Preliminary Investigation of Stream Sediments Contaminations Caused by Mining Activities in Ibodi and Its Environs , S / W Nigeria Using Geological and Geochemical Assessment Approach

Mining and related activities are sources of heavy metal contamination in streams, such as copper, zinc, cadmium, arsenic and lead . The study is focused on Ibodi, southwestern Nigeria which is located in the basement complex of Nigeria and it is to assess the stream sediments of Ibodi in order to decipher the environmental impact assessment of mining activities on the environment. A total of ten stream sediment were collected from the study area and its environs along major tributaries, air dried at room temperature, sieved with 75 micron sized sieve and analyzed in the laboratory using ICP-MS (inductively couple plasma mass spectrometry technique). The analytical results of the major elements analyses show that Iron oxide [Fe2O3] has the highest major element composition, value ranging from 2.36% 10.61% with an average value of 5.262%. This highest concentration of Iron oxide was found in location 1, with a value of 10.61% and this can be attributed to the underlying geology of amphibolites' in the Ibodi study area, which are known to be rich in Iron as well as magnesium i.e ferromagnesian minerals. Magnesium oxide [MgO] range in composition from 0.11% 0.92% with an average value of 0.349%, the highest concentration was found in location 3. [Al2O3] ranges in composition from 0.83% 4.158% with an average value of 2.109% the highest value was also found at location 3, it is the next in abundance to Iron oxide in the Ibodi study area. Potassium oxide [K2O] range in composition from 0.04% 0.65% with an average value of 0.183%, other major oxides such as [P2O5], [TiO2], [Na2O] and [CaO] have average values of 0.109%, 0.096%,0.008% and 0.162% respectively; These values are generally low within the Ibodi study area, The analytical results for trace element geochemistry of Ibodi study area show that Vanadium [V] has a high concentrations and it range from 35.00 ppm 202.00 ppm with an average mean value of 92.50 ppm, the highest concentration of this element was found in location 1 of the Ibodi study area. Arsenic [As] range from 0.10 ppm 1.6 ppm with an average value of 0.644 ppm, there is a significant enrichment of Cobalt [Co] and Chromium [Cr] with concentrations ranging from 4.0 ppm 53.50 ppm and 35.20 ppm -150.70 ppm respectively, with average mean values of 17.73 ppm and 88.78 ppm respectively; Manganese [Mn] has the highest concentration in the study area, with concentration value ranging from 86.00 ppm 2165.00 ppm having an average value of 768.20 ppm; the highest concentration of this element was found in location 1 of the study area. [Ga], [Ni] and [Pb] show considerable enrichments within the study area with concentration values ranging from 3.10 ppm 9.50 ppm, 5.30 ppm 37.70 ppm and 6.75 ppm 18.44 ppm, with average values of 6.08 ppm,19.80 ppm, 12.209 ppm respectively, Rubidium [Rb] range in concentration from 6.50 ppm 30.90 ppm with an average value of 13.41 ppm, Strontium [Sr] has concentration values that range from 4.70 ppm 37.20 ppm with an average value of 15.06 ppm. [Y], [Zr] and [Zn] has concentration values that range from 7.99 ppm 21.10 ppm, 1.20 ppm 4.00 ppm and 26.20 ppm-83.60 ppm respectively with average mean values of 15.065 ppm, 2.21 ppm and 46.58 ppm, the value of zinc [Zn] is considerably high in the study area with the highest value found at location 4 of the study area indicating some level of enrichment of this metals within the study area, also [Rb], [Y] and [Sr] show some considerable enrichments within the study area. from the study of the environmental parameter such as box plot and Geo-accumulation indexes the values of the selected trace elements are all less than 1, meaning that all the selected trace metals in Ibodi study area have values less than zero and are in the negative zone. In order to determine the pollution status of the study area, the values of the elements when compared to the Muller classes of


Methodology of Study
Systematic geological mapping and stream sediment sampling of first order streams in other to represent weathered rocks in the drainage system was carried out, followed by thin section Petrographic studies of fresh whole rock samples was carried out.Ten stream sediments samples were then analyzed for major and trace elements using inductively-coupled plasma atomic emission spectrophotometry (ICP-AES), at ACME Laboratory Vancouver Canada.The geochemical analytical procedure involves addition of 5ml of Perchloric acid (HClO 4 ), Trioxonitrate (V) HN0 3 and 15 ml Hydrofluoric acid (Hf) to 0.5 gm of sample.The solution was stirred properly and allowed to evaporate to dryness after it was warmed at a low temperature for some hours.4ml hydrochloric acid (HCl) was then added to the cooled solution and warmed to dissolve the salts.The solution was cooled; and then diluted to 50 ml with distilled water.The solution is then introduced into the ICP torch as aqueous -aerosol.The emitted light by the ions in the ICP was converted to an electrical signal by a photo multiplier in the spectrometer, the intensity of the electrical signal produced by emitted light from the ions were compared to a standard (a previously measured intensity of a known concentration of the elements) and the concentration then computed.

