Size-Specific Characterization of Sands and Dust Collected from Iraq and Northern Kuwait: Factors Influencing Bacterial Species Composition and Trace Element Bioavailability

In arid environments, winds, storms, and other physical disturbances can suspend surficial sands, silts, and clays as airborne dust that can be subsequently transported over distances from meters to hundreds of kilometers. This dust, particularly the silt/clay fraction, carries with it any organisms and inorganic or organic constituents that are associated with particle surfaces. In the summer of 2007, surface sand samples were collected from sites in Northern Kuwait and Iraq. Bacterial species richness and diversity on the readily- suspendible silt/clay fraction of these samples was quantified using length heterogeneity polymerase chain reaction (LH-PCR) on DNA extracts. The silt/clay fraction was also characterized geochemically and mineralogically using Energy-Dispersive X-ray Fluorescence (ED-XRF) and X-ray Diffraction (XRD). Lastly a series of sequential extractions were conducted and analyzed by High Resolution Inductively Coupled Mass Spectrometry (HR-ICP-MS) to investigate the potential bioavailability of select trace elements (Cr, V, Cu, Zn, Pb) associated with the silt-clay fraction. Results suggest linkages between the geochemistry and mineralogy of the readily-suspendible silt/clay fraction and bioavailable trace element loading of Northern Kuwait and Iraq sands. Additionally, geochemistry and mineralogy may play an important role in determining bacterial species richness and diversity on surficial sands and airborne dust in Northern Kuwait, Iraq, and other arid regions.