Identifying natural and anthropogenic sources of metals in urban and rural soils using GIS-based data, PCA, and spatial interpolation Harley T. Davis a , C. Marjorie Aelion a,d,* , Suzanne McDermott b , and Andrew B. Lawson c,1 a University of South Carolina, Department of Environmental Health Sciences, 921 Assembly Street, Columbia, SC 29208, USA b Department of Family and Preventive Medicine, 3209 Colonial Drive, Columbia, SC 29208, USA c Department of Epidemiology and Biostatistics, 800 Sumter Street, Columbia, SC 29208, USA d University of Massachusetts, Department of Public Health, 715 No. Pleasant Street, Amherst, MA 01003 Abstract Determining sources of neurotoxic metals in rural and urban soils is important for mitigating human exposure. Surface soil from four areas with significant clusters of mental retardation and developmental delay (MR/DD) in children, and one control site were analyzed for nine metals and characterized by soil type, climate, ecological region, land use and industrial facilities using readily- available GIS-based data. Kriging, principal component analysis (PCA) and cluster analysis (CA) were used to identify commonalities of metal distribution. Three MR/DD areas (one rural and two urban) had similar soil types and significantly higher soil metal concentrations. PCA and CA results suggested that Ba, Be and Mn were consistently from natural sources; Pb and Hg from anthropogenic sources; and As, Cr, Cu, and Ni from both sources. Arsenic had low commonality estimates, was highly associated with a third PCA factor, and had a complex distribution, complicating mitigation strategies to minimize concentrations and exposures. Keywords Principal component analysis; cluster analysis; rural and urban soils; GIS databases; neurotoxic metals; mental retardation and developmental delay 1. Introduction Soils contaminated with toxic metals from point sources are potential exposure routes for surrounding populations (Carrizales et al., 2006; Hinwood et al., 2004; Pruvot et al., 2006). Surface soils are a relevant exposure route for a variety of metals (Caussy et al., 2003) such as arsenic (As) (Calderón et al., 2001; Díaz-Barriga et al., 1993), chromium (Cr) (Duckett, 1986), lead (Pb) (Calderón et al., 2001; Factor-Litvak et al., 1999), and mercury (Hg) (Debes *Corresponding Author: (413) 545-2526 (phone); (413) 545-0501 (fax); E-mail: maelion@schoolph.umass.edu. 1 Present address: Medical University of South Carolina, Department of Biostatistics, Bioinformatics, and Epidemiology, 135 Canon Street, Charleston, SC 29425, USA Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author Manuscript Environ Pollut. Author manuscript; available in PMC 2010 August 1. Published in final edited form as: Environ Pollut. 2009 ; 157(8-9): 2378–2385. doi:10.1016/j.envpol.2009.03.021. NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript