The temporal evolution of molecular compositions and changes in structural features of Hillsboro Canal (Florida, USA) dissolved organic matter (DOM) was studied with an emphasis on nitrogen and ...sulfur containing molecules, after a 13 day time-series exposure to simulated sunlight. The Hillsboro Canal drains from the ridge and slough wetland environment underlain by peat soils from the northern extent of the Greater Everglades Ecosystem. The Hillsboro Canal-DOM was characterized by combining ultrahigh-resolution mass spectrometry (FT-ICR-MS), high-field nuclear magnetic resonance spectroscopy (1H NMR), size exclusion chromatography (SEC) with UV detection, and ultraviolet/visible (UV/vis) absorbance and excitation emission matrix (EEM) fluorescence spectroscopy. Size exclusion chromatography (SEC) demonstrated progressive depletion of higher mass molecules and a concomitant decrease of absorbance during photo-irradiation. NMR and FT-ICR-MS revealed nonlinear temporal evolution of DOM. In fact, FT-ICR-MS showed an initial depletion of supposedly chromophoric molecules often carrying major unsaturation accompanied by an uneven evolution of numbers of CHO, CHOS and CHNO compounds. While CHNO compounds continually increased throughout the entire photo-exposure time, CHO and CHOS compounds temporarily increased but declined after further light exposure. Progressive loss of highly unsaturated compounds was accompanied by production of low mass CHO and CHNO compounds with high O/C ratios. Area-normalized 1H NMR spectra of DOM in water and of the water insoluble fraction (~5%) in methanol revealed clear distinctions between irradiated and non-irradiated samples and congruent evolution of DOM structural features during irradiation, with more uniform trends in methanolic-DOM. Photoirradiation caused initial photoproduction of oxygenated aliphatic compounds, continued depletion of phenols and oxygenated aromatics, substantial change from initial natural product derived olefins to photoproduced olefins, and uneven evolution of carboxylated and alkylated benzene derivatives. This study demonstrates longer-term heteroatom-dependent photochemistry of DOM, which will affect the speciation of N and S heteroatoms, their connections to inorganic nutrients, and potentially their bioavailability.
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•Photo-irradiation affects molecular and spectroscopic features of peat-derived DOM.•Longer-term heteroatom-dependent photochemistry affects DON and DOS speciation.•The temporal evolution of heteroatom photoproducts was non-linear.•Ultimate fate of DON and DOS compounds is strongly driven by photochemistry.
The behavior and composition of hydrochar-based dissolved organic matter (DOM) would affect the efficiency of copper (Cu) removal from wastewater through adsorption. In this study, the reed was ...hydrolyzed in the presence of feedwater with and without ZnCl2, FeCl3, and SnCl4 to produce pristine hydrochars (PHCs), which were named H2O-HC, ZnCl2-HC, FeCl3-HC, and SnCl4-HC. After removal of DOM, washed hydrochars (WHCs) were obtained, labelled as W–H2O-HC, W-ZnCl2-HC, W-FeCl3-HC, and W-SnCl4-HC. The release dynamics of DOM from PHCs were analyzed, and the adsorption behaviors of Cu2+ on both PHCs and WHCs were investigated. The results showed that chloride-modifications were beneficial for the porosity, specific surface area (SSA), and functional groups of WHCs. Meanwhile, the quantity of hydrochar-based DOM was significantly affected by chloride-modifications. In particular, the relative contents of Ar–P and Fa-L in the DOM released from hydrochars varied with time and modification. Furthermore, the Qe of Cu2+ adsorption on WHCs followed the order of W-SnCl4-HC > W-FeCl3-HC > W-ZnCl2-HC > W–H2O-HC at 15 °C. Compared to PHCs, the adsorption capacity of Cu2+ on WHCs was improved by 7.15–119.77% at the temperature of 35 °C. Simultaneously, the adsorption capacity of Cu2+ in WHCs showed a significant correlation with the SSA via physical adsorption (P < 0.05). Moreover, XPS analysis revealed that Cu2+ adsorption also occurred via complexation and chelation through newly formed Cu–O group between W-SnCl4-HC and Cu2+. Notably, the increase of Cu2+ adsorption in WHCs was significantly correlated with the release of Fa-L and Ar–P from PHCs (P < 0.05). This study found that the content and composition of hydrochar-based DOM could be a major driving factor for Cu2+ adsorption.
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•The adsorption performance of chlorides-modified hydrochars for Cu2+ was studied.•The Qe of Cu2+ adsorption followed the order of W-SnCl4-HC > W-FeCl3-HC > W-ZnCl2-HC > W–H2O-HC at 15 °C.•Cu2+ removal efficiency of hydrochars was improved significantly by removing DOM.•Due to complexation, DOM should not be overlooked in the adsorption of Cu2+ on hydrochars.
