Rapidly expanding studies investigate the effects of e-commerce on company operations in the retail market.However,the interaction between agri-food e-commerce(AEC)and the traditional agri-food wholesale industry(AWI)...Rapidly expanding studies investigate the effects of e-commerce on company operations in the retail market.However,the interaction between agri-food e-commerce(AEC)and the traditional agri-food wholesale industry(AWI)has not received enough attention in the existing literature.Based on the provincial panel data from 2013 to 2020 in China,this paper examines the effect of AEC on AWI,comprising three dimensions:digitalization(DIGITAL),agrifood e-commerce infrastructure and supporting services(AECI),and agri-food e-commerce economy(AECE).First,AWI and AEC are measured using an entropy-based combination of indicators.The results indicate that for China as a whole,AWI has remained practically unchanged,whereas AEC exhibits a significant rising trend.Second,the findings of the fixed-effect regression reveal that DIGITAL and AECE tend to raise AWI,whereas AECI negatively affects AWI.Third,threshold regression results indicate that AECI tends to diminish AWI with three-stage inhibitory intensity,which manifests as a first increase and then a drop in the inhibition degree.These results suggest that with the introduction of e-commerce for agricultural product circulation,digital development will have catfish effects that tend to stimulate the vitality of the conventional wholesale industry and promote technical progress.Furthermore,the traditional wholesale industry benefits financially from e-commerce even while it diverts part of the traditional wholesale circulation for agricultural products.展开更多
Based on the previous statistical analysis of mesoscale convective systems(MCSs)over the second-step terrain along Yangtze-Huaihe River Valley,eight representative long-lived eastward-propagating MCSs are selected for...Based on the previous statistical analysis of mesoscale convective systems(MCSs)over the second-step terrain along Yangtze-Huaihe River Valley,eight representative long-lived eastward-propagating MCSs are selected for model-based sensitivity testing to investigate the initiation and evolution of these types of MCSs as well as their impact on downstream areas.We subject each MCS to a semi-idealized(CNTL)simulation and a sensitivity(NOLH)simulation that neglects condensational heating in the formation region.The CNTL experiment reveals convection forms in the region downstream of a shortwave trough typified by persistent southwesterly winds in the low-to midtroposphere.Upon merging with other convective systems,moist convection develops into an MCS,which propagates eastward under the influence of mid-tropospheric westerlies,and moves out of the second-step terrain.The MCS then merges with pre-existing local convection over the plains;the merged convection reinforces the cyclonic wind perturbation into a mesoscale vortex at 850 hPa.While this vortex moves eastward to regions with local vortex at 850 hPa,another vortex at 925 hPa is also intensified.Finally,the vortices at 850 and 925 hPa merge together and develop into a mesoscale convective vortex(MCV).In contrast,MCSs fail to form and move eastward in the NOLH experiment.In the absence of eastward-propagating MCSs,moist convection and mesoscale vortices still appear in the plains,but the vortex strength and precipitation intensity are significantly weakened.It is suggested the eastward-propagating MCSs over the second-step terrain significantly impact the development and enhancement of moist convection and vortices in the downstream areas.展开更多
The objective of this study was to prepare tamsulosin hydrochloride-sustained release(TSH-SR)pellets which showed good release stability with frame-controlled method.TSH was added to Eudragit~?NE30D and Eudragit~?L30D...The objective of this study was to prepare tamsulosin hydrochloride-sustained release(TSH-SR)pellets which showed good release stability with frame-controlled method.TSH was added to Eudragit~?NE30D and Eudragit~?L30D-55 polymers to form drug-loaded inner core.Afterwards,enteric Eudragit~?L30D-55 polymer was modified on the surface of it to the final product.Dissolution studies showed that TSH-SR pellets were more stable during the coating process,different curing temperatures and storage conditions compared with TSH pellets produced by film-controlled technique.Appearances and glass transition temperatures(Tgs)of free films and surface morphologies observed by scanning electron microscopy(SEM)of blank sustained release pellets prepared by different ratios of Eudragit~?NE30D and Eudragit~?L30D-55 further indicated that temperature and relative humidity(RH)were the key factors when Eudragit~?NE30D blended with Eudragit~?L30D-55 were applied to sustained/controlled release preparations.In addition,SEM identified the surface morphologies of TSH-SR pellets before and after dissolution,which showed intact surface structure and great correlation with release curve respectively.展开更多
