Acidic and alkaline constituents of air particulates within dwellings

The acidic and alkaline substances of indoor and outdoor PM10 aerosol samples were collected simultaneously in 15 domestic environments in the Taipei urban area; 10% of indoor and 20% of outdoor PM10 levels exceeded the USEPA 24 h standard for PM10 (150 μg m−3). The mean indoor concentrations of Na+, K+, NH4+, Cl−, SO42− and NO3− were observed to be 52, 16, 206, 20, 114 and 50 nmol m−3, respectively. The mean outdoor concentrations of the ions mentioned above were 56, 18, 234, 32, 130 and 65 nmol m−3, respectively. Moreover, the mean concentrations of the indoor and outdoor excess SO42− were observed to be 112 and 127 nmol m−3, respectively. On average, the sum of the six analyzed ions constituted 20% of the total mass concentration from the indoor and outdoor PM10 samples. The major portion of the acid present in Taipei aerosols is associated more with SO42− than with NO3−. Furthermore, significant correlations of SO42− with NH4+ and NO3− were observed, and aerosol sulfates are neutralized by atmospheric ammonia to form (NH4)2SO4. In addition, the indoor and outdoor SO42−Na+ ratios were found to be much higher than that of sea-water, indicating a SO42− origin from anthropogenic sources.