The removal of four dissolved organic matter (DOM) fractions, non-acid hydrophobics, hydrophobic acids, hydrophilics and transphilics, was achieved by coagulation-UV/H2O2 oxidation in ...post-pharmaceutical wastewater (PhWW). Coagulation with Polyferric chloride (PFC), Polymeric ferric sulfate (PFS) and Polymeric aluminum ferric chloride (PAFC) was studied separately to evaluate the effects of the initial pH and coagulant dosage. The coagulation-UV/H2O2 oxidation method resulted in much higher reduction rates for dissolved organic carbon (DOC) (by 75%) and UV254 (by 92%) than coagulation or UV/H2O2 oxidation alone. The proportion of non-acid hydrophobics, hydrophobic acids, transphilics and hydrophilics removed by coagulation was 54%, 49%, 27% and 12 %, while the combined treatment removed 92%, 87%, 70% and 39%, respectively. Parallel factor analysis (PARAFAC) of fluorescence measurements revealed that the humic-like fluorescent component C4 showed the highest removal (by 44%) during the coagulation stage. After coagulation-UV/H2O2 treatment, the humic-like fluorescent component C3 had the highest removal (by 72%), whereas xenobiotic organic fluorescent components C1 and C4 remained recalcitrant to decomposition. Significant correlations (R2 > 0.8) between C1 and the hydrophobic acids and non-acid hydrophobics suggested the possibility of using fluorescence spectroscopy as an effective tool to assess variations in DOM fraction treatment efficacy in coagulation-UV/H2O2 systems. After the combined treatment, toxic inhibition of cellular activity by post PhWW decreased from 88% to 47% and biodegradability increased from 0.1 to 0.52.
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The impact of thermal remediation on soil function has drawn increasing attention. So far, as the most active fraction of soil organic matter, the evolution of dissolved organic matter (DOM) during ...the thermal remediation lacks in-depth investigation, especially for the temperatures value below 100 °C. In this study, a series of soil thermal treatment experiments was conducted at 30, 60, and 90 °C during a 90-d period, where soil DOM concentration increased with heating temperature and duration. The molecular weight, functional groups content and aromaticity of DOM all decreased during the thermal treatment. The excitation-emission matrices (EEM) results suggested that humic acid-like substances transformed into fulvic acid-like substances (F
III
/F
V
increased from 0.27 to 0.44) during the heating process, and five DOM components were further identified by EEM-PARAFAC. The change of DOM structures and components indicated the decline of DOM stability and hydrophilicity, and can potentially change the bioavailability and mobility. Elevated temperature also resulted in the decline of DOM complexation ability, which may be caused by the loss of binding sites due to the decrease of polar function groups, aromatic structures and hydrophilic components. This study provides valuable information about the evolution of DOM during thermal remediation, which would potentially change the fate of metal ions and the effectiveness of the post-treatment technologies in the treated region.
Pharmaceuticals and personal care products (PPCPs) are emerging contaminants that have raised urgent environmental issues. The dissolved organic matter (DOM) plays a pivotal role on PPCPs' migration ...and transformation. To obtain a comprehensive understanding of the occurrence and distribution of PPCPs, a seasonal sampling focused on the riverine system in coastal zone, Tianjin, Bohai Rim was conducted. The distribution and transformation of thirty-three PPCPs and their interaction with DOM were investigated, and their sources and ecological risks were further evaluated. The total concentration of PPCPs ranges from 0.01 to 197.20 μg/L, and such value is affected by regional temperature, DOM and land use types. PPCPs migration at soil-water interface is controlled by temperature, sunlight, water flow and DOM. PPCPs have a high affinity to the protein-like DOM, while the humus-like DOM plays a negative influence and facilitates PPCPs' degradation. It is also found that protein-like DOM can represent point source pollution, while humus-like substances indicate non-point source (NPS) emission. Specific PPCPs can be used as markers to trace the source of domestic discharge. Additionally, daily use PPCPs such as ketoprofen, caffeine and iopromide are estimated to be the main risk substances, and their ecological risk varies on space, season and river hydraulic condition.
Lentic ecosystems are important agents of local and global carbon cycling, but their contribution varies along gradients of dissolved organic matter (DOM) and productivity. We investigated how ...contrasting summer and autumn precipitation can shape annual and inter-annual variation in ecosystem carbon (C) flux (gross primary production (GPP), ecosystem respiration (ER), and CO2 efflux) in two subtropical lakes differing substantially in trophic state and water color. Instrumented buoys recorded time series of free-water DO, terrestrial DOM (tDOM), chlorophyll a, water temperature profiles, and meteorological measurements over five years (2009–2011 and 2014–2015). Reduced precipitation caused immediate and prolonged effects on C flux in both lakes. During the drought year (2014) GPP and ER declined by 60 to 80% and both lakes were either CO2 sinks or neutral. In the subsequent wet year (2015), GPP and ER increased by 40 to 110%, and both lakes shifted to strong net CO2 emitters. Higher ecosystem R resulted from larger GPP while higher tDOM contributed to a dramatic increase in dissolved inorganic carbon, which intensified CO2 emission in both lakes. C flux was more responsive in the clear mesotrophic lake, declining by approximately 40% in the cumulative GPP and ER, and increasing by >400% in CO2 efflux whereas changes in the oligotrophic colored lake were more modest (approximately 30% and 300% for metabolic declines and efflux increases, respectively). Temporal variation and magnitude of C flux were governed by tDOM-mediated changes in epilimnetic nutrient levels and hypolimnetic light availability. This study demonstrated terrestrial loads of DOM strongly influence the inter-annual response and sensitivity of ecosystem C flux to variation in inter-annual precipitation. Our findings have important implications for predicting the trend, magnitude, duration, and sensitivity of the response of C flux in subtropical lakes/reservoirs to future changes in precipitation patterns under altered climatic conditions.
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•Effects of droughts on inter-annual C fluxes were studied in subtropical lakes.•Multi-parameter probes were deployed to record key parameters over five years.•Lakes shifted from a C sink in dry year to C source in subsequent normal year.•C fluxes were more responsive to droughts in the mesotrophic colored lake.•Terrestrial DOM serves as a driver for the response of lakes to droughts.
Dissolved organic matter (DOM) is widely present in aqueous environments and plays a significant role in pollutant mitigation and transformation. So far, excitation-emission matrix (EEM) fluorescence ...spectroscopy coupled with parallel factor analysis (PARAFAC) has been widely applied to quantify fluorescent DOM. However, this approach fails to provide accurate concentration of DOM when fluorescent contaminants exist. In this work, a new method, prior linear decomposition (PLD), is developed to solve this problem by introducing prior information, i.e., EEMs of DOM, into data decomposition. First, EEM of humic acid (HA) with different numbers of random Gaussian peaks are tested to confirm the robustness of PLD. The percentages for the relative errors within 5% are found to be 97.7% and 69% using PLD and PARAFAC, respectively. Then, the determination of mixture of HA with several contaminants is performed, validating the feasibility of DOM quantification and capability of contaminant diagnosis using PLD for synthetic water samples. Finally, DOM-containing natural water samples collected from a polluted lake, river and wastewater treatment plant (WWTP) are measured. The testing results confirm that PLD provides an accurate result with less evaluated error than PARAFAC and the EEMs of the contaminants can be inferred precisely. This work clearly demonstrates that PLD offers a robust approach for quantifying fluorescent DOM, which is of great significance in both natural and engineered aqueous environments.
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•Interfering substances are identified using prior linear decomposition (PLD).•DOM can be accurately quantified by using PLD in the presence of interferences.•PLD provides a more accurate and rapid quantification result than PARAFAC.•PLD is capable of on-line monitoring fluorescent DOM in water.
