Organic carbon at soil particle surfaces—evidence from x‐ray photoelectron spectroscopy and surface abrasion

Abstract

This study aimed at investigating the potential of x‐ray photoelectron spectroscopy (XPS) for investigating soil organic matter at secondary soil particles. The XPS was applied to microaggregates of the A horizon of a Typic Haplustoll (<20‐μm equivalent diameter, >53‐μm maximum real diameter) and to the fine‐earth fraction (<2 mm) of the Bs horizon of a Typic Haplorthod. Carbon and N, as well as Si (both samples), Ca (Haplustoll), and Al (Haplorthod) were detected. Removing the particle surface layer (<50 nm) by bombarding with Ar+ resulted in a strong reduction of the signals of C and N, while those attributed to inorganic components increased relatively. Consequently, in both soils, organic matter was concentrated at the surface of soil aggregates. We conclude that Ar+ sputtering followed by XPS analysis is a useful tool in identifying the accumulation of elements at the surfaces of soil particles.