Insight into the effect of microplastics on the adsorption and degradation behavior of thiamethoxam in agricultural soils.

Thiamethoxam and microplastics are both common pollutants in farmland soil; however, few studies have focused on the interaction between thiamethoxam and microplastics in soil. Here, a batch experiment and soil incubation experiment were performed to explore the mechanism and effects of microplastics on the adsorption and degradation behaviors of thiamethoxam in soil, respectively. First, the batch experimental results indicated that the adsorption process of thiamethoxam on the microplastic/soil mixtures and soil-only systems mainly relies on chemical interactions. All sorption processes had moderate intensities of adsorption, and the sorption process occurred on the heterogeneous surface. In addition, the particle size and dose of microplastics could both affect the adsorption behavior of thiamethoxam onto microplastics/soil systems. The sorption capacity of thiamethoxam in soil decreases as the particle size of microplastics increases, but the sorption capacity increases as the dose of microplastics increases. Second, the results of the soil incubation experiment showed that the half-lives of thiamethoxam ranged from 57.7 d to 86.6 d, from 86.6 d to 173.3 d, and 115 d in the biodegradable microplastic/soil systems, nondegradable microplastic/soil systems, soil-only systems, respectively. These results indicate that biodegradable microplastics promoted the degradation of thiamethoxam, while nondegradable microplastics delayed the degradation process of thiamethoxam in soil. Overall, microplastics could change the degradation behaviors, sorption capacity and adsorption efficiency, and then affect the mobility and persistence of thiamethoxam in the soil environment. These findings contribute to understanding the influence of microplastics on the environmental fate of pesticides in the soil environment.

Simulation and Prediction of Fungal Community Evolution Based on RBF Neural Network.

Simulation and prediction of the scale change of fungal community. First, using the experimental data of a variety of fungal decomposition activities, a mathematical model of the decomposition rate and the relationship between the bacterial species was established, thereby revealing the internal mechanism of fungal decomposition activity in a complex environment. Second, based on the linear regression method and the principle of biodiversity, a model of fungal decomposition rate was constructed, and it was concluded that the interaction between mycelial elongation and moisture resistance could increase the fungal decomposition rate. Third, the differential equations are used to quantify the competitive relationship between different bacterial species, divide the boundaries of superior and inferior species, and simulate the long-term and short-term evolution trends of the community under the same initial environment. And an empirical analysis is made by taking the sudden change of the atmosphere affecting the evolution of the colony as an example. Finally, starting from summer, combining soil temperature, humidity, and fungal species data in five different environments such as arid and semiarid, a three-dimensional model and RBF neural network are introduced to predict community evolution. The study concluded that under given conditions, different strains are in short-term competition, and in the long-term, mutually beneficial symbiosis. Biodiversity is important for the biological regulation of nature.

The effect of microplastics on behaviors of chiral imidazolinone herbicides in the aquatic environment: Residue, degradation and distribution.

The pollution of aquatic environments by microplastics and herbicides has become a global concern. This study was focused on imazamox, imazapic, and imazethapyr sorption to polypropylene microplastics in water. And the potential effects of microplastics on herbicide enantiomer degradation and distributions in water, sediment, and water-sediment microcosms were investigated. Adsorption experiment results indicated that herbicide sorption to microplastics involved both chemisorption and physical adsorption. Degradation experiment results indicated that microplastics could markedly increase herbicide persistence in water and sediment. Marked stereoselective degradation was not found for the three herbicides in water and sediment, but stereoselective degradation of imazapic in water containing microplastics was found. The water-sediment microcosms experiment results indicated that microplastics have significant effect on stereoselectivity degradation and distribution in water and water-sediment microcosms for imazapic, and have little effect on stereoselectivity behaviors of imazamox and imazethapyr in water-sediment systems. Furthermore, the microcosm experiment results also indicated that herbicides can partition between water and microplastics and that microplastics could affect herbicide persistence and distributions in aquatic environments. The present study provides new insights into the fate of chiral pollutants in aquatic environments containing microplastics, and contributes to understanding behaviors of herbicides and microplastics in aquatic environments.

Insight into the adsorption mechanisms of ionizable imidazolinone herbicides in sediments: Kinetics, adsorption model, and influencing factors.

