I think you need to read the attribute page in details but you mostly get it apparently.
http://boost-log.sourceforge.net/libs/log/doc/html/log/tutorial/attributes.html

Basically, you don't associate attribute to loggers but to log record.
In your case I think the simplest way would be to have a different logging macro (or function),
that would do the log record setup and send manually but will add necessary attributes in the middle.

See the example of manual logging (or see the boost log macros implementations):

void manual_logging()
{
    src::severity_logger< severity_level > slg;

    logging::record rec = slg.open_record(keywords::severity = normal);
     /// HERE ADD NECESSARY ATTRIBUTE THAT WILL BE FILTERED BY SINKS
    if (rec)
    {
        logging::record_ostream strm(rec);
        strm << "A regular message";
        strm.flush();
        slg.push_record(boost::move(rec));
    }
}