Treatment of Dimethoate Aqueous Solution by Using Ultrasonic Airlift Loop Reactor

Ultrasonic airlift loop reactor （UALR） shows potential and wide application for wastewater treatment. In this paper the performance and efficiency of UALR in dimethoate degradation were presented. The effects of O3 flow rate, ultrasonic intensity and initial concentration of dimethoate on degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O3 transfer rate. The results showed that UALR not only increased degradation rate, but also was better than the simole sum of degradation by O3 and ultrasound separately. Under the operation conditions of O3 flow of 0.34 m^3·h^-1, ultrasonic intensity 3.71 W.cm^-2, and initial concentration of dimethoate at 20 mg·L^- 1, the degradation rate of dimethoate increased to 80%. UALR seems an advisable choice for treating organic wastewater and this process may have wide application prospect in industry.

Dimethoate Induced Oxidative Damage and Histopathological Changes in lung of Adult rats:Modulatory Effects of Selenium and/or Vitamin E

Objective To determine the efficiency of selenium and/or vitamin E to alleviate lung oxidative damage induced by dimethoate, an organophosphorus compound. Methods Adult Wistar rats were exposed during 30 days either to dimethoate （0.2 g/L of drinking water）, dimethoate＋selenium （0.5 mg/kg of diet）, dimethoate＋vitamin E （100 mg/kg of diet）, or dimethoate＋selenium＋vitamin E. Results Exposure to dimethoate caused oxidative stress in lung evidenced by an increase of malondialdehyde, protein carbonyl groups and advanced oxidation protein products. An increase in glutathione peroxidase, superoxide dismutase, catalase and a decrease in acetylcholinesterase and butyrylcholinesterase activities, glutathione, non-protein thiols and vitamins C levels were observed. Histopathological changes in lung tissue were noted as emphysema, hemorrhages and hemosiderin deposits. Co-administration of selenium or vitamin E to the diet of dimethoate treated rats ameliorated the biochemical parameters as well as histological impairments. The joint effect of these elements was more powerful in antagonizing dimethoate-induced lung oxidative damage. Conclusion We concluded that selenium and vitamin E ameliorated the toxic effects of this pesticide in lung tissue suggesting their role as potential antioxidants.

Distribution Behaviour of Dimethoate in Tea Leaf

A study was undertaken to assess the distribution behaviour of Dimethoate in tea leaf. Tea bushes were subjected to Dimethoate spray at recommended dose and double the recommended doses. The extraction of pesticide was done using chloroform and the analysis was done using a Hewlett-Packard 5890 series II gas chromatograph with Nitrogen Phosphorus Detector (NPD). The penetration behaviour of Dimethoate was studied in dry and wet seasons. Variations in penetration were observed in dry and wet seasons which was attributed to climatic factors like temperature, humidity, rainfall, sunlight and physicochemical properties of the residue like water solubility, partition coefficient and formulation type. Residues observed in the cell wall and tissues confirm its good penetrating ability inspite of its hydrophilic nature. Higher penetration in wet season as indicated can be attributed to the route through the stomatal pores.

Selective extraction of dimethoate from cucumber samples by use of molecularly imprinted microspheres

Molecularly imprinted polymers for dimethoate recognition were synthesized by the precipitation polymerization technique using methyl methacrylate （MMA） as the functional monomer and ethylene glycol dimethacrylate （EGDMA） as the cross-linker. The morphology, adsorption and recognition properties were investigated by scanning electron microscopy （SEM）, static adsorption test, and competitive adsorption test. To obtain the best selectivity and binding performance, the synthesis and adsorption conditions of MIPs were optimized through single factor experiments. Under the optimized conditions, the resultant polymers exhibited uniform size, satisfactory binding capacity and significant selectivity. Furthermore, the imprinted polymers were successfully applied as a specific solid-phase extractants combined with high performance liquid chromatography （HPLC） for determination of dimethoate residues in the cucumber samples. The average recoveries of three spiked samples ranged from 78.5% to 87.9% with the relative standard deviations （RSDs） less than 4.4% and the limit of detection （LOD） obtained for dimethoate as low as 2.3 μg/mL.

