Abstract

The study was carried out to evaluate heavy metals concentration and their human health risk in some selected crops grown on – farm at close proximity (seven meters away) to Lapite dumpsite in Ibadan. Soil samples: of 0 – 15 and 15 – 30 cm depths were randomly collected, while Xanthosoma sagititolium (cocoyam), Zea mays (maize) and Musa paradisiaca (plantain) grown on-farm were collected at harvest. Soil and crop samples were packed separately, laid out in a completely randomized design and replicated three times. Samples were dried separately, digested and analyzed for heavy metals (Cu, Co and Pb) using Atomic Absorption Spectrometry with standard procedures. Transfer factor (TF) associated with heavy metals concentration and Health Risk Index (HRI) were also determined. Data collected were analyzed using ANOVA at p < 0.05. Results showed significant differences (p<0.05) in the heavy metal concentrations in the soil and crop samples. In soil their levels followed this trend: Pb>Cu>Co with values ranging from 11.53-49.0 mg/kg which were within the permissible limit. The concentrations in crop samples were: Cu>Co>Pb for plantain, Cu>Pb>Co for maize and Cu>Pb>Co for cocoyam. Heavy metals in plantain ranged from 1.83-5.37 mg/kg, maize 0.62-2.50 mg/kg and 0.82-6.82 mg/kg for cocoyam, which were higher than the permissible limit. The highest TF was in Cu (0.3) >0.05, while lowest value was from Pb (0.03) <0.05 in cocoyam, respectively. The HRI of heavy metals in the crop samples followed this trend: Pb>Cu>Co with their values ranging from 0.001- 0.224 which were all <1. This study revealed that heavy metals in both soil depths were within the permissible levels, while Cu and Pb levels in Xanthosoma sagititolium, Zea mays and Musa paradisiaca were above the safe limit level with the exception of Co. However, Transfer Factor (except Cu >0.05) and Health Risk Index showed that all crops were < 0.05 and 1.00, respectively. This indicated that the populace that consumes the crops are not at risk, although ill-health could occur over time through bioaccumulation. Therefore, Lapite dumpsite and crops grown around should be properly monitored.

Key Words: Dumpsite,Heavy metals, Health Risk Index, Transfer Factor