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Cotton has been one of the success stories of Pakistan rural industries. However this growth has had environmental effects including the movement of agricultural chemicals to groundwater and surface water. In Pakistan there is little data on environmental contamination of rural water sources by pesticides. The objective of this study is to present the soil and well sampling methodologies that have been developed to support the regulatory activities for detected pesticides, to indicate the range in pesticide active ingredients and their breakdown products detected in groundwater. and to discuss how the data have been used to provide a scientific approach for the further development of the groundwater regulatory program. These studies provide further understanding of the agronomic, chemical, and geographic factors that contribute to movement of residues to groundwater. The 1st part of the study evaluated pesticide contamination of groundwater in four intensive cotton growing districts. Water samples were collected from 37 rural open wells in the areas of Bahwalnagar, Muzafargarh, D. G. Khan and Rajan Pur districts of Punjab and analyzed for eight pesticides which are mostly used. Information on types of pesticide used and distance to nearest pesticide mixing area and application areas was obtained for each site. From the eight pesticides analysed, six pesticides were detected in the water samples. Only cypermethrin and cabosulfan were not detected. The percentage of detection of bifenthrin, λ-cyhalothrin, carbofuran, endosulfan. methyl parathion and monocrotophos was, respectively 13.5%, 5.4%. 59.4%, 8%. 5.4%. and 35.1 % in July; . 16.2%,13.5%, 43.2%, 8%, N.D. (not detected) and 24.3% in October. Maximum contamination levels (MCLs) established by the U.S. Environmental Protection Agency for drinking water were not exceeded. The study has shown the need for monitoring pesticide contamination in rural water resources, and the development of drinking water quality standards for specific pesticides in Pakistan. The conclusions and recommendations will be disseminated to senior decision makers in central and local governments, extension agents and farmers. The 2nd part of the study was conducted to examine adsorption of pesticides ,bifenthrin, carbosulfan ,λ-cyhalothrin, cypermethrin, endosulfan, parathion methyl, monocrotophos and 4-nitrophenol by sandy clay loam (S.C.L) and sandy loam (S.L) soils , (with varying organic content). There was no significant difference between the observed soil water partitioning coefficient values (Kd) derived from linear and nonlinear Freundlich isotherms. Adsorption of pesticides on S.C.L soils was higher than those on S.L soils. Kd values showed significant correlations (r2= 0.8-0.99 and 0.65-0.97) with soil organic carbon content (OC) and weak correlations (r2= 0.2-0.29 and 0.1-0.18) with clay contents of S.C.L and S.L soil at p≤0.05, respectively for all pesticides (except monocrotophos). Observed Koc values (soil-water partitioning constants based on the organic C fraction of the soil) were in accordance with the literature values of Wauchope and Tomlin with a maximum deviation of less than 0.5 log units. Ten Quantitative Property-Property Relationships (QPPR) among water solubility, n-octanol water coefficient (Kow) and Koc were proposed for studied pesticides except monocrotophos. The models were considered acceptable when predicted-observed difference for log Kow and log Koc were ≤0.3 and ≤0.5 log units. respectively, during the validation procedure. This work indicates that the log Koc derived from the log Koc, from some of existing relationships, may be a fair predictor where observed values (i.e., Kd and Koc) are not available. Furthermore, predicted leaching potential by groundwater ubiquity scores (GUS) equation was solved by using observed Koc values and literature reported half lives of pesticides. GUS ranked the mobility of nonvolatile compounds i.e., bifenthrin, λ-cyhalothrin, cypermethrin and endosulfan extremely low; methyl parathion very low; 4-nitrophenol low; carbofuran and monocrotophos very high in S.C.L and S.L soils, respectively. Results discussed in this part provide background to prioritize pesticides or chemical groups that should be evaluated under field conditions with regard to their leaching potential to groundwater in arid climates. The 3rd part of study evaluated the influence of temperature, moisture, and microbial activity on the degradation and persistence of mostly used cotton pesticides i.e., carbosulfan, carbofuran, endsosulfan and monocrotophos with the help of laboratory incubation and lysimeter studies on sandy loam soil (Typic Ustocurepts) in Pakistan. Drainage from Lysimeters were sampled at 49. 52. 59, 73. 100. 113 and 119 days against the pesticide application at 37, 63, 82, 108, and 137 days after sowing of cotton. Carbofuran, monocrotophos and nitrate were detected in drainage samples having average value of2.34 μg/L, 2.6 μg/L and 15.6 mg/L for no-tillage and 2.l6 μg/L, 2.3 μg/L and 13.4 mg/L for tillage, respectively. In the laboratory. pesticides disappearance kinetics were measured with sterile and non-sterile soils from 0-10 cm depth at different temperatures (15, 25 and 35°C) and 50 and 90 % field water capacities (FWC). Monocrotophos and carbosulfan observed dissipation kinetics by first-order rate law while other with second order rate kinetics. The results of incubation studies showed that temperature and moisture contents significantly reduced the T1/2 (half life) values of pesticides in sterile and non-sterile soil but the effect of microbial activity is almost significant that may be due to less organic carbon (0.3 %). The presence of carbofuran and monocrotophos in soil profile (0-10, 10-30, 30-60, 60-90, 90-150 cm) and higher concentration of endosulfan and cyhalothrin in top layer (0-10 cm) showed the persistence of the pesticides. Moreover the detection of endosulfan and cyhalothrin in 10-30 cm soil layer may be due to preferential flow. The data generated from this study may be helpful for risk assessment studies for pesticides and to validate pesticide transport models for cotton growing areas of Pakistan for sandy loam soils

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: leaching, cotton pesticides, pesticides poisoning, lysimeters, soil ground water system, salorthids, camborthids
Subjects: Q Science > QD Chemistry
Depositing User: Muhammad Khan Khan
Date Deposited: 28 Oct 2016 04:12
Last Modified: 28 Oct 2016 04:12
URI: http://eprints.hec.gov.pk/id/eprint/2919

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