Methodology for the determination of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF)

This article describes a methodology for the analysis of minor and trace elements in petroleum cokes by wavelength‐dispersive X‐ray fluorescence (WD‐XRF) spectrometry. The methodology was developed in order to have a rapid and reliable control method of these elements, because they determine coke end uses. There are a number of standard methods of chemical analysis by WD‐XRF or inductively coupled plasma atomic emission spectrometry (ICP‐OES) techniques. However, the standards that use WD‐XRF measurement give detection limits (L_D) above 10 mg·kg^?1 and only analyse a few elements of interest, whereas the ICP‐OES method requires extensive sample handling and long sample preparation times, with the ensuing errors. In order to improve the method described in the standard ASTM D6376 and reach the L_D and quantification limits (L_Q) required, the different stages of the process, ranging from sample preparation to measurement conditions: analytical line, detector, crystal, tube power, use of primary beam filters, and measurement time, were optimised. The samples were prepared in the form of pressed pellets, under conditions of high cleanliness of the mills, crushers, presses, and dies, and of the laboratory itself. The following reference materials were used in measurement calibration and validation: SRM 1632c, SRM 2718, SRM 2719, SRM 2685b, AR 2771, AR 2772, SARM 18, SARM 19, and CLB‐1. In addition, a series of materials were analysed by WD‐XRF and ICP‐OES, and the results were compared. The developed methodology, which uses WD‐XRF, is rapid and accurate, and very low L_D and measurement uncertainties were obtained for the following elements: Al, Ba, Ca, Cr, Cu, Fe, Ge, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, and Zn. Copyright © 2010 John Wiley & Sons, Ltd.     

Chemical analysis of argon–oxygen decarburization slags in stainless steelmaking process by X‐ray fluorescence spectrometry

A quantitative analysis method of fluorine in the slags produced in the stainless argon–oxygen decarburization (AOD) process by X‐ray spectrometry was proposed employing direct analysis technique by pressed pellet. This research investigated the separate quantification of calcium fluoride and calcium oxide contained in AOD slags. X‐ray diffraction measurement was performed to identify the stable phase of fluorine compound, which is primarily present in the slags. The synthetic standards prepared in laboratory were used to construct the X‐ray fluorescence (XRF) calibration curves for F, Ca_tO, SiO₂, MgO, Al₂O₃ and Cr₂O₃, considering the matrix effects and line overlap corrections (t: total). The calibration curves were tested by the quantitative analysis of synthetic standards with satisfactory precision and accuracy. The proposed method might be an alternative solution to the problem with the simple and routine chemical analyses of calcium fluoride in AOD slags of stainless steelmaking process by XRF spectrometry. Copyright © 2010 John Wiley & Sons, Ltd.     

Bead‐releasing agents used in the preparation of solid samples as beads for WD‐XRF measurement

This paper carries the results of an evaluation of various materials, which may be used to aid in the release of a fused bead from its mould during a wavelength‐dispersive x‐ray fluorescence (WD‐XRF) measurement. The following bead‐releasing agents were studied: NaI, LiBr, NH₄I, and LiI. Each was incorporated in different quantities, as a solid and/or in an aqueous solution, together with a flux, into samples of ceramic raw materials. Release agent interference in the WD‐XRF measurement was analysed, and the optimum quantity of release agent needed to obtain suitable beads for WD‐XRF measurement was determined. The best results were obtained for LiI, which yielded reproducible beads without significant interference in the WD‐XRF measurement when a relatively small quantity (0.11 LiI g/bead) was used. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative or semi‐quantitative?–laboratory‐based WD‐XRF versus portable ED‐XRF spectrometer: results obtained from measurements on nickel‐base alloys

‘Semi‐quantitative’ analytical procedures are becoming more and more popular. Using such procedures, the question of the accuracy of results arises. The accuracy of an analytical procedure depends to a great extent on spectral resolution, counting statistics and matrix correction. Two ‘semi‐quantitative’ procedures are compared with a quantitative analytical program. Using a laboratory‐based wavelength‐dispersive x‐ray fluorescence (WD‐XRF) spectrometer and a portable energy‐dispersive x‐ray fluorescence (ED‐XRF) spectrometer, 28 different nickel‐base alloy Certified Reference Materials (CRMs) were analyzed. Line interferences and inaccurate matrix correction are reasons for deviations from the reference value. As the comparison shows, ‘semi‐quantitative’ analyses on the WD‐XRF spectrometer can be accepted as quantitative determinations. The investigations show that the results obtained with the portable ED‐XRF spectrometer do not meet the quality requirements of laboratory analysis, but they are good enough for field investigations. Copyright © 2004 John Wiley & Sons, Ltd.     

