Study on treatment of pesticides-containing wastewater by model combining of the pre-biotreatment and photocatalytic TiO2

In the current period, with the development of economy, science, and technology, people's lives have been improved, leading to increasing demand for water use. Thus, one of the main current concerns is the increased pollution of surface water and groundwater. Especially water pollution by pesticides is a serious problem. In this study, the wastewater treated system, which is including the aerobic biological process and photocatalytic TiO2, used to evaluate the effective treatment of pesticides. Self-generated wastewater was added by a group mixed 8 types of Organochlorine pesticides (OCPs): Tetrachloro-m-xylene,b -HCH,d - HCH, Heptachlor – epoxide, 4,4'- DDE,b -Endosulfan, Endrin – aldehyde, Endosulfan – sulfate and 5 types of Organophosphate pesticides (OPPs): Diazinon, Malathion, Parathion, Ethion, Trithion. The results showed that the COD removal efficiency was over 89,09% for the whole system when maintaining the load of 0,78 kgCOD/m3. day, total retention time was 16 hours. Five types of OPPs was thoroughly treated after going through the system based on its easily biodegradable. For OCPs, the treatment efficiency through the biological process is not high, 6/8 types about 5 - 27% but through photocatalytic TiO2/UV, the treatment efficiency increased 67 - 100% for each type. The results obtained in the study show that the use of the method of combining biology and AOPs is effective for wastewater difficult to treat as pesticides.

Exploring the Environmental Exposure to Methoxychlor, α-HCH and Endosulfan–sulfate Residues in Lake Naivasha (Kenya) Using a Multimedia Fate Modeling Approach

Distribution of pesticide residues in the environment and their transport to surface water bodies is one of the most important environmental challenges. Fate of pesticides in the complex environments, especially in aquatic phases such as lakes and rivers, is governed by the main properties of the contaminants and the environmental properties. In this study, a multimedia mass modeling approach using the Quantitative Water Air Sediment Interaction (QWASI) model was applied to explore the fate of organochlorine pesticide residues of methoxychlor, α-HCH and endosulfan–sulfate in the lake Naivasha (Kenya). The required physicochemical data of the pesticides such as molar mass, vapor pressure, air–water partitioning coefficient (KAW), solubility, and the Henry’s law constant were provided as the inputs of the model. The environment data also were collected using field measurements and taken from the literature. The sensitivity analysis of the model was applied using One At a Time (OAT) approach and calibrated using measured pesticide residues by passive sampling method. Finally, the calibrated model was used to estimate the fate and distribution of the pesticide residues in different media of the lake. The result of sensitivity analysis showed that the five most sensitive parameters were KOC, logKow, half-life of the pollutants in water, half-life of the pollutants in sediment, and KAW. The variations of outputs for the three studied pesticide residues against inputs were noticeably different. For example, the range of changes in the concentration of α-HCH residue was between 96% to 102%, while for methoxychlor and endosulfan-sulfate it was between 65% to 125%. The results of calibration demonstrated that the model was calibrated reasonably with the R2 of 0.65 and RMSE of 16.4. It was found that methoxychlor had a mass fraction of almost 70% in water column and almost 30% of mass fraction in the sediment. In contrast, endosulfan–sulfate had highest most fraction in the water column (>99%) and just a negligible percentage in the sediment compartment. α-HCH also had the same situation like endosulfan–sulfate (e.g., 99% and 1% in water and sediment, respectively). Finally, it was concluded that the application of QWASI in combination with passive sampling technique allowed an insight to the fate process of the studied OCPs and helped actual concentration predictions. Therefore, the results of this study can also be used to perform risk assessment and investigate the environmental exposure of pesticide residues.

X-ray crystal structure of endosulfan sulfate

X-ray crystallography is an important method used to confirm the three-dimensional structure of a chemical compound. In this study, the crystal structure of endosulfan sulfate was investigated. Endosulfan sulfate is the major metabolite of the insecticide endosulfan, which is composed of two stereoisomers (α and β). From GC–MS analysis, α- and β-endosulfan each gave a single peak in the endosulfan sample, but only one peak was observed for endosulfan sulfate. Interestingly, in X-ray crystallography, two conformers of endosulfan sulfate (A and B) were observed at a ratio of 2(A):1(B). A heterocyclic seven-membered ring of conformer B assumed a horizontal-chair form, differing from two twisted forms of α-endosulfan while a vertical-chair form was observed for conformer A, showing the very similar structure to β-endosulfan; this difference in conformation is caused by differing bond angles at O(1)–C(8)–C(3) and O(2)–C(9)–C(4). In space packing, two asymmetric units were obtained, and three molecules were aligned in the order of A–A–B conformers in each unit. The total potential energy of A was slightly lower (approximately 4 kcal/mol) than B, possibly resulting in the two molecules of A that exist in a rigid crystal state. However, A and B conformers should not exist at room temperature in a solution state for GC–MS analysis, likely due to the small energy difference.

Monitoring of Organochlorine Pesticides Residues in Five Fruits using Gas Liquid Chromatography Equipped with Electron Capture Detector (GLC-ECD)

India is the largest producer of fruits as they are important part of their economy. But they are badly affected by insect-pest attack during harvesting. Farmers use a large amount of pesticides to protect them but due to their longer persistence they found in fruits in small quantities. This paper described an analytical methodology for the monitoring of 20 organochlorine pesticides in 5 fruits viz. pineapple (Ananas comosus), apple (Malus pumila), plum (Prunus domestica), papaya (Carica papaya) and mango (Mangifera indica) by using gas liquid chromatography equipped with electron capture detector (GLC-ECD). During the monitoring work it has been found that each fruit was contaminated with pesticides. Pineapple was found contaminated with β-BHC, δ-BHC, heptachlor epoxide, dieldrin, endrin and methoxychlor; apple was found contaminated γ-BHC, δ-BHC, heptachlor epoxide, dieldrin, endrin, endosulfan II and methoxychlor; plum and papaya were found contaminated with γ-BHC, β-BHC, δ-BHC, heptachlor epoxide, 4,4′-DDE, endrin, endosulfan sulfate and methoxychlor; mango was found contaminated with β-BHC, δ-BHC, 4,4′-DDE, endrin, endosulfan sulfate and methoxychlor. However, the detected concentration of pesticides was below the MRL values but their long term use can cause serious health problems.