Heavy metals contamination of water, soil, and plants around an electronic waste dumpsite

Electronic waste (e-waste) has become a subject of growing environmental concern in developing countries due to legal/illegal import of electronics from developed nations. In this study, concentrations of heavy metals in and around the largest e-waste dumping site in Nigeria, Alaba International Market in Lagos, was investigated. Concentrations of five heavy metals, namely: cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni), and zinc (Zn) in soil, water, and plant samples during the wet and dry seasons were measured using atomic absorption spectrometry (AAS). Samples were collected between October 2011 and May 2012 and digested using standard wet digestion methods. Pb recorded the highest values, while the lowest were found for Cd in all the samples during the dry season. Heavy metal concentrations were generally lower during the wet season due to increased aeration and dilution from rainfall. Results show that the total mean concentrations of the heavy metals decreased with depth in soil samples and distance from the dumpsite. Possible sources of contamination were also discussed. A noteworthy observation was that the concentrations of most of the heavy metals under investigation exceeded maximum permissible levels.