation of XPS analyses of stainless‐steel powder with adsorbed stearic acid. In addition, time‐of‐flight SIMS analysis is used to verify the adsorption of stearic acid on the powder surface. It is shown that Tougaard nanostructure analysis can be used for determining the thickness of an organic layer on particulate material. The layer thickness of adsorbed stearic acid was estimated to be ～20 Å, corresponding to monolayer adsorption. Time‐of‐flight SIMS analysis verified the adsorption of stearic acid on the powder surface. From the XPS analysis of flat samples it was determined that the use of the metal/oxide universal cross‐section in Tougaard nanostructure analysis best described the increased background due to adsorption of carboxylic acids, and that information about molecular orientation could be gained. Copyright © 2003 John Wiley & Sons, Ltd.     

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.     

The determination of silicon in airborne particulate matter by XRF and LA-ICP-MS

This study reports the analysis of Si in airborne particulate matter by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as well as X-ray fluorescence (XRF). It was found that Si concentration in airborne particulates collected on PTFE-membrane filters could be accurately determined with a laser beam operated at 160 mJ free running mode, 6.5 mm defocusing distance and 0.8 l/min carrier gas flow rate during the LA-ICP-MS measurement. Standard filters prepared by NIST SRM 1648 urban particulates were used for both XRF and LA-ICP-MS not only to establish the calibration curves of Si, but also to examine the proposed method's effectiveness. The capability of applying both methods for natural sample analysis was also examined. Particulate loaded filter samples collected from a heavily polluted metropolitan area of Kaoshiung, Taiwan were initially measured by XRF, then by LA-ICP-MS. An intercomparison between them was thus performed. As a result, both XRF and LA-ICP-MS proved to be the valid analytical methods for directly determining Si concentrations in airborne particulates on PTFE membrane filters.     

Deposition measurement of particulate matter in connection with corrosion studies

A new passive particle collector (inert surrogate surface) that collects particles from all directions has been developed. It was used to measure particle deposition at 35 test sites as part of a project that examined corrosion of materials in order that variation in particulate material could be used in development of dose–response functions in a modern multi-pollutant environment. The project, MULTI-ASSESS, was funded by the EU to examine the effects of air pollution on cultural heritage. Passive samplers were mounted rain-protected, and both in wind-protected and wind-exposed positions, to match the exposure of the samples for corrosion studies. The particle mass and its chemical content (nitrate, ammonium, sulfate, calcium, sodium, chloride, magnesium and potassium) were analysed. The loss of light reflectance on the surrogate surface was also measured. Very little ammonium and potassium was found, and one or more anions are missing in the ion balance. There were many strong correlations between the analysed species. The mass of analysed water-soluble ions was fairly constant at 24% of the total mass. The particle mass deposited to the samplers in the wind-protected position was about 25% of the particles deposited to an openly exposed sampler. The Cl⁻/Na⁺ ratios indicate a reaction between HNO₃ and NaCl. The deposited nitrate flux corresponds to the missing chloride. The Ca²⁺ deposition equals the deposition and the anion deficiency. The deposition most likely originates from SO₂ that has reacted with basic calcium-containing particles either before or after they were deposited. The particle depositions at the urban sites were much higher than in nearby rural sites. The deposited mass correlated surprisingly well with the PM₁₀ concentration, except at sites very close to traffic.     

Size distribution and characteristics of chemical components in ambient particulate matter.

Ambient particulate matter and gas in Kyoto were investigated by gravimetric analysis, X-ray fluorescence spectrometry, and ion chromatography in order to clarify their behavior and origin. The size distribution and characteristics of the chemical components in ambient particulates collected on PTFE membrane filters using an Andersen air sampler were examined from August 2001 to April 2004. A four-stage filter pack method was used to sample the atmosphere for the determination of gas (SO2, HNO3, HCl, NH3) and particulate matter (SO42, NO3, Cl-, Na+, K+, Ca2+, Mg2+, NH4+) concentrations from October 2002 to April 2004. The concentration of SPM mass was in the range of 6.7 - 80.2 microg/m3. The size distributions of SPM mass were bimodal, peaking at around 0.65 - 1.1 and 3.3 - 4.7 microm, and 40 - 85% of SPM mass was fine particles (< 2.1 microm). Na, Mg, Al, Si, Ca, Cl, and Fe were mainly present in coarse particles (2.1 to 11.0 microm), while S was present in fine particles. The concentrations of Al, Si, Ca, Mg, and Fe in fine particles increased from March to April in 2002, and those in coarse particulates increased in November 2002 and from March to April in 2004. This may be the effect of the continental yellow sand "Kosa." The differences in the size distributions of Al, Si, Ca, Mg, and Fe in particles may depend on differences in their place of occurrence and course of transport from China to Japan. The concentration of HCl gas was higher than that of particulate chloride ion in summer. Nitric acid gas existed at higher concentrations in summer, but fine particulate nitrate ion was observed in winter. The gaseous-to-fine aerosol nitrate fraction became higher at warmer temperatures. Coarse sulfate was below 10%, and SO2 gas and fine particulate sulfate were above 90%.     

