PESA as a complementary tool to PIXE at CTU Prague

Proton Elastic Scattering Analysis (PESA) is a simple convenient method for hydrogen analysis in thin samples. A Proton Induced X-ray Emission (PIXE) target chamber was equipped with a PIPS detector for detection of forward-scattered protons. One of the objectives was to perform PIXE and PESA analyses of air particulate targets simultaneously. Tests and calibrations were fulfilled mainly with Mylar foils 1.5–6.5 μm thick in the proton energy region between 1.35 and 2.3 MeV. The energy dependence of scattering cross section is different from the Rutherford formula. Comparison of PIXE/PESA analysis with the Guelph Scanning Proton Microprobe Laboratory at the University of Guelph, Canada on seven aerosol samples was carried out. The intercomparison results validated our PESA/PIXE quality assurance protocol. In addition, repeated measurements of Gelman Teflo^TM filters indicated a gradual increase of hydrogen content by 1 ng/cm² per 1 μC/cm² proton dose.     

Analysis of atmospheric aerosols by particle-induced X-ray emission, instrumental neutron activation analysis, and ion chromatography

Particle-induced X-ray emission (PIXE), ion chromatography (IC), and occasionally also instrumental neutron activation analysis (INAA) were used in combination for the analysis of atmospheric aerosol samples that were collected on Nuclepore polycarbonate filters. A comparison of the results enabled us to evaluate the matrix effects (i.e., particle size effects) of the PIXE analysis for the light elements and to assess the water-solubility and/or speciation of a number of elements (e.g., S, K, Ca). Results are presented from several measurement campaigns at urban and forested sites in Europe, whereby PM10 or PM2.5 filter samples were taken. From the PIXE and IC results for a 2003 summer campaign at the K-puszta site in Hungary, it was estimated that organosulphates could be responsible for 20% of the total sulphur concentration and 30% of the organic aerosol in PM10. The comparison of the IC and PIXE data for K and Ca from the various sites indicated that most of the Ca was water-soluble (the mineral dust Ca was presumably mostly present as calcite, and perhaps also in part as gypsum); in contrast, for K, only half of it was typically water-soluble, indicating that it was to a large extent associated with insoluble mineral dust. Exceptions, with almost fully water-soluble K, were found for samples that were substantially impacted by biomass burning.     

Analysis of C, N and O in aerosol collected on an organic backing using internal blank measurements and variable beam size

A method with low MDL (minimum detection limit) was developed for analysis of carbon (C), nitrogen (N) and oxygen (O) in aerosol samples collected on an organic backing. An accelerator-produced beam of protons interacting with the sample and the detection of elastically scattered protons (PESA; particle elastic scattering analysis) and emitted X-rays (PIXE; particle-induced X-ray emission) were the basic components of the setup. The method is based on measurement of internal blank concentrations, i.e. measurement of the blank concentration outside the aerosol deposit in each sample, and the use of two sizes of the beam in order to improve the MDL of the analysis. Large beam size covering the entire aerosol deposit was used to obtain quantitative analysis with PIXE. Small beam was used to obtain relative elemental concentrations with PESA and PIXE, which were transformed to absolute values by the aid of large-beam analysis. The small-size-beam served two purposes: to make internal blank measurements feasible and to improve the signal ratio of aerosol-deposit to backing. Compared with the traditional way of analysis, using a beam that is larger than the deposit and specially prepared blank samples, the new method reduced the MDL of C, N and O by a factor of 130, 70 and 90, respectively. The new method was applied to aerosol samples collected in the upper troposphere and the lowermost stratosphere from the CARIBIC platform. As far as the authors know, these measurements are the first quantitative determinations of C, N and O in the aerosol of this part of the atmosphere. The results show that these elements together with sulfur are major components of the aerosol.     

