  The chemical composition of the solar corona is different from that of the
solar photosphere, with the strongest variation being observed in active
regions (ARs). Using data from the Extreme Ultraviolet (EUV) Imaging
Spectrometer (EIS) on Hinode, we present a survey of coronal elemental
composition as expressed in the first ionisation potential (FIP) bias in 28 ARs
of different ages and magnetic flux content, which are at different stages in
their evolution. We find no correlation between the FIP bias of an AR and its
total unsigned magnetic flux or age. However, there is a weak dependence of FIP
bias on the evolutionary stage, decreasing from 1.9-2.2 in ARs with spots to
1.5-1.6 in ARs that are at more advanced stages of the decay phase. FIP bias
shows an increasing trend with average magnetic flux density up to 200 G but
this trend does not continue at higher values. The FIP bias distribution within
ARs has a spread between 0.4 and 1. The largest spread is observed in very
dispersed ARs. We attribute this to a range of physical processes taking place
in these ARs including processes associated with filament channel formation.
These findings indicate that, while some general trends can be observed, the
processes influencing the composition of an AR are complex and specific to its
evolution, magnetic configuration or environment. The spread of FIP bias values
in ARs shows a broad match with that previously observed in situ in the slow
solar wind.
