A new approach for determination of crustal and trace elements in airborne particulate matter

An ICP-OES procedure was developed for fast and accurate determination of various crustal (Al, Ca, Fe, Mg, Si) and trace elements (Ba, Cu, Mn, Na, K, Sr, Ti, Zn) in airborne particulate matter. The method is based on a preliminary treatment of the aerosol samples with a mixture of nitric acid and hydrogen peroxide at elevated temperature leading to a mineralization of the organic sampling substrate, dissolution of soluble material and homogeneous suspension of the remaining non-soluble fraction. After dilution the derived slurry solutions were measured using ICP-OES. The reproducibility of analysis given as the relative standard deviation (% RSD) varied between 3.2 and 6.8% for bulk constituents such as Al, Ca, Fe, Mg and Si whereas values ranging from 3.5 to 9.1% were obtained for trace metals present with distinctly lower abundance in PM10 (e.g. Ba, Cu, Mn, Sr, Zn). The limits of detection (LOD) calculated as three times the standard deviation (3σ) of the signal derived from filter blank samples ranged from approximately 1?ng?m^?3 (Sr) to 71?ng?m^?3(Ca). The developed procedure was evaluated by comparing the obtained results with the findings derived for the same set of aerosol samples analyzed using a microwave procedure for sample dissolution with subsequent ICP-OES analysis. Finally the developed procedure was applied for the analysis of crustal and trace elements in PM10 samples collected at an urban site (Getreidemarkt, Vienna) and a rural site (Hartberg, Styria), in Austria. The concentrations of the investigated crustal elements varied between some hundred ng?m^?3 and few µg?m^?3 with highest concentrations for Fe and Si, distinctly reduced concentrations ranging from some ng?m^?3 (Sr) to more than hundred ng?m^?3 (K) were found for trace elements. Observed PM10 concentrations were found to be in accordance to literature findings from urban sites in central Europe.     

Recent developments in assessment of bio-accessible trace metal fractions in airborne particulate matter: A review

In the last years a great deal of research has been focused on the determination of harmful trace metals such as Cd, Co, Cr, Cu, Ni or Pb in airborne particulate matter (APM). However, the commonly applied determination of total element concentrations in APM provides only an upper-end estimate of potential metal toxicity. For improved risk assessment it is important to determine bio-accessible concentrations instead of total metal contents. The present review gives an overview of analytical procedures reported for measurement of bio-accessible trace metal fractions in APM. The different approaches developed for extraction of soluble trace metals in APM are summarized. Furthermore the analytical techniques applied for accurate determination of dissolved trace metals in the presence of complex sample matrix are presented. Finally a compilation of published results for bio-accessible trace metals in APM is included.     

Determination of water-soluble and insoluble compounds in size classified airborne particulate matter

The elemental composition of water soluble and acid soluble size-fractionated airborne particulate matter (APM) was investigated. PM2.5 and PM2.5-10 samples were collected every three days from October 2006 to October 2007 in Buenos Aires, Argentina. The collection was performed on Nucleopore® filters using a GENT sampler. Samples containing fine and coarse particles were subjected to an aqueous leaching to obtain information on the dissolution behaviors of ions, metal and metalloids. Key elements namely, Al, Ba, Ca, Cr, Cu, Fe, Mg, Mn, Pb, Se, Ti and Zn were determined in each fraction by inductively coupled plasma optical emission spectrometry (ICP OES). In the aqueous fractions, Cl⁻, SO₄²⁻, Na⁺ and NH₄⁺ were determined by high performance liquid chromatography (HPLC). A (6:2:5) mixture of nitric, hydrochloric and perchloric acids was used for leaching metals from the residual filters. For validation of the extraction procedure, the ICP OES measurements the Standard Reference Material NIST 1648 (Urban particulate matter) was subjected to the same analytical procedure that the samples loaded with APM. Total analyte concentration varied from 333.2 μg g^− 1 (equivalent to 3.7 ng m^− 3) for Ti to 692 mg g^− 1 (equivalent to 2.47 μg m^− 3) for Ca.     

