To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron electrovalencies (Fe^2+-EDTA and Fe^3+-EDTA) and species (Fe-EDTA, F...To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron electrovalencies (Fe^2+-EDTA and Fe^3+-EDTA) and species (Fe-EDTA, Fe(OH)x^32x and FeC6H5O7) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe^3+-EDTA, Fe^2+-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell) was obtained under conditions of 18 μmol/L Fe^2+-EDTA, despite the lower cell density (2.3×10^5 cell/ml) in such condition. Fe^3+-EDTA is more effective than Fe^2+-EDTA in improving the cell growth. Especially, the maximal steady-state cell density, 2.9×10^5 cell/ml was obtained at 18 μmol/L Fe^3+-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH)x^32x, FeC6H5O7) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC6H5O7 performed the best. Under the condition of a higher concentration (36 μmol/L) of FeC6H5O7, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC6H5O7, Fe(OH)x^32x and EDTA-Fe.展开更多
Chlorite(ClO_(2)-)is the by-product of the water treatment process carried out using chlorine dioxide(ClO_(2))as an effective disinfectant and oxidant;however,the reactivation of ClO_(2)has commonly been overlooked.H...Chlorite(ClO_(2)-)is the by-product of the water treatment process carried out using chlorine dioxide(ClO_(2))as an effective disinfectant and oxidant;however,the reactivation of ClO_(2)has commonly been overlooked.Herein,it was unprecedentedly found that ClO_(2)could be activated by iron species(Feb:Fe0,FeII,or FeIII),which contributed to the synchronous removal of ClO_(2)and selective oxidative treatment of organic contaminants.However,the above-mentioned activation process presented intensive Ht-dependent reactivity.The introduction of Feb significantly shortened the autocatalysis process via the accumulation of Clor ClOduring the protonation of ClO_(2)driven by ultrasonic field.Furthermore,it was found that the interdependent high-valent-Fe-oxo and ClO_(2),after identification,were the dominant active species for accelerating the oxidation process.Accordingly,the unified mechanisms based on coordination catalysis([FeN(H_(2)O)a(ClOxm)b]nt-P)were putative,and this process was thus used to account for the pollutant removal by the Feb-activated protonated ClO_(2).This study pioneers the activation of ClO_(2)for water treatment and provides a novel strategy for“waste treating waste”.Derivatively,this activation process further provides the preparation methods for sulfones and ClO_(2),including the oriented oxidation of sulfoxides to sulfones and the production of ClO_(2) for on-site use.展开更多
Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of ...Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of hydrogen sulfide(SOH_(2)S) to elemental sulfur(S) has emerged as a sustainable and environmentally friendly solution.Due to its unique properties,iron oxide has been extensively investigated as a catalyst for SOH_(2)S;however,rapid deactivation has remained a significant drawback.The causes of iron oxide-based catalysts deactivation mechanisms in SOH_(2)S,including sulfur or sulfate deposition,the transformation of iron species,sintering and excessive oxygen vacancy formation,and active site loss,are thoroughly examined in this review.By focusing on the deactivation mechanisms,this review aims to provide valuable insights into enhancing the stability and efficiency of iron-based catalysts for SOH_(2)S.展开更多
Organic-inorganic interactions occurring in petroleum-related mud volcanoes can help predict the chemical processes that are responsible for methane emissions to the atmosphere. Seven samples of mud breccia directly e...Organic-inorganic interactions occurring in petroleum-related mud volcanoes can help predict the chemical processes that are responsible for methane emissions to the atmosphere. Seven samples of mud breccia directly ejected from one crater were collected in the Dushanzi mud volcano, along with one argillite sample of the original reddish host rocks distal from the crater, for comparison purposes. The mineral and chemical compositions as well as iron species of all samples were determined using XRD, XRF and M?ssbauer spectroscopy, respectively. The results indicate that a series of marked reactions occurred