6533b86dfe1ef96bd12c9d84

RESEARCH PRODUCT

Atmospheric dispersion of volcanic CO 2 at Vulcano island

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Abstract Intensive carbon dioxide emanations occur throughout the island of Vulcano (Aeolian Archipelago, north of Sicily, Italy). The main sources of CO 2 on the island are the hot fumaroles (∼500°C) of the northern ridge of the La Fossa crater, the fumaroles of the Baia di Levante and the emission areas spread out both on the slopes of the cone and in the nearby plain. The carbon dioxide from the soil can be considered as being emitted at air temperature. In this work, CO 2 concentrations in the air over the island are estimated by means of two numerical codes. This paper takes advantage of the parallel knowledge gained from a previously written paper for SO 2 emissions from the La Fossa volcanic cone (J. Volcanol. Geotherm. Res., 75 (1997) 283). Here the attention is focused on CO 2 and on the roles the different CO 2 sources play in the inhabited area of Vulcano Porto village. In the model chain, the wind flow is simulated using a 3D mesoscale meteorological model for complex terrain. The simulations are performed for the most significant large-scale wind conditions derived from a meteorological analysis of the region. Flow model outputs are then used by way of a Lagrangian particle model to simulate the dispersion of the gas and to calculate the concentrations. The space and time evolution of gas concentration is discussed for various sources and output rates. Simulations show that the contributions to the concentrations at the inhabited area of Vulcano Porto village of: (1) the cone slopes and the La Forgia Vecchia emitting areas; and (2) of the crater fumaroles are both negligible. The main contribution comes from the soil emission at the volcano feet. Results agree well with field measurements, indicating a sharp decrease in CO 2 concentration downwind, and nocturnal peaks of few hundred ppm in the areas emitting 10 −3  cm 3 (CO 2 STP)/cm 2  s. The approach shows the absence of any risk to population at the present emission rates.