Selected trace elements evaluation in soil from an urban farming area

Urban farming makes a substantial influence on the household economy of the urban poor especially in developing countries. Urban soil the hot spot of urban farming is a natural sink for contaminants especially the trace elements derived mainly from anthropogenic activities. This study’s aim was to quantify the concentrations of selected trace elements (Cr, Mn, Cu, Ni, and Zn) in topsoil (0-20 cm) and subsoil (21-50 cm) and to evaluate whether their concentration vary during dry and rainy season. Grid soil sampling method was used to collect soil samples and their total concentration was determined using a portable X-ray Fluorescence Spectrometer. The study revealed that the topsoil had higher concentration than sub soil. The topsoil concentration in mg/kg were 61.62, 4042.58, 30.82, 43.90 and 456.43 for Cr, Mn, Ni, Cu and Zn respectively.  The subsoil concentration in mg/kg were 54.67, 3791.38, 30.32, 27.83 and 370.32 for Cr, Mn, Ni, Cu and Zn respectively. It also noted that concentration of the trace elements was higher during dry season than wet season but not significantly different (P ≥ .05) for all the elements. This study recommends that the level of trace elements studied in the soil be monitored to ensure that it does not reach the harmful levels.