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•DOM decreased bioaccumulation of ERY in aquatic organisms.•SRHA and SRFA inhibited ERY bioavailability greater than the other DOM.•ERY KDOC values increased with the content of humic ...and fulvic acid-like compounds.•DOM interacted with ERY via reactions of −COO− with ERY+ and H-bonding.•Inhibitory effects of DOM were related with its sources and properties.
Macrolides are widely used antibiotics with ubiquitous occurrence in aquatic environments. Unlike many emerging contaminants, macrolides are positively charged on their amine groups and are likely to interact with negative charge groups of dissolved organic matters (DOMs), which may alter macrolide bioaccumulation but yet to be explored. Here we evaluated the effects of different DOM (LeHA, PPHA, SRHA and SRFA) on erythromycin (an important macrolide) bioaccumulation into aquatic biota with 14C tracing. Results showed that ERY uptake in organisms was significantly inhibited by DOM (P < 0.05). In the presence of DOM at 20 mg L−1, the averaged equilibrium concentration (Ce) decreased by 28.1–40.6% for zebrafish and 10.9–25.8% for duckweed, corresponding to reductions in the bioconcentration factor (BCF) by 15.9–32.8% and 10.9–18.5%, respectively. Likely due to their higher carboxyl group content, SRHA and SRFA exhibited stronger inhibitory effects than LeHA or PPHA. The possible interactions between ERY and DOM were explored and results suggested that DOM inhibited ERY bioavailability by forming DOM-ERY complexes via ionic bonding of −COO− and ERY+, hydrogen bonding and hydrophobic partitioning. This study was the first to report on inhibitory effects of DOM on erythromycin bioavailability and has important implications for better understanding risks of macrolides.
The concentration of dissolved organic matter (DOM) in aquatic ecosystems has manifold direct and indirect consequences for primary and secondary production. Theoretical approaches suggest a negative ...effect of DOM on phytoplankton and a positive effect on bacteria, both of which alter the development of metazooplankton, the main consumer of bacteria and phytoplankton. However, experimental observations give heterogeneous results on the effect sizes of plankton in relation to DOM addition. Here, the synthesis of 411 effect sizes of plankton in response to DOM is presented from 59 studies. The referenced studies display effect sizes in relation to various DOM sources and different experimental designs. Thus, the hypothesis that neither DOM quality nor the type of experiment bias the effect size response of plankton was tested; the hypothesis was tested separately for bacterioplankton, phytoplankton and metazooplankton with the use of a meta-analytical approach. DOM quality was represented by the five different sources of DOM that are used most often in these experiments, i.e., natural water, bog leachate, glucose/sucrose, terrestrial plant leachate, and soil leachate. The experiment types comprised in situ experiments, i.e., experiments taking place under manipulated conditions in a natural ecosystem, and ex situ experiments, i.e., those taking place outside of a natural ecosystem. The meta-analyses showed that, although total DOM had a positive influence on the effect size of bacterioplankton and an insignificant influence on metazooplankton, the effect sizes differed significantly in relation to DOM source and the type of experiment. The effect size of phytoplankton, although not significantly related with total DOM, differed in response to DOM source but not experiment type. The results suggest that experimental conditions may produce artifacts in the strength of responses of aquatic biota to DOM concentrations.
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•The results of 59 experiments on plankton responses to DOM were synthesised.•The synthesis was made in regard to DOM source and type of experiment.•DOM source and type of experiments biased effect sizes of plankton.•Ambient conditions of experiments are critical to plankton responses to DOM.
