One should contact the moderators/admins to discuss this; it can be arranged but there's no way in the software to do it yourself.
Normally when a member wants to close their account we do not delete their posts, because that messes up the flow of some threads, but if there are posts you want to remove for good reasons we are sensitive to that and can do so for your own protection.
I hope you're not planning on leaving, Laurie, but if you are, please contact the moderators to discuss it.