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Triplet-State Photochemistry of Dissolved Organic Matter: Triplet-State Energy Distribution and Surface Electric Charge Conditions
摘要： Excited triplet states of chromophoric dissolved organic matter (3CDOM*) are highly reactive species in sunlit surface waters and play a critical role in reactive oxygen species (ROS) formation and pollutant attenuation. In the present study, a series of chemical probes, including sorbic acid, sorbic alcohol, sorbic amine, trimethylphenol, and furfuryl alcohol, were employed to quantitatively determine 3CDOM* and 1O2 in various organic matters. Using a high concentration of sorbic alcohol as high-energy triplet states quencher, 3CDOM* can be first distinguished as high-energy triplet states (>250 kJ mol?1) and low-energy triplet states (<250 kJ mol?1). The terrestrial-origin natural organic matter (NOM) was found to mainly consist of low-energy triplet states, while high-energy triplet states were predominant in autochthonous-origin NOM and effluent/wastewater organic matter (EfOM/WWOM). The 1O2 quantum yields and electron transfer quantum yield coefficients (f TMP) generated from low-energy triplet states remained constant in all tested organic matters. External phenolic compound showed quenching effects on triplet-state formation and tended to have a higher quenching efficiency for aromatic ketone triplet states, which are the main high-energy triplet states. In comparison with terrestrial-origin NOM, autochthonous-origin NOM and EfOM/WWOM presented lower reaction rate constants for sorbic amines and higher reaction rate constants for sorbic acid, and these differences are likely due to dissimilar surface electric charge conditions. Understanding the triplet-state photochemistry of CDOM is essential for providing useful insights into their photochemical effects in aquatic systems.
关键词： surface charge,triplet-state photochemistry,energy distribution,dissolved organic matter,reactive oxygen species,chemical probes
更新于2025-11-19 16:56:35
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Preparation of high-purity α-Si3N4 nano-powder by precursor-carbothermal reduction and nitridation
摘要： This work investigated the role of natural organic matter (NOM) in the environmental processes of silver nanoparticles (AgNP) and the uptake and accumulation of AgNP in wheat. Different NOMs (Suwannee River humic acids [SRHA], fulvic acid [FA]) and Ag elements (Ag(0) and Ag+) were incubated in a hydroponic media for 15 days. The results showed that the NOM (10 mg C L-1) altered the dissolution, stabilization, uptake and accumulation of AgNP. The dissolution of AgNP declined in the presence of NOM. Compared with FA, the dissolved Ag+ decreased much more from 0.30 mg L-1 to 0.10 mg L-1 in the presence of SRHA. The fluorescence quenching results indicated that SRHA exhibited stronger binding to Ag+ than that of FA, and the quenching constants Ksv were 0.1309 (SRHA) and 0.0074 (FA), respectively. CeO, CeH, CeOeC, and MeeOH were involved in the interaction between NOM and AgNP. The NOM decreased the accumulated content of Ag in wheat. Hence, NOM alleviated the inhibition of AgNP to wheat growth. SRHA reduced the Ag content of wheat roots approximately 3-fold. These results clearly indicated the importance of NOM on altering the behavior, fate and toxicity of AgNP in an environment.
