Type Of Impactor Research Articles

Collection characteristics of low-pressure impactors with various impaction substrate materials

The effects of types of low-pressure impactors (DLPI; Dekati; referred to hereinafter as “LPI”; and NanoMOUDI-II; MSP) and impaction substrate materials (aluminum foils, quartz fiber filters, and polycarbonate filters) on mass size distribution were studied for diesel exhaust particles from dynamometer test (DEP) and roadside atmospheric particles for a better understanding in terms of chemical analysis of impactor sample. Particle mass size distribution measured with LPI using aluminum foils and polycarbonate filters was distorted toward smaller mode diameters than those measured with NanoMOUDI using aluminum foils in sampling DEP and roadside atmospheric particles. This difference is explained by the occurrence of particle blow off in LPI. Heavy loading due to high concentrations in a specific size range results in greater particle loading height, from which particles are easily blown off by high jet velocities. Mass size distribution of DEP measured with LPI using a quartz fiber filter was modified to larger mode diameter than that measured with NanoMOUDI using aluminum foils. Higher particle collection efficiency than the ideal condition and smaller particles than the calibrated size, collected on upper stages, resulted in larger mode diameter, owing to the occurrence of filtration as well as impaction, and a shorter jet-to-plate distance, owing to the thickness of the filter. On the other hand, mass size distribution of roadside atmospheric particles measured with LPI using quartz fiber filters was similar to that measured with NanoMOUDI using aluminum foils. It is possible that the artifact of filtration is not important because of lower particle concentrations in the roadside atmosphere than in DEP. This experimental study of mass size distributions with various impactor types and substrate materials will enhance our understanding of the size distribution of chemical components, because impaction substrate material is restricted from methods of chemical analysis even though each substrate material has different collection characteristics.

An ordinary chondrite impactor for the Popigai crater, Siberia

With a diameter of ∼100 km, Popigai in Northern Siberia is the largest crater known in the Cenozoic. The concentrations in platinum group elements (PGE) were analyzed in twenty samples of homogeneous impact melt collected in the northwestern flank of the crater to identify the composition of the projectile. The method selected was preconcentration by NiS fire assay followed by inductively coupled plasma-mass spectrometry (ICP-MS). This technique measures all the PGE (except Os) and by using aliquots >10g, the results are highly reproducible. The major and trace element composition of the impact melt resembles that of gneissic lithologies of the Anabar shield, which are representative of the target rock. The PGE are enriched in the melt by factors of 3 to 14 compared to the main target lithology, but the meteoritic contamination is only around 0.2 wt.%. Using plots of elemental ratios such as Ru/Rh vs. Pt/Pd or Ru/Rh vs. Pd/Ir, the Popigai impactor is clearly identified as an ordinary chondrite and most likely l-chondrite. This study indicates that PGE elemental ratios allow discrimination of the type of impactor, even in the case of low meteoritic contamination. This study confirms that a significant fraction of the crater-forming projectiles presently documented could have an ordinary chondrite composition. Their probable source, the S-type asteroids, appears to form the majority of the bodies in the main asteroid belt and among Near Earth Objects (NEOs). The ordinary chondrite origin of the Popigai projectile supports an asteroidal origin for the late Eocene impacts as a plausible alternative to the comet shower scenario proposed by Farley et al. (1998).

The development of a novel high-dose pressurized aerosol dry-powder device (PADD) for the delivery of pumactant for inhalation therapy.

The performance of a novel dry powder inhaler designed to deliver exceptionally high doses was investigated using pumactant as a model powder. Pumactant (a synthetic lung surfactant consisting of a phospholipid mixture), with a 90th percentile particle size of 2.92 microm is highly cohesive, has a high moisture affinity (6.2% w/w at 45% RH), and is predominantly amorphous. The device (pressurized aerosol dry-powder delivery [PADD]) utilizes pressurized gas to aerosolize a powder bed from a reservoir and delivers it through a conventional mouthpiece. The influence of loaded dose on dry powder delivery and can pressure on aerosolization efficiency was investigated. Analysis of the delivered dose studies suggested a linear relationship between loaded dose and delivered dose (R(2) = 0.96, for loaded doses of 0-250 mg), with a delivery efficiency of 70%. Analysis of the aerosolization efficiency using a Marple Miller type impactor suggested fine particle fractions (particles with an aerodynamic diameter of <5 microm) of approximately 30% using canister pressures of 8-14 bars. These results indicate that the PADD device may be a useful tool in delivering high-dose medicaments, as a carrier-free formulation, to the deep lung.

