HEAVY METAL CONTAMINATION OF VEGETABLES PLANTED IN LAGOS SOILS AND THEIR POTENTIAL POLLUTION RISKS

Abstract

Vegetables can play an important part in alleviating hunger and malnutrition in Nigeria, because they are among the basic requirements of balancing our diet. They have adequate nutritious supply and with characteristic taste. However, vegetable could serve as a source of toxic metals in human especially when planted in contaminated soils. The implications associated with metal contamination are of great concern. This study evaluated edible vegetable samples harvested from suspected contaminated soils located at: Iyana-Iba, Baruwa-pipeline, Isheri-Oshun and Idi-Araba. The plants and their corresponding soil samples were collected and acid-digested. The following parameters: Cu, Zn, Ni, Fe, Pb, Cd, and Cr were determined in the digested samples with Atomic Absorption Spectrophotometer.  The metals were found in the decreasing order of concentrations as follow: Iyana-Iba (Fe > Cr > Pb > Zn > Cu > Ni > Cd), Baruwa pipeline (Fe > Pb > Zn > Cr > Cu > Ni > Cd), Isheri-Oshun (Fe > Pb > Cr > Zn > Ni > Cu > Cd); Idi-Araba (Fe > Cr > Pb > Zn > Ni > Cu > Cd). Using enrichment factors, all the samples were severely enriched with Cd and Pb. The edible parts of vegetables also indicated higher concentrations of Cd (1.13-2.39 mg\kg), Cr (1.58-2.51 mg\kg) and Pb (14.15-43.05 mg\kg) than the WHO regulatory standards implying risk to the consumers. Sources of these metals were traceable to urban storm water, water irrigation and atmospheric deposition. This suggests that farmlands in Lagos should be regularly monitored.