Neutron activation analysis of platinum metals in airborne particulate matter

A method is described for the determination of Au, Pt, Pd, Ag and Ir in two atmospheric aerosol samples, namely in Ghent and in the Milanese intercomparison sample. After neutron irradiation the samples are fused with Na₂O₂. Gold is extracted with ethylacetate, Pt precipitated as (NH₄)₂PtCl₆ Pd as dimethylglyoximate, Ag as chloride and Ir separated by anion-exchange adsorption and batch extraction. Ge(Li) gamma-spectrometry is applied for all determinations. The concentrations in ng·g⁻¹ in the samples are respectively: Au: 49 and 3000; Pt: below 100 for both samples; Pd: 7 and 28; Ag: 6000 and 14 000; Ir: 2.5 and 1.3.     

Comparison of extracting solutions for elemental fractionation in airborne particulate matter

It is here described the comparison of extraction efficiency of some solutions (acetate buffer, deionized water, diluted HNO₃ and EDTA) frequently adopted in literature for evaluating the elemental solubility in airborne particulate matter. This comparison was performed considering the distribution of As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, S, Si, Sb, Sn, Sr, Ti, V, Zn between the extractable and mineralized residual fractions on the NIST 1648 certified material, PM₁₀ real samples and size-segregated samples, collected by a 13-stage impactor.The extracting solutions were evaluated by comparing extractive efficiencies and robustness towards some factors, such as acidity and concentration of complexing species, that have great environmental variability and that could be able to modify the extractive efficiency.Furthermore, extraction methods application to size-segregated samples allowed estimating the selectivity of extracting solutions towards dimensionally characterized emission sources, as dusts originated from abrasion and road dust re-suspension.On the basis of the obtained results, it was possible to define the main advantages and disadvantages resulting from the use of different extracting solutions, necessary to make possible the comparison of environmental studies carried out in different extractive conditions and to start up a proper study for harmonizing extracting procedures.     

Chemical characterization of selected metals by X-ray fluorescence method in particulate matter collected in the area of Krakow, Poland

This study presents the results of year long (2007–2008) particulate matter collecting campaigns. The three particle size fractions of particulate matter were collected in Krakow, Poland. Fine fraction consists of particles of a diameter below 2.5 µm, medium is between 2.5 and 8 µm and coarse fraction contains particles above 8 µm. Elemental concentrations were evaluated for each sample. Following elements were measured by EDXRF method: K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, Br, and Pb. During each sampling campaign meteorological parameters such as temperature, wind speed, wind direction, humidity were taken from the same place. The highest values of mass particulate matter showed results from January 2008 and April 2008. These were about 14 µg/m³ for fine fraction, 8 µg/m³ for medium and 16 µg/m³ for coarse fraction. The lowest values were observed in May 2007, they were 4, 6, 6 µg/m³, respectively. During the winter season the wind speed was low and particulate matter remained in the air in high concentrations. In May 2007 the speed of wind was higher, reaching 2–3 m/s. PM was blown away from the city from the direction of N–W. Measured concentrations of elements were low, they were below permissible values specified by EU. The coarse fraction concentrations of Ca, Mn, and Fe were higher and characterized by the same trend. These samples were collected when the wind speed was low and its direction was from south-east. As concentrations of Cr, Cu, and Zn were low, these elements did not come from the south-east direction of Krakow. Concentration of Br correlates to the concentration of Pb. It suggests that they came from the same source (vehicles fuels burning).     

Evidence of tin and other anthropogenic metals in particulate matter in Lisbon, Portugal

Thermal and epithermal neutron activation analysis techniques were used to analyze 27 Teflon air filters which were exposed to ambient air in Lisbon, Portugal, in February 2007. Tin was detected which is strongly suggestive of an anthropogenic source. Arsenic, antimony and copper were shown to be highly correlated, which is also suggestive of anthropogenic pollution. Trace element analysis of short- and medium-lived isotopes was performed yielding concentration information of various elements. Analytical sensitivities were enhanced using a Compton suppression system. Enrichment factor analysis shows that arsenic, tin, zinc, copper and antimony are at elevated concentrations in the Lisbon atmosphere.     