in the mud volcano systems, more specifically in the mud breccia when compared to the original rocks. Changes mainly included:(1) some conversion of clay minerals from smectite into chlorite and illite, and the precipitation of secondary carbonate minerals such as calcite and siderite;(2) silicon depletion and significant elemental enrichment of iron, manganese, magnesium, calcium and phosphorus; and(3) transformation of iron from ferric species in hematite and smectite into ferrous species in siderite, chlorite and illite. These geochemical reactions likely induced the color changes of the original reddish Neogene argillite to the gray or black mud breccia, as a result of reduction of elements and/or alteration of minerals associated with the oxidation of hydrocarbons. Our results also suggest that greenhouse gases emitted from the mud volcanoes are lowered through a series of methane oxidation reactions and carbon fixation(i.e., through carbonate precipitation).展开更多
Superparamagnetic iron oxide nanoparticles (SPIONs) are one of the most versatile and safe nanoparticles in a wide variety of biomedical applications. In the past decades, considerable efforts have been made to inve...Superparamagnetic iron oxide nanoparticles (SPIONs) are one of the most versatile and safe nanoparticles in a wide variety of biomedical applications. In the past decades, considerable efforts have been made to investigate the potential adverse biological effects and safety issues associated with SPIONs, which is essential for the development of next-generation SPIONs and for continued progress in translational research. In this mini review, we summarize recent developments in toxicity studies on SPIONs, focusing on the relationship between the physicochemical properties of SPIONs and their induced toxic biological responses for a better toxicological understanding of SPIONs.展开更多
Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine(CBZ).However,metal phthalocyanine tends to undergo their own dimerization or polymerization,thereby reducing their activ...Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine(CBZ).However,metal phthalocyanine tends to undergo their own dimerization or polymerization,thereby reducing their activity points and affecting their catalytic properties.In this study,a catalytic system consisting of O-bridged iron perfluorophthalocyanine dimers(FePcF16-O-FePcF16),multi-walled carbon nanotubes(MWCNTs)and H2O_(2) was proposed.The results showed MWCNTs loaded with FePcF16-O-FePcF16 can achieve excellent degradation of CBZ with smaller dosages of FePcF16-O-FePcF16 and H2O_(2),and milder reaction temperatures.In addition,the results of experiments revealed the reaction mechanism of non-hydroxyl radicals.The highly oxidized high-valent iron-oxo(Fe(IV)=O)species was the main reactive species in the FePcF16-O-FePcF16/MWCNTs/H2O_(2) system.It is noteworthy that MWCNTs can improve the dispersion of FePcF16-O-FePcF16,contributing to the production of highly oxidized Fe(IV)=O.Then,the pathway of CBZ oxidative degradation was speculated,and the study results also provide new ideas for metal phthalocyanine-loaded carbon materials to degrade emerging pollutants.展开更多
Wetland reclamation has been ongoing in the Sanjiang Plain since the mid-1950s,which has resulted in major changes in wetlands and the agriculture ecosystem in the region that have influenced the iron output to the Se...Wetland reclamation has been ongoing in the Sanjiang Plain since the mid-1950s,which has resulted in major changes in wetlands and the agriculture ecosystem in the region that have influenced the iron output to the Sea of Okhotsk and limited the primary productivity in the North Pacific Ocean.This study was conducted to investigate the chemical forms of iron in different aquatic environments(agricultural water including groundwater,paddy water,and canal water;wetland water including marsh water,marsh streams,and main streams) with the cross-flow filtration method to reveal the transportation and transformation characteristics of iron in response to major land use changes.In addition,the factors affecting iron behavior in different water bodies were reviewed.In marsh water and streams,the concentrations of dissolved iron were higher due to the high organic matter contents