Measurements and Modeling of Atmospheric Deposition in Major International Programs

Mechanisms and various physical, chemical, biological, and hydrometeorological processes involved in formation of atmospheric deposition have been studied in numerous projects within major international research programs, such as the EUROTRAC (http://www3.gsf.de), the EU ELOISE (http://www.eloisegroup.org), the US National Atmospheric

Deposition Program (NADP) (http://nadp.sws.uiuc.edu), and various IGBP (http://www.igbp.net) projects. The major IGBP projects in the atmospheric deposition field include the International Global Atmospheric Chemistry (IGAC) project (http://www.igac.noaa.gov), Surface Ocean - Lower Atmosphere Study (SOLAS) project (http://www.solas-int.org), Land-Ocean Interactions in the Coastal Zone (LOICZ) project (http://www.loicz.org), and Integrated Land Ecosystem - Atmosphere Processes Study (iLEAPS) project (http://www.atm.helsinki.fi). A large body of information has been obtained on dry and wet deposition of various gases and particles with different chemical compositions and sizes. This information has been used to quantify the atmospheric deposition as one of the major fluxes of various chemicals in the Earth system.

The European Monitoring and Evaluation Program (EMEP, http://www.emep.int), established within the UN ECE LRTAP, is the largest program in the world which studies source-receptor relationships for acid-forming gases, photooxidants, nutrients, and contaminants emitted to the air. The EMEP assesses the atmospheric deposition of these chemicals in Europe using both modeling approaches and monitoring network. An example of EMEP map of dry and wet deposition of sulfur compounds is presented in Figure 6. The EMEP results are used to assess what portion of emissions of the above-mentioned chemicals emitted in one country or a given region is deposited in another country or other regions. Such information is then used in negotiations of reductions of emissions and exposure to air pollutants in Europe.

The US NADP was organized already in 1977 as the US State Agricultural Experiment Stations (SAES) project to measure atmospheric deposition in the US and study the environmental effects of the deposited chemicals. In the 1980s, with the establishment of the National Acid Precipitation program (NAPAP), the network name was change to NADP/NTN (National Trends Network). At present, the NADP is SAES National Research Support project 3 with more than 250 stations.

The OSPARCOM and HELCOM measurement networks are used to assess the atmospheric deposition of nutrients and contaminants to the North Sea and NorthEast Atlantic, and the Baltic Sea, respectively. The results of this assessment are compared with inputs of these chemicals through other pathways, such as river discharges and direct releases. The results of input assessments are then used to develop strategy for reduction of inputs of nutrients and contaminants to these seas.

Assessment of atmospheric deposition to the Great Waters in the North America also provides a large body of information on deposition of nutrients and contaminants to aquatic surfaces. This measurement program has been carried out within the US Clean Air Act.

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Figure 6 Dry (a) and wet (b) deposition of sulfur compounds in Europe in 2003, in mg(S) m 2. From the Meteorological Synthesizing Centre-West of the European Monitoring and Evaluation Programme (EMEP, www.emep.int).

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