Direct chemical characterisation of clay suspensions by WD‐XRF

This study was performed to develop a method for directly controlling the chemical composition of clay slurries used in preparing ceramic floor and wall tile bodies by wavelength‐dispersive X‐ray fluorescence (WD‐XRF) spectrometry, without the prior need to dry and prepare the samples as fused beads or pellets for WD‐XRF measurement, owing to the importance of knowing the suspension chemical composition in real time for appropriate control of the industrial process. The study was conducted on a wide range of ceramic floor and wall tile bodies, which are used to prepare different suspensions. The influence of suspension viscosity (from 300 to 7000 cp), of suspension solids content (between 66 and 69%), and of the type of body composition (floor or wall tile) on the WD‐XRF measurement was determined. In these viscosity and solid content ranges, no appreciable differences were observed in the WD‐XRF measurement results, indicating that the possibly arising variations in viscosity and solids content in such clay suspensions in industrial practice do not influence the WD‐XRF measurement. In contrast, the type of body composition did influence the WD‐XRF measurement. The developed method is rapid, reproducible, and accurate, which was verified by analysis of the materials using the customary method of WD‐XRF measurement on fused beads. In addition, this method is cheaper and more harmless to the environment; it minimises waste generation, since no sample preparation is required and the plastic sample holders can be reused, thanks to the reusable sample holder system designed at the Instituto de Tecnología Cerámica laboratories. Copyright © 2011 John Wiley & Sons, Ltd.     

The determination of elements in welding fume by X‐ray spectrometry and UniQuant

Welding is a hazardous process with an associated risk of health effects related to the fume arising from the core metal, flux components and welding surface. X‐ray fluorescence (XRF) is commonly used to determine elemental concentrations as part of occupational hygiene investigations using conventional calibrations. A method is proposed to determine elements in welding fume using XRF and a fundamental parameter software package known as UniQuant^®. This was found to remove the need for special dust standards being prepared as the calibration used was based on a series of standards supplied with UniQuant that would cover all sample types. A conventional calibration and UniQuant calibration were set up and elements found in welding fume were determined from tin to titanium. Samples obtained from the Health and Safety Laboratory Workplace Analysis Scheme for Proficiency (WASP) programme were also analysed by both methods for nickel, iron, manganese and chromium. For the normal calibration, average recovery results for the WASP samples were between 92 and 103% of the target value with relative standard deviations of 3‐7%. For the UniQuant calibration, average recovery results for the WASP samples were between 97 and 112% of the target value with relative standard deviations of 3‐10%. These results are well within analytical performance expectations for the type of welding fume matrix analysed. The method was applied to real welding fume samples collected from workplaces. Copyright © 2011 John Wiley & Sons, Ltd.     

Spectroscopic investigations on kidney stones using Fourier transform infrared and X‐ray fluorescence spectrometry

