THE LEGACY OF TetraEthylLead (TEL) IN URBAN RIVER SEDIMENT AND ATMOSPHERIC PARTICULATES

Lead concentrations in U.S. urban soil and river sediment ([Pb]) typically exceed those of the natural background (~100 - 400 vs. 10-20 ppm, respectively). In areas where [Pb] have been analyzed as a function of depth [and age], maximum concentrations occur ~ 1970, when lead concentrations in TEL-gasoline maximized. Transport of these high Pb sediments exposes the urban populace to Pb via ingestion of suspended river sediment/eating contaminated soil (e.g. pica children) and/or inhalation of airborne particulates. Attempting to pinpoint sources of lead in urban environments is difficult given the plethora of sources present. In this presentation, two case studies are evaluated to (1) assess if legacy TEL-derived Pb can be identified in urban soils using the ALAS Model (Hurst, 2002); and (2) quantify the impact of TEL-derived Pb in the anthropogenic component of urban soils. The studies include the re-evaluation of a published investigation by Lima et al. (2005) concerning sources of Pb in Pettaquamscutt River Basin sediments (RI) and (2) a lead recycling facility (LRF) that was implicated as the sole source of lead in a northern U.S. urban area. The Pettaquamscutt River Basin study (Lima et al., 2005) apportions sources of anthropogenic lead in sediment among PA coal, Mississippi Valley Type ore, and natural/coal dust sources. The authors conclude that the ALAS Model (depicts temporal variations in leaded gasoline 206Pb/207Pb ratios) cannot be used to identify gasoline lead in the sediment. However, observed Pb isotopic/concentration trends in the sediment demonstrate that both gasoline and coal Pb are present. LRF operations were alleged to be the major source of Pb in a northern US urban area. Although analyses of 60 samples from the LRF, adjacent properties, and a park (never industrialized) indicate the presence of LRF Pb in local soils (< 10%), gasoline derived Pb contributes significantly to [Pb]. Hence, despite numerous sources of Pb in the urban environment (e.g. paint, industry) the legacy of TEL-derived Pb is retained in urban soils. Mitigation of legacy gasoline Pb in soils remains problematic given its ubiquity and due to biases to implicate the “usual suspects”, such as lead paint and local industry.