GEOCHEMISTRY OF ENVIRONMENTAL LEAD IN SACRAMENTO, CALIFORNIA

The City of Sacramento sits near the eastern boundary of the Central Valley and the foothills of the Sierra Nevada, with a Mediterranean climate characterized by hot dry summers and cool wet winters. Between 1989-2004, Sacramento County reported >250 local children with Pb poisoning, mostly in urban minority populations. Although household sources of Pb are major contributors, the possibility of roadway and soil sources has not previously been investigated in the region. No significant natural sources of Pb exist locally, so all Pb in excess of levels typical for the siliciclastics that dominate the region (<<50 mg/kg) is anthropogenic. Analyses of the geochemistry of urban soils and surficial sediment show dramatic enrichment of Pb throughout the Sacramento region. Concentrations of Pb range from low levels of ~15 mg/kg to over 1500 mg/kg. In all cases, high Pb concentrations are only found within the top 10-20 cm below the surface. Preliminary analyses of the lateral distribution of Pb concentrations show a possible relationship between high soil Pb and the distribution of child lead poisonings, although more data are required. Significant correlations are found between Pb and the concentrations of Cd (0.1-10.0 mg/kg) and Zn, (50-1000 mg/kg) suggesting a common roadway source. No clear relationship is yet evident between Pb distribution and potential sources such as individual roadways, industrial centers, and older housing, although decreases are seen with distance from some major roadways. This study demonstrates the immediate need for higher geochemical sampling densities in Sacramento and other cities. Understanding the distribution and geochemistry of environmental Pb is critical for designing strategies to protect children in this and other cities in a similar climatic setting.