Solubility Of Pesticides Research Articles

Impact of biochar on the degradation rates of three pesticides by vegetables and its effects on soil bacterial communities under greenhouse conditions

A 28 days pesticide degradation experiment was conducted for broccoli (Brassica oleracea L. var. italica Planch) and pakchoi (Brassica chinensis L.) with three pesticides (chlorantraniliprole (CAP), haloxyfop-etotyl (HPM), and indoxacarb (IXB)) to explore the effects of biochar on pesticide environmental fate and rhizosphere soil diversity. Rice straw biochar (RB) was applied to soil at a 25.00 t ha−1 dosage under greenhouse conditions, and its effects on the degradation of three pesticides in vegetables and in soil were investigated individually. Overall, RB application effectively facilitated CAP and HPM degradation in broccoli by 13.51–39.42% and in broccoli soil by 23.80–74.10%, respectively. RB application slowed the degradation of CAP, HPM and IXB in pakchoi by 0.00–57.17% and slowed the degradation of CAP in pakchoi by 37.32–43.40%. The results showed that the effect of RB application on pesticide degradation in crops and soil was related to biochar properties, pesticide solubility, plant growth status, and soil characteristics. Rhizosphere soil microorganisms were also investigated, and the results showed that biochar application may be valuable for altering bacterial richness and diversity. The effect of biochar application on pesticide residues in crops and soil was influenced by the vegetable variety first, and the second was pesticide characteristics. RB applied to soil at a 25.00 t ha−1 dosage under greenhouse conditions is recommended for broccoli production to ensure food safety. Our results suggested that biochar application in soil could reduce pesticide non-point source pollution, especially for highly soluble pesticides, and could affect soil microorganisms.

Production and characterization of a biosurfactant produced by Bacillus amyloliquefaciens C11 for enhancing the solubility of pesticides

The production and characterization of lipopeptide biosurfactant obtained from a novel bacterial strain Bacillus amyloliquefaciens C11 isolated from a biopurification system, to enhance the solubility of three pesticides of environmental concern was investigated. Biosurfactant production by B. amyloliquefaciens C11 was evaluated in a 2-L reactor and characterized by chromatographic and spectroscopic methods. Biosurfactant production was associated with bacterial growth and glucose consumption. The produced biosurfactant decreased the surface tension of water from 72 to 28 mN m−1 at 24 h of incubation, with critical micelle concentration (CMC) of 51.5 mg L−1. The polymerase chain reaction for determining the presence of srfAA gene in B. amyloliquefaciens C11 was carried out. The strain exhibited the presence of srfAA gene with amplification at 201 bp, which is specific to surfactin homologues. The production of surfactin was corroborated by high performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of flight mass spectrometry (MALDI-TOF-MS) analyses. The HPLC analysis showed six isoforms of surfactin, being the isoform D found in mayor percentage (41%). Thermal gravimetric analysis (TGA) revealed the thermostability of the biosurfactant. The obtained biosurfactant maintained its properties during exposure to temperatures in range of 30–80 °C and pH values in range of 5–9. The surfactin produced by B. amyloliquefaciens C11 increased the solubility in water of chlorpyrifos, iprodione and atrazine by 7.5-fold, 1.3-fold, and 1.4-fold, respectively. Our results show that the biosurfactant produced by B. amyloliquefaciens C11 improves the bioavailability of pesticides and consequently could improves the efficiency of bioremediation processes.

In vitro assessment of the pesticide bioaccessibility in Dendrobium officinale Kimura et Migo.

Bioaccessibility (BA) is a crucial factor for evaluating the absorption of pollutants in the human digestion system, which is of vital importance for risk assessment of pollutants via food intake. Multi-pesticides were detected in Dendrobium officinale Kimura et Migo (D. officinale), a popular dual-use plant with both botanical medicine and food applications. Nevertheless, the BA of pesticides in D. officinale remains unknown, restricting its market size. Herein, the BA of 19 pesticides with varying properties was evaluated by using an in vitro digestion model, showing BA values between 27.4 and 96.8%. The BA was controlled by the hydrophobicity and water solubility of pesticides, since the significant correlation between these two factors and BA values was observed. Moreover, co-ingested food ingredients could influence the BA, wherein the effect was significant for pesticides of logKow values no less than 3. Lipids enhanced the BA by 9-66%, whereas proteins or carbohydrates decreased BA values by 6-28%. In particular, considering the BA, the risk quotient values were reduced by 3-73%. Clearly, this work suggested that traditional risk assessment without considering the BA would seriously overestimate the actual risk of pesticides in food.

