Dissipation Rate Constants Research Articles

The impact of growing season and cultivation systems on the dissipation of profenofos and λ- cyhalothrin on Brassica juncea: a comparative study

This study was conducted to contour dissipation patterns of two pesticides (profenofos and λ-cyhalothrin) on B. juncea (green mustard) grown under green house (G.H.) and open field (O.F.) during dry and wet season. The dissipation data of studied pesticides were fitted into the first order kinetic equation. Based on the dissipation rate constant, k obtained, profenofos dissipates faster than λ-cyhalothrin regardless of growing system and season. The dissipation of both pesticides were found to be more rapid during dry season compare to wet season. Growing system however displayed a rather contradictory results for profenofos where during dry season, faster dissipation took place in O.F., while during wet season rapid dissipation took place in G.H. λ-Cyhalothrin on the other hand exhibits faster dissipation in G.H. during both seasons. The half-lives obtained for profenofos and λ-cyhalothrin in B. juncea were 0.66–1.8 days and 1.18–3.7 days, respectively. Based on this experiment, terminal residue obtained for profenofos and λ-cyhalothrin for B. juncea were lower than the stipulated MRL. This work was momentous to guide appropriate applications and establishment of accurate PHI of pesticides in B. juncea that will benefit farmers in a country with humid tropical climate.

Benchmarking the Persistence of Active Pharmaceutical Ingredients in River Systems.

Assessing the persistence of organic micropollutants from field data has been notoriously laborious, requiring extensive data including emissions and chemical properties, and the application of detailed mass-balance models, which often contain parameters that are impossible to measure. To overcome some of these obstacles, we developed the concept of persistence benchmarking for large rivers that receive numerous emissions and provide enough residence time to observe the dissipation of compounds. We estimated the dissipation rate constants of 41 compounds (mostly active pharmaceutical ingredients) from five measurement campaigns in the Rhine and Danube rivers using concentration rate profiles with respect to carbamazepine. Dissipation rates clearly distinguished between known fast- and slow-degrading compounds, and campaign-specific boundary conditions had an influence on a minor subset of compounds only. Benchmarking provided reasonable estimates on summer total system half-lives in the Rhine compared to previous laboratory experiments and a mass-balance modeling study. Consequently, benchmarking can be a straightforward persistence assessment method of continuously emitted organic micropollutants in large river systems, especially when it is supported by field monitoring campaigns of proper analytical quality and spatial resolution.

Photo-thermal conversion properties of Cr, Mo, and W nanofluids in polyethylene glycol prepared by laser ablation in liquid method for direct absorption solar collectors applications

Nanofluids (NFs) are promising materials for solar-energy harvesting. The main drawback of NFs is their instability and longtime preparation methods that the purpose of this work relies on overcoming these problems. The Cr, Mo, and W NFs in polyethylene glycol (PEG) were synthesized by laser ablation in liquid (LAL). The capability of the prepared NFs in photo-thermal conversion was investigated under 60 min solar simulator irradiation at 1 Sun and thermo-physical properties of them (SER, Etotal, E%, and B) were calculated, indicating Cr NF has the highest photo-thermal conversion efficiency (E%≅85% at its near-to-surface). The comparison of nanoparticles radius obtained with transmission electron microscopy (TEM) and the hydrodynamic radius obtained with dynamic light scattering (DLS) methods, reveals that nanoparticles were surrounded by a thick layer of PEG molecules, leading to the super-stable and long-life NFs. The effect of the nanoparticle concentration, light intensity, and consecutive heating–cooling cycles on the performance of NFs was investigated. Under 1 h sunlight illumination (∼850–960 W/m2 intensity), the surface temperature of Cr NF reaches ≅ 65 ℃, indicating the Cr NF is highly eligible for photo-thermal conversion in the real outdoor condition. The low cost and simplicity of the synthesis method, no need to use stabilizer, super durability, high-thermal stability, low rate constant of heat dissipation, and high photo-thermal conversion efficiency confirms that Cr/PEG NF can be used as potential working fluid for direct absorption solar collectors (DASCs).

LC-MS/MS Method Minimizing Matrix Effect for the Analysis of Bifenthrin and Butachlor in Chinese Chives and Its Application for Residual Study.

