Investigating the impact of soil properties, application rates and environmental conditions on pyroxasulfone dissipation and its ecotoxicological effects on soil health in aridisols of Punjab.

This study is to understand the fate and ecological consequences of pyroxasulfone in aridisols of Punjab, a detailed dissipation study in soil, its influence on soil enzymes, microbial count and succeeding crops was evaluated. Half-lives (DT50) increased with an increase in the application rate of pyroxasulfone. Dissipation of pyroxasulfone decreased with increase in organic matter content of soil and was slower in clay loam soil (DT50 12.50 to 24.89) followed by sandy loam (DT50 8.91 to 17.78) and loamy sand soil (DT50 6.45 to 14.89). Faster dissipation was observed under submerged conditions (DT50 2.9 to 20.99 days) than under field capacity conditions (DT50 6.45 to 24.89 days). Dissipation increased with increase in temperature with DT50 varying from 6.46 to 24.88, 4.87 to 22.89 and 2.97 to 20.99 days at 25 ± 2, 35 ± 2 and 45 ± 2 °C, respectively. Dissipation was slower under sterile conditions and about 23.87- to 33.74-fold increase in DT50 was observed under sterile conditions as compared to non-sterile conditions. The application of pyroxasulfone showed short-lived transitory effect on dehydrogenase, alkaline phosphatase and soil microbial activity while herbicide has non-significant effect on soil urease activity. PCA suggested that dehydrogenase and bacteria were most sensitive among enzymatic and microbial activities. In efficacy study, pyroxasulfone effectively controlled Phalaris minor germination, with higher efficacy in loamy sand soil (GR50 2.46 µg mL-1) as compared to clay loam soil (GR50 5.19 µg mL-1).

Synergistic impact of tank mixing pendimethalin and pyroxasulfone on soil enzymatic and microbial dynamics.

A field experiment was carried out during the Rabi 2022-23 at Punjab Agricultural University, Ludhiana to evaluate the effect of pyroxasulfone and pendimethalin on soil enzymatic and microbial activities when applied individually or as a tank mix combination. The experiment employed a factorial randomized complete block design in triplicate encompassing 16 treatments. Control soils exhibited a continuous increase in enzymatic and microbial activities over time. In herbicide-treated plots, a highly dose-dependent lag phase was observed in all enzymatic and microbial activities which gets shorter or disappear at higher application rates. Following the initial lag phase, inhibition in enzymatic and microbial activities was observed with higher inhibition in tank mix combination (90.7 to 99.1% up to 90 days after herbicide application (DAA) followed by pendimethalin (77.3 to 92.9% up to 90 DAA) and pyroxasulfone (30.3 to 76.2% up to 45 DAA). After initial inhibition, enzymatic and microbial activities increased at harvest. Principal component analysis (PCA) revealed that dehydrogenase activity among soil enzymes and bacteria among microbial populations were more sensitive to studied herbicides. Based on the values of the Integrated Biomarker Response (IBRv2), pendimethalin had a greater impact on soil activities than pyroxasulfone, and their combined application exhibited a synergistic effect.

Understanding Environmental Fate: Soil Variability and Rainfall Influence on Triafamone and Ethoxysulfuron Leaching.

Considering the environmental impact of triafamone and ethoxysulfuron, it is crucial to investigate their leaching behaviour under different geographical conditions. The present study evaluates the effects of application rate, soil properties and rainfall conditions on leaching of these herbicides and their metabolites. Ethoxysulfuron leached up to 50-60 cm with 82.95 to 89.23% detected in leachates while triafamone leached only to 10-20 cm and was < 0.01 µg mL-1 in leachates. Highest leachability was observed in loamy sand followed by sandy loam and clay loam soil. M1 metabolite (N-(2-((4,6-dimethoxy-1,3,5-triazin-2-yl) (hydroxy) methyl) -6-fluorophenyl) -1,1-difluoro-N-methyl methane sulfonamide) was majorly present in 0 to 10 cm soil depth. With increase in rainfall, downward mobility of both parent and M1 increased. Amendment of loamy sand soil with farmyard manure reduced the leachability indicating it could mitigate groundwater pollution. However, the effect of different exogenous OM amendments on leaching behaviour of herbicides needs to be evaluated.

