Intercomparison of PIXE and ICP‐AES Analyses of Aeolian Dust from Owens (Dry) Lake, California

Abstract

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.

Laboratory Studies of the Cloud Droplet Activation Properties and Corresponding Chemistry of Saline Playa Dust

“…In contrast to the "low hygroscopicity" samples, aerosols generated from the Owens Lake Crust sample produced several ion peaks consistent with soluble sodium carbonates, sodium chloride (halite), and sodium sulfates. These ion peaks include 62 Na 2 O + , which is likely due to the fragmentation of Na 2 CO 3 forming 62 Na 2 O + and CO 2 (g), similar to the ions observed for calcite, and further supported by the observation of 129 Na 3 CO 3 + in this sample. The saline-rich, erodible soil from Owens (dry) Lake, especially when collected from the surface containing efflorescent salts, has been found to contain several minerals rich in sodium carbonates, including natron (Na 2 CO 3 •10H 2 O), thermonatrite (Na 2 CO 3 •H 2 O), and trona (Na 3 HCO 3 CO 3 • 2H 2 O).…”

“…consistent with previous results that indicated that this sample contained a mixture of surface salts and the underlying aluminosilicate material. 62,63 Further, this sample lacked ion peaks indicative of sodium sulfates and halite, and had low intensity peaks associated with sodium carbonates consistent with this sample representing a cement-like crust rather than an erodible, saline-rich crust. Overall, the Owens Lake Crust sample generated several ion peaks indicative of highly hygroscopic material (e.g., Na 2 SO 4 , κ ∼ 1.04; NaCl, κ ∼ 1.4; Na 2 CO 3 , κ ∼ 1.29 31,47 ), which explains the order of magnitude difference in κ between the two different samples from Owens (dry) Lake, as well as the high hygroscopicity of the Owens Lake Crust sample in comparison to the other playa samples.…”

“…Several sulfate ion peaks present in the Owens Lake Crust sample were associated with sodium (e.g., 119 NaSO 4 − , 165 Na 3 SO 4 + ), likely due to the presence of thenardite (Na 2 SO 4 ) and mirabilite (Na 2 SO 4 • 10H 2 O), which are present when the surface of Owens (dry) Lake is covered with an erodible, efflorescent evaporite salt crust. 32,33,51,62,63 Notably, the Owens Lake Dust sample contained 23 Na + , 27 Al + , and silicate peaks ( 60 SiO 2 − , 76 SiO 3 − , etc.) consistent with previous results that indicated that this sample contained a mixture of surface salts and the underlying aluminosilicate material.…”

ClNO2 Production from N2O5 Uptake on Saline Playa Dusts: New Insights into Potential Inland Sources of ClNO2

“…The “sediment” sample represents a mixture of materials derived from both the evaporite surface and the salt-silt-clay crust directly underneath, including highly hygroscopic sodium carbonates and sodium sulfates that best explain our high values of γ N2O5 and φ ClNO2 . In contrast, the “crust” sample was a hard, white material composed of pure salts that do not fully deliquesce at the humidities used in this work. − ,,, These results underscore the heterogeneity of mineral content not only across playas but also within the same playa …”

“…In contrast, the "crust" sample was a hard, white material composed of pure salts that do not fully deliquesce at the humidities used in this work. [50][51][52]74,104,105 These results underscore the heterogeneity of mineral content not only across playas but also within the same playa. 106 In contrast to the Salton Sea and the Owens Lake "crust" samples that show increasing values of both γ N2O5 and φ ClNO2 with RH, dust generated from the Black Rock Desert showed increasing yields of ClNO 2 (0.3−0.6) but a decrease in N 2 O 5 reactivity (0.07−0.02) with increasing RH.…”