The purpose of the Western Airborne Contaminants Assessment Project (WACAP) was to evaluate ecological impacts of airborne contaminants in national parks using a network of sites to provide spatially extensive, site specific, and temporally-resolved information on the exposure, accumulation, and impacts of airborne toxic compounds. WACAP was designed and implemented by the National Park Service's Air Resources Division with cooperators from the U.S. Environmental Protection Agency, U.S. Geological Survey, and several universities, as well as the participating National Parks. Eight core national parks participated in WACAP: Sequoia, Rocky Mountain, Olympic, Mt. Rainier, Glacier, Denali, Noatak, and Gates of the Arctic. An additional 11 national parks and one national forest participated in sampling vegetation and air in 2005. WACAP was conducted over a six-year timeline, with the first year (2002) for design and method development work, three years (2003-2005) for field sampling and analysis, and the last four years (2006 to 2009) for completing analyses and preparing the final report, database and interpretive reports. The final report for WACAP, The Fate, Transport, and Ecological Impacts of Airborne Contaminants in Western National Parks (USA) (Landers et al. 2008), contains details about the sampling design, methods, and results. Section 3.4 of the report provides details of methods used for each ecosystem medium.