Dissipation of tembotrione in maize and its effect on biochemical attributes of maize under mid-hill sub-humid zone.

The present study was undertaken to investigate the dissipation behavior of tembotrione in soil and its effect on the biochemical constituents of maize leaves and grain. The average recovery of tembotrione from soil, maize grain, and stover was in the range of 84.0 to 86.0%, 79.3 to 83.0%, and 81.0 to 84.4%, respectively, with RSD less than 10%. Half-life (DT50) of tembotrione ranged from 9 to 14 days at an application rate of 60 to 240 g ha-1. Terminal residues in soil, maize grain, and stover were below detectable levels (≤ 0.025 µg g-1) at studied application rates. The chemical attributes, i.e., total chlorophyll, total carotenoids, and carbohydrate content, of rice leaves were observed at monthly intervals (zero (2 h), 30, 60 days after the herbicide application) and at harvest for biochemical analysis and grain samples at maturity of the crop for carbohydrate content. The results revealed that total chlorophyll, total carotenoids, and carbohydrate content in maize leaves increased significantly with applied tembotrione treatments, and the maximum increase was noticed in treatment 120 g ha-1. A significant increase in total carbohydrate content in maize grain over the control was noticed in all the herbicide-applied treatments. It can be inferred that the application of tembotrione is safe in the production of food with better quality and food safety.

Comparative studies on adsorptive and photocatalytic potential of differently synthesized ferric oxide nanoparticles for malachite green.

In the present work, effect of different fuels on the structural, morphological, magnetic, adsorptive and photocatalytic properties of ferric oxide nanoparticles (Fe2O3 NPs) was evaluated. Fe2O3 NPs were synthesized via combustion method by using oxalyl dihydrazide (ODH), polyethylene glycol (PEG) and urea as fuels. The indigenously synthesized NPs were characterized by different analytical tools. XRD patterns confirmed the presence of α- and γ-Fe2O3 phases. TEM micrographs displayed average particle size was less than 30 nm. Saturation magnetization amplified with increase in the γ-Fe2O3 content, which was correlated to the fuel used for synthesis. Adsorptive and photocatalytic activity of synthesized NPs was studied using malachite green (MG) dye as a model compound. The uptake behavior for MG dye was influenced by the solution pH, contact time, adsorbent dose, temperature and dye concentration. Thermodynamic studies indicated the endothermic nature of the adsorption phenomenon. The adsorption was well defined with Langmuir and Freundlich isotherms in comparison to Dubinin-Radushkevitch adsorption isotherm model. The trend for percentage removal of MG dye using NPs synthesized by different fuels was: urea > PEG > ODH. Fe2O3 NPs facilitated photo degradation of dye solution in ultra-violet and visible light irradiations.

In-vitro evaluation of rice straw biochars' effect on bispyribac-sodium dissipation and microbial activity in soil.

Dissipation of bispyribac-sodium was estimated in an unamended sandy loam soil and soil amended with rice straw and its biochars in pot culture experiment. Effect of herbicide and amendments on abundance and activity of soil microbial parameters was also assessed by determining soil biological parameters. Amendment type, application rate and soil moisture had differential influence on bispyribac-sodium dissipation and soil's microbial parameters. Amendment of soil with rice straw and its biochars enhanced the dissipation of bispyribac-sodium (DT50 = 7.55-18.44 days) as compared to unamended soil (DT50 = 23.13-28.60 days) and dissipation decreased in this order: rice straw >350BC > 550BC > CBC amended soil > unamended soil. Dissipation of bispyribac-sodium decreased with increase in amendment level of rice straw and its biochars in soil. Irrespective of amendment type and application rate, bispyribac sodium was more persistent under submerged conditions than at field capacity and its DT50 was 10.13 to 28.60 and 7.55-27.14 days, respectively. Dehydrogenase, alkaline phosphatase activity and bacterial population indicated that application of the organic amendment decreased negative effects of the herbicide on soil enzymatic activities. These findings prove that biostimulation using rice straw and its biochars has the potential to decrease the persistence of bispyribac-sodium and minimize its environmental hazards.

Dissipation of Pendimethalin in Soil Under Direct Seeded and Transplanted Rice Field.

