Seasonal variations in the origin of lead in snow at Dye 3, Greenland

The isotopic composition and concentration of lead has been measured in fresh and slightly aged snow collected at Dye 3 in southern Greenland during one full year. The lead concentration displayed large variations ranging from 14–3016 pg/g in April (spring) to 3–6 pg/g in September (summer) while the isotopic ratios changed in regular manner during the year. The 206Pb/207Pb ratios were ∼1.15 from spring to mid-summer snow, and increased in late summer to early autumn, reaching ∼1.20 in winter. These isotopic data indicate that the lead in the autumn to winter snow originated in North America, while that in spring to mid-summer snow is from Eurasia.