Aerosol Solubility Research Articles

The solubility and deposition flux of East Asian aerosol metals in the East China Sea: The effects of aeolian transport processes

Aerosol dissolvable metals are considered to be readily bioaccessible so that their input would influence the growth and composition of marine phytoplankton and affect elemental cycling globally. However, it is highly challenging to measure or estimate reliable deposition fluxes of aerosol dissolvable metals in the ocean partially due to the impacts of complicated processes involved in pre- and post-deposition of aerosols. We have collected lithogenic dust from major Chinese deserts and size-fractionated aerosols from the East China Sea (ECS) to study the variations of their dissolvable metals by using three operationally defined leaching protocols (ultrapure water, buffer, and Berger leaches). We have systematically investigated the changes of the distribution patterns of the metals to evaluate the potential impacts of the transport processes on the flux estimates of different elements. In addition to the extremely high solubilities observed for anthropogenic type elements, we found variations for solubilities of lithogenic type elements (Ti, Al, Fe) increase with increasing sizes by the three leaching treatments. Without knowing the size specific information (mass and solubility), our observations indicate that the deposition fluxes of lithogenic type elements would be significantly overestimated. Compared with the solubility of the desert dust, we found that all solubilities for lithogenic type elements in the largest aerosols were significantly enhanced. For example, the Fe solubilities increased up to 68, 6, and 3 folds for ultrapure water, buffer, and Berger treatments, respectively. Attributed to the difference of the impacts of the transport processes in different regions, the extent of the enhancement would be region specific. Comparing some other recent laboratory studies, we argue that the solubilities obtained by buffer and Berger leaches are more realistic to represent aerosol solubility in the ocean than ultrapure water leach. It would be essential to carry out similar field studies in other regions as this study to obtain region specific parameters of dissolvable aerosol metals to achieve better global modeling estimates on the fluxes of dissolvable aerosol metals in the ocean.

Experimental study of single-bubble behavior containing aerosol during pool scrubbing

During a severe accident (SA) in a nuclear power plant, the damaged core releases fission products (FPs). Pool scrubbing is a filtering process to avoid the release of radioactive aerosols into the environment, and its effects have already been modeled and implemented in some SA codes such as MELCOR. However, the effect of aerosols on bubble motion is not defined in this code's model. Therefore, in this study, we visualized the effect of aerosol on the bubble interface via the measurement of the bubble aspect ratio and rising velocity. High-speed videography enabled us to clearly record the effect of aerosol solubility on bubble shape. We found that the solubility of the aerosol inside the bubble – a factor not considered in the MELCOR code – affected the bubble shape and rising velocity. Moreover, soluble aerosols tended to affect bubbles in a manner similar to surfactants. The internal velocity of an oil droplet – a simulated air bubble – was measured using a PIV method. Using image processing, we obtained the interface velocity from the PIV data. The comparison of the experimentally obtained interface velocity and the theoretical value calculated from the equation in MELCOR suggests that MELCOR's internal flow can qualitatively predict the characteristics of internal bubble flow. Additionally, we combined the bubble visualization data and the MELCOR internal bubble flow model and calculated the decontamination factor (DF) for a single-bubble. The results show that the difference in the DF is due to solubility of aerosol, which is caused by the bubble shape and rising velocity.