The dissipation of pendimethalin applied in direct seeded rice (DSR) and transplanted rice (TPR) field at 1.0 and 2.0 kg a.i. ha-1 followed biphasic first order kinetics (R2 > 0.91) and was comparatively faster under flooded TPR than DSR. The half-life (DT50) of pendimethalin in the soil ranged from 2.22 to 2.80 days in the initial phase and 23.51 to 24.66 days in the final phase in TPR for both application rates. However in DSR, DT50 varied from 3.67 to 4.35 days in the initial phase and 34.19 to 34.99 days in the final phase. Residues of pendimethalin in soil samples analyzed by HPLC and GC-MS/MS were below the detection limit (< 0.003 µg g-1) for both the application rates in DSR and TPR whereas 0.003-0.009 µg g-1 and 0.003-0.008 µg g-1 residues of pendimethalin were found in rice grain and straw samples, respectively.

Dissipation of bispyribac sodium in aridisols: Impact of soil type, moisture and temperature.

The study was conducted to evaluate the influence of physicochemical properties of soil, moisture and temperature on the dissipation behaviour of bispyribac sodium under laboratory conditions. Bispyribac sodium residues were extracted using matrix solid phase dispersion and were quantified using liquid chromatography tandem-mass spectrometry. The mean percent recovery of bispyribac sodium from studied soils ranged from 82.7 ±â€¯8.3-105.1±â€¯2.6%. The limit of quantification and limit of detection was 0.006 and 0.002 µg g-1, respectively. Dissipation of bispyribac sodium followed first order kinetics and soil type greatly influenced the dissipation behaviour of bispyribac sodium. Dissipation was faster in loam soil (DT50 = 12.79-14.52days) followed by clay loam (DT50 = 22.01-23.15days), sandy loam (DT50 = 23.34-25.17 days) and loamy sand soil (DT50 = 25.39-27.32days). The amendment of soil with FYM enhanced the dissipation of bispyribac sodium by 1.86-5.96-fold. It dissipated slowly under submerged (DT50 = 21.41-40.96days) conditions as compared to field capacity (DT50 = 12.79-27.32days) in studied soils. The degradation rate increased with the increase in temperature in studied soils and DT50 ranged from 12.79 to 40.96, 7.36-36.96 and 4.09-31.61days at 30, 40 and 50 °C, respectively.

Time and temperature dependent adsorption-desorption behaviour of pretilachlor in soil.

Understanding and quantifying the adsorption-desorption behaviour of herbicide in soil is imperative for predicting their fate and transport in the environment. In the present study, the effect of time and temperature on the adsorption-desorption behaviour of pretilachlor in soils was investigated using batch equilibration technique. The adsorption-desorption kinetics of pretilachlor in soils was two step process and was well described by pseudo-second-order kinetic model. Freundlich model accurately predicted the sorption behaviour of pretilachlor. The adsorption-desorption of pretilachlor varied significantly with the concentration, temperature and properties of soil viz. organic matter and clay content. All the studied soils had non-linear slopes (n < 1) and degree of nonlinearity increased with increase in clay, organic matter content and temperature (p < 0.05). Desorption of pretilachlor was hysteretic in studied soils and hysteresis coefficient varied from 0.023 to 0.275. Thermodynamic analysis showed that pretilachlor adsorption onto soils was a feasible, spontaneous and endothermic process which becomes more favourable at high temperature. It could be inferred that the adsorption of pretilachlor on soils was physical in nature.

Effect of Soil Type, Moisture and Temperature on the Dissipation of Penoxsulam in Soil Under Laboratory Conditions.

A comprehensive study was conducted to evaluate the effect of concentration, moisture conditions, temperature and soil type on dissipation of penoxsulam in soil under laboratory conditions. Penoxsulam residues from the soil were extracted using matrix solid phase dispersion method and quantified using high performance liquid chromatography with UV detector at 230 nm. Dissipation followed first order kinetics and penoxsulam dissipated within 60 days in all the treatments with half-life varying from 12.60 to 30.08 days. Soil type greatly influenced the dissipation of penoxsulam and it was found to be slower in clay loam followed by loam, sandy loam and loamy sand soil. However, irrespective of soil type, dissipation of penoxsulam increased with increase in moisture content of soil and temperature.

