Exogenous organic input impacts soil phosphorus transformation.Meanwhile,dissolved organic matter(DOM)is crucial for biogeochemical functions.Nevertheless,the interaction between the structural composition of DOM and ...Exogenous organic input impacts soil phosphorus transformation.Meanwhile,dissolved organic matter(DOM)is crucial for biogeochemical functions.Nevertheless,the interaction between the structural composition of DOM and phosphorus during the soil formation process of phosphogypsum(PG)remains unknown.This study explores the interaction between the structural composition of DOM and phosphorus in enhanced PG under the participation of fungal microorganisms through different application amounts of exogenous organic matter and culture time.Results show that application of exogenous organic matter led to varying degrees of increase in dissolved organic carbon(DOC)concentration and humification extent in the soil-like substrate.Additionally,the relative abundance of protein-like component C3 exhibited a trend of initial increase followed by decline over time.The contents of available phosphorus(AP),microbial biomass phosphorus(MBP),and active phosphorus pools(Active-P)in the soil-like substrate are all enhanced overall.Furthermore,a significant correlation exists between DOC and AP as well as MBP.This suggests that DOM is a crucial factor in enhancing the phosphorus availability of the soil-like substrate.The enrichment of known phosphate-solubilizing fungi in culturing favors the decomposition,activation and utilization of hard-to-mineralize phosphorus components in the soil-like substrate.These findings help understand DOM’s biogeochemical behavior and offer insights into PG utilization and the sustainable development of China’s phosphorus industry.展开更多
The retrieval of dissolved organic carbon （DOC） distribution by remote sensing is mainly based on the em- pirical relationship of DOC concentration and colored dissolved organic matter （CDOM） concentration in many...The retrieval of dissolved organic carbon （DOC） distribution by remote sensing is mainly based on the em- pirical relationship of DOC concentration and colored dissolved organic matter （CDOM） concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world＇s major estuaries and bays. It is found that, generally, the C- DOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a non- conservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea（ECS） was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeo- chemical processes were analyzed except for the physical mixing process with the data from late autumn （November, 2010） and winter （December, 2009） cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological pro- cesses. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm （CSDM） was proposed： when the biological influence was significant （Chl a greater than 0.8 μg/dm3）, DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant （Chl a less than 0.8 μg/dm3）, the direct DOC concentration and CDOM concentration relationship was used. Based on the pro- posed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.展开更多
In this study, the spatial and temporal distribution characteristics of dis- solved organic carbon （DOC） in water-logged paddy soil in Yanbian were investigat- ed under conditions of different fertilization types （...In this study, the spatial and temporal distribution characteristics of dis- solved organic carbon （DOC） in water-logged paddy soil in Yanbian were investigat- ed under conditions of different fertilization types （single application of chemical fer- tilizer, mixed application and chemical and organic fertilizers and single application of organic fertilizer） and cultivation years （80 years and 120 years）. The results showed that the spatial and temporal distribution of DOC in water-logged paddy soil changed significantly with time going by. The single application of chemical fertilizer or mixed application of chemical and organic fertilizers contributed to the release of DOC in top paddy soil under water-logging condition; the single application of organ- ic fertilizer promoted the accumulation of DOC in bottom paddy soil, resulting in great heterogeneity of DOC in the vertical space, but the single application of chem- ical fertilizer weakened the vertical spatial heterogeneity of soil DOC; the DOC con- tent in the 80-year-old water-logged paddy soil was higher and more stable than that in the 120-year-old soil.展开更多
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
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
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
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