The matrix effect refers to the change in the analytical signal caused by the matrix in which the sample is contained, as well as the impurities that are co-eluted with the target analyte. In crop sample analysis using LC-MS/MS, the matrix effect can affect the quantification results. Chinese chives are likely to exhibit a strong matrix effect when co-extracted with bifenthrin and butachlor due to the presence of phytochemicals and chlorophyll. A novel analytical method was developed to reduce the matrix effects of bifenthrin and butachlor to a negligible level in Chinese chives. The established method had a limit of quantitation of 0.005 mg/kg and correlation coefficients greater than 0.999 within the range of 0.005-0.5 mg/kg. Matrix effects were found to be negligible, with values ranging from -18.8% to 7.2% in four different sources of chives and two leafy vegetables. Compared to conventional analytical methods for the LOQ and matrix effect, the established method demonstrated improved performances. The analytical method was further applied in a residual study in chive fields. The active ingredient of butachlor 5 granule (GR) was not detected after soil admixture application, while that of bifenthrin 1 emulsifiable concentrate (EC) showed a range from 1.002 to 0.087 mg/kg after foliar spraying. The dissipation rate constant (k) of bifenthrin was determined to be 0.115, thus its half-life was calculated to be 6.0 days. From the results, PHI and safety use standards of both pesticides were suggested. The developed analytical method can be applied to accurately determine bifenthrin and butachlor residues in Chinese chives and provides a foundation for further research on the fate and behavior of these pesticides in the environment.

Analysis and comparison of turbulence model coefficient uncertainty for canonical flow problems

The purpose of this paper is to present results of an uncertainty and sensitivity analysis study of commonly used turbulence models in Reynolds-Averaged Navier–Stokes codes due to the epistemic uncertainty in closure coefficients for a set of turbulence model validation cases that represent the structure of several canonical flow problems. The study focuses on the analysis of a 2D Zero Pressure Gradient Flat Plate, a 2D NASA Wall Mounted Hump, and an Axisymmetric Shock Wave Boundary Layer Interaction, all of which are well documented on the NASA Langley Research Center Turbulence Modeling Resource website. The Spalart–Allmaras (SA), the Wilcox (2006) κ−ω (W2006), and the Menter Shear-Stress Transport (SST) turbulence models are considered in the stochastic analyses of these flow problems, and the FUN3D code was utilized as the flow solver. The uncertainty quantification approach involves stochastic expansions based on non-intrusive polynomial chaos to efficiently propagate the uncertainty. Sensitivity analysis is performed with Sobol indices to rank the relative contribution of each closure coefficient to the total uncertainty for several output flow quantities. The results generalize a set of closure coefficients which have been identified as contributing most to the uncertainty in various output quantities of interest for the set of canonical flow problems considered in this study. Mainly, the SA turbulence model is most sensitive to the uncertainties in the diffusion constant (σ), the log layer calibration constant (κ), and the turbulent destruction constant (cw2). The predictive capability of the W2006 model is most sensitive to the uncertainties in a dissipation rate constant (σw), the shear stress limiter (Clim), and a turbulence-kinetic energy constant (β*). Likewise, the SST turbulence model was found to be most sensitive to the diffusion constants (σw1 and σw2), the log layer calibration constant (κ), and the shear stress limiter (a1).

Super-stable carbon quantum dots nanofluid for efficient solar-thermal conversion

Environmental-friendly carbon quantum dots (CQDs) nanofluid was synthesized using microwave heating of polyethyleneglycol 200 (PEG 200). PEG acts as a carbon source, base fluid and dispersant simultaneously. The synthesized CQDs were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS) and fluorescence spectroscopy. The synthesized CQDs with average diameter of 6.5 nm were solvated with PEG molecules, and consequently, the nanofluid with an excellent long-term stability was obtained. The synthesized CQDs nanofluid was used for photo-thermal conversion. The infrared thermographs showed that the surface temperature of nanofluid reaches to >60 °C after irradiation using LED lamp with 0.8 Sun irradiance for 100 min. The synthesized nanofluid was used at several consecutive heating/cooling cycles without losing its efficiency in photo-thermal conversion. Total absorbed energy, stored energy ratio, photo-thermal conversion efficiency and rate constant of heat dissipation were calculated and discussed in details. Because of stability at high temperatures (up to 200 °C), preservation of photo-thermal efficiency at consecutive heating/cooling cycles and longtime durability, the synthesized CQDs nanofluid can be considered as a super-stable nanofluid. Additionally, the performance of the CQDs nanofluid in solar energy harvesting and its application for water heating in a continuous flow system was examined. All results confirm that the synthesized CQDs nanofluid has many advantages including low cost and simplicity of preparation procedure, no need to use dispersant, long-life stability, very high thermal-stability and high photo-thermal conversion efficiency. Therefore, CQDs nanofluid has high potential to be utilized for practical solar energy harvesting.

