  Based on its condensed-matter properties, crystal structure, and metallurgy,
which includes a phase diagram with six allotropic phases, plutonium is one of
the most complicated pure elements in its solid state. Its anomalous
properties, which are indicative of a very strongly correlated state, are
related to its special position in the periodic table, which is at the boundary
between the light actinides that have itinerant 5$f$ electrons and the heavy
actinides that have localized 5$f$ electrons. As a foundational study to probe
the role of local electronic correlations in Pu, we use the local-density
approximation together with a continuous-time quantum Monte Carlo simulation to
investigate the electronic structure of a single Pu atom that is either
substitutionally embedded in the bulk and or adsorbed on the surface of a Th
host. This is a simpler case than the solid phases of Pu metal, which must also
include the interactions between Pu 5$f$ electrons on different Pu atoms. For
the Pu impurity atom we have found a Kondo resonance peak, which is an
important signature of electronic correlations, in the local density of states
around the Fermi energy. Furthermore, we show that the peak width of this
resonance is narrower for Pu atoms at the surface of Th than for those in the
bulk due to a weakened Pu 5$f$-ligand hybridization at the surface.
