| Bromine oxide has been measured in the plumes of several passively degassing volcanoes. In
previous studies we compared field measurements from Mt. Etna, Italy with results from a
one-dimensional model that was initialised with volcanic plume compositions according to a
thermodynamic model. Assuming a so-called effective source region where plume air is
being mixed with ambient air at still high temperatures we were able to reproduce the
measurements for BrO and SO2 very well (Bobrowski et al., 2007). The model resolves the
vertical dilution of the plume and includes a parameterisation for the horizontal
entrainment of background air as well as a detailed set of gas-phase and aqueous-phase
reactions.
This presentation will discuss long-range effects of volcanic plumes on tropospheric
chemistry and will address a number of important open questions such as the speciation of
chlorine, sulphur - halogen interactions and especially the interaction of halogens with
mercury. I will present new model results to help identify the involved processes and
implications and to direct future field work. |