Dissolved organic carbon(DOC)constitutes the largest organic carbon reservoir in the ocean and plays a vital role in the oceanic carbon cycle.However,research on DOC in Antarctica has been limited,largely due to diffi...Dissolved organic carbon(DOC)constitutes the largest organic carbon reservoir in the ocean and plays a vital role in the oceanic carbon cycle.However,research on DOC in Antarctica has been limited,largely due to difficulties in sample collection.In this study,we investigate chromophoric dissolved organic matter(CDOM)in the Cosmonaut Sea and Cooperation Sea,Antarctica.The relative abundances of CDOM,as indicated by the absorption coefficient at 254 nm(a_(254)),exhibit significant variability,ranging from 1.29 m^(-1) to 8.37 m^(-1).The diatom species B is the primary contributor to CDOM in the region influenced by the Antarctic slope current.Using excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis(EEM-PARAFAC),we identify three fluorescent components:one protein-like component(C1)and two humic-like components(C2 and C3).Our findings indicate that strong microbial activity in the euphotic zones of the Cosmonaut Sea and Cooperation Sea serves as a primary pathway for the removal of protein-like substances while also acting as a significant source of humic-like substances.Microbial degradation likely accounts for the decoupling of the vertical distribution of DOC and phytoplankton.Furthermore,the intrusion of modified circumpolar deep water(mCDW)into the euphotic zones of open ocean areas influences the distribution of CDOM at depths shallower than 200 m.These results have important implications for enhancing our understanding of the dynamics of CDOM and DOC in east Antarctica,as well as for improving assessments of the carbon cycle.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
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
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 δ^(18)O) 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
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
Dissolved organic matter(DOM)in rivers plays a key role in the global carbon cycle and aquatic ecosystems,yet its spatiotemporal dynamics across complex terrains remains inadequately characterized.To address this gap,...Dissolved organic matter(DOM)in rivers plays a key role in the global carbon cycle and aquatic ecosystems,yet its spatiotemporal dynamics across complex terrains remains inadequately characterized.To address this gap,we conducted seasonal sampling along the Luan River and examined how DOM composition varies over space and time in response to environmental drivers.Using parallel factor analysis(PARAFAC),we identified two humic-like components(C1+C2,Em>380 nm)and one protein-like component(C3,Em<380 nm).DOM fluorescence intensity was lowest in winter,while C1 and C3 levels peaked in autumn and C2 in summer(p<0.05).Spatially,C1 and C3 levels were highest downstream regions,whereas C2 peaked in the midstream section(p<0.05).Microbial sources dominated DOM in spring,winter,and in both headwater and downstream areas(FI>1.9).Principal coordinates analysis(PCoA)combined with multi-response permutation process(MRPP)confirmed significant spatiotemporal differences in DOM composition(p<0.05).Random forest modeling showed humic-like components were more sensitive to environmental changes.Redundancy analysis(RDA)and Mantel tests identified temperature as the dominant seasonal driver of DOM variation(p<0.05),while dissolved total phosphorus(DTP)and nitrate nitrogen(NO_(3)^(-)-N)were the key spatial determinants.Significant correlations were also observed between NO_(3)^(-)-N and ammonium nitrogen(NH_(4)^(+)-N),as well as between DTP and DOM,suggesting shared origins and compositional linkages(p<0.05).Our findings highlight the pronounced seasonal and spatial heterogeneity of DOM in multi-terrain river systems,offering valuable insights into carbon dynamics and ecosystem functioning in river systems.展开更多
Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession...Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors.The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments,and the results showed that the average removal rate of TN was 45.80 g N/(m^(3)·day)when the influent N level was 100 mg N/L,which was better than 10 mg N/L and 50 mg N/L.Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates.Medium to high N levels enriched a copiotroph bacterial module(Module 1)detected by network analysis,including Phenylobacterium,Xanthobacteraceae,Burkholderiaceae,Pseudomonas,and Magnetospirillaceae,carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM.Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophswith fewer N-cycle potentials(Module 2).Together,this study reveals that the compositional change ofDOMand bacterial community succession are closely related to N removal performance,providing an ecological basis for developing techniques for N-rich effluent treatment.展开更多
基金supported by the Science and Technology Major Program of Yunnan(No.202402AG0500103)the Industrial Innovation Talent Project of Yunnan(No.XDYC-CYCX-2023007)the National Key Research and Development Program of China(No.2023YFC3709100).