Biochemical Characterization of Detoxifying Enzymes in Dimethoate-Resistant Strains of Melon Aphid, Aphis gossypii(Hemiptera: Aphididae)

The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that are persistently and non-persistently transmitted. In nature, aphids are regulated by their natural enemies. However, chemical control remains a major management tool even though resistance to insecticides has been documented worldwide. A better understanding of mechanisms by which insecticide resistance occurs and its early detection is desirable to develop effective management strategies. The present investigation was conducted to study the development of resistance to an organophosphate (OP) compound-dimethoate, identify biochemical mechanism(s) involved in resistance and study cross-resistance to imidacloprid in laboratory selected A. gossypii strains in comparison to susceptible strains. Bioassay studies revealed that the LC50 values increased dramatically with dimethoate selection in resistant strains and the resistance ratio (RR) was 270-, 243- and 210-fold greater than that of the susceptible strains by 30th generation. Further, biochemical assays revealed enhanced activities of carboxylesterases (CarE), glutathione S-transferases (GSTs) and cytochrome P450-mediated p-Nitroanisole O-demethylase (PNOD) in resistant strains supporting their role in dimethoate detoxification. This study thus revealed that enhanced activity of detoxifying enzymes viz., CarE, GSTs and PNODs is one of the mechanisms underlying dimethoate resistance in A. gossypii collected from South India. Interestingly, the possibility of negatively correlated cross-resistance to imidacloprid was identified in three OP- resistant strains exhibiting 2.97-, 2.56- and 3.76-fold sensitivity to imidacloprid (a novel neonicotinoid). This indicated that the latter was less affected by the resistance mechanism(s) present.

Biochemical Characterization of Detoxifying Enzymes in Dimethoate-Resistant Strains of Melon Aphid, <i>Aphis gossypii</i>(Hemiptera: Aphididae)

The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is a highly polyphagous sap sucking pest on wide varieties of crops including cotton and vegetables. It is a notorious vector of many plant viruses that are persistently and non-persistently transmitted. In nature, aphids are regulated by their natural enemies. However, chemical control remains a major management tool even though resistance to insecticides has been documented worldwide. A better understanding of mechanisms by which insecticide resistance occurs and its early detection is desirable to develop effective management strategies. The present investigation was conducted to study the development of resistance to an organophosphate (OP) compound-dimethoate, identify biochemical mechanism(s) involved in resistance and study cross-resistance to imidacloprid in laboratory selected A. gossypii strains in comparison to susceptible strains. Bioassay studies revealed that the LC50 values increased dramatically with dimethoate selection in resistant strains and the resistance ratio (RR) was 270-, 243- and 210-fold greater than that of the susceptible strains by 30th generation. Further, biochemical assays revealed enhanced activities of carboxylesterases (CarE), glutathione S-transferases (GSTs) and cytochrome P450-mediated p-Nitroanisole O-demethylase (PNOD) in resistant strains supporting their role in dimethoate detoxification. This study thus revealed that enhanced activity of detoxifying enzymes viz., CarE, GSTs and PNODs is one of the mechanisms underlying dimethoate resistance in A. gossypii collected from South India. Interestingly, the possibility of negatively correlated cross-resistance to imidacloprid was identified in three OP- resistant strains exhibiting 2.97-, 2.56- and 3.76-fold sensitivity to imidacloprid (a novel neonicotinoid). This indicated that the latter was less affected by the resistance mechanism(s) present.

Effect of Dimethoate on Object Recognition Memory in Wistar Rats and Essay of Treatment with Nettle

Pesticides were economically important chemicals in agriculture. Their use has permitted agricultural progress, through the eradication of harmful insect and the fight against vectors of disease. However, several studies question the beneficial effects of organophosphorus compounds, showing that their deregulated use causes various problems of environmental pollution and human health. The present study shows that chronic exposure to a subtoxic dose of dimethoate is likely to affect cognitive and behavioral functions of rats (both males and females). Our results show that exposure to dimethoate affects both short and long-term memory capacities. The short-term memory results are more pronounced. Treatment with nettle extract allowed a significant improvement in cognitive and behavioral performance of the rats after their exposure to dimethoate.

