China’s lakes are plagued by cadmium(Cd)pollution.Dissolved organic matter(DOM)significantly regulates Cd(II)transport properties at the sediment-water interface.Understanding the effects of different DOM components ...China’s lakes are plagued by cadmium(Cd)pollution.Dissolved organic matter(DOM)significantly regulates Cd(II)transport properties at the sediment-water interface.Understanding the effects of different DOM components on the transportation properties of Cd(II)at the sediment-water interface is essential.In this study,typical DOM from different sources was selected to study Cd(II)mobility at the sediment-water interface.Results showed that terrestrial-derived DOM(fulvic acids,FA)and autochthonous-derived DOM(α-amylase,B1)inhibit Cd(II)sequestration by sediments(42.5%and 5.8%,respectively),while anthropogenic-derived DOM(sodium dodecyl benzene sulfonate,SDBS)increased the Cd(II)adsorption capacity by sediments by 2.8%.Fluorescence quenching coupling with parallel factor analysis(EEM-PARAFAC)was used to characterize different DOM components.The results showed that FA contains three kinds of components(C1,C3:protein-like components,C2:humic-like components);SDBS contains two kinds of components(C1,C2:protein-like components);B1 contains three kinds of components(C1,C2:protein-like components,C3:humic-like components).Three complex reaction modelswere used to characterize the ability of Cd(II)complex with DOM,and it was found that the humic-like component could hardly be complex with Cd(II).Accordingly,humic-like components compete for Cd(II)adsorption sites on the sediment surface and inhibit Cd(II)adsorption fromsediments.Fourier transform infrared spectroscopy(FTIR)of the sediment surface before and after Cd(II)addition was analyzed and proved the competitive adsorption theory.This study provides a better understanding of the Cd(II)mobilization behavior at the sediment-water interface and indicates that the input of humic-like DOM will increase the bioavailability of Cd.展开更多
Polybrominated biphenyl ethers(PBDEs)and polycyclic aromatic hydrocarbons(PAHs)are commonly detected contaminants at e-waste recycling sites.Against the conventional wisdom that PBDEs and PAHs are highly immobile and ...Polybrominated biphenyl ethers(PBDEs)and polycyclic aromatic hydrocarbons(PAHs)are commonly detected contaminants at e-waste recycling sites.Against the conventional wisdom that PBDEs and PAHs are highly immobile and persist primarily in shallowsurface soils,increasing evidence shows that these compounds can leach into the groundwater.Herein,we compare the leachabilities of PBDEs vs.PAHs from contaminated soils collected at an e-waste recycling site in Tianjin,China.Considerable amounts of BDE-209(0.3–2 ng/L)and phenanthrene(42–106 ng/L),the most abundant PBDE and PAH at the site,are detected in the effluents of columns packed with contaminated soils,with the specific concentrations varying with hydrodynamic and solution chemistry conditions.Interestingly,the leaching potential of BDE-209 appears to be closely related to the release of colloidal mineral particles,whereas the leachability of phenanthrene correlates well with the concentration of dissolved organic carbon in the effluent,but showing essentially no correlation with the concentration of mineral particles.The surprisingly different trends of the leachability observed between BDE-209 and phenanthrene is counterintuitive,as PBDEs and PAHs often co-exist at e-waste recycling sites(particularly at the sites wherein incineration is being practiced)and share many similarities in terms of physicochemical properties.One possible explanation is that due to its extremely low solubility,BDE-209 predominantly exists in free-phase(i.e.,as solid(nano)particles),whereas the more soluble phenanthrene is mainly sorbed to soil organic matter.Findings in this study underscore the need to better understand the mobility of highly hydrophobic organic contaminants at contaminated sites for improved risk management.展开更多
Lake Baiyangdian is one of China’s largest macrophyte-derived lakes,facing severe challenges related to water quality maintenance and eutrophication prevention.Dissolved organic matter(DOM)was a huge carbon pool and ...Lake Baiyangdian is one of China’s largest macrophyte-derived lakes,facing severe challenges related to water quality maintenance and eutrophication prevention.Dissolved organic matter(DOM)was a huge carbon pool and its abundance,property,and transformation played important roles in the biogeochemical cycle and energy flow in lake ecosystems.In this study,Lake Baiyangdian was divided into four distinct areas:Unartificial Area(UA),Village Area(VA),Tourism Area(TA),and Breeding Area(BA).We examined the diversity of DOM properties and sources across these functional areas.Our findings reveal that DOM in this lake is predominantly composed of protein-like substances,as determined by excitation-emission matrix and parallel factor analysis(EEM-PARAFAC).Notably,the exogenous tyrosine-like component C1 showed a stronger presence in VA and BA compared to UA and TA.Ultrahigh-resolution mass spectrometry(FT-ICR MS)unveiled a similar DOM molecular composition pattern across different functional areas due to the high relative abundances of lignan compounds,suggesting that macrophytes significantly influence the material structure of DOM.DOM properties exhibited specific associations with water quality indicators in various functional areas,as indicated by the Mantel test.The connections between DOM properties and NO_(3)-N andNH3-Nwere more pronounced in VA and BA than in UA and TA.Our results underscore the viability of using DOM as an indicator for more precise and scientific water quality management.展开更多
The dissolved organic matter(DOM)with high mobility and reactivity plays a crucial role in soil.In this study,the characteristics and phytotoxicity ofDOMreleased fromthe hydrochars prepared from different feedstocks(c...The dissolved organic matter(DOM)with high mobility and reactivity plays a crucial role in soil.In this study,the characteristics and phytotoxicity ofDOMreleased fromthe hydrochars prepared from different feedstocks(cowmanure,corn stalk and Myriophyllum aquaticum)under three hydrothermal carbonization(HTC)temperatures(180,200 and 220°C)were evaluated.The results showed that the hydrochars had high dissolved organic carbon content(20.15 to 37.65 mg/g)and its content showed a gradual reduction as HTC temperature increased.Three fluorescent components including mixed substance of fulvic acid-like and humic acid-like substances(C1,30.92%-58.32%),UVA humic acid-like substance(C2,25.27%-29.94%)and protein-like substance(C3,11.74%-41.92%)were identified in hydrochar DOM by excitation emission matrix spectra coupled with parallel factor analysis.High HTC temperature increased the relative proportion of aromatic substances(C1+C2)and humification degree of hydrochar DOM from cow manure,while it presented adverse effects on the hydrochar DOM from corn stalk and Myriophyllum.aquaticum.The principal component analysis suggested that feedstock type and HTC temperature posed significant effects on the characteristics of hydrochar DOM.Additionally,seed germination test of all hydrochar DOM demonstrated that the root length was reduced by 8.88%-26.43%in contrast with control,and the germination index values were 73.57%-91.12%.These findings provided new insights into the potential environmental effects for hydrochar application in soil.展开更多
Arsenic-contaminated groundwater is widely used in agriculture.To meet the increasing demand for safe water in agriculture,an efficient and cost-effective method for As removal from groundwater is urgently needed.We h...Arsenic-contaminated groundwater is widely used in agriculture.To meet the increasing demand for safe water in agriculture,an efficient and cost-effective method for As removal from groundwater is urgently needed.We hypothesized that Fe(oxyhydr)oxide(FeOOH)minerals precipitated in situ from indigenous Fe in groundwater may immobilize As,providing a solution for safely using As-contaminated groundwater in irrigation.To confirm this hypothesis and identify the controlling mechanisms,we comprehensively evaluated the transport,speciation changes,and immobilization of As and Fe in agricultural canals irrigated using As-contaminated groundwater.The efficiently removed As and Fe in the canals accumulated in shallow sediment rather than subsurface sediment.Linear combination fitting(LCF)analysis of X-ray absorption near edge spectroscopy(XANES)indicated that As(Ⅴ)was the dominant As species,followed by As(Ⅲ),and therewas no FeAsO_(4) precipitate.Sequential extraction revealed higher contents of amorphous FeOOH and associated As in shallower sediment than in the subsurface layer.Stoichiometric molar ratio calculations,SEM-EDS,FTIR,and fluorescence spectroscopy collectively demonstrated that the microbial reductive dissolution of amorphous FeOOH proceeded via reactive dissolved organic matter(DOM)consumption in subsurface anoxic porewater environment facilitating high labile As,whereas in surface sediment,the in situ-generated amorphous FeOOH was stable and strongly inhibited As release via adsorption.In summary,groundwater Fe^(2+)can efficiently precipitate in benthic surface sediment as abundant amorphous FeOOH,which immobilizes most of the dissolved As,protecting agricultural soil from contamination.This field research supports the critical roles of the phase and reactivity of in situ-generated FeOOH in As immobilization and provides new insight into the sustainable use of contaminated water.展开更多