Evaluation of a microwave-assisted extraction technique for determination of water-soluble inorganic species in urban airborne particulate matter

A simple and rapid microwave-assisted extraction (MAE) technique has been developed for the determination of water-soluble inorganic species (cations: Na⁺, NH₄⁺, K⁺, Ca²⁺ and Mg²⁺ and anions: F^–, Cl^–, NO₃^–, PO₄^3– and SO₄^2–) in airborne particulate matter. The analytes were extracted under different treatment conditions such as microwave power and extraction time. They were quantified using ion chromatography. The observed concentrations and recovery yields obtained under different conditions were compared. The results of a comparison between this MAE and sonication using NIST SRM 1648 are also given in this paper. The optimized MAE technique gave results in good agreement with the values obtained by the sonication. For some ions, for example Mg²⁺ and K⁺, recovery was low with both techniques. The results demonstrated that the optimized MAE is fast and efficient compared with conventional ultrasonic extraction. Urban airborne particles were collected and subjected to the MAE followed by the IC analysis to determine the relative proportions of different water-soluble inorganic species. These results are briefly discussed.     

Determination of water soluble trace metals in airborne particulate matter using a dynamic extraction procedure with on-line inductively coupled plasma optical emission spectrometric detection

A novel continuous-flow system for the dynamic extraction of water soluble metal fractions in airborne particulate matter (APM) with subsequent inductively coupled plasma optical emission spectrometric (ICP-OES) analysis of derived extracts is presented. The fully automated extraction system with on-line multi-element detection offers enhanced sensitivity when compared to batch-wise counterparts; additionally it provides information about the extraction process. With the developed procedure detection limits in the order of 1.5 (Ba) to 8.0 (Ni) ng extractable mass per investigated sample could be achieved, which translates to method detection limits for soluble metal concentrations in APM ranging from 0.2 ng m⁻³ (Ba) to 0.9 ng m⁻³ (Fe). Reproducibility of analysis was determined by replicate measurement (n = 6) of an APM sample with an aerodynamic diameter ≤10 μm (PM10), derived results varied between 3.5% (Mn) and 12.1% (Ni) relative standard deviation. Method validation was accomplished by comparison of extracted soluble and remaining non-soluble fractions with the total metal contents of the investigated PM10 samples, showing an excellent mass balance for all elements. Application of the developed procedure for the analysis of water soluble metal fractions in PM10 samples (n = 16) from Linz (Austria) indicated a high variability of extractable fractions ranging from 11.7 ± 7.2% (Fe) to 48.8 ± 15.4% (Mn) of the total metal contents.     

Inductively coupled plasma optical emission spectrometric determination of trace element in PM10 airborne particulate matter collected in an industrial area of Argentina

Trace metals of relevance from the environmental and toxicological point of view were quantified in the city of Campana, Buenos Aires, Argentina. The collection of particulate matter was performed on ash-free fiber glass filters using high-volume samplers with a PM₁₀ sampling head, during a 3-month period in 2002. An acid leaching of elements deposited on the filters was adopted paying special attention to the recovery of volatile elements. Analysis was performed by inductively coupled plasma optical emission spectrometry (ICP OES) to ascertain the concentrations of 12 key elements, namely, Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn. The validation of the procedure was performed by the analysis of the standard reference material NIST 1648, urban particulate matter, and good agreement between concentrations found and the reported certified values was achieved. Blank filters were spiked with the analytes investigated and the recoveries varied between 83% and 92%. Metal concentrations spanned the range 0.03 ng m⁻³ (equivalent to 0.42 μg g⁻¹) for Cd to 1.9 μg m⁻³ (equivalent to 29.7 mg g⁻¹) for Fe. The results obtained show that the pollutants of special environmental and health concern are As and Pb. Mean As concentration was higher than the guideline value associated with an excess cancer risk of 1:10⁻⁶, reported by the World Health Organization (WHO). Lead is the only element that showed higher concentrations than those recently measured in the large and heavily trafficked metropolitan area of Buenos Aires. Cadmium>Pb>As>Zn>Cu are the elements more enriched in airborne PM₁₀.     

