Search

The Salt Lake City EPA Environmental Monitoring for Public Access and Community Tracking (EMPACT) project, initiated in October 1999, is designed to evaluate the usefulness of a newly developed real-time continuous monitor (RAMS) for total (non-volatile plus semi-volatile) PM2.5 mass and the health relevance of PM2.5 measured by this method as compared to other measurements of PM2.5 parameters. Ammonium nitrate and semi-volatile organic compounds (SVOC) are significant components of fine particles in many urban atmospheres. These components however, are not properly measured by current EPA accepted methods, such as the PM2.5 FRM, due to loss of semi-volatile material (SVM) from the filter during sampling. Continuous PM2.5 mass measurements are attempted using methods such as the R&P TEOM monitor. This method however, heats the sample to remove particle-bound water. This results in evaporation of significant amounts of semi-volatile material. Similarly, continuous carbonaceous material monitors are expected to lose semi-volatile organic material during sample collection. Continuous RAMS and collocated TEOM monitor data have been obtained at the EMPACT sampling site in Salt lake City, Utah during a 2-year period. Results obtained for the continuous determination of total PM2.5 mass with the RAMS have been validated by comparison with results obtained from collocated PC-BOSS diffusion denuder integrated samples at the EMPACT sampling site in Salt Lake City, Utah during three intensive sampling periods (winter 1999–2000, summer 2000, and winter 2000–2001). While the RAMS is shown to measure total PM2.5, including semi-volatile nitrate and organic material, commercially available semi-continuous TEOM and C monitors do not reliably measure these species.

Lichens are known to accumulate airborne elements. This characteristic makes them useful as biomonitors of air quality. However, direct correlations of element concentrations in the air with element concentrations in lichen thalli are generally unavailable. The purpose of this study was to quantitatively examine the relationship between concentrations of copper in ambient air samples and thalli of foliose and fruticose lichens. Lichen samples from four sites along an air copper gradient were collected and analyzed. Foliose specimens consistently accumulated more than twice as much copper as fruticose specimens at all four sites. The relationship between copper concentrations in foliose and fruticose lichens and ambient air samples along an airborne copper gradient was examined using a stepwise regression model. An R2 value of (0.84) and an F-statistic of (182.5, p

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.

Thirty-six lichen samples that were collected from five wilderness areas and a national monument in the intermountain western United States have been analyzed by PIXE for the determination of 21 elements: P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ba, and Pb. Samples were powdered and spiked with Y as an internal standard. The powder was analyzed directly as a sample of moderate thickness. Elemental concentration means and ranges were generally consistent with concentration ranges from other studies of unimpacted lichens. Some samples, however, had high concentrations of S, Cu, As, and a few other elements. There are interpretations of the data that imply some wilderness areas are being impacted to some degree by industrial-plant atmospheric emissions.

Hair samples were obtained from ten mummies of the archaic and formative cultures of the north coast of Chile. Each sample was divided into two portions. One portion was washed in acetone and then water and the second portion remained unwashed. All samples were then prepared by an acid digestion procedure and analyzed by PIXE. The washed and unwashed samples were compared to determine what elements were present in the material on the hair surface. Concentrations of the elements Ca, Ti, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, and Pb are reported. Comparison was made to previously published elemental analyses of mummy hair and modern hair. One sample, which had a reddish hue, was found to contain unusually large quantities of Fe and As. Since the unwashed sample had much higher concentrations of these elements than the washed sample, it is believed that the reddish color originated in a mineral dye applied to the hair.

Self-supporting foils of aluminum oxide in the thickness range 100 to 300 nm were prepared by anodic oxidation of aluminum foil and subsequent dissolution of the unreacted aluminum. The foil thicknesses were measured by scanning electron microscopy. Using these foils, stopping cross sections of aluminum oxide for protons and deuterons were measured for particles in the energy range 0.90 to 2.50 MeV. These measured stopping cross sections are compared to other literature results and to the theoretical values as predicted by Bragg's Rule.

Materials containing a significant silicate matrix are often considered for element analysis by the PIXE method. In some circumstances such materials may not be conveniently prepared for sample analysis. It has been found that a lithium metaborate fusion-acid dissolution procedure works well for converting siliceous materials into solution from which thin-target PIXE samples may be made. We have demonstrated that this method will allow rapid and accurate element analysis. The lithium metaborate, however, creates a matrix residue leading to the requirement for sample thickness corrections and an increase in detection limits. We have found this to be a useful sample-preparation method.

