Lead fluxes and 206Pb/207Pb isotope ratios in rime and snow collected at remote mountain-top locations (Czech Republic, Central Europe): Patterns and sources

During three winter seasons (2009-2011), Pb concentrations were measured in precipitation at 10 high-elevation sites in the Czech Republic, close to the borders with Austria, Germany, Poland, and Slovakia. Soluble and insoluble Pb forms were quantified in snow (vertical deposition), and rime (horizontal deposition). The objective was to compare Pb input fluxes into ecosystems via vertical and horizontal deposition, and to identify the residual Pb polution sources in an era of rapidly decreasing industrial pollution. Lead soluble in diluted HNO3 made up 96 % of total Pb deposition, with the remaining 4 % Pb bound mainly in silicates. Four times higher concentrations of soluble Pb in rime than in snow, and 1.6 times higher concentrations of insoluble Pb in rime than in snow were associated with slightly different Pb isotope ratios. On average, the 206Pb/207Pb ratios in rime were higher than those in snow. Higher 206Pb/207Pb ratios of insoluble Pb than in insoluble Pb may indicate an increasing role of geogenic Pb in recent atmospheric deposition. A distinct reversal to more radiogenic 206Pb/207Pb ratios in snow and rime in 2010, compared to literature data from rain-fed Shagnum peatlands (1800-2000 A.D.), documented a recent decrease in anthropogenic Pb in the atmosphere of Central Europe. Since the early 1980s, Pb concentrations in snow decreased 18 times in the rural south of the Czech Republic, but only twice in the industrial north of the Czech Republic. Isotope signatures indicated that Pb in today’s atmospheric deposition is mainly derived from Mesozoic ores mined/processed in southern Poland and coal combustion in the Czech Republic and Poland.JRC.G.II.6-Nuclear Safeguards and Forensic