Atmospheric deposition fluxes over the Atlantic Ocean: a GEOTRACES case study

Abstract. Atmospheric deposition is an important source of micronutrients to the ocean, but atmospheric deposition fluxes remain poorly constrained in most ocean regions due to the limited number of field observations of wet and dry atmospheric inputs. Here we present the distribution of dissolved aluminium (dAl), as a tracer of atmospheric inputs, in surface waters of the Atlantic Ocean along GEOTRACES sections GA01, GA06, GA08, and GA10. We used the surface mixed-layer concentrations of dAl to calculate atmospheric deposition fluxes using a simple steady state model. We have optimized the Al fractional aerosol solubility, the dAl residence time within the surface mixed layer and the depth of the surface mixed layer for each separate cruise to calculate the atmospheric deposition fluxes. We calculated the lowest deposition fluxes of 0.15±0.1 and 0.27±0.13 g m−2 yr−1 for the South and North Atlantic Ocean (>40∘ S and >40∘ N) respectively, and the highest fluxes of 1.8 and 3.09 g m−2 yr−1 for the south-east Atlantic and tropical Atlantic Ocean, respectively. Overall, our estimations are comparable to atmospheric dust deposition model estimates and reported field-based atmospheric deposition estimates. We note that our estimates diverge from atmospheric dust deposition model flux estimates in regions influenced by riverine Al inputs and in upwelling regions. As dAl is a key trace element in the GEOTRACES programme, the approach presented in this study allows calculations of atmospheric deposition fluxes at high spatial resolution for remote ocean regions.

The residence times of trace elements determined in the surface Arctic Ocean during the 2015 US Arctic GEOTRACES expedition

Data collected during the US Arctic GEOTRACES expedition in 2015 are used to estimate the mean residence time of dissolved trace elements (Fe, Mn, Ni, Cd, Zn, Cu, Pb, V) in surface water with respect to atmospheric deposition. The calculations utilize mixed layer trace element (TE) inventories, aerosol solubility determinations, and estimates of the atmospheric trace element flux into the upper ocean. The trace element flux is estimated by the product of the 7Be flux (determined by the ocean 7Be inventory) and the TE/7Be ratio of aerosols. This method has been established elsewhere and is tested here by comparing 7Be-derived TE flux to the measured TE accumulation in recently deposited snow. Given the variability in snow and aerosol TE concentration observed over the expedition, and the limited timescale of the observations, agreement between the two methods is reasonable. While there are assumptions in these calculations, the distribution of residence times with respect to atmospheric input across the expedition track informs us of additional sources or sinks for each element. The residence time of dissolved Fe was ~ 20–40 y for most stations. However, several stations that display a longer, oceanographically inconsistent apparent Fe residence time of ~300–500 years are likely influenced by additional input from the Transpolar Drift (TPD), which has been shown to convey shelf water properties to the central Arctic. This was seen for Cu, Ni and Zn as well. The flux of Fe delivered by the TPD was ~ 10 nmol/m2/d for these stations, an order of magnitude greater than the soluble atmospheric input. On the other hand, V and Pb show a decrease in the apparent residence times within TPD water, suggesting removal of these elements from the source region of the TPD. For Mn, there is no obvious trend in residence time among the stations; however the apparent residence time (400–1400 y) is significantly greater than the ~20 y calculated for atmospheric input elsewhere, signifying appreciable input from other sources. It has been suggested that about 90% of Mn input to the Arctic Ocean originates from Arctic rivers, shelf sediments, and coastal erosion. Results here suggest a flux from these sources of ~30 nmol/m2/d which is significantly greater than the atmospheric input of Mn in the Arctic.

Hail suppression effectiveness for varying solubility of natural aerosols in water

This sensitivity study examined the impact of natural aerosol on the results obtained by numerical cloud seeding experiments focused on hail suppression on the ground. A main concern was investigating the effects of the solubility of the natural aerosol on unseeded and seeded cloud simulations. A numerical model with a two-moment bulk microphysical scheme was used for this purpose. The numerical model calculated the mass and number concentrations of the following seven microphysical categories: cloud water, rain, cloud ice, snow, graupel, frozen raindrops and hail. The solubility values of the natural aerosol in water were varied, and the rain and hail production in clouds and the corresponding surface precipitation were analysed in unseeded and seeded cases. The effectiveness of hail suppression on the ground is reduced in atmospheric environments with natural aerosols that are less soluble in water. A low solubility of natural aerosol in water can result in overseeding. The sensitivity study showed that environments with predominantly soluble aerosol particles (such as sodium chloride) were suitable for hail suppression with a simultaneous increase in surface rain.

