A comparison of an optimised sequential extraction procedure and dilute acid leaching of elements in anoxic sediments, including the effects of oxidation on sediment metal partitioning

The effect of oxidation of anoxic sediment upon the extraction of 13 elements (Cd, Sn, Sb, Pb, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As) using the optimised Community Bureau of Reference of the European Commission (BCR) sequential extraction procedure and a dilute acid partial extraction procedure (4 h, 1 mol L⁻¹ HCl) was investigated. Elements commonly associated with the sulfidic phase, Cd, Cu, Pb, Zn and Fe exhibited the most significant changes under the BCR sequential extraction procedure. Cd, Cu, Zn, and to a lesser extent Pb, were redistributed into the weak acid extractable fraction upon oxidation of the anoxic sediment and Fe was redistributed into the reducible fraction as expected, but an increase was also observed in the residual Fe. For the HCl partial extraction, sediments with moderate acid volatile sulfide (AVS) levels (1-100 μmol g⁻¹) showed no significant difference in element partitioning following oxidation, whilst sediments containing high AVS levels (>100 μmol g⁻¹) were significantly different with elevated concentrations of Cu and Sn noted in the partial extract following oxidation of the sediment. Comparison of the labile metals released using the BCR sequential extraction procedure (ΣSteps 1-3) to labile metals extracted using the dilute HCl partial extraction showed that no method was consistently more aggressive than the other, with the HCl partial extraction extracting more Sn and Sb from the anoxic sediment than the BCR procedure, whilst the BCR procedure extracted more Cr, Co, Cu and As than the HCl extraction.     

Comparison of single and sequential extraction procedures for the study of rare earth elements remobilisation in different types of soils

With the continual increase in the utilisation of rare earth elements (REE) for industrial and agricultural purposes, research into the environmental and biogeochemical behaviour of REE had attracted much interest in recent times. This study principally describes the distribution of REE in four different types of soils like lateritic soil (S-1), in situ natural soil (S-2), soil contaminated by mining activity (S-3) and accidentally polluted soil (S-4) utilizing the optimised BCR sequential extraction procedure and partial extractions with various types of single extractants such as unbuffered salt solutions 0.1 M NaNO₃, 0.01 M CaCl₂, 1 M NH₄NO₃; complexing agents 0.005 M DTPA and 0.05 M EDTA; acid solutions 0.43 M CH₃COOH and 1 M HCl. Comparison of the sum of the four BCR fractions, which included an aqua regia attack on the residue, with the pseudo-total aqua regia digest values to assess the accuracy of the BCR partioning approach has been undertaken. Partial extraction results with several single extractants have also been reported for all the REE elements including yttrium which have been analysed by the optimised BCR procedure. Results obtained after 24 h extraction with each of the single extractant have also been discussed. The extraction with 1 M HCl during 24 h yielded similar quantities of REE as those released under the combined steps of 1, 2 and 3 of the BCR sequential extraction for all the four different type of soil samples indicating that this reagent can be used successfully to estimate the total extractable contents of REE in various types of soil samples.     

Distribution of heavy metals of agricultural soils of central Greece using the modified BCR sequential extraction method

The state of heavy metal (Cd, Cu, Ni, Zn, Pb, and Cr) pollution was studied, in 440 texturally different soil profiles in Thessaly, an intensely cultivated region in Central Greece. The study was carried out in 2004 and 2005 on 220 soil samples for each year. Soil samples were classified in three soil orders: Endisols, Alfisols, and Vertisols according to the Soil Taxonomy System. The pseudo-total concentrations of heavy metals were determined by the aqua regia procedure. Heavy metals were also determined after division into four fractions by sequential extraction with (a) acetic acid (exchangeable and specifically adsorbed metals), (b) a reducing agent (bound to Fe/Mn hydroxides), (c) an oxidizing agent (bound to soil organic matter), and (d) aqua regia (bound to mineral structures, residual). The concentrations of all the metals studied were higher in the topsoil (0–30?cm) and lower in the second soil layer (30–60?cm). Concentrations of 70–82% of Cd, 39–64% of Cu, 41–69% of Ni, 29–51% of Zn, 75–89% of Pb, and 52–87% of Cr were found in the first two fractions. Cd appeared to be the most mobile of the metals studied, while Cu and Zn were found in forms associated with soil organic matter. The chemical partitioning patterns of Pb and Cr indicated that these metals are largely associated with the Fe–Mn hydroxides, while Cr was also found in the residual fractions. Significant correlations between heavy metals fractions and soil physicochemical parameters were obtained and discussed.     

