Measurement of the Level of Some Heavy Metals in Fall-out Dusts at Rehoboth Town, Hardap Region, Namibia

Abstract

Aims: To determine the levels of heavy metals in fall-out dust from Rehoboth town, Hardap region, Namibia. Study Design: Modified open bucket samplers were used to collect the settleable particulate. Six “ordinary” open buckets were placed at different locations (Blocks A to F). In Rehoboth town. Each bucket’s contents were filtered using a Buchner funnel connected to the diaphragm vacuum pump. The residues collected after the filtering were dried and transferred into clean, pre-labelled polyethylene bags and then transported to Analytical Laboratory Services, Windhoek Namibia, for further processing and analyses. Place and Duration of Study: Rehoboth town, Hardap region, Namibia, between September 2015 and December 2015. Methodology: The samples were digested according to EPA method 3050B for Inductively Coupled Plasma-Optical Emission Spectrophotometer (ICP-OES) analysis. Ten (10) mL of each digestate was taken and mixed with equal volume of matrix modifier and then analysed using ICP-OES (ICP: Perkin Elmer Optima 7000 DV) for the levels of chromium, cadmium, lead, arsenic, manganese, zinc and nickel. Results: The levels of heavy metals obtained showed the metals’ enrichment of the dust fall ranging between 0.05 – 1.38 Block A; 0.06-37.44 Block B; 0.05-3.43 Block C; 0.05-4.68 Block D; 0.09-1.73 Block E and 0.09-1.56 Block F respectively. This showed very high enrichment for Block B and deficient to minimal, moderate enrichment for Blocks A, C, D, E and F. The results of contamination factors indicated moderate, considerate and highly contaminated dust fall with the heavy metals; which are related to common and input from anthropogenically induced sources.  Conclusion: Human activities in the town of Rehoboth, Namibia have obviously increased the levels of heavy metals in dust fall-out. The calculation of pollution load index (PLI) clearly points to deterioration of site quality. This obviously is a grave concern following environmental accumulation and non-biodegradation of heavy metal and hence, the need to have all major roads and inter linking street roads to be paved to mitigate the release of dust into the atmosphere.