Assessment of Heavy Metals in Waterleaf from Various Sources in Ota, Nigeria

Abstract

This study assessed the levels of heavy metals present in waterleaf (Talinum triangulare) from various sources in Ota, Ogun State. Eighty (80) samples of waterleaf were obtained from 5 domestic (non-hazardous) dumpsites, 5 non-dumpsites, 5 markets and 5 streets in Ota. The non-dumpsites were locations in industrial areas. Also, over 500 questionnaires were randomly administered to residents in Ota to assess the extent of consumption of waterleaf. Standard method was followed for sample treatment, digestion, and analysis of selected heavy metals: lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni) and cobalt (Co) using Atomic Absorption Spectrometer. The results showed that in waterleaf from domestic dumpsites the concentration (mg/kg) of heavy metals were: Pb (14.50-20.10), Cd (0.05-0.60), Cr (0.19-2.48), Ni (2.75-7.30) and Co (3.40-6.05); from non-dumpsites: Pb (12.20-24.45), Cd (ND- 0.60), Cr (ND-2.79), Ni (ND-24.00), Co (3.75-5.75); from markets: Pb (0.35-3.85), Cd (ND), Cr (ND-7.11), Ni (ND- 5.10), Co (1.05-2.45); and from streets: Pb (ND-5.00), Cd (ND), Cr (ND), Ni (3.50-7.25), Co (1.50-2.50). Generally, all the heavy metals were highest in waterleaf from domestic dumpsites and non-dumpsites. There were 502 respondents to the questionnaire; of which 82% consumed waterleaf. Out of those who consumed waterleaf, 41% consumed it daily, 32% at least once in a week, and 19% at least once in two weeks. It may be concluded that there is the high tendency of exposure to heavy metals by those who consume waterleaf in the studied locations since the levels in waterleaf from all sources studied generally exceeded the FAO/WHO limits.

Keywords: Waterleaf, Talinum triangulare, vegetable, heavy metals, pollution, Ota