Persulfate advanced oxidation technology is widely utilized for remediating organic-contaminated groundwater. Post-remediation by persulfate oxidation, the aromaticity of dissolved organic matter ...(DOM) in groundwater is significantly reduced. Nevertheless, the evolution trends of aromaticity and related structural changes in DOM remained unclear. Here, we selected eight types of DOM to analyze the variation in aromaticity, molecular weight, and fluorescence characteristics during oxidation by persulfate using optical spectroscopy and parallel faction analysis combined with two-dimensional correlation spectroscopy analysis (2D PARAFAC COS). The results showed diverse trends in the changes of aromaticity and maximum fluorescence intensity (Fmax) among different types of DOM as the reaction time increases. Four types of DOM (humic acid 1S104H, fulvic acid, and natural organic matters) exhibited an initially noteworthy increase in aromaticity followed by a decrease, while others demonstrated a continuous decreasing trend (14.3%–69.4%). The overall decreasing magnitude of DOM aromaticity follows the order of natural organic matters ≈ commercial humic acid > fulvic acid > extracted humic acid. The Fmax of humic acid increased, exception of commercial humic acid. The Fmax of fulvic acid initially decreased and then increased, while that of natural organic matters exhibited a decreasing trend (86.4%). The fulvic acid-like substance is the main controlling factor for the aromaticity and molecular weight of DOM during persulfate oxidation process. The oxidation sequence of fluorophores in DOM is as follows: fulvic-like substance, microbial-derived humic-like substance, humic-like substance, and aquatic humic-like substance. The fulvic-like and microbial-derived humic-like substances at longer excitation wavelengths were more sensitive to the response of persulfate oxidation than that of shorter excitation wavelengths. This result reveals the structure evolution of DOM during persulfate oxidation process and provides further support for predicting its environmental behavior.
•Aromaticity in eight DOM decreased by 14.3%–69.4% after 32 h of oxidation•Persulfate system enhanced fluorescence intensity of HA extracted from environment•Fulvic acid-like substance reflected the aromaticity and molecular weight in DOM•The evolution mechanism of fluorophores was elucidated by 2D PARAFAC COS
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•Lignin content is inversely proportional to DOM release from the biochar.•Biochar pyrolyzed sawdust with more lignin extracted less Fe from soil.•Sawdust biochar with less lignin can ...enhance the As leaching from soil.
Biochar is widely used material whose physical and chemical characteristics been widely investigated. Nevertheless, dissolved organic matter (DOM) released from biochar has received relatively little attention. In particular, little research has been conducted to understand the effects of feedstock biomass components on biochar DOM release. To control the amount of DOM released from biochar, this study focuses on the role of lignin, a component of biomass. To this end, samples of sawdust containing different lignin contents and a binary mixture of cellulose and lignin were pyrolyzed at 400 and 700 °C, and then the physico-chemical properties of the resulting biochar, and Fe(II) and As mobility were investigated in arsenic-contaminated soil amended by the biochar. This study showed that lignin is an critical factor in controlling the release of DOM. The amount of DOM released from the sawdust biochar with the lowest lignin content was 33% (400 °C) and 44% (700 °C) lower than those produced from lignin-rich biochar (sawdust without the extraction of lignin). The amount of oxalic acid in DOM decreased with increased lignin content. In addition, As mobility and the transformation of Fe(II) were minimized when lignin-rich biochar was applied to the As-contaminated soil. More importantly, these results suggest that controlling the lignin content of biomass can be universally applied to predict DOM concentrations of the biochars produced.
•Microbes promoted the dissolution of oxides on mineral surfaces in water.•Extracellular polymeric substances contributed to mineral biotransformation.•Electronic transfer between minerals and ...microbes changed the mineral activation.•FT-ICR-MS measured the decomposition of organic matters at the molecular level.•Biotransformation of minerals inhibited the decomposition of organic matters.
Photochemical reactions that widely occur in aquatic environments play important roles in carbon fate (e.g., carbon conversion and storage from organic matter) in ecosystems. Aquatic microbes and natural minerals further regulate carbon fate, but the processes and mechanisms remain largely unknown. Herein, the interaction between Escherichia coli and pyrite and its influence on the fate of carbon in water were investigated at the microscopic scale and molecular level. The results showed that saccharides and phenolic compounds in microbial extracellular polymeric substances helped remove pyrite surface oxides via electron transfer. After the removal of surface oxides on pyrite, the photochemical properties under visible-light irradiation were significantly decreased, such as reactive oxygen species and electron transfer capacity. Unlike the well-accepted theory of minerals protecting organic matter in the soil, the organic matter adsorbed on minerals preferred degradation due to the enhanced photochemical reactions in water. In contrast, the minerals transformed by microbes suppressed the decomposition of organic matter due to the passivation of the chemical structure and activity. These results highlight the significance of mineral chemical activity on organic matter regulated by microbes and provide insights into organic matter conversion in water.