Source, transformation, and preservation mechanisms of dissolved organic matter (DOM) remain elemental questions in contemporary marine and aquatic sciences and represent a missing link in models of ...global elemental cycles. Although the chemical character of DOM is central to its fate in the global carbon cycle, DOM characterizations in long‐term ecological research programs are rarely performed. We analyzed the variability in the quality of 134 DOM samples collected from 12 Long Term Ecological Research stations by quantification of organic carbon and nitrogen concentration in addition to analysis of UV‐visible absorbance and fluorescence spectra. The fluorescence spectra were further characterized by parallel factor analysis. There was a large range in both concentration and quality of the DOM, with the dissolved organic carbon (DOC) concentration ranging from less than 1 mgC/L to over 30 mgC/L. The ranges of specific UV absorbance and fluorescence parameters suggested significant variations in DOM composition within a specific study area, on both spatial and temporal scales. There was no correlation between DOC concentration and any DOM quality parameter, illustrating that comparing across biomes, large variations in DOM quality are not necessarily associated with corresponding large ranges in DOC concentrations. The data presented here emphasize that optical properties of DOM can be highly variable and controlled by different physical (e.g., hydrology), chemical (e.g., photoreactivity/redox conditions), and biological (e.g., primary productivity) processes, and as such can have important ecological consequences. This study demonstrates that relatively simple DOM absorbance and/or fluorescence measurements can be incorporated into long‐term ecological research and monitoring programs, resulting in advanced understanding of organic matter dynamics in aquatic ecosystems.
Extracellular matrix of periphyton has complex structural and chemical composition regulating metal transfer within biofilms with consequences for metal transfer to aquatic food webs. We investigated ...which metal species were retained in the loosely (LB) and the tightly bound (TB) fractions of the periphyton matrix from three pristine lakes at different growth stages. We measured the fluorescent dissolved organic matter (FDOM) composition with parallel factor analysis (PARAFAC) and the co-occurrence of essential and non-essential metals with FDOM in the two matrix fractions. The LB and TB fractions of periphyton had distinct fluorescence composition from the water column. The PARAFAC model identified five components, including two (C2 and C4) appearing to be of periphytic origin. The humic-like C2 was almost exclusive to periphyton and the tryptophan-like C4, associated to biofilm phototrophy, represented up to 47.0 ± 7.3 % of total fluorescence in the LB fraction. Most metals had significant positive relationships with four FDOM components in the LB fraction while C2 was the only component in the TB fraction to show such significant relationships. Components in the LB fraction seemed to act as scavengers for metals, preventing them from reaching the cellular fraction, while C2 from the TB fraction was likely promoting the bioavailability of essential metals for microorganisms inside periphyton. This study highlights the contrasting roles of the extracellular matrix on metal mobility beyond the usually proposed protection mechanisms. We suggest an experimental model for the study of metal regulation processes of the periphytic extracellular polymeric substances with a focus on the components produced by microorganisms within periphyton and their distribution in the different matrix fractions.
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•Periphyton was investigated for dissolved organic components and metal distribution•Extracellular matrices were rich in components from periphytic origins•Co-occurrence of components and metals were found in mobile and attached fractions•Suggested dual role of periphytic components on metals mobility•New model is proposed for periphyton regulation of metals
•Mass features MFs can have high abundance differences in DOM photo degradation experiments.•The same MFs show highest differences in stratified reservoirs.•Such KEY-MFs can be DBP precursors or ...flocculation relevant polyphenol-likes.•Both photo products and photo degraded MFs can be searched and found.
The molecular composition of dissolved organic matter (DOM) is of relevance for global carbon cycling and important for drinking water processing also. The detection of variation of DOM composition as function of time and space from a methodological viewpoint is essential to observe DOM processing and was addressed so far. High resolution concerning DOM quality was achieved with Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS).
However almost none of the existing FTICR-MS data sets were evaluated addressing the fate of single mass features / molecular formulas (MFs) abundance during experiments. In contrast to former studies we analyze the function of MF abundance of time and space for such MFs which are present in all samples and which were formerly claimed as recalcitrant in not all but a great number of studies. For the first time the reactivity of MFs was directly compared by their abundance differences using a simple equation, the relative intensity difference (δRI). Search strategies to find out the maximum δRI values are introduced. The corresponding MFs will be regarded as key MFs (KEY-MFs). In order to test this new approach data from a recent photo degradation experiment were combined with monitoring surveys conducted in two drinking water reservoirs. The δRI values varied over one order of magnitude (more than five-fold). MFs like C9H12O6 and C10H14O6 revealed high biogeochemical reactivity as photo products. Some of the KEY-MFs were identical with MFs identified as disinfection byproducts precursors in recent studies. Other KEY-MFs were oxygen-rich and relatively unsaturated (poly-phenol-like) and hence relevant to flocculation procedures.