Temperature Dependent Adsorption-Desorption Behaviour of Pendimethalin in Punjab Soils.

This study shows the effect of soil type and temperature on the adsorption and desorption behaviour of pendimethalin using a batch equilibration technique. Adsorption kinetics followed pseudo-second-order-model (R2 > 0.99). The shape of adsorption curve for studied soils was S-type at 30 and 40°C and L-type at 50°C. The isotherms were nonlinear and were well described by Freundlich equation. Adsorption capacity ranged from 1.4 to 2.2 µg1 - 1/n g-1 mL1/n and the order of adsorption was: clay loam > sandy loam > loamy sand indicating strong affinity of pendimethalin towards organic matter and clay content. Irrespective of soil type, the adsorption of pendimethalin increased with increase in temperature suggesting endothermic process. Freundlich desorption coefficient was greater than adsorption in all soils at studied temperatures indicating hysteresis. Thermodynamic parameters revealed spontaneous adsorption process which becomes more favourable at high temperature. The adsorption of pendimethalin was dominated by surface adsorption at lower equilibrium concentration and partition at high concentrations.

Effect of light conditions and chemical characteristics of water on dissipation of glyphosate in aqueous medium.

The present study was conducted to determine the effect of light conditions and chemical properties of water on dissipation of glyphosate. The residues of glyphosate and aminomethylphosphonic acid (AMPA) were quantified using fluorescence spectrophotometer after derivatization with 9-fluoroenylmethoxycarbonyl chloride (FMOC-Cl) and orthopthaldehyde (OPA). Average percent recoveries of glyphosate and AMPA from distilled, tap, and ground water ranged from 87.5 to 94.9, 87.3 to 93.7, and 80.6 to 92.0, respectively, with relative standard deviation less than 10%. The limit of detection and limit of quantification of glyphosate and AMPA from different water matrices ranged from 0.001 to 0.03 µg mL-1 and 0.003 to 0.01 µg mL-1, respectively. The dissipation of glyphosate followed the first-order kinetics, and half-life varied from 1.56 to 14.47 and 13.14 to 42.38 days under UV and sunlight, respectively. The pH and electrical conductivity (EC) of water has differential influence on dissipation of glyphosate, and it increased with increase in pH and EC.

Influence of Long Term Application of Butachlor on its Dissipation and Harvest Residues in Soil and Rice.

The study delineates the effect of repeated application of butachlor to rice crop from 1997 onwards. Additionally, in 2014 and 2015, dissipation kinetics of butachlor in soil was studied under field and laboratory conditions. The average recovery of butachlor for soil, rice grain and rice straw ranged between 80.3%-93.2% and 82.8%-96.5% with quantification limit of 0.01 and 0.003 µg g-1 for HPLC and GC-MS/MS, respectively. The dissipation of butachlor followed first order kinetics and half-life under long term field trials in rice soil varied from 15.2 to 19.29 days and 25.94 to 29.79 days under field and laboratory conditions, respectively. The residue of butachlor in soil, rice grain and straw samples at harvest over the years was below the quantification limit and no quantifiable amount of metabolites were present in soil at harvest suggestive of its safe application.

Persistence behaviour of pretilachlor in puddled paddy fields under subtropical humid climate.

The paper delineates the field trials conducted to investigate the persistence behaviour and dissipation kinetics of pretilachlor in puddled paddy fields under subtropical humid climatic region. Matrix solid phase dispersion (MSPD) method was used for extraction of the pretilachlor from paddy grain and paddy soil samples collected from the experimental field. Pretilachlor residues were quantified using high-performance liquid chromatography (HPLC) with UV/Vis detector at 210 nm. The average recoveries of pretilachlor extracted from matrix ranged from 80.3 to 103.3% with standard deviation less than 10% and sensitivity of 0.01 µg g(-1). The dissipation rate of pretilachlor in paddy field soil and paddy field water followed first-order kinetics with decrease in pretilachlor residues as a function of time. Faster dissipation of pretilachlor was observed in paddy field water than in paddy field soil with half life of 1.89-2.97 days and 7.52-9.58 days, respectively. At harvest, the residues of pretilachlor in the paddy soil and paddy crop samples were below the detection limit.

