Monitoring of sulfur dioxide in the guinea savanna zone of Nigeria: implications of the atmospheric photochemistry

The level of sulfur(IV) oxide (SO2) in the tropospheric environment of Ilorin is presented using three urban classes and a control site from 2003-2006 wet and dry seasons. The mean concentrations over the years during wet and dry seasons were 1.29 ± 0.17 and 7.17 ± 0.87 (ppb), respectively. The wet season concentration was 15.25% lower than the dry season due to rain attenuation. The mean values at the control site for two seasons were one order of magnitude lower than those in the urban sites. The overall average concentration over Ilorin city was 4.23 ± 0.52 ppb. The value is comparable with other cities of the world and is within the limit of the United State Environmental Protection Agency (USEPA) Guidelines for Air Quality Standards. SO2 levels were found to varied significantly with vehicular intensity, other anthropogenic activities also decreased drastically during wet season. There was a significant difference (p = 0.05) between SO2 concentration with high and low traffic flow count; however, there was no difference (p = 0.05) between high traffic/medium population and medium traffic/high population density areas. The regression analysis indicated a correlation between SO2 and the hourly traffic volume in almost all the sites

Heavy Metals Distribution and Speciation in Soils around a Mega Cement Factory in North-Central Nigeria

Surface and sub-surface soils were sampled in the neighbourhood environment of an ultra-modern and largest cement factory in Nigeria. The five geochemical fractions investigated were exchangeable, carbonate, Fe-Mn oxide, organic matter and residual. All fractions were subsequently analyzed for lead (Pb), copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) using atomic absorption spectrophotometer. The average total metals concentrations (mg/Kg) in the surface soil were 1063.8± 261 for Fe, 30.29 ± 19.25 for Mn, 24.15 ± 21.69 for Cu, 15.08 ± 11.95 for Pb and 8.54 ± 3.18 for Zn. Relatively lower mean concentrations were measured in the sub-surface soil samples. The percent distribution concentration of the various metals in the residual fraction ranged from 0.23 to 69.48% for Pb, 0.85 to 75.30% for Cu, 36.02 to 83.86% for Zn, 12.97 to 44.04% for Mn and 18.11 to 57.25% for Fe. Factor analysis revealed that while Pb, Cu and Zn would majorly be of anthropogenic origin, Mn and Fe are mainly of natural origin. Pb was found to be the most mobile with mobility factor of 71.8% while Fe has the least mobility factor of 3.62%. Regression analysis (r2 = 0.71) further showed that Cu is correlated with Pb. Soil pollution indices revealed that the surface soil is slightly contaminated in lead and zinc, and moderately contaminated in copper.Key words: Heavy metals speciation, Mobility factor, Soil pollution, Cement industr