Indoor/outdoor ratios and indoor surface accumulations of ionic substances at Newark, New Jersey

Abstract

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. The deposition velocities are based on average annual surface accumulations derived from approximately 500 extractions of Zn and Al surfaces and indoor concentrations based on more than a year of sampling. Examination of the indoor/outdoor ratios suggests that K + and possibly Ca 2+ associated with fine mode particles have appreciable indoor sources, while SO 4 2−, Na + , NH 4 − and Mg 2+ do not. In the coarse particle mode, SC 4 2− and K + appear to have indoor sources. The deposition velocities for the ions exhibit some spread in the fine mode, consistent with expected variations in size distributions. The deposition velocities of ions associated with coarse mode particles are in the same range as the gravitational settling velocities, as expected. The consistency of the deposition velocities that were measured for fine mode sulfate at Wichita, Lubbock and Newark indicates that a value of 0.005 cm s −1 can be used to estimate the deposition velocity for sulfate at all locations with air flow characteristics similar to these sites. Using a methodology described previously, these improved sets of indoor/outdoor ratios and deposition velocities for ions in fine and coarse particles can be used for estimating indoor surface accumulation rates from outdoor concentrations.