Abstract: A fast (25 min) non-destructive determination of silicon in steel by 14-MeV neutron activation is described. The 1.78-MeV 28Al activity, induced by the reaction 28Si(n,p)28Al, is counted on a NaI(Tl) detector. An oxygen flux monitor is used to normalise to the same neutron flux. Two methods are described to correct for the 56Mn activity (2.58 h), induced into the iron matrix via 56Fe(n,p)56Mn. Nuclear interferences of phosphorus and aluminium have been examined. Special attention has been paid to stainless steels. A sensitivity of 0.02 to 0.05% of silicon is obtained. The precision is 2 to 3% for steels containing above 1% silicon, and 7% for 0.1% of silicon.

Abstract: A fast (10 min) non-destructive determination of copper in. steel and cast iron by 14-MeV neutron activation analysis is described. The 0.511-MeV annihilation radiation of62Cu (T1/2=9.8 min), induced by the reaction63Cu(n,2n)62Cu, is counted by two opposing NaI(Tl) detectors operating in coincidence. An oxygen flux monitor is used to normalise the irradiations. For high phosphorus contents, two measurements are made and the 9-min activity contribution is calculated. As the iron content of the samples is known, the use of pure iron samples allows correction for53Fe activity from the reaction54Fe(n,2n)53Fe(T1/2= 8.9 min). When the phosphorus and silicon activities are low, the procedure of counting and computing can be greatly simplified. Nuclear interferences of most common alloying and impurity elements were investigated.The precision is 23% for steels containing above 1% Cu, andCa. 10% for 0.1%Cu.

Abstract: The determination of silicon via the 28Si(n,p)28 Al reaction by means of 14-MeV neutrons is applied to the analysis of pollution and natural aerosols. A Whatman 41 filter (40 cm2) on which airborne particulate material has been collected is compressed into a 3 × 12.7 mm pellet. Standards are prepared in the same way from clean filters spiked with a silicate solution. After a 50-s irradiation and a 75-s decay time, the sample is counted for 2 min with 5 × 5 NaI(Tl) well detector. The 1.779-MeV photopeak of 28Al is measured with a single channel sealer chain or with a multichannel analyser. The reproducibility, sensitivity and liability to interference from other elements were investigated for both counting systems. The homogeneity of the pellets and the filters was checked. The overall precision of one single-channel determination was estimated to be 3.5% after a 24-h high-volume sampling time. Samples collected in urban, industrial and remote areas with concentrations ranging from 0.05 to 15 μg Si m-3 air were analysed and the results are discussed.

Abstract: A general standardization method is described for the determination of oxygen in solid samples via the 16O(n,p)16N reaction. Two systems of flux monitoring are considered: the sample versus standard comparator method and BF3 monitoring. The average flux in sample and standard, fast neutron shielding, fast neutron scattering, absorption of fast neutrons, absorption of 16N γ-rays and counting efficiency of sample and standard are considered. The influence of the target diameter on the obtained correction factors has also been studied. Total achievable accuracy is believed to be about 1%.

Abstract: Elemental analysis for all of the light elements up through chlorine by elastic scattering of 16 MeV protons has been shown to be feasible. Basic problems associated with such measurements are discussed including kinematics, angular distribution, and sample backings. Spectra are presented for air particulate matter for both a total filter (Nuclepore) and a size fractionated air impactor (polystyrene backed) sample. The method is absolute, non destructive and can be used in conjunction with proton induced x-ray fluorescence to quantitatively analyze all elements in the same sample in minutes of time.

Abstract: Chromium and silicon are determined simultaneously in steel by 14-MeV neutron activation analysis. The activities of 52V(Eγ=1.43 MeV,TView the MathML source=3.76 min) from 52Cr(n,p)52V and 28Al (Eγ=1.78 MeV; TView the MathML source=2.24 min) from 28Si(n,p)28Al are evaluated by mixed γ-ray spectrometry. The influence of manganese and phosphorus, the main interfering elements, is negligible for most stainless steels. The count rate should be limited, to avoid 52V pulse pile-up effects interfering in the 28Al energy region. Precisions in the 2-10% range are reached, depending on the concentrations, for a 10-min analysis time. Results for a series of steel samples are compared with industrial analyses.