质子非卢瑟福背散射测量气溶胶样品中氢、碳、氮和氧的含量

气溶胶样品中Z＞12以上元素含量的质子荧光(PIXE)分析是北京师范大学GIC4117串列加速器的主要应用领域之一。为弥补PIXE无法分析H、C、N和O等轻元素之不足，在PIXE靶室160°散射角安装金硅面垒探测器，用质子非卢瑟福背散射分析（PNBS）方法对核孔膜采集的气溶胶样品中H、C、N和O等轻元素的含量进行测量。测量得到的气溶胶样品中H和Si元素含量与质子前角散射（PESA）和PIXE的分析结果相近，表明PNBS可用于核孔膜采集的气溶胶样品的分析。     

冬季上海吴淞地区大气颗粒物PM10的元素主成分分析

从2002年12月到2003年2月,利用8通道采样器对上海吴淞地区进行3个月的大气气溶胶PM10(空气动力学直径小于10μm的颗粒)的采样。使用质子激发X射线荧光(PIXE)分析方法进行了多元素质量浓度测定,然后对获取数据进行主成分分析,讨论了吴淞地区8个风向采集的PM10中含有的主要化学元素成分和可能的来源。     

Analysis of atmospheric aerosols by PIXE: the importance of real time and complementary measurements

Particle-Induced X-ray Emission (PIXE) has been used for more than 30 yr in many urban and background air pollution studies. The technique has certainly contributed to the understanding of source-receptor relationship for aerosol particles as well as to aerosol physics and chemistry. In the last few years, where aerosol issues were strongly linked to global climate change through the relationship between aerosol and atmospheric radiation points to new challenges in atmospheric sciences, where PIXE could play an important role. Also the recognition for the inter-relationship between aerosol and liquid and gas phases in the atmosphere makes important to integrate PIXE aerosol analysis with other complementary measurements. The use of Nephelometers and Aethalometers to measure scattering and absorption of radiation by aerosol particles can be done in parallel with particle filter collection for PIXE analysis. Parallel measurements of trace gases using traditional monitors as well as with new techniques such as Differential Optical Absorption Spectroscopy (DOAS) that can provide concentration of O₃, SO₂, NO₃, NO₂, HCHO, HNO₃, Benzene, Toluene, and Xylene, is also important for both urban and remote aerosol studies. They provide information that allows a much richer interpretation of PIXE data. Recently developed instruments that provide real time aerosol data such as the Tapered Element Oscillating Microbalance (TEOM) PM₁₀ monitor and automatic real time organic and elemental carbon analyzers provide extremely useful data to complement PIXE aerosol analysis. The concentrations of trace elements measured by PIXE comprise only 10–30% of the aerosol mass, leaving the organic aerosol characterization and measurement with an important role. The aerosol source apportionment provided by PIXE analysis can be extended with other aerosol measurements such as scattering and absorption, estimating for example, the radiative impact of each discriminated aerosol source. The aerosol bulk PIXE measurements can be complemented with soluble concentrations provided by Ion Chromatography (IC) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Recent developments in remote sensing techniques and products also enhance significantly regional aerosol studies. Three-dimensional air mass trajectories should be integrated in aerosol studies for urban and remote areas. The applications of these techniques to study urban aerosols from São Paulo and Santiago de Chile have broadened extensively the scientific scope of these studies.     

PIXE and XRF analysis of particulate matter samples: an inter-laboratory comparison

PIXE and XRF are very effective techniques in atmospheric aerosol investigation, therefore they are extensively used by the authors. In this work an inter-laboratory comparison of the results obtained analysing several samples (collected on different substrata) with both techniques is presented: the samples were analysed by PIXE (in Florence, at the 3 MV Tandetron accelerator of LABEC laboratory) and by XRF (in Genoa and Milan, where two Oxford XRF instruments are operational). The results of the three sets of measurements are in good agreement for all the analysed samples.The aim of this work was also to compare PIXE and XRF performance in atmospheric aerosol analysis with the routine set-up currently in use at the three laboratories, to determine the best technique to be applied depending on the substratum used for aerosol sampling and the main elements of interest for each specific research project. Results of the comparison between the minimum detection limits of both techniques will be shown for all the measured elements, for different substrata (Teflon, polycarbonate and cellulose mixed esters).     

