Can magmatic volcanoes produce black carbon aerosol at powerful explosive eruptions?

Volcanoes are not traditionally considered to be significant sources of black carbon particles for the stratosphere. The main reason for this well-established view is the absence of appreciable traces of black carbon in volcanic emissions. Recently (Zuev et al., 2014), proposed a new hypothesis of formation and injection of nanodispersed carbon into the stratosphere during powerful explosive volcanic eruptions due to conversion of carbon-containing volcanic gases into black carbon particles. Critical analysis of this hypothesis and new observational data showed that it does not contradict the existing ideas about the principal possibility of this process, but can and should be significantly supplemented and corrected. Analysis of physicochemical processes in volcanic column showed the possibility of formation of the following types of black carbon particles: single highly dispersed particles or their small fractal aggregates, particles of fibrous or encapsulate types associated with pyroclasts, graphite-like pyrocarbon particles.Moreover, the formation of particles of the second and third types is energetically more accessible than that of the first type. Data on the detection of carbonаceous particles in the stratosphere and volcanic ash confirm the possibility of formation of all types of predicted particles and their identity with particles produced by known technological processes and detected after powerful volcanic eruptions in Kamchatka (Russia). The main limiting factors determining both the possibility and the lower boundary of the conditions for the formation of particles of different types have been identified: temperature and concentration of carbon-bearing gases in the volcanic column. For plinian-type eruptions, these parameters appear to be insufficient for the formation of black carbon particles in appreciable amounts and their accumulation in the stratosphere, which contradicts the previously mentioned hypothesis. All potentially formed black carbon remains in volcanic ash and sediments.