Assessment of heavy metals in selected dumpsite soils and plants in Kumasi and Asante Mampong, Ghana

Abstract

This study investigated dumpsite farmers’ soil physicochemical knowledge, heavy metals and their pollution levels in selected dumpsites and background soils and plants in Kumasi and Asante Mampong, Ghana (latitude 5o 50‘ 7.46’’ N, longitude 0o 15‘ 2.25’’ W). Chi - square (ꭓ2) test showed that dumpsites farmers’ soil knowledge had no association (p = 0.21) with farmers’ educational level but showed a significant (p = 0.02) association with farmers awareness that dumpsites soil contain toxic elements; and (p = 0.03) farmers awareness that plants on dumpsites absorb toxic elements. Metals level were determined in soils at 0 - 15 cm and 15 - 30 cm depths with edible parts of plantain and cocoyam; 0 - 30 cm depth of sampled soils in pots with lettuce under field conditions using an XL3t GOLD XRF mass spectrometer. Physicochemical properties of dumpsite soils were higher than that of background soils. Cr, Fe, Ni, Cu, Zn, As, Cd, Hg and Pb were higher by 15 – 25 %. Soil Cu, Zn and Hg at 0 - 15 cm and 15 - 30 cm; soil Ni, Zn and Hg in pots from Magazine dumpsite were all above WHO (2015) limits in soils. Cr, Fe and Hg in plantain leaves and fruits from Magazine dumpsite; Hg in cocoyam leaves from Kyeremfaso dumpsite, and Hg in cocoyam corms from Magazine dumpsite; Cr, Fe, Ni and Cd in lettuce shoots and roots in pots in Magazine dumpsite were above allowable levels by FAO/WHO (2011). Cr and Cd; Fe and Zn; Ni and Cu; Cu, Zn and As; Zn and As; As and Pb; Hg and Pb association showed they have similar contamination sources. Cr and Fe; Cu, Cr and Zn showed antagonistic and synergistic type of behavior. Soil pH, SOM, CEC, Clay and soil available P influenced Cr, Fe, Ni, Cu, Zn, As and Cd. Pollution indices (Igeo, EF, RTEF, TR and TF) indicated very high contamination for Fe, Cu, Zn and Hg in the order of KYE < AYE < SUA. Education on dumpsites farming must be intensified and excavate dumpsites to landfill sites.