Environmental geochemical signature of shale in pollution assessment of trace metals in soil and water in parts of southern Benue Trough, southeastern Nigeria

T.N. Nganje*, C.I. Adamu, A.S. Ekwere, K.A. Ibe, Aniekan Edet, Andrew Hursthouse

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Black shales have a great environmental geochemical significance and act as a source of metal enrichment which upon weathering could release trace elements into soil system where they are in turn mobilized and release into surface water and groundwater systems. An investigation of environmental geochemistry of rock, soil and water in parts of Abakaliki, southeastern Benue trough, Nigeria was carried out in order to evaluate the impact of shale bedrock in the soil and water environment. Shale rock, soil and water samples were collected from ten (10) locations within the study area and were analyzed for major and trace elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In situ parameters such as pH, in water was measured in the field. The results shows that Pb is highly enriched while As. Cr, Co, Fe, Ni, Sr, V and Zn are slightly enriched in the shales relative to the global shale average. Similar geochemical trend was observed for surface and subsurface soils. Also, the mean concentration of As, Co. Cu. Mn, Pb and Zn in soils at both depths are higher than the mean concentrations in the shale bedrock in the area of study, implying relative enrichments of these metals in the soils of the study area. In addition, the mean values of Al, Fe, Ti, Cr, Ni, Sr and V in both soil depths are lower than the values recorded in the shale bedrock. Relationship between pH and metal load suggested that the waters are dominantly near neutral to alkaline range suggesting that acidic contaminants do not affect the water quality. The mean concentration of Al, Fe, Mn and Pb in groundwater and surface water was above the regulatory standards indicating contamination of the water. The calculated enrichment factor, anthropogenic inputs, pollution index for soil indicated that the soil are highly contaminated through numerous geogenic and anthropogenic sources with Pb being the most toxic metal with the shale bedrock and the mineral load contained in them as the major contributor of these contaminants.
Original languageEnglish
JournalInternational Journal of Environmental Analytical Chemistry
Early online date1 Apr 2021
DOIs
Publication statusE-pub ahead of print - 1 Apr 2021

Keywords

  • geochemical
  • shale
  • trace metals
  • Benue trough
  • soil and water
  • Abakaliki
  • Nigeria

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