Residue analysis and dissipation of monosulfuron in soil and wheat

HPLC-UV residue analytical method for monosulfuron [N-[( 4' -methyl) pyrimidin- 2' -yl]-2-nitrophenylsulfonyl urea] in soil and wheat was developed. Monosulfuron residues were recovered by solvent extraction, followed by liquid-liquid partition, and C 18 cartrige clean-up. Excellent method recoveries ranging from 95%—104% for both fortified soil and wheat grain were obtained with coefficients of variation 1.5%—11.8%. The minimum detectable quantities in soil and wheat were both 4 ng, the limit of detection was 0.02 mg/kg. When monosulfuron was applied according to double dosage of maximum recommended use direction(120 g ai/hm 2 of 10% monosulfuron wettable powder sprayed for once during development of wheat) in field studies conducted in Shandong Province and near Beijing, monosulfuron residues was not detected in soil and wheat samples collected 75 d after application. Laboratory soil degradation studies showed that monosulfuron degraded faster in acidic soil and strong alkaline soil than in neutral or weak alkaline soil. Half lives in Jiangxi soil, Shijiazhuang soil, Jiangsu soil and Heilongjiang soil were 41, 48, 87 and 84 d respectively. Monosulfuron residues dissipated rapidly in Shandong and Beijing field test sites with half-lives of less than 14 d.

Residue analysis and dissipation of a new fungicide 2-allylphenol in tomato

The method of residue analysis of a new synthesized fungicide 2-allylphenol was studied by simulating the active compound structure in Gingko tree(Gingko biloba L.) and its dissipation rate and terminal residue levels in tomato under field condition. Residues of 2-allylphenol were extracted from tomato matrix with acetone, purified by liquid-liquid extraction and Florisil cartrieges, and then determined by HPLC with UV-detector. The minimum detectable amount of 2-allylphenol was 3×10 -9 g, the minimum detectable concentration of 2-allylphenol in the samples of tomato were 0.01 mg/kg. The ranges of average recoveries and coefficient variation of the method were 87.7%—90.2% and 1.25%—2.06%, respectively. The dissipation rate and terminal residue levels in tomato were determined with the method described above. The results showed that the half-life of 2-allylphenol in tomato was 6.37 d, and 2-allylphenol declined with 82.6% of the initial deposit remaining in tomato at harvest. The terminal residue levels in tomato were 0.15 mg/kg and 0.20 mg/kg following the recommended doses and time intervals.

Residue Analysis of 55% MCPA·ametryn·diuron WP

The digestion regularity of MCPA, ametryn and dim＇on which were the active ingredients of 55% MCPA · ametryn · diuron WP in sugarcane leaves and soil of sugarcane plantation collected from Changsha of Hunan Province and Haikou of Hainan Province in 2009 and 2010were studied in the paper, and the results showed that these three agents had rapid digestion. The final residue test showed that beth MCPA and ametryn had not been detected in the study; the average resi- dues of diuron in the soil collected from Hunan Province in 2009 and 2010 were 0.018 and 0.015 mg/kg, respectively which were slightly larger than the critical value of 0. 013mg,/kg; diuron had no been detected in other treatments.

Method for Analysis of Ethephon Residue in Walnuts

[Objectives] This study was conducted to establish an analytical method for the determination of ethephon residue in walnuts by UPLC-MS/MS. [Methods] This study was conducted to establish an analytical method for the determination of ethephon residue in walnuts by UPLC-MS/MS. [Results] The limit of quantification was 0.1 mg/kg and the recoveries were 94%-105% with the relative standard deviations of 0.82%-2.64% at the spiked levels of 0.1-5.0 mg/kg. [Conclusions] The accuracy and sensitivity of the method meet the requirements of pesticide residue analysis, and the experimental method is simple to operate.

Study on Analytical Method of Endosulfan Residue in Apple

This study was conducted to establish an analytical method for endosulfan residue in apple. Samples were extracted with 30 ml of acetone ： ethyl acetate （9：1）, purified with FlorisiL （containing activated carbon）, and detected by GC. Under those detection conditions, the detection limits of α-endosulfan, 15-endosulfan and endosulfate were 10^-11, 10^-11, and 2.5×10^-11 g, respectively. The recoveries of α-en- dosulfan were in the range of 89.49%-95.34%, with CVs in the range of 1.45%- 2.69%; the recoveries of β-endosulfan were in the range of 99.35%-100.63%, with CVs in the range of 1.39%-4.72%; and the recoveries of endosulfan suffate were in the range of 95.32%-101.15%, with CVs in the range of 1.19%-3.21%. The accu- racy, precision and sensitivity of the method all satisfy the requirements of pesticide residue analysis.