The copper complexing of dissolved organic matter released from hydrochar(HDOM)affects the former’s environmental behavior.In this study,how hydrothermal temperatures(180,220 and 260℃)influence the molecular-level c...The copper complexing of dissolved organic matter released from hydrochar(HDOM)affects the former’s environmental behavior.In this study,how hydrothermal temperatures(180,220 and 260℃)influence the molecular-level constitutions and Cu(II)binding features of HDOM were elucidated via fourier transform ion cyclotron resonance mass spectrometry and multi-spectroscopic analysis.The findings demonstrated that the almost HDOM molecules had the traits of lower polarity and higher hydrophobicity.As the hydrothermal temperature increased,the molecules with particularly high relative strength gradually disappeared,average molecular weight,percentages of CHON and aliphatic compounds of HDOM reduced while the percentages of CHO and aromatic compounds increased.In general,the fluorescence quenching of Cu(II)weakened as hydrothermal temperature rose and the Cu(II)binding stability constants of fluorophores in HDOM were 4.50–5.31.In addition,the Cu(II) binding order of fluorophores in HDOM showed temperature heterogeneities, andpolysaccharides or aromatic rings of non-fluorescent substances had the fastest responsesto Cu(II) binding. Generally, fluorescent components tend to bind Cu(II) at relatively traceconcentrations (0–40 μmol/L), whereas non-fluorescent substances tend to the bind Cu(II)at relatively higher concentrations (50–100 μmol/L). This study contributed to the predictionof the potential environmental behaviors and risks of Cu(II) at the molecular level afterhydrochar application.展开更多
Dissolved black carbon(DBC)plays a crucial role in the migration and bioavailability of iron in water.However,the properties of DBC releasing under diverse pyrolysis conditions and dissolving processes have not been s...Dissolved black carbon(DBC)plays a crucial role in the migration and bioavailability of iron in water.However,the properties of DBC releasing under diverse pyrolysis conditions and dissolving processes have not been systematically studied.Here,the compositions of DBC released from biochar through redox processes dominated by bacteria and light were thoroughly studied.It was found that the DBC released from straw biochar possess more oxygen-containing functional groups and aromatic substances.The content of phenolic and carboxylic groups in DBC was increased under influence of microorganisms and light,respectively.The concentration of phenolic hydroxyl groups increased from 10.0~57.5 mmol/gC to 6.6~65.2 mmol/gC,and the concentration of carboxyl groups increased from49.7~97.5 mmol/gC to 62.1~113.3 mmol/gC.Then the impacts of DBC on pyrite dissolution andmicroalgae growth were also investigated.The complexing Fe^(3+)was proved to play a predominant role in the dissolution of ferrous mineral in DBC solution.Due to complexing between iron ion and DBC,the amount of dissolved Fe in aquatic water may rise as a result of elevated number of aromatic components with oxygen containing groups and low molecular weight generated under light conditions.Fe-DBC complexations in solution significantly promoted microalga growth,which might be attributed to the stimulating effect of dissolved Fe on the chlorophyll synthesis.The results of study will deepen our understanding of the behavior and ultimate destiny of DBC released into an iron-rich environment under redox conditions.展开更多
As a widely used fertilizer,urea significantly promotes the leaching of dissolved organic nitrogen(DON)in soils and aggravates nitrogen contamination in groundwater.Clayminerals are considered the most important facto...As a widely used fertilizer,urea significantly promotes the leaching of dissolved organic nitrogen(DON)in soils and aggravates nitrogen contamination in groundwater.Clayminerals are considered the most important factor in retaining DON.However,the effect of urea on the retention of DON with different molecular weights by clay minerals is unknown.In this study,the retention of both low-molecular weight DON(LMWD)and high-molecular weight DON(HMWD)by clay minerals in the presence of urea was investigated.For this purpose,batch adsorption and soil column leaching experiments,characterization analysis(Fourier transform infrared spectroscopy X-ray diffraction,and X-ray photoelectron spectroscopy),and molecular dynamics simulations were carried out.Urea had a positive effect on the adsorption of LMWD,whereas a competitive effect existed for the adsorption of HMWD.The dominant interactions among DON,urea,and clay minerals included H-bonding,ligand exchange,and cation exchange.The urea was preferentially adsorbed on clay minerals and formed a complex,which provided more adsorption sites to LMWD and only a few to HMWD.The presence of urea increased the retention of LMWD and decreased the retention of HMWD in clay minerals.The retention capacity of LMWD increased by 6.9%–12.8%,while that of HMWD decreased by 6.7%–53.1%.These findings suggest that LMWD tended to be trapped in soils,while HMWD was prone to be leached into groundwater,which can be used to evaluate the leaching of DON from soil to groundwater.展开更多
Oceanic dissolved oxygen(DO)concentration is crucial for assessing the status of marine ecosystems.Against the backdrop of global warming,DO shows a general decrease,posing a threat to the health of marine ecosystems....Oceanic dissolved oxygen(DO)concentration is crucial for assessing the status of marine ecosystems.Against the backdrop of global warming,DO shows a general decrease,posing a threat to the health of marine ecosystems.Therefore,there is an urgent need to develop advanced tools to characterize the spatio-temporal variations of three-dimensional(3D)DO.To address this challenge,this study introduces the Light Gradient Boosting Machine(Light-GBM),combining satellite remote sensing and reanalysis data with Biogeochemical Argo data to accurately reconstruct the 3D DO structure in the Mediterranean Sea from 2010 to 2022.Various environmental parameters are incorporated as inputs,including spatiotemporal features,meteorological characteristics,and ocean color properties.The LightGBM model demonstrates excellent performance on the testing dataset with R^(2) of 0.958.The modeled DO agrees better with in-situ measurements than products from numerical models.Using the Shapley Additive exPlanations method,the contributions of input features are assessed.Sea surface temperatures provide a correlation with DO at the sea surface,while spatial coordinates supplement the view of the ocean interior.Based on the reconstructed 3D DO structure,we identify an oxygen minimum zone in the western Mediterranean that expands continuously,reaching depths of approximately 300–800 m.The western Mediterranean exhibits a significant declining trend.This study enhances marine environmental evidence by proposing a precise and cost-effective approach for reconstructing 3D DO,thereby offering insights into the dynamics of DO variations under changing climatic conditions.展开更多
Biochar-derived dissolved organic matter(BCDOM),an essential component of biochar,plays a vital role in regulating the physicochemical and biological properties of soils during biochar application.However,the influenc...Biochar-derived dissolved organic matter(BCDOM),an essential component of biochar,plays a vital role in regulating the physicochemical and biological properties of soils during biochar application.However,the influence of BCDOM on soil organisms has not been clearly explained.Hence,this review aims to discuss the factors affecting BCDOM and its interaction with soil substances including organic pollutants,heavy metals,and microorganisms.Results displayed that the quantity of BCDOM ranges from 0.17 to 37.03 mg/g,which was influenced by feedstock,preparation methods of biochar,and extraction methods.With the decrease in lignin content of feedstocks,carbonization temperature,and acidity of extraction solution,the content of BCDOM increased.Through complexation and adsorption,protein-like components in BCDOM interact with heavy metals,promoting the adsorption and immobilization of heavy metals onto biochar.Furthermore,BCDOM enhances the adsorption of organic pollutants by biochar throughπ−πinteractions,hydrogen bonding,and redox processes.More importantly,BCDOM promotes plant growth by enhancing microbial activities,providing nutrients,and improving soil properties.However,the transport and fate of BCDOM in soil have not been well studied,and more researches are needed to explore the interaction mechanisms between BCDOM and soil organisms.展开更多