Investigation of heavy-metal uptake by vegetables growing in contaminated soils using the modified BCR sequential extraction method

The heavy metal (Cu, Fe, Co, Ni, Cd, Cr, Pb, Zn, and Mn) concentrations in soils and in vegetable samples, i.e. lettuce (Lactuca sativa L.), parsley (Petroselinum crispum), dill (Anethum graveolens), and onion (Allium cepa L.), taken from three urban vegetable gardens in Kayseri, Turkey, were determined by FAAS. The modified three-step sequential extraction procedure proposed by the European Bureau of References (BCR), now the Standards, Measurements and Testing Programme, was used in order to evaluate trace elements mobility in soil samples, and heavy-metal uptake by vegetables. Three operationally defined fractions were isolated using the BCR procedure: acid extractable (i.e. bound to carbonates), reducible (bound to Fe/Mn oxides), and oxidizable (bound to organic matter and sulphides). The vegetable samples were prepared to analysis using the wet-ashing procedure. To estimate the accuracy of the method used in analysis of the vegetable samples, the standard reference material (NIST SRM 1573a, Tomato leaves) was used. The results of recovery for all the elements were relatively satisfactory (87.7–108%). For the soil samples, the recovery values were calculated by proportioning the sum of the steps of the BCR procedure to those of the pseudototal digestion (i.e. aqua regia). In soils, the mobility of heavy metals followed the order Mn>Cd>Cu>Pb>Zn>Cr>Ni>Co>Fe. The relationship between the vegetable–metal and soil–extractable metal concentrations was examined in order to evaluate the bioavailability of metals, and the positive correlation, especially for the first (i.e. water, acid-soluble and exchangeable fraction) and for the third (i.e. oxidizable fraction) extraction steps, was obtained.     

Comparison of aqua regia and HNO3-H2O2 procedures for extraction of Tl and some other elements from soils

The relationship between aqua regia (ISO 11466) and HNO(3)-H(2)O(2) (ISO/CD 20279) extraction procedures for atomic emission spectrometric (ICP/OES and ICP/MS) determinations of Tl, P, Mn, Fe, Mg, Ca, Sr, Al, K, As, Bi, Zn, Pb, Co, Cd, Ni, V, Be, Cu and Cr was investigated. Soil samples (155) representing areas with different contents of the elements were selected for the comparison. Tl was the element of the highest interest and therefore the sampling sites were chosen to achieve as wide range of Tl contents as possible. Both extraction procedures are comparable in results (differences lower than 10% for the most of the elements) for all the tested elements. Statistically non-significant differences between the two extraction procedures were found for P, Zn, V and K (the slope was very close to 1 and the intercept included zero). Statistically significant values of intercepts were found for Fe, Al, Ca, Cd, Sr and Ni. Significantly higher results for aqua regia were found for Cu (12%), Pb (17%), Mn (11%) and lower results by aqua regia were found for Mg (4%), As (13%), Co (20%), Be (11%), Cr (4%) and Bi (6%). The results for Tl, the element of the highest interest, after HNO(3)-H(2)O(2) extraction procedure, were approximately 6% higher than the results after aqua regia extraction. Content of Tl in the soil samples was from 0.08 to 2.8 mg kg(-1). A highly significant linear relationship was found (R(2)=0.97).     

Assessment of a geochemical extraction procedure to determine the solid phase fractionation and bioaccessibility of potentially harmful elements in soils: A case study using the NIST 2710 reference soil

Three mineral acid sequential extraction regimes (HNO₃ only, HNO₃ followed by HCl and aqua regia) were applied to the NIST 2710 contaminated reference soil. The major and trace element chemical analysis data from the extractions were subjected to a chemometric self-modelling mixture resolution procedure which identified that 12 distinct physico-chemical components were extracted. The fractionation of As, Cd, Ni and Pb between these components were determined. Tentative assignments of the mineralogical sources of the components were made. The human ingestion bioaccessible fraction of As, Cd and Pb were determined using the in vitro BARGE UBM bioaccessibility test and were found to be 51.6%, 68.0% and 68.4% respectively. The relationship between the lability of the physico-chemical components and the bioaccessible fraction of the soils was investigated and the bioaccessible fractions were assigned to specific components. The extraction scheme using aqua regia was found to be the most suitable as it was the only one which extracted the iron sulphide phase in the soil.     