Analysis of α, β, γ-hexachlorocyclohexanes in water by novel activated carbon fiber-solid phase microextraction coupled with gas chromatography—mass spectrometry

A fast and simple method for determination of α, β, γ-hexachlorocyclohexanes (HCHs) in water using activated carbon fiber-solid phase microextraction(ACF-SPME) were studied. Results showed the performance of adsorption and desorption of three HCHs on ACF were excellent. A wide linear range from 10 to 100 μg/L and detection limits of the ng/L level were obtained using ACF-SPME with GC-MS in selected ion monitoring(SIM) acquisition mode. The proposed method was also successfully applied for determination of three HCHs in tap water. Compared to commercial fibers, ACF showed some advantages such as better resistance to solvents, higher thermal stability, longer lifetime and lower cost. The data demonstrated that GC-MS with ACF-SPME is well suitable for the analysis of HCHs in water.

Development of an analytical method for multi-residue quantification of 18 anthelmintics in various animal-based food products using liquid chromatography-tandem mass spectrometry

In this study,we developed a simple screening procedure for the determination of 18 anthelmintics(including benzimidazoles,macrocyclic lactones,salicylanilides,substituted phenols,tetrahydropyrimidines,and imidazothiazoles)in five animal-derived food matrices(chicken muscle,pork,beef,milk,and egg)using liquid chromatography-tandem mass spectrometry.Analytes were extracted using acetonitrile/1% acetic acid(milk and egg)and acetonitrile/1% acetic acid with 0.5 mL of distilled water(chicken muscle,pork,and beef),and purified using saturated n-hexane/acetonitrile.A reversed-phase analytical column and a mobile phase consisting of(A)10 mM ammonium formate in distilled water and(B)methanol were used to achieve optimal chromatographic separation.Matrix-matched standard calibration curves(R^(2)≥0.9752)were obtained for concentration equivalent to ×1/2,×1,×2,×3,×4,and×5 fold the maximum residue limit(MRL)stipulated by the Korean Ministry of Food and Drug Safety.Recoveries of 61.2e118.4%,with relative standard deviations(RSDs)of ≤19.9%(intraday and interday),were obtained for each sample at three spiking concentrations(×1/2,×1,and ×2 the MRL values).Limits of detection,limits of quantification,and matrix effects were 0.02e5.5 mg/kg,0.06e10 mg/kg,and -98.8 to 13.9%(at 20 μg/kg),respectively.In five samples of each food matrix(chicken muscle,pork,beef,milk,and egg)purchased from large retailers in Seoul that were tested,none of the target analytes were detected.It has therefore been shown that this protocol is adaptable,accurate,and precise for the quantification of anthelmintic residues in foods of animal origin.

Determination of Organochlorine and Synthetic Pyrethroid Pesticide Residues in Water Samples Collected from Different Locations of Bangladesh

The present study was aimed to validate an analytical method for the quantification of 19 organochlorine and 2 synthetic pyrethroid pesticide residues in water samples using modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction and Gas Chromatography coupled with Electron Capture Detector (ECD). The selected pesticide residues were determined by in-house validated method. The analytical method was validated by evaluating the accuracy, precision, linearity, limit of detection (LOD) and limit of quantification (LOQ). The average recoveries of the selected pesticides ranged from 78% to 117% with RSDr ≤ 12% in two fortification levels of 0.02 and 0.1 mg/L. The linearity was ≥0.995 for all of the selected pesticides. The LOD ranged from 0.003 to 0.006 mg/L and the LOQ was 0.02 mg/L for all the selected analytes. This method was applied satisfactorily for the residue analysis of 108 water samples collected from nine districts of Bangladesh. Among the analyzed samples, only 4 had cypermethrin residues (0.026 mg/L, 0.034 mg/L, 0.045 mg/L and 0.05 mg/L). The level of detected cypermethrin residues were above the WHO recommended guide line values of water quality.

Testing heteroscedasticity in nonparametric regression models based on residual analysis

The importance of detecting heteroscedasticity in regression analysis is widely recognized because efficient inference for the regression function requires that heteroscedasticity should be taken into account. In this paper, a simple test for heteroscedasticity is proposed in nonparametric regression based on residual analysis. Furthermore, some simulations with a comparison with Dette and Munk＇s method are conducted to evaluate the performance of the proposed test. The results demonstrate that the method in this paper performs quite satisfactorily and is much more powerful than Dette and Munk＇s method in some cases.

