Air-Water Distribution of POPs Along a North-South Atlantic Transect

To study the transport of POPs from the northern hemisphere to the southern, cruises were carried out collecting aerosol and surface water samples where different classes of organic pollutants were determined. The content of polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), 1,1-dichloro-2,2-bis(4-chlorophenyl)ethene (4,4′-DDE), and polyaromatic hydrocarbons (PAHs) were determined from the island of Texel (The 29 Netherlands) to Walvis Bay (Namibia) and Cape Town (South Africa).The concentrations of HCB range from 2 to 9 pg L-1 in water and from 56 to 145 pg m-3 in air.
Concentrations of 4,4’-DDE in water ranged from 0.3 to 1.4 pg L-1, which is similar to the values found in previous studies carried out in the North Atlantic (0.4–0.6 pg L-1). Atmospheric 4,4’-DDE concentrations range from 0.1 to 0.9 pg m-3 were somewhat smaller than the values of 1.3–6.3 pg m-3 observed in the same area during one cruise carried out in April 1990.
During the same cruises the contents of polycyclic aromatic hydrocarbons (PAHs) and one emerging class of pollutants (polychlorinated naphthalenes, PCNs) were determined. The highest PAH concentrations occurred in the European samples, and in samples close to West Africa and South Africa. Consistently low PAH concentrations were measured in the southern hemisphere open ocean samples (190-680 pg/m3). Concentrations showed a diurnal cycle, the day/night ratios of phenanthrene, 1-methylphenanthrene and fluoranthene were typically ~1.5-2.5:1. The mechanisms causing this pattern are not understood at present, but dynamic environmental processes are implicated. The highest PCN concentrations occurred in the European samples, but high values were also detected off the West African coast, and in the sample taken closest to South Africa.