Accumulation of Particle Derived Ionic Contaminants on Electronic Equipment: Airborne Concentrations and Deposition Velocities

We previously reported deposition velocities for chloride, nitrate, sulfate, sodium, ammonium, potassium, magnesium, and calcium associated with fine and coarse particles at telephone company switching equipment locations in Wichita, Kansas and Lubbock, Texas. Preliminary data were also reported for a site in Newark, NJ. These results were based on comparisons of indoor concentrations, obtained using dichotomous samplers for collection and ion chromatography (IC) for analysis, with average annual surface accumulations that were obtained by collecting water extracts of zinc and aluminum structural surfaces and then analyzing by IC. In this paper we report the complete results for the Newark site and for a new site in Neenah, Wisconsin. The deposition velocities are based on average annual surface accumulations derived from approximately 500 extractions of zinc and aluminum surfaces as well as indoor concentrations measured for an annual cycle at weekly intervals at both the Newark and Neenah sites. The results demonstrate that deposition velocities for each of the major ions are similar, regardless of location, and can be used to predict surface accumulation rates and that variations in surface accumulations are not attributable to variations in airborne concentrations.