To investigate the impact of particle size on in vitro/vivo performance of praziquantel(PZQ), nanocrystals(NCs) and microcrystals(MCs) of PZQ were prepared using the methods of wet milling and jet milling, respectivel...To investigate the impact of particle size on in vitro/vivo performance of praziquantel(PZQ), nanocrystals(NCs) and microcrystals(MCs) of PZQ were prepared using the methods of wet milling and jet milling, respectively. PZQ NCs and MCs were characterized with dynamic light scattering, laser particle size analyzer, transmission electron microscopy, differential scanning calorimetry, X-ray powder diffraction and fourier transform infrared spectroscopy. The average diameters of PZQ NCs and MCs were 364.4 nm and 3.7 μm, respectively. No change in crystalline form was observed. Dissolution tests were performed in two different media, where the cumulative dissolution and dissolution rate of NCs were significantly improved in comparison with those of MCs and KANGQING~? in non-sink condition. Similarly, oral bioavailability of PZQ NCs in beagle dogs was 1.68( P < 0.05) and 1.83 fold( P < 0.01) higher than that of MCs and KANGQING~? . Considering the advantages of in vitro/vivo performance and facile preparation, PZQ NCs may have a great application in the treatment of schistosomiasis.展开更多
Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body te...Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body temperature(TBB) dataset during May to August 2000–2016(except 2005). The MCSs were divided into eastward-propagating(EP) and quasi-stationary(QS) types, to compare their spatial and temporal distributions and convective intensities, and to identify the favorable synoptic conditions for the formation and evolution of EP MCSs. The results showed that both MCS types occurred most often in July. The EP MCSs were mainly initiated over the eastern regions of the study area, while the QS type mainly originated in the western regions of the study area. Both MCS types mainly formed in the afternoon, but a second peak occurred in the early morning for QS MCSs. The EP MCSs had a larger cloud area at their mature stage and a lower cloud brightness temperature, indicating more intense convection. Additionally, the longer lifetime and further eastward propagation of the EP MCSs meant that they had a great influence on the precipitation over the middle and lower reaches of the Yangtze River. Synoptic circulation analysis demonstrated that the combination of the mid-level low trough east of the Tibetan Plateau(TP), and the western pacific subtropical high(WPSH), favored the formation and eastward propagation of EP MCSs. The positive vertical relative vorticity and stronger vertical wind shear provided dynamic conditions favorable for convective organization and development. Furthermore, a stronger low level jet imported warm and moist air to the eastern edge of, and the regions east of, the second-step terrain. The substantial convergence of water vapor promoted the development and long-lived maintenance of the EP MCSs.展开更多
Microbes play important roles in the transport and transformation of selenium(Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bac...Microbes play important roles in the transport and transformation of selenium(Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides,respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations(MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L.xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles(SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra-or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized Se NPs would have potential applications in agriculture, food, environment and medicine.展开更多
Whether plant coexistence can reduce the impacts of lead (Pb) on crops in agroecosystems has not been well understood. We conducted a factorial experiment to investigate the effects of weeds coexisting with maize (Zea...Whether plant coexistence can reduce the impacts of lead (Pb) on crops in agroecosystems has not been well understood. We conducted a factorial experiment to investigate the effects of weeds coexisting with maize (Zea mays L.) on Pb accumulation in maize and soil microbes at two Pb levels (ambient and 300 mg/kg). Elevated Pb tended to increase the Pb concentration in maize and decreased soil microbial activity (indicated by the average well color development, AWCD), functional group diversity, as well as arbuscular mycorrhizal (AM) colonization and vesicle number of maize. Compared to the monoculture, weeds coexisting with maize reduced the Pb concentrations in the root, leaf, sheath and stem of maize at both seedling and mature stages. In maize-weed mixtures, soil microbial activity and functional group diversity tended to increase for both Pb treatments relative to the monoculture. Furthermore, principal component analysis revealed that the soil microbial community structure changed with the introduction of weeds. The highest Pb accumulation in weeds occurred for the elevated Pb treatment in a three species mixture. The results suggest that multiple plant species coexistence could reduce lead accumulation in crop plants and alleviate the negative impacts on soil microbes in polluted land, thereby highlighting the significance of plant diversity in agroecosystems.展开更多