To reveal the adsorption mechanisms of imazamox, imazapic, and imazethapyr on sediment and batch experiments were carried out in this study. The adsorption kinetics of three imidazolinone herbicides on sediment were accurately described by the pseudo-second-order kinetic model(R2 > 0.9004). The values of adsorption capacity (Qe.cal) were ranged from 0.0183 to 0.0859 mg kg-1 for three herbicides. Adsorption equilibrium was reached within 24 h for three herbicides on sediment, and well fitted by the Freundlich model(R2 > 0.9561). The KF of values for adsorption obtained sediment samples were ranged from 0.2501 to 1.322 L1/n mg1-1/n kg-1for three herbicides. These results indicated that intraparticle diffusion and external mass transport were the main rate controlling steps of the adsorption of herbicides on sediment and that the chemical adsorption was dominant during the adsorption processes. The calculated hysteresis coefficient H were 0.9422,0.7877 and 0.744 for imazmox, imazapic and imazethapyr in raw sediment, respectively, indicating that there is a hysteresis in desorption. The influences of solution pH and sediment organic carbon content on the imidazolinone herbicide adsorption behaviors were also examined. Which shown that the adsorption process for herbicides was highly pH-dependent and adsorption efficiency was closely related to the organic matter content of the sediment, suggesting that electrostatic interactions played crucial roles in the adsorption behavior between sediment and imidazolinone herbicides, and the herbicides were mostly absorbed by the amorphous materials of sediment. These research findings are important for assessing the fate and transport of imidazolinone herbicides in water-sediment systems.

Simultaneous determination of tiafenacil and its six metabolites in fruits using ultra-high-performance liquid chromatography/tandem mass spectrometry.

A simple and reliable analytical method was established for the simultaneous determination of tiafenacil and its six metabolites in fruits. The method involves three steps: extraction using acidified acetonitrile, clean-up by octadecylsilane(C18) and graphitized carbon black (GCB), and detection using liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS). The method was validated on seven matrices spiked at 10, 100 and 1000 µg kg-1. Average recoveries ranged from 73% to 105% with intra-day RSDr (n = 5) of 1.0%-13.0% and inter-day RSDR (n = 15) of 1.1%-14.6%. Good linearities (R2 > 0.9911) were obtained for seven analytes in all matrices. The limit of quantification (LOQs) for tiafenacil and its six metabolites were 10 µg kg-1 in all matrices. This analytical method provides a basis for the establishment of maximum residue limits (MRL) and for the monitoring of tiafenacil residues in fruits.

Behavior of imidazolinone herbicide enantiomers in earthworm-soil microcosms: Degradation and bioaccumulation.

Imidazolinone herbicides are a group of chiral herbicides that are widely used to control weeds in crops. Despite their wide use, few studies on the behavior of enantiomers in terrestrial systems have been reported. In this study, the bioaccumulation of imazamox, imazapic, and imazethapyr enantiomers in earthworm and their degradation in soils were assessed using earthworm-soil microcosms. The bioaccumulation of the three herbicides in earthworm was not significantly enantioselective. Imazamox and imazethapyr did not significant stereoselective degradation in soil (p > 0.05), while the enantioselectivity of the degradation of imazapic was significant (p < 0.05). Furthermore, biota to soil accumulation factor (BSAF) values were also calculated for three herbicides. Relationships between BSAF values and organic matter content of soil and log KOW of herbicides were investigated. The BSAFs values were negatively correlated with the log KOW of herbicides, and were positively correlated with organic matter content of soil in earthworm-soil microcosms. These relationships indicated that chemical hydrophobicity (Kow) and organic matter content of soil were good predictors to estimate the bioavailability of imidazolinone herbicides to earthworm.

Simultaneous analysis of indaziflam and its metabolites in pitaya using dispersive solid phase extraction coupled with liquid chromatography coupled with tandem mass spectrometry.

A simple and efficient multiresidue method using dispersive solid phase extraction and liquid chromatography coupled with tandem mass spectrometry was developed for the targeted analysis of indaziflam and its five metabolites (indaziflam-diaminotriazine, indaziflam-carboxylic acid, indaziflam-triazine indanone, indaziflam-hydroxyethyl, and indaziflam-olefin) in pitaya samples (including roots, plants, flowers, peels, pulp, and whole fruit). The analytes were extracted with acetonitrile, and the extracts were purified using multiwalled carbon nanotubes. The method was validated using pitaya samples spiked at 0.5, 5, and 50 µg/kg, and the average recoveries varied from 61.1 to 103.7% with relative standard deviations lower than 12.7% (n = 5). This method exhibited sufficient linearity within the concentration range of 0.1-100 µg/L. The limits of detection and quantification were in the ranges of 0.001-0.1 and 0.003-0.3 µg/kg, respectively. The method was successfully applied to analyze pitaya samples in Nanning, and no indaziflam or its metabolites were detected in the samples analyzed.

Computational study on the mechanism and kinetics for the reaction between HO2 and n-propyl peroxy radical.