Research on Pesticide Residues of Cypermethrin in Lettuce

In order to find the effective method to reduce pesticide residues in vegetables, and promote the healthy development of vegetable industry. The paper used chlorothalonil, fenvalerate, dimethoate widely used pesticides as experimental material, using GC method to measure residual dynamics of vegetable pesticide. The results show that： fenvalerate, dimethoate, chlorothalonil pesticide residues in lettuce was higher than that tomato in the application day, respectively reach at 42.9%, 44.9%, 57.8%, pesticide degradation rate in open land were significantly higher than those in greenhouse within 5-20 days. The test showed that： the degradation of pesticide amount is in 8.77%r-19.64% within 1 days. The initial concentration of pesticides on vegetables are relevant with surface area of vegetable edible parts; the degradation speed of pesticide degradation rate in greenhouse vegetable is obviously slower than the open field vegetable; pesticide deposition phenomenon is an important factor affecting the pesticide residues in greenhouse.

Residue Based Open-Loop Modal Analysis Method for Detecting LFMR of PMSG-WFs Penetrated Power Systems

This paper proposes a residue based open-loop modal analysis method to detect low frequency modal resonance(LFMR),including asymmetric low frequency modal attraction(ALFMA)and asymmetric low frequency modal repulsion(ALFMR),of permanent magnetic synchronous generator based wind farms(PMSG-WFs)penetrated power systems.The formation of ALFMA and ALFMR caused by two open-loop low frequency oscillation(LFO)modes moving close and apart is analyzed in detail.Via predicting the trajectories of closed-loop LFO modes based on calculation of residue of open-loop LFO modes,both ALFMA and ALFMR can be detected.The proposed method can select LFO modes which move to the right half complex plane as control parameters vary.Simulation studies are carried out on a three-machine power system and a four-machine 11-bus power system to verify the properties of the proposed method.

Impact of climate and human activity on NDVI of various vegetation types in the Three-River Source Region, China

The Three-River Source Region(TRSR)in China holds a vital position and exhibits an irreplaceable strategic importance in ecological preservation at the national level.On the basis of an in-depth study of the vegetation evolution in the TRSR from 2000 to 2022,we conducted a detailed analysis of the feedback mechanism of vegetation growth to climate change and human activity for different vegetation types.During the growing season,the spatiotemporal variations of normalized difference vegetation index(NDVI)for different vegetation types in the TRSR were analyzed using the Moderate Resolution Imaging Spectroradiometer(MODIS)-NDVI data and meteorological data from 2000 to 2022.In addition,the response characteristics of vegetation to temperature,precipitation,and human activity were assessed using trend analysis,partial correlation analysis,and residual analysis.Results indicated that,after in-depth research,from 2000 to 2022,the TRSR's average NDVI during the growing season was 0.3482.The preliminary ranking of the average NDVI for different vegetation types was as follows:shrubland(0.5762)>forest(0.5443)>meadow(0.4219)>highland vegetation(0.2223)>steppe(0.2159).The NDVI during the growing season exhibited a fluctuating growth trend,with an average growth rate of 0.0018/10a(P<0.01).Notably,forests displayed a significant development trend throughout the growing season,possessing the fastest rate of change in NDVI(0.0028/10a).Moreover,the upward trends in NDVI for forests and steppes exhibited extensive spatial distributions,with significant increases accounting for 95.23%and 93.80%,respectively.The sensitivity to precipitation was significantly enhanced in other vegetation types other than highland vegetation.By contrast,steppes,meadows,and highland vegetation demonstrated relatively high vulnerability to temperature fluctuations.A further detailed analysis revealed that climate change had a significant positive impact on the TRSR from 2000 to 2022,particularly in its northwestern areas,accounting for 85.05%of the total area.Meanwhile,human activity played a notable positive role in the southwestern and southeastern areas of the TRSR,covering 62.65%of the total area.Therefore,climate change had a significantly higher impact on NDVI during the growing season in the TRSR than human activity.

Impacts of climate change and human activities on vegetation dynamics on the Mongolian Plateau, East Asia from 2000 to 2023

The Mongolian Plateau in East Asia is one of the largest contingent arid and semi-arid areas of the world.Under the impacts of climate change and human activities,desertification is becoming increasingly severe on the Mongolian Plateau.Understanding the vegetation dynamics in this region can better characterize its ecological changes.In this study,based on Moderate Resolution Imaging Spectroradiometer(MODIS)images,we calculated the kernel normalized difference vegetation index(kNDVI)on the Mongolian Plateau from 2000 to 2023,and analyzed the changes in kNDVI using the Theil-Sen median trend analysis and Mann-Kendall significance test.We further investigated the impact of climate change on kNDVI change using partial correlation analysis and composite correlation analysis,and quantified the effects of climate change and human activities on kNDVI change by residual analysis.The results showed that kNDVI on the Mongolian Plateau was increasing overall,and the vegetation recovery area in the southern region was significantly larger than that in the northern region.About 50.99%of the plateau showed dominant climate-driven effects of temperature,precipitation,and wind speed on kNDVI change.Residual analysis showed that climate change and human activities together contributed to 94.79%of the areas with vegetation improvement.Appropriate human activities promoted the recovery of local vegetation,and climate change inhibited vegetation growth in the northern part of the Mongolian Plateau.This study provides scientific data for understanding the regional ecological environment status and future changes and developing effective ecological protection measures on the Mongolian Plateau.

