  Using numerical techniques we study the zero temperature properties of a
substitutional magnetic impurity in a one-dimensional correlated system
described by the Hubbard model with repulsive interaction $U$. We find that,
while the static spin correlation maintains a $2k_F$ periodicity, the charge
correlations show Friedel oscillations with a $4k_F$ periodicity for large
values of $U$. The static on-site susceptibility decreases as the interactions
in the chain are turned on and we interpret this as an increase of the Kondo
temperature. For large values of $U$ the short range antiferromagnetic
correlations dominate over the collective Kondo singlet formation.
