A comparison of lead isotope ratios in the bark pockets and annual rings of two beech trees collected in Derbyshire and South Yorkshire, UK

ICP-MS analysis of the bark pockets and annual rings of two beech (Fagus sylvatica L.) trees collected from Longshaw, Derbyshire and Swinton, South Yorkshire in the UK recorded differences in the Pb-206/(201) Pb isotope ratio. In the Longshaw sample, the Pb-206/Pb-201 isotope ratio of the bark pockets (approximate to 1914-1998, 78-260 mug g(-1) Pb) declined from approximately 1.16 to 1.12, whilst the annual rings ( 1899-1998, 0.2-2.5 mug g(-1) Pb) had a Pb-206/ Pb-207 ratio of approximately 1.18. In the Swinton sample, the bark pockets (approximate to 1919-1998, 7-78 mug g(-1) Pb) declined from 1.15 to 1.11 and the annual rings (1899-1998, 0.2-0.5 mug g(-1) Pb) from 1.18 to 1.15. The data implied that the bark pockets accumulated lead directly from the atmosphere through wet and dry deposition, whilst the annual rings accumulated lead from the soil via the roots. The bark pockets recorded a relative decline in the accumulation of lead from indigenous sources, such as lead smelting and coal combustion (1.17-1.19), and increase in imported sources such as the smelting of Australian ores (1.04) and leaded petrol usage (1.06-1.09). in contrast, the annual rings at Longshaw recorded ratios typical of indigenous lead, whilst the annual rings in Swinton recorded a relatively small decrease in Pb-206/Pb-207 reflecting leaded petrol usage. The decline in Pb-206/Pb-207 of the bark pockets was consistent with the historical decline in Pb-216/Pb-217 of atmospheric lead recorded in peat, lake sediments and archival herbage at other UK locations. (C) 2003 Elsevier B.V. All rights reserved.