Quantification of penoxsulam in soil and rice samples by matrix solid phase extraction and liquid-liquid extraction followed by HPLC-UV method.

The paper exploits the development of novel, simple and sensitive methodology involving matrix solid phase dispersion (MSPD) and the comparison of MSPD with liquid-liquid extraction (LLE) for the evaluation of residual penoxsulam in soil and rice samples. Extracted samples were analyzed by high-performance liquid chromatography (HPLC) with ultraviolet detector at 230 nm. Both methods were optimized, considering different parameters, and under optimum conditions, the mean recoveries obtained were in the range of 85-104 % for MSPD and 78.8-90.7 % for LLE. Precision values expressed as relative standard deviation (RSD) were ≤10 for MSPD and ≤15 for LLE. Linearity for penoxsulam was in the range of 0.01-20 µg mL(-1) with limits of detection and limits of quantification of 0.01 and 0.03 mg kg(-1), respectively.

Insights into adsorption performance and mechanism of chitosan-bentonite biocomposites for removal of imazethapyr and imazamox.

In the present study, chitosan-bentonite biocomposites were synthesised by ultrasonication, characterized using spectral techniques and assessed for their effectiveness in removing imazethapyr and imazamox from aqueous solution. The response surface methodology based box behnken design was utilized to generate optimum conditions viz. pH (1 to 9), adsorbent dose (0.01 to 1.0 g), contact time (0.5 to 48 h) and temperature (15 to 55 °C) for adsorption of herbicides on biocomposites. Based on model predictions, 60.4 to 91.5 % of imazethapyr and 31.7 to 46.4 % of imazamox was efficiently removed under optimal conditions. Adsorption data exhibited a strong fit to pseudo-second-order kinetic (R2 > 0.987) and Freundlich isotherm (R2 > 0.979). The adsorption capacity ranged from 3.88 to 112 µg1-ng-1mLn and order of adsorption was: low molecular weight chitosan-bentonite> medium molecular weight chitosan-bentonite> high molecular weight chitosan-bentonite> bentonite. Thermodynamic experiments suggested a spontaneous, exothermic process, reducing the system randomness during adsorption. Desorption experiments revealed successful desorption ranging from 91.5 to 97.0 % using 0.1 M NaOH. The adsorption mechanism was dominated by synergistic electrostatic interactions and hydrogen bonding. These results collectively indicated the potential environmental remediation application of chitosan-bentonite biocomposites to adsorb imazethapyr and imazamox from wastewaters.

Smoothened-activating lipids drive resistance to CDK4/6 inhibition in Hedgehog-associated medulloblastoma cells and preclinical models.

Medulloblastoma is an aggressive pediatric brain tumor that can be driven by misactivation of the Hedgehog (HH) pathway. CDK6 is a critical effector of oncogenic HH signaling, but attempts to target the HH pathway in medulloblastoma have been encumbered by resistance to single-agent molecular therapy. We identified mechanisms of resistance to CDK6 inhibition in HH-associated medulloblastoma by performing orthogonal CRISPR and CRISPR interference screens in medulloblastoma cells treated with a CDK4/6 inhibitor and RNA-Seq of a mouse model of HH-associated medulloblastoma with genetic deletion of Cdk6. Our concordant in vitro and in vivo data revealed that decreased ribosomal protein expression underlies resistance to CDK6 inhibition in HH-associated medulloblastoma, leading to ER stress and activation of the unfolded protein response (UPR). These pathways increased the activity of enzymes producing Smoothened-activating (SMO-activating) sterol lipids that sustained oncogenic HH signaling in medulloblastoma despite cell-cycle attenuation. We consistently demonstrated that concurrent genetic deletion or pharmacological inhibition of CDK6 and HSD11ß2, an enzyme producing SMO-activating lipids, additively blocked cancer growth in multiple mouse genetic models of HH-associated medulloblastoma. Our data reveal what we believe to be a novel pathway of resistance to CDK4/6 inhibition as well as a novel combination therapy to treat the most common malignant brain tumor in children.

ß-Cyclodextrin-chitosan biocomposites for synergistic removal of imazethapyr and imazamox from soils: Fabrication, performance and mechanisms.

