Lead (Pb) Accumulation in Water, Sediment and Distribution of Macro-Invertebrates in Delimi River, Jos, Nigeria

Background: This study assessed the concentrations of lead (Pb) in the water column and sediment as well as macro-invertebrates in River Delimi with a view to determining its ability to support aquatic life.

Methodology: Water and sediment samples were collected simultaneously between August and November 2019 at designated stations: A (Abattoir), B (British America bridge), and C (Farin Gada bridge). Composite method was employed to collect water samples from different points in each station in 250 ml capacity plastic bottles with screw caps. The plastic bottles had previously washed with detergent and finally rinsed using distilled water. The water samples were filtered using 0.4 mm Whatman filter paper. Samples were then digested with few drops of concentrated nitric acid (HNO3). Sediment samples were collected in decontaminated airtight polythene bags measuring 500_g each. Sub-samples of the material were sun-dried for three (3) days and homogenized by grinding in laboratory mortar and pestle and sieved (aperture 125 µm). Sediment samples were digested with 20 cm3 aqua regia (3HCl:1HNO3), filtrate were stored in glass bottles and transported to the laboratory for chemical analyses. Macroinvertebrates were collected using a D-frame kick-net (30) at each site over a three-minute period. The collected specimens were preserved in 70% formalin and transported to the laboratory for sorting, identification, and enumeration.

Result: Showed that the concentration of lead (Pb) in all the water samples were found to be less than the permissible limit set by WHO/FAO except site WA3 (0.0874ppm) and WC3 (0.0678 ppm) which were higher than the permissible limit. The concentration of lead (Pb) in sediment was higher than the WHO/FAO permissible limit in all sampling stations which is most likely to pose serious health risks to macrobenthos. Also, 7 Micro-invertebrate taxa were identified in the sampling stations. Chironomidae, Eristalis Larva (Syrphidae), Tabanidae and Whirligig beetle (Gyrinidae) comprised more than 79% of the total abundance while stone fly Larva, hydrophilidae and beetle larva constituted the remaining.

Conclusion: water samples suggest potential environmental contamination of lead in some locations while sediment samples indicate a significant contamination with lead, posing potential health risks to organisms living in the sediment, including macrobenthos.