Assessment of chemical quality of three streams under different agricultural land systems in Obafemi Awolowo University Ile-Ife, Nigeria

Abstract

The chemical quality of streams under three agricultural land systems viz Agbogbo Amuta, and Abagbooro catchments was investigated with the aim of determining the physicochemical parameters of the streams and to understand nutrients loss and water pollution levels of the three different agricultural land systems. Mechanized farming is practiced in the Amuta catchment while peasant farming and tree cropping is practiced in Agbogbo and Abagbooro catchment areas, respectively. Stream water samples were collected and analyzed biweekly for a period of 12 months. Physicochemical parameters were determined using standard analytical techniques, while levels of trace metals – Zn, Cu, Co, Cd, Pb, Cr, and Ni were determined after nitric acid digestion using an Atomic Absorption Spectrophotometer (AAS). The pH of streams from the three catchment areas varied from slight acidity (6.10) to alkaline (8.60). The electrical conductivity (EC) ranged between 0.07 and 0.10 mS cm⁻¹, 0.02 and 0.07 mS cm⁻¹, and 0.03 and 0.06 mS cm⁻¹ for Amuta, Agbogbo, and Abagbooro catchments, respectively. The nutrients; (1.76 ± 0.41 mg L⁻¹), (0.19 ± 0.05 mg L⁻¹), (1.98 ± 1.07 mg L⁻¹), and (3.93 ± 1.30 mg L⁻¹) were highest in the Amuta stream and lowest in the Abagboro stream: (0.77 ± 0.34 mg L⁻¹), (0.14 ± 0.03 mg L⁻¹) (1.83 ± 1.03 mg L⁻¹), and (2.78 ± 1.23 mg L⁻¹). The mean concentrations of some trace metals: Mn (2.56 ± 0.25 mg L⁻¹), Fe (0.34 ± 0.10 mg L⁻¹), Co (0.10 ± 0.02 mg L⁻¹), and Cr (0.21 ± 0.18 mg L⁻¹) were highest in the Amuta catchment area, while the levels of cadmium and lead were not significantly different at p ≤ 0.05 in the three sampling areas. The study showed that nutrients loss and water pollution were highest in the stream from the Amuta catchment area compared to the Agbogbo and Abagdooro catchment areas. Levels of physicochemical parameters and some trace metals investigated in this study therefore depended on the type of agricultural inputs and practices in the three catchment areas.

Keywords:

• physicochemical
• trace metals
• pollution
• nutrient-loss