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Dissolved organic matter (DOM), as the most active ingredient in compost, directly determines the speciation and environmental behavior of HMs. Here, the binding properties of DOM derived from ...chicken-manure compost (CHM), cow-manure compost (COM) and pig-manure compost (PIM) with HMs were explored by analyses of Fluorescence excitation-emission matrix parallel factor (EEM-PARAFAC) and two-dimensional correlation Fourier transform infrared spectroscopy (2D-FTIR-COS). Results showed that the binding characteristics vary with origin of DOM and type of HMs. The fulvic-like component dominated the transformation of HMs speciation, and CHM-DOM had higher affinity with HMs and greater risk causing pollution due to its higher aromaticity, molecular weight and distribution of fluorescent components. Moreover, Cu(II) can efficiently bind to DOM with the stability constants (log kM) ranging from 4.53 to 5.38, followed by Pb(II) (3.34–3.57), whereas Cd(II) can hardly bind to DOM. The amide and polysaccharide were the predominant sites for HMs binding in CHM-DOM, and polysaccharide and phenolic in COM-DOM, while phenolic and amide in PIM-DOM, respectively. Although the proportion of protein-like components and non-fluorescent polysaccharides in DOM were low, their role in HMs binding should not be ignored. In brief, the environmental risk caused by livestock manure compost may originate from interactions between DOM and HMs.
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•Binding characteristics vary with origin of DOM and type of HMs.•CHM-DOM may cause environmental risk due to its interaction with HMs.•Protein and polysaccharides should not be ignored in HMs binding.
Sponge holobionts (i.e., the host and its associated microbiota) play a key role in the cycling of dissolved organic matter (DOM) in marine ecosystems. On coral reefs, an ecological shift from ...coral-dominated to algal-dominated ecosystems is currently occurring. Given that benthic corals and macroalgae release different types of DOM, in different abundances and with different bioavailability to sponge holobionts, it is important to understand how the metabolic activity of the host and associated microbiota change in response to the exposure to both DOM sources. Here, we look at the differential gene expression of two sponge holobionts 6 hours after feeding on naturally sourced coral- and macroalgal-DOM using RNA sequencing and meta-transcriptomic analysis. We found a slight, but significant differential gene expression in the comparison between the coral- and macroalgal-DOM treatments in both the high microbial abundance sponge Plakortis angulospiculatus and the low microbial abundance sponge Haliclona vansoesti. In the hosts, processes that regulate immune response, signal transduction, and metabolic pathways related to cell proliferation were elicited. In the associated microbiota carbohydrate metabolism was upregulated in both treatments, but coral-DOM induced further lipid and amino acids biosynthesis, while macroalgal-DOM caused a stress response. These differences could be driven by the presence of distinct organic macronutrients in the two DOM sources and of small pathogens or bacterial virulence factors in the macroalgal-DOM. This work provides two new sponge meta-transcriptomes and a database of putative genes and genetic pathways that are involved in the differential processing of coral- versus macroalgal-DOM as food source to sponges with high and low abundances of associated microbes. These pathways include carbohydrate metabolism, signaling pathways, and immune responses. However, the differences in the meta-transcriptomic responses of the sponge holobionts after 6 hours of feeding on the two DOM sources were small. Longer-term responses to both DOM sources should be assessed to evaluate how the metabolism and the ecological function of sponges will be affected when reefs shift from coral towards algal dominance.
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•Interaction between BSA and four antibiotics was studied by fluorescence quenching.•Static quenching occurred and binding ability followed order: TTC > CPC > OTC > PEG.•β-lactam ...showed higher removal rate than tetracycline by γ-radiation only or with BSA.•No correlation between k/kBSA and the binding affinity was observed.•BSA has little effect trend of abatement of antimicrobial activity by γ-irradiation.
In this study, to explore the influence of protein on antibiotics degradation during ionizing irradiation, the binding interaction between bovine serum albumin (BSA) and the broad spectrum β-lactam and tetractycline antibiotics and its effect on antibiotic degradation were investigated. Static quenching happened between BSA and antibiotics involving penicillin G (PEG), cephalosporin C (CPC), oxytetracycline (OTC) and tetracycline hydrochloride (TTC), indicating the formation of non-fluorescence complexes. The binding capacity followed the order: TTC > CPC > OTC > PEG. As exposed to γ-irradiation, the β-lactam antibiotics showed a higher degradation rate than the tetracyclines. The degradation rate constant (k) of CPC and PEG was 1.4–2.0 times higher than that of OTC and TTC. In presence of BSA, the k values (kBSA) of all the four antibiotics decreased greatly and the degradation rate of CPC and PEG was still higher by 1.2–1.3 times than that of OTC and TTC. No correlation between k/kBSA and the binding affinity was observed. The presence of BSA has little effect on the trend of abatement of antimicrobial activity to S. aureus during γ-irradiation. This suggests that the inhibition of protein to antibiotic degradation was mainly attributed to the competition of protein for the active species such as ·OH radical formed during γ-irradiation, while the binding ability of protein to antibiotics has no obvious effect. The results of this study contributed to develop technical strategies to improve the removal of antibiotics completely in real water matrices.
