Evaluation of Nitrate and Nitrite Contents of Vegetables and Soils from Irrigated Farmlands within Makurdi metropolis, Benue State, Nigeria

Abstract

Common vegetables (Amaranthus hybridus, Capsicum annuum, Telferia occidentalis, Talinum triangulare, Abelmoschus esculentus, Hibiscus sabdariffa,  Corchorus olitorius, and Ocimum basilicum) and soil samples were collected from irrigated farmlands along the bank of river Benue and analyzed for their  nitrate and nitrite contents using UV- spectrophotometer. This was aimed at assessing the level of contamination of these vegetables by these anions.  The results of the study indicate nitrates concentrations in the vegetables to range from 1829.54mg/kg to 5114.16mg/kg, while nitrite content of the  vegetables was also found to range from 459.80 mg/kg to 718.63 mg/kg. Soil nitrate ranged from 1882.13 mg/kg to 4004.20 mg/kg, while the nitrite  ranged from 244.20 mg/kg to 1232.70 mg/kg. Some of the vegetables were found to accumulate nitrate and nitrite contents higher than the permissible  limits prescribed by WHO/FAO. The higher content of nitrate and nitrites in these vegetables and soil could be attributed to excessive use of fertilizers,  animal manures, and other agro-chemicals as well as the wastewater used in irrigation. Both nitrate and nitrite transfer factors were above 0.5 which  implies that the vegetable have high tendency to accumulate the anions, therefore, continuous consumption of these vegetable could be detrimental to  health.