Potentially toxic elements in food crops grown on urban waste dump-sites: a case study of Wakaliga Dump-site, Kampala City, Uganda

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Kampala International University, School of Engineering and Applied Science
This study aimed at investigating the seasonal variation in the levels of contamination in soils, food crops, and domestic spring water samples from Wakaliga dumpsite in Kampala. Potentially Toxic Elements (PTE) and physicochemical properties were analyzed during the dry season (May-July 2017) and the wet season (September-November 2017) and the results compared to standard limits set by international and local agencies. The results obtained indicated that some of the elements were found in concentration levels within permissible limits, while others were above permissible set limits in the soil, crops and domestic (spring) water samples. Zinc maximum levels of 3.41±0.01 mg/kg and 3.3 1±0.04 mg/kg d.w. were found in dry-season picked spinach and sugarcane, respectively, while the lowest concentrations of 0.98±0.02 mg/kg d.w. were found in wet-season cocoyam. Copper was found to exist below permissible limits for all the crops, soil and water; concentrations of lead in spinach were found to be within a permissible limit 2.31±0.005 mg/kg d.w. while all the others were below the permissible limits. Negligible amounts of cadmium were found in all the samples. All the soil samples indicated results below permissible levels of toxic metals in the arable soils as indicated by ‘~ATHO (1996). The physiochemical parameters were all within acceptable limits for drinking water, as set by WHO and NEMA; Cadmium was not detected in the domestic water. The findings of this research indicated the presence of potentially toxic elements whose levels could be on the increase and found out that zinc concentrations were higher in both crops and soil for both the two harvesting seasons. This was followed by lead, which is attributable to the availability of discarded substances containing these elements in the environment. Proper waste management, control and disposal methods should be put in place to minimize exposure of toxic containing substances into the environment.
A dissertation submitted to the school of engineering and applied sciences, Kampala International University, in partial fulfillment of the requirements for the award of the degree of Master of Science in chemistry
Toxic elements, Food crops, Urban waste dump-sites