9300627 Davidson This three-year award supports U.S.-Sweden cooperative research between Cliff I. Davidson, of Carnegie-Mellon University and Mats Oblad of the Chalmers University of Technology. The objectives of the research are (1) to measure and model dry deposition of atmospheric acids and trace elements in the Gardsjon Lake forest canopy in central Sweden as part of a large international watershed study; and (2) to develop models and interpret data on dry deposition in the Artic region. The investigators will study sulfate and nitrate acidic compounds known to cause ecosystem damage, and certain trace elements that are known to neutralize acids. The proposed work will focus on field measurements and computer modeling of dry deposition processes. Atmospheric acids are transported to surfaces by wet and dry deposition. Dry deposition is an important mechanism of removal of acidic compounds from the atmosphere; however, its processes are not well understood. The forest deposition work and the work in the Artic will provide better estimates and understanding of the physical and chemical processes by which atmospheric particles interact with vegetated and snow surfaces. The researchers at Carnegie Mellon have developed unique, symmetric airfoil devices for measuring dry deposition. These will be set up in the forest canopy at Gardsjon Lake. The models on dry deposition in the Artic, also developed by the Carnegie-Mellon group, will be tested utilizing new datasets available at Chalmers University. The proposed collaboration takes advantage of Swedish expertise in modeling methods and experience in monitoring the deposition of acidic compounds in a forest canopy. It also allows comparision of results at American sites with those from Swedish sites. ***
