Heavy Metal Concentrations in Soil from Selected Rice Farms at Cheju, Zanzibar

Abstract

Advancement of science and technology has enhanced the use of chemical products, such as fertilizer and pesticides, into agriculture to improve yield. Normally, these products contain metals which are detrimental to human health. These metals may be absorbed by plants and hence be introduced into food chain. In this study, samples of soil from Cheju rice farms were analyzed for heavy metals associated with agrochemicals using Energy Dispersive X-ray Fluorescence (EDXRF) Spectrometry. Sixty soil samples were collected from Cheju rice farms and 10 control samples were collected from Mwera about 25 km from Cheju. T-test to compare the mean concentrations of elements in fertilized and control soils showed that the soil samples from Cheju farms had significantly higher concentrations of most of the determined metals compared to the control sample. Higher concentrations of these elements in fertilized soil may be attributed to the repeated use of agrochemicals in farming. Analysis of rice grains from the field and other samples from the neighbouring ecosystem is recommended.