Deposition model

A variety of models have been developed to study acid deposition. Sulfuric acid is formed relatively slowly in the atmosphere, so its concentrations are beUeved to be more uniform than o2one, especially in and around cities. Also, the impacts are viewed as more regional in nature. This allows an even coarser hori2ontal resolution, on the order of 80 to 100 km, to be used in acid deposition models. Atmospheric models of acid deposition have been used to determine where reductions in sulfur dioxide emissions would be most effective. Many of the ecosystems that are most sensitive to damage from acid deposition are located in the northeastern United States and southeastern Canada. Early acid deposition models helped to estabUsh that sulfuric acid and its precursors are transported over long distances, eg, from the Ohio River Valley to New England (86—88). Models have also been used to show that sulfuric acid deposition is nearly linear in response to changing levels of emissions of sulfur dioxide (89). 

J. S. Chang and co-workers. The Regional Acid Deposition Model and Engineering Model, State-of-Science—Technology Report 4, National Acid Precipitation Assessment Program, Washington, D.C., 1989. 

NUCRAC improves on the health effects model by a reexamination of Hiroshima and Nagasaki data. The dry deposition model was much improved by the inclusion of a particle-si/e distribution, a detailed settling model, and a detailed chronic exposure model via the food pathway. However, it does not include a rainout model. 

The aerodynamic particle diameter determines the fate of particles in the respiratory system. Coarse particles are deposited in the nose and nasopharynx. Smaller particles that pass the upper airway can be deposited in the bronchial region and lower airway. A size-selective deposition model and sampling of particles has been standardized both in Europe and internationally. The... 

Deposition Model. A two-step deposition model may be summarized as follows.In the first step, the diamond surface is activated by the removal of a surface-bonded hydrogen ion by atomic hydrogen as follows ... 

Terrestrial BicknelTs thrush Adult Blood Ability for significant uptake of Hg in montane habitats high priority for conservation blood levels related to atmospheric deposition models... 

Berger, B.R. (1983a) Epithermal gold-silver quartz-adularia type. In Cox, D.P. (ed.), GEOMINAS Mineral Resource Assessment of Columbia — Ore Deposit Models, U.S. Geological Survey. Open-File Report, 83, V. 23, 39. 

In the ASTER reactor deposition experiments were performed in order to compare with the 2D model results. Normalized deposition rates are plotted in Figure 22 as a function of radial position for data taken at 25 and 18 Pa. The deposition takes place on a square glass plate. For each pressure two profile measurements were performed, each profile perpendicular to the other (a and b in Fig. 22). A clear discrepancy is present. The use of the simplified deposition model is an explanation for this. Another recent 2D fluid model also shows discrepancies between the measured and calculated deposition rate [257], which are attributed to the relative simplicity of the deposition model. 

In this chapter the deposition of n-Si H by PECVD has been described. The chapter covers material as well as discharge issues. It tries to relate material and discharge properties in various ways. Plasma modeling provides a means to study in detail the physical and chemical processes that occur in the plasma. The presented models show a high degree of sophistication, but from the comparison with experimental data it is clear that especially the deposition model needs improvement. Also, a full 2D model most probably is not needed, as differences between ID and 2D modeling results are not very large. 

The ICRP deposition model estimates the fraction of inhaled material initially retained in each compartment (see Figure 3-2). The model was developed with five compartments (1) the anterior nasal passages (ET,) (2) all other extrathoracic airways (ET2) (posterior nasal passages, the naso- and oropharynx, and the larynx) (3) the bronchi (BB) (4) the bronchioles (bb) and (5) the alveolar interstitium (AI). Particles deposited in each of the regions may be removed and redistributed either upward into the respiratory tree or to the lymphatic system and blood by different particle removal mechanisms. 

Respiratory Tract Clearance. This portion of the model identifies the principal clearance pathways within the respiratory tract. The model was developed to predict the retention of various radioactive materials. Figure 3-4 presents the compartmental model and is linked to the deposition model (see Figure 3-2) and to reference values presented in Table 3-5. This table provides clearance rates, expressed as a fraction per day and also as half-time (Part A), and deposition fractions (Part B) for each compartment for insoluble... 

Most lung deposition models are based on the influence of particle size on aerosol deposition. Breathing parameters, such as breathing frequency and tidal volume, play a key role in lung deposition [15]. Table 2 shows the breathing parameters for healthy male volunteers subjected to various levels of exercise on a bicycle ergometer [16], There are known differences in these parameters based on gender, age, and disease... 

The deposition model used here includes expressions for diffusion (Ingham, 1975) sedimentation (Pich, 1972) and impaction (Egan and Nixon, 1985) and a realistic treatment of lung ventilation. It can be shown that this predicts the aerosol deposition measured in the lungs of human subjects (summarised by Rudolf (1986)) over the range of aerosol size from 5 nm to 5 pm diameter, and for all breathing conditions tested, to within 207o of measured values. 

Mercer, T. T. (1975). The deposition model of the Task Group on Lung Dynamics A comparison with recent experimental data, Health Phys. 29, 673. 

The random deposition model represented by Eq. (4.1) produces a mono tonic increase of surface width with time. 

The first step in the application of the concept was to determine the critical load values for the different regions of eastern Canada. This was done using historical measurements of lake acidity in concert with the Integrated Assessment Model (IAM) which links atmospheric transport and deposition models with water chemistry and empirical biological response models. Details of the method are given in Jeffries and Lam (1993). 

The Comprehensive Acid Deposition Model (CADM) has been created for calculation of dry and wet deposition of sulfur species over South Korea (Park et al 1997,1999a). This model presents quantitative assessment of the acidity loading and alterations in deposition rates. 

Cooney D, Kazantseva M, Hickey AJ (2004) Development of a size-dependent aerosol deposition model utilising human airway epithelial cells for evaluating aerosol drug delivery. Altern Lab Anim 32(6) 581-590. 

Work by Altshuler et al. with 0.4-fim particles and a tidal volume of 500 ml showed that only about 11-27% of new air in each successive breath actually mixes with residual air. Theoretical particle-deposition models developed by Altshuler, Beeckmans, and Davies have accounted for the mixing of inhaled aerosol with residual air. 

Kliment, V. Dichotomical model of respiratory airways of the rabbit and its significance for the construction of deposition models. Folia Morphol. 22 286-290, 1974. 

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