The lead-isotope ratio have been used to assess and identify impact of leaded gasoline, coal combustion and mineral activities[ref 1] due to the difference in 206Pb (~52%), 207Pb (~24%) and 208Pb (~23%) isotope ratios. The source of these differences is the decaying of the parent isotopes of 238U to 206Pb, 235U to 207Pb and 232Th to 208Pb. 204Pb is the only stable Pb isotope usually contributing 1% of the total Pb. Differences in 206Pb/207Pb ratio ranges from 1.06 to 1.10 in old Pb ores (e.g. the time of the roman empire), whereas recent mining from radiogenic (high U and Th contents) ores can have 206Pb/207Pb ratios >1.18. Ratios to 204Pb would be the optimal way to assess lead sources, but when using quadropole MS, the resolution does not allow for distinction between 204Pb and 204Hg (6.87% natural). The route of the Galathea3 [figure, ref 2] gave an excellent opportunity to investigate the general patterns in both biota and sediments across the world. Preliminary results indicate sediment ratios ranging between 1.11 and 1.29, and for mussels ratios of 1.06 to 1.35 was found. Reproducibility of certified reference material NIST 981 of 206Pb/207Pb respectively 206Pb/208Pb was 0.13 to 0.35% with recoveries of 98.50 to 100.03%. Geographical differences and comparison with literature values for the different regions will be presented, together with a discussion on the suitability of ICP-quadropole-MS for isotope ratio determinations.
bly isotop ratio; muslinger; sediment; galathea3; Lead isotope ratio; bivalves
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Nordic Conference on Plasma Spectrochemistry, 2008