Connecting the solubility and CCN activation of complex organic aerosols: a theoretical study using solubility distributions

Abstract. We present a theoretical study investigating the cloud activation of multicomponent organic particles. We modeled these complex mixtures using solubility distributions (analogous to volatility distributions in the VBS, i.e., volatility basis set, approach), describing the mixture as a set of surrogate compounds with varying water solubilities in a given range. We conducted Köhler theory calculations for 144 different mixtures with varying solubility range, number of components, assumption about the organic mixture thermodynamics and the shape of the solubility distribution, yielding approximately 6000 unique cloud condensation nucleus (CCN)-activation points. The results from these comprehensive calculations were compared to three simplifying assumptions about organic aerosol solubility: (1) complete dissolution at the point of activation; (2) combining the aerosol solubility with the molar mass and density into a single effective hygroscopicity parameter κ; and (3) assuming a fixed water-soluble fraction ϵeff. The complete dissolution was able to reproduce the activation points with a reasonable accuracy only when the majority (70–80%) of the material was dissolved at the point of activation. The single-parameter representations of complex mixture solubility were confirmed to be powerful semi-empirical tools for representing the CCN activation of organic aerosol, predicting the activation diameter within 10% in most of the studied supersaturations. Depending mostly on the condensed-phase interactions between the organic molecules, material with solubilities larger than about 0.1–100 g L−1 could be treated as soluble in the CCN activation process over atmospherically relevant particle dry diameters and supersaturations. Our results indicate that understanding the details of the solubility distribution in the range of 0.1–100 g L−1 is thus critical for capturing the CCN activation, while resolution outside this solubility range will probably not add much information except in some special cases. The connections of these results to the previous observations of the CCN activation and the molecular properties of complex organic mixture aerosols are discussed. The presented results help unravel the mechanistic reasons behind observations of hygroscopic growth and CCN activation of atmospheric secondary organic aerosol (SOA) particles. The proposed solubility distribution framework is a promising tool for modeling the interlinkages between atmospheric aging, volatility and water uptake of atmospheric organic aerosol.

U-238 Content in Urine of Uranium Miners and Its Modelled Values

U-238 Content in Urine of Uranium Miners and Its Modelled ValuesAbstract Number:1674AbstractThe study is based on measurements of U-238 in urine among 88 active uranium miners using high-resolution inductively coupled mass spectrometry method. 100 samples of urine were collected. Daily levels are in the range of 0.1 – 8.6 mBq with the mean of 3.3 and standard deviation of 1.3 among hewers and with the mean of 2.1 and standard deviation of 1.1 among other professions. The experimental data are compared to those estimated from U-238 inhalation intake derived from long lived alpha activities monitored by personal ALGADE dosimeters and calculated excretion functions according to software IMBA. The fit between observed and calculated data is evaluated for different parameters like isotopic composition, particle size, or solubility of aerosol in the lungs. It was proven that biokinetics models lead to higher then excreted values. Although it may be caused by uncertainties connected with U-238 urine content. The correlations between observed and calculated are about 0.4 among hewers and 0.7 among others professions. Lower correlation for hewers is caused by some outlying long lived alpha intakes. The uncertainty of exposure data is assessed as well taking into account the temporal pattern of daily exposures, profession and age of miners. The study is supported by the European Commission and the Czech Ministry of Education (project DOREMI, GA 249689, 7G13001).

Developments in the CSU-RAMS Aerosol Model: Emissions, Nucleation, Regeneration, Deposition, and Radiation