Dissipation of the pesticides fipronil, cypermethrin, and tebuconazole in vegetables: A case study in Thua Thien-Hue province, Central Vietnam.

This study was designed to understand the dissipation of fipronil, cypermethrin, and tebuconazole in green onions and mustard greens grown in Central Vietnam. A field trial on ca. 400 m2 was implemented for two months with three different cropping regimes (natural plot—fully exposed to natural conditions; bed plot—fenced in by plastic sheets with an open roof; and protected plot—fully covered by plastic sheets) for each vegetable. A first-order kinetic model was successfully employed to interpret the dissipation data of each studied pesticide. A comparing the dissipation rate constants obtained under the same crop and growing regime between chemicals suggested that, among the chemicals examined, fipronil dissipated most readily. The pesticides were also proven to be more persistent in crops grown in protected plots than those grown in natural plots. The half-lives for fipronil, cypermethrin, and tebuconazole fluctuated, occurring at 0.4–2.2 days, 2.0–6.0 days, and 0.9–3.3 days, respectively.

Effects of temperature on the dissipation of total- and water-extractable pesticides in Japanese soils.

We investigated the dissipation of 27 pesticides in five Japanese soils at three temperatures and the variability of activation energies (Ea). The dissipation of total pesticides extracted sequentially using water and acetone was fitted to a single first-order (SFO) model. The Ea values calculated from the dissipation rate constants of the SFO model showed a normal distribution with a median of 61.1 kJ mol−1. The dissipation of water-extractable pesticides (i.e., phytoavailable pesticides) was fitted to a double first-order in parallel model with two dissipation rate constants: k1 and k2. The Ea values calculated from k1 and k2 showed normal or lognormal distribution, and the medians of the normal distribution calculated from k1 and k2 were 62.8 and 45.2 kJ mol−1, respectively. Furthermore, the method for estimating the biphasic dissipation of phytoavailable pesticides at different temperatures by using the median Ea values of the laboratory experiment was demonstrated in a field experiment.

Comparative numerical and experimental investigation of process viscometry for flows in an agitator with a flat blade turbine impeller

This paper presents a method for measuring the viscosity of generalized Newtonian fluid directly in flows generated by flat-blade turbine impellers, which are commonly used for moderate mixing and dispersion. A flat-blade turbine with four blades is defined as a model system and analyzed through numerical simulations with experimental verification. Carbopol 940 solution, a high viscosity non-Newtonian fluid with a yield stress, and a bentonite based drilling mud solution were selected as test fluids. Numerical simulation techniques for flow in agitators with a yield stress was established using the rotating coordinate system and flow solutions were validated with experiments by comparing the torque on the impeller shaft. The Metzner-Otto constant and the energy dissipation rate constant were predicted by numerical simulations using the Metzner-Otto correlation and validated via experiments. The effective viscosity that reproduces total energy dissipation rate identical to that of a Newtonian fluid was obtained from both numerical and experimental methods at different impeller speeds, from which the material viscosity curve was established as a function of the shear rate. The accuracy of viscosity prediction was compared with a rheological measurement and the average relative error was below 12% and 7% in the experiment and simulation, respectively. This method has the advantage of being able to measure the in-situ viscosity, where a drilling mud needs to transport more and heavier cuttings and careful preparation of the mud is key issue to a successful drilling process.

