Trace elements from fumaroles at Vulcano Island (Italy): rates of transport and a thermochemical model

This paper reports a semi-quantitative estimate of fluxes of some trace elements (As, Bi, Cd, Pb, Tl, and Zn) emitted from fumaroles at La Fossa crater, on the island of Vulcano. In addition, the paper presents a thermochemical model of the deposition of solid species during the cooling of volcanic gases as a function of temperature. A free-energy minimization method was used. Computations indicate that lead condenses as PbS between 428° and 277°C and as PbCl2 between 252° and 202°C; Bi2S3 occurs between 428° and 408°C, CdS occurs between 428° and 388°C, and Zn2SO5 occurs only at 428°C. Calculations show, moreover, the occurrence of TlCl between 177° and 102°C. Sulfur occurs below 152°C. The calculated results are in agreement with the depositional sequence observed in a silica sampling tube.