Abstract

• Phytoremediation is an eco-friendly treatment for reducing soil contamination. Cypermethrin is one of the most widely used pyrethroid insecticides against different pests, and its use causes soil contamination. A field study was conducted in cypermethrin contaminated soil to detect and monitor the changes in soil nutrients, enzyme activities, and 3-phenoxy benzoic acid (3-PBA, primary metabolite of cypermethrin insecticide). Phytoremediation was undertaken using two plant species: aster (Callistephus chinensis L. Nees) and Bermuda grass (Cynodon dactylon L. Pers.) in the absence and presence of iron oxide particles (0.01 g/kg of soil). Soil pH, soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), and available potassium (K2O) and relative metals content by EDXRF. The activities of soil urease (mg NH4+-N g-1 soil h-1) and dehydrogenase (µg TPF g-1 soil h-1) also increased in the treated soil samples as determined by the phenolhypochlorite colourimetric method and the Triphenyl Tetrazolium Chloride (TTC) assay method. The urease enzyme activities of aster (5.363 ± 0.024) and Bermuda grass (4.816 ± 0.07) was found to be higher when compared with uncultivated soil (S0) (3.74 ± 0.03), whereas the dehydrogenase activity of aster (0.00127 ± 0.0000) and Bermuda grass (0.00113 ± 0.0000) was also increased when compared with S0 (0.0008 ± 0.0000) in the field experiment. Furthermore, the insecticide residue in the soil samples was determined by UV-Vis and GC-MS. The results showed the decrease in insecticide residue decrease in during phytoremediation in the presence of iron oxide particles. Phytoremediation demonstrated 96.33 % and 94.19 % PBA decrease using aster and Bermuda grass in 12 weeks period. The results demonstrated that aster and Bermuda grass showed promising potential for use as phytoremediating agents in insecticide contaminated soil.