Some trace metals content of atmospheric dusts deposition in Katima Mulilo metropolis, Namibia

Abstract

Trace metals content of atmospheric dusts continue to attract global attention as more anthropogenic activities including urban road construction impacted on the natural metals load of airborne particulates. This study employed analytical procedures to investigate the concentrations of arsenic, cadmium, cobalt, chromium, copper, nickel, lead, vanadium, tin and manganese in atmospheric dusts deposition in Katima Mulilo metropolis, Namibia. Replicate samples were collected on five days interval under dry winter conditions from mid- August to mid-October, 2013. Samples were collected from within 40 m radius at selected locations along Katima Mulilo urban road construction and from a quite residential area; 2 km away from the road work. Processed samples were digested by EPA method 3050B followed by Inductively Coupled Plasma-Optical Emission Spectrophometer (ICP: Perkin Elmer Optima 7000 DV) analysis. The results obtained showed that manganese recorded the highest concentration in the dusts deposition collected within the urban road construction (155.67±2.52 mg/kg) and residential area (64.00±2.64 mg/kg) respectively. Tin recorded the lowest concentration with mean levels of 0.60±0.10 mg/kg along the road construction and 0.24±0.07 mg/kg in the residential area. T-test analysis of the variations in concentrations of the trace metals were statistically significant (p < 0.05). However, the levels of the trace metals recorded in this study were lower than their permissible concentrations recommended by Canadian soil quality guidelines for the protection of environment and human health. There is a very strong positive inter-elemental correlations and the metals enrichment factors showed moderate enrichment. These suggested common and input from anthropogenically induced sources respectively. Single element pollution indexes of the metals showed low contaminations but the levels of arsenic, cadmium, nickel and vanadium in the atmospheric dusts deposition could become source of health concern following environmental accumulations and non-biodegradation of the trace metals. Thus, it is recommended that periodic evaluation of the trace metals content of the atmospheric dusts deposition should be sustained to monitor future accumulation.