Understanding the influence of polymeric ionic liquid sorbent coating substituents on cannabinoid and pesticide affinity in solid-phase microextraction

To understand factors that drive pesticide-cannabinoid selectivity in solid-phase microextraction (SPME), eight new polymeric ionic liquid (PIL) sorbent coatings were designed and compared to four previously reported PIL sorbent coatings for the extraction of pesticides. The four PIL sorbent coatings consisted of either vinylimidazolium or vinylbenzylimidazolium ILs with long alkyl chain substituents (i.e., -C8H17 or -C12H25) and bis[(trifluoromethyl)sulfonyl]imide ([NTf2−]) anions, from which the eight new PIL sorbent coatings were adapted. Modifications to the chemical structure of IL monomers and crosslinkers included incorporation of polymerizable p-styrenesulfonate or 3-sulfopropyl acrylate anions, the addition of aromatic moieties, and/or the addition of polar functional groups (i.e., -OH or -O- groups). A total of ten commonly regulated pesticides and six cannabinoids were examined in this study. The effect of salt on the solubility of pesticides and cannabinoids in aqueous solutions was assessed by determining their extraction efficiencies in the presence of varied methanol content. Differences in their solubilities appear to play a dominant role in enhancing pesticide-cannabinoid selectivity. The selectivity, represented as the ratio of pesticide total peak areas to cannabinoid total peak areas, also exhibited a moderate correlation to the affinity of the sorbent coatings towards both the pesticides and the cannabinoids. A positive correlation was observed for the pesticides and a negative correlation was observed for the cannabinoids, suggesting that selectivity was driven by more than the presence of salt in the samples. The sorbent coatings’ affinity towards each class of analytes were examined to determine specific interactions that might influence selectivity. The two main structural modifications increasing pesticide-cannabinoid selectivity included the absence of aromatic moieties and the addition of hydrogen bond donor functional groups. Extractions of simple aromatic molecules as probes were performed under similar extraction conditions as the cannabinoids and confirmed the influence of hydrogen bonding interactions on sorbent coating affinity.

A general supramolecular adjuvant for pesticides based on host-guest recognition.

Pesticides are indispensable in agriculture and can effectively improve the yields and quality of crops. Due to their weak water solubility, most pesticides need to be dissolved by adding solubilizing adjuvants. In this work, based on molecular recognition of the macrocyclic host, we developed a novel supramolecular adjuvant, called sulfonated azocalix[4]arene (SAC4A), which significantly improves the water solubility of pesticides. SAC4A presents multiple advantages, including high water solubility, strong binding affinity, universality, and simple preparation. SAC4A showed an average binding constant value of 1.66 × 105 M-1 for 25 pesticides. Phase solubility results indicated that SAC4A increased the water solubility of pesticides by 80-1310 times. The herbicidal, fungicidal, and insecticidal activities of supramolecular formulations were found to be superior to those of technical pesticides, and the herbicidal effects were even better than those of commercial formulations. Overall results revealed the potential of SAC4A to improve the solubility and effectiveness of pesticides, providing a new development idea for the application of adjuvants in agriculture. © 2023 Society of Chemical Industry.

Advances in Biopolymeric Nanopesticides: A New Eco-Friendly/Eco-Protective Perspective in Precision Agriculture.

Pesticides are essential to contemporary agriculture and are required to safeguard plants from hazardous pests, diseases, and weeds. In addition to harming the environment, overusing these pesticides causes pests to become resistant over time. Alternative methods and agrochemicals are therefore required to combat resistance. A potential solution to pesticide resistance and other issues may be found in nanotechnology. Due to their small size, high surface-area-to-volume ratio, and ability to offer novel crop protection techniques, nanoformulations, primarily biopolymer-based ones, can address specific agricultural concerns. Several biopolymers can be employed to load pesticides, including starch, cellulose, chitosan, pectin, agar, and alginate. Other biopolymeric nanomaterials can load pesticides for targeted delivery, including gums, carrageenan, galactomannans, and tamarind seed polysaccharide (TSP). Aside from presenting other benefits, such as reduced toxicity, increased stability/shelf life, and improved pesticide solubility, biopolymeric systems are also cost-effective; readily available; biocompatible; biodegradable; and biosafe (i.e., releasing associated active compounds gradually, without endangering the environment) and have a low carbon footprint. Additionally, biopolymeric nanoformulations support plant growth while improving soil aeration and microbial activity, which may favor the environment. The present review provides a thorough analysis of the toxicity and release behavior of biopolymeric nanopesticides for targeted delivery in precision crop protection.

Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system’s average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

Photochemical interactions between pesticides and plant volatiles

Among the numerous studies devoted to the photodegradation of pesticides, very scarce are those investigating the effect of plant volatiles. Yet, pesticides can be in contact with plant volatiles after having been spread on crops or when they are transported in surface water, making interactions between the two kinds of chemicals possible. The objectives of the present study were to investigate the reactions occurring on plants. We selected thyme as a plant because it is used in green roofs and two pesticides: the fungicide chlorothalonil for its very oxidant excited state and the insecticide imidacloprid for its ability to release the radical NO2 under irradiation. Pesticides were irradiated with simulated solar light first in a solvent ensuring a high solubility of pesticides and plant volatiles, and then directly on thyme's leaves. Analyses were conducted by headspace gas chromatography–mass spectrometry (HS-GC–MS), GC–MS and liquid chromatography-high resolution mass spectrometry (LC-HRMS). In acetonitrile, chlorothalonil photosensitized the degradation of thymol, α-pinene, 3-carene and linalool with high quantum yields ranging from 0.35 to 0.04, and was photoreduced, while thymol underwent oxidation, chlorination and dimerization. On thyme's leave, chlorothalonil was photoreduced again and products arising from oxidation and dimerization of thymol were detected. Imidacloprid photooxidized and photonitrated thymol in acetonitrile, converting it into chemicals of particular concern. Some of these chemicals were also found when imidacloprid was irradiated dispersed on thyme's leaves. These results show that photochemical reactions between pesticides and the plants secondary metabolites can take place in solution as on plants. These findings demonstrate the importance to increase our knowledge on these complex scenarios that concern all the environmental compartments.

Influence of rainfall and seasonal crop practices on nutrient and pesticide runoff from soybean dominated agricultural areas in Pampean streams, Argentina

An increase in the spatial variability of rainfall is expected due to climate change. This implies increasing rainfall rates during spring and summer in the Pampas region, Argentina, period of maximum application of agrochemicals, which might cause an increase in pesticides and nutrients carried to surface water systems, as runoff by rainfall is one of the main pathways for diffuse pollution. The crops phenological stage can also affect pesticide and nutrient runoff since the applied agrochemicals and soil cover differ in each stage. In this study, we assessed the influence of rainfall and seasonal crop practices on water quality (nutrient and pesticide concentrations) in three streams in the Pampas region, Argentina. Five sampling campaigns were performed before and after three rainfall events during two different seasons of crop practices (SCP1, SCP2) and the physicochemical characteristics of the stream and runoff water were analyzed. The pesticide concentrations in the streams presented a general increase immediately after the rainfall event. Water quality was also affected, as an increase in ammonium, soluble reactive phosphorus (SRP), biological oxygen demand (BOD), and turbidity was observed. The crops phenological stage influenced pesticide and nutrient types and concentrations detected in the streams. During SCP1, mainly characterized by chemical fallow and sowing of soybean and vegetative growth and flowering of corn, ammonium, SRP, BOD, turbidity, and some pesticides, such as metolachlor, showed significantly higher results than those found in SCP2 (grain filling and vegetative growth of soybean and corn sowing). The pesticide concentrations detected in runoff water depended mostly on the pesticide solubility, the lateral slope of the streams, and the percentage of woody riparian vegetation cover. The results obtained show the relevance of assessing the influence of rainfall and crops phenological stages on the dynamics of surface water and on pesticide and nutrient runoff for environmental monitoring.

Zoxamide accumulation and retention evaluation after nanosuspension technology application in tomato plant.

Low water solubility of pesticide requires formulations with high levels of stabilizers and organic solvents. Moreover, only 0.1% of the applied pesticides formulation reaches the target, while 99.9% spreads in the surrounding environment. Therefore, there is the need for more efficient and environmentally sustainable alternatives. Zoxamide (ZO) nanosuspension was prepared through a media milling technique by using the stabilizer polysorbate 80. The thin and acicular crystals obtained, showed particle size of 227 nm, polydispersion index of 0.247 and zeta potential of -28 mV. Dimensional data and morphology of ZO nanocrystals alone, on tomato leaves and berries, were confirmed by scanning electron microscopy. The reduction in size for ZO crystals obtained after the milling process increased pesticide water solubility till 39.6mg L-1 , about 1.6 the solubility obtained with a conventional commercial formulation. Field and dip contamination trials performed on tomato plants showed the nanosuspension's ability to increase ZO deposition and accumulation versus a coarse ZO suspension and commercial formulation, respectively. The nanoformulation proposed, resulted in low cost and was easy to make. Moreover, the organic solvent-free composition together with a low surfactant addition assured a minor environmental impact. Finally, the increased retention and deposition of the fungicide can reduce the amounts of ZO formulation applied to tomatoes. © 2021 Society of Chemical Industry.