Temperate glaciers are highly sensitive to variations in climate and environmental conditions.Investigating the chemical composition of dissolved organic matter(DOM)in glacier snow is essential for understanding its c...Temperate glaciers are highly sensitive to variations in climate and environmental conditions.Investigating the chemical composition of dissolved organic matter(DOM)in glacier snow is essential for understanding its characteristics,sources,and transformation processes within glacial systems.This study aims to elucidate the chemical composition and transformation of DOM in snow environment by analyzing samples collected from snowpits,surface snow,and snow meltwater at Baishui Glacier No.1 on Mt.Yulong during May and June.The average concentrations of dissolved organic carbon(DOC)in snow meltwater collected in May(1.63±0.63 mg L^(-1))and June(1.54±0.35 mg L^(-1))were both significantly higher than those measured in snowpit samples from May(0.74±0.10 mg L^(-1))and June(0.54±0.10 mg L^(-1)),as well as in surface snow samples from May(0.65±0.31 mg L^(-1))and June(0.69±0.30 mg L^(-1)).However,the concentrations of DOC in samples from the same category did not show significant variation between May and June.Using excitation-emission matrix(EEM)fluorescence spectroscopy coupled with parallel factor(PARAFAC)analysis,three protein-like components(C_(1),C_(2),and C_(3))and one humic-like component(C_(4))were identified.The protein-like components accounted for more than 75%of the total DOM in all snow samples,indicating that the fluorescent DOM originated from biological or microbial sources.Significant differences in the relative proportions of the four fluorescent components were observed between snowpit samples from May and June,whereas no significant variations were noted in the other sample types.Furthermore,a clear transformation from protein-like to humic-like components was observed during the transition from snowpits to snow meltwater.Further analysis using Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS)revealed that DOM in these snow samples was predominantly composed of aliphatic and peptide-like compounds(30.9%-50.9%),suggesting a substantial microbial contribution.FT-ICR MS data also demonstrated compositional shifts in DOM among snowpit,surface snow,and meltwater samples.Specifically,aliphatic and peptide-like compounds were progressively transformed into unsaturated compounds with high oxygen content,polyphenolic species,and condensed aromatic compounds during their transition from snowpit to meltwater.Therefore,the relative contribution of terrestrial-derived DOM increased during the transition from snowpit to snowmelt.Furthermore,an increase in heteroatom content in the DOM of meltwater samples indicated continuous chemical transformations likely driven by biological activity and/or photochemical processes during snowmelt and leaching.展开更多
Dissolved organic matter(DOM)is very important in aquatic environments,yet it is challenging to characterize DOM as a highly complex mixture of thousands of molecules,and the knowledge of the effects of different degr...Dissolved organic matter(DOM)is very important in aquatic environments,yet it is challenging to characterize DOM as a highly complex mixture of thousands of molecules,and the knowledge of the effects of different degradation processes on different molecules remains limited.This study examined the distribution and degradation of DOM in a large subtropical river using optical techniques and Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS).At the molecular level,DOM was mainly composed of CHO and lignin-like compounds,which was related to the dominance of forestland in the watershed and resulted in a low biological lability index(MLBL).The modified aromaticity index(AI_(mod)),unsaturation degree(DBE),and humic content(HIX)decreased while MLBL,H/C,absorption spectral slope(S_(275–295)),and biological index(BIX)increased in the estuarine zone due to the increasing autochthonous contribution.Photo-and microbial degradation resulted in a similar decrease in the bulk dissolved organic carbon,while they showed opposite effects on the DOM composition.Photo-degradation removed all fluorescent components and decreased molecular weight,HIX,AI_(mod),DBE,%CHO,%lignin-like,%tannin-like,and%condensed aromatic-like compounds.In contrast,bio-degradation preferentially consumed lipid-like,protein-like,and carbohydrate-like compounds,with increases in%ligninlike,%tannin-like,%condensed aromatic-like compounds,and humic-like fluorescent components.Overall,the application of ultra-high resolutionmass spectrometry provided valuable insights into the composition and behavior of DOM at themolecular level and revealed the contrasting effects of photo-and microbial degradation on different compounds.These results have implications for better understanding the composition and transformation of aquatic DOM.展开更多
Water-soluble organic matter(WSOM)significantly influences the transport of metals and organic contaminants in soils,yet the interaction specifics with antimony(Sb)remain largely unexplored.Antimony is of particular e...Water-soluble organic matter(WSOM)significantly influences the transport of metals and organic contaminants in soils,yet the interaction specifics with antimony(Sb)remain largely unexplored.Antimony is of particular environmental concern due to its toxic properties and harmful effects on ecosystems and human health.Employing a three-step fractionation method with polyvinylpyrrolidone(PVP),this study aimed to isolate and analyze humic acids(HA),PVP-non adsorbed fulvic acids(FAA),and PVP-adsorbed fulvic acids(FAB)from WSOM in soil spiked with Sb and incubated for 18 months.These fractions underwent chemical analysis for carbon(C),nitrogen(N),total organic carbon(TOC),and Sb,complemented by FTIR and 1H NMR spectroscopic characterization.The study revealed that HA wasmore aliphatic,with Sb predominantly associating with the fulvic acid(FA)fraction,accounting for 97%of Sb in extracts.Specifically,the FAA subfraction held substantial portions of total carbon(TC),total nitrogen(TN),total organic carbon(TOC),and Sb.Correlations between Sb concentrations and TN,TC,and TOC were significant.Extraction methods showed NaOH and Na_(4)P_(2)O_(7) outperformed HCl and deionised water in extracting TC,TN,and TOC,with higher Sb concentrations found in Na_(4)P_(2)O_(7) and NaOH extracts.This underscores the role of Fe/Al-SOM complexes in Sb soil availability.The results revealed that FAA subfraction accounted for 76%,64%and 94%of TN,TOC and Sb,respectively.Therefore,this research highlights the FAA fraction’s central role,predominantly comprising non-humic substances like amines,in the availability of C,N,and Sb in Sb-impacted soils.The findings offer insights for environmental management and remediation strategies.展开更多
Spring dinoflagellate blooms are always severe in the Three Gorges Reservoir(TGR),China,threatening water ecological health.Many dinoflagellates are capable of mixotrophism,yet the influence of dissolved organic matte...Spring dinoflagellate blooms are always severe in the Three Gorges Reservoir(TGR),China,threatening water ecological health.Many dinoflagellates are capable of mixotrophism,yet the influence of dissolved organic matter(DOM)on their growth and blooms in spring remains unclear.This study characterized the source and composition of DOM from sediment,soil,and plant,and assessed their effects on the growth of bloom-forming algal species(Peridiniopsis sp.and Microcystis aeruginosa)under different temperatures.The results showed that sediment and soil DOM promoted Peridiniopsis sp.growth,plant DOM slightly inhibited it.However,DOM had no significant effect on M.aeruginosa growth.The promotion of sediment and soil DOM on Peridiniopsis sp.growth was higher at 15℃and 20℃ than at 25℃.Moreover,the effect of DOM on Peridiniopsis sp.growth was more significant than that of high nitrogen and phosphorus.Fulvic acid-like,humic-like and tyrosine-like substances of DOM in sediment and soil might be the effective components promoting the Peridiniopsis sp.growth,while tryptophan-like substance of plant DOM might hinder it.Sediment and soil DOM might promote the Peridiniopsis sp.growth mainly by providing adequate organic carbon,increasing protein content,and improving photosynthesis.The findings will provide important information for the formation and control of dinoflagellate blooms in TGR.展开更多
This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessme...This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessment Report,including CCP scenarios,projecting a significant temperature rise of 3.3–5.7℃in the case o very high GHG emission power,the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa.Through a one-dimensional model incorporat ing sediment redox reactions,various scenarios where ai temperature and wind speed are changed are simulated.I is revealed that a 5℃increase in air temperature leads to decreasing 1-2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer,while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen lev els.Moreover,doubling wind speed enhances surface laye oxygen but diminishes it in deeper layers due to increased mixing.Seasonal variations in wind effects are noted with significant surface layer oxygen increases from 0.4to 0.8 mg/L during summer to autumn,increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertica mixing.This phenomenon impacts the lake’s oxygen cycle year-round.In contrast,precipitation changes show limited impact on oxygen levels,suggesting minor influence com pared to other meteorological factors.The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors fo accurate predictions of future water conditions.A holistic approach integrating nutrient levels,water temperature,and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources,particularly in addressing precipitation variations.展开更多
