Evaluation of the Pollution Status of Lagos Coastal Waters and Sediments, using Physicochemical Characteristics, Contamination Factor, Nemerow Pollution Index, Ecological Risk and Potential Ecological Risk Index

Abstract

The heavy metals and physicochemical properties of Lagos coastal waters and sediments, Southwestern Nigeria were investigated in 5 stations (station 1-5), to determine their levels, distributions and pollution index. The observed ranges of physicochemical characteristics from the study area are: dissolved oxygen (DO): 2.15-11.3 mg/L; pH: 6-7.7; temperature (Temp): 28.05-29.25°C; biochemical oxygen demand (BOD): 1.6-110.1 mg/L; electrical conductivity (EC): 1.8-29.8 mS/cm; salinity (SAL): 0.02-2.05ppt; total dissolved solids (TDS): 211.8-1210.2 mg/L and total suspended solids (TSS): 12.13-117.95 mg/L. The analyzed physicochemical properties from all the stations are within the desired values for healthy marine ecosystems when compared with Federal ministry of environment (FMENV) Nigeria and World Health organization permissible limits (DO:>5 mg/L; pH:6.5-9; TEMP:<40°C; BOD: 50 mg/L; EC:900 mS/cm; TDS:1000mg/L and TSS:600 mg/L), with the exception of low DO at station 1 and station 5; and high BOD at; station 2 and station 3 respectively. The concentrations of heavy metals present in the water samples followed the sequence: Fe > Pb > Cu > Cr > Zn > Cd, and showed high values for Pb, Cd and Cr, relative to the standard permissible limits according to FMENV (Pb 0.001; Zn 50 mg/L; Cd < 0.0018; Cu 2-4 mg/L and Cr 0.02-2.0 mg/L). The calculated contamination factor (CF) in the sediment samples showed low-moderate contamination for the analyzed heavy metals (Cr, Zn, Cu and Pb), except for cadmium (Cd) that showed extremely severe contamination (CF > 6) values across the sampling stations. The calculated Nemerow pollution index (NPI) and ecological risk index (RI) showed heavily polluted (NPI > 10) values and very high ecological risk (RI > 380) values at Apapa (location 1), Iddo (location 2) and Makoko (location 3). The potential ecological risk factor (Eir) confirmed Cd as the highest polluted heavy metals (Eir >320), with the greatest potential threat to the marine ecosystems in the Lagos coastal waters. The study highlights the impacts of anthropogenic pollutions on the coastal ecosystems and human health.

Assessment of water quality and heavy metal contamination in ballast water: Implications for marine ecosystems and human health

“…Thus, the introduction of non-indigenous species through ballast water can lead to competition with native species, the decline or extinction of indigenous species, and disruption of the ecosystem (Hess-Erga et al, 2019). The conditions of the Lagos Coastal Waters reveals low dissolved oxygen and high biochemical oxygen demand at certain stations (Ajani et al, 2021). Nkwoji et al (2020) revealed in their study of the coastal Lagos Lagoon that the inflow of pollutants from land-based sources resulted in degraded water quality, and low diversity and abundance of benthic macroinvertebrates.…”

Impacts of the Residual Trace Metals of Aquaculture in Net Cages on the Quality of Sediment

“…Studies have demonstrated the occurrence of the contamination of sediments by trace metals caused by human activities, urbanization and industrialization [ 43 , 57 , 58 , 59 , 60 ]; agriculture [ 61 , 62 ]; and mining [ 63 , 64 , 65 ].…”

Evaluation of Water Quality of Collected Rainwater in the Northeastern Loess Plateau

“…Singh et al [8] used principal component analysis to evaluate the water quality of lakes for pH, conductivity, Ca 2+ , K + , Na + , Cl − , NO 3 − , SO 4 2− , CO 3 2− and other ions, with good results. Ajani et al [9] used the Nemerow pollution index to evaluate the integrated pollution status of sediments in the water zone. Principal component analysis (PCA) can avoid subjective arbitrariness and objectively determine the weights of each index for quantitative studies.…”