Effects of Dimethoate Exposure on Locomotor Activity and Anxiety-Like Behavior in Female Wistar Rat

Developmental exposure to organophosphate insecticide is well known to induce neurobehavioral impairments, at late period. The present study aims to investigate the effects of subchronic exposure to Dimethoate, on locomotors skills and anxiety like behavior among wistar rat. Two groups of female’s rats are used. The intoxicated group receives daily, during five weeks, by intragastric gavage, a dose of Dimethoate dissolved in corn oil (100 mg/kg body weight). The control group receives only the corn oil. Spontaneous locomotors activity is evaluated using the Open Field test (OF) and anxiety-like behavior is measured using Elevated Plus-Maze (EPM). Dimethoate induced significant impairment of spontaneous locomotors activities, which is reflected by high decrease of number of squares crossed (SC) in OF. Females exposed to Dimethoate develop further anxiety-like response, expressed by significant reductions of the time spent in open arm of Elevated Plus-Maze.

Comparative analysis of DNA-SIP and magnetic-nanoparticle mediated isolation (MMI) on unraveling dimethoate degraders

Microorganisms are crucial in the bioremediation of organophosphorus pesticides. However, most functional microorganisms (> 99%) are yet to be cultivated. This study applied two cultivation-independent approaches, DNA-SIP and magnetic-nanoparticle mediated isolation (MMI), to identify the functional microorganisms in degrading dimethoate in agricultural soils. MMI identified five dimethoate degraders: Pseudomonas, Bacillus, Ramlibacter, Arthrobacter, and Rhodococcus, whereas DNA-SIP identified three dimethoate degraders: Ramlibacter, Arthrobacter, and Rhodococcus. Also, MMI showed higher resolution than DNA-SIP in identifying functional microorganisms. Two organic phosphohydrolase (OPH) genes: ophC2 and ophB, were involved in dimethoate metabolism, as revealed by DNA-SIP and MMI. The degradation products of dimethoate include omethoate, O,O,S-trimethyl thiophosphorothioate, N-methyl-2-sulfanylacetamide, O,O-diethyl S-hydrogen phosphorodithioate, O,O,O-trimethyl thiophosphate, O,O,S-trimethyl thiophosphorodithioate, and O,O,O-trimethyl phosphoric. This study emphasizes the feasibility of using SIP and MMI to explore the functional dimethoate degraders, expanding our knowledge of microbial resources with cultivation-independent approaches.

Pesticide-Induced Alterations of Esterase and Antioxidant Enzymes of Aquatic Organisms Oreochromis mossambicus and Xenopus laevis

Pesticides are extensively utilized in modern farming to control pests and weeds, thereby ensuring high quality and quantity of crops. Aerial drifts and runoffs after rain transport these agrochemicals to aquatic bodies, where they adversely affect aquatic organisms. We carried out a study to assess the effects of carbaryl and dimethoate on esterase and antioxidant enzyme activities of tadpoles, adult frogs and juvenile fish. These organisms were exposed to sublethal contraptions of 2.9 ppm carbaryl and 4.8 ppm dimethoate for 96 hours. After the exposure period, the fish and frogs were sacrificed and post-mitochondrial fractions were prepared for enzymatic analysis. Acetylcholinesterase (AChE), carboxylesterase (CbE), superoxide dismutase, glutathione peroxidase and catalase were measured. Carbaryl and dimethoate inhibited the activities of acetylcholinesterase, carboxylesterase, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in juvenile fish, tadpoles and adult frogs. Inhibition of SOD, CAT and GPx suggests that the two pesticides caused oxidative stress in the aquatic organisms, while inhibition of AChE and CbE affected the normal transmission of nerve impulses. The results indicate that the two pesticides affect the well-being of the studied aquatic organisms.