Diphenylarsinic acid(DPAA)is both the prime starting material and major metabolite of chemical weapons(CWs).Because of its toxicity and the widespread distribution of abandoned CWs in burial site,DPAA sorption by natu...Diphenylarsinic acid(DPAA)is both the prime starting material and major metabolite of chemical weapons(CWs).Because of its toxicity and the widespread distribution of abandoned CWs in burial site,DPAA sorption by natural Fe minerals is of considerable interest.Here we report the first study on DPAA sorption by natural magnetite and siderite using macroscopic sorption kinetics,sequential extraction procedure(SEP)and microscopic extended X-ray absorption fine-structure spectroscopy(EXAFS).Our results show that the sorption pseudo-equilibrated in 60 minutes and that close to 50%and 20%–30%removal can be achieved for magnetite and siderite,respectively,at the initial DPAA concentrations of 4–100 mg/L.DPAA sorption followed pseudo-secondary and intra-particle diffusion kinetics models,and the whole process was mainly governed by intra-particle diffusion and chemical bonding.SEP and EXAFS results revealed that DPAA mainly formed inner-sphere complexes on magnetite(>80%),while on siderite it simultaneously resulted in outer-sphere and inner-sphere complexes.EXAFS analysis further confirmed the formation of inner-sphere bidentate binuclear corner-sharing complexes(^(2)C)for DPAA.Comparison of these results with previous studies suggests that phenyl groups are likely to impact the sorption capacity and structure of DPAA by increasing steric hindrance or affecting the way the central arsenic(As)atom maintains charge balance.These results improve our knowledge of DPAA interactions with Fe minerals,which will help to develop remediation technology and predict the fate of DPAA in soil-water environments.展开更多
Diphenylarsinic acid(DPAA)is a phenyl arsenic compound derived from chemical warfare weapons.Macroscopic and microscopic work on DPAA sorption will provide useful information in predicting the partitioning and mobilit...Diphenylarsinic acid(DPAA)is a phenyl arsenic compound derived from chemical warfare weapons.Macroscopic and microscopic work on DPAA sorption will provide useful information in predicting the partitioning and mobility of DPAA in the soil-water environment.Here,batch experiments and extended X-ray absorption fine structure(EXAFS)spectroscopy were used to investigate the sorption mechanisms of DPAA.The DPAA sorption data from 11 soil types was found to fit the Freundlich equation,and the sorption capacity,Kf,was significantly and positively correlated with oxalateextractable Fe2o3.The Kf values of eight of the 11 untreated soils(1.51113.04)significantly decreased upon removal of amorphous metal(hydr)oxides(0.51-13.37).When both amorphous and crystalline metal(hydr)oxides were removed from the untreated soils,the values either decreased or slightly increased(0.65-3.09).Subsequent removal of soil organic matter from these amorphous and crystalline metal(hydr)oxide-depleted samples led to ftirther decreases in A^f to 0.021.38,with only one exception(Sulfic Aquic-Orthic Halosols).These findings strongly suggest that ligand exchange reactions with amorphous metal(hydr)oxides contribute most to DPAA sorption on soils.EXAFS data provide further evidence that DPAA primarily formed bidentate binuclear(~C)and monodentate mononuclear(1 V)coring-sharing complexes with As-Fe distances of 3.34 and 3.66 A,respectively,on Fe(hydr)oxides.Comparison of these results with earlier studies suggests that 2C and 1 F complexes of DPAA may be favored under low and high surface coverages,respectively,with the formation of 1 V bonds possibly conserving the sorption sites or decreasing the steric hindrance derived from phenyl substituents.展开更多
