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

Atmospheric concentrations of peroxyacetyl nitrate (PAN) were measured duri ng a cruise of RV Polarstern from Cape Town (South Africa) to Bremerhaven ( Germany) in May/June 1998 and at Ny-Alesund, Svalbard, in March 1998. The c ontinuous in-situ measurements were using electron capture gas chromatograp hy combined with a cryogenic preconcentration technique. The time resolutio n of the measurements was 10 min with a detection limit of 5 parts per tril lion 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 latitu des between 10 degrees N and 10 degrees S. The latitudinal distribution of PAN showed significantly higher concentrations in the northern hemisphere c ompared to the southern hemisphere. North of 10 degrees N, daily maximum PA N concentrations normally exceeded 100 pptv, Mean mixing ratios decreased f rom 244 pptv between 50 degrees N and 54 degrees N to 13 pptv between 20 de grees N and 30 degrees N. Enhanced concentrations were detected in continen tally influenced air masses identified by trajectory analysis and simultane ous measurements of black carbon and ozone. Intrusions of air masses from t he upper troposphere could not be inferred from trajectory analysis. In tem perate northern latitudes, enhanced PAN mixing ratios can be used as an ind icator of long-range transport of photochemically active pollutants.