Heavy Metals Bioaccumulation in Celosia argentea L. and Corchorus olitorius L. Grown on Refuse Disposal in Igabi Local Government Area, Kaduna State, Nigeria

Abstract

Leafy vegetable farmers nowadays in part of the country gathered manure from dumped sites for growing vegetables due to the nation's high cost for both organic and artificial fertilizers. However, because of this, this study was carried out to evaluate bioaccumulation of heavy metals in Celosia argentea L. and Corchorus olitorius L. grown on heavy metal-contaminated manure from refuse disposal, employing Igabi local Government Area of Kaduna State as a case study. Two (2) species of leafy vegetables Cockscomb (Celosia argentea L.) and Jews mallow (Corchorus olitorius L.) were grown on three different pots I, II and III replicated three (3) times respectively. (control soil, contaminated soil that was gathered from disposal locations, and a mix of control and contaminated soil). After being digested using the wet acid method, the collected vegetables were subjected to atomic absorption spectroscopy (AAS) for heavy metal. The mean ± standard deviation was used to express the results, and Duncan Multiple Range Test (DMRT) is used to separate the mean values. The findings were contrasted with recommendations from the Food and Agricultural Organization (FAO) and the World Health Organization (WHO). Results demonstrated that the leafy vegetables' accreted levels of (Cr) chromium (Cockscomb-1.36 + 0.062 mg/kg; Jews mallow - 1.10 + 0.050 mg/kg) and (Cd) cadmium (Cockscomb- 1.65 + 0.076 mg/kg; Jews mallow - 0.98 + 0.045 mg/kg) are beyond the WHO/FAO-permissible limits(Cr -1.3 mg/kg; Cd - 0.2 mg/kg).However,  Jews Mallow surpasses the allowable limit of 0.2 mg/kg in Cadmium (Cd) only, whereas Cockscomb has levels of Cadmium (Cd) and Chromium (Cr) that are higher than the permissible limits of 0.2 mg/kg and 1.3 mg/kg, respectively Accumulation order varies according to the species and soil's supply. Inconclusion, the two (2) Leafy vegetables (Corchorus olitorius L and Celosia argentea L) absorbs and accrues heavy metals above WHO/FAO permissible limit standard. In the two vegetables, the levels of cadmium (Cd) and chromium (Cr) is above the allowable limits respectively. When the two vegetables are compared, Celosia argentea L.( 6.66mg/kg) absorbs and accumulates greater heavy metals as opposed to Corchorus olitorius L.(4.18mg/kg) Therefore, it is recommended that farmers should be sensitized of the dangers of using soil from dumping sites or any other polluted soil for crop and vegetable cultivation, as well as the needs for appropriate pollution management.