Moso bamboo(Phyllostachys edulis)forests are a vital resource in subtropical China,known for their high carbon(C)sequestration capacity.However,the dynamic processes of C fluxes within each component(canopy,culm,and s...Moso bamboo(Phyllostachys edulis)forests are a vital resource in subtropical China,known for their high carbon(C)sequestration capacity.However,the dynamic processes of C fluxes within each component(canopy,culm,and soil)and their individual contributions,particularly during on-and off-years,remain unclear.A 2-year field experiment was conducted to investigate the dynamics of C fluxes from the canopy,culm,and soil(partitioned into heterotrophic,rhizome,and stump respiration)and their contributions to net ecosystem productivity(NEP)in a representative Moso bamboo forest in the subtropical region of China.The average annual NEP of the Moso bamboo forest was 7.31±2.76 t C·ha^(-1).Specifically,the canopy's annual net C uptake was 17.30±3.23 tC·ha^(-1),accounting for 237%of NEP.In contrast,C emissions from heterotrophs,culms,rhizomes,and stumps were 5.37±1.20,2.18±1.05,1.29±0.04,and 1.15±0.33 t C·ha^(-1),accounting for73%,30%,18%,and16%of NEP,respectively.The NEP,net cumulative C uptake in the canopy,and C emissions from the respiration of heterotrophs and stumps were all significantly higher during on-years when compared to off-years,whereas C emissions from bamboo culms displayed opposite trends.These findings offer a new approach for quantifying the C budgets of Moso bamboo forests and provide valuable insights into the C cycling processes in forest ecosystems.展开更多
Phenological changes play a central role in regulating seasonal variation in the ecological processes,exerting significant impacts on hydrologic and nutrient cycles,and ultimately influencing ecosystem functioning suc...Phenological changes play a central role in regulating seasonal variation in the ecological processes,exerting significant impacts on hydrologic and nutrient cycles,and ultimately influencing ecosystem functioning such as carbon uptake.However,the potential impact mechanisms of phenological events on seasonal carbon dynamics in subtropical regions are under-investigated.These knowledge gaps hinder from accurately linking photosynthetic phenology and carbon sequestration capacity.Using chlorophyll fluorescence remote sensing and productivity data from 2000 to 2019,we found that an advancement in spring phenology increased spring gross(GPP)and net primary productivity(NPP)in subtropical vegetation of China by 2.1 gC m^(-2)yr^(-1)and 1.4 gC m^(-2)yr^(-1),respectively.A delay in autumn phenology increased the autumnal GPP and NPP by 0.4 gC m^(-2)yr^(-1)and 0.2 gC m^(-2)yr^(-1),respectively.Temporally,the contribution of the spring phenology to spring carbon uptake increased significantly during the study period,while this positive contribution showed a nonsignificant trend in summer.In comparison,the later autumn phenology could significantly contribute to the increase in autumnal carbon uptake;however,this contributing effect was weakened.Path analysis indicated that these phenomena have been caused by the increased leaf area and enhanced photosynthesis due to earlier spring and later autumn phenology,respectively.Our results demonstrate the diverse impacts of vegetation phenology on the seasonal carbon sequestration ability and it is imperative to consider such asymmetric effects when modeling ecosystem processes parameterized under future climate change.展开更多
Although paid to upward shift response to global phenomenon at low zones did not receive increasing attention has been of plant species in altitude as a warming, research on this altitudinal and low latitudinal enoug...Although paid to upward shift response to global phenomenon at low zones did not receive increasing attention has been of plant species in altitude as a warming, research on this altitudinal and low latitudinal enough attention. In this study, an investigation was carried out to test the relationship between the upward spread of Moso bamboo （Phyllostachys pubescens） along altitudinal gradient and the increasing air temperature over the past decade within the Tianmu Mountain region, situated in southeastern China. Results showed that the peak elevation of Moso bamboo population establishment rose by an average of 9.8 m （±2.7 m） during the past decade and significant correlation existed with mean annual temperature （P 〈 0.0001, n = 339） but not with annual precipitation （P = 0.7, n = 339）, indicating that the upward shift of Moso bamboo along altitudinal gradients was driven primarily by warming temperatures. This upward shift could potentially reduce biodiversity by altering the species composition of the ecosystem. However, there is also the potential for increased carbon sequestration capacity of local forest systems, which would produce an additional carbon sink to combat rising atmospheric C02 concentrations and future global warming.展开更多
Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions...Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions.Results:Using satellite solar-induced chlorophyll fluorescence(SIF)and MODIS enhanced vegetation index(EVI)data,we applied two methods to evaluate temporal and spatial patterns of the end of the growing season(EGS)in subtropical vegetation in China,and analyze the dependence of EGS on preseason maximum and minimum temperatures as well as cumulative precipitation.Our results indicated that the averaged EGS derived from the SIF and EVI based on the two methods(dynamic threshold method and derivative method)was later than that derived from gross primary productivity(GPP)based on the eddy covariance technique,and the time-lag for EGSsif and EGSevi was approximately 2 weeks and 4 weeks,respectively.We found that EGS was positively correlated with preseason minimum temperature and cumulative precipitation(accounting for more than 73%and 62%of the study areas,respectively),but negatively correlated with preseason maximum temperature(accounting for more than 59%of the study areas).In addition,EGS was more sensitive to the changes in the preseason minimum temperature than to other climatic factors,and an increase in the preseason minimum temperature significantly delayed the EGS in evergreen forests,shrub and grassland.Conclusions:Our results indicated that the SIF outperformed traditional vegetation indices in capturing the autumn photosynthetic phenology of evergreen forest in the subtropical region of China.We found that minimum temperature plays a significant role in determining autumn photosynthetic phenology in the study region.These findings contribute to improving our understanding of the response of the EGS to climate change in subtropical vegetation of China,and provide a new perspective for accurately evaluating the role played by evergreen vegetation in the regional carbon budget.展开更多
Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate...Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.展开更多
