Portable X-Ray Fluorescence (pXRF) for Determining Cr and Ni Contents of Serpentine Soils in the Field

摘要

Serpentine-derived soils have high concentrations of Cr and Ni from the parent materials and pose a risk to human health and environmental quality. The use of pXRF is a viable and effective technique for digital soil morphometries. Soil digestion by aqua regia (AR) is a common method for screening heavy metals in contaminated soils. To provide in situ measurements, pXRF was performed for quantifying Cr and Ni in 49 soil horizons from 11 pedons at 3 serpentine areas in eastern Taiwan. Cr and Ni were also determined by the AR method for the samples. The correlation between pXRF and AR methods was linear and significant (r = 0.90 and 0.99, respectively, P < 0.001). The metal contents by pXRF were, however, higher than by AR. The difference is much larger for Cr than for Ni, because Cr was mainly fixed in the chromite minerals which were resistant to the AR reagent, but Ni was easily released from weatherable serpentine silicates. When additional 192 surface soil samples were used, the correlation wassignificant for Cr and Ni (r = 0.89 and 0.98, respectively, P < 0.001, n = 241). It was concluded that the pXRF was valid to rapidly screen Cr and Ni levels in serpentine soils in the field.