Dry deposition, of ozone

Broder, B. and H. A. Gygax (1985), The Influence of Locally Induced Wind Systems on the Effectiveness of Nocturnal Dry Deposition of Ozone, Atmos. Environ. 19, 1627-1637. 

Colbeck, I., and Harrison, R. M., Dry deposition of ozone Some measurements of deposition velocity and of vertical profiles to 100 metres. Atmos. Environ. 19, 1807 (1985). 

Transport from the atmosphere to land and water Dry deposition of particulate and gaseous pollutants Precipitation scavenging of particulate and gaseous pollutants Adsorption of gases onto particles and subsequent diy and wet deposition Transport within the atmosphere Turbulent dispersion and convection Atmospheric transformation Diffusion to the stratosphere Photochemical degradation Oxidation by free radicals and ozone Gas-to-particle conversion... 

Approximately 10% of atmospheric ozone resides in the troposphere. Since solar radiation of wavelengths less than 242 nm that photolyzes molecular oxygen (see Reaction (5.11)) is entirely absorbed above the tropopause, and hence cannot produce ozone in the lower atmosphere, it was believed for a long time that the presence of O3 in the free troposphere was due to downward transport of ozone-rich air masses from the stratosphere. Dry deposition of O3 on vegetation was believed to be the only significant loss process. 

Harrison, 1985 Huebert and Robert, 1985 Shepson et al., 1992). Gases that are removed readily by dry deposition have deposition velocities of order 1 cm s 1 or larger. Examples include nitric acid (HN03) and sulfur dioxide (S02). Ozone deposition velocities are about 0.5 cm s-1. With a 1 km deep atmospheric boundary layer, a gas with a deposition velocity of 1 cm s-1 has a timescale for dry deposition of the order of 1 day. Dry deposition will be an important removal process for species whose timescale for dry deposition is comparable to or smaller than that for chemical transformation. 

Relation of 03 to NO, From the definition of the ozone production efficiency, the signature of an NO molecule lost is the appearance of a number of 03 molecules, the specific number depending on atmospheric conditions and the HC and NO levels. Thus, the 03 concentration attained in an airmass should be correlated with the quantity [NO,]-[NO ], which is the total concentration of products of NO oxidation (HNO3, PAN, etc.). That this correlation should exist in airmasses was first pointed out by Trainer (1991, 1993), and it has been subsequently pursued in numerous studies [e.g., Kleinman (1994, 1997), CarpenteT et al. (2000)]. To obtain a good correlation between [03] and [NO,]-[NO ], O3 production must have occurred within a day or so in the airmass, before significant removal of NOv can take place, for example by wet and dry deposition of HN03. 

From the standpoint of regional tropospheric chemistry—which involves near-surface abundances of ozone, wet and dry deposition of acidic species, and transport and lifetimes of trace atmospheric constituents—the climate variables of interest include the variability of distributions of temperature, precipitation, clouds, and boundary-layer meteorology. In the global sense, these variables are controlled by surface and atmospheric temperature and water content. The distributions of temperature and water vapor are in turn controlled by solar and longwave radiation transfer involving the surface and the atmosphere. 

Pio, C.A., Feliciano, M.S., 1996. Dry deposition of sulphur dioxide and ozone over low vegetation in moderate southern European weather conditions. Measurements and modelling. Ann. Geophys. Part II (Suppl. II, Col. 14), C468. 

Acid deposition is the more accurate and scientifically preferred term. It is true that sulfur dioxide undergoes oxidation to the trioxide, which in turn converts to sulfuric acid in clouds, fogs, and mists. On the other hand, dry deposition of acidic aerosols and particulates is deemed to be just as damaging, especially as far as the adverse effects on trees and historic buildings are concerned. Moreover, ozone and heavy metals, which contribute to ecosystem damage, are not themselves acidic. 