Kidney stone is the most painful and prevalent urological disorder of the urinary system throughout the world. Thus, analysis of kidney stones is an integral part in the evaluation of patents having stone disease. Spectroscopic investigations of stones provide an idea about the pathogenesis of stones for its better cure and treatment. Hence, the present work targets multispectroscopic investigations on kidney stones using Fourier transform infrared (FTIR) and wave dispersive X‐ray fluorescence (WD‐XRF) spectroscopy which are the most useful analytical methods for the purpose of bio‐medical diagnostics. In the present study, FTIR spectral method is used to investigate the chemical composition and classification of kidney stones. The multicomponents of kidney stones such as calcium oxalate, hydroxyl apatite, phosphates, carbonates, and struvite were investigated and studied. Qualitative and quantitative determination of major and trace elements present in the kidney stones was performed employing WD‐XRF spectroscopy. The wide range of elements determined in the kidney stones were calcium (Ca), magnesium (Mg), phosphorous (P), sodium (Na), potassium (K), chlorine (Cl), sulfur (S), silicon (Si), iodine (I), titanium (Ti), iron (Fe), ruthenium (Ru), zinc (Zn), aluminum (Al), strontium (Sr), nickel (Ni), copper (Cu), and bromine (Br). For the first time, ruthenium was detected in kidney stone samples employing WD‐XRF in very low concentration. Our results revealed that the presence and relative concentrations of trace elements in different kinds of stones are different and depend on the stone types. From the experiments carried out on kidney stones for trace elemental detection, it was found that WD‐XRF is a robust analytical tool that can be useful for the diagnosis of urological disorders. We have also compared our findings with the results reported using XRF technique. The results obtained in the present paper show interesting prospects for FTIR and WD‐XRF spectrometry in nephrolithiasis. Copyright © 2017 John Wiley & Sons, Ltd.     

ED‐XRF set‐up for size‐segregated aerosol samples analysis

The knowledge of size‐segregated elemental concentrations in atmospheric particulate matter (PM) gives a useful contribution to the complete chemical characterisation; this information can be obtained by sampling with multi‐stage cascade impactors. In this work, samples were collected using a low‐pressure 12‐stage Small Deposit Impactor and a 13‐stage rotating Micro Orifice Uniform Deposit Impactor^?. Both impactors collect the aerosol in an inhomogeneous geometry, which needs a special set‐up for X‐ray analysis. This work aims at setting up an energy dispersive X‐ray fluorescence (ED‐XRF) spectrometer to analyse quantitatively size‐segregated samples obtained by these impactors. The analysis of cascade impactor samples by ED‐XRF is not customary; therefore, as additional consistency test some samples were analysed also by particle‐induced X‐ray emission (PIXE), which is more frequently applied to size‐segregated samples characterised by small PM quantities. A very good agreement between ED‐XRF and PIXE results was obtained for all the detected elements in samples collected with both impactors. The good inter‐comparability proves that our methodology is reliable for analysing size‐segregated samples by ED‐XRF technique. The advantage of this approach is that ED‐XRF is cheaper, easier to use, and more widespread than PIXE, thus promoting an intensive use of multi‐stage impactors. Copyright © 2011 John Wiley & Sons, Ltd.     

Characterization of Indian Ayurvedic herbal medicines for their metal concentrations using WD‐XRF spectrometry

This article describes the details of metal concentrations evaluated using wavelength dispersive X‐ray fluorescence (WD‐XRF) spectrometry. A total of 22 elements, Na, Mg, Al, Si, P, S, K, Ti, Ca, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Hg, Pb, Ba, Au, and Sn from 16 Ayurvedic medicines were characterized. The method was validated by analyzing the six certified reference materials of soil standards [NIST SRM‐2710, CRM 027‐050 (US‐EPA certified), PS‐1, TILL‐1 and TILL‐4 (Canadian certified reference material, CCRMP) and JSO‐1 (Japanese certified reference material)]. The elemental concentrations in all the standards are found to be within ± 10% of the reported values. Crystalline phases in the individual drug samples were explained by powder X‐ray diffraction (XRD) technique. Qualitative phase identification was done using the ICDD database. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of Mg and Ti in Ziegler–Natta catalysts by x‐ray fluorescence spectrometry

The metal content in Ziegler–Natta catalysts based on Ti and Mg derivatives could not be determined directly by x‐ray fluorescence (XRF) spectrometry owing to the instability of the catalyst. The samples were then calcined and the resultant Mg and Ti oxides were characterized by x‐ray diffraction (XRD). A series of synthetic standards were prepared with high‐purity MgO and TiO₂, since there were no available certified standards for the catalysts. Samples and standards were compressed with high‐purity H₃BO₃ flux. This protocol was shown to be reproducible, having a correlation coefficient of 0.9999. The metal contents determined by XRF were in accordance with those obtained by a complexometric titration (Mg) and a UV–visible spectrophotometric method (Ti). Copyright © 2004 John Wiley & Sons, Ltd.     