The n-propyl peroxy radical (n-C3H7O2) is the key intermediate during atmospheric oxidation of propane (C3H8) which plays an important role in the carbon and nitrogen cycles in the troposphere. In this paper, a comprehensive theoretical study on the reaction mechanism and kinetics of the reaction between HO2 and n-C3H7O2 was performed at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-311G(d,p) level of theory. Computational results show that the HO2 + n-C3H7O2 reaction proceeds on both singlet and triplet potential energy surfaces (PESs). From an energetic point of view, the formation of C3H7O2H and 3O2 via triplet hydrogen abstraction is the most favorable channel while other product channels are negligible. In addition, the calculated rate constants for the title reaction over the temperature range of 238-398 K were calculated by the multiconformer transition state theory (MC-TST), and the calculated rate constants show a negative temperature dependence. The contributions of the other four reaction channels to the total rate constant are negligible.

Method Development and Validation of Indaziflam and Its Five Metabolites in Soil, Water, and Fruits by Modified QuEChERS and UHPLC-MS/MS.

A method for simultaneously determining indaziflam and its five metabolites in soil, water, and fruits using ultraperformance liquid chromatography/tandem mass spectrometry was established. The analytes were eluted in <4.5 min. Positive electrospray ionization mode was used. The analytes were extracted using acetonitrile containing 1% ammonium hydroxide, and then the extracts were purified using octadecylsilane and PRiME HLB cartridges. The quantification limits were 0.01-1.01 µg kg-1. The linearities of the calibrations for all analytes were excellent ( R2 > 0.9952). The recoveries at spike concentrations of 0.01, 0.1, and 1 mg kg-1 were 81.3-112.1%. The intraday and interday relative standard deviations were <13.5% and <12.3%, respectively. The method was successfully used to determine indaziflam and its five metabolites in samples from markets and fields. The results confirmed that the method is an effective and robust procedure for routinely determining indaziflam and its metabolites in soil, water, and fruit samples.

Cleavage of Unstrained C-C Bonds in Acenes by Boron and Light: Transformation of Naphthalene into Benzoborepin.

Naphthalene and acenaphthene with peri 2-py and BMes2 (py=pyridyl, Mes=mesityl) substituents have been found to undergo facile phototransformation, cleavage of a C-C bond of naphthalene, and formation of 2-py-bound benzoborepins as the major products. Mechanistic pathways of this photoreaction have been established by examination of both excited and ground states by using CASSCF and CASPT2 methods in DFT and time-dependent DFT calculations. The mesityl to py-naphthyl charge-transfer transition and the mesityl migration from the boron atom to the naphthyl moiety drive this unprecedented C-C bond cleavage and boron-insertion reaction.

Triaryl-Boron Functionalized Dinuclear Platinum Complexes Linked by Photoisomerizable Bpe Ligand: Luminescence and Isomerism.

We report herein a series of triarylboron-functionalized Pt(II) dinuclear complexes using a photoactive bis(4-pyridyl)ethylene (bpe) bridging unit. The new Pt(II) complexes display phosphorescence at both room temperature and 77 K. Depending on the conditions under which crystals of the complexes were grown, either the cis- or trans-isomers could be obtained. The trans and cis isomers were found to undergo light-induced isomerization in solution with the trans isomer being the dominant species.

Characterization of the fate and distribution of ethiprole in water-fish-sediment microcosm using a fugacity model.

A novel, relatively simple and effective three-compartment level IV fugacity model was developed to quantitatively describe the fate, transformation and transport of ethiprole in an aquatic system. Chemical equilibrium was assumed to apply within each bulk compartment. Expressions are included for degradation reactions, advective flow, emission, and interphase transport by non-diffusive and diffusive processes. The simulated results closely matched the results obtained from the experiments. The model indicated that at 25°C (day:night=12h:12h), after approximately 672h, Results of the model calculations showed that the ethiprole was degraded by both photolysis and microorganisms in the water accounts for 86.8% (account for 90.4%, 95.4% in Beijing (BJ) and Hunan (HN) microcosm respectively) of the total removal, the ethiprole was removed by advective outflow accounts for 0.15% (accounts for 0.05%, 0.1% in HN and BJ microcosm respectively) of the total removal, the ethiprole were removed by biodegradation in sediment and fish, accounts for 8.54% and 5.55% (accounts for 2.52% and 2.03%, 5.6% and 3.7% in HN and BJ microcosm respectively) of the total removal respectively in HLJ microcosm. It indicates that biodegradation and photolysis in the water phase were the most important removal process, and most of the ethiprole was distributed in the water phase. A sensitivity analysis of the input parameters indicates that the Henry's law constant (H) and octanol-water partition coefficient (Kow) parameters are the both most sensitive to the ethiprole concentration in the medium, which suggests that the H and Kow have important impact on both the distribution and variance of the contaminant concentration. The mass balance under steady-state conditions showed that over 90% of ethiprole stay in water for all microcosm. This finding demonstrates that water plays a key role in the fate of ethiprole, acting as the major sink for contaminants in the stimulation system.

