Heavy Metal Contamination in Cocoyam Crops and Soils in Countries around the Lake Victoria Basin (Tanzania, Uganda and Kenya)

Abstract

A study to determine heavy metals concentration and their correlation between soil and cocoyam crops grown at different wetland locations in Tanzania, Kenya and Uganda around Lake Victoria basin was done. A total of 48 cocoyams and 48 soil samples (taken at 0-15 cm deep) were collected in triplicate from various locations in three districts in each country. They were analysed for Mercury (Hg), Arsenic (As), Lead (Pb), Chromium (Cr) and Copper (Cu) concentrations using atomic absorption spectrophotometry (AAS). The mean heavy metals concentration in cocoyam samples were above maximum permissible limits of 0.1 mg/kg for Hg, As and Pb and 5 mg/kg for Cu established by FAO/WHO (1995) and EU (2004; 2006) rendering them unsafe for human consumption. Heavy metals concentrations in soils were higher than in cocoyam samples in all locations in all countries . As and Cr concentrations however, were below the maximum permissible limits of 20 and 75 mg/kg respectively, in all countries. Heavy metals variation occurred both within and among countries, with Kampala, Uganda having significantly (p<0.05) higher values than other locations and countries,  respectively. With exception of Pb in Uganda, insignificant correlation (p>0.05) between soil and the corresponding cocoyam crops grown was observed for other metals. Soil and cocoyam crops grown in the selected locations along the wetlands of Lake Victoria basin are contaminated with heavy metals and thus pose health risk to the consumers

Keywords: cocoyams, soil, Mercury, Arsenic, Lead, Chromium, Copper