The comparative analytical performance of the Beagle 2 X‐ray Spectrometer for in situ geochemical analysis on Mars

The Beagle 2 X‐ray Spectrometer (B2 XRS) instrument was part of the Beagle 2 Mars lander payload and intended to perform in situ geochemical analyses of geological materials on Mars. The analytical performance of a spare version of the B2 XRS was compared with (1) a portable X‐ray fluorescence (PXRF) spectrometer designed to perform terrestrial fieldwork and (2) a laboratory‐based wavelength‐dispersive (WD‐XRF) system used to produce high quality geochemical data. The criteria used to assess the performance were based on fitting precision, accuracy and detection limit, determined from the analysis of international geochemical reference materials. The fitting precision of the B2 XRS and PXRF was found to be in agreement with the Horwitz function (a benchmark relating the analysed concentration of an analyte to its uncertainty) over 4 orders of magnitude of concentration range from 10^?1 to 10^?5 g/g. The PXRF generally had a better fitting precision than the B2 XRS because of its better resolution. In order of improving accuracy, the spectrometers generally are ranked B2 XRS, PXRF and WD‐XRF for various major and trace elements. A limiting factor in the accuracy of the B2 XRS was the application of the algorithm used for its quantitative analysis. The detection limits for the spectrometers ranked in the same order as the accuracy as a result of improving signal‐to‐noise ratio (SNR) of elemental peaks, which is a direct consequence of improving resolution between these spectrometers. Overall, the B2 XRS was found to have a favourable analytical performance compared to the benchmark spectrometers, despite having met considerable design constraints and qualification tests as a planetary instrument. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of arsenic‐containing white rice grains as calibration standards for X‐ray fluorescence analysis of total arsenic in cereals

A preparation method of arsenic‐containing white rice grains as calibration standards was developed for the X‐ray fluorescence (XRF) analysis of arsenic in rice grains. Calibration standards were prepared by adding 10 g of white rice grains (from Japan) to 100 ml methanol‐containing dimethylarsinic acid corresponding to 2–100 µg arsenic. The mixture was heated, dried at 150 °C, cooled to room temperature, and then stored in a silica gel desiccator. A total of 5.0 g of each calibration standard was packed into a polyethylene cup (32 mm internal diameter and 23 mm height) covered with a 6‐µm‐thick polypropylene film and then analyzed by wavelength‐dispersive XRF spectrometry. The calibration curve for arsenic obtained from the white rice grains containing arsenic showed good linearity over a concentration range of 0.21–5.00 mg kg^?1 arsenic. The limit of detection of arsenic was 0.080 mg kg^?1. To check the reliability of the XRF method, the concentrations of arsenic in six samples of grain cereals and two samples of flour were compared with those obtained by atomic absorption spectrometry after acid decomposition. The values obtained by both analytical methods showed good agreement. Copyright © 2016 John Wiley & Sons, Ltd.     

Chemical composition and mass closure for PM10 aerosols during the 2005 dry season at a rural site in Morogoro,Tanzania

An intensive aerosol field campaign was carried out from 11 July to 11 August 2005 (dry season) at a rural site in Morogoro, Tanzania. The objectives were to determine the chemical composition of the atmospheric particulate matter (PM) and to examine to which extent the gravimetric PM mass can be explained by the measured aerosol components. Two low‐volume filter samplers were deployed, a PM₁₀ filter holder with two Whatman QM‐A quartz fibre filters in series and a Gent PM₁₀ stacked filter unit (SFU) sampler with coarse and fine Nuclepore polycarbonate filters. The samplers operated in parallel and a total of 51 parallel collections were made. All samples were analysed for the PM mass by weighing. Depending on the sampler type and/or collection substrate, further analyses were performed for 25 elements by particle‐induced x‐ray emission spectrometry, for major water‐soluble inorganic ions by ion chromatography, and for organic carbon and elemental carbon by a thermal—optical transmission technique. The PM₁₀ mass, as derived from the SFU samples, was, on an average, 46 ± 12 µg/m³. Aerosol chemical mass closure calculations were made for this PM₁₀ mass; eight aerosol components were considered and they explained 93% of the average PM₁₀ mass. Organic matter (OM) and crustal matter were the dominant aerosol components; they accounted for, on an average, 44% and 33%, respectively, of the PM₁₀ aerosol. The large contribution from OM is thought to originate mainly from the burning of biomass, especially of charcoal and agricultural residues. Copyright © 2009 John Wiley & Sons, Ltd.     