AbstractThe Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS) has undergone development focused on improving the treatment of aerosols in the microphysics model, with the goal of examining the impacts of aerosol characteristics, scavenging, and regeneration processes, among others, on precipitation processes in clouds ranging from stratocumulus to deep convection and mixed-phase orographic clouds. Improvements in the representation of aerosols allow for more comprehensive studies of aerosol effects on cloud systems across scales. In RAMS there are now sub- and supermicrometer modes of sulfate, mineral dust, sea salt, and regenerated aerosol. All aerosol species can compete for cloud droplet nucleation, and they are regenerated via hydrometeor evaporation. A newly applied heterogeneous ice nuclei parameterization accounts for deposition nucleation and condensation and immersion freezing of aerosols greater than 0.5-μm diameter. There are also schemes for trimodal sea salt emissions and bimodal dust lofting that are functions of wind speed and surface properties. Aerosol wet and dry deposition accounts for collection by falling hydrometeors as well as gravitational settling of aerosols on water, soil, and vegetation. Aerosol radiative effects are parameterized via the Mie theory. An examination of the simulated impact of aerosol characteristics, sources, and sinks reveals mixed sensitivity among cloud types. For example, reduced aerosol solubility has little impact on deep convection since supersaturations are large and nearly all accumulation-mode aerosols activate. In contrast, reduced solubility results in reduced aerosol activation in precipitating stratocumulus. This leads to lower cloud droplet concentration, larger droplet size, and more efficient warm rain processes.

Evaluation of commonly used filter substrates for the measurement of aerosol trace element solubility

The published literature describing aerosol trace element fractional solubility measurements is characterized by a wide range of observed fractional solubilities. Whereas some of this variability is derived from natural differences in the chemical characteristics of the aerosol source material, the use of different sample collection and processing protocols by the scientific community has also confounded efforts to understand aerosol solubility. Bulk aerosol samples were collected at a coastal site over a nine‐month period and used to assess the influence of filter material on aerosol solubility measurements. Two hundred samples were extracted with ultrapure deionized water and focused on the solubility of ten trace elements (Al, P, Ti, V, Mn, Fe, Ni, Cu, Zn, and Pb) of interest to the GEOTRACES program. Aerosol samples were collected on eight different filter types and extracted using a flow‐through “instantaneous” extraction method. In many cases, the operationally defined aerosol trace element solubility differed depending on filter type. Major anion concentrations and trace element fractional solubility were found to differ 58% and 60% of the time, respectively. Filter blank concentrations are also reported for the various filter types. This work, in conjunction with the 2008 GEOTRACES Aerosol Intercalibration study, should aid the design of future research efforts by the wider marine aerosol community and allow better comparisons among published data.

A closure study of cloud condensation nuclei in the North China Plain using droplet kinetic condensational growth model

Abstract. Aerosol size distribution and cloud condensation nucleus (CCN) number concentration were measured in the North China Plain from 31 December 2009 to 20 January 2010. The CCN closure study was performed using these data and droplet kinetic condensational growth model. The calculated CCN concentration with the assumption of pure ammonium sulfate aerosol is 40–140% higher than that observed for the supersaturations in this study. A sensitivity test on aerosol solubility and mixing state indicates that 0.2–0.5 mass fraction of ammonium sulfate for internal mixture can lead to a ratio of 0.82–1.30 for the calculated to observed CCN concentrations, and that 0.4–0.7 mass fraction of ammonium sulfate for external mixture results in a ratio of 0.74–1.25 in the North China Plain during the time period of the field observations, suggesting that a relatively simple scheme may be used for CCN prediction in climate models for this region. Finally, we compare the calculated CCN concentrations from the kinetic condensational growth model and the equilibrium model. The kinetic condensational growth model can simulate droplet growth in a time period under a certain supersaturation, while the equilibrium model only predicts whether a certain aerosol can be activated as CCN under that supersaturation. The CCN concentration calculated with the kinetic model is higher than that with the equilibrium model at supersaturations of 0.056% and 0.083%, because some particles that are not activated from the equilibrium point-of-view can grow large enough to be considered as CCN in the kinetic model. While at a supersaturation of 0.17%, CCN concentration calculated with the kinetic model is lower than that with the equilibrium model, due to the limitation of droplet kinetic growth. The calculated CCN concentrations using the kinetic model and the equilibrium model are the same at supersaturations of 0.35% and 0.70%.

