Since you already set a new password and email, you should be on the safe side but if you want to lock this account, simply set your "Secret Question & Answer" then try to recover it using the same method (it automatically locks your account [refer to this thread]).

On a side note: It's a bit weird that you want your account to be blocked/locked and yet you've joined some bounty campaigns.

---

Just go to each of the posts (on the topic itself) > Look for "delete button" on upper right corner of each post.