Changes in the lead content of atmospheric aerosols above the Eastern Channel between 1982/83 and 1994

Lead concentrations in atmospheric particulate matter, along the southern coast of the Strait of Dover have been measured during two sampling campaigns, over a 10 year period. The results point out that lead concentrations have been decreased by a factor of two, from 1982/83 to 1994. This evolution is in good agreement with a general trend to the diminution of lead in atmospheric aerosols above the Eastern Channel and the Southern Bight of the North Sea. It appears that, from 1972 to 1994, lead concentrations have decreased by an order of magnitude, despite the uncertainty of the oldest-values. As established in a similar coastal environment, this decrease in the lead concentrations can be explained by the reduction in the emissions of automotive lead. The evolution of the mass-size distribution is consistent with this last factor; assuming that automotive lead is essentially present in particles smaller than 0.33 μm, the observed decrease of this granulometric class between 1983 and 1994 (7 ng/m3) is close to the measured decrease in the lead concentrations (9 ng/m3). A slight decrease (14%) of the related dry deposition flux has been calculated for the same period. But, if part of the fall-out due to particles larger than 1 μm is approximately constant over the same period (about 430 g/km2 per year), the submicronic flux exhibits a decrease of 70%.