Optical In Situ Size and Concentration Measurement of Particles Dispersed in Gases at Temperatures up to 1000°C

Based on previous experience, an optical particle counter has been designed which allows the direct measurement of the size and concentration of dust particles in gas flows at high temperatures. The instrument features a new optical measuring volume definition together with a signal control to avoid border‐zone error effects. The instrument has a free working distance of 200 mm. Hence it is possible to make true in situ measurements in pipe flows with a cross‐section of ca. 60 cm² and additionally to protect the device against heat and dust precipitation on the optical windows. The instrument was initially used to examine the separation behaviour of cake‐forming rigid ceramic barrier filters at temperatures up to 1000 °C. In particular, the fractional efficiencies and the time‐related concentration changes on the clean gas side caused by a pulse jet cleaning event could be determined. The results obtained so far demonstrate that ceramic barrier filters show basically the same behaviour as conventional filters, but possess a substantially higher separation efficiency at a corresponding higher pressure drop (fractional penetration values between 10⁻⁵ and 10⁻⁹ depending on the type of filter material and the cake formation).     

Identification of aerosol particle sources in semi‐rural area of Kwabenya,near Accra,Ghana, by EDXRF techniques

Small aerosol particles have for a long time been known to be harmful to humans, and are today regarded to cause a larger number of deaths than traffic accidents globally. Energy dispersive x‐ray fluorescence (EDXRF) is a well known method that has been used for identification of toxic as well as non‐toxic elements in the particles. The combination of elements will together with other information help to identify the sources and predict the effects of particles on environment and human health. The present work was conducted in Kwabenya, a suburb of the capital Accra of Ghana, which is frequently exposed to Harmattan dust from the Sahara–Sahel region. In total 171 filters each of PM2.5 and PM(2.5–10) were collected during 1 year. Levels of elements, black carbon (BC) and mass, were determined for both particle sizes. Principal component analysis (PCA) was performed on the datasets from Harmattan and non‐Harmattan periods. The daily average of PM10 was very high, 179 µg m^?3 and the BC contents were 4 µg m^?3. The presence of crustal elements was large in PM(2.5–10) as well as in PM2.5, and had a more than tenfold increase in PM(2.5–10) during the Harmattan period. Major characteristic elements for different sources were identified from correlation coefficients and regression analysis of the data. Sahara sand aerosol was the major source in both study periods, but influence from biomass burning, sea‐spray and metal industries was also observed. Copyright © 2009 John Wiley & Sons, Ltd.     

Accurate standard‐based quantification of X‐ray fluorescence data using metal‐contaminated plant tissue

Quantitative X‐ray fluorescence (XRF) measurements have been conducted on naturally lead‐contaminated samples. The calibration procedure using the ratio of fluorescence to Compton scattered radiation was investigated using Monte Carlo simulation. Experimental results with low‐energy photons (14 keV) and simulations show a very good linearity of the fluorescence to Compton ratio as a function of metal concentration. Lead (Pb), iron (Fe) and zinc (Zn) are measured in samples of Phaseolus vulgaris (bean seeds) that have been grown using a nutritive solution with different Pb dopings. Naturally contaminated samples are thus obtained. The calibration must be done for fixed conditions of X‐ray energy and scattering angle, while X‐ray beam intensity and detector to sample distance can change from one sample to another. Simulation allows to evaluate the matrix effect on the calibration curve, and shows that linearity is preserved even in the presence of other heavy elements in the fluorescence spectrum. However, calibration must be done using samples with similar matrix as it affects the slope of the curve. Copyright © 2010 John Wiley & Sons, Ltd.     

