MULTIVARIATE ANALYSIS OF LEAD IN URBAN SOIL IN SACRAMENTO, CA

Despite years of efforts to reduce pollution levels, soil Pb contamination remains a common problem in urban areas. 113 soil surface samples were collected throughout Sacramento, California, and analyzed by ICP-AES and ICP-MS for 43 elements; a supplementary dataset for Pb was collected by ED-XRF on 28 additional samples. A prediction map of Pb concentrations in soil was generated by ordinary kriging of the spatially distributed data. The prediction map shows elevated lead concentrations in soil located in the central, older area of Sacramento where traffic density and industrial activity have been spatially and temporally persistent. Historic data from the National Uranium Resorce Evlauation, reformatted by the USGS, and a subset of recently collected data were analyzed independently by factor analysis. Both datasets can be described by three lithogenic factors. One such factor includes correlations among Co, Cr, Fe, Mg, and Ni, which may be related to mafic and ultramafic rock input. A second factor includes correlations among Rare Earth Elements, K, and Rb, which may reflect felsic rock input. The last factor identified includes Ca, Na, and Sr, which may similarly be associated with felsic rocks. The recent, higher-resolution dataset revealed an additional factor that was not present in the NURE database. This final factor is dominated by Pb, Cd, Cu, and Zn; and is interpreted as an anthropogenic factor associated with contamination from several potential sources including vehicle and industrial emissions, and Pb paint. The presence of the anthropogenic factor in the recent data and its absence from the NURE data is explained by the greater density of recent soil samples collected within the city of Sacramento where contamination is present. Although the contamination is not extreme, the spatial and statistical analysis of lead samples from urban Sacramento soils serves to inform Sacramento residents and decisions makers of the causes and locations of lead contamination in Sacramento. This valuable information can be used to prevent chronic lead exposure, which can have devastating effects, especially on young children.