In this study, sampling was done monthly between March, 2014 and October 2014. Sampling was conducted from 40 sampling points designated along the river course from Idah to Kotonkarfe, within an interval of 2km apart.
Five samples per sampling site were homogenized to form a composite sample. Coordinates of the sampling points were recorded using global positioning system (GPS).
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The Map of Study Area
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The River Niger features two main bridges within the study area. One is at the cross between the Eastern and the Central senatorial district in Kogi State at Itobe while the other is located at Kotonkarfe on the way to FCT. Abuja.
The river serves as source of water for domestic uses, fishery, recreational activities, sand mining and agricultural irrigation programs for more than five million people settled along the river.
Some major portion of the river includes; Idah, Ajaokota, Itobe, Shintaku, Lokoja and Kotonkarfe. The section under study cut across; Idah, OFU, Ajaokuta, Lokoja and Kotonkarfe local government’s areas of Kogi State.
Idah covers total area of 36km2 with the total population of 79,815 (2006 census). While Lokoja covers area of 3180km2 and a population of 195, 261 (2006 census). The major occupation of the people is fishing and irrigation farming, few of them engaged in commercial activities.
The Niger loses itself into the complex delta system in Africa and supplies life to remote villages and town through which it passes. (Figure 2.1)
3.1.2 Water Sampling and Preservation
The sample bottles used were washed with metal free non-ionic detergent solution and finally rinsed several times with distilled water. The pre-cleaned poly- ethene sample bottles were immersed 10cm below the water surface and 0.5liter of water was taken at each sampling location. The surface water samples were collected from the selected locations with a 500ml sterilized polyethylene bottle. The samples from five points per sampling site were homogenized to form a composite sample. Samples were acidified with 10% HNO3, placed in an ice bath and brought to the laboratory. The samples were filtered using whatman No.1 filter paper and stored at 40C in a refrigerator until time for trace metal analysis (Bassey, 2015). The water samples for
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physico-chemical analysis were collected into acid cleaned polyethene bottles packed and transported in ice-box to the laboratory. They were stored in the refrigerator prior to analysis.
The water sample for micro biological analysis was obtained against the water current and stored in well sterilized amber bottles.
3.1.3 Sediment Sampling and Preservation
Grab sediments were collected from the river for 8 months (March 2014 to October 2014). In the study area, five grab samples were collected at each sampling location and were combined together in a stainless steel bowl to form a composite sample. The samples were transported back to the laboratory in a cooler with crushed ice.
In the laboratory the sediment samples were air dried for one week, after drying visible remains of organism and debris were removed. The dried samples were crushed or ground into fine particles using pestle and mortal and sieved through a 2mm sieve (mesh) to remove unground matters and separate the coarse fractions from the fine fractions.
3.1.4 Fish Sampling Preservation and Treatment
Five samples of Tillapia (Oreochromis niloticus) and five samples, of catfish (Clarias gariepinus) each were obtained from three selected sampling sites viz: Idah, Itobe and Lokoja where anthropogenic activities were high. The lengths of the fishes were between 15 and 18 cm and weight, between 50 and 75g. The fish samples were obtained by some fishermen using fishing nets and local traps.
The fish samples were washed with deionized water and collected into pre-cleaned polyethene bags and were immediately transferred into a thermo-insulated flask filled with ice-blocks and taken to the Zoology laboratory of Kogi State University, Anyigba for identification and was
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indentified by Dr. A.A. Akinolu of the department. The fish samples were then immediately preserved in a deep freezer at -180C to avoid deterioration.
The frozen samples were washed with distilled water after removing the scales. The sample was oven dried to a constant weight at 800C in an acid wash petridish. After cooling in a desiccator, the samples were ground using a mortar and pestle to powdery form and sieved through 1mm mesh. The homogenized powdered samples were stored in an air tight pre-cleaned dry plastic bottles for further analysis.
3.1.5 Materials and Equipment Whatman filter paper No.1&42 Electric hotplate
Volumetric flasks
Buck scientific, 210 VGP Atomic Absorption Spectrophotometer.
Jenway P.F7 flame photometer.
Sieve Beakers
Fume cupboard
Hach colourimeter – model Dr 890
Jen way model 470 portable conductivity and total dissolved solid meter.
Pipette S and Bureltes.
Bar magnet and PH electrodes Magnetic stirrer
pH meter
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Water proof wegtech PH scan 3 + double Junction mdel
Thermo Evolution 600 UV/visble spectrophotometer computer based automated model.
Conical flasks.
Shewood scientific limited flane photometer model 410.
250ml Erlen Meyer flask.
3.1.6 Reagents
Analar nitic acid solution 50% HCl solution
De – ionized water
Concentrated HNO3 solotion Hach customised reagents
Sodium trioxocabornate (iv) solution Buffer solutions
K2Cr2O4 solution EDTA
Sodium hydroxide (NaOH) solution Murixide indicator
Calgamite indicator.
All reagents used were of analytical grade and obtained from Franny Chemical company, Ikeja Lagos.
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