While walking through the vaults, Fortunato begins to cough violently, perhaps as a result of the niter that covers the walls of the catacombs. Niter is another name for potassium nitrate, a kind of white salt that is naturally produced and used in a variety of ways. It, apparently, is affecting the air below ground, and this exacerbates the cold symptoms Fortunato already has. Montresor offers him some wine, to take the edge off Fortunato's cough, and Fortunato says,
"I drink [...] to the buried that repose around us."
The word repose may constitute an example of personification. It can describe the action of one who lays down or rests, as though they are sleeping. There are several definitions of the word that could personify the dead, discussing them as though they are still alive and yet merely resting. However, the word can also be used to describe the posture of an inanimate object, like a body, and so, using this definition, it would not be personification.
In the final paragraph, Montresor says, when Fortunato goes silent within the wall, "My heart grew sick." His heart cannot actually grow sick, but people can, and so Montresor personifies his heart in order to express how ill—perhaps with guilt or fear or remorse—he feels. Since the heart is often associated with emotion, it makes sense that Montresor is describing negative emotions and not a physical ailment.