文摘Exogenous organic input impacts soil phosphorus transformation.Meanwhile,dissolved organic matter(DOM)is crucial for biogeochemical functions.Nevertheless,the interaction between the structural composition of DOM and phosphorus during the soil formation process of phosphogypsum(PG)remains unknown.This study explores the interaction between the structural composition of DOM and phosphorus in enhanced PG under the participation of fungal microorganisms through different application amounts of exogenous organic matter and culture time.Results show that application of exogenous organic matter led to varying degrees of increase in dissolved organic carbon(DOC)concentration and humification extent in the soil-like substrate.Additionally,the relative abundance of protein-like component C3 exhibited a trend of initial increase followed by decline over time.The contents of available phosphorus(AP),microbial biomass phosphorus(MBP),and active phosphorus pools(Active-P)in the soil-like substrate are all enhanced overall.Furthermore,a significant correlation exists between DOC and AP as well as MBP.This suggests that DOM is a crucial factor in enhancing the phosphorus availability of the soil-like substrate.The enrichment of known phosphate-solubilizing fungi in culturing favors the decomposition,activation and utilization of hard-to-mineralize phosphorus components in the soil-like substrate.These findings help understand DOM’s biogeochemical behavior and offer insights into PG utilization and the sustainable development of China’s phosphorus industry.
基金The National Basic Research Program of China (973 Program) under contract No.2009CB421202the Public Science and Technology Research Funds Projects of Ocean of China under contract No. 200905012the National Natural Science Foundation of China under contract Nos 40976110 and 40706061
文摘The retrieval of dissolved organic carbon （DOC） distribution by remote sensing is mainly based on the em- pirical relationship of DOC concentration and colored dissolved organic matter （CDOM） concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world＇s major estuaries and bays. It is found that, generally, the C- DOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a non- conservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea（ECS） was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeo- chemical processes were analyzed except for the physical mixing process with the data from late autumn （November, 2010） and winter （December, 2009） cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological pro- cesses. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm （CSDM） was proposed： when the biological influence was significant （Chl a greater than 0.8 μg/dm3）, DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant （Chl a less than 0.8 μg/dm3）, the direct DOC concentration and CDOM concentration relationship was used. Based on the pro- posed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.
基金Supported by National Natural Science Foundation of China(31160103)Scientific and Technological Development Project of Yanbian University(YDKH[2011]32)Key Program of Department of Science and Technology of Jilin Province(20140204045SF)~~
文摘In this study, the spatial and temporal distribution characteristics of dis- solved organic carbon （DOC） in water-logged paddy soil in Yanbian were investigat- ed under conditions of different fertilization types （single application of chemical fer- tilizer, mixed application and chemical and organic fertilizers and single application of organic fertilizer） and cultivation years （80 years and 120 years）. The results showed that the spatial and temporal distribution of DOC in water-logged paddy soil changed significantly with time going by. The single application of chemical fertilizer or mixed application of chemical and organic fertilizers contributed to the release of DOC in top paddy soil under water-logging condition; the single application of organ- ic fertilizer promoted the accumulation of DOC in bottom paddy soil, resulting in great heterogeneity of DOC in the vertical space, but the single application of chem- ical fertilizer weakened the vertical spatial heterogeneity of soil DOC; the DOC con- tent in the 80-year-old water-logged paddy soil was higher and more stable than that in the 120-year-old soil.
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.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 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 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The National Natural Science Foundation of China under contract Nos 42276255,41976228,42176227 and 42306262the National Polar Special Program under contract Nos IRASCC 01-01-02,IRASCC 02-02-03,and IRASCC 02-02-05the Scientific Research Fund of the Second Institute of Oceanography under contract Nos JG2211 and JG2212.
文摘Dissolved organic carbon(DOC)constitutes the largest organic carbon reservoir in the ocean and plays a vital role in the oceanic carbon cycle.However,research on DOC in Antarctica has been limited,largely due to difficulties in sample collection.In this study,we investigate chromophoric dissolved organic matter(CDOM)in the Cosmonaut Sea and Cooperation Sea,Antarctica.The relative abundances of CDOM,as indicated by the absorption coefficient at 254 nm(a_(254)),exhibit significant variability,ranging from 1.29 m^(-1) to 8.37 m^(-1).The diatom species B is the primary contributor to CDOM in the region influenced by the Antarctic slope current.Using excitation-emission matrix fluorescence spectroscopy coupled with parallel factor analysis(EEM-PARAFAC),we identify three fluorescent components:one protein-like component(C1)and two humic-like components(C2 and C3).Our findings indicate that strong microbial activity in the euphotic zones of the Cosmonaut Sea and Cooperation Sea serves as a primary pathway for the removal of protein-like substances while also acting as a significant source of humic-like substances.Microbial degradation likely accounts for the decoupling of the vertical distribution of DOC and phytoplankton.Furthermore,the intrusion of modified circumpolar deep water(mCDW)into the euphotic zones of open ocean areas influences the distribution of CDOM at depths shallower than 200 m.These results have important implications for enhancing our understanding of the dynamics of CDOM and DOC in east Antarctica,as well as for improving assessments of the carbon cycle.
