Journal of Atmospheric Pollution, 2016, Vol. 4, No. 1, 15-22 Available online at http://pubs.sciepub.com/jap/4/1/2 ©Science and Education Publishing DOI:10.12691/jap-4-1-2 Trace Metals in Total Atmospheric Depositions (TAD) of a Nigerian Island C.A. Onwudiegwu 1 , G.C. Ezeh 2,* , I.B. Obioh 2 1 African Institute for Science Policy and Innovations, Obafemi Awolowo University, Ile-Ife Nigeria 2 Atmospheric Research and Information Analysis Laboratory (ARIAL), Centre for Energy Research and Development (CERD), Obafemi Awolowo University Ile-Ife *Corresponding author: gcezeh@cerd.gov.ng, goddyich@yahoo.com Abstract The paucity of data on air quality studies in Nigeria prompted us to commence the monitoring of total atmospheric deposition (TAD) in Lagos Island, Nigeria. TAD samples were collected every 30 days for a period of two years using a local assembled gauge fashioned after the Australian model gauge. Elemental characterization was carried out by Particle Induced X-ray Emission (PIXE) technique via an in-vacuum ion beam set-up. The TAD rates ranged from 1 to 62 g -1 m 3 month -1 . Twenty-eight elements (Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Ga, As, Zn, Se, Br, Rb, Y, Nb, Mo, Sr, Zr and Pb) were detected in both fractions and their concentrations were assessed. Enrichment factors (EF) and pollution indices (PLI) were calculated and results revealed that most elements were anthropogenic with concentrations exceeding the World Health Organization guideline standards. Keywords: atmospheric, anthropogenic, air quality, PIXE, pollution, ion beam Cite This Article: C.A. Onwudiegwu, G.C. Ezeh, and I.B. Obioh, “Trace Metals in Total Atmospheric Depositions (TAD) of a Nigerian Island.” Journal of Atmospheric Pollution, vol. 4, no. 1 (2016): 15-22. doi: 10.12691/jap-4-1-2. 1. Introduction In urban areas, anthropogenic activities have led to the generation of atmospheric emission of mostly sub-micron particles. These particles may be transported over very long distances: the so-called remote pollution by urban areas has been studied over lakes or seas where it may feature as a major trace metal input to large aquatic ecosystems. Nevertheless, significant wet and dry fallout also occur locally, and atmospheric fluxes onto impervious urban surfaces may significantly contribute to the contamination of urban runoff and play an important role in the urban cycle of metals, and further downstream on the contamination of receiving ecosystems. Although metal contamination of urban aerosols is widely recognized, only few studies [1,2,3,4] have been devoted to the Lagos conurbation. Yet the reported studies focused on size segregated aerosols (PM 2.5 and PM 2.5-10 ) hence the need to investigate trace metals associated with TAD. Metal transfer through the atmosphere is a significant part of the biogeochemical cycle of these elements [5]. There are two process which increase heavy metal concentrations in the atmosphere: natural and anthropogenic [6]. Natural sources are mainly composed of soil, sea water and volcanic dusts and gases. Anthropogenic emissions come from industrial gases and aerosols or fossil-fuel combustion [7]. Incineration of urban waste is also identified as major atmospheric source of trace metals [8]. Metallic pollutants may be transported over long distances as very small particles [9]. These particles when aggregated or washed out by rain are called atmospheric deposition, respectively, dry and wet. Dry deposition of particles occurs by direct impact and gravitational settling on land or water surfaces. In wet deposition, aerosols and gases are dissolved or suspended in water droplets or ice crystals. Besides such long-range transport processes, significant dry and wet depositions also occur locally, and atmospheric sources in urban area may play an important role in the metal contamination of atmospheric depositions [10]. Since heavy metals present high toxicity and high lability in atmospheric fallouts [11], its monitoring and characterization are important in-order to understand air quality issues that could arise in the environment due to elemental enrichments. Accelerator-based ion beam analysis (IBA) techniques have been applied for characterization of heavy metals associated with TAD for many years [12]. They are well suited for such studies as IBA techniques have several unique advantages. The techniques have multi-elemental analysis capabilities; low minimum detection limits (MDLs) for a very broad range of elements in the Periodic Table and can quantitatively detect picograms of material in micrograms of sample [13]. With the use of IBA accelerator-based PIXE (Particle Induced X-ray Emission) technique, systematic investigations of TAD have been performed for several years [14]. Thus, with the application of IBA, an improved data set for source apportionment studies could be achieved since the output of source apportionment depends on the quality of elemental compositions analyzed [13].