Abstract: A nonurban base line has been established for nine trace element constituents of aerosol particles as a function of particle size at ground level sampling stations in north Florida up to 50 km from the Gulf of Mexico. The particle size range 0.25- to >4-μm aerodynamic diameter was investigated by cascade impactor sampling and elemental analysis by proton-induced X ray emission. By using a strategy of sampling at urban, forest, and coastal locations and by choosing approximately 48-hour sample averaging intervals the potential dependence of the base line levels both on local pollution and natural sources and on local particle size specific aerosol removal processes could be evaluated. It is found that elements contained in the largest particles, especially those of >4 μm, display the greatest degree of average concentration difference between sites, a result suggesting short atmospheric residence times and the importance of local dispersion sources and atmospheric cleansing processes in regulating the particle concentrations in air. Elements contained in particles of <2-μm diameter show little average concentration difference between sites unless they are influenced by local pollution sources, a finding suggesting that their concentrations in air are regulated by large-scale sources and transport processes. Sulfur in the smallest particles shows a marked constancy of concentration, but it may be modified in the largest particle size ranges in relation to proximity to the seacoast. No evidence is found for dependence of particulate sulfur concentrations on local pollution sources. K, Ca, Ti, Fe, and Zn appear to be regulated in the main by terrestrial source processes, and Cl by marine source processes, but Br and Pb appear to be accounted for adequately by assuming automotive fuel combustion as their major source. Limited data obtained for V indicate that it may vary considerably with fluctuations in aerosol transport from oil-fired electric power plant sources in the region. Limited additional data also suggest that Mn is derived from sources of natural terrestrial composition. In view of these findings, certain criteria may be set for the design of a meaningful nonurban aerosol monitoring network.

Abstract: Proton Induced X-ray Emission, (PIXE), is capable of high precision analysis for trace element components of aerosol particle size fractions sampled by cascade impactor. A statistical evaluation of data quality has been carried out in order to distinguish between analytical uncertainties in the PIXE procedure, errors caused by cascade impactor performance and by other factors in the sampling procedure, and geophysical causes of differences in composition and particle size distributions of the elements in aerosols. Replicate analyses and simultaneous samplings taken in north Florida and St. Louis have been used for the data evaluation. In addition to the analytical error the sampling procedure contributes an error of ~ 10% to be added quadratically. The resulting precision is sufficient to evaluate the data in geophysical terms. This is illustrated by means of sample sets taken simultaneously in an urban, forest and coastal environment of the same region.

Abstract: Several sample preparation methods for waters for energy-dispersive x.r.f. were examined, as well as the influence of sample size on the analytical characteristics. The most satisfactory simple, rapid method proved to be spotting of 1.5 ml of water sample on a Whatman-41 cellulose filter paper provided with a wax ring of 29-mm diameter and evaporating the water with an unheated air stream from underneath. Sensitivities are below 100 p.p.b. for most elements and often below 50 p.p.b. when the optimal secondary fluorescer is used. Accuracy and precision are usually in the 1520 % range. The method is applicable to many dilute aqueous solutions as is illustrated by analysis of industrial water samples and ashed biological material.

Abstract: A computer routine was developed for qualitative and quantitative analysis of photographically recorded spark-source mass spectra. Particular attention is given to the case of a graphite matrix. The program starts from the line intensities (expressed as Seidel values) and isotope masses calculated from the densitometer readings by a commercially available routine. From the intensities in the different exposures (typically 15 stages), it computes the parameters for the linear parts of the density curves for each ion. Taking into account mutual interferences of multivalent ions, isotope or C-clusters, oxide, carbide and dicarbide ions, the program automatically identifies and then quantifies the elements present. The precision of the results is around 5%. Reading and complete processing of one photoplate is achieved within 23 h.

Abstract: The relative merits of eight procedures for preconcentrations of trace metal ions from natural water samples and synthetic solutions are evaluated. Spikes (100 μg l−1 ) of Mn, Co, Zn, Eu, Cs and Ba and the corresponding radioactive tracers were added to batches of drinking water, estuarine water, sea water, ground water, twice-distilled water and ahumic material solution. After equilibration for 25 months, the following techniques were applied: passage through columns of Dowex Al chelating resin and ofsilylated silica gel, filtration through laminate membrane filters and chelating diethylenetriamine cellulose filters, precipitation with sodium diethyldithiocarbamate and l-(2-pyridylazo)-2-naphthol, extraction with ammonium pyrrolidinedithiocarbamate, and chelation by 8-quinolinol (oxine) followed by adsorption on activated carbon. The quantitative characteristics of these techniques and the influence of the water matrix effects are discussed, as well as the applicability for x-ray fluorescence analysis.