Size–fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time–of–fl...Size–fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time–of–flight secondary ion mass spectrometry（TOF–SIMS）.The variation characteristics of the surface chemical composition and influencing factors were studied, and the possible sources of these chemical compositions were identified through principal component analysis. The results showed that inorganic components such as crustal elements and sulfate, and organic components such as aliphatic hydrocarbons and oxygen–containing organic groups were present. Some surface components, such as polycyclic aromatic hydrocarbons, heavy metals and fluorides may exert adverse effects on human health. The species and relative percentages of the chemical components varied with particle size, diurnal and pollution progress. During a heavy pollution event, the species and relative percentages of secondary components such as oxygen–containing organic groups and sulfurous compounds increased, indicating that particles aged during this event. The surface chemical composition of the aerosol particles was affected mainly by emissions from coal combustion and motor vehicles. In addition, air pollution, meteorological factors, and air mass transport also exerted a significant effect on the surface chemical composition of aerosol particles.展开更多
The small and medium-sized river basins along southeast coast of China hold comparatively abundant water resources.However,the rapid resources urbanization in recent years has produced a series of water problems such ...The small and medium-sized river basins along southeast coast of China hold comparatively abundant water resources.However,the rapid resources urbanization in recent years has produced a series of water problems such as deterioration of river water quality,water shortage and exacerbated floods,which have constrained urban economic development.By applying the principle of triple supply-demand equilibrium,this paper focuses on the estimation of levels of water supply and demand in 2030 at different guarantee probabilities,with a case study of Xiamen city.The results show that water shortage and inefficient utilization are main problems in the city,as the future water supply looks daunting,and a water shortage may hit nearly 2×10^(8)m^(3)in an extraordinarily dry year.Based on current water supply-demand gap and its trend,this paper proposes countermeasures and suggestions for developing and utilizing groundwater resources and improving the utilization rate of water resources,which can supply as a reference for other southeast middle-to-small-sized basin cities in terms of sustainable water resources and water environment protection.展开更多
A new method combining QuEChERS (quick, easy, cheap, effective, rugged and safe) and DLLME (dispersive liquid–liquid microextraction) for the simultaneous determination of residues of ten sulfonylurea herbicide in wa...A new method combining QuEChERS (quick, easy, cheap, effective, rugged and safe) and DLLME (dispersive liquid–liquid microextraction) for the simultaneous determination of residues of ten sulfonylurea herbicide in water using UPLC-MS/MS was developed and validated. Analytes were extracted and purified with QuEChERS and concentrated in chlorobenzene by applying the DLLME procedure. Several extraction parameters were tested, such as volume, extractive solvent by the QuEChERS method and subsequently used for DLLME, selection of extractive solvent and its volume, was tested. The developed method was validated on the basis of international guidelines. Mean recoveries ranged from 81.2 to 104.9%. Repeatability and reproducibility were lower than 10%. Limits of detection (LODs) and quantification (LOQs) were below 0.074 μg/L and 0.244 μg/L, respectively. Decision limit (CCα) and detection capability (CCβ) were calculated and CCβ ranged from 0.101 μg/L (pyrazosulfuron-ethyl) to 0.260 μg/L (nicosulfuron). Finally, when the method was applied to real samples, traces of three compounds were found in 42 samples and only thifensulfuon-methyl was detected above the LOQ in three samples at 0.17-0.20 μg/L.展开更多
Atmospheric aerosol particle samples were collected using an Ambient Eight Stage（Non-Viable） Cascade Impactor Sampler in a typical urban area of Beijing from 27 th Sep.to 5th Oct.,2009.The surface chemistry of these...Atmospheric aerosol particle samples were collected using an Ambient Eight Stage（Non-Viable） Cascade Impactor Sampler in a typical urban area of Beijing from 27 th Sep.to 5th Oct.,2009.The surface chemistry of these aerosol particles was analyzed using Static Time of Flight-Secondary Ion Mass Spectrometry（Static TOF-SIMS）.The factors influencing surface compositions were evaluated in conjunction with the air pollution levels,meteorological factors,and air mass transport for the sampling period.The results show that a variety of organic ion groups and inorganic ions/ion groups were accumulated on the surfaces of aerosol particles in urban areas of Beijing;and hydrophobic organic compounds with short-or middle-chain alkyl as well as hydrophilic secondary inorganic compounds were observed.All these compounds have the potential to affect the atmospheric behavior of urban aerosol particles.PM1.1–2.1and PM3.3–4.7had similar elements on their surfaces,but some molecules and ionic groups demonstrated differences in Time of Flight-Secondary Ion Mass Spectrometry spectra.This suggests that the quantities of elements varied between PM1.1–2.1and PM3.3–4.7.In particular,more intense research efforts into fluoride pollution are required,because the fluorides on aerosol surfaces have the potential to harm human health.The levels of air pollution had the most significant influence on the surface compositions of aerosol particles in our study.Hence,heavier air pollution was associated with more complex surface compositions on aerosol particles.In addition,wind,rainfall,and air masses from the south also greatly influenced the surface compositions of these urban aerosol particles.展开更多
With the enlarging scale and intensifying production of livestock and poultry breeding, the environment pollution becomes increasingly prominent in the Dianchi Lake Basin since 1990s. According to the survey of ＂The ...With the enlarging scale and intensifying production of livestock and poultry breeding, the environment pollution becomes increasingly prominent in the Dianchi Lake Basin since 1990s. According to the survey of ＂The First National Census of Pollution Sources＂, occurrence and discharge of pollutants in large-scale livestock and poultry farms in this region were first understood. The pollution characteristics of large-scale live- stock and poultry breeding were also analyzed deeply. On this basis, the significance of pollution control programs for environment protection was investigated from aspects of pollution control policy, technology management and publicity.展开更多
Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions ...Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions on soil CH_(4) flux in tropical rainforests are still poorly understood.From January 2015 to December 2018,a field experiment was conducted in a primary tropical montane rainforest(PTMR)and a secondary tropical montane rainforest(STMR)in southern China to quantify the impact of N additions at four levels(N0:0 kg N⋅ha^(-1)⋅year^(-1);N25:25 kg N⋅ha^(-1)⋅year^(-1);N50:50 kg N⋅ha^(-1)⋅year^(-1);N100:100 kg N⋅ha^(-1)⋅year^(-1)on soil CH_(4) flux.Results:Four years of measurements showed clear seasonal variations in CH_(4) flux in all treatment plots for both forest types(PTMR and STMR),with lower rates of soil CH_(4) uptake during the wet season and higher rates of soil CH_(4) uptake during the dry season.Soil CH_(4) uptake rates were significantly and negatively correlated with both soil temperature and soil moisture for both forest types.Annual CH_(4) uptake for the N0 plots from the PTMR and STMR soils were2.20 and1.98 kg N⋅ha^(-1)⋅year^(-1),respectively.At the PTMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 19%,29%,and 36%for the N25,N50,and N100 treatments,respectively.At the STMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 15%,18%,and 38%for the N25,N50,and N100 treatments,respectively.High level N addition had a stronger inhibitory impact on soil CH_(4) uptake than did the low level N addition.Conclusion:Our data suggest that soil CH_(4) uptake in tropical rainforests is sensitive to N deposition.If atmospheric N deposition continues to increase in the future,the soil CH_(4) sink strength of tropical rainforests may weaken further.展开更多
