STABLE LEAD-ISOTOPE RECORD OF LEAD POLLUTION IN LOCH-LOMOND SEDIMENTSSINCE 1630 AD

Stable lead isotope data can yield information on the geochemical orig ins of lead and on its relative contributions from sources such as coa l burning, mining, smelting, and car-exhaust emissions. This extremely detailed Pb-206/Pb-207 profile for dated bottom sediments in Loch Lom ond, Scotland, shows the trends clearly related to the varying nature and extent of anthropogenic lead inputs after 1630. In particular, a s ignificant decline in the Pb-206/Pb-207 ratio of excess lead during 19 29-1991 is attributable to the introduction and use of (Pb-206-deplete d) leaded petrol since the 1920s. This accounts, however, for just 24- 53% of the excess lead deposited since 1929 and less than or equal to 19% of the total excess lead inventory. Deposition of lead from indust rial (and domestic) activities has predominated overall and, on an ann ual basis, until at least the mid-1950s.