Peroxyacetyl nitrate (PAN) distribution over the South Atlantic Ocean

The atmospheric concentration of peroxyacetyl nitrate (PAN) was measured ov er the South Atlantic Ocean in the range between 37 degrees and 70 degrees S in March 1999 in order to investigate its latitudinal distribution and it s role in the NOy chemistry of the remote marine boundary layer (MBL) in th e high latitudes of the southern hemisphere. The measurements were performe d using an automatic gas chromatographic system aboard RV Polarstern. Mean mixing ratios of 62(+/- 21) pptv were obtained between 37 degrees and 49 de grees S. South of 55 degrees S, PAN concentrations were very low with value s of the order of 10-30 pptv. Pronounced diurnal cycles could not be observ ed. The concentrations over the South Atlantic were considerably lower comp ared with the North Atlantic where the MBL is influenced by continental air masses.