Determination of platinum in urine and airborne particulate matter from Budapest and Vienna

Urine samples taken from 100 adults living in the city centres of the two capitals were analysed by the same inductively coupled plasma quadrupole mass spectrometer following their 10-fold dilution with bidistilled water. The mean concentration values of platinum related to creatinine were about three times higher in the Hungarian samples than in the Austrian ones. Six particulate matter samples were collected by a Gent-type two-stage sampler in the districts of the two capitals, which have high traffic density. The polycarbonate filters containing the fine (d<2 μm) and the coarse (d=2–10 μm) fractions were digested in a microwave assisted digestion system and analysed by the same high-resolution inductively coupled plasma mass spectrometer. The respirable, fine fractions of aerosols collected in Budapest contained approximately twice as much platinum than the aerosols from Vienna. However, the coarse fraction showed a contrary picture, with five times higher Pt concentration in the samples collected in Vienna.     

Optimization and validation of a low temperature microwave-assisted extraction method for analysis of polycyclic aromatic hydrocarbons in airborne particulate matter

A low temperature microwave-assisted extraction method (MAE) is reported for the analysis of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter (PM). The main parameters affecting the extraction efficiency (choice of extractants, microwave power, and extraction time) were investigated and optimized. The optimized procedure requires a 20 ml mixture of acetone:n-hexane (1:1) for extraction of PAHs in PM at 150 W of microwave energy (20 min extraction time). Clean-up of MAE extracts was not found to be necessary. The optimized method was validated using two different SRM (1648-urban particulate matter and 1649a, urban dust). The results obtained are in good agreement with certified values. PAHs recoveries for both reference materials were between 79 and 122% with relative standard deviation ranging from 3 to 21%. Detection limits were determined based on blank determination using two kinds of quartz filter substrates (n = 10), which ranged from 0.001 (0.03) ng m⁻³ (pg/μg) for B(k)Ft to 1.119 (37.3) for Naph in ng m⁻³ (pg/μg), respectively. The repeatability and day-to-day reproducibility obtained in this study were in the range of 4-16 and 3-25% for spiked standards and SRM 1649, respectively. The optimized and validated MAE technique was applied to the extraction of PAHs from a set of real world PM samples collected in Singapore. The sum of particulate-bound PAHs in outdoor PM ranged from 1.05 to 3.45 ng m⁻³ while that in indoor PM (cooking emissions) ranged from 27.6 to 75.7 ng m⁻³, respectively.     

Analytical methods for assessing metal bioaccessibility in airborne particulate matter: A scoping review

In contrast to the existence of standardized methods to assess metal bioaccessibility via the gastrointestinal route, there are no widely-accepted, established in vitro testing protocols to measure elemental solubility in the human lung. This may be attributed, in part, to the difficulty associated with simulating the lung’s complex in vivo conditions. The purpose of this review is two-fold: (1) to determine how the bioaccessibility of metals associated with ambient particulate matter (PM) in the human lung has been assessed in the literature, and (2) examine the suitability and biological relevance of applied methods for the measurement of metal bioaccessibility employed to date.     

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.     

Evaluation of polyurethane foam, polypropylene, quartz fiber, and cellulose substrates for multi-element analysis of atmospheric particulate matter by ICP-MS

Traditional methods for the analysis of trace metals require particulate matter (PM) collected on specific filter substrates. In this paper, methods for elemental analysis of PM collected on substrates commonly used for organic analysis in air quality studies are developed. Polyurethane foam (PUF), polypropylene (PP), and quartz fiber (QF) substrates were first digested in a mixture of HNO₃/HCl/HF/H₂O₂ using a microwave digestion system and then analyzed for elements by inductively coupled plasma mass spectrometry. Filter blanks and recoveries for standard reference materials (SRMs) on these substrates were compared with a cellulose (CL) substrate, more commonly used for trace metal analysis in PM. The results show concentrations of filter blanks in the order of QF > PUF > PP > CL with a high variability in PUF and PP blanks relative to QF. Percent recovery of most elements from the SRMs on all substrates are within ±20% of certified or reference values. QF substrates showed consistent blanks with a reproducibility better than ±10% for the majority of elements. Therefore, QF substrates were applied to ambient PM collected in a variety of environments from pristine to polluted. Concentrations of field blanks for ≥18 of 31 elements analyzed on a small section of QF substrate are ≤25% of the amounts present in samples for urban atmospheres. Results suggest that QF used in a high-volume sampler can be a suitable substrate to quantify trace elements, in addition to organic species and hence reduce logistics and costs in air pollution studies.

