Size-Differentiated Chemical Composition of Re-Suspended Soil Dust from the Desert Southwest United States

ABSTRACT

As part of the Desert Southwest Coarse Particulate Matter Study which characterized the composition of fine and coarse particulate matter in Pinal County, AZ during 2010–2011, several source samples were collected from several different soil types to assist in source apportionment analysis of the study results. Soil types included native desert soils, agricultural soils (crop farming), dirt-road material adjacent to agricultural areas, paved road dusts, dirt road material from within and adjacent to a cattle feedlot, and material from an active cattle feedlot. Following laboratory resuspension of the soil, size-segregated PM_2.5 and PM₁₀ fractions for each source type were collected on filters and characterized for mass, ions, OC, EC, and trace elements. While there are unique chemical compositions of soils in the region (e.g., high As and Sb) that reiterate the importance of using local source profiles (e.g., native soils) as compared to Upper Continental Crust or soil profiles from other regions in receptor modeling studies. The study also provides new insights into the impact of land-use modification on source emission profiles. Specifically, high OC and PO₄^3– are found in material representative of local cattle feedlot activities while elevated Cu, Sb and Zn are found from sources impacted by motor vehicle traffic. Results of the study indicate that the local native soil composition is only slightly modified by agricultural activities and this study provides the chemical composition of both native and agricultural soil for source apportionment studies in the Desert Southwest.