Natural fluctuation of sulfur species in volcanic fumaroles

We describe and discuss the origin of short-term(hours) variations in the concentration of sulfur species (SO2, H2S, and S8 0) of crater fumaroles discharging at different temperatures (up to 410 .C) from five volcanic systems. Sulfur species can be investigated as an independent subsystem within the whole composition characterizing the fumarolic fluids, their chemical behavior being governed by similar laws in volcanic systems.The measured data are time dependent and show regular oscillations whose amplitude is by far larger than the analytical error. The agreement between the theoretical and the measured concentrations of SO2, H2S, and S8 0 suggests that the formation of dissipative structures can explain the observed oscillations. Accordingly, the periodicity and the amplitude of the compositional oscillations were found to be in strong relationwith the entropy excess of the non-equilibrium systems under investigation. The results of our study suggest that the amplitude and magnitude of short-term natural (self-induced) fluctuations of the sulfur species caused by the presence of the dissipative structures, and their comparisonwith the compositional variations of other subsystems, should be taken into serious account for geochemical monitoring purposes. © 2008 Walter de Gruyter - Berlin - New York.