The Effect of Environmental Temperature on the Shock Absorption Capacity of Running Shoes

0092 Various shock absorption systems (SAS) are used in contemporary running shoes to decrease lower extremity overuse injuries in runners. SAS typically include different polymeric materials with temperature sensitive biomechanical properties that may ultimately affect performance. PURPOSE: To determine the effect of temperature changes on the shock absorption capacity of four running shoes constructed with four different SAS. METHODS: Four brands of running shoes representing the most common SAS were chosen: Nike Air Triax (air-fllled units), Asics Gel Cumulus IV (gel-fllled units), Adidas Supernova (ethylene vinyl acetate or EVA), and Adidas A3 (polyurethane foam). One pair of each brand was tested (total of 4 pairs or 8 shoes). The shoes were frozen to −20° C using dry ice and gradually heated to +50° C in a portable incubator. Shoes were tested by an impactor following ASTM Standard F1614-99 at the following temperatures: −20°, −10°, 0°, +10°, +20°, +30°, +40°, +50° Celsius. The impact tester is a free-fall type impactor with instrumented force and position transducers. Output signals from both the force and position transducers were low-pass filtered at 500 Hz and sampled at 1500 Hz. From each data trial, the peak deceleration (G) was determined as an estimate of the shock absorption capacity. To assess the differences between the shoes, a repeated measures analysis of variance was used, the independent variables being the SAS and the temperature. RESULTS: There was a quadratic trend in the curves that differed between the shoe types (p< .001), indicating that for each SAS, the drop of the peak deceleration (G) with the increase of temperature was significant. There was also a significant overall difference when comparing the four different SAS over the temperature range. The polyurethane foam had much higher peak deceleration at cold temperatures than any of the other shoes tested. CONCLUSION: As the ambient temperature gets colder, the shock absorption capacity of the running shoes in the current study decreased. Temperature induced changes were most marked for the polyurethane foam SAS. These findings may have important clinical implications for individuals training in cold environments.

The Effect of Environmental Temperature on the Shock Absorption Capacity of Running Shoes

0092 Various shock absorption systems (SAS) are used in contemporary running shoes to decrease lower extremity overuse injuries in runners. SAS typically include different polymeric materials with temperature sensitive biomechanical properties that may ultimately affect performance. PURPOSE: To determine the effect of temperature changes on the shock absorption capacity of four running shoes constructed with four different SAS. METHODS: Four brands of running shoes representing the most common SAS were chosen: Nike Air Triax (air-fllled units), Asics Gel Cumulus IV (gel-fllled units), Adidas Supernova (ethylene vinyl acetate or EVA), and Adidas A3 (polyurethane foam). One pair of each brand was tested (total of 4 pairs or 8 shoes). The shoes were frozen to −20° C using dry ice and gradually heated to +50° C in a portable incubator. Shoes were tested by an impactor following ASTM Standard F1614-99 at the following temperatures: −20°, −10°, 0°, +10°, +20°, +30°, +40°, +50° Celsius. The impact tester is a free-fall type impactor with instrumented force and position transducers. Output signals from both the force and position transducers were low-pass filtered at 500 Hz and sampled at 1500 Hz. From each data trial, the peak deceleration (G) was determined as an estimate of the shock absorption capacity. To assess the differences between the shoes, a repeated measures analysis of variance was used, the independent variables being the SAS and the temperature. RESULTS: There was a quadratic trend in the curves that differed between the shoe types (p< .001), indicating that for each SAS, the drop of the peak deceleration (G) with the increase of temperature was significant. There was also a significant overall difference when comparing the four different SAS over the temperature range. The polyurethane foam had much higher peak deceleration at cold temperatures than any of the other shoes tested. CONCLUSION: As the ambient temperature gets colder, the shock absorption capacity of the running shoes in the current study decreased. Temperature induced changes were most marked for the polyurethane foam SAS. These findings may have important clinical implications for individuals training in cold environments.

