RESUMO
BACKGROUND: Soil contamination with heavy metals has severely increased over the last few decades, mainly from industrial wastes and human activities. Soil pollution is a source of danger to the health of people globally. OBJECTIVES: To assess the level of soil contamination with heavy metals around steel rolling mills in Jinja municipality, Uganda. METHODS: Four composite soil samples were collected from each of the sides of the Jinja steel rolling mills, dried and digested. The digested solution samples were analyzed in triplicates for the levels of lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), copper (Cu), and nickel (Ni), using a flame atomic absorption spectrometer (Savant AA model 2009); the analytical process was monitored using analytical standard solutions. Data analysis was performed using Statistical Package for the Social Sciences (SPSS) software version 19 and Excel. Mean metal concentrations, standard deviations, medians, and skewness were obtained to describe heavy metal concentrations in the soil. Pollution load index and geo-accumulation indices were calculated to determine the level and extent of heavy metal contamination in the soil. RESULTS: The mean concentration loads of the heavy metals in soils around the Jinja steel rolling mills were 43.15 mg/kg for Pb, 28.16 mg/kg for Zn, 0.93 mg/kg for Cd, 0.22 mg/kg for Cr, 80.96 mg/kg for Cu, and 9.40 mg/kg for Ni. The metal load distribution around the industry was in descending order: Left-hand side > Downwind side > Right-hand side > Upwind side. Results for the geo-accumulation index were 1.30 for Pb, -1.31 for Zn, 2.63 for Cd, -7.25 for Cr, 2.99 for Cu, and -1.19 for Ni. The overall pollution load index was 1.08. CONCLUSIONS: The concentration levels of heavy metals around the steel rolling mills did not appear to be of serious concern, except for copper and cadmium, which showed moderate pollution and moderate to strong pollution, respectively. All heavy metals were within the limits of the United States Environmental Protection Agency (USEPA) residential soil standards and the Dutch intervention soil standards. Overall, soils around the Jinja steel rolling mills were slightly polluted with heavy metals, and measures therefore need to be taken to prevent further soil contamination with heavy metals.
