Programmable thermal dissociation of reactive gaseous mercury – a potential approach to chemical speciation: results from a field study

Abstract. The use of programmable thermal dissociation (PTD) as an approach to investigating the chemical speciation of reactive gaseous mercury (RGM, Hg²⁺) has been explored in a field study. In this approach RGM is collected on a denuder and analyzed using PTD. The denuder is placed in an oven and the dissociation of the RGM is measured, as a function of temperature, by monitoring the evolution of elemental mercury (GEM, Hg⁰) in real time using laser-induced fluorescence (LIF). The technique was tested in a field campaign at a coal-fired power plant in Pensacola, Florida. Uncoated tubular denuders were used to obtain samples from the plant's stack exhaust gases and from the stack plume, downwind of the stack using an airship. The PTD profiles from these samples were compared with PTD profiles of HgCl₂.