Home
Add
Get on Google Play
Home
> Edit
Add/Update Thesis
Title*
Author's Name*
Supervisor's Name
Abstract
The fate of nine different pesticides (endosulfan, deltamethrin, imidacloprid, thiodicarb, triazophos, pyridaben, emamectin benzoate, fipronil and diafenthiuron) selected from individual classes was examined in three different soils at laboratory and field conditions. The findings suggested the various key mechanisms such as adsorption, leaching, dissipation and degradation which were responsible for interaction of pesticide with soil. Among these adsorption was one of the most important processes affecting the leaching of pesticides through soil because it controls the amount of pesticide available for transport. The evaluation of kinetic data was performed through pseudo first and second order models. It was found that kinetic adsorption of all pesticides except Endosulfan on soil followed pseudo first order with rate constant value ranged in 0.096-0.214/h, equilibrium concentration was found 38.177-77.678 mg/g and R2 value in a range of 0.988-0.997. Only kinetic adsorption of Endosulfan has followed pseudo second order kinetic model. To monitor the pseudo equilibrium achieved for selected pesticides the curve was plotted between pesticide residues adsorbed and time. The kinetic adsorption had shown two clear regions, initially a very rapid adsorption followed by a slow adsorption region. The rapid adsorption was surface phenomenon because the vacant sites in the soil particles were filled up rapidly in the preliminary region followed by a slow adsorption due to migration and diffusion of pesticide molecules in soil. The pseudo equilibrium time observed for pyridaben was 3 h, diafenthiuron 3.5 h, endosulfan, fipronil and deltamethrin 4 h each, emamectin benzoate 5 h, imidacloprid and triazophos 6 h, thiodicarb 10h. Equilibrium adsorption of selected nine pesticides was monitored with Langmuir and Freundlich models. It was investigated that all selected pesticides have followed Freundlich isotherm representing the reversible, non-ideal and multilayer adsorption over heterogeneous surface of soil. The Freundlich adsorption capacity (A), intensity (n) and R2 computed for all used pesticides were in a range of 1.053-2.813 mg/g, 0.249-0.892 and 0.996-0.999 respectively. Therefore the value of n obtained from Freundlich model was below 1, indicating chemisorption was taking place between pesticides and soil surface. In addition value of 1/n was greater than one showing co-operative adsorption was taking place with chemisorption mechanism. In laboratory, leaching study was performed in three plastic columns of 30 cm length, each for individual soil type. Known amount of each pesticide was applied to column, after adsorption it was eluted with 500 ml water in five portions. These water portions and soils were analyzed with concerned analytical technique. Generally the concentration of all pesticides was found to be decreased in column soil and water samples. In water samples it was observed as follow: α-Endosulfan 1.028-0.002, β-Endosulfan 1.015-0.003, triazophos 0.734-0.101, imidacloprid 0.481-0.103, thiodicarb 2.814-0.003, diafenthiuron 0.28-0.003, fipronil 0.032-0.002, emamectin benzoate 0.082-0.040, pyridaben 0.004-0.001, deltamethrin 0.073-0.001 ng/µl respectively. The decrease of pesticide residues in column soils were found as, α-Endosulfan 3.621-0.012, β-Endosulfan 2.968-0.012, triazophos 4.782-0.004, imidacloprid 2.905-0.123, thiodicarb 4.739-0.618, diafenthiuron 4.296-0.013, fipronil 4.791-1.107, emamectin benzoate 4.749-1.131, pyridaben 5.314-1.014 and deltamethrin 2.584-0.605 ng/mg. In field the leaching power of pesticides was examined up to 60 cm depth. Total four soil samples were randomly collected from each site, first three samples were taken at interval of 10 cm each and fourth sample was taken from 30-60 cm soil depth. The residue was found to decrease as we go down in soil. The pesticides Endosulfan, imidacloprid, thiodicarb and diafenthiuron were seen to leach 60 cm soil depth, triazophos moved 30 cm soil depth and deltamethrin, pyridaben, emamectin benzoate, fipronil were observed strongly adsorbed within 20 cm soil depth. The dissipation rate investigated for individual pesticide in three different soils was as under: α-Endosulfan 99 % over 60 d with average T1/2 of 8.395 d, β-Endosulfan above 91 % over 140 d with average T1/2 43.659 d, deltamethrin above 91 % over 30 d with average T1/2 16.577 d, imidacloprid above 88.413 % over 120 d with average T1/2 38.002 d, thiodicarb above 94.301 d over 35 d with average T1/2 8.372 d, triazophos above 90% over 30 d with average half-life of 9.059, pyridaben above 90 % over 12 d with average T1/2 3.786 d, emamectin benzoate above 87.035 % over 12 d with average T1/2 4.142 d, fipronil above 90 % over 150 d with average T1/245.755 d, diafenthiuron above 94 % over 15 d with average T1/2 4.343 d. From dissipation study it was inferred that rate was variable in each soil due to climatic changes, soil nature and soil-pesticide interactions. The % recoveries obtained for each of pesticide in soil were: α-Endosulfan 93.407-98.559, β-Endosulfan 89.216-97.279, deltamethrin 94.775-96.935, imidacloprid 88.698-95.694, thiodicarb 86.098-95.762, triazophos 92.093-98.516, pyridaben 90.885-95.116, emamectin benzoate 88.973-96.158, fipronil 95.769-99.030 and diafenthiuron 88.432-94.416 %. By applying GUS model triazophos, pyridaben, emamectin benzoate, fipronil, α-Endosulfan and deltamethrin were classified as non-leacher pesticides, while diafenthiuron, thiodicarb, β-Endosulfan and imidacloprid were categorized as leacher pesticides class.
Subject/Specialization
Language
Program
Faculty/Department's Name
Institute Name
Univeristy Type
Public
Private
Campus (if any)
Institute Affiliation Inforamtion (if any)
City where institute is located
Province
Country
Degree Starting Year
Degree Completion Year
Year of Viva Voce Exam
Thesis Completion Year
Thesis Status
Completed
Incomplete
Number of Pages
Urdu Keywords
English Keywords
Link
Select Category
Religious Studies
Social Sciences & Humanities
Science
Technology
Any other inforamtion you want to share such as Table of Contents, Conclusion.
Your email address*