This study investigates the spatial distribution and regulatory mechanisms of dissolved inorganic carbon(DIC) in Xiangshan Bay, East China Sea, addressing critical gaps in carbon cycling research within semi-enclosed ...This study investigates the spatial distribution and regulatory mechanisms of dissolved inorganic carbon(DIC) in Xiangshan Bay, East China Sea, addressing critical gaps in carbon cycling research within semi-enclosed bays. Through isotopic analysis(δ~(13)C_(DIC), δD and δ18O) and hydrochemical measurements [salinity and dissolved oxygen(DO)] of surface and bottom seawater samples from 52 stations, we demonstrate that δ~(13)C_(DIC) values(surface:-3.6‰ to-2.1‰;bottom:-3.6‰ to-1.8‰) exhibit distinct vertical and spatial patterns, with higher values in surface waters and outer bay regions compared to bottom and inner bay areas. Conservative mixing between seawater(average contribution:56%) and freshwater dominates DIC dynamics, while tidal hydrodynamics amplify the imprint of riverine inputs during low tides. Nutrient gradients driven by saline-freshwater mixing enhance primary productivity in outer bay regions,resulting in 13C-enriched DIC and elevated dissolved organic carbon(DOC) concentrations. Conversely, bottom waters show 13C-depleted signatures(-2.75‰ mean δ~(13)C_(DIC)), reflecting organic matter degradation under oxygen-depleted conditions. Aquaculture activities exacerbate localized eutrophication, with monsoon-enhanced runoff amplifying anthropogenic impacts. This work underscores the sensitivity of coastal carbon cycling to both natural hydrodynamics and anthropogenic perturbations in semi-enclosed bays.展开更多
Alpine tundra ecosystems are highly sensitive to climate change,particularly due to their dependence on the duration and timing of snow cover.This study investigated the effects of the climate extreme years 2022 and 2...Alpine tundra ecosystems are highly sensitive to climate change,particularly due to their dependence on the duration and timing of snow cover.This study investigated the effects of the climate extreme years 2022 and 2023 on carbon(C)and nitrogen(N)forms in two alpine tundra communities:snowbed(SB)and Carex curvula(CC),located at high elevation in the North-West(NW)Italian Alps.During these years,both sites experienced exceptionally low snow cover duration and elevated mean soil temperature during the snow-free season.Dissolved organic carbon(DOC)concentrations significantly increased by+65%in SB and+42%in CC compared to 2016-2021,likely reflecting enhanced microbial decomposition of organic matter.In contrast,soil ammonium and nitrate levels showed no significant changes,indicating differential responses between C and N processes.These findings suggest that DOC is a sensitive(early)indicator of climate-induced shifts in soil functioning.Given the critical role of alpine tundra in global C cycling,understanding DOC dynamics under climate extreme events is crucial to predict future ecosystem feedback to global change.展开更多
Ultraviolet-visible(UV-Vis)and three-dimensional excitation emission matrix fluorescence(3D-EEM)spectroscopies were conducted to investigate the structure and origin of dissolved organic matter(DOM)from soils around t...Ultraviolet-visible(UV-Vis)and three-dimensional excitation emission matrix fluorescence(3D-EEM)spectroscopies were conducted to investigate the structure and origin of dissolved organic matter(DOM)from soils around the Tuo river in Suzhou city in different season.The results showed that the characteristics of all samples,UV-Visible spectra were similar and the relative concentrations of DOM showed an overall increasing trend in the middle and upper reaches of the Tuo River and reached a maximum in the middle reaches of the river.In particular,the aromaticity(A250/A365)of DOM in sediments at the midstream point of the Tuo River and the degree of humification degree(SUVA254)were higher than those in other river sections.The 3D-EEM fluorescence spectra showed that fulvic acid-like peaks in the visible region,fulvic acid-like peaks in the UV-visible region,and two humic acid-like peaks were reflected in the dissolved organic matter of the Tuo River sediments.Combining the three-dimensional fluorescence spectrum with the fluorescence index(fluorescence index,FI)and autochthonous index(autoch-thonous index,BIX)of DOM in the sediments of the Tuo River in different seasons,it shows that the exogenous input of DOM in the sediments of each section of the Tuo River is extremely obvious and less bioavailable.The aromaticity of DOM molecules is enhanced after the Tuo River flows through urban areas.The present study can provide a reference for the future management of the water environment of related rivers.展开更多
Winter irrigation is a crucial measure for preventing farmland salinity in arid inland regions.However,given the relatively complex process of salt leaching under the influence of freezing and thawing,present salinity...Winter irrigation is a crucial measure for preventing farmland salinity in arid inland regions.However,given the relatively complex process of salt leaching under the influence of freezing and thawing,present salinity management has led to soil quality deterioration in the irrigation areas in Northwest China.To better understand this process,a field experiment was conducted in Huangyang Town,Wuwei City,Gansu Province,China to simulate the evolution of soil profile salinity and alkalinity in a typical oasis farmland under 3-year regular barley planting,using a local prevailing water-salt management mode of drip irrigation for the growing period and winter irrigation for the fallow period.This study investigated the impact of freezing on salt leaching by comparing the soil profile water,heat,and salt movements under different winter irrigation quotas.Compared to no winter irrigation,a reduction in the winter irrigation quota from the standard one to a halved one led to a transition from a sink of 11.05% by salt leaching to a source of 13.75% by salt addition.This means that overwintering soil freezing,especially in oases with deep groundwater tables,can worsen root zone salinization caused by a deficit winter irrigation,through freezing-induced root zone soil water and salt return.Furthermore,dry saline soil dominated by sulfate is at the risk of soil alkalization when freezing-induced oversaturation of solute concentration leads to significant salt precipitation.These findings are crucial for understanding the mechanisms behind the increasing secondary salinization caused by unsustainable winter irrigation in oasis irrigation areas.展开更多
To investigate the influence of oxygen content in a physiological liquid environment on the corrosion behavior of biomedical zinc-based alloys,a simulated bodily fluid environment with varying dissolved oxygen was est...To investigate the influence of oxygen content in a physiological liquid environment on the corrosion behavior of biomedical zinc-based alloys,a simulated bodily fluid environment with varying dissolved oxygen was established in vitro using external oxygen supply equipment.The influence of dissolved oxygen concentration on the corrosion behavior of pure Zn and Zn−Cu alloys was studied with scanning electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectrometry,and electrochemical analysis.Due to oxygen absorption corrosion,the increase in dissolved oxygen concentration increases the pH value of the solution and promotes the accumulation of corrosion product layer.Compared with the environment without additional oxygen supply,the corrosion rate of the sample under the continuous oxygen supply condition is increased by one order of magnitude.Because the Zn−Cu alloy has micro-galvanic corrosion,its corrosion rate is about 1.5 times that of pure zinc under different dissolved oxygen conditions.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42307524,and 51879103).
文摘China’s lakes are plagued by cadmium(Cd)pollution.Dissolved organic matter(DOM)significantly regulates Cd(II)transport properties at the sediment-water interface.Understanding the effects of different DOM components on the transportation properties of Cd(II)at the sediment-water interface is essential.In this study,typical DOM from different sources was selected to study Cd(II)mobility at the sediment-water interface.Results showed that terrestrial-derived DOM(fulvic acids,FA)and autochthonous-derived DOM(α-amylase,B1)inhibit Cd(II)sequestration by sediments(42.5%and 5.8%,respectively),while anthropogenic-derived DOM(sodium dodecyl benzene sulfonate,SDBS)increased the Cd(II)adsorption capacity by sediments by 2.8%.Fluorescence quenching coupling with parallel factor analysis(EEM-PARAFAC)was used to characterize different DOM components.The results showed that FA contains three kinds of components(C1,C3:protein-like components,C2:humic-like components);SDBS contains two kinds of components(C1,C2:protein-like components);B1 contains three kinds of components(C1,C2:protein-like components,C3:humic-like components).Three complex reaction modelswere used to characterize the ability of Cd(II)complex with DOM,and it was found that the humic-like component could hardly be complex with Cd(II).Accordingly,humic-like components compete for Cd(II)adsorption sites on the sediment surface and inhibit Cd(II)adsorption fromsediments.Fourier transform infrared spectroscopy(FTIR)of the sediment surface before and after Cd(II)addition was analyzed and proved the competitive adsorption theory.This study provides a better understanding of the Cd(II)mobilization behavior at the sediment-water interface and indicates that the input of humic-like DOM will increase the bioavailability of Cd.
