Snow lead isotopes

In a climax to his sediment studies, Patterson reported tersely that we have found the composition of lead in snow to be very different from the composition of lead which has been deposited on the ocean floors during the past 100,000 years. The lead in Lassen Volcanic National Park had a signature mix of lead isotopes, a characteristic fingerprint identifying it as a... 

W. Chisholm, K. J. R. Rosman, C. F. Boutron, J, P. Candelone, S. Hong, Determination of lead isotopic ratios in Greenland and Antarctic snow and ice at picogram per gram concentrations. Anal. Chim. Acta, 311 (1995), 141-151. 

Gulson BL, Davis JJ, Mizon KJ et al (1995a) Sources of lead in soil and dust and the use of dust fallout as a sampling medium. Sci Total Environ 166 245-262 Gulson BL, Mahaffey KR, Mizon KJ et al (1995b) Contribution of tissue lead to blood lead in adult female subjects based on stable lead isotope methods. J Lab Clin Med 125 703-712 Hageman KJ, Simonich SL, Campbell DH et al (2006) Atmospheric deposition of current-use and historic-use pesticides in snow at national parks in the western United States. Environ Sci Technol 40 3174-3180... 

Analyzing the samples back at Caltech, Patterson, Masayo Murozumi, and Chow demonstrated that polar ice is naturally extremely pure but that snow deposited in modern times on Greenland contained roughly 100 times more lead than did preindustrial snow. Most of the lead deposits dated from the twentieth century. Geochemists later used the unique ratio of lead-206 and lead-207 isotopes in the lead to prove that these deposits originated in the United States. 

Natural isotopic variations in lead in polar snow and ice as indicators of source regions... 

The first measurements of Pb isotopes in Greenland snow were reported in 1993 (45). The samples were taken from a 10.7 m long, 10.5 cm diameter, snow core drilled at Summit, central Greenland, in 1989 (72°35 N, 37°38 W, mean annual accumulation rate 21.5 g cm year ). Cores were drilled with a polycarbonate auger to minimise the Pb contamination. The core contained snow deposited between the years 1967 and 1988. The 3.23 km elevation of the site provided representative samples of free tropospheric aerosols. An expanded data set and a more complete description and interpretation of these data were later reported by Rosman et al. (46). The latter included samples from the upper part of a 70 m snow core including snow deposited between 1960 and 1974. Data on all four Pb isotopes were given for these samples ( Pb/ Pb, ° Pb/ ° Pb and Pb/ °" Pb). Aliquots of these samples were also analysed for heavy metals by Boutron et al. (47) who showed there was a reduction in the Pb concentration in Greenland snow after 1970, which they attributed mainly to the reduction in the use of alkyl-leaded petrol. 

Doring, T., Schwikowski, M., and Gaggeler, H.W. (1997) The analysis of lead concentrations and isotope ratios in recent snow samples from high alpine sites with a double focusing ICP-MS. Fresenius J. Anal. Chem., 359, 382-384. 

Atmosphere. Few data are available (Table 25) on the isotopic composition of lead in the atmosphere. The low lead content of air requires some concentrating mechanism before analysis is feasible, and snow has been used (Tatsumoto and Patterson, 1963 Chow, 1968a). This lead may be due to lead from gasoline widely carried as aerosols (Chow and Johnstone, 1965), as they are rather similar in isotopic composition. 

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