Sampling E. coli and B. subtilis bacteria bioaerosols by a new type of impactor with a cooled impaction plate

Sampling E. coli and B. subtilis bacteria bioaerosols by a new type of impactor with a cooled impaction plate

New type of impactor with a cooled impaction plate for capturing PM2.5 and other aerosols

A new type of impactor with a cooled impaction plate was suggested by Lee and Kim (J. Aerosol Sci. 32 (2001) 107). The impactor performed well without coating material by using just the cooling impaction plate. However, the mechanism in the impactor was not elucidated by the experimental method. In this study, this kind of impactor specifically designed for capturing PM2.5 is presented. To understand the mechanism, two kinds of experiments were conducted. The experimental results show the condensation effect to be more effective than the thermophoresis effect in reducing the rebounce in the cooled plate impactor. Furthermore, this kind of impactor could be applied to PM2.5 classification.

Characterization of inhalation aerosols: a critical evaluation of cascade impactor analysis and laser diffraction technique.

Cascade impactor analysis is the standard technique for in vitro characterization of aerosol clouds generated by medical aerosol generators. One important reason for using this inertial separation principle is that drug fractions are classified into aerodynamic size ranges that are relevant to the deposition in the respiratory tract. Measurement of these fractions with chemical detection methods enables establishment of the particle size distribution of the drug in the presence of excipients. However, the technique is laborious and time consuming and most of the devices used for inhaler evaluation lack sufficient possibilities for automation. In addition to that, impactors often have to be operated under conditions for which they were not designed and calibrated. Particularly, flow rates through impactors are increased to values at which the flow through the nozzles is highly turbulent. This has an uncontrolled influence on the collection efficiencies and cut-off curves of these nozzles. Moreover, the cut-off value varies with the flow rate through an impactor nozzle. On the other hand, the high air flow resistances of most impactors are rather restricting to the attainable (fixed) inspiratory flow curves through these devices. Especially for breath actuated dry powder inhalers, higher flow rates and flow increase rates may be desirable than can be achieved in combination with a particular type of impactor. In this paper, the applicability of laser diffraction technology is evaluated as a very fast and highly reliable alternative for cascade impactor analysis. With this technique, aerodynamic diameters cannot be measured, but for comparative evaluation and development, comprising most in vitro applications, this is not necessary. Laser diffraction has excellent possibilities for automated recording of data and testing conditions, and the size classes are independent of the flow rate. Practical limitations can be overcome by using a special inhaler adapter which enables control of the inspiratory flow curve through the inhaler, analysis of the emitted fine particle mass fraction and pre-separation of large particles during testing of dry powder inhalers containing adhesive mixtures.

A multi-isotopic and trace element investigation of the Cretaceous–Tertiary boundary layer at Stevns Klint, Denmark – inferences for the origin and nature of siderophile and lithophile element geochemical anomalies

