This project is an investigation of the transport of chemical trace elements and species from source regions through the atmosphere to the Greenland ice sheet. Its goal is to provide information for the interpretation of the trace element distribution in a long ice core to be obtained through the Greenland Ice Sheet Program (GISP-II) drilling effort. The ice core is expected to provide a detailed record spanning 200,000 years. The project has three specific objectives: (1) the identification of source regions and atmospheric pathways for the chemical constituents reaching the drill site, including the possible changes in air mass characteristics during transit, (2) the study of mechanisms and rates of incorporation of chemical species into precipitating snow, and (3) the investigation of post-depositional changes in snow chemistry and of the redistribution of species within the snowpack. Field work consists of the collecting of air, aerosol, precipitation, and deposited snow samples, which will be analyzed for various anions and cations, trace elements, carbon compounds, and trace gases. A special atmospheric camp, to ensure that samples will be uncontaminated by the drilling, has been planned as part of the GISP-II program.