Major, minor, and trace element concentrations were determined by particle-induced x-ray emission (PIXE) in 118 aeolian sediment samples collected at six heights in seven locations along a 1.2 km transect during three sequential dust storms at Owens (dry) Lake, California, USA. Na and S concentrations covaried with each other (and inversely with Si and Ca), increased with height, and decreased with distance downwind and time. Mg, Al, Si, K, Mn, Fe, and Sr concentrations at northerly sites varied with height and location as opposed to nearly constant concentrations at southerly locations. Volumetric particle-size distribution (PSD) for each sample was determined via laser diffraction. PSDs of the collected sediment reflected a trimodal distribution:63% of samples peaked at 20-50 µm (silt), 11% at 50-100 µm (very fine sand) and 26% at 100-250 µm (fine sand). Most silty samples occurred during the first two events. Significant differences in element concentrations existed in relation to the PSDs. Na and S concentrations were proportional to the submicron to silt particle fraction during each event. Al, Ti, Mn, K, Fe, and Rb concentrations correlated with 100-500 µm (fine/medium sand) particles in the first two events and a wider PSD range 250-1000 µm (coarse sand) in the third event. The results suggest sodium sulfate aerosol emission during the first windstorm, while subsequent saltation-dominated events released more aluminosilicate minerals containing higher trace metal concentrations. These combined techniques reveal particle size/chemical fractionation and spatial variability of sediment properties during resuspension at aeolian 'hotspots,' with implications to geochemical cycling and aerosol source/receptor relationships.
Particle-induced X-ray emission (PIXE) and ICP-AES can be combined to obtain a wider range of detected elements, augment previous data and ⁄ or to verify measured concentrations of heavy and trace metals in geological samples. Intercomparison of data sets generated by multiple techniques is challenging due to the differing processes and methods of each technique. Here, we compare elemental data obtained by both techniques for aeolian dust from Owens (Dry) Lake, California. Nineteen elements were detected by PIXE, sixteen by ICP-AES and ten elements were detected by both techniques. Statistical analyses of data set groupings illustrated which parameters differed significantly between PIXE and ICP-AES. Relative variation (%) showed that PIXE gave higher concentrations than ICP-AES for Al, As, Cu, Fe, K, Mn, Ni, Sr, Ti and Zn in all samples. For As, Cu, Sr and Zn, relative variation was variable between the techniques. PIXE detection limits exceeded ICP-AES concentrations for Ba, Cd, Co, Cr, Pb and Mo. Low ICP-AES percentage recoveries of Al, Fe, K, Mn and Ti for NIST SRM 2710 indicated incomplete dissolution during digestion (EPA Method 3050B), since elements were bound in silicate structures. Variability between the two data sets is explained by differences between analytical techniques, sample preparation methods and ⁄ or variability in sample matrices.
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