Nitric acid concentrations in southern California museums

Abstract

Measurements were made during two seasons at five
\nLos Angeles area museums to determine the concentrations
\nof nitric acid in outdoor and indoor air. Mean seasonal
\nindoor nitric acid concentrations ranged from <0.1 to 1.5
\nµg/m^3 corresponding to less than 1-40% of the outdoor
\nnitric acid concentration, depending on building construction and ventilation system design. A mathematical
\nmodel was applied to determine whether indoor/outdoor
\nHNO_3 concentration ratios can be predicted from data on
\nbuilding parameters and ventilation system design. Good
\nagreement between predicted and measured values was
\nfound. The rates of deposition of total inorganic nitrate
\nonto vertical surfaces due to gas-phase plus aerosol-phase
\npollutants were measured and found to vary from 0.2 to
\n5.8 ng m^(-2) s(^-1). Measurements indicate that nearly all of this deposition flux was delivered due to deposition of
\ngas-phase species, but comparison to theoretical HN03
\ntransport calculations suggests that gaseous species in
\naddition to HNO_3 contribute to the observed accumulation
\nof inorganic nitrate.