ABSTRACT
It is known that surface blackening is caused by the carbonaceous particles embedded in the black crusts, which are emitted into atmosphere by combustion processes. However, the studies performed so far on this topic have concentrated only on the qualitative characterisation of particle morphology and elemental composition by optical and electron microscopy, with the aim of identifying the combustion sources (Carretero & Galan 1996, Chabas & Lefèvre 1996).