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•Bulk soil IR spectra predict UV absorbance of water-extractable organic matter (WEOM)•WEOM humic-like fluorescence emission can be predictable from bulk soil IR spectra.•Optical properties of ...extracts are better predicted than organic C concentration.•WEOM aromatic components are better presented in soil IR spectra than aliphatic ones.•Compositional attributes of soil extracts are better predicted than these of WEOM.
Water-extractable organic matter (WEOM) is labile and a key component of soil organic matter. Thus, the prediction of soil WEOM concentration and composition-related characteristics is of great interest. The main objective of this study was to model and predict dissolved organic C (DOC) concentration and WEOM composition-related attributes of aqueous soil extracts using mid-infrared (IR) spectra of bulk soils coupled with partial least square (PLS) regression. Absorbance of UV light at 254 nm (Abs254), considered proportional to the concentration of aromatic substances in soil extracts, and light emission intensities proportional to concentrations of some components controlling WEOM fluorescence, were used as composition-related attributes of the soil extracts. The DOC-normalized Abs254 and emission intensities were used as composition-related attributes of WEOM. Application of PLS regressions for predicting spectroscopy-based composition-related attributes of aqueous soil extracts, using bulk soil IR spectra, is novel. Mid-IR spectra were determined for 216 soil samples collected from different (i) Israeli climate regions (Mediterranean and Semi-arid), (ii) types of land use (field crops, orchard and non-cultivated land), (iii) two depths (0–10 and 30–60 cm), (iv) sampling seasons (Fall and Spring). Prediction of DOC concentrations in the soil extracts was of limited and variable success evaluated by the coefficient of determination and slope of the linear regression of predicted vs measured values, with some soil subsets yielding no satisfactory predictions. However, Abs254 and emission intensities of fluorescent humic-like components were predicted more successfully than DOC concentrations, suggesting that WEOM aromatic and fluorescent components are better presented in soil IR spectra compared to WEOM aliphatic substances. Yet, prediction of the specific UV absorbance (SUVA), using bulk soil IR spectra, was less successful than prediction of Abs254. Prediction of DOC-normalized emission intensities of fluorescent components (analogous to SUVA in fluorescence spectroscopy) was not successful. The differences between the success of predicting extract properties, i.e., Abs254 and fluorescence emission intensities, and the prediction of DOC-normalized derivatives, suggest that concentrations of aromatic (fluorescent) components in soil extracts are better predicted using PLS regression analysis of bulk soil mid-IR spectra than the WEOM composition.
Abstract
Fluorescence analysis is a sensitive and selective method that provides abundant information and does not result in sample destruction. This technology is widely used in the detection of ...dissolved organic matter in the environment. Some challenges with fluorescence analysis are its higher sensitivity so that it is sensitive to background signals, the difficulty of extracting useful information, and the complexity and diversity of analytical methods. This review summarizes recent applications of fluorescence analysis in water research for the characterization of pollutants, evaluation of water treatment processes, and monitoring of emerging contaminants such as drugs, disinfection by-products, and toxicity. Two-dimensional fluorescence and excitation–emission matrix fluorescence analysis methods are discussed, along with their advantages and disadvantages, and application scope. Methods for sample processing, instrument calibration, and data analysis are proposed. This review is an important source of information for the application of fluorescence technology in water research such as the analysis of emerging contaminants.
•Hydrophilic and neutral fractions of organic matter are the most significant foulants.•Hydrophobic acids showed higher THMs formation reactivity than hydrophilic fractions.•Humic substances were ...efficiently broken-down by ozone or Fenton reactions.•Low molecular weight acids are not effectively removed by ozone.
