The lead content and isotopic composition of british coals and their implications for past and present releases of lead to the UK environment

Abstract

More than 60 coal samples, predominantly from the principal coalfields of England and Wales (25) and Scotland (30), were analysed for lead by AAS and for stable lead isotopes by ICP‐MS. While the average lead content of Scottish coal, 23.9 mg kg−1, was more than double that of coal from England and Wales, 11.0 mg kg−1, the corresponding mean 206Pb/207Pb ratios (± 1 s.d.) were nearly identical, at 1.181±0.011 and 1.184±0.006, respectively. In the light of the lead isotopic signatures of British coals and of both indigenous (206Pb/207Pb ∼ 1.17) and imported Australian (206Pb/207Pb ∼ 1.04) lead ores, an approach based on estimated lead emissions from these sources and the deconvolution of the historical lead and 206Pb/207Pb records preserved in lake sediments, peat bogs and archival herbage material indicates that coal combustion became an increasingly significant contributor to atmospheric lead deposition in the UK during the period 1830–1930, especially after the onset of England’s decline as a major location of lead mining and smelting in the late‐19th Century. Since 1930 and the introduction of leaded petrol, the atmospheric 206Pb/207Pb ratio in the UK has been strongly influenced by car‐exhaust emissions of comparatively 206Pb‐depleted lead of predominantly Australian origin, counter‐balanced to some extent by coal‐combustion emissions of lead, although these have fallen dramatically since the mid‐1950s. Nevertheless, with the introduction and substantial uptake of unleaded petrol in the UK during the last decade, even the declining releases from coal, along with contributions from other sources, are continuing to affect the atmospheric lead content and 206Pb/207Pb ratio.