Determination of heavy metals (Pb, Cd, Cu, Zn, Cr) in sedimentary reference materials with IDMS: total concentration and aqua regia soluble portion

Summary The total concentration and the aqua regia soluble portion of traces of Pb, Cd, Cu, Zn, and Cr are determined with isotope dilution mass spectrometry (IDMS) in three different types of sediments using a thermal quadrupole instrument (THQ). The results are compared with those obtained by other methods during a certification project to establish these sediments (BCR 277, BCR 280, BCR 320) as standard reference materials. The IDMS (THQ) results are in good agreement with the preliminary certification values and the results of two other laboratories, which applied IDMS using magnetic sector field mass spectrometers. Significant differences between the different analytical methods were found for the total Pb concentration, which could be explained by adsorption and coprecipitation effects during the chemical pretreatment of samples. Using aqua regia instead of HF/HNO₃ for the decomposition of sediments, only 65%–95% of the total Pb and 60%–90% of the total Cr could be dissolved. On the other hand, only a small or negligible portion of Zn, Cd, and Cu could not be dissolved by aqua regia. The IDMS values for the aqua regia soluble Cr portion are significantly higher compared to the results of other methods. This can be explained by adsorption effects.

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Bestimmung von Schwermetallen (Pb, Cd, Cu, Zn, Cr) in sedimentären Standard-Referenzmaterialien mit massenspektrometrischer Isotopenverdünnungsanalyse: Totalgehalt sowie in Königswasser löslicher Anteil

     

Ultrasound-Assisted Extraction for the Evaluation of Element Mobility in Bottom Sediment Collected at Mining and Smelting Pb–Zn Ores Area in Poland

The current BCR procedure for metal fractionation recommended by the Standard Measurement and Testing Programme requires rather time-consuming sample pretreatment. Ultrasonic energy seems to be an attractive alternative for leaching metal from solid samples into a liquid extractant phase. This study aims at optimizing ultrasonic extraction in order to replace the BCR method of leaching using acetic acid and to apply the procedure of assessing element mobility in bottom sediment rich in moderately soluble carbonate minerals. The application of ICP-MS allowed the determination of As, Cd, Cr, Cu, Pb, Ni, Tl and Zn in extracts, in a wide range of concentration without any special treatment. Finally, 40’min extraction in an ultrasonic bath was proposed for evaluation of the mobile fraction of As, Cd, Cr, Cu, Pb and Zn as an assessment of environmental risk. The recovery of the ultrasound-assisted extraction in comparison to the shake-filter method, as applied in the common BCR procedure, was slightly higher than 100% for As, Cr and Pb, reasonably high (about 70%) for Cd, Zn and Cd, but did not exceed 21% for Tl. Also, the mobility and extractability (relative mobility) of the studied elements from sediment collected over one year were compares. According to the results obtained after 40’min of ultrasound-assisted extraction it can be concluded that mobility did not change over one year for Cr, Cu, As, Cd, Ni and Tl, but noticeable differences for Zn and Pb were observed. The total content of all studied elements was almost the same in samples taken in the years 2003 and 2004, respectively.     

Development of a wide bore flow through microwave digestion device for the determination of trace metals in soil

A flow through microwave digestion device has been developed for the determination of Cd, Cr, Mn, Ni and Pb in soil by aqua regia extraction. This device differs from existing commercially available devices as it uses a double pumping action to replace the back pressure regulator traditionally used to achieve internal pressurisation. An acid front has also been included to overcome problems associated with the dilution of acid in samples due to dispersion. Recoveries between 95 and 105% of certified values were achieved with standard deviations of less than 4% for certified reference soil (BCR 143R). A sample throughput of 6 samples per hour was achieved in the optimised system. The performance of the device was tested by digesting real soil samples ground through a 250 microns sieve and slurried without the use of surfactants. A comparison of analytical performance for analysing real samples was made between the microwave flow method and a thermal method.     