关键词： Wheat,Nanoparticle fate,Accumulation,Natural organic matter,Silver nanoparticle
更新于2025-11-19 16:46:39
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Linking optical and chemical signatures of dissolved organic matter in the southern Argentine shelf: Distribution and bioavailability
摘要： Fluorescence spectroscopy is commonly used to investigate the distribution and dynamics of dissolved organic matter (DOM) in marine systems. However, the direct comparison with chemical signatures is essential to substantiate the molecular composition of specific fluorescent components. Here we report the relation between optical and chemical signatures of DOM in waters of the Beagle Channel (BCW) (south-east of Tierra del Fuego, in the southern Argentine shelf) at the Pacific-Atlantic connection and neighboring coastal (CW) and oceanic (OW) waters (54.75-55.75°S, 64-68°W). The relationships among concentrations of total dissolved carbohydrates (TDCHO) and amino acids (TDAA), and fluorescent DOM (FDOM), including terrestrial “humic-like” (FDOMC) and “protein-like” compounds (FDOMT), and bioavailability of DOM components were assessed from field measurements acquired in the austral summer 2012. The maximal concentrations of TDCHO, dissolved organic carbon (DOC) and FDOMc intensities were found in BCW, while the minima in OW, displaying a negative correlation with salinity. This spatial distribution of biogeochemical signals suggests that humic compounds contributed by continental runoff contain refractory carbohydrates, and FDOMC resulted as a reliable tracer of carbon pathways in the Pacific-Atlantic connection. Conversely, TDAA and FDOMT showed the opposite distributional trend, with minimal concentrations in BCW and the maxima in CW and OW. The significant positive correlation of TDAA with salinity suggests open water sources of these components, however, phytoplankton biomass (Chla) in CW and OW was significantly lower than in BCW, ruling out the assumption of autochthonous source in open waters. TDAA were negatively correlated with the abundance of heterotrophic bacteria (HB), which displayed a consistent decrease from BCW towards OW, suggesting high bacterial uptake of TDAA in the BCW. This bacterial uptake is supported by the observed variation in carbon contribution of TDAA to DOC (amino acids carbon yield, in %), which is an indicator of DOM lability. The negative correlation found between amino acids carbon yield and HB abundance reflects intense bacterial activity in BCW, where phytoplankton biomass was maximum. Hence, higher DOM “freshness” occurs in the BCW, suggesting a tight coupling between microbial production and consumption.
关键词： Pacific-Atlantic connection.,amino acids,fluorescent dissolved organic matter,carbohydrates
更新于2025-11-14 15:26:12
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Effect of dissolved natural organic matter on the photocatalytic micropollutant removal performance of TiO2 nanotube array
摘要： The TiO2 nanotube array (TNA) is a promising photocatalyst for removal of micropollutants from water, but better understanding on its applicability in complex water matrices is still desired. Therefore this study investigates the effect of dissolved natural organic matter (NOMs) on 4-chloro-2-methylphenoxyacetic acid (MCPA, a typical micropollutant found in many water bodies) removal performance of TNA. The present study shows that although in bulk liquid phase NOMs would undergo photosensitization that can contribute to MCPA removal, the overall effect of NOMs on MCPA removal is detrimental due to the interaction between NOMs and the TNA surface: the total removal of MCPA decreased from 94.3% to 62.0% and 61.8%, in the presence of only 5 mg/L SWR-NOM and UMR-NOM respectively. Acidic pH was found to be able to mitigate the detrimental effect of NOMs (the total removal of MCPA was only decreased from 94.5% to 83.3% and 88.8% under acidic pH, in the presence of 15 mg/L SWR-NOM and UMR-NOM respectively), and the photosensitization effect of NOMs was strengthened; while under alkaline pH conditions the detrimental effect of NOMs completely vanished (the total removal of MCPA increased from 45.7% to 55.7% and 60.5% in the presence of 15 mg/L SWR-NOM and UMR-NOM respectively). Two commonly present co-existing anions, i.e. phosphate and bicarbonate, also mitigate the detrimental effect of NOMs. With 15 mg/L SWR-NOM: the presence of 100 mg/L bicarbonate increased the total removal of MCPA from 49.1% to 65.1%; the presence of 100 mg/L phosphate increased the total removal of MCPA from 49.1% to 62.5%. With 15 mg/L SWR-NOM, the presence of 100 mg/L bicarbonate increased the total removal of MCPA from 45.2% to 56.1%; the presence of 100 mg/L phosphate increased the total removal of MCPA from 45.2% to 62.9%. The photocurrent measurement support that the presence of such anions greatly suppresses the h + scavenging effect of NOMs; while other anions, i.e. chloride, nitrate, sulfate, showed no notable effect.
