PH ISOTOPIC COMPOSITION OF AIRBORNE PARTICULATE MATERIAL FROM FRANCE AND THE SOUTHERN UNITED-KINGDOM - IMPLICATIONS FOR PB POLLUTION SOURCES IN URBAN AREAS

Pb isotopic studies of airborne particulate matter, incinerator ash, a nd gasoline have been carried out to determine sources of Pb pollution in urban areas from France and the southern United Kingdom. Pb-206/Pb -207 ratios in gasoline range from 1.061 to 1.094 (average values are 1.084 for France and 1.067 for the U.K.) while for industrially-derive d Pb, Pb-206/Pb-207 ratios vary from 1.143 to 1.155. Natural Pb is mor e radiogenic and literature values for pre-industrial sediments give P b-206/Pb-207 ratios of 1.19-1.20 in France and 1.17-1.19 in the U.K. T he measured Pb isotopic signature of airborne particulate matter refle cts the relative importance of each of these sources, and samples take n from urban areas close to traffic in France and the U.K. show Pb-206 /Pb-207 ratios that vary widely from 1.085 to 1.158. While alkyl-lead additives in gasoline are typically still the dominant source of Pb in urban particulate matter, the relative importance of gasoline-derived Pb has decreased, and as a result other sources (industrial and natur al) can be identified using isotopic studies. This is a consequence of recent EU environmental legislation that significantly limits concent rations of Pb in gasoline and the increased market penetration of unle aded gasoline. In addition, at a given location, the Pb isotopic compo sition of particulate matter can vary considerably due to temporal var iations in sources (i.e., variations in traffic density) and with wind direction.