The occurrence of microplastics (MPs) as emerging contaminants in the environment may cause changes in water or sediment characteristics, and further affect their biogeochemical cycles. Thus, ...insights into the interactions between dissolved organic matter (DOM) and MPs are essential for the assessment of environmental impacts of MPs in ecosystems. Integrating spectroscopic methods with chemometric analyses, this work explored the chemical and microstructural changes of DOM-MP complex to reveal the mechanism of DOM-MP interaction at a molecular level. MPs were found to interact with the aromatic structure of DOM via π-π conjugation, then be entrapped in the DOM polymers by the carboxyl groups and C=O bonds, constituting a highly conjugated co-polymer with increased electron density. This induced the fluorescence intensity increase in DOM. The interaction affinity of DOM-MP was highly dependent on the MP size and solution pH. This work offers a new insight into the impact of MP discharge on environment and may provide an analytical framework for evaluating MP hetero-aggregation and the roles of MPs in the transportation of other contaminants. Furthermore, the integrated methods used in this work exhibit potential applications in exploring the fragmentation processes of MPs and formation of secondary MPs under natural conditions.
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•DOM is adhered onto MPs via π-π conjugation, carboxyl groups and C=O bonds.•MP-DOM constitutes a conjugated co-polymer with an elevated electron density.•Interaction between DOM and MP depends on MP size and solution pH.•The approach has a great potential in elucidating plastics fragmentation and secondary MPs formation.
The interaction mechanism between humic acid and polystyrene microplastics is explored and new insights into the impact of MP discharge on environment are provided.
In recent years, rigid analogs of phenylalkylamine hallucinogens have appeared as recreational drugs. Examples include 2-(8-bromo-2,3,6,7-tetrahydrobenzo1,2-b:4,5-b′difuran-4-yl)ethan-1-amine ...(2C-B-FLY) and 1-(8-bromobenzo1,2-b;4,5-b’difuran-4-yl)-2-aminopropane (Bromo-DragonFLY, DOB-DFLY). Although some rigid compounds such as DOB-DFLY reportedly have higher potency than their non-rigid counterparts, it is not clear whether the same is true for 2C-B-FLY and other tetrahydrobenzodifurans. In the present study, the head twitch response (HTR), a 5-HT2A receptor-mediated behavior induced by serotonergic hallucinogens, was used to assess the effects of 2,5-dimethoxy-4-bromoamphetamine (DOB) and its α-desmethyl homologue 2,5-dimethoxy-4-bromophenethylamine (2C-B), as well as their benzodifuranyl and tetrahydrobenzodifuranyl analogs, in C57BL/6J mice. DOB (ED50 = 0.75 μmol/kg) and 2C-B (ED50 = 2.43 μmol/kg) induced the HTR. The benzodifurans DOB-DFLY (ED50 = 0.20 μmol/kg) and 2C-B-DFLY (ED50 = 1.07 μmol/kg) had significantly higher potency than DOB and 2C-B, respectively. The tetrahydrobenzodifurans DOB-FLY (ED50 = 0.67 μmol/kg) and 2C-B-FLY (ED50 = 1.79 μmol/kg), by contrast, were approximately equipotent with their non-rigid counterparts. Three novel tetrahydrobenzodifurans (2C-I-FLY, 2C-E-FLY and 2C-EF-FLY) were also active in the HTR assay but had relatively low potency. In summary, the in vivo potency of 2,5-dimethoxyphenylalkylamines is enhanced when the 2- and 5-methoxy groups are incorporated into aromatic furan rings, whereas potency is not altered if the methoxy groups are incorporated into dihydrofuran rings. The potency relationships for these compounds in mice closely parallel the human hallucinogenic data. The high potency of DOB-DFLY is probably linked to the presence of two structural features (a benzodifuran nucleus and an α-methyl group) known to enhance the potency of phenylalkylamine hallucinogens.
•The hallucinogens 2C-B and DOB induced head twitches in mice.•Tethering the methoxy groups into a benzodifuran nucleus increased potency.•Tethering the methoxy groups into a tetrahydrobenzodifuran nucleus did not alter potency.•The benzodifuran hallucinogen Bromo-DragonFLY was highly potent in mice.
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