基金supported by the National Key Research and Development Program of China(No.2019YFC1804202)the National Natural Science Foundation of China(Nos.22020102004 and 22125603)+1 种基金Tianjin Municipal Science and Technology Bureau(No.21JCZDJC00280)the Fundamental Research Funds for the Central Universities,and the Ministry of Education of China(No.T2017002).
文摘Polybrominated biphenyl ethers(PBDEs)and polycyclic aromatic hydrocarbons(PAHs)are commonly detected contaminants at e-waste recycling sites.Against the conventional wisdom that PBDEs and PAHs are highly immobile and persist primarily in shallowsurface soils,increasing evidence shows that these compounds can leach into the groundwater.Herein,we compare the leachabilities of PBDEs vs.PAHs from contaminated soils collected at an e-waste recycling site in Tianjin,China.Considerable amounts of BDE-209(0.3–2 ng/L)and phenanthrene(42–106 ng/L),the most abundant PBDE and PAH at the site,are detected in the effluents of columns packed with contaminated soils,with the specific concentrations varying with hydrodynamic and solution chemistry conditions.Interestingly,the leaching potential of BDE-209 appears to be closely related to the release of colloidal mineral particles,whereas the leachability of phenanthrene correlates well with the concentration of dissolved organic carbon in the effluent,but showing essentially no correlation with the concentration of mineral particles.The surprisingly different trends of the leachability observed between BDE-209 and phenanthrene is counterintuitive,as PBDEs and PAHs often co-exist at e-waste recycling sites(particularly at the sites wherein incineration is being practiced)and share many similarities in terms of physicochemical properties.One possible explanation is that due to its extremely low solubility,BDE-209 predominantly exists in free-phase(i.e.,as solid(nano)particles),whereas the more soluble phenanthrene is mainly sorbed to soil organic matter.Findings in this study underscore the need to better understand the mobility of highly hydrophobic organic contaminants at contaminated sites for improved risk management.
基金supported by the National Key Research and Development Program of China(No.2022YFC3204000).
文摘Lake Baiyangdian is one of China’s largest macrophyte-derived lakes,facing severe challenges related to water quality maintenance and eutrophication prevention.Dissolved organic matter(DOM)was a huge carbon pool and its abundance,property,and transformation played important roles in the biogeochemical cycle and energy flow in lake ecosystems.In this study,Lake Baiyangdian was divided into four distinct areas:Unartificial Area(UA),Village Area(VA),Tourism Area(TA),and Breeding Area(BA).We examined the diversity of DOM properties and sources across these functional areas.Our findings reveal that DOM in this lake is predominantly composed of protein-like substances,as determined by excitation-emission matrix and parallel factor analysis(EEM-PARAFAC).Notably,the exogenous tyrosine-like component C1 showed a stronger presence in VA and BA compared to UA and TA.Ultrahigh-resolution mass spectrometry(FT-ICR MS)unveiled a similar DOM molecular composition pattern across different functional areas due to the high relative abundances of lignan compounds,suggesting that macrophytes significantly influence the material structure of DOM.DOM properties exhibited specific associations with water quality indicators in various functional areas,as indicated by the Mantel test.The connections between DOM properties and NO_(3)-N andNH3-Nwere more pronounced in VA and BA than in UA and TA.Our results underscore the viability of using DOM as an indicator for more precise and scientific water quality management.
基金supported by the Director Fund Project provided by the Institute of Plant Nutrition,Resources and Environment,Beijing Academy of Agriculture and Forestry Sciences(No.YZS202101)the Youth Fund Project provided by Beijing Academy of Agriculture and Forestry Sciences(No.QNJJ202125)China Agriculture Research System of MOF and MARA.
文摘The dissolved organic matter(DOM)with high mobility and reactivity plays a crucial role in soil.In this study,the characteristics and phytotoxicity ofDOMreleased fromthe hydrochars prepared from different feedstocks(cowmanure,corn stalk and Myriophyllum aquaticum)under three hydrothermal carbonization(HTC)temperatures(180,200 and 220°C)were evaluated.The results showed that the hydrochars had high dissolved organic carbon content(20.15 to 37.65 mg/g)and its content showed a gradual reduction as HTC temperature increased.Three fluorescent components including mixed substance of fulvic acid-like and humic acid-like substances(C1,30.92%-58.32%),UVA humic acid-like substance(C2,25.27%-29.94%)and protein-like substance(C3,11.74%-41.92%)were identified in hydrochar DOM by excitation emission matrix spectra coupled with parallel factor analysis.High HTC temperature increased the relative proportion of aromatic substances(C1+C2)and humification degree of hydrochar DOM from cow manure,while it presented adverse effects on the hydrochar DOM from corn stalk and Myriophyllum.aquaticum.The principal component analysis suggested that feedstock type and HTC temperature posed significant effects on the characteristics of hydrochar DOM.Additionally,seed germination test of all hydrochar DOM demonstrated that the root length was reduced by 8.88%-26.43%in contrast with control,and the germination index values were 73.57%-91.12%.These findings provided new insights into the potential environmental effects for hydrochar application in soil.
基金supported by the National Natural Science Foundation of China(Nos.41830753,42277201,42377242,and 41977286)the Scientific Research Foundation of Guangzhou University(No.YJ2023027)the College Student Innovation and Entrepreneurship Training Program(No.S202311078057).
文摘Arsenic-contaminated groundwater is widely used in agriculture.To meet the increasing demand for safe water in agriculture,an efficient and cost-effective method for As removal from groundwater is urgently needed.We hypothesized that Fe(oxyhydr)oxide(FeOOH)minerals precipitated in situ from indigenous Fe in groundwater may immobilize As,providing a solution for safely using As-contaminated groundwater in irrigation.To confirm this hypothesis and identify the controlling mechanisms,we comprehensively evaluated the transport,speciation changes,and immobilization of As and Fe in agricultural canals irrigated using As-contaminated groundwater.The efficiently removed As and Fe in the canals accumulated in shallow sediment rather than subsurface sediment.Linear combination fitting(LCF)analysis of X-ray absorption near edge spectroscopy(XANES)indicated that As(Ⅴ)was the dominant As species,followed by As(Ⅲ),and therewas no FeAsO_(4) precipitate.Sequential extraction revealed higher contents of amorphous FeOOH and associated As in shallower sediment than in the subsurface layer.Stoichiometric molar ratio calculations,SEM-EDS,FTIR,and fluorescence spectroscopy collectively demonstrated that the microbial reductive dissolution of amorphous FeOOH proceeded via reactive dissolved organic matter(DOM)consumption in subsurface anoxic porewater environment facilitating high labile As,whereas in surface sediment,the in situ-generated amorphous FeOOH was stable and strongly inhibited As release via adsorption.In summary,groundwater Fe^(2+)can efficiently precipitate in benthic surface sediment as abundant amorphous FeOOH,which immobilizes most of the dissolved As,protecting agricultural soil from contamination.This field research supports the critical roles of the phase and reactivity of in situ-generated FeOOH in As immobilization and provides new insight into the sustainable use of contaminated water.
基金supported by the National Natural Science Foundation of China(No.42307090)the Open Subject from State Environmental Protection Key Laboratory of Aquatic Ecosystem Health in theMiddle and Lower Reaches of Yangtze River(No.AEHKF2023008).