What happens when pesticides are solubilised in binary ionic/zwitterionic-nonionic mixed micelles?

HypothesisSurfactants have been widely used as adjuvants in agri-sprays to enhance the solubility of pesticides in foliar spray deposits and their mobility through leaf cuticles. Previously, we have characterised pesticide solubilisation in nonionic surfactant micelles, but what happens when pesticides become solubilised in anionic, cationic and zwitterionic and their mixtures with nonionic surfactants remain poorly characterised. ExperimentsTo facilitate characterisations by SANS and NMR, we used nonionic surfactant hexaethylene glycol monododecyl ether (C12E6), anionic sodium dodecylsulphate (SDS), cationic dodecyltrimethylammonium bromide (DTAB) and zwitterionic dodecylphosphocholine (C12PC) as model adjuvant systems to solubilise 3 pesticides, Cyprodinil (CP), Azoxystrobin (AZ) and Difenoconazole (DF), representing different structural features. The investigation focused on the influence of solubilisates in driving changes to the micellar nanostructures in the absence or presence of electrolytes. NMR and NOESY were applied to investigate the solubility and location of each pesticide in the micelles. SANS was used to reveal subtle changes to the micellar structures due to pesticide solubilisation with and without electrolytes. FindingsUnlike nonionic surfactants, the ionic and zwitterionic surfactant micellar structures remain unchanged upon pesticide solubilisation. Electrolytes slightly elongate the ionic surfactant micelles but have no effect on nonionic and zwitterionic surfactants. Pesticide solubilisation could alter the structures of the binary mixtures of ionic/zwitterionic and ionic/nonionic micelles by causing elongation, shell shrinkage and dehydration, with the exact alteration being determined by the molar ratio in the mixture.

Use of GA-ANN and GA-SVM for a QSPR study on the aqueous solubility of pesticides

The partitioning tendency of pesticides, in this study herbicides in particular, into different environmental compartments depends mainly of the physicochemical properties of the pesticides itself. Aqueous solubility (S) indicates the tendency of a pesticide to be removed from soil by runoff or irrigation and to reach surface water. The experimental procedure for determining the aqueous solubility of pesticides is very expensive and difficult. QSPR methods are often used to estimate the aqueous solubility of herbicides. The artificial neural network (ANN) and support vector machine (SVM) methods, always associated with selection of a genetic algorithm (GA) of the most important variable, were used to develop QSPR models to predict the aqueous solubility of a series of 80 herbicides. The values of log S of the studied compounds were well correlated with the descriptors. Considering the pertinent descriptors, a Pearson correlation squared coefficient (R2) of 0.8 was obtained for the ANN model with a structure of 5-3-1 and 0.8 was obtained for the SVM model using the RBF function for the optimal parameters values: C = 11.12; ? = 0.1111 and ? = 0.222.

Preparation and characterization of an oil-in-water microemulsion of thiamethoxam and acetamiprid without organic solvent for unmanned aerial vehicle spraying

Spraying pesticides is an essential measure for crop protection in agricultural production process. However, the large organic solvents and surfactants usage of common pesticide formulations have caused concern about environmental pollution. In recent years, unmanned aerial vehicle (UAV) spraying has gained more and more attention because of its ability to reduce the usage of pesticide and replace traditional human-powered spraying equipment. Nevertheless, the potential pollution hazard, spray drift and loss of current pesticide formulations in actual aerial spraying also remain challenging to date. Based on the requirement of appropriative pesticide formulation for UAV spraying, a novel oil-in-water microemulsion of thiamethoxam and acetamiprid without any organic solvents was investigated in this study. Complex emulsifiers were proposed to increase the solubility of pesticides in water, which could avoid the addition of unnecessary organic solvents in microemulsions. The physicochemical properties and application performance of the microemulsions were determined using visual observation, Turbiscan technique, laser particle size, indoor spraying experiments, high-performance liquid chromatography with ultraviolet detection and transmission electron microscopy. The optimal microemulsion with the formulation of 10 % sodium dodecyl sulfate and 10 % fatty alcohol polyoxyethylene ether sulfate consisted of small particles with a mean diameter of 1.9 nm, and exhibited good stability, improved wettability, anti evaporation, and spraying performance with deposition coverage rate of 16.2 %. This study expanded the possibility of the preparation and development of environmentally friendly pesticide formulations applicable for UAV agricultural spraying.

