Isotopic trends and background fluxes of atmospheric lead in northern Europe: Analyses of three ombrotrophic bogs from south Sweden

Abstract

Knowledge about the natural atmospheric background deposition rate of lead (Pb) prior to anthropogenic pollution is critical in the understanding of present‐day pollution and for establishing realistic goals for the reduction of atmospheric Pb. We utilize stable Pb isotopes (206Pb and 207Pb) in radiocarbon‐dated peat cores from three ombrotrophic bogs from south Sweden, to calculate fluxes and to survey atmospheric Pb trends prior 3500 BP (the so far known onset of large‐scale anthropogenic pollution). The estimated atmospheric Pb deposition rate was between 1 and 10 μg Pb m2 yr−1 between 5900 and 3700 calendar years BP, which is 100 to 1000 times lower than present‐day deposition rates. The majority of the samples older than 3500 calendar years BP had 206Pb/207Pb ratios ≤1.20, which is significantly lower than unpolluted Swedish mineral soils (206Pb/207Pb > 1.30), suggesting that even the natural atmospheric deposition of Pb was dominated by long‐range transport, rather than local inputs from soil dust. Low 206Pb/207Pb ratios (1.16–1.18) of several samples indicate that this distant transport originated at least partly from early pollution sources. A possible climatic connection with the observed Pb deposition trends is suggested.

Contaminated lead environments of man: reviewing the lead isotopic evidence in sediments, peat, and soils for the temporal and spatial patterns of atmospheric lead pollution in Sweden

“…Based on the more precise chronology available from a few annually laminated sediment records, this peak was centered about AD 80 (Brännv-all et al 1999;Bindler et al 2009). A greater increase in lead concentrations and a sharp decline in 206 Pb/ 207 Pb ratios in sediments began AD 1000, which at least in southern Sweden was likely driven more by long-range transport from mainland Europe and particularly Germany based on atmospheric modeling of historical source regions Brännvall et al 2001a;Klaminder et al 2003), which is in accordance with the distribution of atmospherically transported pollutants based on current atmospheric modeling.…”

“…These changes in isotopic composition during the Roman period were accompanied by an increased deposition of lead to about 0.1 mg Pb m -2 year -1 , which corresponded to a 10-fold increase in Sweden and in other regions. The deposition rate increased a further 10-fold to *1 mg Pb m -2 year -1 by AD 1200 in the Swedish, Swiss, and southern German sites Klaminder et al 2003;Le Roux et al 2005), and in the Harz mining region the increase in lead concentration in the peat records from this area corresponded to at least a 1,000-fold increase in deposition (Kempter and Frenzel 2000;Hettwer et al 2003). This rate of lead deposition to remote sites in south-central Sweden and elsewhere c. AD 1200, *1 mg Pb m -2 year -1 , is comparable to lead deposition rates experienced at these sites in the first decade of the twenty-first century (Swedish deposition data including forest mosses and precipitation chemistry available at ivl.se).…”

“…2), which can be used as a close approximation for the changes in atmospheric lead deposition, lead deposition prior to 3500 BP was dominated by 206 Pb/ 207 Pb ratios characteristic of soil dust from mainland European bedrock and soils, 1.19-1.24 Klaminder et al 2003;Kylander et al 2010). More importantly, the accumulation of lead in the peat records during the mid-Holocene was quite low, approximately 0.001-0.01 mg Pb m -2 year -1 , which is similar to the estimated values in the range of 0.01-0.3 mg Pb m -2 year -1 from sites in Switzerland (Shotyk et al 1998), southern Germany (Le Roux et al 2005, and northwestern Spain (Kylander et al 2005).…”

“…1). These archives include lake sediments in Sweden (Renberg et al 1994;Brännvall et al 1999Brännvall et al , 2001aBindler et al 2001); peat deposits in Sweden Klaminder et al 2003), Spain (Martínez-Cortizas et al 2002;Kylander et al 2005), France (Monna et al 2004a, b;Baron et al 2005), Belgium (De Vleeschouwer et al 2007), Switzerland (Shotyk et al 1998), Germany (Le Roux et al 2005, the UK (Le Roux et al 2004;Cloy et al 2008), and Iceland (Marshall et al 2009); and ice records from Greenland and Devon Island (Hong et al 1994;Rosman et al 1997;Zheng et al 2007). …”

Deciphering human–climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500years (Misten bog, Belgium)

“…Radiogenic isotope signatures of sediments are often used as provenance proxies as they are not affected by erosion and transport (i.e., conservative behavior during the sedimentary cycle, Goldstein et al, 1984). Pb isotopes, particularly in petlands, have been often used as evidence of anthropogenic heavy metal pollution (e.g., Shotyk et al, 1998;Dunlap et al, 1999;Klaminder et al, 2003Klaminder et al, , 2005Ferrat et al, 2012a,b). Another radiogenic isotope system, the Sm/Nd, is less sensitive to trace metal pollution, but Nd isotope data for peat samples are scarce, and have only been measured at a few sites (Blue Cypress in Florida; Kamenov et al, 2009; Etang de la Gruère in Switzerland, Le Roux et al, 2012).…”