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by vilhelm_s
293 days ago
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The radioactive lead isotopes come from decay of uranium and thorium, so lead from different mines will have different isotope ratios depending on how much U and Th happened to be in that ore. Not all leaded gasoline was the same either: > 206Pb/207Pb ratios commonly found in Pb ores
throughout the world range between 16.0–18.5 and 1.19–1.25,
respectively (Hansmann and Köppel, 2000). Exception to this
rule is the commonly used Pb ore from the Broken Hill deposit,
Australia, which is characterised by extremely low 206Pb/207Pb
ratios (1.03–1.10). On the other hand, Pb originating from the
Mississippi Valley ore deposit, USA, exhibits significantly more
radiogenic Pb isotopic composition (206Pb/204Pb N20.0;
206Pb/207Pb= 1.31–1.35) (Doe and Delevaux, 1972). American
leaded gasoline reflected therefore significantly higher
206Pb/207Pb ratios compared to European gasoline (Fig. 1). The
introduction of the European leaded gasoline around 1945
resulted in a steep decrease of the 206Pb/207Pb ratio of
atmospheric Pb (Weiss et al., 1999; data from peat deposits).
The isotopic composition of leaded gasoline was to some extent
dependent on economical factors, such as the availability and
price of Pb ores and has evolved due to the different Pb ores used.
For example, Pb used for French leaded gasoline originated from
Australian, Moroccan and Swedish ores and the contribution of
the separate ores changed during time (Véron et al., 1999). It is
therefore indispensable to gather data concerning the origin of
gasoline used in studied regions. [from https://sci-hub.ru/https://doi.org/10.1016/j.envint.2007.10....] |
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