This paper presents the research on the atmospheric corrosion rates of carbon steel, zinc and copper in Chongqing, which was a corrosion subprogram of an international project, Regional Air Pollution in Developing Cou...This paper presents the research on the atmospheric corrosion rates of carbon steel, zinc and copper in Chongqing, which was a corrosion subprogram of an international project, Regional Air Pollution in Developing Countries. We performed field exposure tests of carbon steel, zinc and copper at an urban site Guanyinqiao and a rural site Tieshanping inChongqing, then used grey relational analysis, based on the database of the whole corrosion project, to determine the order of the effect of environmental factors on corrosion rates of tested metals, and established dose-response functions for these three metals. The results showed that the two crucial agents of acidic environment, SO2 and H+, were common factors that contributed most to the corrosion of the tested metals. The established dose-response functions for outdoor carbon steel and zinc are proved applicable to use in Chongqing, but the function for copper needs further modifying. We employed these dose- response functions and general environmental data to elaborate the maps of corrosion rate respectively of carbon steel and zinc by geological information system (GIS) technique which help to identify areas of high corrosion damage risk. An acceptable annual average SO2 level of 21 μg/m3 for carbon steel and that of 61 μg/m3 for zinc are also put forward to control the air pollution impact on atmospheric corrosion in Chongqing urban areas.展开更多
Based on the laboratory experiments with the saltwater and freshwater replacing each other in the level sand column, taking the kaolin, illite, smectite, bivalent hydrargyrum ion （Hg^2＋） and ＂phenol （C6H5OH） as ...Based on the laboratory experiments with the saltwater and freshwater replacing each other in the level sand column, taking the kaolin, illite, smectite, bivalent hydrargyrum ion （Hg^2＋） and ＂phenol （C6H5OH） as examples, this paper studies the applications of water sensitivity in situ remediation in saltwater-freshwater transition zone. In the water sensitivity process, the release and migration of clay minerals can make the hydraulic conductivity （HC） decrease and pollutants remove. A new type of low penetrable or impenetrable purdah can be built by adding clay minerals into the sand media to replace the underground concrete impenetrable wall to prevent seawater intrusion, and a number of the heavy metals and organic pollutants in the sand media can be removed by in situ remediation. The results show that the content of kaolin and illite influences the water sensitivity process slightly, and HC of the sand columns descends from 0.011 cm/s to 0.001 4 cm/s and 0.001 2 cm/s respectively even if the content reaches 12% （weight ratio, sic passim）. However, for smectite, HC descends sharply to about 1 × 10^-8 cm/s when its content reaches 4%, and no water can flow through the sand columns beyond 5%. The particle release and migration processes can remove the Hg^2＋ and C6HsOH out of the sand columns efficiently, the removing rate of Hg^2＋ is 31.68% when the freshwater and saltwater are filtered through the sand columns polluted by Hg^2＋, while it is 67.55% when the water sensitivity occurs. With the same method, the removing rates of C6H5OH under the fluid flow and water sensitivity are 55.71% and 43.43% respectively.展开更多
A mathematic model is developed which is applied to analyze the main factors that affect electrode performance and to account for the process of reaction and mass transfer in gas-diffusion electrodes in contact with l...A mathematic model is developed which is applied to analyze the main factors that affect electrode performance and to account for the process of reaction and mass transfer in gas-diffusion electrodes in contact with liquid electrolytes. Electrochemical Thiele modulus φ^2 and electrochemical effectiveness factor η are introduced to elucidate the effects of diffusion on electrochemical reaction and utilization of the gas-diffusion electrode. Profile of the reactant along axial direction is discussed, dependence of electrode potential V on current density J, are predicated by means of the newly developed mathematical model.展开更多
Background: The accurate estimation of soil nutrient content is particularly important in view of its impact on plant growth and forest regeneration. In order to investigate soil nutrient content and quality for the n...Background: The accurate estimation of soil nutrient content is particularly important in view of its impact on plant growth and forest regeneration. In order to investigate soil nutrient content and quality for the natural regeneration of Dacrydium pectinatum communities in China, designing advanced and accurate estimation methods is necessary.Methods: This study uses machine learning techniques created a series of comprehensive and novel models from which to evaluate soil nutrient content. Soil nutrient evaluation methods were built by using six support vector machines and four artificial neural networks.Results: The generalized regression neural network model was the best artificial neural network evaluation model with the smallest root mean square error(5.1), mean error(-0.85), and mean square prediction error(29). The accuracy rate of the combined k-nearest neighbors(k-NN) local support vector machines model(i.e. k-nearest neighbors-support vector machine(KNNSVM)) for soil nutrient evaluation was high, comparing to the other five partial support vector machines models investigated. The area under curve value of generalized regression neural network(0.6572) was the highest, and the cross-validation result showed that the generalized regression neural network reached 92.5%.Conclusions: Both the KNNSVM and generalized regression neural network models can be effectively used to evaluate soil nutrient content and quality grades in conjunction with appropriate model variables. Developing a new feasible evaluation method to assess soil nutrient quality for Dacrydium pectinatum, results from this study can be used as a reference for the adaptive management of rare and endangered tree species. This study, however, found some uncertainties in data acquisition and model simulations, which will be investigated in upcoming studies.展开更多