Previous research has focused on dissolved organic carbon (DOC) as a surrogate for dissolved organic matter (DOM) in pharmaceutical wastewater. Dissolved organic nitrogen (DON) as a part of DOM has ...received little attention. This study investigated the removal characteristics of DON and its influence on the N-nitrosodimethylamine formation potential (NDMA FP) and acute toxicity of DOM in a full-scale hydrolysis/acidification + anaerobic/anoxic/aerobic + moving bed biofilm reactor (MBBR) process treating pharmaceutical wastewater. Results showed that maximum removal of DON (68 ± 12%) was present in the anaerobic process. The removal of DON by anoxic and aerobic processes was negligible as a result of the production of new N-containing compounds that are characteristic of proteins/amino sugars and lipids. DON concentration decreased significantly in the MBBR process (p < 0.05, t-test), indicating that manipulation of the solids retention times (SRTs) could be a solution to minimize DON. Based on the Pearson correlation analysis, the behavior of NDMA FP and DOM acute toxicity was significantly associated with the 3 kDa < MW < 10 kDa (r = 0.709, p < 0.05) and MW < 3 kDa DON (r = 0.659, p < 0.05), respectively, and are not identical to that of DOC fractions (r = 0.037–0.466, p = 0.051–0.886). Moreover, the removal and molecular changes of DON are not coupled with that of DOC during biotreatment. Thus, testing the performance indicator of DON in pharmaceutical wastewater was recommended, as it provides important information for DOM removal characteristics.
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•Anaerobic and MBBR process are effective at removing DON.•DON and DOC removal are not coupled as well as their molecular changes.•DON fractions play significant roles in NDMA formation and acute toxicity of DOM.•Measurement of DON and its fractions are recommended in pharmaceutical wastewater.
Abiotic, biotic, and sparingly the xenobiotic factors are considered to influence the compositional variation of dissolved organic matter (DOM) in aquatic environments. Increasing discharge of ...xenobiotics into water bodies necessitates the need to investigate their effects on the key components of DOM. The effects of bisphenols (BP) and perfluoroalkylated substances (PFAS) on the fluorescence characteristics of pure humic substances (HS) and amino acids (AA) of DOM were examined by using excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) and the attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy in this work. The results showed that interactions of fulvic acid (FA), humic acid (HA), and tryptophan (Trp) with the xenobiotic compounds could generate some fluorescence components like both HS and AA components, whereas the interactions with tyrosine (Tyr) could only generate AA fluorescence components. In addition, it was revealed that the fluorescence intensity of HS decreases by 50–70% and 18–25% in the treatments of HA and FA, respectively, at low concentration (2.5 × 10−3 mg/L) of BP, while this increases by 350–425% and 18–25% at the same concentration of PFAS. However, both BP and PFAS increase the fluorescence intensity of AA. The findings suggest that the xenobiotic compounds are important factors affecting the compositional variation of DOM, especially in the anthropogenically-impacted water bodies.
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•Bisphenols (BP) influence the fluorophore of dissolved organic matter (DOM).•Perfluoroalkylated substances (PFAS) influence the fluorophore of DOM.•BP reduces the fluorescence intensity of humic-like substances (HS).•PFAS increases the fluorescence intensity of HS.•BP and PFAS increase the fluorescence intensity of amino-acids.
The water-rock interaction has a significant effect on the binding characteristics of dissolved organic matter and heavy metals when mine water flows in goaf. This study used fluorescence ...excitation-emission matrix (EEM) quenching combined with parallel factor (PARAFAC) analysis to characterize the binding properties of DOM with Fe (Ⅲ), Fe (Ⅱ+Ⅲ) and Mn (Ⅱ) in mine water under rock-influenced conditions. Two protein-like components and two humic-like components were identified by PARAFAC, in which protein-like components dominated (75.9%). The fluorescence intensity of each component can all be weakened, especially the stability constant (logKM) value of Fe (Ⅱ+Ⅲ) with fulvic-like acid and humic-like acid was the largest and the binding was more stable. Clay minerals and iron-bearing minerals in rocks had significant effects on the binding characteristics of DOM and metal ions under water-rock interaction. Iron ions released by the oxidation of pyrite and siderite in sandstone can reduce the fluorescence intensity of the derived components. The competitive adsorption effect of clay minerals on metal ions made the fluorescence intensity of the derived components under the action of sandstone containing less clay minerals (19.5%) be lower than that of mudstone (31.3%). Meanwhile, the process of water-rock interaction was accompanied by microbial activities to convert protein-like components into fulvic-like and humic-like components, or higher levels of stable substances. This study shows that when assessing the potential ability of mine water DOM and metal ions binding and migration during the flow of water in goaf it is crucial to take into account the presence of water-rock interaction.
