Development and field evaluation of a new diffusive sampler for hydrogen sulphide in the ambient air

A study on the applicability of zinc acetate impregnated silica substrate in the collection of hydrogen sulfide by active sampling

A novel substrate for the hydrogen sulfide determination in air was developed based on zinc acetate impregnated silica in glass tubes. Collected H2S is quantified by ion chromatography after sulfide oxidation to sulfate in an alkaline solution of H2O2. Laboratory tests were conducted in controlled atmosphere to evaluate uptake rate, linearity, sample stability, influence of relative humidity and interfering gases. A pilot study was also conducted in the field in order to assess the applicability of the substrate and to understand the effect that gases such NO2 and CH4 can have on the efficiency of collection of H2S. The new substrate has shown to have several advantages with respect to the charcoal substrate, that is the one of choice as reported by National Institute of Occupational Safety and Health (NIOSH) method. In particular it does not suffer from sulfur background and it is not influenced by interfering gases such as NO2 and CH4.

Characterization of the olfactory impact around a wastewater treatment plant: optimization and validation of a hydrogen sulfide determination procedure based on passive diffusion sampling

A monitoring program based on an indirect method was conducted to assess the approximation of the olfactory impact in several wastewater treatment plants (in the present work, only one is shown). The method uses H2S passive sampling using Palmes-type diffusion tubes impregnated with silver nitrate and fluorometric analysis employing fluorescein mercuric acetate. The analytical procedure was validated in the exposure chamber. Exposure periods ofat least 4 days are recommended. The quantification limit of the procedure is 0.61 ppb for a 5-day sampling, which allows the H2S immission (ground concentration) level to be measured within its low odor threshold, from 0.5 to 300 ppb. Experimental results suggest an exposure time greater than 4 days, while recovery efficiency of the procedure, 93.0+/-1.8%, seems not to depend on the amount of H2S collected by the samplers within their application range. The repeatability, expressed as relative standard deviation, is lower than 7%, which is within the limits normally accepted for this type of sampler. Statistical comparison showed that this procedure and the reference method provide analogous accuracy. The proposed procedure was applied in two experimental campaigns, one intensive and the other extensive, and concentrations within the H2S low odor threshold were quantified at each sampling point. From these results, it can be concluded that the procedure shows good potential for monitoring the olfactory impact around facilities where H2S emissions are dominant.