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Project Status: complete

Title: Measurement of atmospheric dry deposition at Emerald Lake in Sequoia National Park

Principal Investigator / Author(s): Bytnerowicz, Andrzej

Contractor: Statewide Air Pollution Research Center, UC Riverside

Contract Number: A732-039

Research Program Area: Atmospheric Processes

Topic Areas: Acid Deposition, Ecosystem Impacts


The primary objective of this study was to assess atmospheric dry deposition of major anions and cations to trees at the Emerald Lake area of the Sequoia National Park. The field work was performed between July 15, 1987 and September 10, 1987, utilizing three time periods without wet precipitation for dry deposition determinations. Materials deposited on Teflon film coated and non-coated branches of two native coniferous species, lodgepole pine (~ concorta) and western white pine (f. monticola) , as well as potted seedlings of Coulter pine (P. coulteri) were rinsed from the foliage with deionized-distilled water. Atmospheric ions deposited to two surrogate surfaces (nylon and paper filters) were extracted from the filters in deionized-distilled water. Acidity, conductivity, and concentrations of nitrate, sulfate, phosphate, chloride, fluoride, ammonium and metallic cations were determined in foliage rinses and filter extracts. Deposition fluxes of the studied ions to tree foliage and surrogate surfaces as well as conductivity of needle rinses and filter extracts have been determined. Deposition fluxes of the majority of the measured ions to the lodge- pole and western white pines were similar during all three exposure periods. However, deposition fluxes of chloride and ammonium were the highest during the second period of exposures (August 4-12, 1987). No significant differences were found between deposition rates to Teflon-coated branches and to non-Teflon branches. This indicates that for these two conifers, no significant extraction of ions during the washing procedures or uptake of ions deposited on needle surfaces by the needle interior took place. Highest deposition fluxes were determined for nitrate, ammonium, calcium and sodium. Deposition fluxes of sulfate were several times lower than deposition fluxes of nitrate.

For Coulter pines deposition rates of sulfate and phosphate were significantly higher for non-Teflon coated branches than for Teflon coated branches. This indicates that a significant extraction of ions from the needle interior during the washing procedures was taking place. Rinsing of branches enclosed in the clean-air chamber provided a mechanism to estimate amounts of ions being extracted from the needles (both Teflon and non-Teflon coated). After subtracting the extractable ions, the net dry deposition fluxes to the Teflon-coated branches and to the non-Teflon coated branches became similar, and in the range of values determined for the native pines. Highest values of deposition fluxes were found for nitrate, sulfate, ammonium, calcium and sodium. Deposition fluxes of some ions (especially chloride, ammonium, sodium and hydrogen) to the nylon and paper filters were quite different from the fluxes determined for the pine branches. For the nylon filters high deposition fluxes of nitrate, chloride, calcium and sodium were determined. Nitrate, ammonium, calcium and sodium deposition fluxes were the highest for the paper filters. No deposition fluxes of phosphate to these filters was found. Comparison of nitrate: sulfate and ammonium: sulfate ratios revealed that the fluxes of nitrogen compounds to the native coniferous species at Emerald Lake are of a greater importance than the sulfur compounds fluxes. This finding is similar to the ratio of these ions determined for the chaparral species in the mountains of the South Coast Air Basin, California, during the summer of 1985. Balancing deposition of anions and cations to different surfaces indicates a deficit of anions. This suggests that anions not measured during this study (organic anions and carbonate) may playa more important role than previously thought in dry deposition.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 322-3893

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