Quantitative contributions of climate change and human activities to vegetation dynamics in the Zoige Plateau from 2001 to 2020

Climate change and human activities such as overgrazing and rapid development of tourism simultaneously affected the vegetation of the Zoige Plateau.However,the spatiotemporal variations of vegetation and the relative contributions of climate change and human activities to these vegetation dynamics remain unclear.Therefore,clarifying how and why the vegetation on the Zoige Plateau changed can provide a scientific basis for the sustainable development of the region.Here,we investigate NDVI trends using the Normalized Difference Vegetation Index(NDVI)as an indicator of vegetation greenness and distinguish the relative effects of climate changes and human activities on vegetation changes by utilizing residual trend analysis and the Geodetector.We find a tendency of vegetation greening from 2001 to 2020,with significant greening accounting for 21.44%of the entire region.However,browning area expanded rapidly after 2011.Warmer temperatures are the primary driver of vegetation changes in the Zoige Plateau.Climatic variations and human activities were responsible for 65.57%and 34.43%of vegetation greening,and 39.14%and 60.86%of vegetation browning,respectively,with browning concentrated along the Yellow,Black and White Rivers.Compared to 2001-2010,the inhibitory effect of human activity and climate fluctuations on vegetation grew dramatically between 2011 and 2020.

Town gas daily load forecasting based on machine learning combinatorial algorithms:A case study in North China

Timely and accurate gas load forecasting is critical for optimal scheduling under tight winter gas supply conditions.Under the background of the implementation of“coal-to-gas”for winter heating in rural areas of North China and the sufficient field research,this paper proposes a correction algorithm for daily average temperature based on the cumulative effect of temperature and a set of combined forecasting models for gas load forecasting based on machine learning and introduces its application through a detailed case study.In order to solve the problems of forecasting performance degradation and complexity increase caused by too many influencing factors,a combined forecasting model back-propagation-improved complete ensemble empirical mode decomposition with adaptive-noise-gated recurrent unit based on residual sequence analysis is proposed.Back propagation(BP)neural network is used to analyze the main influencing factors,so that the secondary influencing factors are reflected in the residual sequence generated by the forecasting.After decomposition,reconstruction,and re-forecast,the mean absolute percentage error(MAPE)of the combined models for the daily gas load in the case study has been controlled under 1.9%,which is significantly improved compared with each single algorithm.The forecasting error before and after the temperature correction are also compared.It is found that the MAPE with the temperature correction is reduced by 1.7%,which reflects the effectiveness of the temperature correction to eliminate the impact of temperature cumulative effect and its contribution to the improvement of the forecasting accuracy for the combined forecasting models.

Trends and perspectives on general Pesticide analytical chemistry

Agrochemicals are indispensable materials in agricultural production,used to control or prevent diseases,insects and weeds,and play important roles in ensuring both food security and food safety.Meanwhile,the negative impacts of modern synthetic pesticides on humans and the environment could not be neglected.Thus,the production,registration,application and monitoring of pesticides should be strictly checked to ensure their commercial product quality and safety to human health as well as to the environment.This review summarizes the analytical chemistry involved in the quality control(QC)analysis for commercial formulation,residue analysis,dietary risk assessment and regulation prospects of pesticides.The main concepts and contents of pesticide analytical chemistry are comprehensively introduced and analyzed.In addition,the requirements and criteria of the relevant guidelines from various organizations are discussed.Finally,the research frontier areas and future trending for the invention of new generation of agrochemicals,registration/enforcement,market monitoring and risk management of pesticides are discussed.

