Elevated Lead and Zinc Contents in Remote Alpine Soils of the Swiss National Park

Abstract

Weathering of bedrock and pedogenic processes can result in elevated heavy metal concentrations in the soil. Small-scale variations in bedrock composition can therefore cause local variations in the metal content of the soil. Such a case was found in the remote alpine area of the Swiss National Park. Soil profiles were sampled at an altitude of about 2,400 m, representing soils developed above different bedrocks. The concentration of lead in the profiles was found to be strongly dependent on the metal content in the bedrock underlying the soil and was strongly enriched in the top 10 cm. The dolomitic bedrock in the study area contains elevated lead concentrations compared with other dolomites. Dissolution of dolomite and accumulation of weathering residues during soil formation resulted in high lead concentrations throughout the soil profile. The enrichment of lead in the topsoil, however, is largely attributed to atmospheric input. The isotopic signature of the lead clearly indicates that it is mainly of natural origin and that atmospheric deposition of anthropogenic lead contributed to about 20 to 40% to the lead concentration in the topsoil on the bedrock with elevated lead concentrations. In the soils on bedrock with normal lead concentrations, the anthropogenic contribution is estimated to be about 75%. Also, zinc was very strongly enriched in the topsoil. This enrichment was closely correlated with the organic matter distribution in the profiles, suggesting that recycling through plant uptake and litter deposition was a dominant process in the long-term retention of this metal in the soil.

Lead biogeochemistry in a central Ontario Forested watershed

“…Total Pb pools in mineral soil and the forest floor estimated using the HNO 3 /H 2 SO 4 digest were 1824 and 87.8 mg m À2 , respectively, which likely overestimate to some extent the amount of pollution Pb in soil. Numerous studies have shown that Pb accumulates in upper soil horizons during periods of high deposition, and Pb concentrations typically decrease dramatically with soil depth reflecting the relative immobility of Pb in soils (Brannvall et al 2001c;Erel 1998;Huang and Matzner 2004;Navratil et al 2004;Nowack et al 2001;. The average Pb concentration in the forest floor at PC1 (HF digest) was 75 mg g À1 , which is far below the lowest biological effect level for Pb of 225-250 mg g À1 reported by Bringmark and Bringmark (2001).…”

Major and trace elements in soils in the Central Pyrenees: high altitude soils as a cumulative record of background atmospheric contamination over SW Europe

“…This notion is supported by data in the literature. Enhanced concentrations of Pb have been reported in remote alpine soils in Switzerland, where Pb isotope analysis indicated that the anthropogenic fraction accounts for 20-75% of total Pb (Nowack et al 2001), i.e., an EF up to ∼4. Similarly, Camarero et al (1998) found an increase in Pb from natural background values of ∼20 mg kg −1 in deep soil layers up to ∼ 100 mg kg −1 (i.e., EF ∼5) in the top organic layer in soils from a catchment in the Central Pyrenees, accompanied by the corresponding change in the Pb isotopic quotient, thus indicating the polluting origin of the excess Pb.…”

The Nature and Distribution of Metals in Soils of the Sydney Estuary Catchment, Australia

“…Metals are present in soils at naturally occurring concentrations, which are determined by underlying geology, the nature of parent material and processes of soil formation (Palumbo et al 2000;Nowack et al 2001;Hooda 2003;Rojo et al 2004) and thus soil may be both a source and sink for these elements. Metals are generally poorly mobile within the soil profile and are not biodegradable, resulting in long residence times (Williams et al 1987;Mermut et al 1996;NSW EPA 2003).…”