Toxic metal concentration and ecological risk assessment in surface water, soil sediment, and atmosphere in two selected creeks in Rivers State

Abstract

Pollution puts the balance of the earth's support systems at risk, and it threatens the existence of the marine ecosystem: air, surface water, and soil sediment. Samples were collected at three points within the creeks of Isaka and Marine Base for toxic metals analysis. Five toxic metals (As, Cd, Hg, Mn, and Pb) were analyzed using Atomic Absorption Spectrophotometer. The analyses of Isaka creek revealed As and Hg to be of the same concentration of 0.002±0.00 mg/l in surface water, and 0.001±0.00mg/kg apiece in both soil sediment and air. Cd was found to be 0.032±0.001mg/l concentration in surface water, 0.064±0.003mg/kg in soil sediment and 0.002±0.00ppm in air. The concentration of Mn was found to be 0.055±0.004mg/l in surface water, 2.406±0.34mg/kg in soil sediment and 0.005±0.00ppm in the air analysis. For Pb, a concentration of 0.232 ±0.10mg/l was found in surface water, 0.704±0.043mg/kg in soil sediment and 0.002±0.00ppm in air. The result of Marine Base creek showed As to be of a concentration. of 0.007±0.00mg/l in surface water, 0.002±0.00mg/kg in soil sediment and 0.001±0.00ppm in the air. The concentrations of Cd were 0.023±0.001mg/l, 0.041±0.001mg/kg, and 0.001±0.00ppm in surface water, soil sediment and air respectively. Hg has mean concentrations of 0.0005±0.00mg/l in surface water, 0.002±0.00mg/kg in soil sediment and 0.0005±0.00ppm in air, while that of Mn was observed to be 0.067±0.001mg/l in surface water, 37.632±0.064mg/kg in soil sediment and 0.011±0.002ppm in the air. Concentration for Pb metal was observed to be 0.166±0.001mg/l in surface water, 1.407±0.188mg/kg in soil sediment and 0.002±0.00ppm in the air. Also, the contamination factor revealed that the water and soil samples from both creeks fell within low contamination factor (CF<1), indicating no pollution. The Ecological Risk Index (Eri) for all the deleterious elements in the surface water and sediments were < 30, indicating trivial effect from ingestion of surface water or dermal source for intake of sediment from both creeks as they pose no ecological threat to human lives. The sum Risk Index (RI = Σ Eni) for all the toxic metals in the surroundings of both creeks is to be tagged slight as the values are very low below 40. However, the particulate matter concentration of the toxic metals As, Cd, and Pb contained in the atmosphere is higher than the acceptable limits of USEPA. There should therefore be control over the sources of these pollutants to prevent ecological problems.