It looks like line 2412 of EMIS_DEFN.F contains:
WRITE( XMSG,'(A,A16,A,/,I3,A11,A16,A,/,A)' ),
& 'ERROR: Surrogate Species ',TRIM(SPEC),' on emission stream ',
& ISRM, ' has units ',TRIM(UNITS),' which are unkown to CMAQ. ',
& 'Please correct them to proceed.'
CALL M3EXIT( 'CHECK_EMIS_UNITS', 0, 0, XMSG, 2 )
Please refer to the advice in this previous issue: Issue about CCTM in CMAQv5.3.1 - #6 by hogrefe.christian