Effects of Aerosol Solubility and Regeneration on Mixed-Phase Orographic Clouds and Precipitation

Abstract A detailed bin aerosol-microphysics scheme has been implemented into the Weather Research and Forecast Model to investigate the effects of aerosol solubility and regeneration on mixed-phase orographic clouds and precipitation. Two-dimensional simulations of idealized moist flow over two identical bell-shaped mountains were carried out using different combinations of aerosol regeneration, solubility, loading, ice nucleation parameterizations, and humidity. The results showed the following. 1) Pollution and regenerated aerosols suppress the riming process in mixed-phase clouds by narrowing the drop spectrum. In general, the lower the aerosol solubility, the broader the drop spectrum and thus the higher the riming rate. When the solubility of initial aerosol increases with an increasing size of aerosol particles, the modified solubility of regenerated aerosols reduces precipitation. 2) The qualitative effects of aerosol solubility and regeneration on mixed-phase orographic clouds and precipitation are not affected by different ice nucleation parameterizations. 3) The impacts of aerosol properties on rain are similar in both warm- and mixed-phase clouds. Aerosols exert weaker impact on snow and stronger impact on graupel compared to rain as graupel production is strongly affected by riming. 4) Precipitation of both warm- and mixed-phase clouds is most sensitive to aerosol regeneration, then to aerosol solubility, and last to modified solubility of regenerated aerosol; however, the precipitation amount is mainly controlled by humidity and aerosol loading.

Global estimates of mineral dust aerosol iron and aluminum solubility that account for particle size using diffusion‐controlled and surface‐area‐controlled approximations

Mineral aerosol deposition is recognized as the dominant source of iron to the open ocean and the solubility of iron in the dust aerosol is highly variable, with measurements ranging from 0.01–80%. Global models have difficulty capturing the observed variations in solubility, and have ignored the solubility dependence on aerosol size. We introduce two idealized physical models to estimate the size dependence of mineral aerosol solubility: a diffusion‐controlled model and a surface‐area‐controlled model. These models produce differing time‐ and space‐varying solubility maps for aerosol Fe and Al given the dust age at deposition, size‐resolved dust entrainment fields, and the aerosol acidity. The resulting soluble iron deposition fluxes are substantially different, and more realistic, than a globally uniform solubility approximation. The surface‐area‐controlled solubility varies more than the diffusion‐controlled solubility and better captures the spatial pattern of observed solubility in the Atlantic. However, neither of these two models explains the large solubility variation observed in the Pacific. We then examine the impacts of spatially variable, size‐dependent solubility on marine biogeochemistry with the Biogeochemical Elemental Cycling (BEC) ocean model by comparing the modeled surface ocean dissolved Fe and Al with observations. The diffusion‐based variable solubility does not significantly improve the simulation of dissolved Fe relative to a 5% globally uniform solubility, while the surface‐area‐based variable solubility improves the simulation in the North Atlantic but worsens it in the Pacific and Indian Oceans.

Uptake of acid pollutants by mineral dust and their effect on aerosol solubility

Abstract Due to the implications caused by mineral dust and sea-salt heterogeneous reactions with SO 2 , NO x and NH 3 derivatives, this study aims to understand the interaction between gaseous and particulate phases; PM10 and PM2.5, in dust-rich and dust-poor environments. During dust outbreaks, the increase in PM10 and PM2.5 mass concentrations by 80 and 75%, respectively, was accompanied with approximately 30% decrease in water soluble inorganic ions. However, nitrate ion concentration, which increased by 36% during dust-rich episodes, was correlated with a 96% increase in gaseous HONO concentration. This implies a significant impact of dust storms on the tropospheric NO 2 to HONO conversion and consequently the formation of nitrate in PMs. Products of the reaction between HONO and mineral dust render atmospheric aerosols more soluble and consequently higher nitrogen deposition fluxes were calculated.

