Atmospheric input and origin of selected elements in Walker Branch Watershed,Oak Ridge,Tennessee

The elemental composition and relative contribution to input of precipitation and aerosols have been determined for the Walker Branch Watershed in Oak Ridge, Tennessee, U.S.A. Comparison of elemental ratios in rain to those in local soils indicates that Cu, Hg, and Pb are enriched with respect to soil by a factor of 30 to 170 and must have a non-soil source. Due to inherent problems encountered in determining elemental deposition velocities, elemental input by dry deposition was calculated using literature value upper and lower limits. If the higher deposition velocities are chosen, dry deposition could constitute from 62 to 96% of the total input for selected elements to the watershed. Enrichment factor and chemical mass balance calculations have been applied to aerosol data in an attempt to distinguish between atmospheric particulates derived from soil, automobiles, and three nearby coal-fired steam plants. Elemental deposition by wet and dry fallout has also been calculated using published deposition velocities. Mass balance calculations indicate that no more than 5% of the total aerosol load can be attributed to the three coal-fired steam plants. The steam plants can, however, account for up to 20% of individual elements collected in air above the watershed.