Atmospheric wet deposition

Abele D, Ferreira GA, Schloss I (1999) H202 accumulation from photochemical production and atmospheric wet deposition in Antarctic coastal and off-shore waters of Potter Cove, King George Island. Antarc Sci 11 131-139... 

TANNER Instrumentation of Atmospheric Wet Deposition Processes Acknowledgments... 

Zhang, J. (1994). Atmospheric wet deposition of nutrient elements Correlation with harmful biological blooms in Northwest Pacific coastal zones. Ambio 23, 464—468. 

The variable emission rates and the meteorological parameters — wind velocity (dilution factor), wind direction (contribution of other sources) and the occurrence of atmospheric wet deposition - are the main parameters responsible for the variation in ambient air concentration levels with a factor of 10. 

In 2003, a wet-deposition collection site was established in Iasi, northeast Romania, to monitor the quantity and chemical quality of atmospheric wet deposition. Monitoring was carried out from May 2003 to May 2004. EHiring the first phase of sampling 52 wet-deposition samples were collected. A second phase of sampling began in May 2004 and is... 

Agrawal, M. and R.K. Singh Effect of industrial emission on atmospheric wet deposition, Water, Air, and Soil Pollut., 130 (2001) 481-486. 

Scudlark JR, Conko KM, Church TM. 1994. Atmospheric wet deposition of trace elements to Chesapeake Bay CBAD study year 1 results. Atmos Environ 28(8) 1487-1498. 

Atmospheric deposition is also a major source of metal input into many aquatic ecosystems (Salomons 1986). Helmers and Schrems (1995) reported for the tropical North Atlantic Ocean that wet trace element deposition dominates over dry input. From the increased enrichment factors relative to the Earth s crust, the determined trace metal concentrations were assumed to originate from anthropogenic sources. For atmospheric wet depositional fluxes of selected trace elements at two mid-Atlantic sites, Kim et al. (2000) reported that at least half of the Cr and Mn and more than 90% of the Cd, Zn, Pb, and Ni are from non-crustal (presumably anthropogenic) sources. 

Kim G, Scudiark J and Church T (2000) Atmospheric wet deposition of trace dements to Chesapeake and Delaware Bays. Atmos Environ 34 3437-3444. 

Conko, K.M., Rice, K.C., Kennedy, M.M., 2004. Atmospheric wet deposition of trace elements to a suburban environment, Reston, Virginia, USA. Atmos. Environ. 38, 4025—4033. Cowherd, C., Muleski, G.E., Englehart, P.J., Gillette, D.A., 1985. Rapid Assessment of Exposure to Particulate Emissions from Surface Contamination Sites. U.S. EPA Report No. EPA/600/ 8-85/002. Office of Health and Environmental Assessment, US Environmental Protection Agency, Washington, DC. 

Poster, D. and J. Baker, Mechanisms of atmospheric wet deposition of chemical contaminants, in Atmospheric Deposition of Contaminants to the Great Lakes and Coastal Waters Proceedingsfrom a Session at SETAC s 15th Annual Meeting, 1. Baker, Ed. 1997, SETAC Press, Pensacola, FL. 

Pesticides can be transported away from the site of appHcation either in the atmosphere or in water. The process of volatili2ation that transfers the pesticide from the site of appHcation to the atmosphere has been discussed in detail (46). The off-site transport and deposition can be at scales ranging from local to global. Once the pesticide is in the atmosphere, it is subject to chemical and photochemical processes, wet deposition in rain or fog, and dry deposition. 

Deposition. The products of the various chemical and physical reactions in the atmosphere are eventually returned to the earth s surface. Usually, a useful distinction is made here between wet and dry deposition. Wet deposition, ie, rainout and washout, includes the flux of all those components that are carried to the earth s surface by rain or snow, that is, those dissolved and particulate substances contained in rain or snow. Dry deposition is the flux of particles and gases, especially SO2, FINO, and NFl, to the receptor surface during the absence of rain or snow. Deposition can also occur through fog, aerosols and droplets which can be deposited on trees, plants, or the ground. With forests, approximately half of the deposition of SO(, NH+,andH+ occurs as dry deposition. 

The measurement data for reduced atmospheric nitrogen in the UK are of variable quality, largely because monitoring ambient NHj is subject to very large variations." However, the wet deposition monitoring data provide a good... 

Acid deposition refers to the transport of acid constituents from the atmosphere to the earth s surface. This process includes dry deposition of SO2, NO2, HNO3, and particulate sulfate matter and wet deposition ("acid rain") to surfaces. This process is widespread and alters distribution of plant and aquatic species, soil composition, pH of water, and nutrient content, depending on the circumstances. 

Fig. 10-12. Atmospheric processes involved in acidic deposition, The two principal deposition pathways are dry deposition (nonrain events) and wet deposition (rain events).

Except for fine particulate matter (0.2 /xm or less), which may remain airborne for long periods of time, and gases such as carbon monoxide, which do not react readily, most airborne pollutants are eventually removed from the atmosphere by sedimentation, reaction, or dry or wet deposition. 

Deposition is the atmospheric removal process by which gaseous and particulate contaminants are transferred from the atmosphere to surface receptors - soil, vegetation, and surface waters (22,27,28, 32). This process has been conveniently separated into two categories dry and wet deposition. Dry deposition is a direct transfer process that removes contaminants from the atmosphere without the intervention of precipitation, and therefore may occur continuously. Wet deposition involves the removal of contaminants from the atmosphere in an aqueous form and is therefore dependent on the precipitation events of rain, snow, or fog. 

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. 

Fig. 4-13 Calculated and observed annual wet deposition of sulfur in mgS/m per year. (Reprinted from "Atmospheric Environment," Volume 30, Feichter, J., Kjellstrom, E., Rodhe, H., Dentener, F., Lelieveld, and Roelofs, G.-J., Simulation of the tropospheric sulfur cycle in a global climate model, pp. 1693-1707, Copyright 1996, with permission from Elsevier Science.)...

Impurities travel from atmosphere to ice sheet surface either attached to snowflakes or as independent aerosols. These two modes are called wet and dry deposition, respectively. The simplest plausible model for impurity deposition describes the net flux of impurity to ice sheet (which is directly calculated from ice cores as the product of impurity concentration in the ice, Ci, and accumulation rate, a) as the sum of dry and wet deposition fluxes which are both linear functions of atmospheric impurity concentration Ca (Legrand, 1987) ... 

Methyl parathion can be released to surface waters by storm runoff from sprayed fields atmospheric deposition following aerial application (wet deposition from rain and fog water) waste water releases from formulation, manufacturing, or processing facilities and spills. 

The methyl parathion released to the atmosphere can be transported back to surface water and soil by wet deposition. Methyl parathion that is released to the atmosphere can also be transformed by indirect photolysis to its oxygen analog, methyl paraoxon, by oxidation with photochemically produced oxygen radicals. However, methyl parathion is not expected to undergo significant transformation to methyl paraoxon. 

Trichloroethylene has been detected in a number of rainwater samples collected in the United States and elsewhere (see Section 5.4.2). It is moderately soluble in water, and experimental data have shown that scavenging by rainwater occurs rapidly (Jung et al. 1992). Trichloroethylene can, however, be expected to revolatilize back to the atmosphere after being deposited by wet deposition. Evaporation from dry surfaces can also be predicted from the high vapor pressure. 

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