Particle Induced X-ray Emission Data Research Articles

Dependence of precipitation of trace elements on pH in standard water

Abstract The present work aimed to study the dependence of precipitation of trace elements on the pH of solution. A standard solution was prepared by using ultrapure deionized water (18.2 MΩ/cm) as the solvent and 11 water-soluble salts having different elements as solutes. Five samples of different pH values (2 acidic, 2 basic, and 1 neutral) were prepared from this standard solution. Sodium-diethyldithiocarbamate was used as the chelating agent to precipitate the metal ions present in these samples of different pH values. The targets were prepared by collecting these precipitates on mixed cellulose esters filter of 0.4 μm pore size by vacuum filtration. Elemental analysis of these targets was performed by particle-induced X-ray emission (PIXE) using 2.7 MeV protons from the single Dee variable energy cyclotron at Panjab University, Chandigarh, India. PIXE data were analyzed using GUPIXWIN software. For most of the elements, except Hg with oxidation state +2, such as Co, Ni, Zn, Ba, and Cd, a general trend of enhancement in precipitation was observed with the increase in pH. However, for other elements such as V, As, Mo, Ag, and Bi, which have oxidation state other than +2, no definite pattern was observed. Precipitation of Ba and As using this method was negligible at all five pH values. From these results, it can be concluded that the precipitation and recovery of elements depend strongly on the pH of the water sample.

On the autarchic use of solely PIXE data in particulate matter source apportionment studies by receptor modeling

Particle Induced X-ray Emission (PIXE) analysis of aerosol samples allows simultaneous detection of several elements, including important tracers of many particulate matter sources. This capability, together with the possibility of analyzing a high number of samples in very short times, makes PIXE a very effective tool for source apportionment studies by receptor modeling. However, important aerosol components, like nitrates, OC and EC, cannot be assessed by PIXE: this limitation may strongly compromise the results of a source apportionment study if based on PIXE data alone. In this work, an experimental dataset characterised by an extended chemical speciation (elements, EC–OC, ions) is used to test the effect of reducing input species in the application of one of the most widely used receptor model, namely Positive Matrix Factorization (PMF). The main effect of using only PIXE data is that the secondary nitrate source is not identified and the contribution of biomass burning is overestimated, probably due to the similar seasonal pattern of these two sources.

In-depth elemental characterization of Cu(In,Ga)Se2 thin film solar cells by means of RBS and PIXE techniques

Thin films based on Cu(In,Ga)Se2 are used as absorber cells in photovoltaic devices. In and Ga graded depth profiles are designed to optimize the solar cell performance. Simultaneous Rutherford Backscattering Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE) with 3MeV 4He ions were used in conjunction to determine the depth profile of all the heavy elements in Cu(In,Ga)Se2 absorbers and complete solar cells. The RBS and PIXE data from one sample were analyzed synergistically, providing reliable depth profiles that satisfy all the data collected. An uncertainty analysis was done, probing the sensitivity of the analysis to different assumptions. The analytical possibilities of the combined RBS/PIXE alpha beam measurements of the CIGSe thin film solar cells, as well as the uncertainties induced in the quantitative methodology are discussed and critically assessed.

Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements

Abstract. This study aims to determine the mineral contribution to PM10 in the central Mediterranean Sea, based on 7 yr of daily PM10 samplings made on the island of Lampedusa (35.5° N, 12.6° E). The chemical composition of the PM10 samples was determined by ion chromatography for the main ions, and, on selected samples, by particle-induced X-ray emission (PIXE) for the total content of crustal markers. Aerosol optical depth measurements were carried out in parallel to the PM10 sampling. The average PM10 concentration at Lampedusa over the period June 2004–December 2010 is 31.5 μg m−3, with low interannual variability. The annual means are below the EU annual standard for PM10, but 9.9% of the total number of daily data exceeds the daily threshold value established by the European Commission for PM (50 μg m−3, European Community, EC/30/1999). The Saharan dust contribution to PM10 was derived by calculating the contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides in samples in which PIXE data were available. Cases in which crustal content exceeded the 75th percentile of the crustal oxide content distribution were identified as elevated dust events. Using this threshold, we obtained 175 events. Fifty-five elevated dust events (31.6%) displayed PM10 higher than 50 μg m−3, with dust contributing by 33% on average. The crustal contribution to PM10 has an annual average value of 5.42 μg m−3, and reaches a value as high as 67.9 μg m−3 (corresponding to 49% of PM10) during an intense Saharan dust event. The crustal content estimated from a single tracer, such as Al or Ca, is in good agreement with the one calculated as the sum of the metal oxides. Conversely, larger crustal contents are derived by applying the EU guidelines for demonstration and subtraction of exceedances in PM10 levels due to high background of natural aerosol. The crustal aerosol amount and contribution to PM10 showed a very small seasonal dependence; conversely, the dust columnar burden displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm up to 0.28 in June–August). We found that 71.3% of the dust events identified from optical properties over the atmospheric column display a high dust content at the ground level. Conversely, the remaining 28.7% of cases present a negligible or small impact on the surface aerosol composition due to the transport processes over the Mediterranean Sea, where dust frequently travels above the marine boundary layer, especially in summer. Based on backward trajectories, two regions, one in Algeria–Tunisia, and one in Libya, are identified as main source areas for intense dust episodes occurring mainly in autumn and winter. Data on the bulk composition of mineral aerosol arising from these two source areas are scarce; results on characteristic ratios between elements show somewhat higher values of Ca / Al and (Ca + Mg) / Fe (2.5 ± 1.0, and 4.7 ± 2.0, respectively) for Algeria–Tunisia than for Libyan origin (Ca / Al = 1.9 ± 0.7 and (Ca + Mg) / Fe = 3.3 ± 1.1).

Accurate Determination of Quantity of Material in Thin Films by Rutherford Backscattering Spectrometry

Ion beam analysis (IBA) is a cluster of techniques including Rutherford and non-Rutherford backscattering spectrometry and particle-induced X-ray emission (PIXE). Recently, the ability to treat multiple IBA techniques (including PIXE) self-consistently has been demonstrated. The utility of IBA for accurately depth profiling thin films is critically reviewed. As an important example of IBA, three laboratories have independently measured a silicon sample implanted with a fluence of nominally 5 × 10(15) As/cm(2) at an unprecedented absolute accuracy. Using 1.5 MeV (4)He(+) Rutherford backscattering spectrometry (RBS), each lab has demonstrated a combined standard uncertainty around 1% (coverage factor k = 1) traceable to an Sb-implanted certified reference material through the silicon electronic stopping power. The uncertainty budget shows that this accuracy is dominated by the knowledge of the electronic stopping, but that special care must also be taken to accurately determine the electronic gain of the detection system and other parameters. This RBS method is quite general and can be used routinely to accurately validate ion implanter charge collection systems, to certify SIMS standards, and for other applications. The generality of application of such methods in IBA is emphasized: if RBS and PIXE data are analysed self-consistently then the resulting depth profile inherits the accuracy and depth resolution of RBS and the sensitivity and elemental discrimination of PIXE.

PIXE and IRR analysis of sixteenth-century ink drawings by Luca Cambiaso and his school

Non-invasive and non-contact analyses were performed on a group of 28 ink drawings ascribed to the sixteenth-century Italian painter Luca Cambiaso and his followers. Drawings analysed in this investigation were selected from the collections of Musei di Strada Nuova in Genoa and of Museo del Prado in Madrid. Particle-induced X-ray emission (PIXE), carried out at the Centro de Micro-Análisis de Materiales of the Universidad Autónoma de Madrid and at the Università di Firenze, provided elemental data on the inks and papers. The drawings in Genoa were studied at the Università di Genova using infrared relectography (IRR) and optical microscopy. Elemental composition of the inks was determined by comparison with a set of certified thin standards. Elemental analysis indicates that all of the drawings were executed with iron gall ink, except for one case where a mixed carbon black and iron gall ink was used. The PIXE data showed variations in the elemental concentrations of the materials used in the various inks, indicating the use of different recipes in their production. In some cases, these differences may help corroborate stylistic judgements to confirm or deny Cambiaso's authorship and separate autograph drawings from those of his pupils or imitators. PIXE analysis was also used to distinguish the presence of retouches and later additions. In some drawings, the combined use of IRR and optical microscopy revealed the presence of a dry carbon-based underdrawing, following a working method that seems more consistent with a workshop procedure than with the drawing technique of the master himself.

