After derivatization, the concentration of levoglucosan was determined using a GC/MS (7890B/5977B, Agilent, USA) operating at an ionization energy of 70 eV in EI mode. Statistical analysis. seasons were analyzed via Donifef-ewreanycaens ainlysPisMo2f.5vcaorinacnecnetr(AatNioOnsVaAn...