and marsh water becoming the main iron source for river water.The conversion of dissolved iron into acid-labile iron occurred during the discharge of wetland water into marsh rivers.Iron primarily existed in both the >0.7 and <0.01 μm size fractions,accounting for about 58.3% and 26.4% of the total dissolved iron,respectively.In agricultural irrigation systems,ferrous ion entered the paddy fields from groundwater,and a fraction of this ferrous iron was subsequently converted into high molecular weight and medium molecular weight iron(colloid iron) in paddy and canal water.However,the concentrations of total dissolved iron decreased by 62.5% from underground to the surface due to the formation of precipitates.Despite this,water discharge in agriculture is still an important iron source for rivers and has the potential to supplement iron due to its higher acid-labile iron concentrations.Land use and cover change and agricultural irrigation increased the iron content of surface soil,but reduced the output of iron in water systems.Overall,the concentration of total dissolved iron in water systems has been reduced to 42.6% by wetland reclamation.展开更多
Chemical forms, reactivities and transformation of iron fractions in marshy waters were investigated with cross-flow filtration technique to study the iron environmental behavior. Iron fractions were divided into four...Chemical forms, reactivities and transformation of iron fractions in marshy waters were investigated with cross-flow filtration technique to study the iron environmental behavior. Iron fractions were divided into four parts: acid-labile iron (pre-acidification of unfiltered marshy water samples, 〉 0.7 μm), high-molecular-weight iron (0.7-0.05 μm), medium-molecular-weight iron (0.05-0.01 μm), and low-molecular-weight iron (〈 0.01μm). The cross-flow filtration suggested that iron primarily exist in both the 〉 0.7 μm and 〈 0.01 μm size fractions in marshy waters. Rainfall is the key for rain-fed wetland to determine fate of iron by changing the aquatic biochemical conditions. By monitoring the variation of iron concentrations and fractions over three years, it was found that dissolved iron and acid-labile iron concentrations exhibit a large variation extent under different annual rainfalls from 2006 to 2008. The seasonal variation for iron species proved that the surface temperature could control some conversion reactions of iron in marshy waters. Low- molecular-weight iron would convert to acid-labile iron gradually with temperature decreasing. The photochemical reactions of iron fractions, especially low-molecular-weight iron had occurred under solar irradiation. The relative proportion of low-molecular-weight in total dissolved iron ranging from 28.3% to 43.2% were found during the day time, which proved that the observed decreasing concentration of acid lability iron was caused by its degradation to low molecular weight iron.展开更多
Carbon materials(e.g.,pyrogenic carbon(PyC))are widely used in agricultural soils and can participate in various biogeochemical processes,including iron(Fe)cycling.In soils,Fe (Ⅱ)species have been proposed as the mai...Carbon materials(e.g.,pyrogenic carbon(PyC))are widely used in agricultural soils and can participate in various biogeochemical processes,including iron(Fe)cycling.In soils,Fe (Ⅱ)species have been proposed as the main active contributor to produce reactive oxygen species(ROS),which are involved in various biogeochemical processes.However,the effects of PyC on the transformation of different Fe species in soils and the associated production of ROS are rarely investigated.This study examined the influence of PyC(pyrolyzed at 300-700℃)on Fe (Ⅱ)/Fe(Ⅲ)cycling and hydroxyl radical(·OH)production during redox fluctuations of paddy soils.Results showed that the reduction of Fe(Ⅲ)in soils was facilitated by PyC during anoxic incubation,which was ascribed to the increased abundance of dissimilatory Fe(Ⅲ)-reducing microorganisms(biotic reduction)and the electron exchange capacity of PyC(abiotic reduction).During oxygenation,PyC and higher soil pH promoted the oxidation of active Fe (Ⅱ)species(e.g.,exchangeable and low-crystalline Fe (Ⅱ)),which consequently induced higher yield of·OH and further led to degradation of imidacloprid and inactivation of soil microorganisms.Our results demonstrated that PyC accelerated Fe (Ⅱ)/Fe(Ⅲ)cycling and·OH production during redox fluctuations of paddy soils(especially those with low content of soil organic carbon),providing a new insight for remediation strategies in agricultural fields contaminated with organic pollutants.展开更多
