GeoEnvironmental Implications of Heavy Metals Distribution in Parts of Lagos Lagoon, Southern Nigeria.

Abstract

The study investigated the level of heavy metals in surface waters and sediments in the Lagos Lagoon, Lagos State. Water and sediment samples were collected in sterile plastic containers respectively from 8 sampling locations inclusive of a control. The samples were treated and digested and analyzed using the Atomic Absorption Spectrophotometer (AAS). The t-test, single factor ANOVA, post-hoc means plot and Principal Components Analysis (PCA) were used to analyze data. Cu, Zn, Cd, Mn, Ni,Cr and Fe varied as follows: 1.97-5.60(3.07) mg/L in water columns and 9.9-527.35 ppm in sediments,1.58 – 6.99(3.03 )mg/L in water columns and 37.69 – 875.64 ppm, 0.18–0.93 (0.62)mg/L and 0.37–11.46 ppm, 4.48–11.28 (8.51) mg/L and 184.95–547.45ppm, 9.83-20.50 (14.54)mg/L and 46.30–551.00ppm, 4.93–44.70 (23.39) mg/L and 105.17-227.77ppm and 31.60–86.17 (1.08) mg/L and 454.27-768.23ppm respectively. The pH, electrical conductivity, water temperature, salinity, total dissolved solids and dissolved oxygen varied as follows:7.85- 8.39 (8.05), 15.60-28.20 (21.89μS/cm) and 28.00-30.00(29.130C),8.10-14.50 (11.280/00),9.36 – 16.92 (13.49mg/L) and 4.40 – 7.00 (5.78mg/L) in water samples respectively. The results were compared with WHO and NESRA standards and were found to be above the limits. Results indicate lithological origin for the heavy metal presence and possible transportation of heavy metal species from the industries and domestic wastes and deposition in sediments of the proximal Lagos Lagoon.