Application of Lead Isotopic Ratios in Atmospheric Pollution Studies in the Valley of Mexico

Lead isotopic studies of airborne particulate matter, gasoline and other environmental samples have been carried out to determine possible sources of lead pollution in the Metropolitan Zone of the Valley of Mexico. 206Pb\207Pb ratio in gasoline was 1.1395 (plus_minus) 0.0165 and 1.071 (plus_minus) 0.008 for industrially-derived lead as a mean. Natural lead is more radiogenic with values from 1.2082 (plus_minus) 0.022 to 1.211 (plus_minus) 0.108. The measured Pb isotopic signature of airborne particulate matter reflects the relative importance of each of these sources. The 206Pb\207Pb ratio was 1.179 (plus_minus) 0.105 as a mean. The relative importance of gasoline has decreased, and, therefore, other sources (natural and industrial) can be identified by means of isotopic studies. This is a consequence of the introduction of unleaded gasoline as mandaped by strictest environmental regulation.