Geosciences 2014, 4(1): 23-28 DOI: 10.5923/j.geo.20140401.03 Distribution of Heavy Metals in Urban Soils; A Case Study of Calabar Area, South-Eastern Nigeria Azubuike S. Ekwere * , Solomon J. Ekwere, Bassey E. Ephraim, Anthony N. Ugbaja Department of Geology, University of Calabar, Calabar, Nigeria Abstract This work presents an attempt to establish the degree of anthropogenic influences of selected trace metals distribution in soils from Calabar area of south-eastern Nigeria. Fe, Mn, Pb, Cu, Zn, Cd, Co, Cr, As and Ni concentrations were determined for soils of different categories within the study area. Various geo-statistical and other techniques were used for assessment of the metal concentration in the Calabar urban soils. Geochemical data show the metal levels to be within background values and geo-accumulation index (I geo ) confirms that these metals are unpolluted – moderately polluted, thereby posing no significant environmental impact. The slightly elevated concentration of Pb are attributable to emissions from automobile along motored roads, waste disposal from automobile repair shops and other forms of indiscriminate dumping of effluents within the commercial areas. Principal component analyses; correlation, factor and cluster analyses indicates dominant lithogenic control and subordinate anthropogenesis. Metal speciation reveals that the trace elements are unsaturated and bound in immobile phases with some occurring as free mobile ions. Keywords Heavy Metals, Soils, Geo-accumulation Index, Calabar, Nigeria 1. Introduction Geochemical mapping and techniques have in recent times found diverse applications in studies of urban environment using various sampling media. This has been geared by the need to identify contaminated land and subsequent health risk assessments. Soils are considered as a very important ecological crossroad in the landscape because it constitutes a recognizable repository for the transfer, retention and domiciliation of current or potentially toxic pollutants within the geo-system. The contents of these potential pollutants may be from natural sources but increases with time are related to anthropogenesis of urbanization. Rock weathering often mobilizes elements into the soil leading to distribution and dispersion along the geochemical cycle in the secondary environment. Contents of these metals in soils govern the composition of the elements in plants and animals with an attendant influence on human and animal health. Trace element distribution in soils depends on factors such as nature of the parent material, weathering processes, human activity and climatic conditions (Martinez et al., 2003). Trace metals such as As, Pd, Cd are characterized by long residual periods, high invisibility, little transfer, high toxicity and complexity of behaviours (Alloway, 1995). Trace metals, even the most potentially toxic ones can be essential * Corresponding author: zerratta77@yahoo.com (Azubuike S. Ekwere) Published online at http://journal.sapub.org/geo Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved nutrients for growth of plants and animals but exposure to elevated levels can pose threat to health and life (Nriagu and Pzcyna, 1988; Qian et al., 1996). The assessment of potentially toxic elements in soils and sediments in urbanized and industrial settings are evident in the works of Zachmann and Block, 1993; Thuy et al., 2000; Manjunatha et al., 2001; Abrahim and Parker, 2002; Edet et al., 2003; Ekwere and Elueze, 2011 and Foli et al., 2012). The Calabar area, where the present research is conducted, is an attractive socio-economic centre of the nation due to its thriving tourism potentials and fast developing sea port. Most of the lands in the metropolis are used for different purposes including residence, hospitality, industrial and commercial activities, agriculture and reserves. The influx of visitors during the annual carnival parade and the resulting rapid growth of human and industrial population in the area are bound to affect the environmental quality of surface soils in the area. This study therefore attempts to provide information on soil chemistry and possible anthropogenic impacts of environmental pollution in the metropolis. This is relevant for the management and sustainable development of this rapidly developing urban setting. 1.1. Description of Study Area The study area spans two local administrative political units; Calabar municipality and Calabar-South local council. Both constitute the larger Calabar metropolis, which was the first administrative capital of Nigeria. Geographically the area is delimited by latitudes 4° 15′ - 5° 15′ North and longitudes 8° 15′ - 8° 25′ East (Fig. 1). The area receives an