Evaluation of potentially toxic metals load and risk assessment in sediments from coastal areas of Lagos State

Abstract

Trace metal pollution is of global concern due to its adverse effects on human health. Sediments in water bodies are a repository of pollutants, including trace metals, and since they are non-biodegradable, they have negative impact on the ecosystems. Trace metals are due to both anthropogenic and natural sources. Sediments are monitors of trace metal pollution. The study, therefore, aims at assessing the trace heavy metals (THM) in the surface sediments of coastal areas in Lagos State. Forty (40) sediments samples (top and sub-sediment soil) were collected from five coastal communities: Langbasa, Itumaro, Ibeshe, Epe and Badagry, analyzed for pH and trace metals using Atomic Absorption Spectrometry (AAS). Ecological tools: pollution classification, pollution index, and geo accumulation index were further used along with application of sediments quality guidelines to reveal trends and variations in sediment investigated. The pH values range from 4.7- 6.4, while the trace metals concentration ranges from 1.6 - 6.42, 36.2 - 104.5, 0.05 - 63.6, 0.00 - 0.17, 32.1 - 266.3, 3.7 - 5.94, 0.00 - 0.00 mg/kg for Zn, Fe, Cu, Pb, Ca, Mg and Ni respectively. The order of concentration of the metals was Ca > Fe > mg > Cu > Zn > Pb. The monomial and overall ecological potential risks for the trace potentially toxic metals investigated (lead, iron, zinc and copper) in the study area posed low potential risk (<40) and (< 110) respectively. The order of deteriorations (potential risk) in the study area is Badagry > Ibeshe > Epe > Itumaro > Langbasa. Continuous monitoring of trace heavy metals is important to ensure health safety and sustainable environment.