X-ray photoelectron spectroscopy investigations of the chemistries of soils

The present study continues our x-ray photoelectron spectroscopy (XPS) or e lectron spectroscopy for chemical analysis investigations of silicate syste ms, particularly those in contact with biological materials. In the present case, the investigations are extended to a detailed analysis for a wide va riety of soil samples extracted from different locations around the world. The samples were selected from relatively pristine sites, pressed into wafe rs, and were examined without further modification. All of the materials we re insulators and therefore analysis required extensive use of the electron flood gun. Careful XPS chemical shift assignments have been achieved for m any silicate minerals. These have been exploited in the present study along with the detailed XPS analysis of organofunctional groups rendered by Beam son and Briggs. As a result, a fairly detailed simultaneous nondestructive description is provided of the surface of both the humus and silt component s of these soil samples. Substantial variations in the composition are demo nstrated and questions are raised about our classifications of fertility. ( C) 1999 American Vacuum Society. [S0734-2101(99)23504-X].