DEPOSITION OF ATMOSPHERIC IONS TO PINE BRANCHES AND SURROGATE SURFACES IN THE VICINITY OF EMERALD LAKE WATERSHED, SEQUOIA-NATIONAL-PARK

Atmospheric dry deposition of ions to branches of native Pinus contorta and Pinus monticola (natural surfaces), and nylon filters and Whatman paper filters (surrogate surfaces) were measured in the summer of 1987 in the vicinity of Emerald Lake Watershed (ELW) of the Sequoia National Park located on the western slope of the Sierra Nevada in California. Deposition fluxes of airborne NO3-, NH4+ and SO4(2-) to naive pines at the ELW were much higher than in the eastern Sierra Nevada, but several times lower than deposition fluxes to natural and surrogate surfaces at the highly polluted site in the San Gabriel Mountains of southern California. Deposition fluxes of NO3- and NH4+ to the natural and surrogate surfaces at the ELW were much higher than deposition of SO4(2-), proving the importance of N compounds in atmospheric dry deposition in this part of the western U.S. A deficit of inorganic anions in materials deposited to various surfaces indicated a possibility of substantial participation of organic acids in atmospheric dry deposition processes. Nylon and paper filters proved to be poor surrogate surfaces for the estimation of ionic dry deposition to conifer branches.