A new procedure for the determination of atmospheric sulfur compounds was developed and applied during three months in the central area of the City of Porto Alegre- RS, and one month near an oil refinery located close to this city. The method is based on the coulometric determination of the tarnishing rate of pure silver. The results were compared with the method of pararosaniline, which is being currently used in some of the studied sites for the determination of SO2. The results obtained showed a good correlation between the coulometric method and the pararosaniline method, when only SO2 is present, as usually is the case of urban atmospheres. When H2S is also present, as in the case of industrial areas, the methodology tends to strongly overestimate SO2 concentration.
coulometric method; tarnishing of Ag; urban pollution; SO2, H2S
