Build-up solids and soil samples were also examined for morphology
and elemental composition using a Quanta 3D FIB (Focused
Ion Beam) scanning electronic microscope (SEM). The
samples were gold coated to improve conductivity and better image
resolution after mounting on a carbon tape attached to aluminium
studs (Kreider et al., 2010). Elemental compositions of the
particles were determined with an energy dispersive X-ray spectroscope
(EDX) to characterise the heavy metal elements attached
to the particles. The elemental analyses of particles were carried
out from the centre of the particle with an acceleration voltage
of 30 kV, a working distance of 15 mm, and an EDX collection time
of 20 s. Backscattered electron images (BEIs) were also taken over
0.01 mm2 area at a 1000 magnification.