CHEMICAL CONCENTRATIONS OF POLLUTANT LEAD AEROSOLS, TERRESTRIAL DUSTS AND SEA SALTS IN GREENLAND AND ANTARCTIC SNOW STRATA

In this study we report analyses of lead in annual ice layers from the interior of northern Greenland and in annual layers of ice from the interior of the Antarctic continent. We show that lead concentrations increase from <0.001γPb/kg ice at 800 BC to >0.200 γPb/kg ice today in north pole ice sheets, the sharpest rise occurring after 1940, and that the levels of lead in south polar ice sheets are generally below our detection limits before 1940 and rise only to about 0.020 γPb/kg ice after 1940 (in this paper the symbol gamma, γ, means microgram, 10-6 g). The increase of lead with time in north polar snows is ascribed mainly to lead smelteries before 1940 and to burned lead alkyls after 1940. The difference between the concentrations of lead in northern and southern polar snows is ascribed to barriers to north-south tropospheric mixing which originate from meridional circulating cells and which hinder the migration of aerosol pollutants from the northern hemisphere to the Antarctic. Our observations of the chemical concentrations of the common elements in ice from the interior of Greenland and Antarctica can be explained in terms of simple relations among sea salts and terrestrial dusts. We found about ten times more dust in Greenland interior ice (35 γ/kg) than in Antarctic interior ice (~2 γ/kg), but found twice as much sea salt in Antarctic interior ice (110 γ/kg) than in Greenland interior ice (67 γ/kg). We found that the proportions of sodium, chlorine, magnesium, calcium, and potassium adhered closely to sea salt ratios in ices that were relatively free of silicate dusts, even when the concentrations of sea salts decreased from 1100 γ/kg in NW coastal Greenland ice to 110 γ/kg in Rockefeller Plateau ice in the Antarctic interior. We also found that the amounts and chemical composition of silicate dusts in Greenland were no different in coastal and interior ices, averaging 3 γ Mg, 5.6 γCa, 2.0 γK, 0.1 γTi and 6.8 γSi per kg ice respectively in the interior. We found that there are seasonal variations in the amounts of pollutant lead, sea salts and silicate dusts in the snows, pollutant lead and sea salts being two or three times more concentrated in winter than in summer snows, while silicate dusts were three times more concentrated in spring than in winter snows. The above interpretation, which unifies all the data, is consistent with most related chemical and meteorological observations at temperate latitudes. © 1969.