Relationship between vegetable metal and soil-extractable metal contents by the BCR sequential extraction procedure: chemometrical interpretation of the data

The contents of heavy metals in soil and vegetable samples collected from an urban garden in Kayseri, Turkey, were investigated. Both wet- and dry-ashing methods were used for dissolving vegetable samples. A sequential extraction procedure proposed by the Commission of the European Communities, Community Bureau of Reference (now superseded by the Standards, Measurement and Testing Programme, SM&T) was applied to the soil samples to extract the metals which are present in exchangeable and acid soluble (i.e. bound to carbonates), reducible (bound to Fe/Mn oxides), and oxidisable forms (bound to organic matter and sulphides) in the soil samples. Trace metals in the soil and vegetable samples were determined using flame atomic absorption spectrometry (FAAS). The total metal contents acquired by summing of metal levels in all the sequential extraction steps were compared with pseudo-total metal levels obtained with aqua regia for all the soil samples. The recovery values obtained by proportioning the results obtained by the BCR procedure to those of the pseudo-total digestion were found to be satisfactory. The limits of detection for the elements investigated were in the range of 0.04 to 0.59?µg?mL^?1 for all the extraction stages of the BCR procedure. Similarities among the variables were identified by correlation analysis, principal component analysis and hierarchical cluster analysis. The relationship between the vegetable metal and soil-extractable metal concentrations was examined in order to evaluate the bioavailability of metals.     

The role of different soil sample digestion methods on trace elements analysis: a comparison of ICP-MS and INAA measurement results

The measurement of trace-element concentration in soil, sediment and waste, is generally a combination of a digestion procedure for dissolution of elements and a subsequent measurement of the dissolved elements. “Partial” and “total” digestion methods can be used in environmental monitoring activities. To compare measurement results obtained by different methods, it is crucial to determine and to maintain control of the bias of the results obtained by these methods. In this paper, ICP-MS results obtained after matrix digestion with modified aqua regia (HCl+HNO₃+H₂O₂) method and two “total” digestion methods (microwave aqua regia+HF and HNO₃+HF) are compared with those obtained by instrumental neutron activation analysis, a non-destructive analytical method for the determination of the total mass concentrations of inorganic components in environmental matrices. The comparison was carried out on eight agricultural soil samples collected in one test area and measured by k₀-INAA and ICP-MS to determine As, Co, Cr, Sb and Zn mass concentration. The bias of results for As, Cd, Co, Cr, Cu, Ni, Pb, Sb and Zn of the three digestion methods were assessed using selected measurement standards. This paper highlights that the digestion procedure is an integral part of the measurement and can affect the measurement result in environmental analysis.     

Procedure for dissolving wolframite in order to determine trace elements by atomic absorption spectrometry

An analytical procedure for dissolving wolframite in order to determine trace elements by atomic absorption is reported. After decomposition of the mineral by alkaline fusion, the cooled flux is dissolved by heating with aqua regia. The finely crystalline precipitate of tungstite, which forms on standing, is filtered and dissolved by heating with aqua regia. Tungstite forms again in the latter solution and the filtration and solubilization are repeated until the solution contains negligible amounts of trace elements. Following this procedure, trace elements in 35 samples of natural wolframite have been dissolved and the solutions obtained have been analyzed by atomic absorption spectrometry for Fe, Mn, Cu, Zn, Pb, Co, Ni and Cd.     

Multi-elemental analysis of marine sediment reference material MESS-3: one-step microwave digestion and determination by high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS)

Single-step microwave digestion methods using four different acidic dissolving reagents were investigated with the main objective to obtain a simple, rapid method for multi-elemental analysis of marine sediment samples by high resolution inductively coupled plasma-mass spectrometry (HRICP-MS), especially for environmental studies. Closed-vessels microwave digestion procedures were carried out using the reagents as follows: HNO₃, mixture of HNO₃-HCl (φ _r = 9: 1), aqua regia, and mixture of HNO₃-HCl-HF (φ _r = 8: 1: 1). The elements analyzed were: Al, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Mo, Na, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, and Zn. Good recoveries were established for many of the metals analyzed even when only nitric acid was employed. However, for a good recovery of Sb and Tl, aqua regia should be employed.     

