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Title: Heavy Metal Accumulation in Wastewater Irrigated Soil and Lettuce (Lactuca sativa) at Dzorwulu and Airport Residential Area in Accra
Authors: Addo, Divine
Issue Date: 30-Jul-2014
Abstract: Heavy metal contamination of agricultural soils due to human activities is a major concern globally. In this work, heavy metals accumulation in wastewater irrigated soil and lettuce at Dzorwulu and Airport residential area in Accra were investigated. Ten (10) soil samples were taken from each site. Soil properties such as pH, electrical conductivity (EC), organic carbon, cation exchange capacity (CEC) and heavy metals content were determined using standard procedures. Lettuce samples from the farms were analysed for heavy meals. The soils were found to be sandy clay loam and sandy loamy in texture and moderately to slightly alkaline. The organic carbon contents were found to be relatively low (0.90 ± 0.06 and 1.18 ± 0.02) for Dzorwulu and Airport residential area respectively. The mean CEC ranged between 1.58 ±0.03 and 1.75 ± 0.04 for Airport residential area and Dzorwulu samples respectively. The soil EC result indicated low salt accumulations at both sites. The sequence of heavy metal levels in the soil samples from Airport residential area was in the order Zn > Pb > Cu > Ni > Cd > Cr whilst that of Dzorwulu was in the order Zn > Pb > Cu > Ni > Cr > Cd. The Enrichment Factor results for soil samples from Dzorwulu showed minimal enrichment for Zn, Cu and Cr whiles Pb, Ni and Cd showed no enrichment. However, Pb, Cu and Zn were significantly enriched in the soils from Airport residential area. Geo-accumulation index (Igeo) values showed that soil from the Airport sites were not contaminated with Cr (-0.585), Ni (-0.327) and Cd (-0.524) but slightly contaminated with Cu and Zn. There was moderate contamination from Pb (Igeo 1.100). The Igeo values for Dzorwulu samples showed moderate contamination from Cd, but not from Ni. Results of degree of translocation of these metals by the plants from both sites showed a translocation factor (TF) > 1 for Zn in lettuce samples from Dzorwulu. Heavy metals concentration in the lettuce samples were above the FAO/WHO recommended levels. Overall, the soils from both sides can be described as ranging from unpolluted to moderately polluted. The concentrations of metals in the lettuce indicate the abilities of the lettuce to uptake and accumulate metals from the soil on which it was grown. The levels of these heavy metals might place the consumers of this crop grown on such soils at a health risk with time.
Description: A Thesis Submitted to the Department of Environmental Science, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfillment of the requirement for the award of the Master of Science Degree in Environmental Science, May-2014
URI: http://hdl.handle.net/123456789/6216
Appears in Collections:College of Science

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