文摘The copper complexing of dissolved organic matter released from hydrochar(HDOM)affects the former’s environmental behavior.In this study,how hydrothermal temperatures(180,220 and 260℃)influence the molecular-level constitutions and Cu(II)binding features of HDOM were elucidated via fourier transform ion cyclotron resonance mass spectrometry and multi-spectroscopic analysis.The findings demonstrated that the almost HDOM molecules had the traits of lower polarity and higher hydrophobicity.As the hydrothermal temperature increased,the molecules with particularly high relative strength gradually disappeared,average molecular weight,percentages of CHON and aliphatic compounds of HDOM reduced while the percentages of CHO and aromatic compounds increased.In general,the fluorescence quenching of Cu(II)weakened as hydrothermal temperature rose and the Cu(II)binding stability constants of fluorophores in HDOM were 4.50–5.31.In addition,the Cu(II) binding order of fluorophores in HDOM showed temperature heterogeneities, andpolysaccharides or aromatic rings of non-fluorescent substances had the fastest responsesto Cu(II) binding. Generally, fluorescent components tend to bind Cu(II) at relatively traceconcentrations (0–40 μmol/L), whereas non-fluorescent substances tend to the bind Cu(II)at relatively higher concentrations (50–100 μmol/L). This study contributed to the predictionof the potential environmental behaviors and risks of Cu(II) at the molecular level afterhydrochar application.
基金supported by the National Natural Science Foundation of China(Nos.42207450,42067056,and 21866017)the Yunnan Fundamental Research Projects(No.202101BE070001-013)the Foundation for Distinguished Young Talents of Yunnan Province(No.202101AV070006).
文摘Dissolved black carbon(DBC)plays a crucial role in the migration and bioavailability of iron in water.However,the properties of DBC releasing under diverse pyrolysis conditions and dissolving processes have not been systematically studied.Here,the compositions of DBC released from biochar through redox processes dominated by bacteria and light were thoroughly studied.It was found that the DBC released from straw biochar possess more oxygen-containing functional groups and aromatic substances.The content of phenolic and carboxylic groups in DBC was increased under influence of microorganisms and light,respectively.The concentration of phenolic hydroxyl groups increased from 10.0~57.5 mmol/gC to 6.6~65.2 mmol/gC,and the concentration of carboxyl groups increased from49.7~97.5 mmol/gC to 62.1~113.3 mmol/gC.Then the impacts of DBC on pyrite dissolution andmicroalgae growth were also investigated.The complexing Fe^(3+)was proved to play a predominant role in the dissolution of ferrous mineral in DBC solution.Due to complexing between iron ion and DBC,the amount of dissolved Fe in aquatic water may rise as a result of elevated number of aromatic components with oxygen containing groups and low molecular weight generated under light conditions.Fe-DBC complexations in solution significantly promoted microalga growth,which might be attributed to the stimulating effect of dissolved Fe on the chlorophyll synthesis.The results of study will deepen our understanding of the behavior and ultimate destiny of DBC released into an iron-rich environment under redox conditions.
基金supported by the National Natural Science Foundation of China(No.42107052)Beijing Natural Science Foundation(No.JQ21031).
文摘As a widely used fertilizer,urea significantly promotes the leaching of dissolved organic nitrogen(DON)in soils and aggravates nitrogen contamination in groundwater.Clayminerals are considered the most important factor in retaining DON.However,the effect of urea on the retention of DON with different molecular weights by clay minerals is unknown.In this study,the retention of both low-molecular weight DON(LMWD)and high-molecular weight DON(HMWD)by clay minerals in the presence of urea was investigated.For this purpose,batch adsorption and soil column leaching experiments,characterization analysis(Fourier transform infrared spectroscopy X-ray diffraction,and X-ray photoelectron spectroscopy),and molecular dynamics simulations were carried out.Urea had a positive effect on the adsorption of LMWD,whereas a competitive effect existed for the adsorption of HMWD.The dominant interactions among DON,urea,and clay minerals included H-bonding,ligand exchange,and cation exchange.The urea was preferentially adsorbed on clay minerals and formed a complex,which provided more adsorption sites to LMWD and only a few to HMWD.The presence of urea increased the retention of LMWD and decreased the retention of HMWD in clay minerals.The retention capacity of LMWD increased by 6.9%–12.8%,while that of HMWD decreased by 6.7%–53.1%.These findings suggest that LMWD tended to be trapped in soils,while HMWD was prone to be leached into groundwater,which can be used to evaluate the leaching of DON from soil to groundwater.
基金supported by the Central Guiding Local Science and Technology Development Fund of Shandong-Yellow River Basin(No.YDZX2023019)Shandong Natural Science Foundation of China(Nos.ZR2020QF067 and ZR2023QD073)+6 种基金the Discipline Cluster Research Project of Qingdao University“Deep mining and intelligent prediction of multimodal big data for marine ecological disasters”(No.20240604)sourced from the International Argo Program and the national programs that contribute to it(https://argo.ucsd.edu)the CMEMS(http://marine.copernicus.eu/)the CDS(https://cds.climate.copernicus.eu/)the EMODnet(https://www.emodnet-chemistry.eu/)obtained from the ERA5(https://www.ecmwf.int)derived from the Glob Colour Project(http://globcolour.info).
文摘Oceanic dissolved oxygen(DO)concentration is crucial for assessing the status of marine ecosystems.Against the backdrop of global warming,DO shows a general decrease,posing a threat to the health of marine ecosystems.Therefore,there is an urgent need to develop advanced tools to characterize the spatio-temporal variations of three-dimensional(3D)DO.To address this challenge,this study introduces the Light Gradient Boosting Machine(Light-GBM),combining satellite remote sensing and reanalysis data with Biogeochemical Argo data to accurately reconstruct the 3D DO structure in the Mediterranean Sea from 2010 to 2022.Various environmental parameters are incorporated as inputs,including spatiotemporal features,meteorological characteristics,and ocean color properties.The LightGBM model demonstrates excellent performance on the testing dataset with R^(2) of 0.958.The modeled DO agrees better with in-situ measurements than products from numerical models.Using the Shapley Additive exPlanations method,the contributions of input features are assessed.Sea surface temperatures provide a correlation with DO at the sea surface,while spatial coordinates supplement the view of the ocean interior.Based on the reconstructed 3D DO structure,we identify an oxygen minimum zone in the western Mediterranean that expands continuously,reaching depths of approximately 300–800 m.The western Mediterranean exhibits a significant declining trend.This study enhances marine environmental evidence by proposing a precise and cost-effective approach for reconstructing 3D DO,thereby offering insights into the dynamics of DO variations under changing climatic conditions.
基金Project(2020YFC1908802)supported by the National Key Research and Development Project of China。
文摘Biochar-derived dissolved organic matter(BCDOM),an essential component of biochar,plays a vital role in regulating the physicochemical and biological properties of soils during biochar application.However,the influence of BCDOM on soil organisms has not been clearly explained.Hence,this review aims to discuss the factors affecting BCDOM and its interaction with soil substances including organic pollutants,heavy metals,and microorganisms.Results displayed that the quantity of BCDOM ranges from 0.17 to 37.03 mg/g,which was influenced by feedstock,preparation methods of biochar,and extraction methods.With the decrease in lignin content of feedstocks,carbonization temperature,and acidity of extraction solution,the content of BCDOM increased.Through complexation and adsorption,protein-like components in BCDOM interact with heavy metals,promoting the adsorption and immobilization of heavy metals onto biochar.Furthermore,BCDOM enhances the adsorption of organic pollutants by biochar throughπ−πinteractions,hydrogen bonding,and redox processes.More importantly,BCDOM promotes plant growth by enhancing microbial activities,providing nutrients,and improving soil properties.However,the transport and fate of BCDOM in soil have not been well studied,and more researches are needed to explore the interaction mechanisms between BCDOM and soil organisms.