An ion chromatographic analysis of water-soluble,short-chain organic acids in ambient particulate matter

Recent studies have shown that the inclusion of water-soluble short-chain (WSSC) organic acids in source apportionment using positive matrix factorization (PMF) resulted in an improvement in the model's ability to resolve sources, and in understanding secondary particle formation. In the United States, numerous network samplers are operational. Quartz-fibre filters for thermal optical carbon analysis have been collected over a period of years as a part of these sampling campaigns on a routine basis. However, only a small portion of these filters are used for the carbon analysis. Thus, there is the potential to utilize these samples to enhance organic speciation for subsequent use in source apportionment. In this work, an ion-chromatographic method was developed to identify and quantify the WSSC organic acids present in fine particulate matter (PM_2.5). Samples collected to measure the concentrations of particles (PM_2.5) in south-western (Stockton) and northern (Potsdam) New York, USA from November 2002 to June 2004 were used in this study. Acetic, formic, propionic, oxalic, and malonic acids were successfully identified. The identified species accounted for 5–15% of the organic matter mass and thus enhance the knowledge of atmospheric organic-matter constituents. Oxalic acid was the most abundant species at Potsdam and Stockton with median concentrations of 17.71?ng?m^?3 and 92?ng?m^?3, respectively. Acetic and formic acids were present in Potsdam at median concentrations of 12.54?ng?m^?3 and 14.48?ng?m^?3, while at Stockton they were present at 57.58?ng?m^?3 and 51.54?ng?m^?3, respectively. The median concentration values for all acids at Stockton were higher than Potsdam. These observations are consistent with a study conducted in a semi-urban location, Schenectady, New York. At both sites, propionic and malonic acids were found in much lower concentrations when compared with the other acids. The concentration time series of various acids and seasonal variations in individual acids are discussed. The co-variance of acetic and formic acids is also outlined.     

Comparison of inductively coupled plasma-atomic emission spectrometry, anodic stripping voltammetry and instrumental neutron-activation analysis for the determination of heavy metals in airborne particulate matter

The capability of three analytical techniques, inductively coupled plasma-atomic emission spectrometry (ICP-AES), anodic stripping voltammetry (ASV), and instrumental neutron-activation analysis (INAA) have been compared for the determination of Cd, Fe, Pb, and Zn in airborne particulate matter, collected on cellulose filters, from the atmosphere of the large area of Thessaloniki, Greece. Two procedures were tested for quantitative leaching of these elements from the filters before ICP-AES and ASV, digestion with aqua regia in a Teflon autoclave, after dissolution of the organic matter with HClO4 under ambient conditions, and ultrasonic extraction with a mixture of HNO3 and HCl. Validation of the leaching and digestion procedures revealed that digestion in the autoclave is more effective, especially for Fe. The concentrations of these elements over a decade in both industrial and urban areas of the investigated region are compared.     

Examination of a procedure for the production of a simulated filter-based air particulate matter reference material

An approach for producing simulated air particulate matter (APM) deposited on filters has been developed and investigated as to its usefulness for yielding large batches of filters as a future reference material. The APM deposited on the filters was a material collected from an urban industrial area, and had been milled to approximate a material of PM-2.5 particle size distribution. The milled APM material was loaded onto filter substrates (Nuclepore) through the deposition of aliquots from a liquid suspension via vacuum filtration. It should be noted that these filters do not represent a typical PM-2.5 elemental composition, since the milling increased the proportion of crustal materials and the suspension in liquid decreased the sulfate content. Homogeneity between filters was tested using INAA (whole filter analysis) and ED-XRF and PIXE and was estimated to be in the 5% range (relative standard deviation). Homogeneity within the filters and among the filters was also tested using micro-XRF and found to be acceptable for the elements tested. The results of the tests carried out on the filters indicate that this approach is appropriate for large-scale production of similar filters for distribution as reference materials.     

Optimised chromatographic method for the measurement of selected polychlorinated biphenyls in ambient air

The focus of this study was to optimise selected polychlorinated biphenyl analysis in air by gas chromatography. Sample preparation was improved by using an automatic solid/liquid extraction system and columns with 1.5 g of Florisil for cleaning extracts. Better precision on clean-up results was obtained from Florisil cartridges, when compared to those obtained with silica gel. Analytical procedure was checked by participating in an inter-comparison exercise. Finally, we have considered usefulness of evaluating uncertainties associated to our method because of the large handling samples and the extremely low concentrations of PCBs in ambient air.