Facilitation, or positive plant–plant interaction, has received increasing concern from ecologists over the last two decades. Facilitation may occur through direct mitigation of severe environments or indirect mediat...Facilitation, or positive plant–plant interaction, has received increasing concern from ecologists over the last two decades. Facilitation may occur through direct mitigation of severe environments or indirect mediation by a third participant from the same or different trophic levels. The copper(Cu) tolerant species Elsholtzia splendens facilitates the establishment and growth of co-occurring Commelina communis through indirect enrichment of microbial activity. However, whether and how E. splendens impacts the microbial community that is associated with C. communis is less known. We characterized the soil bacterial community in the rhizosphere of C. communis in the absence and presence of E.splendens using PCR-DGGE(polymerase chain reaction-denaturing gradient gel electrophoresis) and sequencing. The result showed that the richness of the bacterial community increased, but diversity and evenness remained similar, in the presence of E. splendens.Chloroflexi, Acidobacteria and Proteobacteria were the most dominant bacteria. The relative abundance of dominant and minor bacterial groups showed distinctly different responses to E. splendens. Principal component analysis and redundancy analysis indicated that variation of the bacterial community was determined by multiple factors and might be driven by the tested soil parameters collectively, or alternatively changed through plant root exudates or other microorganisms. Our results enhance the understanding of how the bacterial community associated with a beneficiary plant responds to a benefactor plant and suggests that the changes of bacterial community composition may have far-reaching influence on plant–soil feedback and the aboveground plant community in the long run.展开更多
基金supported by the Leading Talent Support Program for Agricultural Talents of the Chinese Academy of Agricultural Sciences(TCS2022020)the General program of National Natural Science Foundation of China(1573263)。
文摘Rapidly expanding studies investigate the effects of e-commerce on company operations in the retail market.However,the interaction between agri-food e-commerce(AEC)and the traditional agri-food wholesale industry(AWI)has not received enough attention in the existing literature.Based on the provincial panel data from 2013 to 2020 in China,this paper examines the effect of AEC on AWI,comprising three dimensions:digitalization(DIGITAL),agrifood e-commerce infrastructure and supporting services(AECI),and agri-food e-commerce economy(AECE).First,AWI and AEC are measured using an entropy-based combination of indicators.The results indicate that for China as a whole,AWI has remained practically unchanged,whereas AEC exhibits a significant rising trend.Second,the findings of the fixed-effect regression reveal that DIGITAL and AECE tend to raise AWI,whereas AECI negatively affects AWI.Third,threshold regression results indicate that AECI tends to diminish AWI with three-stage inhibitory intensity,which manifests as a first increase and then a drop in the inhibition degree.These results suggest that with the introduction of e-commerce for agricultural product circulation,digital development will have catfish effects that tend to stimulate the vitality of the conventional wholesale industry and promote technical progress.Furthermore,the traditional wholesale industry benefits financially from e-commerce even while it diverts part of the traditional wholesale circulation for agricultural products.
基金supported by the National Key R&D Program of China(Grant No.2018YFC1507200)the National Natural Science Foundation of China(Grant No.41975057).
文摘Based on the previous statistical analysis of mesoscale convective systems(MCSs)over the second-step terrain along Yangtze-Huaihe River Valley,eight representative long-lived eastward-propagating MCSs are selected for model-based sensitivity testing to investigate the initiation and evolution of these types of MCSs as well as their impact on downstream areas.We subject each MCS to a semi-idealized(CNTL)simulation and a sensitivity(NOLH)simulation that neglects condensational heating in the formation region.The CNTL experiment reveals convection forms in the region downstream of a shortwave trough typified by persistent southwesterly winds in the low-to midtroposphere.Upon merging with other convective systems,moist convection develops into an MCS,which propagates eastward under the influence of mid-tropospheric westerlies,and moves out of the second-step terrain.The MCS then merges with pre-existing local convection over the plains;the merged convection reinforces the cyclonic wind perturbation into a mesoscale vortex at 850 hPa.While this vortex moves eastward to regions with local vortex at 850 hPa,another vortex at 925 hPa is also intensified.Finally,the vortices at 850 and 925 hPa merge together and develop into a mesoscale convective vortex(MCV).In contrast,MCSs fail to form and move eastward in the NOLH experiment.In the absence of eastward-propagating MCSs,moist convection and mesoscale vortices still appear in the plains,but the vortex strength and precipitation intensity are significantly weakened.It is suggested the eastward-propagating MCSs over the second-step terrain significantly impact the development and enhancement of moist convection and vortices in the downstream areas.
