Pb isotopic ratios in airborne PM10 of an iron/metal industrial complex area and nearby residential areas: Implications for ambient sources of Pb pollution

This study examined four stable isotopic compositions of Pb in the PM₁₀ (²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb) along with the ambient Pb concentrations in two residences relative to their proximity to an iron and metal industrial complex (IMIC) as well as an industrial site located within the boundary of the IMIC. In addition, eight potential emission sources were investigated for stable isotopic compositions of Pb. The wintertime Pb isotopic ratios for ²⁰⁸Pb/²⁰⁶Pb for ambient samples of an industrial sampling site (ISS) were closer to those of the residential ambient air concentrations measured at closer proximity to the IMIC (RA1) compared to another residential area located further away (RA2). This finding suggests that the ambient Pb sources were more similar between RA1 and the ISS than between RA2 and the ISS. In contrast, the summertime Pb isotopic ratios for the ambient samples of the ISS were not similar to those for RA1, which in turn were similar to those for RA2. During the summer, it is suggested that motor vehicle emissions appear to be a potential source of Pb in the two residential areas. For the ISS, neither ²⁰⁷Pb/²⁰⁶Pb nor ²⁰⁸Pb/²⁰⁶Pb ratios showed a clear seasonal pattern. However for the ambient samples of the two residential areas, both the ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios exhibited a seasonal pattern, with relatively higher mean ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb ratios during the summer season. It was further confirmed that the ambient Pb concentrations were significantly higher at the ISS than those for RA1, which in turn were significantly higher than those for RA2. At all three sampling sites, high enrichment factor values (≥ 475) were found for Pb.