On the use of measurements and models of dry deposition

Deposition of chemical pollutants are known to effect aquatic and terrestrial ecosystems in some circumstances. The methodologies for quantifying the contributions from wet deposition are well known. Techniques for making direct measurements of dry deposition are available but only for short research intensive experiments. The demands placed on the instrumentation and operator skills are such that routine application of these techniques are not yet possible. Consequently, the use of models has been advocated as a means of deriving spatial and temporal trends of dry deposition rates. In the fall of 1984, a small network of dry deposition research sites was established. It has since evolved to a total of 13 stations (Figure 1). Weekly deposition rates of SO{sub 2}, SO{sub 4}, HNO{sub 3} and NO{sub 3} are derived at these sites by coupling weekly integrated filterpack concentrations with appropriate deposition velocities. The weekly average deposition velocities are derived from site specific meteorological data and information about the surface surrounding the site (1). The model used to derive the deposition velocities has been benchmarked (2) against direct measurements of deposition velocities (eddy correlation) at a subset of the 13 sites (CORE sites, Figure 1). The model is then applied with somemore » confidence to other sites to infer dry deposition rates. Results of seasonal dry deposition rates are presented for 3 research sites in dry deposition research network. Temporal trends in concentration and deposition velocities are discussed as well as yearly deposition rates of S and N.« less