The Effect of Soil Moisture and Texture on Fe Concentration Using Portable X-Ray Fluorescence Spectrometers

摘要

Portable XRF (pXRF) instruments can be used in the field for measurement of soil elemental concentrations. The pXRF measurements in the field, however, are affected by several factors including soil texture, moisture and sample heterogeneity. In thischapter, we investigated the effect of moisture on the Fe concentration of pXRF laboratory and field measurements. In the laboratory study, soil samples were analysed that were wetted to different moisture contents. In the field study, pXRF measurementswere made from topsoil samples and the data were compared to samples that were air-dried and ground to pass a 2-mm sieve. Soil moisture mainly dampens the X-ray intensity resulting in lower Fe concentrations, and this effect is more pronounced for clayeysoils (higher Fe content) as compared to sandy soils (lower Fe content). In addition, the field moisture content is highly related to clay and Fe content. Thus, the response of XRF intensity to soil moisture content depends on soil texture and mineralogy. We could not find a general correction factor for soil moisture and X-ray intensity but the relationship between air-dried and field-moist Fe concentration is highly linear which allows to correct for moisture content by establishing an empirical correction function.