Effects of Aerosol Solubility and Regeneration on Warm-Phase Orographic Clouds and Precipitation Simulated by a Detailed Bin Microphysical Scheme

Abstract This study evaluates the possible impact of aerosol solubility and regeneration on warm-phase orographic clouds and precipitation. The sensitivity evaluation is performed by simulating cloud formation over two identical 2D idealized mountains using a detailed bin microphysical scheme implemented into the Weather Research and Forecasting model (WRF) version 3. The dynamics, thermodynamics, topography, and microphysical pathways were designed to produce precipitating clouds in a linear hydrostatic mountain wave regime. The cloud over the second mountain is affected by regenerated aerosols advected from the cloud over the first mountain. Effects of aerosol solubility and regeneration were investigated with surface relative humidity of 95% and 85% for both clean and polluted background aerosol concentrations. Among the findings are the following: 1) The total number of cloud drops decreases as the aerosol solubility decreases, and the impacts of aerosol solubility on cloud drops and precipitation are more significant in polluted clouds than in clean clouds. 2) Aerosol regeneration increases cloud drops and reduces the precipitation by 2%–80% in clouds over the second mountain. Regenerated aerosol particles replenish one-third to two-thirds of the missing particles when regeneration is not considered. 3) Different size distributions of regenerated aerosol particles have negligible effect on clouds and precipitation except for polluted clouds with high aerosol solubility. 4) When the solubility of initial aerosol particles decreases with an increasing size of aerosol particles, the modified solubility of regenerated aerosol particles increases precipitation over the second mountain.

The influence of aerosol particle number and hygroscopicity on the evolution of convective cloud systems and their precipitation: A numerical study based on the COPS observations on 12 August 2007

The 3D cloud model DESCAM-3D with bin resolved microphysics for ice, water and aerosol particles is used to study the role of particles on the evolution of summertime mid-level convective clouds and the subsequent precipitation during the COPS field campaign which occurred at mid-latitude near the French/German border in summer 2007. Using a 3D grid resolution of 250 m, DESCAM-3D, is able to simulate well the dynamical, cloud and precipitation features of the convective cloud system observed during the afternoon of the 12th August. This mid-level convective system was dominated by warm-phase microphysics. The simulated convective system led to a 1.5 h long lasting precipitation event in agreement with the radar observations. The results of the fine numerical scale compare well with the high resolved radar reflectivities of the LaMP X-band radar and the DLR-Poldirad radar. The prediction of the liquid hydrometeor spectra allows a detailed calculation of the cloud radar reflectivity. In order to better understand the role of aerosol particles on cloud evolution and precipitation formation, several sensitivity studies were performed by modifying aerosol number concentration as well as their physico-chemical properties. Drastic changes in the aerosol solubility lead to a variation in precipitation on the order of 10% for the same convective case. In contrast, changes in the aerosol number concentrations can lead to a variation in total precipitation of up to 30%. Hence, the role of changes in aerosol number concentrations is more important than changes in particle solubility for this case of continental mid-level convection at mid-latitude. A subsequent analysis of the in-cloud microphysics revealed that in-cloud properties are modified significantly in all scenarios. Key parameter is the supersaturation whose magnitude influences both cloud microphysics (cloud droplet and rain drop formation) as well as cloud thermodynamics and cloud dynamics. Furthermore, supersaturation can remain quite low in polluted clouds reducing strongly the release of latent heat and, thus, the intensity of the convective dynamics. As much as a quarter of the polluted cloud volume was found to be subsaturated in this case whereas it was smaller in the continental or clean environments.

Aerosol iron solubility in a semi-arid region: temporal trend and impact of anthropogenic sources

Asystematic 1-yr chemical data for the fine mode (PM2.5) air-borne particulate matter, collected from a high-altitude site (Mt. Abu, 22.7◦N, 74.6◦E, 1680 m asl) in a semi-arid region of western India, reveal characteristic temporal variability in the abundance of mineral dust and fractional solubility of aerosol Fe (referred as water-soluble Fe). A notable feature of the data is seen from an inverse relationship between aerosol Fe (range: 50–915 ng m−3) and fractional Fe solubility (range: 0.06–16.1%). A significant increase in the solubility of iron, during wintertime, is also marked by a uniform decrease in the mass fraction of mineral dust. These observations suggest that the advective transport of pollutants and Fe derived from combustion sources is one of the possible causes for the enhanced solubility of iron over a semi-arid region in western India. The relative dominance of anthropogenic sources, during wintertime, is also supported by a two to threefold increase in NH4+ and SO42− as well as enrichment of heavy metals in PM2.5 (ascertained from Pb/Al and Cd/Al ratios).