Figure 4-13 shows an example from a three-dimensional model simulation of the global atmospheric sulfur balance (Feichter et al, 1996). The model had a grid resolution of about 500 km in the horizontal and on average 1 km in the vertical. The chemical scheme of the model included emissions of dimethyl sulfide (DMS) from the oceans and SO2 from industrial processes and volcanoes. Atmospheric DMS is oxidized by the hydroxyl radical to form SO2, which, in turn, is further oxidized to sulfuric acid and sulfates by reaction with either hydroxyl radical in the gas phase or with hydrogen peroxide or ozone in cloud droplets. Both SO2 and aerosol sulfate are removed from the atmosphere by dry and wet deposition processes. The reasonable agreement between the simulated and observed wet deposition of sulfate indicates that the most important processes affecting the atmospheric sulfur balance have been adequately treated in the model. 

Droppo, J. G Jr., Concurrent Measurements of Ozone Dry Deposition Using Eddy Correlation and Profile Flux Methods, J. Geo-phys. Res., 90, 2111-2118 (1985). 

The CASTNET provides atmospheric data on the dry deposition component of total acid deposition, ground-level ozone, and other forms of atmospheric pollution. CASTNET is considered the nation s primary source for atmospheric data to estimate dry acidic deposition and to provide data on rural ozone levels. Used in conjunction with other national monitoring networks, CASTNET is used to determine the effectiveness of national emission control programs. Established in 1987, CASTNET now comprises over 70 monitoring stations across the United States. The longest data records are primarily at eastern sites. The majority of the monitoring stations are operated by EPA s Office of Air and Radiation however, approximately 20 stations arc operated by the National Park Service in cooperation with EPA. 

We simulated a period of three years (not nudged) to investigate the climatology of the tropospheric ozone budget and the contribution by STE. We focus on the NH where the ozone-PV relation derived from MOZAIC is applied. Figure 4 displays the seasonality of cross-tropopause transports, photochemical production/destruction, dry deposition and the tropospheric content of ozone. 

For a long time, transport from the stratosphere to the troposphere was thought to be the dominant source of ozone in the troposphere. Early in the 1970s, it was first suggested that tropospheric ozone originated mainly from production within the troposphere by photochemical oxidation of CO and hydrocarbons catalysed by HO and NO c- These sources are balanced by in-situ photochemical destruction of ozone and by dry deposition at the earth s surface. Many studies, both experimental- and model-based have set about determining the... 

C is a term representative of the photochemistry (production or destruction), Ey the entrainment velocity, [03] the concentration of free tropospheric ozone, the dry deposition velocity and H the height of the boundary layer. The ozone budget shown in Table 8 has been calculated both in the summer and winter using the ozone continuity equation for a site in the marine boundary layer. 

Dry deposition is frequently the main sink for ozone in the rural atmospheric boundary layer. What is the lifetime of ozone with respect to this process ... 

Thus taking the boundary layer as a discrete compartment, the lifetime of ozone with respect to dry deposition is around 1 day. The lifetime in the free troposphere (the section of the atmosphere above the boundary layer) is longer, being controlled by transfer processes in and out, and chemical reactions. The stratosphere lifetime of ozone is controlled by photochemical and chemical reaction processes. 

FIGURE 4-32 Diurnal cycle of Vd for ozone for a deciduous forest, averaged over the period July 7 to August 30, 1988. Observed values of Vd and values estimated by four models are shown. (Reprinted from Atmospheric Environment, Vol. 30, L. Zhang, J. Padro, and J. L. Walmsley, A Multi-Layer Model vs. Single-Layer Models and Observed 03 Dry Deposition Velocities, pp. 339-345, Copyright 1996, with permission from Elsevier Science.)... 

Padro, J. (1996). Summary of Ozone Dry Deposition Velocity Measurements and Model Estimates over Vineyard, Cotton, Grass and Deciduous Forest in Summer. Atmos. Environ. 30(13), 2363-2369. 

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