Can I close my account and be sure that my posts expropriation be discontinued with my leaving?
Please follow Jeff's directions here to delete your account:
Basically, you need to edit your profile to say "Please delete me" and email firstname.lastname@example.org telling them your user ID (which is 47886) and that you'd like your account to be deleted.
As far as your posts are concerned, I don't believe they will be automatically deleted. The community, however, will work through them to clean them up and remove them as necessary.