Samples of tree bark, which accumulate airborne material, were collected from seven locations in the UK to provide an indication of the magnitude and source of lead pollution. Measurement of the Pb content and Pb-206/207 stable isotope ratio by inductively-coupled plasma mass spectrometry revealed significant differences between the sites. The concentration of Pb varied over almost four orders of magnitude from 7.2 to 9,600 μg g, the maximum values being found near a 'secondary' Pb smelter. The Pb-206/207 isotope ratios varied from 1.108 +/0.002 to 1.169 +/0.001. The lowest Pb concentrations and highest isotope ratios were detected in bark samples from the Scilly Isles, reflecting the low level of industry and road traffic. In contrast, samples obtained from a city centre (Sheffield) and near a motorway (M1) contained 25 to 46 μg g Pb and recorded the lowest Pb-206/207 ratios. Higher concentrations in the vicinity of a coalfired power station recorded a Pb-206/207 ratio of 1.14, suggesting a significant contribution from fly ash. The relative contribution of lead from petrol (Pb-206/207 = 1.08) and other sources such as coal (Pb-206/207 = 1.18) were thus estimated using mass balance equations. Tree bark near the lead smelter recorded an intermediate Pb206/207 ratio of 1.13, reflecting the processing of material of mixed origin. Bellis, D.J., Mcleod, C.W. and Satake, K., 2002. Pb and Pb-206/Pb-207 isotopic analysis of a tree bark pocket near Sheffield, UK, recording historical change in airborne pollution during the 20 Century. Science of the Total Environment, 289, 169-176. Abstract: A section of tree trunk (beech, Fagus sylvatica) containing a bark pocket progressively enclosed at the junction of two branches was collected from a semi-rural location near Sheffield, UK. According to the annual growth rings, the bark pocket formed between circa 1919 and 1998 (the date of felling). The bark pocket was divided into consecutive samples of differing radial depth (and thus age), that were analysed by ICP mass spectrometry. The Pb concentration varied from 7 to 78 mg kg and the Pb206/Pb-207 isotope ratio from 1.11 to 1.15. In contrast, the current surface bark contained 46 mg kg Pb and recorded a Pb-206/Pb-207 ratio of 1.11. The changing elemental and isotopic composition of the bark pocket recorded historical change in the level and sources of airborne Pb pollution. An overall increase in Pb concentration with time was accompanied by a progressive reduction in Pb-206/Pb-207 from circa 1935 to 1943. Mass balance calculations indicated that Pb additives in petrol contributed significantly to the rise in concentration, accounting for a maximum of 50 per cent of the total Pb for circa 1986 to 1998, but that other sources were generally dominant. The highest Pb concentrations were recorded from circa 1951 to 1973, suggesting a high A section of tree trunk (beech, Fagus sylvatica) containing a bark pocket progressively enclosed at the junction of two branches was collected from a semi-rural location near Sheffield, UK. According to the annual growth rings, the bark pocket formed between circa 1919 and 1998 (the date of felling). The bark pocket was divided into consecutive samples of differing radial depth (and thus age), that were analysed by ICP mass spectrometry. The Pb concentration varied from 7 to 78 mg kg and the Pb206/Pb-207 isotope ratio from 1.11 to 1.15. In contrast, the current surface bark contained 46 mg kg Pb and recorded a Pb-206/Pb-207 ratio of 1.11. The changing elemental and isotopic composition of the bark pocket recorded historical change in the level and sources of airborne Pb pollution. An overall increase in Pb concentration with time was accompanied by a progressive reduction in Pb-206/Pb-207 from circa 1935 to 1943. Mass balance calculations indicated that Pb additives in petrol contributed significantly to the rise in concentration, accounting for a maximum of 50 per cent of the total Pb for circa 1986 to 1998, but that other sources were generally dominant. The highest Pb concentrations were recorded from circa 1951 to 1973, suggesting a high