Spatial and Seasonal Concentration of Glyphosate, Nitrate, and Phosphate in Kuti Stream, Yaba, Abaji Area Council, FCT Abuja, Nigeria

Abstract

This study determines the concentration of glyphosate (C₃H₈NO₅P), nitrate (NO₃^-), and phosphate (PO₄^3-) in Kuti stream, Abaji area council, Federal Capital Territory Abuja, Nigeria, for twelve months (January-December, 2019) at four sampling stations that were 500 m apart. Samples were collected monthly during the morning hours (06.00-10.00 h) from a depth of 5–10 cm below the water surface using high-density polyethylene bottles and analyzed by adopting standard protocols. Samples analyzed for C₃H₈NO₅P concentration were pooled quarterly with the highest (0.27±0.01 mg/l) concentration observed in July-September at station 2, lowest (0.02±0.01mg/l) in January-March at station 4. Seasonal concentration differed significantly (P ≤ 0.05), rainy season had 0.12mg/l, dry season had 0.06 mg/l. NO₃ ^- and PO₄^3- had their highest concentration (1.82±0.01mg/l; 0.87±0.01mg/l) in June at station 2 and 1, lowest (0.23±0.06mg/l; 0.21±0.05mg/l) in January and December at station 4 and 3. Rainy season had high concentration (1.82±0.01mg/l; 0.87±0.01 mg/l) of NO₃^- and PO₄^3- compared to dry season (0.23±0.01 mg/l; 0.21±0.01mg/l). Pairwise correlation coefficients show a strong positive relationship (r=0.53/1.00) between PO₄^3- and C₃H₈NO₅P. The mean concentration of C₃H₈NO₅P, NO₃^- and PO₄^3- (0.09±0.01 mg/l; 0.59±0.04 mg/l; 0.37±0.02 mg/l) were below the maximum contamination limit (MCL) of 0.7 mg/l, 50 mg/l and 5.0 mg/l by USEPA, WHO and NERN. The high concentrations observed in the rainy season and station 2 were linked to runoff and riparian agriculture, though their mean concentrations were low if not monitored, will increase and become harmful to aquatic and human lives, therefore, conservation farming was suggested.