Indoor/outdoor concentrations and indoor surface accumulations of ionic substances

The airborne concentrations of soluble ions in fine particles and coarse particles have been measured indoors and outdoors at telephone offices in Wichita, Kansas and Lubbock, Texas, These concentrations are compared with the mean annual indoor surface accumulations of these ions on zinc and aluminum structural surfaces. On average, the major soluble ions contained in fine airborne particles are ammonium, sulfate, and nitrate, while those contained in coarse particles are calcium and nitrate. In the fine mode, potassium and chloride have indoor/outdoor ratios that are larger than those observed for the other ionic species, indicating the existence of a significant indoor source. In the coarse mode, similar comparisons show that sodium, chloride, and sometimes sulfate have significant indoor sources. For chloride, a simple model has been used for apportioning surface accumulation at each location due to corrosive chlorine gases, coarse particles, and fine particles. For other ions where corrosive gases are not important, the accumulation has been apportioned between coarse and fine particles. From these data, experimental deposition velocities for fine mode sulfate ions and coarse mode calcium ions were calculated to be 0.003 and l.0 cms⁻¹, respectively, at Wichita, while those at Lubbock were 0.005 and 0.2 cms⁻.