It is difficult to manage the manufacturing hazardous waste (MHW) which is generated from a huge amount of compli- cated sources and causes very serious pollution. Therefore more and more attention has been paid to MH...It is difficult to manage the manufacturing hazardous waste (MHW) which is generated from a huge amount of compli- cated sources and causes very serious pollution. Therefore more and more attention has been paid to MHW pollution. Shanghai, as an industrial and economic center and an international metropolis in China, has a vast industrial system spanning a multitude of sectors, which generates MHW not only in a huge magnitude but also in a large variety of types from complicated sources, resulting in severe pollution. In 2003, the production of MHW in Shanghai is about 3.96 × 105 ton, involving 33 indices. Most of MHW in Shanghai is treated and disposed of, but a significant portion is not handled properly and effectively. This paper carries out in-field investigation on the current status of MHW production and treat- ment in Shanghai, and puts forward scientific proposals that Shanghai should facilitate cleaner production and minimize haz- ardous waste; strictly enforce hazardous waste registration system, strengthen monitoring the certified enterprises; strengthen intent disposal center construction and realize hazardous waste reclama- tion; accelerate establishing the technical criteria and the man- agement policy, promote the research and development on the treatment and disposal technology, and strengthen information management, thus realizing integrated management on MHW pollution.展开更多
In this study, a in vessel aerobic composting method is adopted to investigate the variation rules of various evaluation parameters （temperature, moisture content, pH, organic matter, water soluble ammonia nitrogen, ...In this study, a in vessel aerobic composting method is adopted to investigate the variation rules of various evaluation parameters （temperature, moisture content, pH, organic matter, water soluble ammonia nitrogen, water soluble nitrate nitrogen and germination index） in cocomposting of municipal sludge, kitchen waste and water hyacinth at different proportions. The results show that, in composting, the parameters of moisture content, pH, water soluble ammonia nitrogen and water soluble nitrate nitrogen demonstrate marked dynamic change rules during composting process; the temperature of three groups of compost materials rapidly rise to above 55 ~C within 96h, and last for 3 - 7d, meeting the harmless requirements, and their organic matter degradation rate excess 30%, the GI index is higher than 83%, in line with the requirements on maturity, which proves that the co-composting of municipal sludge, kitchen waste and water hyacinth can realize harmlessness and resource reutilization after composting.展开更多
Plastic pollution has emerged as one of the major global environmental challenges,posing a severe threat to the sustainable development of our society[1].Polycarbonate(PC),one of the most widely used thermoplastic pol...Plastic pollution has emerged as one of the major global environmental challenges,posing a severe threat to the sustainable development of our society[1].Polycarbonate(PC),one of the most widely used thermoplastic polyesters,has been extensively applied across various fields due to its remarkable material properties,with a global annual production capacity of approximately 6 million tons[2,3].However,a considerable proportion of PC inevitably enter the waste stream after use.展开更多
Ionic liquid-catalyzed methanolysis emerges as an efficient technique for transforming PET into premium-grade dimethyl terephthalate(DMT).However,incomplete depolymerization remains a major obstacle to the further ind...Ionic liquid-catalyzed methanolysis emerges as an efficient technique for transforming PET into premium-grade dimethyl terephthalate(DMT).However,incomplete depolymerization remains a major obstacle to the further industrial application of IL-catalyzed PET methanolysis.The proposed method utilized dimethyl carbonate(DMC)as the solvent for the complete methanolysis of waste PET under mild conditions,resulting in pure DMT and ethylene carbonate(EC)within 2.5 h.The use of 1-ethyl-3-methylimidazolium acetate([EMIm][OAc])as the IL catalyst significantly enhanced the reaction efficiency.Spectroscopic analyses using 1 H NMR and FT-IR confirmed the pivotal role of[EMIm][OAc]in establishing multiple hydrogen bonds with the reactants(PET,DMC,and MeOH)and the intermediate[ethylene glycol(EG)]during the catalytic process.This catalytic system exhibited remarkable performance,achieving complete conversion of PET,which resulted in the production of DMT and EC with yields of 99%and 91%,respectively.Moreover,this versatile approach is applicable to the upcycling of a wide variety of commercial polyesters and polycarbonates,underscoring its potential as a comprehensive solution for plastic waste management.展开更多
The inherent stability and durability of polystyrene(PS)make it a valuable material but also complicate its chemical recycling.Oxidative degradation via hydrogen atom transfer(HAT)is a promising route for PS recovery,...The inherent stability and durability of polystyrene(PS)make it a valuable material but also complicate its chemical recycling.Oxidative degradation via hydrogen atom transfer(HAT)is a promising route for PS recovery,yet existing methods suffer from insufficient selectivity toward target products.Herein,we demonstrate an efficient approach to selectively convert PS into benzoic acid(BA)with an impressive yield of 90%.The process uses nitrogen dioxide(NO_(2)),generated in situ from sodium nitrite and acetic acid,as the primary catalyst,with commercially available cobalt chloride(CoCl_(2))as a cocatalyst under mild conditions(180℃,2 bar(1 bar=101 kPa)O_(2)).Mechanistic studies revealed that NO_(2)simultaneously interacts with the Cα-H and Cβ-H bonds of the benzyl group via a HAT mechanism to form a dioxetane intermediate.This intermediate undergoes a ring-opening process,facilitating C-C bond cleavage and subsequent oxidation to BA.Furthermore,the demonstrated applicability of real-world PS waste underscores the potential of this process to advance PS recycling technologies,ultimately helping mitigate the environmental impact of plastic waste.展开更多
基金sponsored by the National Natural Science Foundation of China(Grant Nos.32125027,31930075)Zhejiang A&F University Research and Development Fund(No.2022LFR006).
文摘Moso bamboo(Phyllostachys edulis)forests are a vital resource in subtropical China,known for their high carbon(C)sequestration capacity.However,the dynamic processes of C fluxes within each component(canopy,culm,and soil)and their individual contributions,particularly during on-and off-years,remain unclear.A 2-year field experiment was conducted to investigate the dynamics of C fluxes from the canopy,culm,and soil(partitioned into heterotrophic,rhizome,and stump respiration)and their contributions to net ecosystem productivity(NEP)in a representative Moso bamboo forest in the subtropical region of China.The average annual NEP of the Moso bamboo forest was 7.31±2.76 t C·ha^(-1).Specifically,the canopy's annual net C uptake was 17.30±3.23 tC·ha^(-1),accounting for 237%of NEP.In contrast,C emissions from heterotrophs,culms,rhizomes,and stumps were 5.37±1.20,2.18±1.05,1.29±0.04,and 1.15±0.33 t C·ha^(-1),accounting for73%,30%,18%,and16%of NEP,respectively.The NEP,net cumulative C uptake in the canopy,and C emissions from the respiration of heterotrophs and stumps were all significantly higher during on-years when compared to off-years,whereas C emissions from bamboo culms displayed opposite trends.These findings offer a new approach for quantifying the C budgets of Moso bamboo forests and provide valuable insights into the C cycling processes in forest ecosystems.
