M.W. Hill

The formation and stability of sulfite species in aerosols

Recent epidemiological and animal lexicological studies indicate that reactions between SO2 and metal containing aerosols result in the formation of respiratory irritants. These studies point out the importance of understanding in detail the chemical species formed by such interactions. Using a combination of thermometric, ESCA and PIXE analysis techniques, it has been demonstrated that both inorganic and organic S(IV) species are stable constituents of aerosols associated with pollution sources containing SO2 and transition metals or with pollution sources resulting from the combustion of fossil fuels. The data indicate the inorganic sulfite species are present as complexes with Fe(III), Cu(II), Zn(II) and possibly Pb(II). The concentration of these inorganic sulfite species is 10 to 30% of the sulfate concentration in primary aerosols produced by smelters. These inorganic sulfite species tend to be evenly distributed over the various particle sizes. In contrast, the inorganic sulfite in primary aerosols produced by fossil fuel burning sources tends to exist in the <3 μm size range and can vary from a negligible to a major fraction of the sulfur species produced. The factors which control this variability are presently unknown. The principal mode of formation of such species in the ambient atmosphere appears to be via SO2 absorption. Oxidation of S° or S(-II)species to form inorganic sulfite complexes or oxidation of the sulfite species to sulfate are both extremely slow, with time constants on the order of months. Aerosol samples collected from the plume, stack, or flue lines of coal burning facilities or collected in New York City or rural Utah produce sulfite when hydrolyzed with dilute aqueous acid. It is postulated this sulfite is produced from organic-SO2 adducts in the sample. These organic S(IV) containing species are predominantly found in the resptrable size range and are present at from 5 to 50% of the sulfate concentration. It is probable that some of these S(IV) species play an important role in the removal of SO2(g) from the atmosphere to form sulfur containing aerosol species.

Proton induced X-ray emission analysis of biological samples: Some approaches and applications

Abstract The method of proton particle induced X-ray emission (proton PIXE) has been used by several teams of researchers for minor and trace element analysis of many interesting biological samples. The proton PIXE analysis method is often ideal for such samples because it allows for the simultaneous determination of several elements and requires only a small sample. Difficult problems are often encountered in preparing samples suitable for PIXE analysis and considerable imagination has been used to solve these problems. Samples both thick and thin in comparison to the particle-beam range have been used. Thin samples are usually supported on thin foils. Procedures used in preparing thins samples have included wet ashing, dry ashing, nebulization of a suspension, freeze-drying, sectioning with a microtome, and spiking with noninterfering elements. Each method of sample analysis has advantages which must be understood when choosing a method for a particular problem.

The chemical composition of smelter flue dusts

Abstract The chemical composition of two copper and three lead smelter flue dust samples has been studied by wet chemical analysis techniques for sulfite, sulfate, arsenite, anenate, chloride, fluoride, phosphate and acid species; by photoetoctron spectroscopy; by X-ray diffraction analysis; and by proton induced X-ray emission spectroscopy. The results indicate the acidity, chemical composition, and time stability of the flue samples varies greatly. Specific components identified in the samples include; sulfate, sulfite, bisulfate, elemental sulfur, sulfide, arsenite, arsenate, arsenic suifide, chloride, fluoride, phosphate, Fe(II), Fe(III), total trace metal composition, and the specific compounds As 2 O 3 , PbSO 4 , PbO · PbSO 4 , ZnO, Fe 3 O 4 , and Fe 2 O 3 . Acidity, and die chemical components controlling acidity vary widely among the samples studied. Comparisons of the bulk and surface composition of the samples indicate that the surface species cannot be predicted from the bulk composition. From the data obtained, satisfactory total mass and charge balance is obtained for the major (> 1 wt%) components present in the flue dusts studied.

Sulfur chemistry in a copper smelter plume

Sulfur transformation chemistry was studied in the plume of the Utah smelter of Kennecott Copper Corporation from April to October 1977. Samples were taken at up to four locations from 4 to 60 km from the stacks. Data collected at each station included: SO2 concentration, low-volume collected total paniculate matter, high-volume collected size fractionated paniculate matter, wind velocity and direction, temperature, and relative humidity. Paniculate samples were analyzed for S(IV). sulfate, strong acid, anions, cations, and elemental concentrations using calorimetric, ion Chromatographie, FIXE, ESCA, ion microprobe, and SEM-ion microprobe techniques. The concentration of As in the paniculate matter was used as a conservative plume tracer. The ratios Mo/As, Pb/As, and Zn/As were constant in particulate matter collected at all sampling sites for any particle size. Strong mineral acid was neutralized by background metal oxide and/or carbonate particulates within 40km of the smelter. This neutralization process is limited only by the rate of incorporation of basic material into the plume. Two distinct metal-S(IV) species similar to those observed in laboratory aerosol experiments were found in the plume. The formation of paniculate S(IV) species occurs by interaction of SO2 (g) with both ambient and plume derived aerosol and is equilibrium controlled. The extent of formation of S(IV) complexes in the aerosol is directly proportional to the SO2(g) and paniculate (Cu + Fe) concentration and inversely proportional to the paniculate acidity. S(IV) species were stable in collected paniculate matter only in the neutralized material, but with proper sampling techniques could be demonstrated to also be present in very acidic particles at high ambient SO2(g) concentrations. Reduction of arsenate to arsenite by the aerosol S(IV) complexes during plume transport is suggested. The SO2(g)-sulfate conversion process in the plume is described by a mechanism which is first order in SO2(g). Equations are derived describing sulfur chemistry when both S(IV) and sulfate formation occur in a plume. The formation of sulfate results primarily in the formation of < 0.5 μm particulates. The formation process is not correlated with plume expansion, paniculate acidity, metal content, or S(IV) species. Due to meteorological restrictions on sampling, data were collected only during periods of maximum insolation. The formation of sulfate from SO2(g) in the plume during periods of high insolation is temperature dependent with an apparent activation energy of 16.6 ± 1.4 kcal mol−1 and a k1, value of 0.039h−1 at 25°C.