COMPARATIVE HYGIENIC ASSESSMENT OF PESTICIDES BEHAVIOR IN SOIL IN INTENSIVE GRAIN FARMING TECHNOLOGIES

The aim: Was the comparative hygienic evaluation of the pesticide behavior in the soil after application on cereals. Material and methods: Methods of full-scale in-field hygienic experiment, high-performance liquid (HPLC), gas-liquid (GLC), thin-layer chromatography, statistical, bibliography were used in the research. Results: Data on the detailed conditions and land parcels treated with studied pesticide formulation and its a.i. are highlighted in the article. The actual levels of the different classes a.i. content in soil and its dynamics were determined, based on which the dissipation rate constants (K) were calculated, as well as quantitative parameters of stability (τ50, τ95, τ99). Conclusions: Azoxystrobin, benzovindiflupyr, epoxiconazole, propiconazole, prochloraz, cyproconazole can be classified as of low hazardous substances, and trinexapac-ethyl, kresoxim-methyl, picoxystrobin, and tebuconazole are considered to be moderately hazardous. Among all pesticides studied, tebuconazole is the longest persists in the soil; epoxiconazole and propiconazole are most likely to disappear from the soil. Calculated values of half-lives of the studied substances in the agro-climatic conditions of Ukraine are slightly different from the results of in-field experiments that were conducted in other countries, namely: azoxystrobin, epoxiconazole, propiconazole, and cyproconazole disappear from the soil more quickly; the kresoxim-methyl and pinoxaden disappear more slowly. Meanwhile, the persistence of benzovindiflupyr, picoxystrobin, prochloraz, trinexapac-ethyl, and tebuconazole does not differ from the persistence in soils of European countries.

Dissipation kinetics of tebuconazole on Malus domestica (Golden Delicious and Jonathan) in an apple orchard from north-eastern Romania

Tebuconazole (TEB) dissipation behavior on Golden Delicious and Jonathan leaf, bark, peel and flesh apple samples was investigated in the present work. The interest fungicides were sequentially applied as a spray in four foliar applications, in full agreement with an apple orchard-protection program recommended by Bayer. For studying TEB dissipation, apple tree related samples were collected in advance (reference) and as soon as applications dried out (3 h), and then at 2, 5, 7.5, 10, and 15 day after the treatment. Reference apple tree samples were analyzed by gas chromatography tandem mass spectrometry for their corresponding chemical and phytochemical composition. Tebuconazole dissipation on apple leaf, bark and peel could be adequately described by a single first-order kinetic model. In apple flesh samples traces of TEB were not detected. Higher TEB dissipation rate constant was observed in apple leaf than in peel and bark apple samples. The half-life time of TEB varies in the 2.71–16.03 d range and might reach a critical value of 1 d under the most reactive circumstances. The results obtained in the present study show that the dissipation parameters are sensitive to the composition of used combined fungicide formulations and also to their corresponding applied dose.

Enantioselective degradation and bioaccumulation of sediment-associated fipronil in Lumbriculus variegatus: Toxicokinetic analysis

Enantioselective degradation and biotransformation are critical processes affecting the bioaccumulation and toxicity of chiral pesticides in the environment. In the present study, enantioselective uptake, biotransformation and elimination of a current use pesticide, fipronil in a benthic invertebrate, Lumbriculus variegatus were assessed using a sediment bioaccumulation test. Toxicokinetic models were constructed to quantitatively describe kinetic processes of fipronil enantiomers. The degradation of fipronil in sediment significantly affected chemical uptake, thus degradation kinetic model was incorporated into toxicokinetic modeling. It was shown that S-(+)-fipronil degraded faster than R-(−)-fipronil in sediment, with dissipation rate constants being 0.090 ± 0.008 and 0.023 ± 0.006 1/d, respectively. As a result, R-(−)-enantiomer preferentially accumulated in sediment over time. Similarly, higher concentrations of R-(−)-fipronil were detected in L. variegatus compared with S-(+)-fipronil. Toxicokinetic modeling showed R-(−)-fipronil had larger uptake and elimination rate coefficients and apparent maximum reaction rate, but a smaller apparent half-saturation constant than S-(+)-fipronil. Preferential uptake of R-(−)-fipronil from sediment to L. variegatus was the main reason for greater R-(−)-fipronil concentrations in organism. Biotransformation of fipronil in L. variegatus was also enantioselective, yet it played fewer roles on enantioselective bioaccumulation than uptake. Overall, our findings highlight the importance of selective degradation, uptake and biotransformation of sediment-associated fipronil on its enantioselective bioaccumulation in benthic invertebrates, which helps to improve the accuracy for assessing aquatic toxicity of the chiral pesticide. CapsuleEnantioselective bioaccumulation of sediment-associated fipronil in Lumbriculus variegatus was quantitatively explained by selective degradation, uptake, biotransformation and elimination parameters using a combination of degradation and toxicokinetic modeling.