The presence of organic matter (OM) in raw wastewater, treated wastewater effluents, and natural water samples has been known to cause many problems in wastewater treatment and water reclamation processes, such as treatability, membrane fouling, and the formation of potentially toxic by-products during wastewater treatment. This paper summarizes the current knowledge on the methods for characterization and quantification of OM in water samples in relation to wastewater and water treatment processes including: (i) characterization based on the biodegradability; (ii) characterization based on particle size distribution; (iii) fractionation based on the hydrophilic/hydrophobic properties; (iv) characterization based on the molecular weight (MW) size distribution; and (v) characterization based on fluorescence excitation emission matrix. In addition, the advantages, disadvantages and applications of these methods are discussed in detail. The establishment of correlations among biodegradability, hydrophobic/hydrophilic fractions, MW size distribution of OM, membrane fouling and formation of toxic by-products potential is highly recommended for further studies.
This work uncovers the implications of the estimation of exogenous inactivation rates for E. coli after the initial lag phase, and presents a strategy for the determination of the second-order ...inactivation rate constants (k2nd) of these bacteria with relevant transient species promoted by solar light in natural waters. For this purpose, specific precursors were considered (nitrate ion, rose bengal, anthraquinone-2-sulfonate) as well as the respective photo-generated transient species (i.e., hydroxyl radical (•OH), singlet oxygen (1O2) and triplet excited states). Under these conditions and by using suitable reference compounds (acesulfame K and 2,4,6-trimethylphenol in different series of experiments), the k2nd values were obtained after developing a proper competition kinetics methodology. The k2nd values were (2.5 ± 0.9) × 1011, (3.8 ± 1.6) × 107 and (1.8 ± 0.7) × 1010 M−1 s−1 for the inactivation of E. coli by •OH, 1O2 and the triplet state of anthraquinone-2-sulfonate (3AQ2S*), respectively. The measurement of a reaction rate constant that is higher than the diffusion-control limit for small molecules in aqueous solution implies that bacteria behave differently from molecules, e.g., because of the large size difference between bacteria and the transients. The obtained k2nd values were used for the modeling of the bacteria inactivation kinetics in outdoor systems (both water bodies and SODIS bottles), limited to the exponential decay phase that follows the initial lag time. Afterwards, the role of dissolved organic matter (DOM) as precursor of transient species for bacterial elimination was systematically studied. The interaction of different sunlight wavelength regions (UVB, UV-A, blue, green and yellow light) with Suwannee river (SW) and Nordic Lake organic matter (ND) was tested, and the photoinduced disinfection exerted by DOM isolates (SW DOM, Suwannee River Humic Acid, Suwannee River Fulvic Acid or Pony Lake Fulvic Acid) was compared. It was not possible to achieve a complete differentiation of the individual contributions of DOM triplet states (3DOM*) and 1O2 to bacterial inactivation. However, the application of competition kinetics to E. coli under solar irradiation in the presence of SW led to a k2nd value of (2.17 ± 0.40) × 1010 M−1 s−1, which is very near the value for inactivation by 3AQ2S* and suggests that the latter behaved very similar to SW-3DOM* and was a good 3DOM* proxy in the present case. The determination of the second-order inactivation rate constants of E. coli with •OH, 3DOM* and 1O2 represents a significant progress in the understanding of the external inactivation pathways of bacteria. It also allows predicting that, after the lag phase, 1O2 would contribute to photoinactivation to a far lesser extent than •OH and 3DOM*.
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•Exogenous inactivation rates for E. coli with transient species were established.•k2nd values were obtained using a proper competition kinetics methodology.•Modeling of the bacteria inactivation kinetics in outdoor systems was carried out.•3AQ2S* was a good 3DOM* proxy for the bacteria inactivation in water.•Source of DOM determines predominant action route of transient species on E. coli.
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