Study of partitioning and dynamics of metals in contaminated soil using modified four-step BCR sequential extraction procedure

The modified four-step BCR sequential extraction procedure (exchangeable and weak acid available species, reducible, oxidisable and residual fractions) was used to examine the distribution of As, Cd, Cr, Cu, Pb, and Zn with soil depth in an area (Baia Mare — Bozanta, Romania) with both high natural level of elements considered as toxic and historical pollution resulting from nonferrous metallurgy. The BCR approach proved a high metal input of anthropogenic origin down to 40 cm, while at lower depths the naturally elevated metal content must be considered. Results of the partitioning study and XRD analysis of solid matrix showed the greatest potential for chemical remobilisation of Cd, Zn, and Cu in weak acidic medium as well as their affinity for the oxidisable fraction (organic matter/sulphide). The tendency of Cr, Pb, and As to be immobilised as residual or reducible species on Fe-Mn oxides was evident. Although the partitioning of As in chemically inactive forms such as scorodite (FeAsO₄ · 2H₂O) soluble under reducible conditions and beudantite (PbFe₃(AsO₄)(SO₄)(OH)₂)), a residual species soluble in acid media, chemical mobilisation from soil in groundwater was confirmed. Dynamic processes of metal retention in soil under different conditions, namely acidic, reducing or oxidisable, were predicted from the Pearsonșs correlation analysis of element species with soil characteristics and components such as Fe, Mn, organic matter content, pH, and total element content, respectively. At the moment of the study, soil and groundwater in the area were found to be polluted with As, Cd, Cu, Pb and Zn. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.     

Oxidative extraction versus total decomposition of soil in the determination of thallium

An aqua regia extraction and a total decomposition of soil were compared in terms of thallium determination. A sequential extraction of soil, according to the BCR protocol, was also performed for additional information on thallium distribution in soil fractions. Certified reference material—soil GBW 07401 of Chinese origin, containing 1 ± 0.2 ppm of thallium was used in these experiments. Thallium was determined by flow injection-differential pulse-anodic stripping voltammetry (FI-DP-ASV). Only 35% of total thallium was extracted in the aqua regia extraction, while the total decomposition led to satisfactory recovery. The sequential extraction showed that only 5% of thallium in GBW 07401 is dissolvable in the four BCR procedure fractions, and that 95% of the element is entrapped in the residual parent matter. These results show that the aqua regia extraction does not ensure complete thallium extraction from soil. Surprisingly, the total decomposition is significantly less time consuming than the aqua regia extraction.     

Chemical characterization of PM10 fractions of urban aerosol

The goal of this investigation was to give an overview about the trace metal and total organic/inorganic carbon (TOC/TIC), water-soluble carbon (WSOC) and polyaromatic hydrocarbons (PAH) concentrations in the PM10 aerosol fraction in Budapest and to monitor monthly changes during the sampling period, whether there is a tendency in the seasonal change of the concentrations. The sampling took place in Budapest, Hungary between September 2004 and August 2007 in an area with high traffic density. For the sampling, a high-volume aerosol sampler equipped with a PM10 head was used. The samples were taken onto quartz fiber filters. Each month, one sample was collected. Sampling time was 96 h, the air intake was 30 m³/h, resulting in 2880 m³ sampled air volume.To measure the metal concentrations two types of sample preparation were used: microwave assisted aqua regia extraction and water extraction by sonication. In both cases, the solutions were analyzed by using a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS). The following 23 elements were investigated: V, Cd, Zn, Cu, Ni, Sb, Sn, Cr, Pt, Pb, Te, Tl, U, Mn, Fe, Co, Ga, Rb, Sr, Mo, Ag, Bi, Li. Comparing the data obtained from the aqua regia extraction to some other cities, the measured trace elements were found in moderate concentration. In the water extract, a significant part of zinc and thallium was found. During the sampling period, no proof of seasonal change in trace element concentrations was found. Trace metal and total organic/inorganic carbon concentrations in Budapest were similar to the concentration data measured in other cities with exception of Mn, Ga, Rb, Cd which are present in higher concentration in Budapest. The TOC content in the PM10 fraction amounted to 30-50%, and its value was the highest during the winter period due to the heating.The yearly average concentration of polyaromatic hydrocarbons was almost constant over the investigated period, but its seasonal change is more than one order of magnitude.     

