Update description

This update includes all submissions until 11 April 2013 from the 2013 Emission Reporting Round for the year 2011
--> Main pollutants were gridded for the year 2011 with the latest available submissions
--> HMs (Cd, Hg, Pb) and POPs (PCDD/PCDF, HCB, B[a]P) were gridded for 2011 on national total level