Topsoil Characterization of Hydrocarbon Impacted Areas in Gokana Local Government Area, Rivers State, Nigeria

Abstract This study evaluated the physico-chemical characteristics and the spatial variation in heavy metals and Total Petroleum Hydrocarbons (TPH) concentration in the topsoils across five hydrocarbon impacted communities (Mogho, B-Dere, K-Dere, Bomu, and Bodo) in Gokana. Local Government Area. The experimental research design was deployed as direct field measurement involving collection of soil samples from the impacted sites. The soil samples were collected at (0-15cm) at the respective locations whereas ANOVA and the one sample t-tests were used for data analyses. One-way ANOVA revealed significant spatial differences (p < 0.05) in all heavy metals analyzed. For Pb, the F-statistic was 8.42 (p = 0.000), with Bodo and Bomu showing the highest concentrations (group “a”), while B-Dere had the lowest (group “c”). Similar trends were observed for Cd (F = 5.27, p = 0.002), Cr (F = 7.63, p = 0.000), Ni (F = 6.91, p = 0.001), Cu (F = 9.11, p = 0.000), and Zn (F = 10.34, p = 0.000), indicating site-specific contamination patterns. Post hoc Duncan tests confirmed that Bodo and Bomu consistently recorded the highest contamination levels for most metals. For TPH, concentrations exceeded the DPR target value of 50 mg/kg at all locations, ranging from 60.20 ± 7.21 mg/kg in Mogho to 98.52 ± 34.31 mg/kg in Bomu. One-sample t-tests showed significant differences between site means and the DPR target (p < 0.05). For example, Mogho (t = 10.20, p = 0.000) and B-Dere (t = 11.50, p = 0.002) recorded moderate exceedances (20–23%), whereas K-Dere (t = 32.65, p = 0.000), Bodo (t = 34.50, p = 0.000), and Bomu (t = 48.52, p = 0.001) exhibited much higher levels (65–97% above the target). The result revealed spatial heterogeneity in hydrocarbon distribution and the elevated levels present long-term ecological risks, which include soil fertility decline and potential bioaccumulation in food crops. Consequent upon the findings, remediation, compliance monitoring, and sustainable oil spill management strategies in the study area were recommended.