When Paul picks up the dirt and lets it slide through his hands, what do you think this symbolizes?

The dirt symbolizes Paul's connection to nature.... something he'd never felt before. It was also the dirt in which Luis would be buried.... a connection to Luis and the community.

I stared at that dirt in fascination, thinking how odd it was that I had never seen it before. This was the dirt that we lived on. The dirt of the tangerine grove that we burned, and buried, and plowed under, and coated with sand, and landscaped over. Here it was.