An application of a modified microwave total dissolution technique for soils

Abstract

Application of a microwave dissolution technique to soil materials aided by acid digestion procedures has many advantages, but the incomplete dissolution of sandy soils has been noted. The objectives of this study were to modify a microwave oven digestion technique to facilitate the determination of the total elemental content of soils and geologic materials containing greater than 45% sand and apply these data to determine natural separations in parent materials. A microwave dissolution technique using aqua regia (HNO₃ and HCl) and hydrofluoric acid (HF) was modified such that the HF is added to the solid 16 hours prior to aqua‐regia addition and subsequent microwave heating. Elemental recoveries were validated using a NBS coal fly ash standard. This procedure was applied to soil core samples representing a wide range of geological and pedological weathering sequences and soil textural classes. Separations in the parent material were determined by observing natural breaks in the elemental concentrations and comparing them to soil morphology data.