Research Article Exchange Characteristics of Lead, Zinc, and Cadmium in Selected Tropical Soils Tope O. Bolanle-Ojo, 1 Abiodun D. Joshua, 2 Opeyemi A. Agbo-Adediran, 3 Ademola S. Ogundana, 3 Kayode A. Aiyeyika, 1 Adebisi P. Ojo, 1 and Olubunmi O. Ayodele 1 1 Forestry Research Institute of Nigeria, P.M.B. 5054, Ibadan 234-02, Oyo State, Nigeria 2 Federal College of Wildlife Management, P.M.B. 268, New Bussa 234-02, Niger State, Nigeria 3 Federal College of Forestry, P.M.B. 5054, Ibadan 234-02, Oyo State, Nigeria Correspondence should be addressed to Olubunmi O. Ayodele; bayodele2002@gmail.com Received 31 July 2013; Revised 17 October 2013; Accepted 4 November 2013; Published 16 January 2014 Academic Editor: Silvia Imhof Copyright © 2014 Tope O. Bolanle-Ojo et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conducting binary-exchange experiments is a common way to identify cationic preferences of exchangeable phases in soil. Cation exchange reactions and thermodynamic studies of Pb 2+ /Ca 2+ , Cd 2+ /Ca 2+ , and Zn 2+ /Ca 2+ were carried out on three surface (0– 30 cm) soil samples from Adamawa and Niger States in Nigeria using the batch method. he physicochemical properties studies of the soils showed that the soils have neutral pH values, low organic matter contents, low exchangeable bases, and low efective cation exchange capacity (mean: 3.27 cmolc kg −1 ) but relatively high base saturations (≫50%) with an average of 75.9%. he amount of cations sorbed in all cases did not exceed the soils cation exchange capacity (CEC) values, except for Pb sorption in the entisol-AD2 and alisol-AD3, where the CEC were exceeded at high Pb loading. Calculated selectivity coeicients were greater than unity across a wide range of exchanger phase composition, indicating a preference for these cations over Ca 2+ . he  eq values obtained in this work were all positive, indicating that the exchange reactions were favoured and equally feasible. hese values indicated that the Ca/soil systems were readily converted to the cation/soil system. he thermodynamic parameters calculated for the exchange of these cations were generally low, but values suggest spontaneous reactions. 1. Introduction Baseline concentration of heavy metals in soils depends on the local geology. his has been supplemented to various degrees by anthropogenic inputs from industrial processes and operations that generate wastes containing considerable amounts of these metals. Heavy metals are nonbiodegradable and hence environmentally persistent and may accumulate in biota and the soils where they can afect soil properties. hey interact with soils in various ways but sorption from aqueous solution onto solid particles is an important process that inluences their accumulation and transport in the environment [1]. hus, heavy metals pollution in soils has become a signiicant topic of concern. Nowhere has the situation become more serious than in developing countries due to the recent establishment of industries producing wastes and eluents containing heavy metals. his has led to increase in the heavy metal burden of the developing countries where waste management practices are poor and the inal metal sink is the soil. Metals may interact with soils in many ways: they may be sorbed by the soil depending on the soil pH, organic matter content, cation exchange capacity, and so forth; the oxidation state of some metals may be changed, thus afecting their mobility, bioavailability, and toxicity [1]. Our major concern is however the displacement of the major exchangeable cations, Ca, Na and K, by toxic heavy metals, thus increasing their chances of absorption by plants and consequently man via the food chain [2]. Furthermore, due to the selective retention and com- petitive adsorption by the soil, there is the tendency of increasing the concentration of these elements in the soil Hindawi Publishing Corporation International Journal of Agronomy Volume 2014, Article ID 428569, 7 pages http://dx.doi.org/10.1155/2014/428569