Survey of the Levels of some Heavy Metals in Roadside Dusts along Katima Mulilo Urban Road Construction, Namibia

Abstract

Roadside dusts pollutions with heavy metals continue to attract attention as more anthropogenic activities including urban road construction impacted on the natural metal loads of the environment. This study employed analytical procedures to investigate the concentrations of arsenic, lead, chromium, cadmium, cobalt, copper, nickel, manganese, vanadium, iron and tin in the roadside dusts along Katima Mulilo urban road construction. Replicate dusts samples collected from three different areas of the road and a quiet residential area (control) were digested by EPA method 3050B followed by Inductively Coupled Plasma-Optical Emission Spectrophotometer (ICP: Perkin Elmer Optima 7000 DV) analysis. The results of levels of the heavy metals revealed that iron recorded the highest concentration of 7491.13±0.15 mg/kg along the road construction while tin recorded the lowest value (0.27±0.13 mg/kg). Similar trend was observed at the control area located 1.5 km away from the road: iron recorded the highest concentration of 2327.17±0.12 mg/kg while tin recorded the lowest concentration (0.20±0.10 mg/kg). The analysis of variance of the heavy metal concentrations across the sample locations were statistically significant (p > 0.05). However, the levels of the heavy metals recorded cross the sampling areas were less than their soil maximum permissible concentrations. There are strong positive inter-elemental correlations between the sampling areas while result of the soil enrichment factors showed significant enrichment; which are related to common and input from anthropogenically induced sources respectively. The results of single element pollution indexes of the heavy metals showed low contaminations but elevated levels of arsenic and cadmium in all the sampling areas. These could become a potential source of health concern following environmental accumulation and non-biodegradation of the heavy metals. Thus, it is recommended among others that an environmental impact assessment should be carried out on gravel sites to be used in urban road construction to limit heavy metal contaminations of roadside dusts following their usage.