Influence of organic amendments on dissipation kinetics of two different pesticides in soil: a case study

ABSTRACTA study was undertaken to investigate the remedial effect of some soil amendments (farmyard manure (FYM), press mud compost (PMC), cereal straw (CS) at 5 t ha−1 and fresh cow dung slurry (FCD) @ 0.5 t ha−1) on dissipation kinetics of imidacloprid and sulfosulfuron under laboratory conditions. Incorporation of CS or FCD was found to be most effective in degrading both the pesticides at faster rates. Dissipation of both the pesticides could be well accounted by two component (1 + 1) first order kinetics. The computed values of parameters revealed that use of organic amendments increased the dissipated fraction of imidacloprid and sulfosulfuron. Incorporation of CS or FCD in soil maintained relatively higher dissipation rate constants for both faster and slower dissipation processes of pesticides in comparison to control. Hence, eco-friendly practices of CS or FCD incorporation as soil amendment in soil can play a vital role in preventing soil and water pollution.

Assessment of the environmental fate of endocrine disrupting chemicals in rivers

Laboratory tests were conducted with five endocrine disruptors (bishenol A, triclosan. nonylphenol, nonylphenol monoethoxylate and nonylphenol diethoxylate) under different redox conditions (aerobic, anoxic, anaerobic and sulfate-reducing conditions) to assess abiotic and biotic degradation in a river water/sediment system. The river water sample was collected from Spercheios River while the sediment was collected from the banks of a tributary of the river at the point where the discharge point of a wastewater treatment plant is located. To describe quantitatively elimination kinetics of the target compounds, pseudo first-order kinetics were adopted. According to the results from the microcosms studies, it can be stated that the substances are eliminated from the aqueous phase with relatively high rates under aerobic conditions due to both sorption and biotransformation processes. However, when reduced oxygen conditions were established in the microcosms incubations, biotransformation decreased, indicating the almost complete cease of the EDCs microbial degradation, while substances' sorption onto sediments showed no significant differences. All compounds were found to be biodegradable under aerobic conditions, and the low to high order of the calculated dissipation rate constants was 0.064±0.004d−1 (TCS)→0.067±0.006d−1 (NP)→0.076±0.009d−1 (NP2EO)→0.081±0.007d−1 (NP1EO)→0.103±0.011d−1 (BPA). Finally, regarding the biotransformation experiments, the elimination of the compounds limited in the absence of oxygen as compared to aerobic.

Phytoremediation of organochlorine and pyrethroid pesticides by aquatic macrophytes and algae in freshwater systems

ABSTRACTExtensive use of Pesticides in agriculture and its surface runoff in river water is a major environmental concern. The present study evaluated the phytoremediation potential of Eichornia crassipes, Pistia strateotes and algae (Chaetomorpha sutoria, Sirogonium sticticum and Zygnema sp.) for organochlorine and pyrethroid pesticides. Water and plant samples were extracted by liquid phase and solid phase extraction respectively and analyzed by high-performance liquid chromatography. Eleven treatments (T1–T11) with and without plants were used for phytoremediation of organochlorine and pyrethroid pesticides. During the experiment, P. strateotes, E. crassipes and algae (C. sutoria, S. sticticum and Zygnema sp.) showed the highest removal efficiency with 62 (71% root, 29% shoot), 60 (67% root, 33% shoot), and 58% respectively for organochlorine and 76 (76% root, 24% shoot), 68 (69% root, 31% shoot), and 70% respectively for pyrethroids for the respective aquatic plants. Dissipation rate constant of treatments with plants (T2, T3, T5, T6, T8, and T9) was significantly higher (p < 0.05) as compared to that of treatments without plants (T10 and T11, control) for both organochlorine and pyrethroid. The bioconcentration factor of pyrethroid treatments (T3, T6, and T9) was significantly higher (p < 0.05) as compared to that of organochlorine treatments (T2, T5 and T8). The removal efficiency of E. crassipes, P. strateotes and algae (C. sutoria, S. sticticum and Zygnema sp.) for pyrethroids was significantly higher (p < 0.01) as compared to that of organochlorine.

