ASSESSMENT OF HEAVY METALS IN OKRA (Abelmoschus esculentus) CULTIVATED THROUGH IRRIGATION, IN MAIDUGURI, NIGERIA

Abstract

The contamination of the environment with heavy metals is one of the challenges that constitute Nigeria’s environmental problem with urbanization being one of the major causes; due to the unavailability of proper waste dumpsites and landfills for infrastructural development thereby resulting in the polluting rivers and streams. The cultivation of vegetables along channels and rivers that transcend major cities have been a source of concern globally in recent decades due to accumulation of heavy metals and introduction of heavy metals into the food chain. This study therefore assessed the level of concentration of heavy metals namely; Aluminum, Iron, Lanthanum, Manganese, Chromium, Rubidium, Antimony, Scandium, Barium, Samarium and Zinc in Okra (Abelmoschus esclentus) samples obtained on farmlands along the bank of river Ngadda and Alau dam cultivated through irrigation. The samples were analyzed using instrumental neutron activation analysis (INAA) analytical technique with the aim of assessing their level of accumulation with heavy metals. The objective was to ascertain the food safety status of the vegetable by comparing the values obtained with maximum permissible limit (MPL) recommended by FAO/WHO for vegetables. The study results show that the concentration levels ranged from below detection limit (BDL) for Aluminum, Chromium, and Antimony (843 ± 16 ppm, 1.3 ± 0.2 ppm and 0.26 ± 0.03 ppm respectively) to Barium (7 ± 1.0 to 12 ± 1.0 ppm, Iron 11 ± 0.4 to 303 ± 36 ppm), Lanthanum (0.203± 0.03 to 1.93± 0.05 ppm), Manganese (22.9 ± 0.2 to 40.2 ± 0.2 ppm), Rubidium (7 ± 1 to 13± 1 ppm), Scandium (0.02± 0.00 to 0.05 ± 0.01 ppm), Samarium (0.02 ± 0 to 0.24± 0.01ppm), and Zinc (8± 1.0 to 24±0.1 ppm). This result also indicates that the maximum concentration value of Manganese exceeds the 25.95 ppm value of MPL recommended by FAO/WHO for vegetables therefore the consumption of Okra (Abelmoschus esclentus) cultivated from the study site has a potential health risk due to the presence of Manganese above recommended value.