文摘The objective of this study was to prepare tamsulosin hydrochloride-sustained release(TSH-SR)pellets which showed good release stability with frame-controlled method.TSH was added to Eudragit~?NE30D and Eudragit~?L30D-55 polymers to form drug-loaded inner core.Afterwards,enteric Eudragit~?L30D-55 polymer was modified on the surface of it to the final product.Dissolution studies showed that TSH-SR pellets were more stable during the coating process,different curing temperatures and storage conditions compared with TSH pellets produced by film-controlled technique.Appearances and glass transition temperatures(Tgs)of free films and surface morphologies observed by scanning electron microscopy(SEM)of blank sustained release pellets prepared by different ratios of Eudragit~?NE30D and Eudragit~?L30D-55 further indicated that temperature and relative humidity(RH)were the key factors when Eudragit~?NE30D blended with Eudragit~?L30D-55 were applied to sustained/controlled release preparations.In addition,SEM identified the surface morphologies of TSH-SR pellets before and after dissolution,which showed intact surface structure and great correlation with release curve respectively.
文摘To investigate the impact of particle size on in vitro/vivo performance of praziquantel(PZQ), nanocrystals(NCs) and microcrystals(MCs) of PZQ were prepared using the methods of wet milling and jet milling, respectively. PZQ NCs and MCs were characterized with dynamic light scattering, laser particle size analyzer, transmission electron microscopy, differential scanning calorimetry, X-ray powder diffraction and fourier transform infrared spectroscopy. The average diameters of PZQ NCs and MCs were 364.4 nm and 3.7 μm, respectively. No change in crystalline form was observed. Dissolution tests were performed in two different media, where the cumulative dissolution and dissolution rate of NCs were significantly improved in comparison with those of MCs and KANGQING~? in non-sink condition. Similarly, oral bioavailability of PZQ NCs in beagle dogs was 1.68( P < 0.05) and 1.83 fold( P < 0.01) higher than that of MCs and KANGQING~? . Considering the advantages of in vitro/vivo performance and facile preparation, PZQ NCs may have a great application in the treatment of schistosomiasis.
基金supported by the National Key R & D Program of China (Grants No. 2018YFC1507200)the National Natural Science Foundation of China (Grants Nos. 41505038, 91637211, 41775046 & 41575045)。
文摘Mesoscale convective systems(MCSs) around the second-step terrain(106°–113°E, 28°–35°N), along the middle reaches of the Yangtze River, were detected, tracked and classified using a black body temperature(TBB) dataset during May to August 2000–2016(except 2005). The MCSs were divided into eastward-propagating(EP) and quasi-stationary(QS) types, to compare their spatial and temporal distributions and convective intensities, and to identify the favorable synoptic conditions for the formation and evolution of EP MCSs. The results showed that both MCS types occurred most often in July. The EP MCSs were mainly initiated over the eastern regions of the study area, while the QS type mainly originated in the western regions of the study area. Both MCS types mainly formed in the afternoon, but a second peak occurred in the early morning for QS MCSs. The EP MCSs had a larger cloud area at their mature stage and a lower cloud brightness temperature, indicating more intense convection. Additionally, the longer lifetime and further eastward propagation of the EP MCSs meant that they had a great influence on the precipitation over the middle and lower reaches of the Yangtze River. Synoptic circulation analysis demonstrated that the combination of the mid-level low trough east of the Tibetan Plateau(TP), and the western pacific subtropical high(WPSH), favored the formation and eastward propagation of EP MCSs. The positive vertical relative vorticity and stronger vertical wind shear provided dynamic conditions favorable for convective organization and development. Furthermore, a stronger low level jet imported warm and moist air to the eastern edge of, and the regions east of, the second-step terrain. The substantial convergence of water vapor promoted the development and long-lived maintenance of the EP MCSs.
