Origin of lead in eight central European peat bogs determined from isotope ratios, strengths, and operation times of regional pollution sources

Lead originating from coal burning, gasoline burning, and ore smelting was identified in ²¹⁰Pb-dated profiles through eight peat bogs distributed over an area of 60 000 km². The Sphagnum-dominated bogs were located mainly in mountainous regions of the Czech Republic bordering with Germany, Austria, and Poland. Basal peat ¹⁴C-dated at 11 000 years BP had a relatively high ²⁰⁶Pb/²⁰⁷Pb ratio (1.193). Peat deposited around 1800 AD had a lower ²⁰⁶Pb/²⁰⁷Pb ratio of 1.168-1.178, indicating that environmental lead in Central Europe had been largely affected by human activity (smelting) even before the beginning of the Industrial Revolution. Five of the sites exhibited a nearly constant ²⁰⁶Pb/²⁰⁷Pb ratio (1.175) throughout the 19th century, resembling the "anthropogenic baseline" described in Northern Europe (1.17). At all sites, the ²⁰⁶Pb/²⁰⁷Pb ratio of peat decreased at least until 1980; at four sites, a reversal to more radiogenic values (higher ²⁰⁶Pb/²⁰⁷Pb), typical of easing pollution, was observed in the following decade (1980-1990). A time series of annual outputs for 14 different mining districts dispersing lead into the environment has been constructed for the past 200 years. The production of Ag-Pb, coal, and leaded gasoline peaked in 1900, 1980, and 1980, respectively. In contrast to other European countries, no peak in annual Pb accumulation rates was found in 1900, the year of maximum ore smelting. The highest annual Pb accumulation rates in peat were consistent with the highest Pb emission rates from coal-fired power plants and traffic (1980). Although maximum coal and gasoline production coincided in time, their isotope ratios were unique. The mean measured ²⁰⁶Pb/²⁰⁷Pb ratios of local coal, ores, and gasoline were 1.19, 1.16, and 1.11, respectively. A considerable proportion of coal emissions, relative to gasoline emisions, was responsible for the higher ²⁰⁶Pb/²⁰⁷Pb ratios in the recent atmosphere (1.15) compared to Western Europe (1.10). As in West European countries, the gasoline sold in the Czech Republic during the Communist era (1948-1989) contained an admixture of low-radiogenic Precambrian lead from Australia.