b-FeOOH nanorods were prepared by a poly ethylene glycol(PEG) assisted precipitation of FeCl_3·6 H_2O aqueous solution with urea. Na_2CO_3 aqueous solution was introduced to maintain their shapes under annealing....b-FeOOH nanorods were prepared by a poly ethylene glycol(PEG) assisted precipitation of FeCl_3·6 H_2O aqueous solution with urea. Na_2CO_3 aqueous solution was introduced to maintain their shapes under annealing. The one-dimensional porous iron oxide nanorods were synthesized successfully. The asprepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, N_2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The hydrogenation of nitrobenzene to aniline was taken as probe reaction to evaluate their catalytic performance. FeOOH(iron oxides hydroxide) nanorods, fabricated by annealing b-FeOOH nanorods at 250℃ in Ar atmosphere for 4h, exhibited high catalytic activity for the transfer hydrogenation of nitrobenzene to aniline with hydrazine hydrate as hydrogen donors.展开更多
As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic spec...As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors(p H, relative humidity(RH), humic acid(HA), trisodium citrate, and additional iron ions) and the contributions of reactive oxygen species(ROS, mainly HO^- and HO2^-/O2^-) to photooxidation of As(Ⅲ) to As(Ⅴ) on kaolinite surfaces under UV irradiation(λ = 365 nm)were investigated. Results showed that lower p H facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate.Promotion or inhibition of As(Ⅲ) photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe^2+competed with As(Ⅲ) for oxidation by ROS. Experiments on scavengers indicated that the HOUradical was the predominant oxidant in this system.Experiments on actual soil surfaces proved the occurrence of As(Ⅲ) photooxidation in real topsoil. This work demonstrates that the photooxidation process of As(Ⅲ) on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As(Ⅲ).展开更多
基金Supported by Xiamen Scientific and Technologic Projects (No. 3052Z20031086)Xiamen University Alumni Association Foundation in Singaporethe First National College Students Innovative Experimental Project
文摘To increase the cell concentration and the accumulation of astaxanthin in the cultivation of Haematococcus pluvialis, effects of different iron electrovalencies (Fe^2+-EDTA and Fe^3+-EDTA) and species (Fe-EDTA, Fe(OH)x^32x and FeC6H5O7) addition on cell growth and accumulation of astaxanthin were studied. Results show that different iron electrovalencies have various effects on cell growth and astaxanthin accumulation of H. pluvialis. Compared with Fe^3+-EDTA, Fe^2+-EDTA stimulate more effectively the formation of astaxanthin. The maximum astaxanthin content (30.70 mg/g biomass cell) was obtained under conditions of 18 μmol/L Fe^2+-EDTA, despite the lower cell density (2.3×10^5 cell/ml) in such condition. Fe^3+-EDTA is more effective than Fe^2+-EDTA in improving the cell growth. Especially, the maximal steady-state cell density, 2.9×10^5 cell/ml was obtained at 18 μmol/L Fe^3+-EDTA addition. On the other hand, all the various species of iron (EDTA-Fe, Fe(OH)x^32x, FeC6H5O7) are capable to improve the growth of the algae and astaxanthin production. Among the three iron species, FeC6H5O7 performed the best. Under the condition of a higher concentration (36 μmol/L) of FeC6H5O7, the cell density and astaxanthin production is 2 and 7 times higher than those of iron-limited group, respectively. The present study demonstrates that the effects of the stimulation with different iron species increased in the order of FeC6H5O7, Fe(OH)x^32x and EDTA-Fe.
基金supported by the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(2019DX08)National Natural Science Foundation of China(52100036),Natural Science Foundation of Shan-dong Province of China(ZR20210E119)+1 种基金Open Project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(QA202140)Scientific Research Foundation of Harbin Institute of Technology at Weihai(HIT(WH)2019).