基金supported by the National Natural Science Foundation of China(No.41771355)the Anhui Provincial Natural Science Foundation(No.1508085SMC211)the Key Project of Outstanding Young Talent Support Program in Universities of Anhui Province(No.gxyqZD2016025)
文摘Microbes play important roles in the transport and transformation of selenium(Se) in the environment, thereby influencing plant resistance to Se and Se accumulation in plant. The objectives are to characterize the bacteria with high Se tolerance and reduction capacity and explore the significance of microbial origins on their Se tolerance, reduction rate and efficiency. Two bacterial strains were isolated from a naturally occurred Se-rich soil at tea orchard in southern Anhui Province, China. The reduction kinetics of selenite was investigated and the reducing product was characterized using scanning electron microscopy and transmission electron microscopy-energy dispersive spectroscopy. The bacteria were identified as Lysinibacillus xylanilyticus and Lysinibacillus macrolides,respectively, using morphological, physiological and molecular methods. The results showed that the minimal inhibitory concentrations(MICs) of selenite for L. xylanilyticus and L. macrolides were 120 and 220 mmol/L, respectively, while MICs of selenate for L.xylanilyticus and L. macrolides were 800 and 700 mmol/L, respectively. Both strains aerobically reduced selenite with an initial concentration of 1.0 mmol/L to elemental Se nanoparticles(SeNPs) completely within 36 hr. Biogenic SeNPs were observed both inside and outside the cells suggesting either an intra-or extracellular reduction process. Our study implied that the microbes from Se-rich environments were more tolerant to Se and generally quicker and more efficient than those from Se-free habitats in the reduction of Se oxyanions. The bacterial strains with high Se reduction capacity and the biological synthesized Se NPs would have potential applications in agriculture, food, environment and medicine.
基金supported by the National Natural ScienceFoundation of China (No. 30970477)the Key Laboratory of Ministry of Agriculture, the People’s Republic ofChina (No. KYJD09021)+2 种基金the Natural Science Foundation of Zhejiang Province (No. Y307418)the Scienceand Technology Department of Zhejiang Province (No.2007C13063)and the Education Department of ZhejiangProvince (No. Y200805536)
文摘Whether plant coexistence can reduce the impacts of lead (Pb) on crops in agroecosystems has not been well understood. We conducted a factorial experiment to investigate the effects of weeds coexisting with maize (Zea mays L.) on Pb accumulation in maize and soil microbes at two Pb levels (ambient and 300 mg/kg). Elevated Pb tended to increase the Pb concentration in maize and decreased soil microbial activity (indicated by the average well color development, AWCD), functional group diversity, as well as arbuscular mycorrhizal (AM) colonization and vesicle number of maize. Compared to the monoculture, weeds coexisting with maize reduced the Pb concentrations in the root, leaf, sheath and stem of maize at both seedling and mature stages. In maize-weed mixtures, soil microbial activity and functional group diversity tended to increase for both Pb treatments relative to the monoculture. Furthermore, principal component analysis revealed that the soil microbial community structure changed with the introduction of weeds. The highest Pb accumulation in weeds occurred for the elevated Pb treatment in a three species mixture. The results suggest that multiple plant species coexistence could reduce lead accumulation in crop plants and alleviate the negative impacts on soil microbes in polluted land, thereby highlighting the significance of plant diversity in agroecosystems.
基金support of the National Natural Science Foundation of China(Nos.41807117,41230858)the Cultivation Project on Excellent Undergraduates’Thesis(design,create)of Anhui Normal University(No.pyjh2020439)the Project of Innovation and Entrepreneurship Training for College Students(No.202110370060).
