Comparsion study of the residual behaviour and kinetics of insecticide fenitrothion and herbicide thiobencarb in clay soil were carried out under laboratory conditions. The residues of the tested pesticides were determined by GC-MS at different interval times (0, 2, 5, 13, 20, 27, 48, 55 and 84 day) after treatment. The recoveries were performed at level of 75 μg/g soil and the recovery percentages were found to be 85.69 and 90.89 for fenitrothion and thiobencarb in the tested soil, respectively. The residue of fenitrothion was 64.27 µg/soil, after 48 days of incubation and the dropped to 5.07 % of the initial residue remaining. Thiobencarb residues level recorded after treated soil with 75 μg a.i / g soil wes 68.17 μg/g soil. This concentration gradually decreased with the time and reached to 0.68 μg/g soil at 55 days after treatment. Both compounds fenitrothion and thiobencarb disappeared very rapidly in the soil following a bi-phasic pattern. Graphical and integral methods were used to select the fit kinetic model. The determination coefficient R 2 was the highest and the SD of K values were the lowest in 1st order model compared to other kinetic models. Therefor, the dissipation of fenitrothion and thiobencarb in soil fits with the 1st-order kinetic model. The estimated value of fenitrothion half-life was 11.21 days and that of thiobencarb was 10.61 days. In general, the dissipation of thiobencarb was slightly faster in the tested soil than fenitrothion.

BACKGROUND: Terrestrial snails are one of the most damaging threats to sustainable agriculture. Chemical control using molluscicides is the main approach used to combat these agricultural pests. Metaldehyde is the active ingredient in most snail control products in use. However, its toxicity indices and mode of action have scarcely been investigated. For the first time, we characterized the metaldehyde contact toxicity indices against the white garden snail Theba pisana. The biochemical impact of metaldehyde on acetylcholinesterase (AChE), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), alkaline phosphatase (ALP) and glutathione S-transferase (GST) activities and the lipid peroxidation (LPO) level was investigated.

The degradation process of pesticides is one of the mechanisms for losing sush chemical from the soil after application. The persistence, degradation kinetics and half-lives of fenitrothion (insecticide) and thiobencarb (herbicide) in the new reclaimed calcareous soil in Egypt were studied under laboratory conditions. The recovery percentages of fenitrothion and thiobencarb were 89.67 and 88.34%, respectively. The results of degradation kinetics showed that residues of fenitrothion and thiobencarb were rapidly decreased during the first five days after treatment. Residues of fenitrothion and thiobencarb remained on the second day were 72.45% and 57.63%, while on the fifth day were 37.72 and 47.18%, respectively. Both tested pesticides disappeared very rapidly from the soil following a bi-phasic pattern. According to the graphical and integral methods, the fit model to describe the degradation kinetic of fenitrothion and thiobencarb is the first order model. The rate constant (k) values for degradation of the two pesticides were 0.036 and 0.068 for fenitrothion and thiobencarb, respectively. The estimated values of half-life were 19.36 days for fenitrothion and 10.24 days for thiobencarb. In general, thiobencarb degraded in sandy clay loam soil about twice faster than fenitrothion.

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This study investigated the removal of imidacloprid (IMI) and oxamyl (OX) pesticides by cement kiln dust (CKD) as industrial by-products. CKD was identified by elements composition, Fourier-transform infrared (FTIR), and scanning electron microscopy (SEM). Effects of initial concentration (100-2000 mg/L), and contact time (10-360 min) were investigated. The kinetic results of IMI and OX pesticides were fitted to pseudo-first-order, pseudo-secondorder, and intra-particle diffusion equations. The pseudosecond-order kinetic model fitted well for IMI removal, while pseudo-first-order kinetic model flitted to OX removal results. Isotherm results were examined by different isotherm models (Freundlich, Langmuir, and Temkin equations). The results fitted well with the Langmuir isotherm model (R 2 =0.988 and 0.999) with maximum adsorption capacity of 142.85 and 100.00 mg/g for IMI and OX pesticide removal by CKD, respectively. The obtained results indicated the potential of using CKD as an efficient and, low-cost adsorbent for the removal of IMI and OX pesticides from aqueous solutions.