Geological Setting, Field Description and Petrography
Nigeria is underlain by Precambrian basement complex rocks, younger granites of Jurassic age and Cretaceous to Recent sediments.The basement rocks occupy about half of the land mass of the country, and is a part of the Pan-African mobile belt lying between the West African and Congo cratons (Black, 1980).There are however contrasting documentation of the evolution of the basement rocks.However loosely, the basement is grouped into three major groups lithostratigraphically viz: the Migmatite-Gneiss Quartzite Complex: comprising biotite and biotite hornblende gneisses, quartzites and quartz schist.Schist Belts, comprising paraschists and meta igneous rocks, which include schists, amphibolites, amphibole schists, talcose rocks, epidote rocks, marble and calc-silicate rocks.They are mainly N-S to NNE-SSW trending belts of low grade supracrustal (and minor volcanic) assemblages.Other secondary rocks used in delineating them are carbonates, calc gneiss and banded iron formation (BIF) and Older granites, which include granite, granodiorite, diorite charnockite, pegmatites and aplites.The study area is located within Ibodi, its geology consists of Precambrian rocks that are typical of Basement Complex of Nigeria and these rocks includes the following five lithologies:

Result and Discussion
The analytical results of the major elements are presented in (Tables 1 and 2).Table 1, shows the major elements oxides composition of the Ibodi study area in (Wt %) while Table 2, shows the statistical summary of major elements oxides with their range and average values respectively.From the analytical data and the various statistical plots figure 5, shows the line diagrams of graphical illustration for major elements oxide composition in stream sediments of Ibodi study area.The analyses show that Iron oxide [Fe 2 O 3 ] has the highest major element composition with value ranging from 2.36% -10.61% with an average value of 5.262%.This highest concentration of Iron oxide was found in location 1, with a value of 10.61%.and this can be attributed to the underlying geology of amphibolites' in the Ibodi study area, which are known to be rich in Iron as well as magnesium i.e ferromagnesian minerals.Magnesium oxide [MgO] range in composition from 0.11% -0.92% with an average value of 0.349%, the highest concentration was found in location 3. [Al 2 O 3 ] ranges in composition from 0.83% -4.158% with an average value of 2.109% the highest value was also found at location 3, it is the next in abundance to Iron oxide in the Ibodi study area.Potassium oxide [K 2 O] range in composition from 0.04% -0.65% with an average value of 0.183%, other major oxides such as [P 2 O 5 ], [TiO 2 ], [Na 2 O] and [CaO] have average values of 0.109%, 0.096%,0.008%and 0.162% respectively; These values are generally low within the Ibodi study area, (Figures 3 and 4) Show the 2D, 3D and geochemical maps of [Fe], [Ca], [Mn], [Ti] [Al], [K] and [Na] respectively within the study area.The correlation matrix (Table 3) shows a very strong and positive correlation of Ca-Fe, Mg-P, Ti-Mg, Na-Fe, S-Fe, S-Mg, S-Ti and S-Na with 'r' values of 0.854, 0.878, 0.893, 0.820, 0.942, 0.832, 0.906 and 0.842 respectively; indicating that they are governed by the same geochemical factors and are from the same source.Also, the correlation matrix showed that Ti-Fe, Ti-P, Na-Ca, Na-Ti, K-Ca, K-P, and S-P with 'r'values of 0.697, 0.682, 0.528, 0.637, 0.547, 0.601 and 0.646 respectively, has strong and positive correlation, indicating that they are also governed by the same geochemical factors and they are from the same source, (Figure 6 ) shows the scatter plots for correlation matrix of major elements within the study area.The analytical results for trace element geochemistry of Ibodi study area are presented in (Tables 4 and 5) .Table 4, shows the trace element concentrations of Ibodi study area in (ppm) and Table 5, shows the statistical summary of trace elements with their range and average values respectively.From these tables, Vanadium [V] has a high concentrations and it range from 35.00 ppm -202.00 ppm with an average mean value of 92.50 ppm, the highest concentration of this element was found in location 1 of the Ibodi study area.Arsenic [As] range from 0.10 ppm -1.6 ppm with an average value of 0.644 ppm, there is a significant enrichment of Cobalt [Co] 8a).Manganese [Mn] has the highest concentration in the study area, with concentration value ranging from 86.00 ppm -2165.00ppm having an average value of 768.20 ppm; the highest concentration of this element was found in location 1 of the study area.[Ga], [Ni] and [Pb] show considerable enrichments within the study area with concentration values ranging from 3.10 ppm -9.50 ppm, 5.30 ppm -37.70 ppm and 6.75 ppm -18.44 ppm, with average values of 6.08 ppm,19.80ppm, 12.209 ppm respectively, Figure 8b (Muller, 1969).It is computed using the formula: Igeo=Log2(Cn/1.5*Bn);Where Cn is the measured concentration of the elements.Bn is the normal or average shale content 1.5 is the correcting or matrix factor for geo-accumulation.The Igeo consist of seven grades (Table 6) ranging from practically uncontaminated to extremely contaminated (Muller, 1969).The geo-accumlation values of the selected trace elements in the stream sediment samples of Ibodi study area is shown in (Table 7).From the box plot and Geo-accumulation Table, (Figure 9; Table 7) respectively, the values of the selected trace elements are all less than 1, meaning that all the selected trace metals in Ibodi study area have values less than zero and are in the negative zone.In order to determine the pollution status of the study area, the values of the elements when compared to the Muller classes of geo-accumulation (1969), suggests that the study area is practically uncontaminated with the selected trace metals, the elements fall into the class 0 i.e.Practically unpolluted (Table 6) of Muller (1969).-2.32193 -2.90689 -2.32193 -3.90689 -2.20645 -6.71425 -3.90689 -6.22882 -1.09954 -6.71425 L8 -3.90689 -1.90689 -3.90689 -4.90689 -1.58496 -5.71425 -2.90689 -7.22882 -0.90689 0 L9 -3.90689 -2.32193 -3.90689 -3.90689 -1.44746 -5.71425 -2.32193 -6.81378 -1.09954 -6.71425 L10 -3.90689 -2.90689 -3.90689 -3.90689 -1.44746 -5.12928 -3.90689 -7.81378 -1.58496 0 in the study area.The result of the correlation co-efficient suggests a common source between these elements.It can be inferred from the geo-accumulation index which is an environmental parameter that enables the assessment of contamination by means of comparism that result from the Ibodi study area has proven that values of selected trace elements are all less than 1, meaning that all the trace metals in Ibodi study area have values less than zero and are in the negative zone suggesting that the study area is practically uncontaminated with the selected trace metals with the elements falling into the class of 0 'Practically uncontaminated' according to Muller, 1969.The result has clearly shown the level of uncontamination in the area under investigation.It is therefore suggested that regular geochemical research work should be carried out in this study area to determine future rise in contamination level as a result of mining activities going on in this environment in addition; Mining activities in the area should be controlled to minimize the amount of pollutants released into the streams and water bodies within the study area in other to guide against health hazards caused by high concentrations of some of these metals on both man and animals.

