Determination of metals, metalloids and non-volatile ions in airborne particulate matter by a new two-step sequential leaching procedure Part A: Experimental design and optimisation

The optimisation of a micro-analytical two-step sequential leaching procedure for the determination of non-volatile ions (NO₃⁻, SO₄²⁻, Cl⁻, Na⁺, Mg²⁺, NH₄⁺ and Ca²⁺) and of 17 elements (Al, As, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, S, Se, V, Zn, Sb, Si and Ti) in two fractions—extract and residue—on the same sample of air particulate matter is described. The two-step method was tested on the SRM NIST 1648 for equivalence with two reference methods, the EMEP procedure for ions extraction and the EN 12341 standard for the elemental determination of the PM₁₀ and is suitable for application to small sample amounts (less than 1 mg of particulate matter is needed), i.e. those collected by daily low volume filter-sampling. Performance times of the procedure were optimised to meet the target of routine application for large scale monitoring samples. A single ultrasonic-assisted extraction of air particulate matter is performed in 0.01 M acetate buffer at pH 4.5, followed by IC ions analysis and ICP-OES elemental analysis of the extract and by ICP-OES elemental analysis of the mineralized residue after dissolution by microwave-assisted digestion with a HNO₃/H₂O₂ mixture. Using a pH buffered extracting solvent was preferred to water or diluted acid solutions to improve the reproducibility of metals extraction with respect to existing leaching methods; the influence of pH, nature and concentration of the buffer solution and extraction time on analytes concentration in the extract is discussed. Values of ions extraction and elements recoveries resulted fairly equivalent with those obtained by the reference methods. The study was also extended to some non-certified elements (Mg, S, Sb, Si and Ti) for their environmental significance. Elements recoveries were obtained as sum of the extract and residue fractions and were comparable with those obtained by direct dissolution. Standard deviations were within 10% for almost all detected ions and elements.     

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).     

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.     

Determination of soluble ions and elements in ambient air suspended particulate matter: Inter-technique comparison of XRF, IC and ICP for sample-by-sample quality control

In this paper, we describe a validation procedure for chemical fractionation analysis of elements (Al, As, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, S, Sb, Si, Sr, Ti and V) and soluble ions (Cl⁻, NO₃⁻, SO₄²⁻, Na⁺, NH₄⁺, Mg²⁺, Ca²⁺) in suspended particulate matter (PM). The procedure applies three distinct measurement techniques (XRF, IC and ICP-OES) to the analysis of individual samples. The techniques used generate different outputs at different stages in the procedure. This makes it possible to identify the contributions of specific parameters to measurement uncertainty. On this basis, we propose a scheme for controlling the analytical quality of data from individual samples in which inter-technique comparisons is used in the same way many analytical methods use surrogates. We apply this scheme to about 310 samples of PM₁₀ and PM_2.5 identifying and assessing the main factors contributing to measurement uncertainty. This procedure successfully resolved a number of difficulties frequently encountered during the analysis of PM, including lack of appropriate reference materials and the low reliability of alternative techniques of quality control. The results demonstrate the critical importance of sample treatment prior to destructive analysis by IC and ICP.