Evaluation of Heavy Metals/Metalloids of High Toxic Response Factors in Sediments of Lekki

Abstract

The unassailable increase in industrial growth and the concomitant urbanization in and around Lekki Free Trade Zone (LFTZ) informed the evaluation of toxic metal by-products in the nearby Lekki Lagoon in southwest Nigeria. The specific objectives were to determine the extent of sediments' degradation using various indices of contamination; unveil potential heavy metals of high toxic coefficients in sediments; and assess the associated human health risks. Horiba U-53 Multiparameter Meter (10-M) Cable was employed to determine water characteristics such as salinity, pH, redox potential and depth.Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) was employed for identification and measurement of the constituents of heavy metals in sediments. The measured concentrations of the various metals were used to compute non-carcinogenic and carcinogenic indices using the United States Environmental Protection Agency risk assessment model. Heavy metals such as Cu, Cd, Hg and As were below threshold effect concentration (TEC) in sediments suggesting there was no probability of negative biological effects. The mean probable effect quotients (mPECQs) varied from 10 % to 17 % possibility of sediments producing toxic effects. Considering indices of contamination such as the contamination factors (CF), enrichment factors, (EF), geoaccumulation index (Igeo), potential contamination index (Cp), toxic risk index (TRI) and integrated ecological risk index (RI), Pb, Cd and Cu posed no threat to the aquatic ecosystem. Meanwhile, Co, Zn, Ni, As and Hg in sediments showed severe to very severe contamination through Cp. Contamination of As was the most widespread, followed by Zn contamination which covered approximately half of the study area, exhibiting moderate to high and moderate to very high contamination respectively. The EF, Pearson correlation, Principal Component (PCA) and Cluster analyses uncloaked both anthropogenic and geogenic pathways of As, Hg, Zn, Ni and Co into the lagoon. The non carcinogenic risks (HI) associated with toxic metals in sediments were within the safe level. However, children's population was more prone to cancer risks than adults through accidental ingestion given the average concentrations of Ni and As in the sediments.

Publication Info:

Author: Phillips, O.A.* and Adebayo, A.J.

Volume: 60

Issue: March

Published By: Journal of Mining and Geology Vol. 60(1) 2024. pp. 1 - 24, 2024-03-01