Recent advances in particle-induced X-ray emission analysis applied to biological samples

Abstract Papers reporting the application of particle induced X-ray emission (PIXE) analysis to biological samples continue to appear regularly in the literature. The majority of these papers deal with blood, hair, and other common body organs while a few deal with biological samples from the environment. A variety of sample preparation methods have been demonstrated, a number of which are improvements, refinements and extensions of the thick- and thin-sample preparation methods reported in the early development of PIXE. While many papers describe the development of PIXE techniques some papers are now describing application of the methods to serious biological problems. The following two factors may help to stimulate more consistent use of the PIXE method. First, each PIXE facility should be organized to give rapid sample processing and should have available several sample preparation and handling methods. Second, those with the skill to use PIXE methods need to become closely associated with researchers knowledgeable in medical and biological sciences and they also need to become more involved in project planning and sample handling.

Proton induced X-ray emission of spherical particles: Corrections for X-ray attenuation

Abstract The intensity of X-rays from PIXE (particle induced X-ray emission) analysis of particulate matter may be reduced relative to that expected from thin samples because of two effects: reduced X-ray cross sections due to proton energy loss, and X-ray attenuation. An equation has been derived for the correction of reduced X-ray intensities emitted from spherical particles. An arbitrary but homogeneous particle composition is assumed. A single particle size or a particle size distribution may be selected. The angle of X-ray detection relative to the incident beam may also be selected. Calculations for X-ray emission lines from sodium to tin have been made for several particle compositions, several radius values and a particle size distribution. It was surprising to find that attenuation corrections were independent of detection angle for all emission lines and particle sizes studied.

Identification of vanadate (VO2+) in particles from the flue lines of oil-fired power plants.

Fly ash samples were collected from the flue lines of two different oil-fired power plants and analyzed by a variety of analytical procedures designed to determine the V cations extractable from the samples. Both VO/sub 2//sup +/ and VO/sup 2 +/ were shown to be present in the samples. The V(V) cation, VO/sub 2//sup +/, was the principal species extracted from these samples.

Measurement of sample temperatures reached during proton and alpha particle irradiation of thin PIXE targets

Abstract Measurements were made of sample temperatures reached during irradiation of thin PIXE targets by 2 MeV protons and 18 MeV alpha particles as a function of beam current density. Results are given for samples placed on two types of target backings.

Apparatus for Electron Spin Resonance Studies at Very High Pressures

Apparatus for studying electron paramagnetic resonance in solids under pressure to 60 kilobars and beyond has been developed. The high pressures are produced between dielectric Bridgman anvils, one of which serves as a microwave resonance cavity. The instrument makes possible the study, by EPR techniques, of paramagnetic atoms or ions subject to stresses which might be expected to induce changes in their electronic structure.

Proton Induced X-Ray Emission Analysis - A Complement to Analytical Methods Used in Environmental Studies

Particle induced X-ray emission (PIXE) analysis is a highly versatile method of element analysis. Thus it is well suited for use as a complement to other methods of analysis in experimental programs requiring both chemical and elemental analyses. This paper reports some results of two projects where PIXE was used in conjunction with titration calorimetry, ion chromatography, atomic absorption spectroscopy, gas chromatography/mass spectrometry, X-ray fluorescence spectroscopy and some other methods. The first is a study of sulfur chemistry in a copper smelter plume. Arsenic was found to be a conservative tracer of the plume and was used for calculation of plume dilution. Calcium was found to be characteristic of the background or ambient aerosol and was used to correct particulate data for the background contribution. The use of both plume and ambient tracers and of data from other analytical methods noted above led to the determination of several aspects of the plume sulfur chemistry. The second project is a study of the effluents from a high-temperature, high-pressure entrained flow gasifier. The scrubber water and particulate matter entrained in the scrubber water and in the product gas were analyzed by PIXE. Of particular interest were the low elemental concentrations in the scrubber water.