Evaluating the Concentration of Heavy Metals in Effluent Irrigated Vegetables

ABSTRACT

This study assessed the concentration of heavy metals in irrigated Amaranthus and Capsicum crops grown with effluent water from the Idu Industrial Area of the FCT. Samples of effluent water were collected from three different industries (Afrifab Steel Limited, National Institutes for Pharmaceutical Research (NIPRD), and Salco), while soils as well as the root, shoot, and edible parts (leaf and chili) of Amaranthus and Capsicum crops grown in effluent water-irrigated crops were collected during the wet and dry seasons. The samples were analysed for some heavy metals (As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn). The results were compared with the NESREA and FAO limits for metal concentration in effluent water, soil, and food crops, respectively. Findings from the study revealed, among others, that there is no significant difference in the concentration of heavy metals in the effluent water samples from the respective industries (p = 0.559 > 0.05 and 0.489 > 0.05), irrigated soil samples (p = 0.999 > 0.05 and 0.992 > 0.05), root, shoot, and leaf of the Amaranthus crop samples (p = 0.606 > 0.05 and 0.381 > 0.05), and the root, shoot, and chili of the capsicum crop samples (p = 0.925 > 0.05 and 0.393 > 0.05) irrespective of seasons. Similarly, the average concentration of heavy metals in the effluent water samples (p = 0.206 > 0.05 and 0.265 > 0.05) and irrigated soils (p = 0.789 > 0.05 and 0.334 > 0.05) were not statistically significant with the NESREA limit across seasons. Similarly, the Amaranthus leaf (p = 0.175 > 0.05 and 0.142 > 0.05) and chili (p = 0.242 > 0.145 and 0.145 > 0.05) samples were statistically indifferent to the FAO limit across seasons. The concentration of heavy metals in the soil showed a positive and significant relationship with that of the Amaranthus leaf (r = 0.9211, p-value 0.000 < 0.05) and Capsicum chili (r = 0.965, p-value 0.000 < 0.05). The study concluded that the accumulation of heavy metals in the soil is, in turn, the major pathway through which food crops can be contaminated. The study recommends, among others, that the direct application of industrial effluent water into farmlands for irrigation farming should be prohibited. Instead, all industrial effluent water should be collected at the Wupa Central Waste Treatment Plant for proper treatment in-line with the NESREA guidelines before being discharged into any agricultural field. This can be regulated by the Abuja Environmental Protection Board (AEPB) and the National Environmental Standards and Regulations Enforcement Agency (NESREA).

PRESENTED

 BY

ZAINAB ABUBAKAR IBRAHIM