Os, Sr, Nd and Pb isotope data were collected from a profile across the Cretaceous–Tertiary (K–T) boundary layer at Stevns Klint, Denmark. ϵ Nd [ T=65 Ma] values from within the boundary layer (Fish Clay) are lower by ∼1 ϵ unit than those of the underlying Maastrichtian limestone and the overlying Danian chalk sequences. Systematic profile-upward changes of Pb, Sr and Os isotopic compositions and concentrations in the boundary layer cannot be accounted for by in situ growth of daughter products since the sedimentation of the Fish Clay. While Os, Nd and Pb isotopes indicate the admixing of less radiogenic components to the Fish Clay, Sr isotopes show elevated radiogenic values in the boundary layer, relative to the carbonate sequences beneath and above it. The sudden change in lithophile (e.g., Sr, Pb and Nd) isotope compositions at the base of the Fish Clay and profile-upward trends of 87Sr/ 86Sr and 206Pb/ 204Pb ratios towards those of the overlying Danian chalk are interpreted to reflect recovery from enhanced, acid rain-induced continental (local?) weathering input to the seawater. However, a continental crustal source is invalid for the siderophile element Os. In the light of evidence from chromium isotopes for a cosmic origin of the platinum group elements (PGEs) and certain moderately siderophile elements (Cr, Ni, Co, V) in K–T boundary sediments, including Stevns Klint [Shukolyukov and Lugmair, Science 282 (1998) 927–929], and supported by the finding of projectile debris [Bauluz et al., Earth Planet. Sci. Lett. 182 (2000) 127–136] and the occurrence of abundant Ni-rich spinel at many K–T sites [Robin et al., Nature 363 (1993) 615–617; Kyte, Nature 396 (1998) 237–239], we favor to explain the sudden drop of 187Os/ 188Os ratios from 0.210 to 0.160 at the K–T boundary to derive from global fall-out of extraterrestrial matter. The present 186Os/ 188Os ratio of 0.119836±0.000004 measured in the basal layer of the Fish Clay is within the uncertainty a chondritic value. We therefore exclude the possibility of a major contribution of PGEs to the sediment from iron meteorites. Chondrite-normalized (Ru/Ir) N ratios of ∼0.95±0.14 and (Os/Ir) N ratios of ∼0.93±0.14 in the Fish Clay cannot distinguish between abundance ratios of different types of chondrites, and strongly sub-chondritic (Pt/Ir) N ratios of ∼0.62±0.09 (2σ) suggest differential PGE remobilization through the sedimentary column (and consequently the alteration of inter-element ratios). PGEs and the moderately siderophile elements Cr, Ni, V, and Co form an elemental association with systematically upward-decreasing concentrations in the Fish Clay. Low Co/Ni ratios of ∼0.12 in the Fish Clay relative to values of ∼0.35 in the over- and underlying carbonate sequences support mixing of meteorite-derived (Co/Ni ∼0.05) and terrestrial upper mantle/crustal (Co/Ni >∼0.3) sources. While lithophile element isotope data indicate an increased continental crustal input to the Fish Clay at the K–T transition, the uncertainty with respect to possible post-depositional alteration of abundance patterns of siderophile and moderately siderophile elements – though not affecting the chondritic isotopic composition of Os – does not allow confirmation of indications from chromium isotopes for a carbonaceous (CV-type) meteorite as the preferred K–T impactor type by Shukolyukov and Lugmair [Science 282 (1998) 927–929].

Targeting the impactors: siderophile element signatures of lunar impact melts from Serenitatis

Highly siderophile element compositions of lunar impact melt breccias provide a unique record of the asteroid population responsible for large cratering events in the inner Solar System. Melt breccias associated with the 3.89 Ga Serenitatis impact basin resolve at least two separate impact events. KREEP-rich melt breccias representing the Apollo 17 poikilitic suite are enriched in highly siderophile elements (3.6–15.8 ppb Ir) with CI-normalized patterns that are elevated in Re, Ru and Pd relative to Ir and Pt. The restricted range of lithophile element compositions combined with the coherent siderophile element signatures indicate formation of these breccias in a single impact event involving an EH chondrite asteroid, probably as melt sheet deposits from the Serenitatis Basin. One exceptional sample, a split from melt breccia 77035, has a distinctive lithophile element composition and a siderophile element signature more like that of ordinary chondrites, indicating a discrete impact event. The recognition of multiple impact events, and the clear signatures of specific types of meteoritic impactors in the Apollo 17 melt breccias, shows that the lunar crust was not comprehensively reworked by prior impacts from 3.9 to 4.5 Ga, an observation more consistent with a late cataclysm than a smoothly declining accretionary flux. Late accretion of enstatite chondrites during a 3.8–4.0 Ga cataclysm may have contributed to siderophile element heterogeneity on the Earth, but would not have made a significant contribution to the volatile budget of the Earth or oxidation of the terrestrial mantle. Siderophile element patterns of Apollo 17 poikilitic breccias become more fractionated with decreasing concentrations, trending away from known meteorite compositions to higher Re/Ir and Pd/Pt ratios. The compositions of these breccias may be explained by a two-stage impact melting process involving: (1) deep penetration of the Serenitatis impactor into meteorite-free lower crust, followed by (2) incorporation of upper crustal lithologies moderately contaminated by prior meteoritic infall into the melt sheet. Trends to higher Re/Ir with decreasing siderophile element concentrations may indicate an endogenous lunar crustal component, or a non-chondritic late accretionary veneer in the pre-Serenitatis upper crust.