基金National Natural Science Foundation of China,No.42371121Joint Fund for Regional Innovation and Development of the National Natural Science Foundation of China,No.U22A20570Science and Technology Innovation Program of Hunan Province,China,No.2022RC4027。
文摘Phenological changes play a central role in regulating seasonal variation in the ecological processes,exerting significant impacts on hydrologic and nutrient cycles,and ultimately influencing ecosystem functioning such as carbon uptake.However,the potential impact mechanisms of phenological events on seasonal carbon dynamics in subtropical regions are under-investigated.These knowledge gaps hinder from accurately linking photosynthetic phenology and carbon sequestration capacity.Using chlorophyll fluorescence remote sensing and productivity data from 2000 to 2019,we found that an advancement in spring phenology increased spring gross(GPP)and net primary productivity(NPP)in subtropical vegetation of China by 2.1 gC m^(-2)yr^(-1)and 1.4 gC m^(-2)yr^(-1),respectively.A delay in autumn phenology increased the autumnal GPP and NPP by 0.4 gC m^(-2)yr^(-1)and 0.2 gC m^(-2)yr^(-1),respectively.Temporally,the contribution of the spring phenology to spring carbon uptake increased significantly during the study period,while this positive contribution showed a nonsignificant trend in summer.In comparison,the later autumn phenology could significantly contribute to the increase in autumnal carbon uptake;however,this contributing effect was weakened.Path analysis indicated that these phenomena have been caused by the increased leaf area and enhanced photosynthesis due to earlier spring and later autumn phenology,respectively.Our results demonstrate the diverse impacts of vegetation phenology on the seasonal carbon sequestration ability and it is imperative to consider such asymmetric effects when modeling ecosystem processes parameterized under future climate change.
基金funded by the National Nature Science Foundation of China (Grant No. 31070440,31270517)China QianRen Program,NSERC-Discovery GrantZhejiang A & F University Research and Development Fund (2012FR023)
文摘Although paid to upward shift response to global phenomenon at low zones did not receive increasing attention has been of plant species in altitude as a warming, research on this altitudinal and low latitudinal enough attention. In this study, an investigation was carried out to test the relationship between the upward spread of Moso bamboo （Phyllostachys pubescens） along altitudinal gradient and the increasing air temperature over the past decade within the Tianmu Mountain region, situated in southeastern China. Results showed that the peak elevation of Moso bamboo population establishment rose by an average of 9.8 m （±2.7 m） during the past decade and significant correlation existed with mean annual temperature （P 〈 0.0001, n = 339） but not with annual precipitation （P = 0.7, n = 339）, indicating that the upward shift of Moso bamboo along altitudinal gradients was driven primarily by warming temperatures. This upward shift could potentially reduce biodiversity by altering the species composition of the ecosystem. However, there is also the potential for increased carbon sequestration capacity of local forest systems, which would produce an additional carbon sink to combat rising atmospheric C02 concentrations and future global warming.
基金supported by the National Natural Science Foundation of China(Grant No.41901117)Natural Science Foundation of Hunan Province,China(Grant No.2020JJ5362)+1 种基金the Outstanding Youth Project of Hu’nan Provincial Education Department(No.18B001)the Natural Sciences and Engineering Research Council of Canada(NSERC)Discover Grant.
文摘Background:Vegetation phenology research has largely focused on temperate deciduous forests,thus limiting our understanding of the response of evergreen vegetation to climate change in tropical and subtropical regions.Results:Using satellite solar-induced chlorophyll fluorescence(SIF)and MODIS enhanced vegetation index(EVI)data,we applied two methods to evaluate temporal and spatial patterns of the end of the growing season(EGS)in subtropical vegetation in China,and analyze the dependence of EGS on preseason maximum and minimum temperatures as well as cumulative precipitation.Our results indicated that the averaged EGS derived from the SIF and EVI based on the two methods(dynamic threshold method and derivative method)was later than that derived from gross primary productivity(GPP)based on the eddy covariance technique,and the time-lag for EGSsif and EGSevi was approximately 2 weeks and 4 weeks,respectively.We found that EGS was positively correlated with preseason minimum temperature and cumulative precipitation(accounting for more than 73%and 62%of the study areas,respectively),but negatively correlated with preseason maximum temperature(accounting for more than 59%of the study areas).In addition,EGS was more sensitive to the changes in the preseason minimum temperature than to other climatic factors,and an increase in the preseason minimum temperature significantly delayed the EGS in evergreen forests,shrub and grassland.Conclusions:Our results indicated that the SIF outperformed traditional vegetation indices in capturing the autumn photosynthetic phenology of evergreen forest in the subtropical region of China.We found that minimum temperature plays a significant role in determining autumn photosynthetic phenology in the study region.These findings contribute to improving our understanding of the response of the EGS to climate change in subtropical vegetation of China,and provide a new perspective for accurately evaluating the role played by evergreen vegetation in the regional carbon budget.
基金sponsored by the National Natural Science Foundation of China,China(Grant Nos.31470529,32125027)Zhejiang A&F University Research and Development Fund,China(Nos.2022LFR006,2021LFR060).
