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 extract...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.展开更多
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...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.展开更多
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...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.展开更多
[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 ...[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.展开更多
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...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.展开更多
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 adsorp...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.展开更多
In this study,we developed a simple screening procedure for the determination of 18 anthelmintics(including benzimidazoles,macrocyclic lactones,salicylanilides,substituted phenols,tetrahydropyrimidines,and imidazothia...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.展开更多
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, rug...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.展开更多
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...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.展开更多
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 pesticide...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.展开更多
Investigating the spatiotemporal evolution of vegetation and its response mechanisms to natural and anthropogenic elements is crucial for regional vegetation restoration and ecological preservation.The Mu Us Sandy Lan...Investigating the spatiotemporal evolution of vegetation and its response mechanisms to natural and anthropogenic elements is crucial for regional vegetation restoration and ecological preservation.The Mu Us Sandy Land(MUSL),which is situated in the semi-arid zone of northwestern China adjacent to the Loess Plateau,has been at the forefront of desertification and oasis formation over the past two millennia.This study is based on the synthesis of the Normalized Difference Vegetation Index(NDVI)data from MOD13A3 data in the MODIS(Moderate-Resolution Imaging Spectroradiometer)dataset(2002-2021)and climate data(temperature and precipitation)at annual and monthly scales from the National Earth System Science Data Center.A range of analytical methods,including univariate linear regression,Theil-Sen trend analysis and Mann-Kendall significance test,correlation analysis,residual analysis,and Hurst index,were used to explore the response mechanisms of the NDVI to climate change and human activities and to predict the future trends of the NDVI in the MUSL.The results showed that through the method of correlation analysis,in terms of both spatially averaged correlation coefficients and area proportion,the NDVI was positively correlated with temperature and precipitation in 97.59%and 96.51%of the study area,respectively,indicating that temperature has a greater impact on the NDVI than precipitation.Residual analysis quantified the contributions of climate change and human activities to the NDVI changes,revealing that climate change and human activities contribute up to 30.00%and 70.00%,respectively,suggesting that human activities predominantly affect the NDVI changes in the MUSL.The Hurst index was used to categorize the future trend of the NDVI into four main directions of development:continuous degradation(0.05%of the study area),degradation in the past but improvement in the future(54.45%),improvement in the past but degradation in the future(0.13%),and continuous improvement(45.36%).In more than 50.00%of the regions that have been degraded in the past but were expected to improve in the future,the NDVI was expected to exhibit a stable trend of anti-persistent improvement.These findings provide theoretical support for future ecological protection,planning,and the implementation of ecological engineering in the MUSL,and also offer a theoretical basis for the planning and execution of construction projects,environmental protection measures,and the sustainable development of vegetation.展开更多
Vegetation response to the combined effects of human and nature has raised extensive controversy.The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear...Vegetation response to the combined effects of human and nature has raised extensive controversy.The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear.Combining spatial and temporal changes in fractional vegetation cover(FVC)and net primary productivity(NPP)from 2000 to 2021,we assessed the trend of these two indicators and quantified the impact of ecological restoration and climate factors on vegetation variation using partial correlation and residual analysis.The results indicated that:(1)From 2000 to 2021,vegetation restoration in the Taihang Mountain area was notably successful.FVC increased by 5.71%over 22 years with a change trend of 0.0018 per annum.The cumulative growth rate of NPP over the same period was 42.03%,corresponding to an average annual increase of 5.492 g(C)·m^(-2)·a^(-1).(2)During the 22-year period,the contribution rates of ecological engineering to FVC and NPP were 65.13%and 64.33%,respectively.Ecological restoration was the dominant factor affecting vegetation change,and its impact was increasing in over 90%of the regional projects.The primary climate controlling factor of NPP was precipitation,while FVC responded synergistically to precipitation(primary)and temperature(secondary).Overall,the impact of precipitation on vegetation was 1.5 times that of temperature.(3)Among various ecological restoration types,grassland restoration contributed the most to vegetation change,followed by forest land restoration.This study offers valuable scientific insights that can guide the sustainability of vegetation ecology in semi-arid mountainous areas.展开更多
Vegetation change is the most intuitive and sensitive bioindicator reflecting seasonal and interannual variations in the external environment,and it can directly reflect the rapid response of terrestrial ecosystems to...Vegetation change is the most intuitive and sensitive bioindicator reflecting seasonal and interannual variations in the external environment,and it can directly reflect the rapid response of terrestrial ecosystems to climate change.Using remote sensing and meteorological data,this study revealed the spatiotemporal characteristics of leaf area index(LAI)in the north of China during 1982–2022,clarified the response of LAI change to different meteorological factors,quantified the impacts of climate change and human activities on LAI change,and predicted the future trends in LAI change.From 1982 to 2022,the vegetation in the north of China generally showed a greening trend with a change rate of 0.0071 m2/(m2•a).Temperature was strongly positively correlated with LAI and was the main climate factor driving