Ecological risk assessment of pesticide residues in diverse farming landscapes of central Zambia
Agricultural intensification in Zambia has led to widespread reliance on pesticides to safeguard crop yields, yet concerns about their ecological consequences remain insufficiently addressed. This study helps to fill this gap by evaluating the extent and ecological risks associated with pesticide contamination in soils from Chibombo and Mkushi Districts in Central Zambia. We used a two-stage nested research design. First, locations (districts) contained different farming systems (commercial, emergent, and smallholder). Within each farming system, we measured and compared the levels of various pesticide residues, followed by ecological risk assessments (single pollution index and comprehensive pollution index). Pesticide residues were extracted using a modified QuEChERS method and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-tandem mass spectrometry (GC-MS/MS). The analysis of pesticide residues indicated that there were significant variations between farming systems in several pesticide residues (acetamiprid, chlorpyriphos, cypermethrin and profenofos). However, there were no significant differences in pesticide residue accumulation between districts. Smallholder farms were generally associated with high insecticide residues (especially chlorpyrifos with a range of 1,494–5,961 μg/kg), emergent farms showed elevated levels of both insecticides and herbicides (notably cypermethrin and fomesafen), while commercial farms were dominated by herbicide residues (acifluorfen, fomesafen, glyphosate and its primary metabolite; aminomethylphosphonic acid). Ecological risk indices indicated significant threats to soil microbial communities, underscoring the potential for long-term disruption of ecosystem services. The data highlights chlorpyrifos and cypermethrin as key pollutants of concern. The study concludes that current pesticide management practices in Central Province pose measurable ecological risks, necessitating urgent policy interventions and adoption of sustainable pest management strategies.