文摘Background: Nitrogen(N) deposition affects soil greenhouse gas(GHG) emissions, while biochar application reduces GHG emissions in agricultural soils. However, it remains unclear whether biochar amendment can alleviate the promoting effects of N input on GHG emissions in forest soils. Here, we quantify the separate and combined effects of biochar amendment(0, 20, and 40 t·ha) and N addition(0, 30, 60, and 90 kg N·ha·yr) on soil GHG fluxes in a long-term field experiment at a Moso bamboo(Phyllostachys edulis) plantation.Results: Low and moderate N inputs(≤60 kg N·ha·yr) significantly increase mean annual soil carbon dioxide(CO) and nitrous oxide(NO) emissions by 17.0%–25.4% and 29.8%–31.2%, respectively, while decreasing methane(CH) uptake by 12.4%–15.9%, leading to increases in the global warming potential(GWP) of soil CHand NO fluxes by 32.4%–44.0%. Moreover, N addition reduces soil organic carbon(C;SOC) storage by 0.2%–6.5%. Compared to the control treatment, biochar amendment increases mean annual soil CO2emissions, CHuptake, and SOC storage by 18.4%–25.4%, 7.6%–15.8%, and 7.1%–13.4%, respectively, while decreasing NO emissions by 17.6%–19.2%, leading to a GWP decrease of 18.4%–21.4%. Biochar amendments significantly enhance the promoting effects of N addition on soil COemissions, while substantially offsetting the promotion of N2O emissions, inhibition of CHuptake, and decreased SOC storage, resulting in a GWP decrease of 9.1%–30.3%.Additionally, soil COand CHfluxes are significantly and positively correlated with soil microbial biomass C(MBC) and pH. Meanwhile, NO emissions have a significant and positive correlation with soil MBC and a negative correlation with pH.Conclusions: Biochar amendment can increase SOC storage and offset the enhanced GWP mediated by elevated N deposition and is, thus, a potential strategy for increasing soil C sinks and decreasing GWPs of soil CHand NO under increasing atmospheric N deposition in Moso bamboo plantations.
基金supported by the National Natural Science Foundation of China(Nos.41175111 and 21177078)the Strategic Pilot Science and Technology Project of the Chinese Academy of Sciences(Class B)(No.XDB05010200)+1 种基金the National Natural Science Foundation of China(No.41265008)Key Discipline Construction Project,Guizhou(No.ZDXK[2016]11)
文摘Size–fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time–of–flight secondary ion mass spectrometry（TOF–SIMS）.The variation characteristics of the surface chemical composition and influencing factors were studied, and the possible sources of these chemical compositions were identified through principal component analysis. The results showed that inorganic components such as crustal elements and sulfate, and organic components such as aliphatic hydrocarbons and oxygen–containing organic groups were present. Some surface components, such as polycyclic aromatic hydrocarbons, heavy metals and fluorides may exert adverse effects on human health. The species and relative percentages of the chemical components varied with particle size, diurnal and pollution progress. During a heavy pollution event, the species and relative percentages of secondary components such as oxygen–containing organic groups and sulfurous compounds increased, indicating that particles aged during this event. The surface chemical composition of the aerosol particles was affected mainly by emissions from coal combustion and motor vehicles. In addition, air pollution, meteorological factors, and air mass transport also exerted a significant effect on the surface chemical composition of aerosol particles.
基金This paper was funded by the Geological Survey Project of China Geological Survey"Comprehensive Geological Survey of Xiamen-Zhangzhou-Quanzhou City"(DD20190303).
文摘The small and medium-sized river basins along southeast coast of China hold comparatively abundant water resources.However,the rapid resources urbanization in recent years has produced a series of water problems such as deterioration of river water quality,water shortage and exacerbated floods,which have constrained urban economic development.By applying the principle of triple supply-demand equilibrium,this paper focuses on the estimation of levels of water supply and demand in 2030 at different guarantee probabilities,with a case study of Xiamen city.The results show that water shortage and inefficient utilization are main problems in the city,as the future water supply looks daunting,and a water shortage may hit nearly 2×10^(8)m^(3)in an extraordinarily dry year.Based on current water supply-demand gap and its trend,this paper proposes countermeasures and suggestions for developing and utilizing groundwater resources and improving the utilization rate of water resources,which can supply as a reference for other southeast middle-to-small-sized basin cities in terms of sustainable water resources and water environment protection.
文摘A new method combining QuEChERS (quick, easy, cheap, effective, rugged and safe) and DLLME (dispersive liquid–liquid microextraction) for the simultaneous determination of residues of ten sulfonylurea herbicide in water using UPLC-MS/MS was developed and validated. Analytes were extracted and purified with QuEChERS and concentrated in chlorobenzene by applying the DLLME procedure. Several extraction parameters were tested, such as volume, extractive solvent by the QuEChERS method and subsequently used for DLLME, selection of extractive solvent and its volume, was tested. The developed method was validated on the basis of international guidelines. Mean recoveries ranged from 81.2 to 104.9%. Repeatability and reproducibility were lower than 10%. Limits of detection (LODs) and quantification (LOQs) were below 0.074 μg/L and 0.244 μg/L, respectively. Decision limit (CCα) and detection capability (CCβ) were calculated and CCβ ranged from 0.101 μg/L (pyrazosulfuron-ethyl) to 0.260 μg/L (nicosulfuron). Finally, when the method was applied to real samples, traces of three compounds were found in 42 samples and only thifensulfuon-methyl was detected above the LOQ in three samples at 0.17-0.20 μg/L.
基金supported by the Project of National Natural Science Foundation of China (Nos.41175111,20677054,21177078)the Strategic Pilot Science and Technology Project of the Chinese Academy of Sciences (Class B) (No.XDB05010200)
文摘Atmospheric aerosol particle samples were collected using an Ambient Eight Stage（Non-Viable） Cascade Impactor Sampler in a typical urban area of Beijing from 27 th Sep.to 5th Oct.,2009.The surface chemistry of these aerosol particles was analyzed using Static Time of Flight-Secondary Ion Mass Spectrometry（Static TOF-SIMS）.The factors influencing surface compositions were evaluated in conjunction with the air pollution levels,meteorological factors,and air mass transport for the sampling period.The results show that a variety of organic ion groups and inorganic ions/ion groups were accumulated on the surfaces of aerosol particles in urban areas of Beijing;and hydrophobic organic compounds with short-or middle-chain alkyl as well as hydrophilic secondary inorganic compounds were observed.All these compounds have the potential to affect the atmospheric behavior of urban aerosol particles.PM1.1–2.1and PM3.3–4.7had similar elements on their surfaces,but some molecules and ionic groups demonstrated differences in Time of Flight-Secondary Ion Mass Spectrometry spectra.This suggests that the quantities of elements varied between PM1.1–2.1and PM3.3–4.7.In particular,more intense research efforts into fluoride pollution are required,because the fluorides on aerosol surfaces have the potential to harm human health.The levels of air pollution had the most significant influence on the surface compositions of aerosol particles in our study.Hence,heavier air pollution was associated with more complex surface compositions on aerosol particles.In addition,wind,rainfall,and air masses from the south also greatly influenced the surface compositions of these urban aerosol particles.
