GEOCHEMISTRY AND ECOLOGICAL RISK ASSESSMENT OF SEDIMENTS IN THE ESTUARY MANGROVE FORESTS OF GBARAMATU KINGDOM OF NIGER DELTA, NIGERIA

Abstract

ABSTRACT Mangrove sediments serve as natural sinks for metals from both natural and human-impacted watersheds. This study investigated the geochemical composition and environmental status of sediments in the Gbaramatu Kingdom, Niger Delta, through a comparative analysis of the Oporoza, Okerenkoko, Kurutie, and Kunuma stations. The research employed multivariate geostatistical techniques, including correlation matrices and hierarchical cluster analysis, to distinguish between natural lithogenic signatures and anthropogenic impacts. Geochemical results revealed that Oporoza sediments were primarily silica rich (SiO₂: 31.85–49.84 mg/kg), whereas the Okerenkoko, Kurutie, and Kunuma (OKK) stations were dominated by iron oxides (Fe₂O₃: 48.41–538.85 mg/kg) and higher sodium levels. Heavy metal concentrations across all sites remained well within WHO permissible limits, suggesting negligible toxic metal enrichment at the time of the study. However, organic geochemical analysis highlighted significant environmental stressors: mean Total Petroleum Hydrocarbon (TPH) and Total Hydrocarbon Content (THC) at the OKK stations (276.12 mg/kg and 331.29 mg/kg respectively) substantially exceeded DPR target value of 50 mg/kg, while Oporoza remained largely within regulatory thresholds. Multivariate analysis identified a dominant lithogenic factor governing major oxides, but revealed distinct hydrocarbon fingerprints. At Oporoza, TPH was specifically associated with vanadium (r = 0.927), an indicator of petroleum derived input. Conversely, at the OKK stations, TPH showed near perfect correlations with aluminum and iron oxides (r > 0.94), indicating a more uniform integration of hydrocarbons into the fine grained mineral matrix. Dendrogram analysis confirmed these patterns, showing isolated hydrocarbon clusters at Oporoza compared to more integrated clusters at the OKK stations. These findings demonstrated the efficacy of multivariate geostatistics in identifying localized pollution dynamics and provide a vital baseline for the sustainable management of the Niger Delta mangrove ecosystems. Keywords: Mangrove forest, Heavy metals, Niger Delta, Ecosystem.