A soil geochemical background for northeastern Brazil

Very few area-representative soil geochemical data exist for the southern hemisphere. A sub-continental scale (1.7 × 10⁶ km²) geochemical sampling expedition in northeastern Brazil delivered 101 representative composite soil samples (30–50 cm depth) for non-anthropogenically influenced areas (mainly pasture land). Major, minor, and selected trace elements, determined by WD-XRF, are discussed with respect to lithology, soil type, biome type, climate and land use. These element concentrations vary up to two orders of magnitude, except for Si (factor ≅ 2.6). Silicon is strongly enriched compared to global averages, whereas most other components show a considerable deficiency. Significant deviations occur compared to results obtained from southern Brazil and from Australia – examples for the few representative data from the southern hemisphere. Anthropogenic influences appear negligible. All environmental parameters, except for land use, play an active role in shaping the geochemical composition. Lithology appears to be partly decoupled from the soils due to their age. The soil composition reflects soil type, biome type, and weathering influences. Most plant nutrients, despite their absolute depletion, show the highest values in Caatinga soils, and the lowest in Atlantic Forest soils. The new data form a robust and valuable tool to support future land use management.