The using of the Index of Ideality of Correlation (IIC) to improve predictive potential of models of water solubility for pesticides.

Models for water solubility of pesticides suggested in this manuscript are important data from point of view of ecologic engineering. The Index of Ideality of Correlation (IIC) of groups of quantitative structure-property relationships (QSPRs) for water solubility of pesticides related to the calibration sets was used to identify good in silico models. This comparison confirmed the high IIC set provides better statistical quality of the model for the validation set. Though there are large databases on solubility, the reliable prediction of the endpoint for new substances which are potential pesticides is an important ecologic task. Unfortunately, predictive models for various endpoints suffer overtraining, and the IIC serves to avoid or at least reduce this. Thus, the approach suggested has both theoretical and economic effects for ecology.

Novel eco-friendly ionic liquids to solubilize seven hydrophobic pesticides

In line with the requirements of green chemistry, the preparation of eco-friendly pesticide formulations has become an inevitable development trend. In this work, we explored the feasibility of four new ionic liquids (ILs, [Octyl trimethyl ammonium] anions, anions = proline, valine, leucine, tartaric acid) as environmentally-friendly solvents for pesticide emulsifiable concentrates, and also as alternatives to traditional imidazole-based ILs since they do not contain the imidazole ring and the anions are natural substances. The results showed that the solubility of pesticides (clethodim, metolachlor, acetochlor, prochloraz, thiamethoxam, glyphosate, acetamiprid) in water with 25%w/v ILs was significantly improved, especially for acetamiprid, where the solubility was increased 19-fold, while it only increased about 4 to 5-fold after adding imidazole-based ILs in our previous work. In addition, the solubilization mechanism was explored by many methods and found that the solubilization effect does not completely depend on the critical micelle concentration (CMC) value but has a great relationship with the hydrophilicity of the ILs which may affect the size of micelles and release behavior to pesticides. Finally, 1H NMR was used to investigate the solubilization sites of ILs for glyphosate, and the interaction between pesticides and anions was explored by the quantum chemical method.

Limiting diffusion coefficients of glufosinate ammonium, cymoxanil and imidacloprid in aqueous solutions

We have measured the limiting diffusion coefficients of three different pesticides in aqueous solutions: glufosinate ammonium, cymoxanil and imidacloprid, highly used for tomato production. The experiments were carried in aqueous solutions, at 25 °C, at concentrations below 3 mmol dm−3 (depending on the solubility of pesticides). Mutual diffusion coefficients (D) obtained by using the Taylor dispersion technique, and by using pure water and different solutions of concentration c, as carrier stream and injection solutions, respectively, show that the systems can be analyzed as binary ones. The hydrodynamic radii and the respective limiting diffusion coefficients of the glufosinate anion, cymoxanil and imidacloprid have also been estimated. For the electrolyte glufosinate ammonium, by using the Nernst equation, it is also possible to estimate the limiting molar conductivity of the glufosinate anion.In order to mimic field conditions, we have measured the tracer diffusion coefficients of glufosinate ammonium in aqueous solutions of ammonium nitrate at different concentrations, permitting us to analysis the salting-in effects on the diffusion of this pesticide.From these measurements useful information on the thermodynamic, transport and structural parameters can be obtained, allowing a better understanding of the behaviour of these compounds in aqueous solution.These studies have been complemented with 1H and 31P NMR spectroscopy in order to obtain more additional structural information on the interaction of ammonium nitrate with glufosinate-ammonium in aqueous solution. The results obtained support the hypothesis of salting-in effects on the diffusion of this pesticide in aqueous solution.

Conformation-independent quantitative structure-property relationships study on water solubility of pesticides

Water solubility is a key physicochemical parameter in pesticide control and regulation, although sometimes its experimental determination is not an easy task. In this study, we present Quantitative Structure-Property Relationships (QSPRs) for predicting the water solubility at 20 °C of 1211 approved heterogeneous pesticide compounds, collected from the online Pesticides Properties Data Base (PPDB). Validated and generally applicable Multivariable Linear Regression (MLR) models were established, including molecular descriptors carrying constitutional and topological aspects of the analyzed compounds. The most representative descriptors were selected from the exploration of a large number of about 18,000 structural variables. A hybrid approach that involves a molecular descriptor, a fingerprint, and a flexible descriptor showed the best predictive performance.