Separation and analysis of nitroarenes from airborne particulate organic matter by HPLC and capillary GC-MS methods

Normal-phase HPLC has been applied to the separation of nitroarenes from dichloromethane extracts from airborne particulate matter samples collected in urban regions of Upper Silesia. GC-MS and capillary gas chromatography with NP detector analysis of the nitroarene fraction made it possible to identify and determine quantitatively those compounds which dominate in the organic matter emitted to the atmosphere in highly industrialized regions (2-nitrofluorene, isomeric nitroarenes of MW = 247, i.e. nitropyrene/nitrofluoranthene/nitroacephenanthrylene).     

Measurement of anions in ambient particulate matter by ion chromatography: A novel sample preparation technique and development of a generic uncertainty budget

A novel sample preparation technique for the measurement of anions in particulate matter by ion chromatography is presented. The technique uses the eluant from the ion chromatography analysis stage to perform the extraction of the anions from the particulate matter. The demonstrated advantages of the new technique are manifold: faster sample throughput, minimised sample preparation, and a matrixed-matched sample for analysis. The repeatability of the technique has been tested using nominally identical ambient particulate matter samples (sub-sampled from one large filter) and the uncertainty of the technique has been estimated. The uncertainty estimate is transferable to other similar methods used to measure ions in particulate matter. Real data obtained using the new method are also presented.     

Analysis of inorganic mercury species associated with airborne particulate matter/aerosols: method development

This paper describes a method for speciation of Hg associated with airborne particulate matter. This method uses a mini-sampler for sample collection and analysis, thermal desorption for separating Hg species, and inductively coupled plasma mass spectrometry (ICP–MS) for identification and quantification of Hg. Coal fly ash spiked with different Hg compounds (e.g. Hg⁰, HgCl₂, HgO, and HgS) was used for qualitative calibration. A standard reference material with a certified value for Hg concentration was used to evaluate the method. When the temperature of the furnace was programmed at a linear rate of increase of 50° min^–1, different Hg compounds could clearly be separated. Three airborne particulate matter samples were collected in parallel in Toronto, ON, Canada and analyzed using this method. Reproducible results were obtained and Hg⁰, HgCl₂, HgO, and HgS species from these samples were detected.     

Critical review on the development of analytical techniques for the elemental analysis of airborne particulate matter

Among all environmental pollutants, particulate matter (PM) poses the major threat to our health. These tiny airborne particles vary in shape and composition, which is reflected in their hazardous potential. The particles are small enough to penetrate deep into the lungs and even enter the bloodstream, causing severe diseases. Therefore, their regular monitoring is required. Toxic metals and other elements are often measured by regulatory agencies as well as in research laboratories, either to compare ambient concentrations with prescribed limit values or to study provenance of air pollution sources in order to target PM pollution mitigation strategies. The most established method for the determination of regulated Pb, Cd, As, Ni and other elements in PM is microwave digestion inductively coupled plasma mass spectrometry (MW/ICPMS), whereas X-ray fluorescence (XRF) techniques have also often been used, especially in research. In this review paper we critically assess these two and three other analytical techniques (i.e., LA-ICPMS, PIXE and INAA) for element determination in PM deposited on filter media. All aspects from sample treatment to measurement range and limitations, costs and waste management are considered. In conclusion we identify XRF and LA-ICPMS as two promising surface techniques for the analysis of a PM deposit on a filter, which could replace the laborious wet MW/ICPMS method, which is – considering its wide use, very incriminating to the environment. In short, EDXRF is the cheapest, simplest for use and already customized for PM samples, whereas LA-ICPMS is promising, but still needs some development in the direction of autosamplers and matrix-matched standards for calibration.     