基金supported by grants from the Sichuan Natural Science Foundation Project(2024NSFSC0793)Dagu Glacier Research Institute(Center)project of Aba Normal College(AS-DTPT 2023072)the support of Youth Innovation Promotion Association CAS(2021429)。
文摘Temperate glaciers are highly sensitive to variations in climate and environmental conditions.Investigating the chemical composition of dissolved organic matter(DOM)in glacier snow is essential for understanding its characteristics,sources,and transformation processes within glacial systems.This study aims to elucidate the chemical composition and transformation of DOM in snow environment by analyzing samples collected from snowpits,surface snow,and snow meltwater at Baishui Glacier No.1 on Mt.Yulong during May and June.The average concentrations of dissolved organic carbon(DOC)in snow meltwater collected in May(1.63±0.63 mg L^(-1))and June(1.54±0.35 mg L^(-1))were both significantly higher than those measured in snowpit samples from May(0.74±0.10 mg L^(-1))and June(0.54±0.10 mg L^(-1)),as well as in surface snow samples from May(0.65±0.31 mg L^(-1))and June(0.69±0.30 mg L^(-1)).However,the concentrations of DOC in samples from the same category did not show significant variation between May and June.Using excitation-emission matrix(EEM)fluorescence spectroscopy coupled with parallel factor(PARAFAC)analysis,three protein-like components(C_(1),C_(2),and C_(3))and one humic-like component(C_(4))were identified.The protein-like components accounted for more than 75%of the total DOM in all snow samples,indicating that the fluorescent DOM originated from biological or microbial sources.Significant differences in the relative proportions of the four fluorescent components were observed between snowpit samples from May and June,whereas no significant variations were noted in the other sample types.Furthermore,a clear transformation from protein-like to humic-like components was observed during the transition from snowpits to snow meltwater.Further analysis using Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS)revealed that DOM in these snow samples was predominantly composed of aliphatic and peptide-like compounds(30.9%-50.9%),suggesting a substantial microbial contribution.FT-ICR MS data also demonstrated compositional shifts in DOM among snowpit,surface snow,and meltwater samples.Specifically,aliphatic and peptide-like compounds were progressively transformed into unsaturated compounds with high oxygen content,polyphenolic species,and condensed aromatic compounds during their transition from snowpit to meltwater.Therefore,the relative contribution of terrestrial-derived DOM increased during the transition from snowpit to snowmelt.Furthermore,an increase in heteroatom content in the DOM of meltwater samples indicated continuous chemical transformations likely driven by biological activity and/or photochemical processes during snowmelt and leaching.
基金supported by Fujian Provincial Natural Science Foundation of China(Nos.2023J01456 and 2021J01626)the National Natural Science Foundation of China(No.41976042)the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University(Nos.SL2022ZD207 and SL2023MS019).
文摘Dissolved organic matter(DOM)is very important in aquatic environments,yet it is challenging to characterize DOM as a highly complex mixture of thousands of molecules,and the knowledge of the effects of different degradation processes on different molecules remains limited.This study examined the distribution and degradation of DOM in a large subtropical river using optical techniques and Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR-MS).At the molecular level,DOM was mainly composed of CHO and lignin-like compounds,which was related to the dominance of forestland in the watershed and resulted in a low biological lability index(MLBL).The modified aromaticity index(AI_(mod)),unsaturation degree(DBE),and humic content(HIX)decreased while MLBL,H/C,absorption spectral slope(S_(275–295)),and biological index(BIX)increased in the estuarine zone due to the increasing autochthonous contribution.Photo-and microbial degradation resulted in a similar decrease in the bulk dissolved organic carbon,while they showed opposite effects on the DOM composition.Photo-degradation removed all fluorescent components and decreased molecular weight,HIX,AI_(mod),DBE,%CHO,%lignin-like,%tannin-like,and%condensed aromatic-like compounds.In contrast,bio-degradation preferentially consumed lipid-like,protein-like,and carbohydrate-like compounds,with increases in%ligninlike,%tannin-like,%condensed aromatic-like compounds,and humic-like fluorescent components.Overall,the application of ultra-high resolutionmass spectrometry provided valuable insights into the composition and behavior of DOM at themolecular level and revealed the contrasting effects of photo-and microbial degradation on different compounds.These results have implications for better understanding the composition and transformation of aquatic DOM.
基金financial support provided by the University of New England,Australia for conducting this research。
文摘Water-soluble organic matter(WSOM)significantly influences the transport of metals and organic contaminants in soils,yet the interaction specifics with antimony(Sb)remain largely unexplored.Antimony is of particular environmental concern due to its toxic properties and harmful effects on ecosystems and human health.Employing a three-step fractionation method with polyvinylpyrrolidone(PVP),this study aimed to isolate and analyze humic acids(HA),PVP-non adsorbed fulvic acids(FAA),and PVP-adsorbed fulvic acids(FAB)from WSOM in soil spiked with Sb and incubated for 18 months.These fractions underwent chemical analysis for carbon(C),nitrogen(N),total organic carbon(TOC),and Sb,complemented by FTIR and 1H NMR spectroscopic characterization.The study revealed that HA wasmore aliphatic,with Sb predominantly associating with the fulvic acid(FA)fraction,accounting for 97%of Sb in extracts.Specifically,the FAA subfraction held substantial portions of total carbon(TC),total nitrogen(TN),total organic carbon(TOC),and Sb.Correlations between Sb concentrations and TN,TC,and TOC were significant.Extraction methods showed NaOH and Na_(4)P_(2)O_(7) outperformed HCl and deionised water in extracting TC,TN,and TOC,with higher Sb concentrations found in Na_(4)P_(2)O_(7) and NaOH extracts.This underscores the role of Fe/Al-SOM complexes in Sb soil availability.The results revealed that FAA subfraction accounted for 76%,64%and 94%of TN,TOC and Sb,respectively.Therefore,this research highlights the FAA fraction’s central role,predominantly comprising non-humic substances like amines,in the availability of C,N,and Sb in Sb-impacted soils.The findings offer insights for environmental management and remediation strategies.
基金supported by the National Key Research and Development Program(No.2021YFC3201003)。
文摘Spring dinoflagellate blooms are always severe in the Three Gorges Reservoir(TGR),China,threatening water ecological health.Many dinoflagellates are capable of mixotrophism,yet the influence of dissolved organic matter(DOM)on their growth and blooms in spring remains unclear.This study characterized the source and composition of DOM from sediment,soil,and plant,and assessed their effects on the growth of bloom-forming algal species(Peridiniopsis sp.and Microcystis aeruginosa)under different temperatures.The results showed that sediment and soil DOM promoted Peridiniopsis sp.growth,plant DOM slightly inhibited it.However,DOM had no significant effect on M.aeruginosa growth.The promotion of sediment and soil DOM on Peridiniopsis sp.growth was higher at 15℃and 20℃ than at 25℃.Moreover,the effect of DOM on Peridiniopsis sp.growth was more significant than that of high nitrogen and phosphorus.Fulvic acid-like,humic-like and tyrosine-like substances of DOM in sediment and soil might be the effective components promoting the Peridiniopsis sp.growth,while tryptophan-like substance of plant DOM might hinder it.Sediment and soil DOM might promote the Peridiniopsis sp.growth mainly by providing adequate organic carbon,increasing protein content,and improving photosynthesis.The findings will provide important information for the formation and control of dinoflagellate blooms in TGR.
基金Open Access funding provided by Kobe UniversityThis research was partially performed by the Environment Research and Technology Development Fund(2RL-2301)of the Environmental Restoration and Conservation Agency provided by Ministry of the Environment of Japan.
文摘This study examines the potential impacts o climate change on Lake Biwa,Japan’s largest freshwate lake,with a focus on temperature,wind speed,and pre cipitation variations.Leveraging data from the IPCC Sixth Assessment Report,including CCP scenarios,projecting a significant temperature rise of 3.3–5.7℃in the case o very high GHG emission power,the research investigates how these shifts may influence dissolved oxygen levels in Lake Biwa.Through a one-dimensional model incorporat ing sediment redox reactions,various scenarios where ai temperature and wind speed are changed are simulated.I is revealed that a 5℃increase in air temperature leads to decreasing 1-2 mg/L of dissolved oxygen concentrations from the surface layer to the bottom layer,while a decrease in air temperature tends to elevate 1–3 mg/L of oxygen lev els.Moreover,doubling wind speed enhances surface laye oxygen but diminishes it in deeper layers due to increased mixing.Seasonal variations in wind effects are noted with significant surface layer oxygen increases from 0.4to 0.8 mg/L during summer to autumn,increases from 0.4 to 0.8 mg/L in autumn to winter due to intensified vertica mixing.This phenomenon impacts the lake’s oxygen cycle year-round.In contrast,precipitation changes show limited impact on oxygen levels,suggesting minor influence com pared to other meteorological factors.The study suggests the necessity of comprehensive three-dimensional models that account for lake-specific and geographical factors fo accurate predictions of future water conditions.A holistic approach integrating nutrient levels,water temperature,and river inflow is deemed essential for sustainable management of Lake Biwa’s water resources,particularly in addressing precipitation variations.
