Aerosol isotopic ammonium signatures over the remote Atlantic Ocean

We report aerosol ammonium 15N signatures for samples collected from research cruises on the South Atlantic and Caribbean using a new high sensitivity method. We confirm a pattern of isotopic signals from generally light (delta N-15 - 5 to -10%0), for aerosols with very low (<2 nmol m(-3)) ammonium concentrations from the remote high latitude ocean, to generally heavier values (815N +5 to +10%), for aerosols collected in temperate and tropical latitudes and with higher ammonium concentrations (>2 nmol m(-3)). We discuss whether this reflects a mixing of aerosols from two end -members (polluted continental and remote marine emissions), or isotopic fractionation during aerosol transport. (C) 2016 Published by Elsevier Ltd.