A field evaluation of a SO2 passive sampler in tropical industrial and urban air

Passive samplers have been widely used for over 30 years in the measurement of personal exposure to vapours and gases in the workplace. These samplers have just recently been applied in the monitoring of ambient air, which presents concentrations that are normally much smaller than those found in occupational environments. The locally constructed passive sampler was based on gas molecular diffusion through static air layer. The design used minimizes particle interference and turbulent diffusion. After exposure, the SO2 trapped in impregnated filters with Na2CO3 was extracted by means of an ultrasonic bath, for 15 min, using 1.0 x 10(-2) mol L-1 H2O2. It was determined as SO4-2 by ion chromatography. The performance of the passive sampler was evaluated at different exposure periods, being applied in industrial and urban areas. Method precision as relative standard deviation for three simultaneously applied passive samplers was within 10%. Passive sampling, when compared to active monitoring methods under real conditions, used in urban and industrial areas, showed an overall accuracy of 15%. A statistical comparison with an active method was performed to demonstrate the validity of the passive method. Sampler capacity varied between 98 and 421 mug SO2 m(-3) for exposure periods of one month and one week, respectively, which allows its use in highly polluted areas. (C) 2004 Elsevier Ltd. All rights reserved.