Growing concern about reclamation of auto-repair workshop areas for residential and agricultural purposes makes risk assessment of heavy metal contamination of the study area imperative. In addition, the study is aimed at ascertaining the dispersion of contaminated Zn, Ni, Cr, Hg, and Pb within the soil profile. A total of 75 soil samples from auto-repair workshops and 18 soil samples from control sites were collected. Significant levels of contamination were found in view of elevated levels of these metals above background concentrations in control sites. Average topsoil metal concentrations (0-10 cm) in auto-repair workshop areas were: Zn 0.90 ± 0.5, Ni 11.5 ± 3.3, Cr 5.3 ± 2.3, Hg 9.4 ± 4.6 and Pb 133 ± 66 mg/kg. Lead was the most significant contaminants, and the degree of contamination was highest for Pb followed by Hg. The detailed levels of total metal contamination for Pb and Hg exceeded international thresholds for agricultural use. Enrichment factor within the soil profile metals were Zn 3.37, Ni 3.38, Cr 6.22, Hg 14.5 and Pb 21.1. The enrichment factor reflects the ratio of average concentration at a particular sampling location to average concentration at control sites. The general trend of dispersion of metal contaminants within the soil profile studied is Pb >> Ni > Hg > Cr >>Zn.

Background.Urbanization, energy consumption, intensification of road traffic and rapid population growth pose significant challenges to ambient air quality. Therefore, regular monitoring of current air quality is essential.Objectives.The study investigated the concentration of sulfur dioxide (SO2), oxides of nitrogen (NOx), ozone (O3), ammonia (NH3) and carbon monoxide (CO) in ten different sites to investigate possible anthropogenic sources within Ibadan, Nigeria.Methods. Air samples were collected into specific absorbing solutions twice daily in the morning and afternoon for four weeks. The resulting solutions were analyzed following specific colorimetric techniques according to standard methods of analysis.Results.Average concentrations varied among the sampling areas. All were above background levels obtained at the control site. Overall concentrations were found to be 30±19 μg/m3 (SO2), 63±16 μg/m3 (NOx), 31±18 μg/m3 (O3), 463±180 μg/m3 (NH3) and 0.59±0.21 ppm (CO). These concentrations were present at the study areas at 15, 31, 17, 5 and 3 times the background concentrations for SO2, NOx, O3, NH3 and CO, respectively.Conclusions.In spite of the short duration of sampling, the data can guide future long term monitoring of air quality in Nigeria. The level of SO2 exceeded World Health Organization limits within this short duration. This is an indication of the need for long term air quality monitoring with a sustainable plan for air pollution management.

Co-precipitation procedure has widely been employed for preconcentration and separation of metal ions from the matrices of environmental samples. This is simply due to its simplicity, low consumption of separating solvent and short duration for analysis. Various organic ligands have been used for this purpose. However, there is dearth of information on the application of 8-hydroxyquinoline (8-HQ) as ligand and Cu(II) as carrier element. The use of Cu(II) is desirable because there is no contamination and background adsorption interference. Therefore, the objective of this study was to use 8-HQ in the presence of Cu(II) for coprecipitation of Cd(II), Co(II), Cr(III), Ni(II) and Pb(II) from standard solutions and surface water prior to their determinations by flame atomic absorption spectrometry (FAAS). The effects of pH, sample volume, amount of 8-HQ and Cu(II) and interfering ions on the recoveries of metal ions from standard solutions were monitored using FAAS. The water samples were treated with 8-HQ under the optimum experimental conditions and metal concentrations were determined by FAAS. The metal concentrations in water samples not treated with 8-HQ were also determined. The optimum recovery values for metal ions were higher than 85.0%. The concentrations (mg/L) of Co(II), Ni(II), Cr(III), and Pb(II) in water samples treated with 8-HQ were 0.014 ± 0.002, 0.03 ± 0.01, 0.04 ± 0.02 and 0.05 ± 0.02, respectively. These concentrations and those obtained without coprecipitation technique were significantly different. Coprecipitation procedure using 8-HQ as ligand and Cu(II) as carrier element enhanced the preconcentration and separation of metal ions from the matrix of water sample.

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