Chemical composition, impact from biomass burning, and mass closure for PM2.5 and PM10 aerosols at Hyytiälä, Finland, in summer 2007

AbstractA comprehensive chemical aerosol characterisation was carried out at the forested site of Hyytiälä, Finland, from 2 to 30 August 2007. PM2.5 and PM10 Nuclepore polycarbonate and quartz fibre filter samples were taken in parallel, typically for separate day‐time and night‐time periods. All samples were analysed for the particulate mass by weighing. The Nuclepore filters were analysed for over 20 elements by particle‐induced X‐ray emission (PIXE) spectrometry and for major anions and cations by ion chromatography. The quartz fibre filters were analysed for organic and elemental carbon by a thermal‐optical transmission technique. A number of samples exhibited high K, Zn, and oxalate levels, indicating an impact from biomass burning. A noteworthy episode occurred on 12‐13 August, when air masses were advected from the southern part of European Russia where extensive biomass burning had occurred. In the aerosol chemical mass closure calculations, eight aerosol types were considered. Organic matter (OM) contributed by far the most to the PM2.5 and PM10 mass; it accounted for about 70% of the average PM2.5 and PM10 mass and 48% of the coarse (PM10–2.5) aerosol. Crustal matter, deduced from the PIXE data, provided a rather small contribution; only 3% in PM2.5, 13% in PM10, and 32% in the coarse aerosol. The mean PM2.5 and PM10 mass concentrations and their attribution to the eight aerosol types for the 2007 campaign at Hyytiälä were similar to those for the cold period of a 2006 summer campaign at the forested site of K‐puszta, Hungary. OM was more important and nitrate was clearly less important at Hyytiälä, though. Copyright © 2011 John Wiley & Sons, Ltd.

SEM-EDS characterization of western Mediterranean obsidians and the Neolithic site of A Fuata (Corsica)

During the Neolithic, obsidians of the Monte Arci (Sardinia) volcanic complex were by far more used in the northern Tyrrhenian area than those of the three other source-islands (Lipari, Palmarola, Pantelleria) in the western Mediterranean. It is shown that merely determinations of content for six major elements with a scanning electron microscope by energy dispersion spectrometry (SEM-EDS) are sufficient to distinguish the four types of Monte Arci obsidians. Because of the compositional similarities between these obsidian types, a multivariate analysis is recommended in provenance studies. Although SEM-EDS, electron microprobe-wavelength dispersion spectrometry (EMP-WDS) and particle induced X-ray emission (PIXE) give essentially concordant results in the determination of these six element contents, subtle technique-related biases prevent the combination of SEM-EDS, EMP-WDS and PIXE data on source samples for provenance purposes. An SEM-EDS test-study reveals the first occurrence of obsidians of Lipari for the A Fuata Middle to Late Neolithic site of NW Corsica (north of Sardinia), in addition to the usual Monte Arci obsidians. Similar to EMP-WDS, the SEM-EDS technique requires only millimeter-sized fragments.

Three-dimensional ion micro-tomography

The technique of ion micro-tomography (IMT) provides three-dimensional distribution information about a sample's mass density and elemental composition. The required data are obtained by doing a scanning transmission ion microscopy (STIM) tomography experiment followed by a particle-induced X-ray emission (PIXE) tomography experiment. The experiment times have been vastly reduced now that data are collected with MicroDAS, the new fast data acquisition system. Moreover, the experiment is easier to perform because sample manipulation is automated via computer control. To obtain comparable spatial resolutions between the STIM and PIXE data, the PIXE tomography experiment is performed by implementing a large solid angle between the sample and X-ray detector. To correct for the inherent three-dimensional nature of such an experimental setup, a specially developed tomographic reconstruction technique is used to combine the STIM and PIXE tomography data sets to create an accurate quantitative tomogram of the sample. The efficacy of the entire IMT process is tested with a characterised “standard” sample. The calculated data agree well with the quantitative and structural information known about the sample. To interpret the three-dimensional distribution information, a special volume rendering program is used to visualise various aspects of the tomogram. Each aspect is colour coded to facilitate the easy visualisation of multiple complex three-dimensional structures.

