I would have too much trouble keeping up with "what's-in-where" if I had different PSK's for different environments.

I have my baseline EDC that I stuff my pockets with regardless of where I'm going (airline travel excluded of course).

I live in a medium-sized city (Baton Rouge) and figure the same problems (shelter, water, food, first aid, etc) would be the similar as if I were in the woods if we encountered a 9-11 level problem (no twin towers but plenty of chemical plants)

My "field pouch" (with potable water tabs, space blanket, N-95 respirator, etc) that lives in my EDC backpack gets transfered over to my camelback if I'm going hiking.