Fig. 4

Green layer (layer 1 and layer 2, Fig. 2 CS5): a optical microscopic image of green layer, b optical microscopic image of particles show the loss of green coloration of emerald green degraded into lavendulan, c SEM–BSE image of lavendulan particles, d SEM–BSE image of green layer, and elemental maps of e copper, f arsenic, g sodium, h calcium and i chlorine show that arsenic migrated out the particle and diffusion within the whole green layers while the occurrence of copper is limited within green particles