Lead accumulation in surface soils and components of Balenites aegyptica specie in a Katsina urban area, Nigeria.

OBJECTIVE: The main objective of this paper is to assess the impact of various vehicular traffic densities on lead (Pb) accumulations in some environmental components in Katsina, a semi-arid urban area of Nigeria. METHODS: This was achieved by collecting and analyzing samples of surface soils, fruits, kernels, leaves, and barks of Balanites aegyptica from locations of different vehicular traffic densities in the area, and analyzing them for lead, using atomic absorption spectrophotometry. RESULTS: The results obtained revealed that the Pb concentration in the high, medium, low, and zero traffic density areas are, 75, 53, 35, and 12 microg x g(-1) respectively for the fruit pulp. They are also16, 13, 8, and 6 microg x g(-1) for fruit kernel and 44, 28, 17, and 9 microg x g(-1) respectively for leaves. For tree barks, the values are 138, 97, 64, and 18 microg x g(-1) respectively while for under-tree-canopy soil samples the mean values are 99, 74, 44, and 17 microg x g(-1). In the case of outside-canopy soil samples, the mean values are 113, 91, 50, and 18 microg x g(-1) respectively for the various classes of vehicular traffic density. CONCLUSION: These results indicate a strong influence of vehicular traffic density on Pb emission into surrounding atmosphere and its subsequent precipitation on soil and components of B. aegyptica specie in the area. Of all the samples, tree bark should be the best index of assessing Pb pollution in the area, as it maintains the closest contact with the surrounding atmosphere. Since Pb has no known lower limit for human tolerance, there is an urgent need for Pb pollution control in the area to be effectively enforced.

Cu, Mn, Fe, and Zn levels in soils of Shika area, Nigeria.

OBJECTIVE: Heavy metals presented in toxic amounts can become injurious to human health. In areas where there is a high level of human activities on soils (such as agriculture and grazing) studies are therefore required from time to time to monitor levels of such metals in the soils in order to identify the point in time when toxicity problems become real. The objective of this paper is to determine the concentrations of some trace metals (Cu, Mn, Fe, and Zn) in soils under cultivation and grazing practices in Shika, a rural area of Kaduna state of Nigeria. METHOD: In this study, soil samples collected from three different categories of locations (cultivated, grazed, and uncultivated/non-grazed serving as a control) across Shika area, Nigeria, were analysed for some trace metal levels (Cu, Mn, Fe, and Zn) using atomic absorption spectrophotometry. For each category, multiple sites were chosen to accommodate all possible intra-category variations, especially in terms of land use and management history and topographic characteristics. Topsoil (0-15 cm) and subsoil (20-30 cm) samples were collected from every site and analysed for the above metals. Averaged values of the metals for the three categories revealed that Zn is the most abundant metal, followed by Fe, then Mn and Cu the least. RESULTS: The results obtained indicate that the cultivation practices, and to a lesser extent grazing, in the area result in higher levels of all the metals than in the control, suggesting that crop immobilization of the metals from soils of the area is low, and that their systematic accumulation is taking place in cultivated soils of the area. Prospects of having elevated soil levels of the metals due to cultivation practices in the area therefore seem quite high. CONCLUSION: On the basis of the results obtained, it was concluded that grazing and cultivation practices have in general caused some significant elevations in the bioavailable (i.e the plant available forms) levels of Zn, Fe, Mn, and Cu in soils of the area.