Measurements of Dry Deposition for Deposition Velocity Model Evaluation

摘要

The U.S. Environmental Protection Agency's (EPA) nationwide network to monitordry deposition of gases and particles, the National Dry Deposition Network (NDDN), measures not deposition, but concentration of pollutants and meteorological variables relevant to deposition processes. The amount of pollutant being deposited per unit area and time, the flux, is computed as the product of the measured concentration and calculated deposition velocity. Deposition velocity is estimated using an inferential model developed by NOAA's Atmospheric Turbulence and Diffusion Division. The model simulates the physical and chemical processes of pollutant transfer and absorption by plants and surfaces using measured meteorological and site vegetation variables as input. Annual and seasonal dry deposition as derived from the inferential model and concentration measurements are reported for the 50 site EPA NDDN. Th authors have recently begun an independent effort to evaluate depositon velocity models by making direct flux measurements and concurrent meteorological measurements needed for the models at several NDDN sites, which differ in terrain, climate, soil, and vegetation cover. The measurement system, instrumentation, and sampling protocol are described briefly herein, along with some preliminary data from out 1994 field program. More detailed analyses are currently underway.