LAI change.Residual analysis revealed that vegetation improvement occurred in across 74.53%of the study area,and vegetation improvement in about 96.83%of the improved zone was attributed to a combination of climate change and human activities.The regions where anthropogenic contribution exceeded 60.00%covered 36.83%of human-affected areas,while the regions where climatic contribution exceeded 60.00%covered 19.77%of climate-affected areas,demonstrating that human activities influenced the intensity of LAI change more deeply despite the broad spatial impact of climate change.Human activities such as afforestation and the Three-North Protective Forest Program played the dominant role in vegetation greening compared to climate change.Hurst index analysis indicated that 80.30%of vegetation in the north of China is expected to experience a non-sustained improvement in the future.These findings will provide a scientific basis for optimizing the protection strategies of the national ecological barrier areas and evaluating the effectiveness of major ecological projects.展开更多
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...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.展开更多
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. Ov...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.展开更多
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 ...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.展开更多
[ 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 Resi...[ 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.展开更多
This study analyzed the spatial and temporal variations in the Normalized Difference Vegetation Index(NDVI) on the Mongolian Plateau from 1982–2013 using Global Inventory Modeling and Mapping Studies(GIMMS) NDVI3 g d...This study analyzed the spatial and temporal variations in the Normalized Difference Vegetation Index(NDVI) on the Mongolian Plateau from 1982–2013 using Global Inventory Modeling and Mapping Studies(GIMMS) NDVI3 g data and explored the effects of climate factors and human activities on vegetation. The results indicate that NDVI has slight upward trend in the Mongolian Plateau over the last 32 years. The area in which NDVI increased was much larger than that in which it decreased. Increased NDVI was primarily distributed in the southern part of the plateau, especially in the agro-pastoral ecotone of Inner Mongolia. Improvement in the vegetative cover is predicted for a larger area compared to that in which degradation is predicted based on Hurst exponent analysis. The NDVI-indicated vegetation growth in the Mongolian Plateau is a combined result of climate variations and human activities. Specifically, the precipitation has been the dominant factor and the recent human effort in protecting the ecological environments has left readily detectable imprints in the NDVI data series.展开更多
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 vegetatio...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.展开更多
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 t...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.展开更多
文摘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.
文摘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.
基金Supported by Scientific and Technological Projects of Nanning Municipal Science and Technology Bureau(20132308)
文摘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.
文摘[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.
基金Supported by National Key Research and Development Program of China(2016YFD0200205-2)~~
文摘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.
文摘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.
基金supported by a grant(18162MFDS523)from the Ministry of Food and Drug Safety Administration in 2019.
文摘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.
文摘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.
基金the National Natural Science Foundation of China (10531030)
文摘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.
文摘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.
基金funded by the Shaanxi Provincial Department of Science and Technology(2023JCYB449)the Yan'an University Project(YDBK2017-19)+1 种基金the Yan'an Science and Technology Bureau's List System Project(2023SLJBZ002)the Shaanxi Provincial Department of Education Natural Science Special Project(23JK0725,24JK0716).
文摘Investigating the spatiotemporal evolution of vegetation and its response mechanisms to natural and anthropogenic elements is crucial for regional vegetation restoration and ecological preservation.The Mu Us Sandy Land(MUSL),which is situated in the semi-arid zone of northwestern China adjacent to the Loess Plateau,has been at the forefront of desertification and oasis formation over the past two millennia.This study is based on the synthesis of the Normalized Difference Vegetation Index(NDVI)data from MOD13A3 data in the MODIS(Moderate-Resolution Imaging Spectroradiometer)dataset(2002-2021)and climate data(temperature and precipitation)at annual and monthly scales from the National Earth System Science Data Center.A range of analytical methods,including univariate linear regression,Theil-Sen trend analysis and Mann-Kendall significance test,correlation analysis,residual analysis,and Hurst index,were used to explore the response mechanisms of the NDVI to climate change and human activities and to predict the future trends of the NDVI in the MUSL.The results showed that through the method of correlation analysis,in terms of both spatially averaged correlation coefficients and area proportion,the NDVI was positively correlated with temperature and precipitation in 97.59%and 96.51%of the study area,respectively,indicating that temperature has a greater impact on the NDVI than precipitation.Residual analysis quantified the contributions of climate change and human activities to the NDVI changes,revealing that climate change and human activities contribute up to 30.00%and 70.00%,respectively,suggesting that human activities predominantly affect the NDVI changes in the MUSL.The Hurst index was used to categorize the future trend of the NDVI into four main directions of development:continuous degradation(0.05%of the study area),degradation in the past but improvement in the future(54.45%),improvement in the past but degradation in the future(0.13%),and continuous improvement(45.36%).In more than 50.00%of the regions that have been degraded in the past but were expected to improve in the future,the NDVI was expected to exhibit a stable trend of anti-persistent improvement.These findings provide theoretical support for future ecological protection,planning,and the implementation of ecological engineering in the MUSL,and also offer a theoretical basis for the planning and execution of construction projects,environmental protection measures,and the sustainable development of vegetation.