Fate and effect of imidacloprid on vermicompost-amended soils under dissimilar conditions: Risk for soil functions, structure, and bacterial abundance.

The fate and impact of pesticide on soil depend partly on the agricultural practices, such as prior treatment with pesticide and/or organic amendments. As a means of determining how the previous soil conditions can affect the fate of imidacloprid (IMI) and its effect on soil functions, experiments were made with soil samples, double-amended or not with either vine-shoot (W) or olive cake (O) vermicompost or contaminated or not with IMI. These soil samples, incubated for 3months, were placed in two microcosms (M1 with the pre-amended soils and M2 with the pre-exposed soils), treated with IMI and amended with vermicomposts and then incubated for 3months. The IMI distribution on soil fractions, sorption processes, dissipation kinetics, and biochemical as well as genetic structure and bacterial abundance were determined to assess the fate and impact of IMI on the soil. The addition of W vermicompost to the soil reduced the IMI availability. The dissipation kinetic in soils from M1 and M2 followed, respectively, a single first-order and a double first-order in parallel models. The lowest IMI persistence corresponded to the soil from M2 amended with O-vermicompost with DT50 and DT90 values of 67d and 265d, while in the other soils 90% dissipation required >512d. The vermicomposts-amended contaminated soils increased the dehydrogenase activity by 2- and 4-fold respect the control soils. However, the urease activity decreased due to the IMI influence. The changes in the bacterial community in the contaminated soil amended with O-vermicompost during incubation were correlated with the dissipation rate constant of IMI, suggesting a better tolerance of microorganisms to IMI. Thus, in the soil contaminated with IMI, the amendment with the vermicompost from olive cake can mitigate the impact of this insecticide on soil functions and promote its depuration capability while minimizing environmental risks.

Dissipation of Antimicrobials in Feedlot Manure Compost after Oral Administration versus Fortification after Excretion.

Fortification of manure with antimicrobials is one approach to studying their dissipation. However, fortified antimicrobials may not accurately model dissipation that occurs after antimicrobials have been administered to livestock in feed and excreted in manure. This study examined the dissipation of antimicrobials excreted in manure versus those added directly to manure (fortified). Steers were fed a diet containing (kg feed) (i) 44 mg chlortetracycline, (ii) 44 mg each of chlortetracycline and sulfamethazine, (iii) 11 mg tylosin, and (iv) no antimicrobials (control). Fortified antimicrobial treatments were prepared by adding antimicrobials to control manure. Manure was composted for 30 d, sampled every 2 to 3 d, and analyzed for antimicrobials and compost properties. Antimicrobial dissipation followed first-order kinetics. The dissipation rate constant was significantly greater (based on 95% confidence limit) for excreted (0.29-0.54 d) than for fortified chlortetracycline (0.11-0.13 d). In contrast, dissipation rate constants were significantly greater for fortified sulfamethazine (0.47 d) and tylosin (0.31 d) than when the same antimicrobials were excreted (0.08 and 0.07 d, respectively). On average, 85 to 99% of the initial antimicrobial concentrations in manure were dissipated after 30 d of composting. The degree of dissipation was greater ( < 0.0001) for fortified (99%) than for excreted tylosin (85%). Composting can be used to reduce environmental loading of antimicrobials before field application of beef cattle manure. Dissipation rates of fortified antimicrobials during manure composting may not accurately reflect those of antimicrobials that are consumed and excreted by cattle.

Biodegradation, Biosorption of Phenanthrene and Its Trans-Membrane Transport by Massilia sp. WF1 and Phanerochaete chrysosporium.