气溶胶中F和Na分析的外束质子诱发γ射线激发曲线测量

在大气颗粒物离子束分析中,质子诱发γ射线分析（PIGE）作为质子诱发X荧光发射（PIXE）的补充方法,通常用于分析轻元素。为得到外束PIGE定量分析气溶胶样品中F和Na元素的最佳实验条件,本工作在北京师范大学串列加速器上测定了质子能量在1.8～2.9 MeV范围内,核反应¹⁹F(p,p’γ)¹⁹F（E_γ=110 keV和197 keV）和 ²³Na(p,p’γ)²³Na(E_γ=440 keV)的γ射线激发函数。     

Trace elements concentration in sediments of Orontes River using PIXE technique

Proton induced X-ray emission (PIXE) has been used to measure trace elements in sediments of Orontes River. Measurements were carried out using a 2 MeV proton beam produced from of the 3 MV tandem accelerator. Sediment samples were collected from 11 sites covering the important potential pollution sources at the river. The accuracy of the experimental procedure was verified using a certified sediment reference material (IAEA-SL1) and was found to be less than 10%. The results have shown that Pb and As were within the natural levels. In contrast, high concentrations of other elements like Cr, Cu, Ni and Zn have been found at different sites and explained by local human and industrial activities.     

扬州西汉墓出土古玻璃的质子激发X荧光分析

化学成分分析是中国古代玻璃研究中一个重要方面，可以为研究中国古代玻璃的起源和技术发展等提供科学的依据，有必要发展新的测试方法。质子激发X荧光(PIXE)技术是一种高灵敏度、非破坏性、多元素定量测定的分析方法。采用PIXE技术对扬州西汉墓出土的玻璃衣片进行了定量分析。结果表明：这些玻璃属中国自创的PbO-BaO-Si02系玻璃；衣片由中心玻璃层和厚度不等的表面腐蚀层组成；腐蚀层比玻璃层含有相对较高的PbO、P2O5和CaO，而BaO和SiO2的含量则比玻璃层大大降低。对实验结果进行了讨论。     

A high sensitivity elemental analysis methodology for upper tropospheric aerosol

In this study, a sampling and analysis tool for aerosol particles has been developed. Its purpose is to characterize upper tropospheric aerosols, where concentrations are low. Since measurements will be made from an airplane, a time resolution of one hour is desirable. These conditions require efficient sampling and analysis with low detection limits. To accomplish this, our sampler uses impaction, concentrating the aerosol deposit on a small area. The impactor has 14 parallel sampling lines which are used sequentially to achieve the time resolution. The elemental analysis is done with Particle-Induced X-ray Emission (PIXE), profiting from its high absolute sensitivity. The aerosol is expected to contain primarily sulphur (S) and emphasis is placed on this element, however the multi-elemental nature of PIXE is of course used. Several substrates have been investigated regarding minimum detection limits. Scanning Transmission Ion Microscopy (STIM) analysis has been conducted on two outdoor aerosol samples, rendering three-dimensional images and mass distribution profiles. The setup was tested at ground level with high time resolution (5 min). Results show that the detection capabilities are excellent.     

Source apportionment of single aerosol particles in the atmosphere of Shanghai city

A nuclear microprobe with high spatial resolution and high analytical sensitivity was applied to analyze atmospheric aerosol at five monitoring sites in Shanghai city.Meantime,a new pattern recognition technique,which used the micro-PIXE spectrum of a single aerosol particle as its fingerprint.was developed to identify the origin of the particle.The results showed that the major contributors to the atmosphere pollution were soil dust(31.6%) ,building dust(30.8%),and the next were vehicle exhaust(13.7%),metallurgic industry excrements(5.6%).oil combustion(5%) and coal combustion(2.3%).Besides these ,about 10% of the particles could not be identified.Based on the cluster analysis of these particles.they could be divided into eight groups.By inference,they might belong to some sub-pollution sources from soil dust,building dust and metallurgic industry excrements.Moreover,some new pollution sources from tyres and chemical plants were also revealed.     

Preprocessing PIXE spectra

Proton induced X-ray emission (PIXE) spectra are normally represented by a model containing both linear and nonlinear parameters. Considerable improvement in calculation time can be made if initial values for these parameters are accurate. This paper discusses simple preprocessing of measured data to obtain estimates for such parameters as energy calibration, detector resolution, and possible elements. This information is useful as either input to a spectrum analysis code or a database for an expert system driving the analysis.     

Study of particulate emissions near a steel plant in Genova by continuous sampling and PIXE hourly analysis

The particulate emissions near a large steel plant located in a densely inhabited suburb of the town of Genova (Italy) have been studied for a period of six months. We have used two-stage continuous streaker samplers and subsequent PIXE analysis with hourly resolution, to follow both seasonal and daily trends. The first streaker sampler remained installed very close to the plant cokery and furnaces, while another sampler was moved to different locations. Samples have been analysed by PIXE, deducing concentrations for elements from Na to Pb. During part of the campaign, the aerosol fractions with aerodynamic diameter (D_ae) < 2.5 μm (fine fraction) and with 2.5 < D_ae < 10 μm (coarse fraction) have been separately collected. We have measured and analysed about 8500 PIXE spectra: the steel plant emissions have been identified to some extent and resolved from other aerosol sources.     