基金supported by the National Natural Science Foundation of China(No.41930651 and 41807013)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.2020102)。
文摘Vegetation response to the combined effects of human and nature has raised extensive controversy.The relative contributions of ecological restoration and multiple climate factors on vegetation variation remain unclear.Combining spatial and temporal changes in fractional vegetation cover(FVC)and net primary productivity(NPP)from 2000 to 2021,we assessed the trend of these two indicators and quantified the impact of ecological restoration and climate factors on vegetation variation using partial correlation and residual analysis.The results indicated that:(1)From 2000 to 2021,vegetation restoration in the Taihang Mountain area was notably successful.FVC increased by 5.71%over 22 years with a change trend of 0.0018 per annum.The cumulative growth rate of NPP over the same period was 42.03%,corresponding to an average annual increase of 5.492 g(C)·m^(-2)·a^(-1).(2)During the 22-year period,the contribution rates of ecological engineering to FVC and NPP were 65.13%and 64.33%,respectively.Ecological restoration was the dominant factor affecting vegetation change,and its impact was increasing in over 90%of the regional projects.The primary climate controlling factor of NPP was precipitation,while FVC responded synergistically to precipitation(primary)and temperature(secondary).Overall,the impact of precipitation on vegetation was 1.5 times that of temperature.(3)Among various ecological restoration types,grassland restoration contributed the most to vegetation change,followed by forest land restoration.This study offers valuable scientific insights that can guide the sustainability of vegetation ecology in semi-arid mountainous areas.
基金supported by the National Natural Science Foundation of China(42301127)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(2023D01C185).
文摘Vegetation change is the most intuitive and sensitive bioindicator reflecting seasonal and interannual variations in the external environment,and it can directly reflect the rapid response of terrestrial ecosystems to climate change.Using remote sensing and meteorological data,this study revealed the spatiotemporal characteristics of leaf area index(LAI)in the north of China during 1982–2022,clarified the response of LAI change to different meteorological factors,quantified the impacts of climate change and human activities on LAI change,and predicted the future trends in LAI change.From 1982 to 2022,the vegetation in the north of China generally showed a greening trend with a change rate of 0.0071 m2/(m2•a).Temperature was strongly positively correlated with LAI and was the main climate factor driving LAI change.Residual analysis revealed that vegetation improvement occurred in across 74.53%of the study area,and vegetation improvement in about 96.83%of the improved zone was attributed to a combination of climate change and human activities.The regions where anthropogenic contribution exceeded 60.00%covered 36.83%of human-affected areas,while the regions where climatic contribution exceeded 60.00%covered 19.77%of climate-affected areas,demonstrating that human activities influenced the intensity of LAI change more deeply despite the broad spatial impact of climate change.Human activities such as afforestation and the Three-North Protective Forest Program played the dominant role in vegetation greening compared to climate change.Hurst index analysis indicated that 80.30%of vegetation in the north of China is expected to experience a non-sustained improvement in the future.These findings will provide a scientific basis for optimizing the protection strategies of the national ecological barrier areas and evaluating the effectiveness of major ecological projects.
基金supported by Guangxi Key Research and Development Program,China(No:AB21196039)the National Natural Science Foundation of China(No:32172439)Key Research and Development Program of Hainan Province,China(No:ZDYF2022XDNY232).
文摘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.
基金supported by the Earmarked Fund for Modern Agro-industry Technology Research System,China(No.CARS-47)the Special Fund for Agro-scientific Research in the Public Interest of China(No.201103034)
文摘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.
文摘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.
文摘[ 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.
基金National Key Technology R&D Program of China,No.2013BAK05B01,No.2013BAK05B02National Natural Science Foundation of China,No.41571491,No.61631011Program of Introducing Talents of Discipline to Universities,No.B16011
文摘This study analyzed the spatial and temporal variations in the Normalized Difference Vegetation Index(NDVI) on the Mongolian Plateau from 1982–2013 using Global Inventory Modeling and Mapping Studies(GIMMS) NDVI3 g data and explored the effects of climate factors and human activities on vegetation. The results indicate that NDVI has slight upward trend in the Mongolian Plateau over the last 32 years. The area in which NDVI increased was much larger than that in which it decreased. Increased NDVI was primarily distributed in the southern part of the plateau, especially in the agro-pastoral ecotone of Inner Mongolia. Improvement in the vegetative cover is predicted for a larger area compared to that in which degradation is predicted based on Hurst exponent analysis. The NDVI-indicated vegetation growth in the Mongolian Plateau is a combined result of climate variations and human activities. Specifically, the precipitation has been the dominant factor and the recent human effort in protecting the ecological environments has left readily detectable imprints in the NDVI data series.
基金supported by the National Natural Science Foundation of China (42377472, 42174055)the Jiangxi Provincial Social Science "Fourteenth Five-Year Plan" (2024) Fund Project (24GL45)+1 种基金the Research Center of Resource and Environment Economics (20RGL01)the Provincial Finance Project of Jiangxi Academy of Sciences-Young Talent Cultivation Program (2023YSBG50010)
文摘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.
基金This study was financially supported by the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(GML2019ZD0207)Dedicated Fund for Promoting High-Quality Economic Development in Guangdong Province(Marine Economic Development Project)(GDNRC[2020]045)the State Key Laboratory of Marine Geology of Tongji University(MGK202007).
文摘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.
