Development and field evaluation of a new diffusive sampler for Hydrogen Sulphide in the ambient air

A diffusive sampler for the determination of hydrogen sulphide (H₂S) based on collection on a paper filter coated with silver nitrate followed by optical densitometric determination of the metal sulphide was developed. Laboratory tests were conducted in controlled atmosphere to evaluate linearity, uptake rate, face velocity effects, sample stability, influence of relative humidity and of interferents, precision and accuracy. The measured uptake rate for H₂S was determined in experiments involving sampling at different concentration levels in comparison to a wet standard colorimetric technique. The precision of the measurements for co-located passive samplers was lower than 15%. The accuracy of the data collected is within 20% of the actual value measured by the wet method. The sampler is capable of reliable measurements of H₂S at common levels of a polluted atmosphere in urban settings yielding average concentration levels over one month and beyond. Diffusive sampling can be adopted to analyse in detail the temporal and spatial trends of H₂S concentration in ambient air and in specific historic buildings or in museums. Figure At the end of sampling cap #2 is removed and optical density is measured