Author(s)

A. Thielmaim, A.S.H. Prevot and J. Staehelin

Abstract

Nitrogen oxides (NOx=NO+NC>2), total reactive nitrogen NOy, ozone (Og), JNO% and volatile organic compounds (VOC) were measured for 10 weeks during spring and summer 1998 in the highly polluted Milan agglomeration. The concentrations during the episode of June 19 to 21 are analyzed. During this period ozone peaks at 160 ppb, NOy at 36 ppb. The high NOz/NOy-ratio in the afternoon indicates aged air masses reaching the station. We refer to NOz as the difference between NOy and NOx. It stands for NOx consumed during the photochemical aging of the air mass. Depending on the origin of the air mass the limitation of the ozone production shifts between VOC- and N

Keywords