基金funded by the National Water Pollution Control and Management Technology Major Projects (2008ZX07102)
文摘With the enlarging scale and intensifying production of livestock and poultry breeding, the environment pollution becomes increasingly prominent in the Dianchi Lake Basin since 1990s. According to the survey of ＂The First National Census of Pollution Sources＂, occurrence and discharge of pollutants in large-scale livestock and poultry farms in this region were first understood. The pollution characteristics of large-scale live- stock and poultry breeding were also analyzed deeply. On this basis, the significance of pollution control programs for environment protection was investigated from aspects of pollution control policy, technology management and publicity.
基金funded by the National Key R&D Program of China(No.2016YFC0500203)a Natural Sciences and Engineering Research Council of Canada Discovery Grant.
文摘Background:Atmospheric nitrogen(N)deposition is projected to increase in the next few decades,which may have a marked impact on soil-atmosphere CH_(4) fluxes.However,the impacts of increased atmospheric N depositions on soil CH_(4) flux in tropical rainforests are still poorly understood.From January 2015 to December 2018,a field experiment was conducted in a primary tropical montane rainforest(PTMR)and a secondary tropical montane rainforest(STMR)in southern China to quantify the impact of N additions at four levels(N0:0 kg N⋅ha^(-1)⋅year^(-1);N25:25 kg N⋅ha^(-1)⋅year^(-1);N50:50 kg N⋅ha^(-1)⋅year^(-1);N100:100 kg N⋅ha^(-1)⋅year^(-1)on soil CH_(4) flux.Results:Four years of measurements showed clear seasonal variations in CH_(4) flux in all treatment plots for both forest types(PTMR and STMR),with lower rates of soil CH_(4) uptake during the wet season and higher rates of soil CH_(4) uptake during the dry season.Soil CH_(4) uptake rates were significantly and negatively correlated with both soil temperature and soil moisture for both forest types.Annual CH_(4) uptake for the N0 plots from the PTMR and STMR soils were2.20 and1.98 kg N⋅ha^(-1)⋅year^(-1),respectively.At the PTMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 19%,29%,and 36%for the N25,N50,and N100 treatments,respectively.At the STMR site,mean CH_(4) uptake compared with the N0 treatment was reduced by 15%,18%,and 38%for the N25,N50,and N100 treatments,respectively.High level N addition had a stronger inhibitory impact on soil CH_(4) uptake than did the low level N addition.Conclusion:Our data suggest that soil CH_(4) uptake in tropical rainforests is sensitive to N deposition.If atmospheric N deposition continues to increase in the future,the soil CH_(4) sink strength of tropical rainforests may weaken further.
基金a corrosion subprogram of the international project Regional Air Pollution in Developing Countries under the contract No. JT73065.
文摘This paper presents the research on the atmospheric corrosion rates of carbon steel, zinc and copper in Chongqing, which was a corrosion subprogram of an international project, Regional Air Pollution in Developing Countries. We performed field exposure tests of carbon steel, zinc and copper at an urban site Guanyinqiao and a rural site Tieshanping inChongqing, then used grey relational analysis, based on the database of the whole corrosion project, to determine the order of the effect of environmental factors on corrosion rates of tested metals, and established dose-response functions for these three metals. The results showed that the two crucial agents of acidic environment, SO2 and H+, were common factors that contributed most to the corrosion of the tested metals. The established dose-response functions for outdoor carbon steel and zinc are proved applicable to use in Chongqing, but the function for copper needs further modifying. We employed these dose- response functions and general environmental data to elaborate the maps of corrosion rate respectively of carbon steel and zinc by geological information system (GIS) technique which help to identify areas of high corrosion damage risk. An acceptable annual average SO2 level of 21 μg/m3 for carbon steel and that of 61 μg/m3 for zinc are also put forward to control the air pollution impact on atmospheric corrosion in Chongqing urban areas.
基金Supported by National Natural Science Foundation of China (No.40572142)
文摘Based on the laboratory experiments with the saltwater and freshwater replacing each other in the level sand column, taking the kaolin, illite, smectite, bivalent hydrargyrum ion （Hg^2＋） and ＂phenol （C6H5OH） as examples, this paper studies the applications of water sensitivity in situ remediation in saltwater-freshwater transition zone. In the water sensitivity process, the release and migration of clay minerals can make the hydraulic conductivity （HC） decrease and pollutants remove. A new type of low penetrable or impenetrable purdah can be built by adding clay minerals into the sand media to replace the underground concrete impenetrable wall to prevent seawater intrusion, and a number of the heavy metals and organic pollutants in the sand media can be removed by in situ remediation. The results show that the content of kaolin and illite influences the water sensitivity process slightly, and HC of the sand columns descends from 0.011 cm/s to 0.001 4 cm/s and 0.001 2 cm/s respectively even if the content reaches 12% （weight ratio, sic passim）. However, for smectite, HC descends sharply to about 1 × 10^-8 cm/s when its content reaches 4%, and no water can flow through the sand columns beyond 5%. The particle release and migration processes can remove the Hg^2＋ and C6HsOH out of the sand columns efficiently, the removing rate of Hg^2＋ is 31.68% when the freshwater and saltwater are filtered through the sand columns polluted by Hg^2＋, while it is 67.55% when the water sensitivity occurs. With the same method, the removing rates of C6H5OH under the fluid flow and water sensitivity are 55.71% and 43.43% respectively.
基金This researchis supported by Shanghai Education Committee(06-OZ-003)Shanghai Key Subject(p1501)
文摘A mathematic model is developed which is applied to analyze the main factors that affect electrode performance and to account for the process of reaction and mass transfer in gas-diffusion electrodes in contact with liquid electrolytes. Electrochemical Thiele modulus φ^2 and electrochemical effectiveness factor η are introduced to elucidate the effects of diffusion on electrochemical reaction and utilization of the gas-diffusion electrode. Profile of the reactant along axial direction is discussed, dependence of electrode potential V on current density J, are predicated by means of the newly developed mathematical model.