Mobility of important toxic analytes in urban dust and simulated air filters determined by sequential extraction and GFAAS/ICP-OES methods

The modified BCR three-step sequential extraction procedure has been applied to homogenized urban dust samples and to simulated air filters loaded with the prepared urban dust via the wet deposition procedure. This work has been focused on comparative study of the distribution of trace elements in both samples and evaluation of the factors influencing the reliability of results with respect to the proposed extraction procedure. Extracted chemical fractions were analyzed by ICP-OES and GFAAS depending on the concentration levels of investigated trace elements As, Cd, Cr, Mn, Ni, and Pb, selected according to their adverse effect on the human health. Statistically evaluated results indicate significant differences between the extracted portions of analytes in urban dust and simulated air filters, where the mobility of some analytes in simulated air filters was higher than that in urban dust samples. The impact of surfactant Triton X-100 (0.05 vol. %) on the extraction procedure was also investigated. Presented at the XVIIIth Slovak Spectroscopic Conference, Spišská Nová Ves, 15–18 October 2006.     

The optimization of microwave digestion procedures and application to an evaluation of potentially toxic element contamination on a former industrial site

The optimization of a microwave dissolution procedure for potentially toxic elements in a contaminated soil sample has been evaluated using a central composite design approach. By considering the operating parameters of temperature, digestion time, microwave power and acid volume it was possible to identify the following optimum conditions: temperature, 160 °C; power, 750 W; digestion time, 25 min; and, an aqua regia volume of 13 mL. These microwave digestion conditions were then applied to 19 samples obtained from a former industrial site in Newcastle upon Tyne. Of the range of potentially toxic elements present at the site as a consequence of former industrial activity (As, Cd, Cr, Cu, Mo, Ni, Pb and Zn), the majority of topsoil samples indicated elevated concentrations of one or more of these elements. In particular, data obtained using either inductively coupled plasma mass spectrometry or flame atomic absorption spectroscopy indicates the high and wide concentration of Pb on the site (188-60300 mg/kg). Comparing the resulting potentially toxic elements data with UK soil guidelines values (SGVs) suggests at least parts of the site represent areas of potential human health risk. It was found that lead soil values exceeded the SGV on 17 out of the 19 sampling sites; similarly for As 6 out of 19 sampling sites exceeded the SGV. While for Cd, Cr and Ni the soil levels were below the stated SGVs.     

The utilization of modified BCR three-step sequential extraction procedure for the fractionation of Cd, Cr, Cu, Ni, Pb and Zn in soil reference materials of different origins

A modified three-step sequential extraction procedure for the fractionation of heavy metals, proposed by the Commission of the European Communities Bureau of Reference (BCR) has been applied to the Slovak reference materials of soils (soil orthic luvisols, soil rendzina and soil eutric cambisol), which represent pedologically different types of soils in Slovakia. Analyses were carried out by flame or electrothermal atomic absorption spectrometry (FAAS or ETAAS). The fractions extracted were: exchangeable (extraction step 1), reducible-iron/manganese oxides (extraction step 2), oxidizable-organic matter and sulfides (extraction step 3). The sum of the element contents in the three fractions plus aqua-regia extractable content of the residue was compared to the aqua-regia extractable content of the elements in the origin soils. The accuracy obtained by comparing the determined contents of the elements with certified values, using BCR CRM 701, certified for the extractable contents (mass fractions) of Cd, Cr, Cu, Ni, Pb and Zn in sediment following a modified BCR-three step sequential extraction procedure, was found to be satisfactory.     

Determination of trace elements in ambient aerosol samples

A microwave-assisted digestion procedure using HNO₃, HF, and H₂O₂ has been developed for analysis of elements in ambient particulate matter (PM). The samples are collected on cellulose filters and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS is calibrated with external standards, and recovery of analytes is tested with NIST SRM 1648 Urban Dust. This method has been used to quantify the airborne concentrations of a large number of elements, including Ag, As, Ba, Be, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sb, Sr, Ti, Tl, V, and Zn. For the majority of these elements, recovery of the NIST SRM is within 15% of the certified values.