In-situ sampling and remote observations of volcanic aerosols.

In order to determine the chemical composition of volatile and nonvolatile particulate matter or/and trace elements (including radioactive nuclides) at the volcanic source and near-source, aerosols can be collected on filter-pack devices and cascade impactors, or optically investigated (in-situ or remote measurements) using compact optical counters, portable photometers and infrared spectrometers, LiDARs, drones and other instruments. Multi-instrument and multi-geometry approaches, including a combination of mobile LiDAR and sunphotometer instruments, a coordinated fleet of drones, coupled Microtops operating at different spectral ranges (Sellitto et al., 2017d), automatic sun tracking photometers with almucantar and principal plane scenarios and other techniques, can provide enhanced observation capabilities of volcanic aerosols and their properties. Aerosol and gas flux and dispersion measurements can be accurately measured using drones to generate plume cross sections equipped with sensors to measure 3D wind vectors, aerosol number size distribution and trace gases. Elemental mass fluxes are obtained by scaling the Xi/SO2 abundance ratios to the SO2 plume flux. Data also provide insight to the heterogenous reactions that occur during near-vent plume emission and expansion.