الفهرس 
Fate of Neoicotinoid Insecticides in different agri-Enviromental componentsOnly 14 pages are availabe for public view
 |  | from | 121 |  |  |
| | | from | 121 | | |
Abstract
It is very important to understand the fate and behaviour of pesticides in agri-enviroment to achieve the purpose of its using and avoiding its risk. Fate and behaviour of pesticides in soil, water and plant are determined by a combination of the dissipation, leaching and uptake processes. Also, an ideal insecticide should be toxic only to the target organism, biodegradable and undesirable residues should not affect non-target surfaces. Thus, it is very important to understand the fate of pesticides in soil and water. However, the information about the fate of pesticides under Egyptian conditions is poor. Therefore, the aim of the present work was to understand the fate of two insecticides; imidacloprid and acetamiprid in the tow common Egyptian soil types; clay loam soil and sandy loam soil. Consequently, the study included the dissipation of tested insecticides in soil and water using experimental and modeling systems with different affecting factors; soil type, temperature, sterilization, pH and salinity. Moreover, the leaching and uptake of acetamiprid and imidacloprid were investigated.
The major conclusions that can be drawn from the present study are that:
Dissipation in soil using UV
The recovery percentages of acetamiprid and imidacloprid extracted by acetonitrile:methanol (50:50) were ranged from 86.0 to 98.0 % form either clay or sandy soil. The dissipation of acetamiprid and imidacloprid at different time intervals up to 45 day. The residues of acetamiprid and imidacloprid were significantly decreased in non-sterile for both soil compared in sterile for both soil. The difference between t0.5 values in the case of non-sterilized and sterilized soil is great. Also, the difference between sterilized and non-sterilized in the case of sandy soil is more than that in the case of clay soil.
Dissipation in water using UV
The recovery percentages of acetamiprid and imidacloprid from water samples were 72.5 and 73.0%, respectively. The dissipation of acetamiprid and imidacloprid in modified pH water (5, 7 and 9) during 40 days was investigated. The dissipation of acetamiprid was rapidly in water at pH 9 than that in modified water to pH 7 and 5. While, the dissipation of imidacloprid throughout all time intervals was heigher in water at pH 5 that at pH 9 and 7. The shortest half-life of acetamiprid was obtained under alkaline condition (pH 9). While that of imidacloprid was recorded under acidic condition (pH 5).
Experimental dissipation in soil using HPLC
The mean values of recovery percentages of the tested insecticides from soil were 86 and 86.7% for acetamiprid and 75.2 and 71.2% for imidacloprid in clay and sandy soil, respectively. The insecticide residues were detected in all samples at 1, 5, 8, 15, 21, 32, 60 day. The dissipation of acetamiprid and imidacloprid were more in treatment of non-sterilization compared to sterilized. In similar, the dissipation rate was more in samples under 50°C than to that under 25°C for both soil types.
The t0.5 values of acetamiprid and imidacloprid in soil were calculated from equation (t0.5=0.6932/k). It can be noted that the sandy soil which incubated at 50°C and non-sterilized led to dissipation of acetamiprid rapidly than the other treatments. The incubation under high temperature (50°C) enhanced while the sterilization reduced the dissipation of tested insecticides.