Multi-element analysis of airborne particulate matter by various spectrometric methods after microwave digestion

A microwave digestion procedure in combination of the measurement of various spectrometric methods including atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry was developed for the multi-element analysis of airborne particulate matter collected on PTFE filters by a dichotomous sampler. In order to achieve more sensitive and rapid multi-element analyses, special PTFE-lined digestion vessels were used. It was found that complete digestion of airborne particulates with an acid mixture of HNO₃-HClO₄-HF (3:7:1, v/v) can be achieved in the microwave-irradiated closed vessel system and direct spectroscopic measurement of the digested sample after appropriate dilution. A recovery study was conducted using a multi-element standard and NIST Standard Reference Material 1648 Urban Particulate. Sixteen major, minor, and trace elements in airborne particulate matter were determined.     

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.     

Capillary electrophoresis determinative and GC-MS confirmatory method for water-soluble organic acids in airborne particulate matter and vehicle emission

Urban fine airborne particulate matter (PM2.5) and vehicle emission samples were studied for water-soluble low-molecular-weight carboxylic acids using CE with indirect UV detection. Further identification of these acids was achieved using GC-MS as their butyl esters (after derivatization with BF3/butanol). Several dicarboxylic acids in the range C2-C10 including straight-chain, branched-chain, cis- and trans-unsaturated, and aromatic acids were confirmed by GC-MS. In addition, aromatic acids such as benzoate, phthalate, terephthalate, isophthalate, and 4-methylphtalate were present in such samples, but some of these were not well resolved by the used CE method. Oxocarboxylic acids (Cn(w) with n > 4) were also identified by GC-MS but not determined by CE due to lack of standards. The rapidity and simplicity of the CE method were clearly demonstrated, and the method was observed to be advantageous for routine monitoring of water-soluble organic acids in airborne PM2.5 and vehicle emission at low microg/L levels.     

A study of uniformity of elements deposition on glass fiber filters after collection of airborne particulate matter (PM-10), using a high-volume sampler

A study was conducted to evaluate the homogeneity of the distribution of metals and metalloids deposited on glass fiber filters collected using a high-volume sampler equipped with a PM-10 sampling head. The airborne particulate matter (APM)-loaded glass fiber filters (with an active surface of about 500 cm²) were weighed and then each filter was cut in five small discs of 6.5 cm of diameter. Each disk was mineralized by acid-assisted microwave (MW) digestion using a mixture of nitric, perchloric and hydrofluoric acids. Analysis was performed by axial view inductively coupled plasma optical emission spectrometry (ICP OES) and the elements considered were: Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Ti and V. The validation of the procedure was performed by the analysis of the standard reference material NIST 1648, urban particulate matter. As a way of comparing the possible variability in trace elements distribution in a particular filter, the mean concentration for each element over the five positions (discs) was calculated and each element concentration was normalized to this mean value. Scatter plots of the normalized concentrations were examined for all elements and all sub-samples. We considered that an element was homogeneously distributed if its normalized concentrations in the 45 sub-samples were within ±15% of the mean value ranging between 0.85 and 1.15. The study demonstrated that the 12 elements tested showed different distribution pattern. Aluminium, Cu and V showed the most homogeneous pattern while Cd and Ni exhibited the largest departures from the mean value in 13 out of the 45 discs analyzed. No preferential deposition was noticed in any sub-sample.     

Remarks on the detection of phenols in airborne particulate matter

Summary Samples of suspended particulate matter collected in Duisburg were investigated for phenolic compounds. The loaded filters were extracted with dichloromethane for 10 hours in a soxhlet apparatus. The concentrated extract was resolved in cyclohexane and separated into a non polar and a polar fraction on alumina. The polar fraction was taken up in dichloromethane and steam-distilled. The distillate was extracted with ether. After the evaporation of the ether, the residue was resolved in dichloromethane and allowed to react with benzoyl chloride. After adding toluene the solution was reduced in volume and analyzed in a GC-MS system. For the separation of phenols by means of HPLC the enrichment of the phenols was performed without benzoylization. Six phenols were detected: hydroxibenzene, methylhydroxibenzene, hydroxibiphenyl, hydroxifluorene, benzylhydroxibenzene and dihydroxibiphenyl.