Evaluation of a novel passive sampling technique for monitoring volcanogenic hydrogen sulfide

Abstract

A novel, low-cost passive sampling procedure for monitoring of volcanogenic hydrogen sulfide is reported. The technique is based on absorption of H₂S onto treated sections of photographic paper, which are housed in plastic film canisters during exposure. The H₂S reacts with silver halide in the photographic paper, causing a colour-change reaction from white, through brown, to black, depending on concentration of atmospheric H₂S. The sampler is sensitive to ≪30 ppb to ∼1000 ppb of H₂S. Here we present results from a series of optimization and quantification experiments. An active sampling procedure for rapid H₂S measurement is also reported, based on absorption of H₂S onto Whatman No. 41 cellulose filters treated with silver nitrate, and was shown to be quantitative using a single filter at flow rates <1.0 L min⁻¹ for collection of <200 μg of sulfide (as H₂S). Determination of sulfide collected on the substrates was performed using a rapid flow-injection technique based on the fluorescence quenching of fluorescein mercuric acetate (FMA) by sulfide. This was optimized at a FMA concentration of 8 mg L⁻¹, at which 100% quenching was obtained at a solution sulfide concentration of 3 mg L⁻¹.