Reducing phenanthrene (PHE) in the environment is critical to ecosystem and human health. Biodegradation, biosorption, and the trans-membrane transport mechanism of PHE by a novel strain, Massilia sp. WF1, and an extensively researched model fungus, Phanerochaete chrysosporium were investigated in aqueous solutions. Results showed that the PHE residual concentration decreased with incubation time and the data fitted well to a first-order kinetic equation, and the t1/2 of PHE degradation by WF1, spores, and mycelial pellets of P. chrysosporium were about 2 h, 87 days, and 87 days, respectively. The biosorbed PHE was higher in P. Chrysosporium than that in WF1, and it increased after microorganisms were inactivated and inhibited, especially in mycelial pellets. The detected intracellular auto-fluorescence of PHE by two-photon excitation microscopy also proved that PHE indeed entered into the cells. Based on regression, the intracellular (Kdin) and extracellular (Kdout) dissipation rate constants of PHE by WF1 were higher than those by spores and mycelial pellets. In addition, the transport rate constant of PHE from outside solution into cells (KinS/Vout) for WF1 were higher than the efflux rate constant of PHE from cells to outside solution (KoutS/Vin), while the opposite phenomena were observed for spores and mycelial pellets. The amount of PHE that transported from outside solution into cells was attributed to the rapid degradation and active PHE efflux in the cells of WF1 and P. Chrysosporium, respectively. Besides, the results under the inhibition treatments of 4°C, and the presence of sodium azide, colchicine, and cytochalasin B demonstrated that a passive trans-membrane transport mechanism was involved in PHE entering into the cells of WF1 and P. Chrysosporium.

Effects of light-emitting diode supplementary lighting on the winter growth of greenhouse plants in the Yangtze River Delta of China.

BackgroundThe winter in the Yangtze River Delta area of China involves more than 1 month of continuous low temperature and poor light (CLTL) weather conditions, which impacts horticultural production in an unheated greenhouse; however, few greenhouses in this area are currently equipped with a heating device. The low-cost and long-living light-emitting diode (LED) was used as an artificial light source to explore the effects of supplementary lighting during the dark period in CLTL winter on the vegetative characteristics, early yield, and physiology of flowering for pepper plants grown in a greenhouse without heating. Two LED lighting sets were employed with different light source to provide 65 μmol m−2 s−1 at night: (1) LED-A: red LEDs (R, peak wavelength 660 nm) and blue LEDs (B, peak wavelength 460 nm) with an R:B ratio of 6:3; and (2) LED-B: R and B LEDs at an R:B ratio of 8:1. Plants growth parameters and chlorophyll fluorescence characteristics were compared between lighting treatments and the control group.ResultsPlants’ yield and photosynthesis ability were improved by LED-A. Pepper grown under the LED-A1 strategy showed a 303.3 % greater fresh weight of fruits and a 501.3 % greater dry mass compared with the control group. Plant leaves under LED-A1 showed maximum efficiency of the light quantum yield of PSII, electron transfer rate, and the proportion of the open fraction of PSII centers, with values 113.70, 114.34, and 211.65 % higher than those of the control group, respectively, and showed the lowest rate constant of thermal energy dissipation of all groups. LED-B was beneficial to the plant height and stems diameter of the pepper plants more than LED-A.ConclusionsThese results can serve as a guide for environment control and for realizing low energy consumption for products grown in a greenhouse in the winter in Southern China.

Rapid photodegradation of clethodim and sethoxydim herbicides in soil and plant surface model systems

Photolysis is an important degradation process to consider when evaluating the persistence of a pesticide in the field. In this work, photolytic behavior of clethodim and sethoxydim herbicides under simulated solar radiation was examined in organic solvents, on glass disk and silica gel plates as leaf and soil model surfaces. The photodegradation was characterized by determination of their half-lives (t1/2), dissipation rate constant (k) and identification of degradation products by means of HPLC-Qtof-MS. Photolytic degradation of clethodim and sethoxydim was very rapid. The photodegradation rate was enhanced in leaf model than in water with half-lives that ranged from 6.3±0.5 to 10.1±0.4min for clethodim and from 8.0±0.3 to 20.5±0.5min for sethoxydim. The fastest rate of degradation was obtained on silica gel plates with half-lives of 1.8 and 5.0min for clethodim and sethoxydim respectively. Photoreduction of the oxime ether moiety was the main transformation processes giving rise to a photostable product, the corresponding dealkoxylated derivative. Isomerization of oxime ether bond and oxidation of sulfur atom to form Z-isomer and the corresponding sulfoxides were the others reactions involved. The different environments tested influenced the concentrations of photoproducts formed during the irradiation of both herbicides. This result suggests that photolysis will be an important pathway of dissipation of the two herbicides. On the basis of these findings, further studies could be desirable to estimate the effects of transformation products on the environment.