PIXE analysis of trace pollutants in Chaliyar river water in Malabar,India

Analysis of trace elemental concentration in the Chaliyar river water has been carried out using the Proton Induced X-ray Emission (PIXE) spectroscopic technique. Water samples were collected from different locations along the course of the river during summer and rainy seasons. Samples were prepared by a preconcentration method. The PIXE analysis was carried out using 2 MeV protons. The details of the measurements and the results are presented in this paper.     

Hourly measurement of particulate concentrations with streaker samplers and optical methods

We have studied the possibility of continuous particulate monitoring, by an optical system, on the filters of a two-stage streaker sampler. The streaker deposits, collected for PIXE analysis, have been examined off-line by measuring the attenuation of a light beam. The optical analysis provides, in a few minutes, an estimate of hourly total mass concentrations, over a one week period, for both stages, very useful as a selection for further PIXE irradiation. We describe the set-up and the calibration procedures, where PIXE plays a fundamental role in resolving different aerosol compositions and in validating the prototype performance. The results obtained over 2 weeks of operation and the comparison with the aerosol component determined via PIXE analysis, are also discussed.     

PIXE as a complement to trace metal analysis of sediments by ICP-OES

The adverse effects of metal contamination in sediments require methods that can quickly and accurately assess the extent of environmental pollution. Particle induced X-ray emission spectrometry (PIXE) is demonstrated to be a viable alternative to an established method, which consists of acid digestion and Inductively coupled plasma-optical emission spectrometry (ICP-OES) to measure trace metals in sediment. The analysis of trace metal composition by both techniques on a NIST Standard Reference Material mud gives results that are consistent with the certified values for fourteen measured metals, seven of which are common to both methods. A comparison study conducted on a sediment core from a freshwater lake with a known chromium contamination in Muskegon County, MI also shows a good correlation between the methods for transition metals of environmental interest over a wide range of metal concentrations. Total sample preparation and analysis time for the PIXE measurements is roughly one third that of acid digestion and ICP-OES. Also, the acid digestion step does not elute all the metal, while the nondestructive PIXE approach is a total metals analysis method. However the PIXE method generally has higher limits of detection for many environmental metal contaminants. By combining the two techniques, the acid digestion elution factor can be quantified by running PIXE on an original sample and on the residue resulting from acid digestion.     

Design of a dedicated target chamber for PIXE microanalysis of mineral samples

A target chamber design for the proposed mineralogical PIXE microprobe at Guelph is described. A detailed discussion of the light optics requirements for this particular application is presented and a choice made from existing approaches used in electron microprobes.     

核分析相关技术用于上海市大气污染特征研究

本文研究了近年来上海市区和郊区大气气溶胶颗粒物的污染状况,采用的多种核分析方法及相关技术有质子激发X荧光分析(PIXE)、激光粒径谱仪(LPS)、同步辐射X射线吸收精细结构(XAFS)和扩展X射线吸收谱精细结构(EXAFS)分析等先进技术.充分发挥核分析技术高灵敏度、快速无损、多元素微量微区同时分析的优势,从大气颗粒物的形貌特征、粒径分布、质量浓度、元素浓度、化学价态等入手,对上海大气可吸入颗粒物PM23和PM1o展开多方位的综合研究.     

Elemental analysis of agricultural soil samples by particle induced X-ray emission (PIXE) technique

In agriculture, elements essential to vital processes are also called nutrients. A suitable and reliable particle induced X-ray emission (PIXE) methodology for content determination of essential nutrients in soil samples was developed and its effectiveness proved. The PIXE method is applied to intermediate thickness samples, whose mass per area unit are smaller than 1 μg/cm². Precision and accuracy of the method was estimated after repeated measurements of a single reference material: CRM PACS-2 (estuarine sediment) with a matrix quite similar to the soil samples measured. This paper reports the results of elemental measurements in soil samples. A discussion of agricultural soil sample preparation for PIXE analysis is also presented.