The effect of varying impaction plate temperature on impactor performance: experimental studies

This study concerns the effect of impaction plate temperature change on impactor performance. The impaction plate was cooled or heated with a thermoelectric module, and the temperature of the impaction plate was monitored by the thermocouple. The size of used particles ranged from 1 to 10 μm . Finally, a collection efficiency curve was obtained by employing a TSI Aerosizer. The results reveal that cooling the impaction plate makes the impactor collection efficiency higher and the re-entrainment lower. Therefore, cooling gives a more desirable collection efficiency curve. The increased adhesion effect on the impaction plate explains this. Based on the present investigations, cooling the impaction plate enhances impactor performance without using coating materials. A new type of impactor with a thermoelectrically cooled plate is demonstrated to be useful in this experimental study.

Evidence for a very high carbon/iridium ratio in the Tunguska impactor

Abstract— We have measured excess Ir and depletion of 14C, two independent indicators of cosmic material, in peat cores from the central Tunguska impact site. Both Ir and 14C show pronounced anomalies in the same stratigraphical depth interval. We have estimated an integral deposition of nonradioactive cosmogenic C of 6.8 ± 1.0 mg C cm−2, and an integrated Ir deposition of 5.9 ± 1.2 pg Ir cm−2. The very high C/Ir ratio and a deduced δ13C value of +55 ± 10% relative to V Pee Dee Belemnite (VPDB) of the impactor material found in this study points towards a cometary type impactor, rather than a chondritic or achondritic asteroidal type impactor.

Damage to rabbit femoral articular cartilage following direct impacts of uniform stresses: an in vitro study

Objective. To determine the acute gross and histologic damage resulting to femoral cartilage from an in vitro direct impact of uniform stress. Design. Gross and histologic evaluations were performed on rabbit femoral condyles impacted by a drop-tower device. Background. It is thought that impacts above a given threshold stress may initiate post-traumatic arthritis. The extent of damage following impacts of specific stress has not been previously studied. Methods. 12 New Zealand White rabbit medial femoral condyles were divided into three groups by impact type and magnitude. A drop tower was used to strike the femoral condyle with a flat impactor, or with a custom contoured impactor. Gross and histological grades were given depending on the depth and number of fissures and cracks in the impacted condyle. Results. The degree of damage correlated best with the type of impactor used and with the impact force; correlation between damage and impact stress was less significant. Contoured impactors tended to produce superficial fibrillation, while flat impactors tended to produce deep cracks. Impact forces above 500 N tended to create more severe damage than impact forces below 500 N. Subchondral bone remained intact in all cases and deep cartilage damage did not occur without disruption of more superficial layers. Poor correlation was found between damage as graded by gross examination versus damage graded histologically. Conclusions. Acute damage corresponds best with type of impactor and impact force, and not as well with impact stress. Micro structural injuries may be present in the absence of gross findings. Relevance Post-traumatic arthritis is a disabling disease thought to occur when a blow of stress above a given threshold is delivered to articular cartilage. Current animal models of post-traumatic arthritis are unable to characterize the impact stress applied to an articular surface. This study examines grossly and histologically the structural damage occurring as a result of impacts of given stress and force.