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 δ^(18)O) 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 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Basic Research Project of Universities in Hebei Province,Affiliated with Shijiazhuang City,Grant/Award Number:241791187ANatural Science Foundation of Hebei Province,Grant/Award Number:E2024208033+1 种基金Hebei Province graduate student innovation ability training program,Grant/Award Number:CXZZSS2025068Hebei Provincial Key Research Projects,Grant/Award Number:21373904D。
文摘Dissolved organic matter(DOM)in rivers plays a key role in the global carbon cycle and aquatic ecosystems,yet its spatiotemporal dynamics across complex terrains remains inadequately characterized.To address this gap,we conducted seasonal sampling along the Luan River and examined how DOM composition varies over space and time in response to environmental drivers.Using parallel factor analysis(PARAFAC),we identified two humic-like components(C1+C2,Em>380 nm)and one protein-like component(C3,Em<380 nm).DOM fluorescence intensity was lowest in winter,while C1 and C3 levels peaked in autumn and C2 in summer(p<0.05).Spatially,C1 and C3 levels were highest downstream regions,whereas C2 peaked in the midstream section(p<0.05).Microbial sources dominated DOM in spring,winter,and in both headwater and downstream areas(FI>1.9).Principal coordinates analysis(PCoA)combined with multi-response permutation process(MRPP)confirmed significant spatiotemporal differences in DOM composition(p<0.05).Random forest modeling showed humic-like components were more sensitive to environmental changes.Redundancy analysis(RDA)and Mantel tests identified temperature as the dominant seasonal driver of DOM variation(p<0.05),while dissolved total phosphorus(DTP)and nitrate nitrogen(NO_(3)^(-)-N)were the key spatial determinants.Significant correlations were also observed between NO_(3)^(-)-N and ammonium nitrogen(NH_(4)^(+)-N),as well as between DTP and DOM,suggesting shared origins and compositional linkages(p<0.05).Our findings highlight the pronounced seasonal and spatial heterogeneity of DOM in multi-terrain river systems,offering valuable insights into carbon dynamics and ecosystem functioning in river systems.
基金supported by the National Key Research and Development Program of China (Nos.2018YFE0105600 and 2020YFC1806803)the New Zealand MBIE Catalyst Fund (No.92846082).
文摘Woodchip bioreactors are an eco-friendly technology for removing nitrogen(N)pollution.However,there needs to be more clarity regarding the dissolved organicmatter(DOM)characteristics and bacterial community succession mechanisms and their association with the N removal performance of bioreactors.The laboratory woodchip bioreactors were continuously operated for 360 days under three influent N level treatments,and the results showed that the average removal rate of TN was 45.80 g N/(m^(3)·day)when the influent N level was 100 mg N/L,which was better than 10 mg N/L and 50 mg N/L.Dynamic succession of bacterial communities in response to influent N levels and DOM characteristics was an important driver of TN removal rates.Medium to high N levels enriched a copiotroph bacterial module(Module 1)detected by network analysis,including Phenylobacterium,Xanthobacteraceae,Burkholderiaceae,Pseudomonas,and Magnetospirillaceae,carrying N-cycle related genes for denitrification and ammonia assimilation by the rapid consumption of DOM.Such a process can increase carbon limitation to stimulate local organic carbon decomposition to enrich oligotrophswith fewer N-cycle potentials(Module 2).Together,this study reveals that the compositional change ofDOMand bacterial community succession are closely related to N removal performance,providing an ecological basis for developing techniques for N-rich effluent treatment.