The present study delineates to develop and explore the possibility of using chitosan-ß-cyclodextrin biocomposites as environmentally friendly decontamination agent for removal of imazethapyr and imazamox from soils. The biocomposites were synthesised using ultrasonic assisted technique and characterised by UV-Visible spectrophotometer. The quantification of imazethapyr and imazamox was done using liquid chromatography tandem mass spectrometry. The adsorption capacity for imazethapyr and imazamox ranged from 0.12 to 1.22 and 0.02 to 1.01 µg1-ng-1mLn, respectively in studied soils (p < .05) indicating strong influence of soil properties on adsorption. Desorption studies indicated that distilled water could desorb only 1.23 to 5.48 and 3.11 to 8.63% of adsorbed imazethapyr and imazamox, respectively at high concentrations (1.0 and 10 µg mL-1) whereas herbicides were not desorbed at low concentrations (0.01 and 0.1 µg mL-1). The removal of imazethapyr and imazamox from soils were carried out with ß-cyclodextrin, chitosan and their biocomposites and the influence of various parameters such as type and concentration of extractant, contact time, liquid to soil ratio, temperature and sequential extraction cycle was investigated. Under optimum conditions, herbicides were successfully desorbed from studied soils using low molecular weight chitosan-ß-cyclodextrin biocomposite (LCD) and removal rate varied from 59.42 to 99.44% at initial herbicide concentration of 0.01 to 10 µg mL-1. The highest removal rate of imazethapyr and imazamox was observed for inceptisol 3 followed by entisol, inceptisol 2, aridisol, inceptisol 1, vertisol and alfisol probably due to differential physico-chemical properties of soil which affected the herbicide-soil interactions. Based on these results, LCD can be regarded as effective and environmentally friendly in situ green extracting agent for remediating soils contaminated with imazethapyr and imazamox.

Dissipation and phytotoxicity of imazethapyr and imazamox in soils amended with ß-cyclodextrin-chitosan biocomposite.

Use of imazethapyr and imazamox has been an environmental concern due to their high persistence, water solubility, residue build up and potential to injure the succeeding crops. Hence, it is necessary to develop effective decontamination technology. In present study, effect of ß-cyclodextrin-chitosan biocomposite (LCD) amendment in soil on dissipation of imazethapyr and imazamox and their phytotoxicity on succeeding crop was evaluated. The influence of different experimental variables viz. extractant solution and its concentration, liquid to soil ratio, amount of soil and soil type on dissipation of imazethapyr and imazamox was assessed through chemical assays. Irrespective of herbicide formulation and application rate, amendment of soils with LCD increased the dissipation rate of herbicide and the residues were below the detection limit (<0.005 µg g-1) within 5 to 15 days in aridisol, entisol, inceptisol A, inceptisol B, inceptisol C and 7 to 21 days in alfisol and vertisol. Amendment of soils with LCD significantly reduced the growth inhibition of Brassica juncea (L.) Czern and improved the soil biological activity as evident from increase in dehydrogenase activity and soil bacterial count. Amendment of soils with LCD could be a promising, economically feasible and environmentally benign soil decontamination strategy for imazethapyr and imazamox contaminated soils.

Effect of repeated application of pendimethalin on its persistence and dissipation kinetics in soil under field and laboratory conditions.

The repeated application of herbicide can alter its persistence in the environment. In India, wheat fields are exposed to herbicide application at least once in the cropping season. The present study investigated the dissipation behavior of pendimethalin applied annually to a wheat field over four cropping seasons from 2012 to 2016. The dissipation studies were also conducted under laboratory conditions during 2015-2016. Pendimethalin from soil and wheat grain samples was extracted using matrix solid-phase dispersion and quantified using high-performance liquid chromatography and gas chromatography-tandem mass spectrometry. The average recoveries of pendimethalin from soil and crop produce ranged from 81.3% to 103.1%. The half-life of pendimethalin ranged from 20.9 to 31.3 days and 9.4 to 60.2 days under field and laboratory conditions, respectively. Dissipation of pendimethalin varied significantly over the years under field conditions and was comparatively faster than under laboratory conditions. On the other hand, non-significant variation in the dissipation of pendimethalin in soils under laboratory conditions was observed. The residues of pendimethalin in crop produce at harvest were below the maximum residue limit set by EPA.