基金financially supported by the Fundamental Research Funds for the Central Non-profit Research Institution of CAF (CAFBB2017ZB004)。
文摘Background: The accurate estimation of soil nutrient content is particularly important in view of its impact on plant growth and forest regeneration. In order to investigate soil nutrient content and quality for the natural regeneration of Dacrydium pectinatum communities in China, designing advanced and accurate estimation methods is necessary.Methods: This study uses machine learning techniques created a series of comprehensive and novel models from which to evaluate soil nutrient content. Soil nutrient evaluation methods were built by using six support vector machines and four artificial neural networks.Results: The generalized regression neural network model was the best artificial neural network evaluation model with the smallest root mean square error(5.1), mean error(-0.85), and mean square prediction error(29). The accuracy rate of the combined k-nearest neighbors(k-NN) local support vector machines model(i.e. k-nearest neighbors-support vector machine(KNNSVM)) for soil nutrient evaluation was high, comparing to the other five partial support vector machines models investigated. The area under curve value of generalized regression neural network(0.6572) was the highest, and the cross-validation result showed that the generalized regression neural network reached 92.5%.Conclusions: Both the KNNSVM and generalized regression neural network models can be effectively used to evaluate soil nutrient content and quality grades in conjunction with appropriate model variables. Developing a new feasible evaluation method to assess soil nutrient quality for Dacrydium pectinatum, results from this study can be used as a reference for the adaptive management of rare and endangered tree species. This study, however, found some uncertainties in data acquisition and model simulations, which will be investigated in upcoming studies.
文摘It is difficult to manage the manufacturing hazardous waste (MHW) which is generated from a huge amount of compli- cated sources and causes very serious pollution. Therefore more and more attention has been paid to MHW pollution. Shanghai, as an industrial and economic center and an international metropolis in China, has a vast industrial system spanning a multitude of sectors, which generates MHW not only in a huge magnitude but also in a large variety of types from complicated sources, resulting in severe pollution. In 2003, the production of MHW in Shanghai is about 3.96 × 105 ton, involving 33 indices. Most of MHW in Shanghai is treated and disposed of, but a significant portion is not handled properly and effectively. This paper carries out in-field investigation on the current status of MHW production and treat- ment in Shanghai, and puts forward scientific proposals that Shanghai should facilitate cleaner production and minimize haz- ardous waste; strictly enforce hazardous waste registration system, strengthen monitoring the certified enterprises; strengthen intent disposal center construction and realize hazardous waste reclama- tion; accelerate establishing the technical criteria and the man- agement policy, promote the research and development on the treatment and disposal technology, and strengthen information management, thus realizing integrated management on MHW pollution.
文摘In this study, a in vessel aerobic composting method is adopted to investigate the variation rules of various evaluation parameters （temperature, moisture content, pH, organic matter, water soluble ammonia nitrogen, water soluble nitrate nitrogen and germination index） in cocomposting of municipal sludge, kitchen waste and water hyacinth at different proportions. The results show that, in composting, the parameters of moisture content, pH, water soluble ammonia nitrogen and water soluble nitrate nitrogen demonstrate marked dynamic change rules during composting process; the temperature of three groups of compost materials rapidly rise to above 55 ~C within 96h, and last for 3 - 7d, meeting the harmless requirements, and their organic matter degradation rate excess 30%, the GI index is higher than 83%, in line with the requirements on maturity, which proves that the co-composting of municipal sludge, kitchen waste and water hyacinth can realize harmlessness and resource reutilization after composting.
基金supported by the Key Research and Development Program of Zhejiang Province(2024C03112 and 2024C03128)the National Natural Science Foundation of China(22376183 and 22209146).
文摘Plastic pollution has emerged as one of the major global environmental challenges,posing a severe threat to the sustainable development of our society[1].Polycarbonate(PC),one of the most widely used thermoplastic polyesters,has been extensively applied across various fields due to its remarkable material properties,with a global annual production capacity of approximately 6 million tons[2,3].However,a considerable proportion of PC inevitably enter the waste stream after use.
基金supported by National Natural Science Foundation of China(22376183,22209146)Key Research and Development Program of Zhejiang Province(2024C03112)+1 种基金the Fundamental Research Funds for the Central Universities(226-2023-00077)Postdoctoral Fellowship Program of CPSF(GZC20232274).
文摘Ionic liquid-catalyzed methanolysis emerges as an efficient technique for transforming PET into premium-grade dimethyl terephthalate(DMT).However,incomplete depolymerization remains a major obstacle to the further industrial application of IL-catalyzed PET methanolysis.The proposed method utilized dimethyl carbonate(DMC)as the solvent for the complete methanolysis of waste PET under mild conditions,resulting in pure DMT and ethylene carbonate(EC)within 2.5 h.The use of 1-ethyl-3-methylimidazolium acetate([EMIm][OAc])as the IL catalyst significantly enhanced the reaction efficiency.Spectroscopic analyses using 1 H NMR and FT-IR confirmed the pivotal role of[EMIm][OAc]in establishing multiple hydrogen bonds with the reactants(PET,DMC,and MeOH)and the intermediate[ethylene glycol(EG)]during the catalytic process.This catalytic system exhibited remarkable performance,achieving complete conversion of PET,which resulted in the production of DMT and EC with yields of 99%and 91%,respectively.Moreover,this versatile approach is applicable to the upcycling of a wide variety of commercial polyesters and polycarbonates,underscoring its potential as a comprehensive solution for plastic waste management.
基金supported by the National Natural Science Foundation of China(22376183 and 22209146)the Key Research and Development Program of Zhejiang Province(2024C03112)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(GZB20230633)。
文摘The inherent stability and durability of polystyrene(PS)make it a valuable material but also complicate its chemical recycling.Oxidative degradation via hydrogen atom transfer(HAT)is a promising route for PS recovery,yet existing methods suffer from insufficient selectivity toward target products.Herein,we demonstrate an efficient approach to selectively convert PS into benzoic acid(BA)with an impressive yield of 90%.The process uses nitrogen dioxide(NO_(2)),generated in situ from sodium nitrite and acetic acid,as the primary catalyst,with commercially available cobalt chloride(CoCl_(2))as a cocatalyst under mild conditions(180℃,2 bar(1 bar=101 kPa)O_(2)).Mechanistic studies revealed that NO_(2)simultaneously interacts with the Cα-H and Cβ-H bonds of the benzyl group via a HAT mechanism to form a dioxetane intermediate.This intermediate undergoes a ring-opening process,facilitating C-C bond cleavage and subsequent oxidation to BA.Furthermore,the demonstrated applicability of real-world PS waste underscores the potential of this process to advance PS recycling technologies,ultimately helping mitigate the environmental impact of plastic waste.