Figure 2 .
Figure 2. Geological map of Ibodi study area and Chromium [Cr] with concentrations ranging from 4.0 ppm -53.50 ppm and 35.20 ppm -150.70 ppm respectively, with average mean values of 17.73 ppm and 88.78 ppm respectively; the 2D and 3D geochemical maps of [V], [As], [Co] and [Cr] are shown in (Figure shows the 2D and 3D geochemical maps of[Ga],[Mn],[Ni]  and[Pb]  within the Ibodi study area.Rubidium[Rb]  range in concentration from 6.50 ppm -30.90 ppm with an average value of 13.41 ppm, Strontium[Sr]  has concentration values that range from 4.70 ppm -37.20 ppm with an average value of 15.06 ppm.[Y], [Zr] and[Zn]  has concentration values that range from 7.99 ppm -21.10 ppm, 1.20 ppm -4.00 ppm and 26.20 ppm-83.60ppm respectively with average mean values of 15.065 ppm, 2.21 ppm and 46.58 ppm, the value of zinc[Zn]  is considerably high in the study area with the highest value found at location 4 of the study area indicating some level of enrichment of this metals within the study area, also[Rb], [Y] and[Sr]  show some considerable enrichments within the study area as reflected in Figure8c, which show the 2D and 3D geochemical maps of [Rb], [Sr], [Y], [Zn] and [Zr] in Ibodi study area; while Figure 7 show Pie charts of various concentrations of trace Elements within the Ibodi stream sediments.The geo-accumulation index (Igeo) is an environmental parameter that enables the assessment of contamination by means of comparism.It is used in relation to bottom sediment

Table 1 .
Major Element Oxides Composition Of Ibodi Study Area (Wt %)

Table 2 .
Summary of Major Element in the Stream Sediment

Table 3 .
Correlation Co-Efficients for Major Element Oxides

Table 4 .
Trace Element Concentrations (ppm) in Stream Sediment of the Study Area

Table 5 .
Summary of Selected Trace Elements Concentration of Stream Sediments

Table 7 .
Geo-Accumulation Distribution of the Elements Against the Locations