Analysis of lichen thin sections by PIXE and STIM using a proton microprobe

In order to better understand the distribution pattern of mineral elements in lichen tissues, thin sections (15 μm) of the foliose, vagrant soil lichen Xanthoparmelia chlorochroa were examined using proton microprobe Particle induced X-ray emission (PIXE). This technique was used to make two-dimensional scans, with 5 μm resolution, across tissue cross sections of the test species. Element maps for Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Cu, Zn, and As have been prepared. Several elements are strongly localized in the element maps. PIXE data are complimented with STIM, light micrographs, and SEM images. Preliminary data suggest that nuclear microprobe techniques may be useful in elucidating element absorption and transport mechanisms in lichens.

Elemental composition of aircraft-sampled aerosols above the southern bight of the North Sea

During the period from September 1988 to October 1989, 23 flights were carried out over the Dutch Continental Shelf of the North Sea and a total of 108 aerosol filter samples were collected. The samples were analyzed for Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br and Pb using both particle-induced X-ray emission (PIXE) and energy-dispersive X-ray fluorescence (EDXRF). The results from PIXE exhibited better precision and lower detection limits than those from EDXRF. Therefore the further discussion and interpretation was based on the PIXE data only. It was observed that Si, S, V, Mn, Ni, Cu and Pb were enriched with respect to the earth's crust. It was seen that winds from the sector Southeast-South contributed most significantly to the total aerosol concentration. The vertical profiles of several elements indicated that their concentration increases with proximity to the sea. Principal factor analysis on the data matrix containing elemental concentrations, height and wind direction parameters allowed us to identify 6 possible aerosol sources, namely, a composite of CaSO4 and metallurgical activities, refuse incineration, residual oil combustion, quartz, soil dust and sea-salt aerosol.

PIXE analysis of atmospheric particulate matter in glass fibre filters

A 3-step extraction procedure was developed to allow particle-induced X-ray emission (PIXE) analysis of particulate matter in normal glass fibre filter samples. The detection limits, expressed in ng/m 3 of air, for the filter extracts were 5 to 30 times lower than those achieved by PIXE analysis of ordinary Nuclepore polycarbonate filter samples. The concentration results were compared with those obtained from routine atomic absorption spectrometry measurements and with the PIXE data from Nuclepore stacked filter unit samples taken in parallel.

Sputtering Analysis with PIXE

The applicability of the particle induced x-ray emission (PIXE) in the determination of sputtering distributions and yields was studied. Sputtered particles were caught on foils for the 45 keV to 125 keV self sputtering of Fe, Ni, Cu, Ti, Mo and Au and for the 90 keV sputtering of both target and implanted particles of Ni+ + Cu, Cu+ + Ni, Ni+ + Fe, and As+ + Ag, and for the target particles of Ar+ + Au. Sputtered particles were collected in an ultra high vacuum (UHV) and in a poorer vacuum system with 99.99% pure Al catcher foils. PIXE data, the x-ray yields from 1 MeV proton and 2 MeV alpha particle beam bombardments, were used to determine the angular distribution of the sputtered products. The sputtering yield was calculated from the angular disbution data by integration over a hemisphere assuming azimuthal symmetry. The efficiency of the PIXE systems was calibrated with a standardized target such as 18 μg/cm2 Fe on the same 99.99% Al foil material. The Al x-ray yield of the catcher foils provided a normalization of all data from a given catcher foil. For a number of samples studied, we have been able to compare the distribution and yields obtained with PIXE to those measured by the Rutherford backscattering (RBS) technique. Also separate RBS analysis of Xe markers in the sputtering targets provided yield values. Comparision of the PIXE and RBS results indicate that the PIXE sputtering distribution and yield measurements are comparable.