Improvement of spatial resolution of µ‐XRF by using a thin metal filter

An improvement of spatial resolution of µ‐XRF by using a thin metal filter was investigated. The size of the x‐ray beam focused by the polycapillary x‐ray lens depended on the energy of the characteristic x‐rays. Original spot sizes at the focal point were 48 µm for CrKα, 41 µm for NiKα, and 28 µm for MoKα, respectively. To make the x‐ray beam size small, Ti? Cu thin foil was placed between the output of the lens and the focal point as a metal filter to reduce the continuous x‐rays. Finally, the x‐ray microbeam size was improved to 30 µm by applying a filter. Clear 2D mapping images of Cr, Fe, and Ni in 300‐mesh stainless steel could be obtained by applying this filter. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of sulfur reference materials that reproduce atmospheric particulate matter sample characteristics for XRF calibration

Energy‐dispersive X‐ray fluorescence (XRF) is an important tool used in routine elemental analysis of atmospheric particulate matter (PM) samples collected on polytetrafluoroethylene (PTFE) membrane filters. The method requires calibration against thin‐film standards of known elemental masses commonly obtained from commercial suppliers. These standards serve as a convenient and widely accepted interlaboratory reference but can differ significantly from samples in their chemical composition, substrate, and geometry. These differences can introduce uncertainties regarding the absolute accuracy of the calibration for atmospheric samples. Continuous elemental records of the US Interagency Monitoring of Protected Visual Environments (IMPROVE) PM monitoring network extend back to 1988. Evaluation of long‐term concentration trends and comparison with other networks demand a calibration that is accurate and precise compared with the uncertainty of the XRF measurement itself. We describe a method to prepare sulfur reference materials that are optimized for calibration of XRF instruments used to analyze IMPROVE PM samples. The reference materials are prepared by using the atmospheric form of the element, by reproducing the sample geometry, and by using the same substrate as in samples. Our results show that stable, pure, anhydrous, and stoichiometric deposits are collected onto the filter substrates, and furthermore, that the reference material masses are accurate and have acceptable uncertainty in the measurement range. The XRF response of the sulfur reference materials is similar to other commercial standards and is linear in the measurement range, and the slope of the multipoint calibration curve has very low uncertainty. These reference materials are valid for the calibration of XRF systems, and they bring improved transparency and credibility to the IMPROVE calibration. Copyright © 2013 John Wiley & Sons, Ltd.     

GE‐MXRF analysis of multilayer films

Polycapillary x‐ray optics (capillary x‐ray lens) is now popular in x‐ray fluorescence (XRF) analysis. Such an x‐ray lens can collect x‐rays emitted from an x‐ray source in a large solid angle and form a very intense x‐ray microbeam which is very convenient for micro x‐ray fluorescence (MXRF) analysis. In this paper, a new method called grazing exit micro x‐ray fluorescence analysis (GE‐MXRF), which combines an x‐ray lens used to form an intense XRF source was developed and applied in multilayer film analysis. Such a method can give the information of film composition, density, and thickness. Through two‐dimensional scan of the film sample, the information of film uniformity can be acquired; meanwhile, this method is also useful in adjusting experiment condition during the film preparation with metal vapor vacuum arc (MEVVA) source ion implantation. Copyright © 2008 John Wiley & Sons, Ltd.     

Levels and sources of heavy metal contamination in road dust in selected major highways of Accra,Ghana

Environmental studies have revealed significant contributions of vehicular exhaust emissions to high pollution levels in urban dwellings. The levels and sources of heavy metal contaminations of some major roads in Accra have been investigated in this work. Street dust samples collected from four major roads in Accra (Mallam Junction‐Weija road, John Teye‐Pokuase road, Tema Motorway and Tetteh Quarshie Interchange in Accra) were analysed for their elemental concentrations using energy‐dispersive X‐ray fluorescence. Twenty elements were identified: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr and Pb. Significant concentration levels were obtained for K, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Br, Rb, Sr, Y, Zr and Pb in all the samples and were used for the source identification. Enrichment factors and principal component analysis were used to verify the anthropogenic contribution to road dust. Results obtained for the enrichment factors showed moderate enrichment for V, Cr and Cu, while Zn, Br, Zr and Pb were significantly enriched. Principal component analysis identified four sources and their contributions to the elemental contents in the road dust. Natural crust, brake wear, tyre wear and vehicle exhaust emission were the four sources identified. The contribution of vehicular non‐exhaust emissions to heavy metal contamination in the road dust was found to be greater than that of exhaust emissions. Copyright © 2012 John Wiley & Sons, Ltd.