Geochemistry of oxidic soils developed from different parent rocks in the Limpopo Province, South Africa

Abstract

The study assessed the geochemical characteristics of oxidic soils developed from different parent rocks in the Limpopo Province, South Africa. The main aim of the study was to assess the overall soil quality in the study area. Soils and fresh rock samples were collected from four different parent rocks (basalt, granite, gneiss and arkosic sandstone) in Limpopo Province for geochemical analyses using X-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analytical methods. The geochemical compositions of the soils showed relative enrichment of Fe2O3, TiO2, CaO, K2O, MgO, MnO, and Na2O (except for CaO, K2O, MgO, MnO, and Na2O in soils developed from basalt). The chemical index alteration (CIA) values varied between 55 and ≈100, which suggest a low to very high degree of chemical weathering. The Al2O3 – (CaO* + Na2O) – K2O (A-CN-K) and Al2O3 – (CaO* + Na2O + K2O) – (FeO + MgO) (A-CNK-FM) diagrams for the different soils also support these observations. Trace elements were significantly enriched in soils developed from basalts and gneisses, but were minimally enriched in soils developed from granites and arkosic sandstones based on their enrichment factors. The ecological risk assessment of the soils based on risk index (RI) indicated a low risk in decreasing order of soils developed from basalt > gneiss > arkosic sandstone > granite, respectively.