Effects of Selected Herbicides on Physicochemical Characteristics and Heavy Metal Concentrations in River Kaduna Water under Controlled Laboratory Conditions
DOI:
https://doi.org/10.67601/njbls.v3i2a.55Keywords:
Aquatic ecotoxicology, Environmental fate, Heavy metal mobilization, Herbicide runoff, Water quality degradation, River KadunaAbstract
Agricultural herbicide runoff poses severe ecological risks to tropical freshwater ecosystems. This study evaluated the comparative effects of low (1.0 mg/L) and high (10.0 mg/L) exposure concentrations of glyphosate, metolachlor, and 2,4-dichlorophenoxyacetic acid (2,4-D) on the physicochemical characteristics and heavy metal concentrations (Pb, Cd, and Zn) of River Kaduna water over a 6-week laboratory microcosm experiment. Water samples were monitored at weekly intervals for temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), nitrate (NO3-N), and phosphate (PO4-P). Herbicide treatments induced significant (p<0.05) alterations in water quality dynamics. Glyphosate at 10.0 mg/L produced the largest increases in EC (1955.3±2.1 μS/cm) and TDS (977.67±1.5 mg/L), alongside a reduction in DO to 2.0±0.1 mg/L compared to the control (3.5±0.1 mg/L). Metolachlor significantly elevated phosphate levels (0.91–0.92 mg/L). Across treatments, lead (Pb) and cadmium (Cd) concentrations exceeded World Health Organization drinking water thresholds, with peak Pb reaching 0.364±0.03 mg/L under 2,4-D treatment and peak Cd reaching 0.021±0.0 mg/L under metolachlor treatment. Conversely, zinc (Zn) remained well within safety standards (0.002–0.088 mg/L). These results indicate that herbicide contamination degrades basic water quality parameters and promotes heavy metal mobilization in tropical surface waters.
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