文摘Chlorite(ClO_(2)-)is the by-product of the water treatment process carried out using chlorine dioxide(ClO_(2))as an effective disinfectant and oxidant;however,the reactivation of ClO_(2)has commonly been overlooked.Herein,it was unprecedentedly found that ClO_(2)could be activated by iron species(Feb:Fe0,FeII,or FeIII),which contributed to the synchronous removal of ClO_(2)and selective oxidative treatment of organic contaminants.However,the above-mentioned activation process presented intensive Ht-dependent reactivity.The introduction of Feb significantly shortened the autocatalysis process via the accumulation of Clor ClOduring the protonation of ClO_(2)driven by ultrasonic field.Furthermore,it was found that the interdependent high-valent-Fe-oxo and ClO_(2),after identification,were the dominant active species for accelerating the oxidation process.Accordingly,the unified mechanisms based on coordination catalysis([FeN(H_(2)O)a(ClOxm)b]nt-P)were putative,and this process was thus used to account for the pollutant removal by the Feb-activated protonated ClO_(2).This study pioneers the activation of ClO_(2)for water treatment and provides a novel strategy for“waste treating waste”.Derivatively,this activation process further provides the preparation methods for sulfones and ClO_(2),including the oriented oxidation of sulfoxides to sulfones and the production of ClO_(2) for on-site use.
基金supported by Thailand Science Research and Innovation Fund Chulalongkorn University,Thailand(IND66210014)。
文摘Hydrogen sulfide(H_(2)S) not only presents significant environmental concerns but also induces severe corrosion in industrial equipment,even at low concentrations.Among various technologies,the selective oxidation of hydrogen sulfide(SOH_(2)S) to elemental sulfur(S) has emerged as a sustainable and environmentally friendly solution.Due to its unique properties,iron oxide has been extensively investigated as a catalyst for SOH_(2)S;however,rapid deactivation has remained a significant drawback.The causes of iron oxide-based catalysts deactivation mechanisms in SOH_(2)S,including sulfur or sulfate deposition,the transformation of iron species,sintering and excessive oxygen vacancy formation,and active site loss,are thoroughly examined in this review.By focusing on the deactivation mechanisms,this review aims to provide valuable insights into enhancing the stability and efficiency of iron-based catalysts for SOH_(2)S.
基金partially supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China(2016ZX05007001-004)the National Natural Science Foundation of China(41273112+3 种基金414021294102012400241402298)CAS"Light of West China"Program and Chinese Academy of Sciences Visiting Professorship for Senior International Scientists(2015VEA032)
文摘Organic-inorganic interactions occurring in petroleum-related mud volcanoes can help predict the chemical processes that are responsible for methane emissions to the atmosphere. Seven samples of mud breccia directly ejected from one crater were collected in the Dushanzi mud volcano, along with one argillite sample of the original reddish host rocks distal from the crater, for comparison purposes. The mineral and chemical compositions as well as iron species of all samples were determined using XRD, XRF and M?ssbauer spectroscopy, respectively. The results indicate that a series of marked reactions occurred in the mud volcano systems, more specifically in the mud breccia when compared to the original rocks. Changes mainly included:(1) some conversion of clay minerals from smectite into chlorite and illite, and the precipitation of secondary carbonate minerals such as calcite and siderite;(2) silicon depletion and significant elemental enrichment of iron, manganese, magnesium, calcium and phosphorus; and(3) transformation of iron from ferric species in hematite and smectite into ferrous species in siderite, chlorite and illite. These geochemical reactions likely induced the color changes of the original reddish Neogene argillite to the gray or black mud breccia, as a result of reduction of elements and/or alteration of minerals associated with the oxidation of hydrocarbons. Our results also suggest that greenhouse gases emitted from the mud volcanoes are lowered through a series of methane oxidation reactions and carbon fixation(i.e., through carbonate precipitation).
基金Project supported by the Major State Basic Research Development Program of China(Grant Nos.2013CB733802 and 2014CB744503)the National Natural Science Foundation of China(Grant Nos.81101101 and 51273165)+1 种基金the Key Project of Chinese Ministry of Education(Grant No.212149)the Fundamental Research Funds for the Central Universities,China(Grant Nos.2013121039 and ZK1002)
文摘Superparamagnetic iron oxide nanoparticles (SPIONs) are one of the most versatile and safe nanoparticles in a wide variety of biomedical applications. In the past decades, considerable efforts have been made to investigate the potential adverse biological effects and safety issues associated with SPIONs, which is essential for the development of next-generation SPIONs and for continued progress in translational research. In this mini review, we summarize recent developments in toxicity studies on SPIONs, focusing on the relationship between the physicochemical properties of SPIONs and their induced toxic biological responses for a better toxicological understanding of SPIONs.
