CHEMICAL CONTAMINATION AND NUTRIENT ACCUMULATION IN WASTEWATER-IRRIGATED VEGETABLES ALONG THE NGADDA RIVER, MAIDUGURI, NIGERIA
Ali Galadima , Ikusemoran Mayomi and Zainab Chellube
Volume 13 Issue 2
Abstract
This study examined the chemical composition and potential contamination of vegetables irrigated with wastewater along the Ngadda River in Maiduguri, northeastern Nigeria. A controlled field experiment was conducted using spinach (Spinacia oleracea) and okra (Abelmoschus esculentus) grown under two irrigation conditions: wastewater and freshwater. Four experimental plots were established, including two wastewater-irrigated plots and two freshwater control plots. At maturity, vegetable samples were harvested and analyzed for selected chemical constituents such as chloride (Cl⁻), sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), phosphate (PO₄³⁻), sulphate (SO₄²⁻), cadmium (Cd), chromium (Cr), and phosphorus (P) using atomic absorption spectrophotometry and UV–visible spectrophotometry. The results showed notable differences in nutrient accumulation between wastewater and freshwater-irrigated vegetables. Chloride concentrations ranged from 0.005 to 0.012 mg/kg, while sodium levels varied between 0.032 to 0.106 mg/kg, with wastewater irrigation increasing sodium in okra by about 63%. Potassium concentrations ranged from 0.052 to 0.114 mg/kg, but decreased by approximately 54% in wastewater-irrigated okra. Magnesium showed the greatest variation, increasing from 0.055 mg/kg to 0.413 mg/kg in wastewater-irrigated okra. Phosphate concentrations also increased under wastewater irrigation, particularly in okra (0.004 to 0.065 mg/kg). Sulphate levels showed only slight variation. Trace heavy metals were detected at very low levels. Cadmium was found only in wastewater-irrigated okra (0.001 mg/kg), while chromium was detected at 0.001 mg/kg in spinach and wastewater-irrigated okra. These values were below international safety limits. Overall, the study indicates that wastewater irrigation can enhance nutrient availability in vegetables but may also introduce trace contaminants, highlighting the need for continuous monitoring and improved wastewater management practices. Keywords: Wastewater Irrigation, Vegetable Contamination, Heavy Metals, Nutrient Accumulation
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