METHODS OF INVESTIGATION OF STREAM SEDIMENTS FROM RIVER (Pb, Zn, Cu, Cd, As and Ni)

Field Method of Investigation

            The field work was done in four (4) stages

(1) Desk Studies: This involves all the preliminary work in the libraries and various offices to consult the available literatures on the study area and related sections.

(2) Reconnaissance Survey: In this stage, preliminary survey was done to identify with the natives of the study area. Geologic spots were noted and also feasibility of the designed geologic study.

(3) Detailed Mapping: In this stage, outcrops, exposures along mines, quarries, erosional and stream channels as well as altitude of bedding plane, joint, vein and inclined bedding were made. Pictures from different location visited were noted. Fresh samples were also taken on this course.

(4) Bed Sediment Sampling: This involves the collection of 20 samples from stream sediments which was later prepared and sent for geochemical analyses. The collection of these 20 samples was done at the interval of 500mtrs with the aid of GPS. This collection was aided by the use of shovel. GPS was used for the location of longitude and latitude at which the samples were taken.

Laboratory Methods/Sample Preparation

            The Laboratory methods includes the preparation of the twenty samples for analysis of the following Elements: Lead (Pb), Zinc (Zn), Copper (Cu), Arsenic (As), Cadmium (Cd) and Nickel (Ni). The sample preparation takes the following steps.

1). Drying: The fresh samples were collected during the dry season. Thus, it was dried in the laboratory for some days.

2). Homogenisation: The samples were homogenized with the used of agate mortar and pestle.

3). Sieving: After the homogenization, the samples were sieved to obtain 100 mesh fraction by the use of polyethylene sieve.

4). Digestion: The samples were digested with the use of aqua regia. The choice of this mixture is to its advantage of being kept at high temperature than other acids (Levinsion, 1974), with its decomposition faster than most other techniques.      

            In the digestion proper, 1g of screened samples were weighed out and placed in 20ml beaker. 10ml of aqua regia was added and stirred. This was gently heated on hot plate to a volume of 2.5ml. After that, 10ml of de-ionized water was added and gently heated to the volume of 5ml. This was sieved adding de-ionized water to make up for 25ml. Thus, the analytical procedures.

Analytical Procedure

            The digested sample was analyzed for Cu, Pb, Zn, Cd, As and Ni by the Atomic Absorption Spectrophotometric method, using Buck Scientific Atomic Absorption Spectrophotometer 210VGP. The outline of this model basically consists of the light sources which are made up of hallow cathode lamp that emits radiation at the resonance wavelength of each element to be analyzed.