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

2016, Atmospheric Environment

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 pollution sources in an era of rapidly decreasing industrial pollution. Lead soluble in diluted HNO 3 made up 96 % of total Pb deposition, with the remaining 4 % Pb bound mainly in silicates. Three times higher concentrations of soluble Pb in rime than in snow, and 2.5 times higher concentrations of insoluble Pb in rime than in snow were associated with slightly different Pb isotope ratios. On average, the 206 Pb/ 207 Pb ratios in rime were higher than those in snow. Higher mean 206 Pb/ 207 Pb ratios of insoluble Pb (1.175) than in soluble Pb (1.165) may indicate an increasing role of geogenic Pb in recent atmospheric deposition. A distinct reversal to more radiogenic 206 Pb/ 207 Pb ratios in snow and rime in 2010, compared to literature data from rain-fed Sphagnum 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 Poland and coal combustion in the Czech Republic and Poland. 4 America in that Pb emissions resulting from coal burning exceeded those from traffic (Vile et al., 2000, Novak et al., 2003, Farmer et al., 2016). The former East Germany was the largest, and the Czech Republic the third largest, soft coal producer in the world. The use of alkyl-lead in petrol was banned at the end of 1996 in Germany, 2000 in the Czech Republic, and 2003 in Poland. We hypothesized that, with easing pollution, Pb is well mixed before being deposited in rural locations. This hypothesis can be tested by a comparison of Pb isotope signatures of individual pollution sources with isotope signatures of Pb deposited in the ecosystems. Knowledge of Pb isotope composition of bedrock is needed to distinguish between geogenic and anthropogenic