A stable lead isotopic investigation of the use of sycamore tree rings as a historical biomonitor of environmental lead contamination

• Published in: The Science of the total environment Vol. 362; no. 1; pp. 278 - 291
• Main Authors: Patrick, Gavin J., Farmer, John G.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01-06-2006; Elsevier Science
• Subjects: Acer - chemistry; Acer pseudoplatanus; Analysis methods; Applied sciences; Atmospheric pollution; Biomonitoring; Dendrochemistry; Environmental Monitoring - methods; Environmental Pollutants - analysis; Environmental Pollutants - history; Exact sciences and technology; History, 19th Century; History, 20th Century; Isotopes; Lead; Lead - analysis; Lead - history; Lead isotopes; Metallurgy; Mining; Pollution; Scotland; United Kingdom; Scotland; Great Britain; Europe; British Isles, Scotland; Atmospheric pollution; Lead; Lead isotopes; Biomonitoring; Dendrochemistry; Isotopic analysis; Historical reconstruction; Acer pseudoplatanus; Historical aspects; Biological indicator; Dendrochronology; Aceraceae; Heavy metal; Lead 207; Lead 206; Dicotyledones; Angiospermae; Pollution source; Air pollution; Spermatophyta; Performance; Anthropogenic factor
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2005.12.004

The validity of the use of sycamore (
Acer pseudoplatanus) tree-rings for the reconstruction of atmospheric lead pollution histories was investigated. Tree cores spanning 1892–2003 were collected from several sycamores from the eastern shore of Loch Lomond, Scotland, an area with no local point sources of lead emission. The lead concentration and
206Pb/
207Pb profiles of the Loch Lomond region cores were compared with corresponding data for the
210Pb-dated loch sediment, and also with data for moss of known age from a Scottish herbarium collection. Two of the seven sycamore cores showed the same lead concentration trend as the lead flux to the loch, the rest having no similarity to either each other or the loch sediment record. Two further sycamore cores showed some similarity in their temporal
206Pb/
207Pb trends to those seen in the sediment and moss records, but only in part of their profiles, whilst the
206Pb/
207Pb ratios of the other sycamore cores remained relatively unchanged for the majority of the time covered, or exhibited an opposite trend. The
206Pb/
207Pb ratios of the tree cores were also mostly higher than those of the previously established records for any given time period. Tree cores covering 1878–2002 were also collected along transects from Wanlockhead and Tyndrum, two areas of former lead mining and smelting associated with distinct
206Pb/
207Pb ratios of 1.170 and 1.144, respectively. The Wanlockhead tree cores exhibited a generally decreasing trend in lead concentration with both time and distance from the lead mine. The characteristic
206Pb/
207Pb ratio of 1.170 was observed in samples close to the mine but a decrease in the influence of the mine-derived lead was observed in more distant samples. The tree sampled at Tyndrum showed elevated lead concentrations, which decreased with time, and a fairly constant
206Pb/
207Pb ratio of ∼
1.15 reflecting input from the mine, features not observed in any other trees along the transect. Overall the data suggest that sycamore tree-ring analysis is an unsuitable method for obtaining records of historical lead deposition in areas with no large local lead input, although it can reveal some information about the temporal and spatial influence of point source emitters. The unsuitability probably arises from the number of active annual rings in a single year, the post-uptake radial translocation of elements, the relative importance of the different routes of uptake, and the soil depth(s) from which trees draw nutrients.