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•EEM-PARAFAC analysis identified 2 protein-like and 2 humic-like components.•Iron ions from iron mine oxidation reduced the fluorescence intensity of DOM.•Competitive adsorption of clay minerals affected the binding of DOM and metal ions.•The process of water-rock interaction was accompanied with microbial activity.•Water-rock interaction manipulated DOM and heavy metal binding properties.
ABSTRACT Microbial photoautotroph-heterotroph interactions underlie marine food webs and shape ecosystem diversity and structure in upper ocean environments. Here, bacterial community composition, ...lifestyle preference, and genomic- and proteomic-level metabolic characteristics were investigated for an open ocean Synechococcus ecotype and its associated heterotrophs over 91 days of cocultivation. The associated heterotrophic bacterial assembly mostly constituted five classes, including Flavobacteria, Bacteroidetes, Phycisphaerae, Gammaproteobacteria, and Alphaproteobacteria. The seven most abundant taxa/genera comprised >90% of the total heterotrophic bacterial community, and five of these displayed distinct lifestyle preferences (free-living or attached) and responses to Synechococcus growth phases. Six high-quality genomes, including Synechococcus and the five dominant heterotrophic bacteria, were reconstructed. The only primary producer of the coculture system, Synechococcus, displayed metabolic processes primarily involved in inorganic nutrient uptake, photosynthesis, and organic matter biosynthesis and release. Two of the flavobacterial populations, Muricauda and Winogradskyella, and an SM1A02 population, displayed preferences for initial degradation of complex compounds and biopolymers, as evinced by high abundances of TonB-dependent transporters (TBDTs), glycoside hydrolase, and peptidase proteins. Polysaccharide utilization loci present in the flavobacterial genomes influence their lifestyle preferences and close associations with phytoplankton. In contrast, the alphaproteobacterium Oricola sp. population mainly utilized low-molecular-weight dissolved organic carbon (DOC) through ATP-binding cassette (ABC), tripartite ATP-independent periplasmic (TRAP), and tripartite tricarboxylate transporter (TTT) transport systems. The heterotrophic bacterial populations exhibited complementary mechanisms for degrading Synechococcus-derived organic matter and driving nutrient cycling. In addition to nutrient exchange, removal of reactive oxygen species and vitamin trafficking might also contribute to the maintenance of the Synechococcus-heterotroph coculture system and the interactions shaping the system. IMPORTANCE The high complexity of in situ ecosystems renders it difficult to study marine microbial photoautotroph-heterotroph interactions. Two-member coculture systems of picocyanobacteria and single heterotrophic bacterial strains have been thoroughly investigated. However, in situ interactions comprise far more diverse heterotrophic bacterial associations with single photoautotrophic organisms. In the present study, combined metagenomic and metaproteomic data supplied the metabolic potentials and activities of uncultured dominant bacterial populations in the coculture system. The results of this study shed light on the nature of interactions between photoautotrophs and heterotrophs, improving our understanding of the complexity of in situ environments.
The actual DOM in Chaohu Lake was used to feed cyanobacterial to explore the changes of microbial communities, fluorescence spectral characteristics and molecular composition of DOM during the ...degradation of cyanobacteria. It is found that cyanobacterial grow periodically depending on the concentration of nutrients with the decreasing concentration of nutrient salts. Both Bacteroidetes and Actinobacteria have strong correlation with algae growth. Bacteroidetes has a positive correlation with algae growth, relationship on the contrary, Actinobacteria has a negative relationship. The humus-like components in the four groups are similar, but the protein-like component (C3) shows periodic changes with the life process of cyanobacteria. The average molecular weight of each sample detected by Orbitrap high-resolution mass spectrometer increases slightly and the DOM increase aromaticity in the end. In this study, the molecule of Carboxyl-Rich Alicyclic Molecules (CRAM) is difficult to be done by photodegradation and biodegradation in the early periods, but some molecules of CRAM are selectively degraded by microorganisms in the final period. The growth of cyanobacterial lead to increasing the concentration of protein-like and carbohydrate-like molecule of DOM in the water. In the final stage, the molecule group of CHO disappear significantly and the molecule group of heteroatomic group increase.
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