Distribution and Elimination of Norfloxacin in Fenneropenaeus chinensis Larvae

This study examined the distribution and elimination of Norfloxacin （NFLX） in Fenneropenaeus chinensis ovary and egg and newly hatched larvae. Mature parental shrimp were exposed to 4 or 10mgL-1 NFLX for 2 or 5d. Ovary and eggs of the shrimp were sampled after spawning in order to detect NFLX residue using high-performance liquid chromatography （HPLC）. Re- suits showed that NFLX residue accumulated in F. chinensis eggs after the parental exposure, with the highest residue detected in ovary. To examine the fate of NFLX residue in larvae, we further determined the concentration of NFLX residue in F. chinensis eggs and larvae at 4 different developmental stages after 24-h exposure. From the newly metamorphosed larvae （Oh post-metamorphosis, h.p.m）, samples were taken at different time intervals to 72 h,p.m. HPLC assay showed that the concentrations of NFLX residue in zoea exposed to 4 and 10mgL-1 NFLX were the highest at 1.5h, i.e., 0.332 and 0.454μgg-1, respectively. At the two NFLX expo- sure levels, the elimination time of half NFLX （half life） in nauplius was 45.36 and 49.85h, respectively, followed by that in zoea （31.68 and 33.13 h）, mysis larvae （42.24 and 47.28 h） and postlarvae （24.48 and 30.96 h）. Both NFLX exposure levels had a germi- cidal effect. The distribution and elimination of NFLX residue in F. chinensis tissue, eggs and larvae correlated well with the drug exposure level. The disappearance of NFLX residue coincided with the larval growth, and the half-life of NFLX decreased with the larval development.

Multiresidue pesticide analysis in tomato using GC-MS/MS using modified QuEChERS method with titanium-coated graphite with CNT-ABS nanocomposite as dispersive solid-phase extraction materials

The presence of pesticide residues in food and vegetables is a growing concern for consumers.To monitor these residues reliably,a selective and sensitive multiresidue system has been developed and validated in tomato by gas chromatography–tandem mass spectrometry(GC-MS/MS).Titanium-coated graphite with carbon nanotube(CNT)in acrylonitrile–butadiene–styrene(ABS)used as reversed-dispersive solid-phase extraction materials with modified QuEChERS(Quick,Easy,Cheap,Effective,Rugged,and Safe)method.Titanium-coated graphite with CNT-ABS is synthesized,characterized by X-ray diffraction and scanning electron microscopy.The clean-up performance of titanium-coated graphite with CNT-ABS was demonstrated to be better to primary secondary amine and graphitized carbon black cartridges.The processing of two multiple reaction monitoring transformations for each analyte is done using GC-MS/MS in electron impact mode.Satisfactory purification and recovery effects(74%–100%)of 35 pesticides were achieved in tomato matrices when using 5 mg of titanium-coated graphite ABS-CNT nanocomposite.It was observed that quinolphos and deltamethrin are present above the maximum residue limit.The technique proved to be reliable and sensitive in tomato samples for the routine testing of 35 pesticides.

Degradation Behavior and Safe Application Technology of 30% Kresoxim-methyl SC in Cucumber and Soil

[ Objective ] The paper was to determine the residue behavior and environmental safety of 30% kresoxim-methyl SC applied on cucumber under green- house conditions. [Method] Referring to Test Standard of Pesticide Residues, the residue dynamics of kresoxim-methyl SC in cucumber was determined by GC. [ Result ] The half lives of kresoxim-methly in cucumber of Yinchuan, Changsha, Harbin were 2.8 - 3.1,2.4 - 3.7, 2.1 - 5.1 d, respectively, and the final resi- due in cucumber after application for 3,5,7 d was less than 0.500 0 mg/kg that was the limited standards of the state. [ Conclusion] Under the proposed cultiva- tion conditions, it is recommended to use the maximum dosage formulation of 270 g. a. i/ha （ preparation 0.09 g/m2 ）, with spraying up to three times and the safe interval of 3 -5 d.

Seismic fine imaging and its significance for natural gas hydrate exploration in the Shenhu Test Area, South China Sea

Shenhu area in South China Sea includes extensive collapse and diapir structures,forming high-angle faults and vertical fracture system,which functions as a fluid migration channel for gas hydrate formation.In order to improve the imaging precision of natural gas hydrate in this area,especially for fault and fracture structures,the present work propose a velocity stitching technique that accelerates effectively the convergence of the shallow seafloor,indicating seafloor horizon interpretation and the initial interval velocity for model building.In the depth domain,pre-stack depth migration and residual curvature are built into the model based on high-precision grid-tomography velocity inversion,after several rounds of tomographic iterations,as the residual velocity field converges gradually.Test results of the Shenhu area show that the imaging precision of the fault zone is obviously improved,the fracture structures appear more clearly,the wave group characteristics significantly change for the better and the signal-to-noise ratio and resolution are improved.These improvements provide the necessary basis for the new reservoir model and field drilling risk tips,help optimize the favorable drilling target,and are crucial for the natural gas resource potential evaluation.