ASSESSMENT OF THE QUALITY OF WILDLAND SOIL OF OLI FOREST KAINJI LAKE NATIONAL PARK BORGU SECTOR, NIGERIA
ASSESSMENT OF THE QUALITY OF WILDLAND SOIL OF OLI FOREST KAINJI LAKE NATIONAL PARK BORGU SECTOR, NIGERIA
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Date
2014-08
Authors
OMOTUGBA, Stephen Kayode
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Abstract
Seasonal study of some potentially environmental toxic heavy metals Cd, Cr, Ni, Pb, Zn, and Cu in soil was carried out in five different vegetation zones of Oli Camp, Kainji Lake National Park at two different depths (0 – 15 cm and 15 – 30 cm) in the wet and dry seasons of 2011 and 2012. The vegetations are Isoberlinia woodland (S1), Terminalia macroptera woodland (S2), Burkea African/Detarium microcarpum woodland (S3), Riparian forest (S4) and Diospyrus mespiliformis (S5). The soil samples were analysed for physicochemical parameters and the mean heavy metal contents using atomic absorption Spectrophotometry. For the wet season of 2011 at 0 - 15 cm depth levels of metal in (mg/kg) were in the order S1: Cd (10.73 ± 2.00), Zn (14.63 ± 0.90), Pb (20.08 ± 3.40), Ni (29.14 ± 2.90), Cu (34.21 ± 0.00); and Cr (39.39 ± 2.30), and S2: Cd (11.56 ± 4.00), Ni (12.03 ± 3.45), Pb (18.97 ± 4.50), Cu (24.11 ± 2.78); Cr (47.34 ± 6.70), and Zn (85.07 ± 1.40). The values for S3: Cd (7.17 ± 2.45), Zn (12.51 ± 0.90), Pb (19.73 ± 1.00), Ni (24.67 ± 1.20), Cr (37.48 ± 2.22), and Cu (47.52 ± 2.10); S4: Cd (8.00 ± 1.30), Ni (10.93 ± 1.00), Zn (19.44 ± 2.30), Pb (19.74 ± 1.00), Cu (35.21 ± 0.00), and Cr (37.96 ± 3.00). In S5 the order: Cd (1.95 ± 0.00), Cu (7.92 ± 0.40), Ni (25.27 ± 1.80), Pb (10.74 ± 1.20), Cr (40.35 ± 2.60), and Zn (211.35±4.30) was obtained. Generally, the heavy metal level obtained for the sub soil (15 – 30 cm) was less than the to-soil counterpart in the wet season of 2011. The mean value of metals in the soils during the wet season of 2011 at 15 – 30 cm depth follow the order of Zn > Cu > Cr > Ni > Pb > Cd for the different vegetation zones studied. The levels of the metals during the dry season of 2011 were generally lower at the 0 - 15 cm and 15 – 30 cm depths compared to the wet season values. The lowest value for the dry season was Cd (0.74 ± 0.02 to 2.26 ± 0.01); and the highest was Zn (160.06 ± 0.56 to 323.08 ± 2.10) mg/kg. During the wet season of 2012, a similar trend in the level of
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metals like in 2011 was obtained, with no significant difference (P < 0.05). The soil samples in the wet and dry seasons of 2011 had the physico - chemical parameters values: pH of 6.65 to 6.95 and 5.3 to 6.7; conductivity of 10.00 ± 2.50 to 101.50 ± 2.12 μScm-1; organic matter, 1.79 ± 0.30 to 2.64 ± 0.51 in the different vegetation zones at the 0 - 15 cm and 15 – 30 cm depths respectively, the order was similar for the wet and dry season of 2012 at the two depths. The result of the sequential extraction of Oli Forest soil at the different vegetation zones shows that Cd, Cr, Ni, Pb, Zn and Cu existed in the fractions in order; residual > carbonate > Fe-MnO > Exchangeable > Organic > Water soluble fractions. High abundance of the metals in the residual fraction implies that the metals are of lithogenic origin and low mobility of the metals in the studied soil. The average potential mobility for the metals studied is in the order: Cr > Cu > Zn > Pb > Ni > Cd. The metals generally have low mobility factor (MF). An enrichment factor (EF) < 1.5 was obtained for the metals, indicating possible crustal materials or natural weathering processes as major source of the metals in the studied areas. In addition, geo - accumulation index < 1.0 was obtained for the metals indicating that the soils from the different vegetation zones of Oli Forest have background metal concentration. This study serves to create awareness on the pollution indices of heavy metals in Oli Forest of Kainji Lake National Park, and calls for the attention of stakeholders in the mitigation of metal pollutant as this is barely monitored.
Description
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF DOCTOR OF PHILOSOPHY IN ANALYTICAL CHEMISTRY DEPARTMENT OF CHEMISTRY FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY ZARIA
AUGUST, 2014
Keywords
ASSESSMENT,, QUALITY,, WILDLAND SOIL,, OLI FOREST,, KAINJI LAKE,, NATIONAL PARK,, BORGU SECTOR,, NIGERIA.