Chemometric-assisted QuEChERS extraction method for the residual analysis of thiacloprid, spirotetramat and spirotetramat's four metabolites in pepper: Application of their dissipation patterns.

Chemometric tools equipped with a Plackett-Burman (P-B) design, a central composite design (CCD) and a desirability profile were employed to optimise the QuEChERS (quick, easy, cheap, effective, rugged and safe) method for the quantification of thiacloprid, spirotetramat and spirotetramat's four metabolites in pepper. The average recoveries were in the range of 71.6-119.5%, with relative standard deviations ⩽ 12.1%. The limit of quantification for the method was less than 0.01 mg/kg. The method was applied to field samples to evaluate the residual characteristics of thiacloprid and spirotetramat. The data showed that the first+first-order model is a better fit than the first order model for the dissipation of thiacloprid and spirotetramat in pepper. The half-lives of thiacloprid and spirotetramat in pepper are 0.81 and 1.21 days, respectively. The final residues were between 0.016 mg/kg and 0.13 mg/kg for thiacloprid and 0.08 mg/kg and 0.12 mg/kg for spirotetramat.

Influx-Operated Ca(2+) Entry via PKD2-L1 and PKD1-L3 Channels Facilitates Sensory Responses to Polymodal Transient Stimuli.

The polycystic TRP subfamily member PKD2-L1, in complex with PKD1-L3, is involved in physiological responses to diverse stimuli. A major challenge to understanding whether and how PKD2-L1/PKD1-L3 acts as a bona fide molecular transducer is that recombinant channels usually respond with small or undetectable currents. Here, we discover a type of Ca(2+) influx-operated Ca(2+) entry (ICE) that generates pronounced Ca(2+) spikes. Triggered by rapid onset/offset of Ca(2+), voltage, or acid stimuli, Ca(2+)-dependent activation amplifies a small Ca(2+) influx via the channel. Ca(2+) concurrently drives a self-limiting negative feedback (Ca(2+)-dependent inactivation) that is regulated by the Ca(2+)-binding EF hands of PKD2-L1. Our results suggest a biphasic ICE with opposite Ca(2+) feedback regulation that facilitates sensory responses to multimodal transient stimuli. We suggest that such a mechanism may also occur for other sensory modalities and other Ca(2+) channels.

Determination of ametoctradin residue in fruits and vegetables by modified quick, easy, cheap, effective, rugged, and safe method using ultra-performance liquid chromatography/tandem mass spectrometry.

A rapid, effective and sensitive method to quantitatively determine ametoctradin residue in apple, cucumber, cabbage, tomato and grape was developed and validated using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS). The target compound was determined in less than 5.0 min using an electrospray ionisation source in positive mode (ESI+). The limit of detection was below 0.043 µg kg(-1), whereas the limits of quantification did not exceed 0.135 µg kg(-1) in all five matrices. The method showed excellent linearity (R(2)>0.9969) for the target compound. Recovery studies were performed in all matrices at three spiked levels (1, 10 and 100 µg L(-1)). The mean recoveries from five matrices ranged from 81.81% to 100.1%, with intra-day relative standard deviations (RSDr) in the range of 0.65-7.88% for the test compound. This method will be useful for the quick and routine detection of ametoctradin residues in potato, grape, cucumber, apple and tomato.

Designer D-form self-assembling peptide nanofiber scaffolds for 3-dimensional cell cultures.

Traditional 2-D cell cultures have many limitations because they do not truly mimic the natural environment. In order to fully understand the in vivo 3-D environment, it is crucial to develop a biomimetic 3-D culture system. Recently progress toward 3-D tissue cell cultures has been gradually made by addressing many critical issues including the microenvironment, gradient diffusion and apoptosis. Here we report a D-form self-assembly peptide system that provides insight into the relationships between nanofiber scaffolds and cell behaviors in 3-D cell cultures. We observed the peptide secondary structures response to ions and confirmed that their participation increases mechanical force rapidly. We also showed the enzymes attachment to nanofibers, investigated scaffolds to form 3-D microenvironment and described a modified protocol for 3-D cell culture D-form self-assembly peptide. Using this protocol, we showed cell behavior in the D-form peptide with high cell viability and low-level cell apoptosis for weeks. Furthermore, we proposed a plausible model for chiral self-assembly peptides in 3-D culture. Our research may further stimulate others to design novel biological materials at single chiral amino acid level, and may broaden the applications of designer D-form self-assembling peptides in clinical and medical nanobiotechnology.