基金the National Natural Science Foundation of China(No.51703201)Zhejiang Provincial Natural Science Foundation of China(No.LQ17E030003)。
文摘Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine(CBZ).However,metal phthalocyanine tends to undergo their own dimerization or polymerization,thereby reducing their activity points and affecting their catalytic properties.In this study,a catalytic system consisting of O-bridged iron perfluorophthalocyanine dimers(FePcF16-O-FePcF16),multi-walled carbon nanotubes(MWCNTs)and H2O_(2) was proposed.The results showed MWCNTs loaded with FePcF16-O-FePcF16 can achieve excellent degradation of CBZ with smaller dosages of FePcF16-O-FePcF16 and H2O_(2),and milder reaction temperatures.In addition,the results of experiments revealed the reaction mechanism of non-hydroxyl radicals.The highly oxidized high-valent iron-oxo(Fe(IV)=O)species was the main reactive species in the FePcF16-O-FePcF16/MWCNTs/H2O_(2) system.It is noteworthy that MWCNTs can improve the dispersion of FePcF16-O-FePcF16,contributing to the production of highly oxidized Fe(IV)=O.Then,the pathway of CBZ oxidative degradation was speculated,and the study results also provide new ideas for metal phthalocyanine-loaded carbon materials to degrade emerging pollutants.
基金supported by National Basic Research Program of China (Grant No. 2004CB418502)
文摘Wetland reclamation has been ongoing in the Sanjiang Plain since the mid-1950s,which has resulted in major changes in wetlands and the agriculture ecosystem in the region that have influenced the iron output to the Sea of Okhotsk and limited the primary productivity in the North Pacific Ocean.This study was conducted to investigate the chemical forms of iron in different aquatic environments(agricultural water including groundwater,paddy water,and canal water;wetland water including marsh water,marsh streams,and main streams) with the cross-flow filtration method to reveal the transportation and transformation characteristics of iron in response to major land use changes.In addition,the factors affecting iron behavior in different water bodies were reviewed.In marsh water and streams,the concentrations of dissolved iron were higher due to the high organic matter contents and marsh water becoming the main iron source for river water.The conversion of dissolved iron into acid-labile iron occurred during the discharge of wetland water into marsh rivers.Iron primarily existed in both the >0.7 and <0.01 μm size fractions,accounting for about 58.3% and 26.4% of the total dissolved iron,respectively.In agricultural irrigation systems,ferrous ion entered the paddy fields from groundwater,and a fraction of this ferrous iron was subsequently converted into high molecular weight and medium molecular weight iron(colloid iron) in paddy and canal water.However,the concentrations of total dissolved iron decreased by 62.5% from underground to the surface due to the formation of precipitates.Despite this,water discharge in agriculture is still an important iron source for rivers and has the potential to supplement iron due to its higher acid-labile iron concentrations.Land use and cover change and agricultural irrigation increased the iron content of surface soil,but reduced the output of iron in water systems.Overall,the concentration of total dissolved iron in water systems has been reduced to 42.6% by wetland reclamation.
基金support by the Knowledge Innovation Project of Chinese Academy of Sciences (No. KZCX2- YW-Q06-03)the National Natural Science Foundation of China (No. 40901128)
文摘Chemical forms, reactivities and transformation of iron fractions in marshy waters were investigated with cross-flow filtration technique to study the iron environmental behavior. Iron fractions were divided into four parts: acid-labile iron (pre-acidification of unfiltered marshy water samples, 〉 0.7 μm), high-molecular-weight iron (0.7-0.05 μm), medium-molecular-weight iron (0.05-0.01 μm), and low-molecular-weight iron (〈 0.01μm). The cross-flow filtration suggested that iron primarily exist in both the 〉 0.7 μm and 〈 0.01 μm size fractions in marshy waters. Rainfall is the key for rain-fed wetland to determine fate of iron by changing the aquatic biochemical conditions. By monitoring the variation of iron concentrations and fractions over three years, it was found that dissolved iron and acid-labile iron concentrations exhibit a large variation extent under different annual rainfalls from 2006 to 2008. The seasonal variation for iron species proved that the surface temperature could control some conversion reactions of iron in marshy waters. Low- molecular-weight iron would convert to acid-labile iron gradually with temperature decreasing. The photochemical reactions of iron fractions, especially low-molecular-weight iron had occurred under solar irradiation. The relative proportion of low-molecular-weight in total dissolved iron ranging from 28.3% to 43.2% were found during the day time, which proved that the observed decreasing concentration of acid lability iron was caused by its degradation to low molecular weight iron.
