You could start by deleting your email, name and any profile data... by choosing not to show them in your profile setting space (update your profile), remove your pic etc.....
That's the most, then if you want to delete your profile email to the webmaster and ask, sure he will help you...but since looks like you are concerned of your data, deleting them should be the most part...then just don't log in here anymore...if you've decided to do not attend here anymore..
Good luck whatever you decide..