One of the primary components of the background in PIXE spectra is secondary electron bremsstrahlung (SEB). However, in order to evaluate the integral usually used to calculate SEB cross sections, certain simplifications must be made, such as assuming an infinite target thickness. In order to more realistically model the physical processes involved in SEB, a Monte Carlo approach is useful. SEB cross sections are calculated by Monte Carlo techniques and the results are compared with the work of Ishii, Morita, and Tarawa [Phys. Rev. A13 (1976) 131; Int. J. PIXE l (1990) 1]. To demonstrate the flexibility of the Monte Carlo method, effects due to the target thickness and the proton-electron cross section are examined.

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.

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.

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.

A single-acid, wet-digestion method using nitric acid has been used to prepare samples for element analysis by thin-target, particle induced X-ray emission (PIXE). The method involves repeated cycles of heating in acid and charring until a clear solution is obtained. Good recovery of elements is observed and matrix reduction is achieved. The method has been successfully applied to organic, carbonaceous and a few other inorganic samples that were in a variety of chemical and physical forms.

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.

A FORTAN program, NANOLEX, has been developed for the analysis of particle induced X-ray spectra. Background components are stripped from a spectrum and recursive relations are employed to strip away contributions of non-Gaussian peak components. A technique known as linearization of a Gaussian is used to determined an energy scale and a good estimate of peak intensities. Ideal Gaussian spectra are generated for elements in the sample and a Fletcher-Powell optimization method is used in a linear least-squares fitting of ideal spectra to the stripped experimental spectrum. The program has been developed with both small and large computer versions.

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

Effluents from a high temperature, high pressure, entrained flow gasifier were analysed for possible inorganic and organic pollutants. The effluents and product gases from this type of reactor are very clean compared to those produced in established commercial gasification processes. The only major potential pollutants are the particulate matter and NH4+ in the scrubber water, the bottom ash, and the H2S and HCN in the product and flash gases. All of the non-volatile organic compounds produced are quantitatively adsorbed by the particulate matter in the scrubber water. Increasing the pressure and decreasing the O2coal ratio tended to reduce pollutants in the effluents and increase coal conversion efficiency.

Various links between acquisitions and circulation systems are possible whether manual or automated. Design considerations of such interfaces between vendor and/or in-house systems must consider record formats, linking data fields, and future demands of maintaining the interface. The greatest advantages to circulation and acquisitions functions are generally realized in the areas of transferring rather than recreating data, as well as collection development information. Benefits to other library functions and programs must also be considered in the overall development and evaluation.

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.

Spectra and angular distributions were obtained for the reactions and conditions 16O(3He, p) 18F at E( 3 H He ) = 19.8 MeV from θlab = 9 ° to 170° for 18F excited states below 11.3 MeV excitation and for 16O(α, d)18F at E(α) = 40.3 MeV from θlab = 8° to 80° for 18F excited states below 12.7 MeV excitation. Distorted-wave (DW) calculations for the (3He, p) reaction were compared to experimental angular distributions and relative total cross sections. Agreement was found when spin-independent interaction potential was used. Nuclear wave functions used in the calculations are discussed. Spectroscopic and configuration assignments were made or confirmed on the basis of excitation energy, angular distributions, comparison of (α, d) and (3He, p) results, relative total cross sections and comparison of experimental quantities to DW calculations. Configurations and Jπ values of 3+ and 4+ were suggested for 18F levels at 3.358 and 5.594 MeV excitation energy, respectively. Configurations and JπT values were confirmed for some levels at T = 0 assignments were made for a large number of levels. A new 18F level at an excitation energy of 8.596 ± 0.019 MeV was identified.

The 6Li(3He, t)6Be and 10B(3He, t)10C reactions have been studied at E( 3 He) = 30 amd 40 MeV. In 6Be, an excited state is observed at Ex = 1.67±0.08 MeV). In 10C, in addition to the sharp ground and first excited states, level structure centered at Ex = 5.28 and 6.58 MeV is observed.

Geometric calculations and equations for multiple scattering were used to develop an expression for the distribution of protons on a PIXE target. The finite size of the proton beam striking a diffuser foil was responsible for a region of lesser proton intensity on the target. A probe consisting of electrodeposited copper on an iron wire was scanned across the target to experimentally measure proton intensity. The experimental beam intensity distribution was used to calculate an effective beam area of constant proton intensity.

Residues from several unservicible munitions and chemical agents disposed of by incineration and chemical conversion have been quantitatively analyzed for elemental content using proton-induced X-ray emission (PIXE). Carbonaceous residues were first digested by a single-acid, wet-oxidation procedure and silicious residues were prepared using a lithium metaborate fusion-acid dissolution procedure. The resulting solutions were applied to a polycarbonate film and analyzed using 2 MeV protons. Recoveries of trace elements were determined and were acceptable. Samples include oxidation residues from white phosphorus rockets and projectiles, products from the controlled combustion of bulk ammonium picrate, baghouse and cyclone dust samples. Agent FS conversion samples, and electrolyte solutions from a warhead power supply.

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.