Iron solubility driven by speciation in dust sources to the ocean

Particulate aerosols are thought to be the primary source of iron to the oceans, but the factors determining their solubility, and thus bioavailability, are unclear. X-ray absorption analysis reveals that speciation controls the solubility of iron in three large sources of aerosol iron. Although abundant in the Earth’s crust, iron is present at trace concentrations in sea water and is a limiting nutrient for phytoplankton in approximately 40% of the ocean1,2. Current literature suggests that aerosols are the primary external source of iron to offshore waters, yet controls on iron aerosol solubility remain unclear3,4. Here we demonstrate that iron speciation (oxidation state and bonding environment) drives iron solubility in arid region soils, glacial weathering products (flour) and oil combustion products (oil fly ash). Iron speciation varies by aerosol source, with soils in arid regions dominated by ferric (oxy)hydroxides, glacial flour by primary and secondary ferrous silicates and oil fly ash by ferric sulphate salts. Variation in iron speciation produces systematic differences in iron solubility: less than 1% of the iron in arid soils was soluble, compared with 2–3% in glacial products and 77–81% in oil combustion products, which is directly linked to fractions of more soluble phases. We conclude that spatial and temporal variations in aerosol iron speciation, driven by the distribution of deserts, glaciers and fossil-fuel combustion, could have a pronounced effect on aerosol iron solubility and therefore on biological productivity and the carbon cycle in the ocean.

METHODS USED TO CALCULATE DOSES RESULTING FROM INHALATION OF CAPSTONE DEPLETED URANIUM AEROSOLS

The methods used to calculate radiological and toxicological doses to hypothetical persons inside either a U.S. Army Abrams tank or Bradley Fighting Vehicle that has been perforated by depleted uranium munitions are described. Data from time- and particle-size-resolved measurements of depleted uranium aerosol as well as particle-size-resolved measurements of aerosol solubility in lung fluids for aerosol produced in the breathing zones of the hypothetical occupants were used. The aerosol was approximated as a mixture of nine monodisperse (single particle size) components corresponding to particle size increments measured by the eight stages plus the backup filter of the cascade impactors used. A Markov Chain Monte Carlo Bayesian analysis technique was employed, which straightforwardly calculates the uncertainties in doses. Extensive quality control checking of the various computer codes used is described.

Particle size and aerosol iron solubility: A high-resolution analysis of Atlantic aerosols

Aerosol samples were collected in the North Atlantic Ocean during June–August, 2003. Aerosols were divided into nine size fractions ranging from > 18 μm to < 0.056 μm. Total element concentrations were measured by energy dispersive X-ray fluorescence to determine the size distribution of biogeochemically important elements. The solubility of Fe and other elements was measured in ultrapure deionized water to investigate the relationship between particle size and aerosol solubility. We found that the majority of soluble aerosol Fe was on particles of ≥ 1 μm aerodynamic diameter. Aerosol Fe solubility was somewhat variable but in general, aerosol Fe solubility did not increase with decreasing particle size.

Evaluation of committed effective doses from internal contamination of 241Am using experimentally determined parameters of the contaminant

Internal contamination of workers with 241Am has occurred a few times since the beginning of the 1970s, mainly in the workplace where radionuclide sources were produced, and later on, also during liquidation of radioactive waste. Contamination in workers was measured in vivo and bioassay was performed. Solubility of aerosol in lungs was studied by in vitro dissolution test with a simulant solution of the extracellular airway lining fluids. Model calculation for the estimation of intakes was done with the experimentally obtained parameters of aerosol, with modified times of intake, with scattering factors, including Types A and B errors, and with corrections on skull size for in vivo measurements. For most cases, an acceptable fit to the experimental data was obtained; for two cases with intakes taking place long time ago ( approximately 30 y), some changes in the model are necessary.