1. Institute of Geosciences and Earth Resources, National Research Council of Italy (IGG–CNR), Via G. Moruzzi 1, 56124 Pisa, Italy
2. Earth Sciences Department, University of Pisa, Via S. Maria 53, 56126 Pisa, Italy
3. Institute of Atmospheric Pollution Research, National Research Council of Italy (IIA–CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
4. Institute of Polar Sciences, National Research Council of Italy (ISP–CNR), Strada Provinciale 35d, 00010 Montelibretti, Italy