文摘Diphenylarsinic acid(DPAA)is both the prime starting material and major metabolite of chemical weapons(CWs).Because of its toxicity and the widespread distribution of abandoned CWs in burial site,DPAA sorption by natural Fe minerals is of considerable interest.Here we report the first study on DPAA sorption by natural magnetite and siderite using macroscopic sorption kinetics,sequential extraction procedure(SEP)and microscopic extended X-ray absorption fine-structure spectroscopy(EXAFS).Our results show that the sorption pseudo-equilibrated in 60 minutes and that close to 50%and 20%–30%removal can be achieved for magnetite and siderite,respectively,at the initial DPAA concentrations of 4–100 mg/L.DPAA sorption followed pseudo-secondary and intra-particle diffusion kinetics models,and the whole process was mainly governed by intra-particle diffusion and chemical bonding.SEP and EXAFS results revealed that DPAA mainly formed inner-sphere complexes on magnetite(>80%),while on siderite it simultaneously resulted in outer-sphere and inner-sphere complexes.EXAFS analysis further confirmed the formation of inner-sphere bidentate binuclear corner-sharing complexes(^(2)C)for DPAA.Comparison of these results with previous studies suggests that phenyl groups are likely to impact the sorption capacity and structure of DPAA by increasing steric hindrance or affecting the way the central arsenic(As)atom maintains charge balance.These results improve our knowledge of DPAA interactions with Fe minerals,which will help to develop remediation technology and predict the fate of DPAA in soil-water environments.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.41807117 and 41230858)the Cultivation Project on Excellent Undergraduates'Thesis(design,create)of Anhui Normal University(No.pyjh2018487)the Innovation and Entrepreneurship Training Project for College Students(No.201910370072)。
文摘Diphenylarsinic acid(DPAA)is a phenyl arsenic compound derived from chemical warfare weapons.Macroscopic and microscopic work on DPAA sorption will provide useful information in predicting the partitioning and mobility of DPAA in the soil-water environment.Here,batch experiments and extended X-ray absorption fine structure(EXAFS)spectroscopy were used to investigate the sorption mechanisms of DPAA.The DPAA sorption data from 11 soil types was found to fit the Freundlich equation,and the sorption capacity,Kf,was significantly and positively correlated with oxalateextractable Fe2o3.The Kf values of eight of the 11 untreated soils(1.51113.04)significantly decreased upon removal of amorphous metal(hydr)oxides(0.51-13.37).When both amorphous and crystalline metal(hydr)oxides were removed from the untreated soils,the values either decreased or slightly increased(0.65-3.09).Subsequent removal of soil organic matter from these amorphous and crystalline metal(hydr)oxide-depleted samples led to ftirther decreases in A^f to 0.021.38,with only one exception(Sulfic Aquic-Orthic Halosols).These findings strongly suggest that ligand exchange reactions with amorphous metal(hydr)oxides contribute most to DPAA sorption on soils.EXAFS data provide further evidence that DPAA primarily formed bidentate binuclear(~C)and monodentate mononuclear(1 V)coring-sharing complexes with As-Fe distances of 3.34 and 3.66 A,respectively,on Fe(hydr)oxides.Comparison of these results with earlier studies suggests that 2C and 1 F complexes of DPAA may be favored under low and high surface coverages,respectively,with the formation of 1 V bonds possibly conserving the sorption sites or decreasing the steric hindrance derived from phenyl substituents.
基金financially supported by the National Natural Science Foundation of China (No. 41001368)Anhui Provincial Natural Science Foundation (No. 1508085SMC211)
文摘Facilitation, or positive plant–plant interaction, has received increasing concern from ecologists over the last two decades. Facilitation may occur through direct mitigation of severe environments or indirect mediation by a third participant from the same or different trophic levels. The copper(Cu) tolerant species Elsholtzia splendens facilitates the establishment and growth of co-occurring Commelina communis through indirect enrichment of microbial activity. However, whether and how E. splendens impacts the microbial community that is associated with C. communis is less known. We characterized the soil bacterial community in the rhizosphere of C. communis in the absence and presence of E.splendens using PCR-DGGE(polymerase chain reaction-denaturing gradient gel electrophoresis) and sequencing. The result showed that the richness of the bacterial community increased, but diversity and evenness remained similar, in the presence of E. splendens.Chloroflexi, Acidobacteria and Proteobacteria were the most dominant bacteria. The relative abundance of dominant and minor bacterial groups showed distinctly different responses to E. splendens. Principal component analysis and redundancy analysis indicated that variation of the bacterial community was determined by multiple factors and might be driven by the tested soil parameters collectively, or alternatively changed through plant root exudates or other microorganisms. Our results enhance the understanding of how the bacterial community associated with a beneficiary plant responds to a benefactor plant and suggests that the changes of bacterial community composition may have far-reaching influence on plant–soil feedback and the aboveground plant community in the long run.
