Atmospheric distribution of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs), and non-ortho biphenyls (PCBs) along a North-South Atlantic transect

Air samples were taken on board the RRS Bransfield (typically for 24-72 h), during an Atlantic cruise from the U.K. to Antarctica in October-December 1998, to investigate the global scale distribution of PCDD/Fs and coplanar PCBs. Highest concentrations Of Cl2-8DD/Fs all occurred between 25 and 52 d egreesN; lowest concentrations were measured around similar to 60 degreesS and further south. Cl(3)DFs showed highest overall concentrations (up to 98 00 fg/m(3)), followed by Cl(2)DFs (up to 5300 fg/m(3)) and OCDD (up to 1300 fg/m(3)). Lowest concentrations, measured in the remote Southern hemispher e, were generally 2 orders of magnitude lower than their highest concentrat ions over the North Atlantic. Concentrations of PCB-77 were higher in the n orthern hemisphere, while PCB-126 and PCB-169 exhibited highest concentrati ons around the equator. Evidence was obtained for substantial emissions of PCDD/Fs off west Africa and while in the port of Montevideo, Uruguay. Shift s in PCDD/F profile distribution were observed on increasing distance from source regions, such that those from the most remote locations were dominat ed by Cl3DF (similar to 40% of the total) and OCDD (similar to 20%). Gas-pa rticle partition data was obtained for all samples. Cl4-6DD/Fs showed the w idest range, varying between 10 and 90% of the total in the gas phase, depe nding on location/temperature. The study gave limited evidence for the infl uence of OH-radical initiated depletion reactions of gaseous PCDD/Fs. The g lobal atmospheric burden is estimated to be on the order of 350 kg Sigma Cl 4-8DD/Fs and similar to3 kg Sigma TEQ.