Abstract
Lead contamination in soil is a common problem in urban areas. Sacramento is no exception. Seventy soil samples were collected in Sacramento and analyzed by 4-acid digestion followed by inductively coupled plasma- atomic emission spectrometry and inductively coupled plasma-mass spectrometry for 43 elements. In addition to the soil samples collected for this study, 43 soil samples collected and analyzed by the same methods supplemented the data. Twenty-eight additional soil samples collected in central Sacramento were analyzed by hand-held X-ray fluorescence spectrometry for Pb and Zn. Two-hundred and fifty-seven samples collected within the area of Sacramento County from the late 1970s to 1980 by the National Uranium Resource Evaluation and Hydrogeochemical Stream Sediment Reconnaissance Program were analyzed by the United States Geological Survey by 4-acid digestion followed by inductively coupled plasma- atomic emission spectrometry and inductively coupled plasma-mass spectrometry for 42 elements. A prediction map of the lead concentrations in soil from the recent data collected in Sacramento was generated by ordinary kriging. The prediction map shows elevated lead concentrations in soil located in the central, older area of Sacramento where traffic density and industrial activity are spatially and temporally persistent. The historic data collected by the NURE program and a subset of recent data collected for this study, were analyzed independently by factor analysis. Both independent analyses identified three lithogenic factors. One such factor includes correlations among Co, Cr, Fe, Mg, and Ni, which are associated with mafic and ultramafic rocks. Another factor identified by both independent analyses includes correlations among Rare Earth Elements, K, and Rb, which are associated with felsic rocks. The last factor identified by both independent analyses includes correlations among Ca, Na, and Sr, which are associated with felsic rocks enriched in these elements. An additional factor was identified by the recent data, which includes correlations among Pb, Cd, Cu, and Zn associated with anthropogenic contamination from vehicle emissions. The presence of the anthropogenic factor in the new data and its subsequent absence from the NURE data is explained by the greater density of recent soil samples collected within the city of Sacramento where anthropogenic contamination is present.