Mapping of H 2S fluxes from the ground using copper passive samplers: An application study at the Zolforata di Pomezia degassing area (Alban Hills, Central Italy)

Abstract

A new method for measuring H 2S mass flux from the ground, based on the digital analysis of the interference colours produced by the sulphidation of copper passive samplers (CPS), is proposed and discussed in this article. CPS sulphidation has a wide range of linear responses to H 2S doses and can be used together the accumulation chamber method to estimate gas fluxes from natural degassing areas. These are often characterized by the presence of vent centred degassing areas (VCDAs), which are recognizable from the absence or rarefaction of vegetation due to high acid gas concentrations in the soil pores and in the air at ground level. A reference emission curve, accounting for the advective and diffusive components of the flux, can be modelled and used to estimate the total H 2S mass released from each VCDA. The application of this method can be supported by remote sensing analysis that helps identify VCDAs in the field in perivolcanic H 2S degassing areas. As an illustrative application, H 2S gas fluxes from the ground were measured in spring 2007 at the Zolforata di Pomezia degassing area (ZPDA, Alban Hills, Central Italy) using an accumulation chamber internally equipped with CPS. H 2S peak fluxes were measured over the vents after remote sensing assisted identification of the VCDAs. Further measurements were carried out in two ponds and one artificial channel bordering the study area. The total atmospheric flux released at the ZPDA, estimated to be about 1207.6 kg day − 1 , was calculated as the summation of the fluxes from all the H 2S sources, the background flux being negligible.