Airborne Trace Elements in Great Smoky Mountains, Olympic, and Glacier National Parks

Airborne trace elements were studied at remote sites in three U.S. National Parks where crustal weathering, sea spray, and long-range transport of anthropogenic emissions were likely to influence concentrations. Levels of all elements studied except Pb were smaller in Great Smoky Mountains National Park than in Olympic or Glacier Parks. Size distribution and Teflon plate dry deposition data showed that elements derived from crustal weathering were associated with larger particles and had greater dry deposition velocities than elements that were enriched relative to crustal composition. The bulk of the mass deposition of each element resulted from the small fraction of large airborne particles. On the basis of the dry deposition data, as well as concentration data obtained within and above the forest canopy, it is hypothesized that airborne particles may undergo successive deposition/re-suspension processes during transport from source to ultimate sink, complicating the measurement of net influx of a species into a region from upwind areas.