Latitudinal distribution of peroxyacetyl nitrate (PAN) over the Atlantic Ocean

Abstract

Atmospheric concentrations of peroxyacetyl nitrate (PAN) were measured during a cruise of RV Polarstern from Cape Town (South Africa) to Bremerhaven (Germany) in May/June 1998 and at Ny-Ålesund, Svalbard, in March 1998. The continuous in-situ measurements were using electron capture gas chromatography combined with a cryogenic preconcentration technique. The time resolution of the measurements was 10 min with a detection limit of 5 parts per trillion by volume (pptv). The mixing ratios of PAN exhibited a maximum of 1100 pptv in the English Channel and values less than 5 pptv in tropical latitudes between 10° N and 10° S. The latitudinal distribution of PAN showed significantly higher concentrations in the northern hemisphere compared to the southern hemisphere. North of 10° N, daily maximum PAN concentrations normally exceeded 100 pptv. Mean mixing ratios decreased from 244 pptv between 50° N and 54° N to 13 pptv between 20° N and 30° N. Enhanced concentrations were detected in continentally influenced air masses identified by trajectory analysis and simultaneous measurements of black carbon and ozone. Intrusions of air masses from the upper troposphere could not be inferred from trajectory analysis. In temperate northern latitudes, enhanced PAN mixing ratios can be used as an indicator of long-range transport of photochemically active pollutants. Copyright 1999 by the American Geophysical Union.