Solvent effect on endosulfan adsorption onto polymeric arginine-methacrylate cryogels.

Endosulfan is a persistent insecticide that is still used in some countries even though it is life-threatening and banned in the agricultural struggle. The solubility of pesticides in water is negligible. It is known that pesticides with better solubility in organic solvents have different solubility when the dielectric constants of these solvents are taken into account. The polymeric structure of arginine was modified with methacrylate to be a functional monomer, and it was immobilized on a solid support, poly(HEMA), and finally, poly(2-hydroxyethyl methacrylate-arginine methacrylate) was obtained and used as an effective adsorbent. The effect of organic solvents on endosulfan adsorption was investigated for the first time in the literature. Endosulfan was removed from alcohol media by using this polymeric structure synthesized by exploiting alcoho-phobic interaction in this work. Nuclear magnetic resonance (NMR), elemental analysis, and Fourier transform infrared spectroscopy (FTIR) methods were used for the structural characterization and therefore to prove successful synthesis of cryogels. Morphological characteristics were also investigated by scanning electron microscopy (SEM), an N2 adsorption method, and swelling test. Adsorption experiments were carried out against varying interaction time and concentration parameters in the batch system. Since the alcohol used as a solvent has a pH value close to the ionic strength of drinking water, no change was made in the pH of the solution. Endosulfan molecules dissolved in solvents such as toluene, dichloromethane, acetone, and chloroform were removed using poly(HEMA-ArMA) cryogels to determine the solvent effect on the adsorption of endosulfan. As expected, the removal of endosulfan from the solvent toluene provided the best result. Although the adsorption in toluene is almost 9.5 times higher than that in ethanol, the use of toluene in the adsorption process due to its chemical structure is not feasible. Thus, experiments were carried out in ethanol.

Adsorption-desorption and hysteresis phenomenon of tebuconazole in Colombian agricultural soils: Experimental assays and mathematical approaches

The adsorption-desorption, hysteresis phenomenon, and leachability of tebuconazole were studied for Inceptisol and Histosol soils at the surface (0–10 cm) and in the subsurface (40–50 cm) of an agricultural region from Colombia by the batch-equilibrium method and mathematical approaches. The experimental Kfa and Kd (L kg−1) values (7.9–289.2) decreased with depth for the two Inceptisols and increased with depth for the Histosol due to the organic carbon content, aryl and carbonyl carbon types. Single-point and desorption isotherms depended on adsorption reversibility and suggested that tebuconazole showed hysteresis; which can be adequately evaluated with the single-point desorption isotherm and the linear model using the hysteresis index HI. The most suitable mathematical approach to estimate the adsorption isotherms of tebuconazole at the surface and in the subsurface was that considering the combination of the n-octanol-water partition coefficient, pesticide solubility, and the mass-balance concept.Tebuconazole had similar moderate mobility potential as compared with the values of other studies conducted in temperate amended and unamended soils, but the risk of the fungicide to pollute groundwater sources increased when the pesticide reached subsurface soil layers, particularly in the Inceptisols.

Partial characterization of a biosurfactant extracted from Pseudomonas sp. B0406 that enhances the solubility of pesticides

ABSTRACTBiodegradation of some organochlorine and organophosphate pesticides is difficult because of their low solubility in water and, therefore, their low bioavailability. To overcome the hydrophobicity problem and the limited pesticide availability, biosurfactants play a major role. In this study, we evaluated the effect of an extract from Pseudomonas sp. B0406 strain with surfactant properties, on the solubility of two pesticides: endosulfan (ED) and methyl parathion (MP). Such a process was performed in order to increase the aqueous solubility of both pesticides, to increase its availability to microorganisms and to promote their biodegradation. The extract from Pseudomonas sp. B0406 showed a critical micellar concentration of 1.4 g/L and the surface tension at that point was 40.4 mN/m. The preliminary chemical and physical partial characterization of the extract with surfactant properties indicated that it is an anionic glycolipid, which increases the solubility of both pesticides of 0.41 at 0.92 mg/L for ED and of 34.58 at 48.10 mg/L for MP. The results of this study suggest the effectiveness of this extract in improving the solubility of both pesticides ED and MP in water and, therefore, of its potential use to enhance the degradation of these pesticides.