Comparison of heavy metal content of selected vegetables grown with organic and inorganic fertilizers

Abstract

Background: Leafy vegetables are good sources of micronutrients but are also bio-accumulators of heavy metals. Objective: The study compared the heavy metal content of selected vegetables grown with organic and inorganic fertilizer in Odeda Local Government Area (LGA), Ogun State, Nigeria.

Methods: Celosia argentea, Telfairia occidentalis and Corchorus olitorius leaves were collected from four randomly selected farmlands. Soup recipes from a recipe book were standardized and used to prepare soups the samples. The vegetables and soups were analyzed in duplicate for lead (Pb), arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni) and zinc (Zn) using the atomic absorption spectrophotometer. Data obtained were analyzed using SPSS version 20.

Results: Arsenic, Pb and Cd were not detected in both Telfairia occidentalis and Corchorus olitorius samples, Similarly, As, Pb, Cr were not detected in the Celosia argentea and its soup. The Ni and Zn in the Corchorus olitorius samples ranged from 0.03mg - 0.6mg/100g and 0.22mg - 0.44mg/100g, respectively. There was not significantly (P > 0.05) different between the organic and inorganic and between the raw and cooked samples. The Ni in Telfairia occidental, ranged from 0.04mg - 0.06mg/100g, zinc from 0.34mg - 0.47mg/100g in both raw and soup samples. In Celosia argentea, Cd ranged from 0.09mg - 0.65mg/100g and was not significantly (P > 0.05) different between the organic and inorganic and between the raw and the cooked samples. Heavy metal in the samples did not exceed FAO/WHO limit for vegetables.

Conclusion: The heavy metal content of the organically grown vegetables was not significantly different from the inorganically grown.

Keywords: heavy metals; vegetables; organic, inorganic and fertilizers