基金The National Key R&D Program of China under contract No. 2022YFE0209300National Natural Science Foundation of China under contract No. 42176091+1 种基金Asia Cooperation Fund of China (Comparative Study of Geoenvironment and Geohazards in the Yangtze River Delta and the Red River Delta)China Geological Survey Project under contract No. DD20242714。
文摘This study investigates the spatial distribution and regulatory mechanisms of dissolved inorganic carbon(DIC) in Xiangshan Bay, East China Sea, addressing critical gaps in carbon cycling research within semi-enclosed bays. Through isotopic analysis(δ~(13)C_(DIC), δD and δ18O) and hydrochemical measurements [salinity and dissolved oxygen(DO)] of surface and bottom seawater samples from 52 stations, we demonstrate that δ~(13)C_(DIC) values(surface:-3.6‰ to-2.1‰;bottom:-3.6‰ to-1.8‰) exhibit distinct vertical and spatial patterns, with higher values in surface waters and outer bay regions compared to bottom and inner bay areas. Conservative mixing between seawater(average contribution:56%) and freshwater dominates DIC dynamics, while tidal hydrodynamics amplify the imprint of riverine inputs during low tides. Nutrient gradients driven by saline-freshwater mixing enhance primary productivity in outer bay regions,resulting in 13C-enriched DIC and elevated dissolved organic carbon(DOC) concentrations. Conversely, bottom waters show 13C-depleted signatures(-2.75‰ mean δ~(13)C_(DIC)), reflecting organic matter degradation under oxygen-depleted conditions. Aquaculture activities exacerbate localized eutrophication, with monsoon-enhanced runoff amplifying anthropogenic impacts. This work underscores the sensitivity of coastal carbon cycling to both natural hydrodynamics and anthropogenic perturbations in semi-enclosed bays.
基金supported by the National Recovery and Resilience Plan(NRRP),Mission 4 Component 2 Investment 1.4-Call for tender No.3138 of 16 December 2021,rectified by Decree n.3175 of 18 December 2021 of Italian Ministry of University and Research funded by the European Union–Next Generation EUProject code CN_00000033,Concession Decree No.1034 of 17 June 2022 adopted by the Italian Ministry of University and Research,CUP D13C22001350001,Project title“National Biodiversity Future Center NBFC”supported by the project NODES,which has received funding from the MUR-M4C21.5 of PNRR funded by the European Union-Next Generation EU(ECS00000036-CUP[D17G22000150001])。
文摘Alpine tundra ecosystems are highly sensitive to climate change,particularly due to their dependence on the duration and timing of snow cover.This study investigated the effects of the climate extreme years 2022 and 2023 on carbon(C)and nitrogen(N)forms in two alpine tundra communities:snowbed(SB)and Carex curvula(CC),located at high elevation in the North-West(NW)Italian Alps.During these years,both sites experienced exceptionally low snow cover duration and elevated mean soil temperature during the snow-free season.Dissolved organic carbon(DOC)concentrations significantly increased by+65%in SB and+42%in CC compared to 2016-2021,likely reflecting enhanced microbial decomposition of organic matter.In contrast,soil ammonium and nitrate levels showed no significant changes,indicating differential responses between C and N processes.These findings suggest that DOC is a sensitive(early)indicator of climate-induced shifts in soil functioning.Given the critical role of alpine tundra in global C cycling,understanding DOC dynamics under climate extreme events is crucial to predict future ecosystem feedback to global change.
文摘Ultraviolet-visible(UV-Vis)and three-dimensional excitation emission matrix fluorescence(3D-EEM)spectroscopies were conducted to investigate the structure and origin of dissolved organic matter(DOM)from soils around the Tuo river in Suzhou city in different season.The results showed that the characteristics of all samples,UV-Visible spectra were similar and the relative concentrations of DOM showed an overall increasing trend in the middle and upper reaches of the Tuo River and reached a maximum in the middle reaches of the river.In particular,the aromaticity(A250/A365)of DOM in sediments at the midstream point of the Tuo River and the degree of humification degree(SUVA254)were higher than those in other river sections.The 3D-EEM fluorescence spectra showed that fulvic acid-like peaks in the visible region,fulvic acid-like peaks in the UV-visible region,and two humic acid-like peaks were reflected in the dissolved organic matter of the Tuo River sediments.Combining the three-dimensional fluorescence spectrum with the fluorescence index(fluorescence index,FI)and autochthonous index(autoch-thonous index,BIX)of DOM in the sediments of the Tuo River in different seasons,it shows that the exogenous input of DOM in the sediments of each section of the Tuo River is extremely obvious and less bioavailable.The aromaticity of DOM molecules is enhanced after the Tuo River flows through urban areas.The present study can provide a reference for the future management of the water environment of related rivers.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA24040203)the Inner Mongolia Key R&D Program,China(No.NMKJXM202107)+1 种基金the Key R&D Program of Gansu Province of China(No.21CX6QA026)the Natural Science Foundation of Gansu Province of China(No.20JR5RA074)。
文摘Winter irrigation is a crucial measure for preventing farmland salinity in arid inland regions.However,given the relatively complex process of salt leaching under the influence of freezing and thawing,present salinity management has led to soil quality deterioration in the irrigation areas in Northwest China.To better understand this process,a field experiment was conducted in Huangyang Town,Wuwei City,Gansu Province,China to simulate the evolution of soil profile salinity and alkalinity in a typical oasis farmland under 3-year regular barley planting,using a local prevailing water-salt management mode of drip irrigation for the growing period and winter irrigation for the fallow period.This study investigated the impact of freezing on salt leaching by comparing the soil profile water,heat,and salt movements under different winter irrigation quotas.Compared to no winter irrigation,a reduction in the winter irrigation quota from the standard one to a halved one led to a transition from a sink of 11.05% by salt leaching to a source of 13.75% by salt addition.This means that overwintering soil freezing,especially in oases with deep groundwater tables,can worsen root zone salinization caused by a deficit winter irrigation,through freezing-induced root zone soil water and salt return.Furthermore,dry saline soil dominated by sulfate is at the risk of soil alkalization when freezing-induced oversaturation of solute concentration leads to significant salt precipitation.These findings are crucial for understanding the mechanisms behind the increasing secondary salinization caused by unsustainable winter irrigation in oasis irrigation areas.
基金supported by the National Natural Science Foundation of China(Nos.52171236,51971062,52231005)Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,Southeast University,China(No.AMM2024A01)+3 种基金Suzhou Science and Technology Project,China(Nos.SJC2023005,SZS2023023)City University of Hong Kong Donation Research Grant,China(No.DON-RMG 9229021)City University of Hong Kong Strategic Research Grant,China(No.SRG 7005505)City University of Hong Kong Donation Grant,China(No.9220061)。
文摘To investigate the influence of oxygen content in a physiological liquid environment on the corrosion behavior of biomedical zinc-based alloys,a simulated bodily fluid environment with varying dissolved oxygen was established in vitro using external oxygen supply equipment.The influence of dissolved oxygen concentration on the corrosion behavior of pure Zn and Zn−Cu alloys was studied with scanning electron microscopy,energy dispersive spectroscopy,Fourier transform infrared spectrometry,and electrochemical analysis.Due to oxygen absorption corrosion,the increase in dissolved oxygen concentration increases the pH value of the solution and promotes the accumulation of corrosion product layer.Compared with the environment without additional oxygen supply,the corrosion rate of the sample under the continuous oxygen supply condition is increased by one order of magnitude.Because the Zn−Cu alloy has micro-galvanic corrosion,its corrosion rate is about 1.5 times that of pure zinc under different dissolved oxygen conditions.