Sample collection and preparation for analysis of airborne particulate matter by total reflection X-ray fluorescence spectrometry

The steady interest in clarifying the relevance of atmospheric particles for health risks requires fast and easy to handle methods for the collection and characterization of airborne particulate matter. For the present study, airborne dust was collected by filtration as well as by impaction with a six stage Berner type impactor. Filtration was performed with cellulose nitrate filters, and in the Berner type impactor a thin spray film was employed as collection medium. The exposed portions of both materials were punched out and digested. Three different digestion techniques were studied and intercompared: open digestion (OD) with nitric acid and hydrogen peroxide, high pressure acid digestion (HPA), and cool plasma ashing (CPA). Decomposition by CPA showed highest reliability and practicability for these materials. After digestion of the samples, the residues were dissolved with nitric and hydrochloric acid, mixed with an internal standard element and analyzed by Total Reflection X-Ray Fluorescence Spectrometry (TXRF). Due to the high detection power of TXRF, the sampling time could be reduced to less than 1 h. By this means it was possible to collect and analyze several samples successively during one day. A diurnal variation was established with both sampling systems in parallel.

Optimization of the operation conditions of an Andersen-Cascade impactor and the relationship to centrifugal adhesion measurements to aid the development of dry powder inhalations

The standardization of the operation conditions of an Andersen-Cascade impactor (Mark II), based on the physical relationship between adhesion and aerodynamic particle behaviour, has been undertaken using the Serevent® Disk-haler. In this case, the drug (Salmeterol xinafoate) is primarily adhered to a carrier material (lactose monohydrate), and thus the standard operation procedure to use this type of impactor had to be modified. For the modified procedure, operating conditions such as air flow rate, thickness of a silicon coat of the impaction plates and drug loading were optimized, bearing in mind the findings reported in the literature about the relationship between adhesion and impaction on plates. For this particular drug, the optimal thickness of the silicon film was found to be 3.75 μm, and the drug loading should not exceed 400μg. Although any air flow velocity between 20 and 60 1 min −1 gave a physically correct aerodynamic particle size for this drug and the chosen inhaler device, a maximum amount of drug was released from the device only applying flow rates between 50 and 60 1 min −1. Four different industrially manufactured Serevent® batches were studied under these optimized operation conditions. Using centrifugal adhesion force measurements, the median adhesion force between Salmeterol xinafoate particles and lactose monohydrate carrier particles was established and linked to the aerodynamic behaviour of the drug using the Cascade impactor. The median adhesion force ( F ad) and the mass median aerodynamic diameter (MMAD) were found to be directly proportional. Statistical analysis, however, indicated that the differences in F ad and MMAD were not significant between the tested batches. The procedure established that the formulation had been produced with high accuracy and reproducibility. The sensitivity of the adhesion force measurements to variability in the manufacturing process would allow an in-process control of the mixture and could help to assure this high standard.

Choice of a suitable material for construction of a battelle type impactor to minimize systematic errors in sampling of airborne dust

Systematic errors can occur when airborne dust is sampled with an impactor for subsequent element analysis. As could be shown, blank values, collection losses and memory effects are caused by the impactor and the material it is made of. Four different materials were chosen to build up a two-stage Battelle type impactor: Makrolon®, titanium, aluminium and stainless steel. The latter was applied without and with a coating of TiN. Air dust was collected on Vaseline® coated impaction plates and directly analyzed by total reflection X-ray fluorescence (TXRF). Up to 15 elements were determined simultaneously after internal standardization. Blank values arising from the impactor walls in contact with the gas flow were measured by sampling air from a clean bench. Relative collection losses were determined by sampling ambient air with two impactors in parallel and by comparing the two sets of results. Memory effects were measured by first collecting airborne particulates and then, after having replaced the impaction plates, pulling air through the impactor in a clean bench. The three effects led to relative systematic errors of a few % up to several 10% depending on element and impactor material. Stainless steel causing the largest errors has to be considered the least suitable material, even if coated with TiN. Aluminium led to moderate systematic deviations. Only titanium and Makrolon® were proven to be widely suitable impactor materials, the latter one, however, only when short sampling periods are applied.

New vertebral body impactors for posterolateral decompression of burst fracture.

A new type of impactor was developed to decompress the anterior aspect of the vertebral body. These instruments are particularly useful for cases of burst fracture.

