Opensearch with more criteria than just "nodes" and "users"

This query is probably not Opensearch related, but it comes close. I have a site Humanitarian News, where I aggregate newsfeeds with feedAPI, which posts all updates in blogs.

The newsfeeds / blogposts are sorted in 6 different sections (aidnews, aidblogs,...) each submitted by one user (one user for all aidnews feeds e.g.).

I implemented opensearch to create a feed based on a search argument, e.g. "Afghanistan" gives me all the latest news postings on "Afghanistan". But now I would like to search also on "Afghanistan" ONLY in the section "Aidnews" (to e.g. exclude all blogs"). Can I do a search on a node AND on what was posted by a particular user? OR Can I do a search on a node AND the contents of one specific blog?

thanks for any suggestion,

Peter