In order to clarify the origin of lead contamination in gas station, the distribution and the existence of lead in gas station site soil have been investigated. The gas station site soils were collected in accordance with the Soil Contamination Countermeasures Act (SCCA). The total concentration of lead in the site soils were in the range from 8.9 to 4520 mg/kg(n＝22). The lead concentration of the 10 samples were exceed the elution standards based on the SCCA, and the 8 samples were exceed the content standards by 1 mol/L-HCl elution test. It was found that the criteria of SCCA is not enough to identify the origin of lead pollution. The chemical species of anthropogenic lead contaminated in the soil are known to present in such as carbonate, sulfide, hydroxide, and organic complexes. Thus, the existence of lead in the gas station site soils have been estimated by sequential chemical extraction. A large amount of lead eluted from the soil with a high concentration of lead by sequential chemical extraction, but the elution of lead from a low concentration soil was less. These lead easily eluted from gas station site soil was estimated to be anthropogenic origin, but in the samples analyzed were considered to also include those of natural source (HB17-1, HB17-2). It was not possible to determine exactly the origin of the lead contamination in such a chemical extraction. Therefore, the analysis of the origin of contaminated lead using its stable isotopes have been performed. From the historical trends of the lead isotope ratios that has been used in Japan since the Meiji Restoration, if the 207Pb/206Pb ratio is greater than or equal to 0.86, it is assessed that the lead is originates from anthropogenical contamination. On the basis of the lead isotope ratio, 8 samples out of 22 gas station site soils were estimated to be anthropogenically contaminated by lead.
