Heavy metals status of agricultural soils should be monitored in order to prevent soil-plant pollution. This study evaluates the effect of season, agronomic practice and soil mineral composition on the levels of some ...Heavy metals status of agricultural soils should be monitored in order to prevent soil-plant pollution. This study evaluates the effect of season, agronomic practice and soil mineral composition on the levels of some heavy metals (Pb, Mn, Ni, Fe, and Zn) in the arable and oil palm soils of three Farm Settlements in Ogun-State Southwest, Nigeria. Soil samples were collected in two consecutive seasons between 2010 and 2012 and digestion was carried out using Standard Wet Acid Digestion method. Total heavy metals in the digest were determined using Flame Atomic Absorption Spectrophotometer (FAAS). The total levels of heavy metals (in mg/kg) found in the sampled soils were as follows: in the rainy season Mn (28.4 - 34.2), Fe (1599.7 - 2013.2), Pb (11.0 - 16.9), Zn (100.5 - 112.9) and Ni (11.3 - 13.8) and in the dry season Mn (32.1 - 40.1), Fe (1701.4 - 2455.5), Pb (13.0 - 18.7), Zn (105.7 - 110.4) and Ni (15.5 - 16.3). Levels of the heavy metals found in the sampled soils were significantly lower (p < 0.05) than their permissible levels in agricultural soils. Although the levels of heavy metals determined in dry season were higher than those of the rainy season, the only seasonal difference was that of Fe in Sawonjo soil significant at p = 0.05. The level of heavy metals in oil palm soils was significantly higher than the level in arable soils (p < 0.05). At present, pollution level of heavy metals in the sampled soils is low and poses no environmental risk, yet, they have to be regularly monitored before they bio-accumulate into toxic. Government should therefore set up soil monitoring agency and provide irrigation facilities to encourage dry season farming.展开更多
文摘Heavy metals status of agricultural soils should be monitored in order to prevent soil-plant pollution. This study evaluates the effect of season, agronomic practice and soil mineral composition on the levels of some heavy metals (Pb, Mn, Ni, Fe, and Zn) in the arable and oil palm soils of three Farm Settlements in Ogun-State Southwest, Nigeria. Soil samples were collected in two consecutive seasons between 2010 and 2012 and digestion was carried out using Standard Wet Acid Digestion method. Total heavy metals in the digest were determined using Flame Atomic Absorption Spectrophotometer (FAAS). The total levels of heavy metals (in mg/kg) found in the sampled soils were as follows: in the rainy season Mn (28.4 - 34.2), Fe (1599.7 - 2013.2), Pb (11.0 - 16.9), Zn (100.5 - 112.9) and Ni (11.3 - 13.8) and in the dry season Mn (32.1 - 40.1), Fe (1701.4 - 2455.5), Pb (13.0 - 18.7), Zn (105.7 - 110.4) and Ni (15.5 - 16.3). Levels of the heavy metals found in the sampled soils were significantly lower (p < 0.05) than their permissible levels in agricultural soils. Although the levels of heavy metals determined in dry season were higher than those of the rainy season, the only seasonal difference was that of Fe in Sawonjo soil significant at p = 0.05. The level of heavy metals in oil palm soils was significantly higher than the level in arable soils (p < 0.05). At present, pollution level of heavy metals in the sampled soils is low and poses no environmental risk, yet, they have to be regularly monitored before they bio-accumulate into toxic. Government should therefore set up soil monitoring agency and provide irrigation facilities to encourage dry season farming.
