Protecting Visibility in National Parks and Wilderness Areas (1993) / Chapter Skim
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Appendix A: Scientific Background Information
Appendix A: Scientific Background Information
Pages 315-324
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From page 315... ...
disulfide (CH3SSCH3) , and related species are derived from natural sources and undergo rapid oxidation in the troposphere to provide a small background source of SO2, which amounts to about 6% of the SO2 found over North America (Places and Streets, 1987~.
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From page 316... ...
is a major source of the HO radical through its photodecomposition to the highly reactive, excited oxygen atom, O(iD) , which reacts with water vapor: O3 + hu(A < 305~)
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From page 317... ...
The major oxidants, H2O2 and O3, are the secondary products formed in gas-phase reactions initiated by the irradiation of air masses containing NO, NO2, and hydrocarbons. Those compounds, as well as molecular oxygen in the presence of certain transition metal catalysts, can oxidize bisulf~te to sulfuric acid and ultimately to the various partially neutralized species (principally ammonium bisulfate)
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From page 318... ...
The gaseous nitric acid can react at basic airborne particle surfaces to form nitrate salts (Seinfeld, 1986~. For example, a particle containing calcium carbonate, can neutralize the nitric acid to produce calcium nitrate.
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From page 319... ...
(1990) have shown that particulate nitrate measured in Los Angeles accumulates in three distinct modes with mass mean aerodynamic diameters of 0.2 + 0.
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From page 320... ...
The sampling of organic materials can be very difficult; organic particles that are collected on filters can lose volatile components during He collection period, and reactive particulate organics can undergo chemical changes after collection on filters, in flasks, or on adsorption media. Problems are especially severe in pristine areas where low concentrations lead to large relative errors because of sampling artifacts.
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From page 321... ...
Although such estimates suggest that secondary organic compounds can contribute significantly to visibility impairment, there is little experimental evidence that permits quantitative estimates of the relative contributions of primary and secondary compounds to organic particle formation on a national scale.
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From page 322... ...
The stations can be powered by solar cells for use at remote locations. Estimates of atmospheric transport based solely on surface winds are subject to interpolation errors in the horizontal direction and to extrapolation errors in the vertical direction.
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From page 323... ...
Tethered balloons, with attached tethersondes, can be used to measure winds, temperature, and humidity up to altitudes of about 2 km during light wind conditions; however, these balloons become unstable at wind speeds above roughly ~ m/sec. Freerise balloons, including instrumented units (e.g., rawinsondes)
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From page 324... ...
Ideally, a meteorological measurement program would include the use of remote sensing to measure temporal variations of winds above the surface. Remote sensing would be complimented by balloons.
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