Phytoremediation of Fosetyl-Aluminum and Spiroxamine from Floriculture Effluent Using Enhanced Azolla pinnata and Lemna minor (Duckweed): A Case Study of Equator Flower Farm, Eldoret, Kenya

Résumé

Floriculture represents a rapidly expanding sector in Kenya’s agricultural economy, but the heavy reliance on pesticides raises growing concerns about environmental pollution and public health risks. This study aimed to evaluate the phytoremediation potential of enhanced aquatic macrophytes, Azolla pinnata and Lemna minor (duckweed), in removing the systemic fungicides Fosetyl-Aluminum and Spiroxamine from floriculture effluent. The research sought to address the ecological threat posed by pesticide runoff from commercial flower farms to the Marura Wetland ecosystem in Eldoret, Kenya. A baseline spatial assessment of pesticide loading was conducted at Equator Flower Farm using HPLC analysis. To improve remediation efficiency, A. pinnata and L. minor were enhanced through colchicine-induced polyploidy (1–10 ppm) to increase biomass and surface area. Experimental trials were conducted in a greenhouse using a completely randomized design (CRD) across three batches. Pesticide concentrations in both the water column and plant tissues were quantified over 14 days to determine removal rates and bioaccumulation factors. Experimental data were analyzed using R (version 4.4.2) to assess pesticide spatial distribution and phytoremediation efficiency. One-way ANOVA was employed to identify significant differences in water-phase concentrations and tissue bioaccumulation across sampling points, treatment batches and plant species at p<0.05.  The study identified significant spatial variability in pesticide distribution at Equator Flower Farm, with a localized hotspot at Point 3 exhibiting concentrations of 6.07 mg/L for Fosetyl-Aluminum and 12.20 mg/L for Spiroxamine. The sequential pond system demonstrated high efficacy (p=0.001), achieving over 85% removal efficiency, although Spiroxamine showed greater environmental persistence than Fosetyl-Aluminum. Experimental results revealed that colchicine-induced polyploidy significantly enhanced the functional morphology of both macrophytes, doubling the shoot height and leaf area of A. pinnata. Consequently, enhanced Azolla outperformed L. minor (p<0.001), sequestering pesticides at rates two to three times higher than the latter, with tissue accumulation reaching 2.18±0.28 mg/kg for Spiroxamine. The study concludes that integrating colchicine-enhanced A. pinnata into sequential treatment systems provides a highly efficient and sustainable biotechnological solution for mitigating persistent floriculture pesticide runoff and protecting aquatic ecosystems. It is recommended that commercial floriculture operations integrate dual-species macrophyte ponds into their treatment chains. Regulatory bodies like NEMA should adopt these nature-based solutions into environmental policy, accompanied by systematic biomass harvesting to ensure the permanent removal of pollutants from the aquatic environment.