Charge properties and fingerprints of some urban and peri-urban garden soils in Accra, Ghana

Abstract

Urban soils are exposed to many pressures such as Urban and peri-urban gardening (UPG) that lead to environmental pollution. This study assessed charge properties of selected UPG soils in Accra, Ghana. Basic soil properties were measured using standard laboratory methods. Afterward, pH0 and charge fingerprints were measured in Whole soils (untreated soils) and Stripped soils (soils stripped of their native soil organic matter (SOM)) using the Gillman potentiometric titration method using CaCl2 and NH4NO3. The G soils were dominantly Acrisols with ferric properties except for two Vertisols. The soil properties were characteristic of the soil types with pH ranging from 5.5–7.6 and exchangeable acidity < 1 cmolc/kg, yielding CEC > ECEC values of 6.7–27.8 cmolc/kg. In both the Whole and Stripped soils, the δpH and the difference between the pH0 of the Whole (5.3–6.6) and the Stripped (5.6–6.9) soils and the Gillman field pH (pH(0.002)) showed that soils were negatively charged. The pH0 of the Whole and Stripped soils highlighted the importance of SOM in the charge properties, particularly in basic CEC. The charge properties depict the ability of soils to retain charged substances and ions introduced thereby restricting their mobility.