Evaluation of the applicability of the MOUDI impactor for aerosol collections with subsequent multielement analysis by PIXE

The micro-orifice uniform deposit impactor (MOUDI) is an 8-stage impactor with cut-sizes down to 0.056 μm and which allegedly provides uniform aerosol deposits for the various stages. In the present study it was examined how uniform the aerosol deposits really are for each impaction plate and whether the uniformity is sufficient for a straightforward PIXE analysis. This was done by collecting several samples of ambient aerosol with the MOUDI and by determining the deposition pattern of various elements on the foils through a linear PIXE scan across each impaction foil. It was found that the deposits are far from uniform at the millimeter level for the stage numbers up to 6. Despite this, concentration data can easily be obtained by PIXE from such samples, provided that the analyzed area is carefully selected and appropriate correction factors for the nonuniformity are employed. Some size distribution data are presented. A comparison is also made of the size distribution data and detection limits that result from employing the MOUDI in combination with PIXE with those obtainable by PIXE analysis of some other types of cascade impactors.

Simple nitric acid dissolution method for electrothermal atomic absorption spectrometric analysis of atmospheric aerosol samples collected by a berner-type low-pressure impactor

The aim of this study was to develop a simple dissolution method for atmospheric aerosol samples collected using a Berner impactor. Particular care was taken to ensure that the procedural blank contributions were as low as possible for the elements investigated. The impactor samples were treated for two or three 20 min periods with 0.2 mol l–1 nitric acid in polystyrene test-tubes in an ultrasonic bath at 50 °C. Electrothermal atomic absorption spectrometry (ETAAS) with a graphite furnace was used to determine 14 elements: Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn. With the exception of Zn, for which a platform was used, all analytes were atomized off the wall of the graphite tube. The blank values for Al, Cd, Cu, Mn, Ni, Pb and V were found to be at or below the detection limits of the method. The blank values for Ca, Fe, K, Mg, Na and Zn varied between 0.5 and 3 µg l–1 but Cr showed an unsuitably high blank of 8 µg l–1. The dissolution method was tested on the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1648 Urban Particulate and the recoveries were found to be 80–93% for Pb, Zn, Cd and Cu. The least recoverable elements in this matrix were Al, Cr, Fe, K and Na, with recoveries between 20 and 44%. A prolonged dissolution time had only a minor effect on the recoveries. Additional tests involved the analysis of ambient aerosol samples, collected with a cascade impactor, by both ETAAS and instrumental neutron activation analysis (INAA), with the latter technique providing the reference values. Six elements (Al, Cu, Mg, Mn, Na and V) were measured by both techniques. Compared with the NIST material, the fine particle (equivalent aerodynamic cut-off diameter<2 µm) impactor samples clearly showed better recoveries for Cu (91%), Mn (90%), Na (102%) and V (96%). Similar or even better recoveries are also expected for fine particle Cd, Zn and Pb, which were not measured in our INAA procedure but exhibited the highest recoveries for the NIST material. For Al, on the other hand, the results from the impactor samples were similar to those for the NIST material and there was a trend that the recoveries were decreasing with increasing particle size, because of incomplete dissolution of the soil dust particles and a lower ability of the coarser particles to form a suspension. Moreover, coarse particle Al was recovered mostly as particulate material. It is assumed that our dissolution method is valid for measuring fine particle Cd, Cu, Mg, Mn, Na, Pb, V and Zn in ambient aerosol samples collected on polycarbonate film by various types of impactors.

Characterization of long-lived radioactive dust in uranium mill operations.

The characteristics of long-lived radioactive dust clouds generated in several mechanical and physiochemical operations in a uranium mill have been investigated. The study consisted of the determination of dust size distribution and of the size distribution of radionuclides associated with particulate matter in the size range less than 0.1 to 26 microns. Experiments were conducted by using two different types of cascade impactors operating at different sampling flow rates. Radionuclide identification was done by using alpha-spectrometry. Long- and short-lived radionuclides were identified in dust samples. The characteristics of the dust clouds depended on the mill operation, such as crushing (vibrating grizzly, jaw crusher, cone crusher); screening; ore transportation; grinding; acid leaching; counter-current decantation; yellow cake precipitation and drying; and yellow cake packaging. In addition, other dust and radioactivity measurements have been carried out.