By Yebpella, Garbunga Gary
Concentrations of twelve elements associated with Pb/Zn mining in Arufu and Akwana were examined in environmental samples after acid digestion with Varian AA 240 flame atomic absorption spectrophotometer using oxy-acetylene flame and nitrous oxide flame for Al. Average levels (µg/g) of elements in rocks from Arufu and Akwana mines were in the range: As (1.20-8.95), Al (10.19-17.16), Cu (1.20-1597.5), Co (4.66-69.44), Cr (101.90-215.48), Se (95.28-512.05), Mn (12.55-4069.30), Fe (410.85-916.38), Zn (158.90-1710.88) and Pb (194.93-9372.85). The results showed concentration ranges of the investigated parameters in soils: pH (6.42 - 7.31), organic matter (0.212 to 0.493 %), cation exchange capacity (0.101 - 0.145 CECcmol/kg), calcium carbonate (1.44 - 2.48 %). The concentration of trace elements in soils were in the following order: Fe > Mn > Se > Pb > Cr > Zn > Cu > Al > Co > As for Arufu study area and Mn > Se > Fe > Zn > Pb > Cr > Cu > Co > Al > As for Akwana study area. High concentrations reported for Pb, Zn, Mn, Fe, Se and Cr indicate high contributions from the dissolution of ore minerals which was higher in wet than in dry season. Concentrations of trace elements in soil from Fyayi and Kente control areas are as follows: Se > Mn > Fe > Cr > Zn > Cu > Al > As > Co and Se > Mn > Fe > Cr > Pb > Cu > Co > Al > As respectively. Mean concentration (µg/g) of bioavailable metals in soils around the mine fields were Zn (9.01 – 35.17), Cu (1.03 – 4.13), Co (0.26 – 1.29), Fe (18.48 – 319.58), Al (0.16 – 4.70), Mn (7.12 – 48.95), Pb (6.57 – 46.29). The highest available metal was iron with mean level of 243.61 µg/g and the least metal available was chromium and the average mean level was 0.22 µg/g. Degree of soil pollution in Arufu and Akwana study areas is in the following order: Fe > Pb > As > Zn > Cr > Mn > Cu > Co and Fe > Pb > As > Mn >Cr > Cu > Zn > Co respectively while soil enrichment ratios were in the ordere: Pb > Fe > As >,Zn > Mn > Cr > Cu > Co > Al and Fe > Pb >,Zn > As > Mn > Cu > Cr > Co > Al. Degree of soil pollution was between the range of minimal to extremely polluted status judging from the contamination index. Levels of trace elements (g/g), in selected food crops collected from farmlands around Arufu and Akwana mining fields and environs were in the following order of decreasing magnitude: Se (541.12) > Fe (167.68) > Mn (99.91) > Cr (26.22) > Cu (9.35) > Pb (5.28), Al (4.14) > As (1.52). Concentration of Fe and Mn were lower than FAO/WHO standard for food while concentration of Cr, Pb and Cu were higher than the standard. Bioaccumulation factor were in following decreasing order of magnitude: Se > Fe > Cu > Al > As > Mn > Cr > Pb. Lead has the least mobility rate in the soil despite its high availability while Se has the highest rate of mobility. The order of occurrence of trace elements in fish caught from streams around Arufu and Akwana study areas is as follows: Cu < Cr < As < Al < Mn < Se < Pb < Fe while Zn and Co were below detection limits of instrument employed for analysis. The above pattern of metal occurrences in fish present Cu with minimum concentration (0.71 µg/g) and Fe (47.52 µg/g) with maximum concentration. Lead was detected at higher concentration than FAO/WHO food standard. Mean concentration of metals (g/g) in water from Arufu and Akwana mining areas were in the following decreasing order of magnitude: Se (4.16) > Fe (3.26) > Zn (2.93) > Mn (1.55) > Pb (0.22) > Cr (0.09) > Al (0.04) > Cu (0.03) > As (0.02). Concentrations of trace elements like Pb, As, Cr, Se, Co may be low but are higher than WHO water guideline which shows contamination of ground and surface water resources around the study area. This study revealed that soil pollution by some metals is a threat to the health of communities around the mines. High content of Pb, As, Zn and Cu resulting from mining activities may affect soil quality and its ability to sustain plants and animals life.