基金National Natural Science Foundation of China(No.42130707,42107382,42022049)Natural Science Foundation of Jiangsu Province(BK20200323).
文摘Carbon materials(e.g.,pyrogenic carbon(PyC))are widely used in agricultural soils and can participate in various biogeochemical processes,including iron(Fe)cycling.In soils,Fe (Ⅱ)species have been proposed as the main active contributor to produce reactive oxygen species(ROS),which are involved in various biogeochemical processes.However,the effects of PyC on the transformation of different Fe species in soils and the associated production of ROS are rarely investigated.This study examined the influence of PyC(pyrolyzed at 300-700℃)on Fe (Ⅱ)/Fe(Ⅲ)cycling and hydroxyl radical(·OH)production during redox fluctuations of paddy soils.Results showed that the reduction of Fe(Ⅲ)in soils was facilitated by PyC during anoxic incubation,which was ascribed to the increased abundance of dissimilatory Fe(Ⅲ)-reducing microorganisms(biotic reduction)and the electron exchange capacity of PyC(abiotic reduction).During oxygenation,PyC and higher soil pH promoted the oxidation of active Fe (Ⅱ)species(e.g.,exchangeable and low-crystalline Fe (Ⅱ)),which consequently induced higher yield of·OH and further led to degradation of imidacloprid and inactivation of soil microorganisms.Our results demonstrated that PyC accelerated Fe (Ⅱ)/Fe(Ⅲ)cycling and·OH production during redox fluctuations of paddy soils(especially those with low content of soil organic carbon),providing a new insight for remediation strategies in agricultural fields contaminated with organic pollutants.
基金the financial support provided by the National Natural Science Foundation of China (Nos. 91545119,21761132025, 21773269, 21703262, and 51521091)Youth Innovation Promotion Association CAS (No. 2015152)"Strategic Priority Research Program" of the Chinese Academy of Sciences (No. XDA09030103)
文摘b-FeOOH nanorods were prepared by a poly ethylene glycol(PEG) assisted precipitation of FeCl_3·6 H_2O aqueous solution with urea. Na_2CO_3 aqueous solution was introduced to maintain their shapes under annealing. The one-dimensional porous iron oxide nanorods were synthesized successfully. The asprepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, N_2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The hydrogenation of nitrobenzene to aniline was taken as probe reaction to evaluate their catalytic performance. FeOOH(iron oxides hydroxide) nanorods, fabricated by annealing b-FeOOH nanorods at 250℃ in Ar atmosphere for 4h, exhibited high catalytic activity for the transfer hydrogenation of nitrobenzene to aniline with hydrazine hydrate as hydrogen donors.
基金supported by the National Natural Science Foundation of China(Nos.21077080,21477090)
文摘As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors(p H, relative humidity(RH), humic acid(HA), trisodium citrate, and additional iron ions) and the contributions of reactive oxygen species(ROS, mainly HO^- and HO2^-/O2^-) to photooxidation of As(Ⅲ) to As(Ⅴ) on kaolinite surfaces under UV irradiation(λ = 365 nm)were investigated. Results showed that lower p H facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate.Promotion or inhibition of As(Ⅲ) photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe^2+competed with As(Ⅲ) for oxidation by ROS. Experiments on scavengers indicated that the HOUradical was the predominant oxidant in this system.Experiments on actual soil surfaces proved the occurrence of As(Ⅲ) photooxidation in real topsoil. This work demonstrates that the photooxidation process of As(Ⅲ) on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As(Ⅲ).