Deltamethrin degradation and effects on soil microbial activity

Abstract

Deltamethrin [(S)-cyano-3-phenoxybenzyl-cis-(1R,3R)-2,2-dimethyl) cyclo-propane carboxylate),1] labelled at gem-dimethyl groups of the cyclopropane ring was applied on two Egyptian soils at a level of 10 mg/kg soil for a laboratory incubation experiment under aerobic and anaerobic conditions. A steady decrease of soil extractable ¹⁴C-residues, accompanied by a corresponding increase of non- extractable bound ¹⁴C-residues was observed over a 90-day incubation period. The percentage of evolved ¹⁴CO₂ increased with time under aerobic and anaerobic conditions in both soils. The effect of deltamethrin on soil microorganisms as well as the counter effect of microorganisms on the insecticide was also investigated. As the incubation period increased, the inhibitory effect of the insecticide on the microorganisms decreased and the evolution of carbon dioxide depended on the applied dose. The nature of soil methanol soluble residues was determined by chromatographic analysis which revealed the presence of the parent insecticide as the main product in addition to four metabolites: 3-(2',2'-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (II); 3-phenoxybenzaldehyde (III); 3-phenoxybenzoic acid (IV); 3-phenoxybenzyl alcohol (V).

Long-term toxic effects of deltamethrin and fenvalerante in soil

“…A toxic metabolite of the deltamethrin 4 -OH-deltamethrin could induce the cytotoxicity significantly, and its toxicity was 200 times higher than the parental compound [38]. The rising cytotoxicity of deltamethrin and fenvalerate on worms after long term exposure might be due to the formation of toxic metabolites because the concentration of deltamethrin and fenvalerate in soil decreased rapidly in the process of degradation by microorganism (P < 0.05) [Fig 1], the major dissipation mechanism and loss route for synthetic pyrethroids in soil [39,40]. So the toxic effect of deltamethrin and fenvalerate did not match with the degradation trend of these pyrethroids [Tables [1][2][3][4][5].…”

Biodegradation potential of aquaculture chemotherapeutants in marine sediments

“…Both EB and deltamethrin have moderate to low water solubility (5–24 mg L −1 for EB (Bright & Dionne ) and <2 μg L −1 for deltamethrin (Tomlin )) and relatively high octanol‐water and sediment‐water partition coefficients (log K ow ~5 for both substances; Tomlin () and Bright & Dionne (); K p = 21.81 for EB; Veldhoen et al ., ), indicating their potential to partition to sediments, where they are expected to undergo biodegradation by sediment microbes (Guo, Wang, Hang, Li, Ali, He & Li ). However, the rates under which this may occur are dependent on a number of factors, including temperature, light, pH, organic matter, moisture, aerobic or anaerobic conditions (Farghaly, Zayed & Soliman ), which has lead to a wide range of degradation half‐life estimates for these substances (79–427 days for EB; Scottish Environmental Protection Agency (SEPA) () and Schering Plough Animal Health (2002) and 5.7–209 days for deltamethrin; Hayes (); Farghaly et al . () and Meyer, Lam, Moore & Jones ()).…”

Measurement of Aquaculture Chemotherapeutants in Flocculent Matter Collected at a Hard-Bottom Dominated Finfish Site on the South Coast of Newfoundland (Canada) After 2 Years of Fallow

“…Abiotic processes are predominant under reducing conditions (Tribovillard et al, 2006); these processes may lead to the depletion or formation of complexes, and the precipitation of sulfides and/or insoluble oxyhydroxides (Tribovillard et al, 2006). While deltamethrin degradation can occur through microbial action as well as hydrolysis and photolysis (Farghaly et al, 2013;Meyer et al, 2013), it may degrade less rapidly once adsorbed to OM-rich sediments (similarly to cypermethrin) (Benskin et al, 2016). The sorption of pyrethroids to flocculent matter is also highlighted by the observed correlation between pyrethroids and both OM content and distance to cage.…”

“…In sediments, chemotherapeutants may undergo chemically or biologically-mediated transformation, but coexposure to pesticides, antibiotics and/or trace metals used in aquaculture may hinder their bacterial transformation leading to increased persistence in sediments (Benskin et al, 2016). For parasiticides such as pyrethroids (and likely other compounds as well), degradation rates depend on several factors, including temperature, light, pH, organic matter (OM) content, and oxygen availability (Farghaly et al, 2013), which affect the half-life of these substances (Benskin et al, 2016). Research on the accumulation and degradation of chemotherapeutants in sediments around aquaculture sites is needed to evaluate dissipation rates (Benskin et al, 2016) and assess the potential for adverse effects to benthic invertebrates (Van Geest et al, 2014).…”