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Abstract
Annular denuder-fllter pack sampling systems were used to make Indoor and outdoor measurements of aerosol strong H+, SO4 2−, NH4 +, NO3 − and NO2 −, and the gaseous pollutants SO2, HNO3, HONO and NH3 during summer and winter periods in Boston, Massachusetts. Outdoor levels of SO2, HNO3, H+ and SO4 2− exceeded their indoor concentrations during both seasons. Winter indoor/outdoor ratios were lower than during the summer, probably due to lower air exchange rates during the winter period. During both monitoring periods, Indoor/ outdoor ratios of aerosol strong H+ were 40-50 percent of the Indoor/outdoor SO4 2− ratio. Since aerosol strong acidity Is typically associated with SO4 2−, this finding Is indicative of neutralization of the acidic aerosol by the higher Indoor NH3 levels. Geometric mean indoor/ outdoor NH3 ratios of 3.5 and 23 respectively were measured for the summer and winter sampling periods. For HONO, NH3, NH4 + and NO2 −, indoor concentrations were significantly higher than ambient levels. Indoor levels of NO3 − were slightly less than outdoor concentrations.