Preliminary assessment of heavy metal distribution in the soils of the university of cape coast nature reserve, Ghana

Abstract

Soil habitats are complex and heterogeneous, resulting in the formation of habitats that can support high microorganism abundance and diversity. A characteristic feature of soil habitats is their wide range of steep physicochemical gradients (e.g., of substrate concentrations, redox potential, pH, available water), which depend upon the size of the soil aggregate. Heavy metal contamination of soils could potentially counteract this steep gradient. The aim of the study was to determine the levels and distribution of heavy metals in the topsoil and subsoil of the University of Cape Coast Nature Reserve and also to assess the extent of anthropogenic impact using three indices-contamination factor (CF), geo-accumulation index (Igeo) and metal pollution index (MPI). The results indicate a wide variability in heavy metal concentrations. The concentrations of Pb, Zn, Fe, As and Cu in the top soil in mg/kg are as follows: 16.1 ± 12.42; 16.6± 1.21; 4650 ± 433.49; 17.9 ± 1.03; and 68.8± 1.37 respectively. The concentrations of Pb, Zn, Fe, As and Cu in the sub soil in mg/kg are as follows: 5.29 ± 0.59; 17.6 ± 1.80; 6780 ± 481.30; 6780 ± 481.30; and 10.3± 1.63 respectively. In the top soil, the order of magnitude of heavy metal concentration is as follows: As >Cu>Fe>Zn>Pb whereas in the subsoil the order is as follows: As > Fe > Cu >Zn>Pb. Heavy metal concentrations were found to be dependent on soil pH. The topsoil and subsoil are practically uncontaminated by Pb (Igeo = -0.76 and -1.88 respectively). Again, they are uncontaminated to moderately contaminated by Zn (Igeo=0.14 and 0.2 respectively). Also, the topsoil and subsoil are moderately contaminated by Fe (Igeo=1.13 and 1.5 respectively). Both the topsoil and subsoil are heavily contaminated by As (Igeo=3.53 and 3.75 respectively). The topsoil is moderately to heavily contaminated by Cu (Igeo=2.52) unlike the subsoil which is uncontaminated to moderately contaminated by Cu (Igeo=0.62). This study serves as the baseline for future monitoring of heavy metal deposition in the nature reserve