关键词： Micropollutant,MCPA,TiO2 nanotube array,Photocatalysis,Natural organic matter
更新于2025-09-23 15:23:52
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Dynamics of dissolved organic matter in a wastewater effluent-impacted Japanese urban stream: characteristics, occurrence and photoreactivity of fluorescent components
摘要： We report the results of using the excitation–emission matrix (EEM) method combined with parallel factor analysis (PARAFAC) to investigate the characteristics and occurrence of dissolved organic matter (DOM) in an urban stream impacted by effluent from a wastewater treatment plant (WWTP). The PARAFAC model divides the bulk EEM spectra into six individual fluorescent components with three humic-like components (C1–C3), two protein-like components (C4 and C5) and a wastewater-derived component (C6). In general, intensities of fluorescent components are abundant in WWTP effluent impacted samples, thus showing that such an effluent is a major source of DOM in urban rivers, but C5 is considered to have autochthonous sources within the stream. In areas where the effluent is released, the fluorescent intensity from components (except C5) gradually decreases as these components are transported downstream. However, concentrations of dissolved organic carbon remain almost constant downstream of the release area. These results would be attributed to degradation and/or modification of fluorophore. Photolysis experiments confirmed that fluorescent intensities can decrease with increase of irradiation times. C6 particularly showed a rapid photodegradation, remaining only 24.1% after 48 h photolysis. These findings would be important when assessing DOM source and water quality in aquatic environments by EEM-PARAFAC.
关键词： dissolved organic matter,excitation–emission matrix,urban river,photochemical reaction
更新于2025-09-23 15:22:29
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Organic matter and sand estimates by spectroradiometry: Strategies for the development of models with applicability at a local scale
摘要： The development of spectral prediction models for soil attributes has been extensively studied in the last 10 years. However, one of the problems encountered during this period concerns the representativeness of the samples selected for model generation, which are often unable to capture the existing variability in agricultural areas, generating imprecise models. Thus, it is necessary to establish strategies for selecting soil samples, as well as for making them more representative within the model. Considering this, the aim of the present study was to evaluate strategies for soil sample selection and the recalibration of large models using samples from a smaller area, in a process called spiking, and its effect on soil attribute estimations. A total of 425 soil samples were used for the generation of the state models, as well as 200 soil samples from a target site for attribute recalibration and prediction. From these 200 samples, 10 (subset) were selected by different methods for state model recalibration (spiking), and 190 were used in the prediction. Another 5 and 10 copies of the subsets were also used as extra-weight to recalibrate the models. Models spiked with samples located in the center of the spectral space associated with extra-weight (10 copies) showed better accuracy in sand prediction (RPD = 2.20; r2 = 0.80; RMSEP = 71.6 g kg?1). For organic matter, the use of selected samples based on 5 clusters associated with extra-weight (10 copies) slightly improved the RMSEP and RPD in most cases, reaching a maximum value of 6.1 g dm?3 and 1.20, respectively. However, the subsets selected at the target site were not able to indicate the entire variability of the local samples concerning organic matter, damaging the expansion of the recalibrated state models.
关键词： Spiking,Organic matter,Spectroradiometry,Sand
更新于2025-09-23 15:22:29
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From micro to macro-contaminants: The impact of low-energy titanium dioxide photocatalysis followed by filtration on the mitigation of drinking water organics
摘要： This study evaluated strategies targeting macro- and micro-organic contaminant mitigation using low-energy titanium dioxide photocatalysis. Energy inputs of 1, 2, and 5 kWh m-3 resulted in incomplete oxidation of macro-organic natural organic matter, signified by greater reductions of UV254 and specific ultraviolet UV absorbance (SUVA) in comparison to dissolved organic carbon (DOC). The rate of UV254 removal was 3 orders of magnitude greater than the rate of DOC degradation. Incomplete oxidation improved operation of downstream filtration processes. Photocatalysis at 2 kWh m-3 increased the bed life of downstream granular activated carbon (GAC) filter by 340% relative to direct filtration pretreatment. Likewise, photocatalysis operated ahead of microfiltration decreased fouling, resulting in longer filter run times. Using 2 kWh m-3 photocatalysis increased filter run time by 36 times in comparison to direct filtration. Furthermore, levels of DOC and UV254 in the membrane permeate improved (with no change in removal across the membrane) using low-energy photocatalysis pretreatments. While high-energy UV inputs provided high levels of removal of the estrogenic micro-organics estrone (E1), 17β-estradiol (E2), estriol (E3), and 17α-ethynlestradiol (EE2), low-energy photocatalysis did not enhance removal of estrogens beyond levels achieved by photolysis alone. In the cases of E1 and E3, the addition of TiO2 as a photocatalyst reduced degradation rates of estrogens compared to UV photolysis. Overall, process electrical energy per order magnitude reductions (EEOs) greatly improved using photocatalysis, versus photolysis, for the macro-organics DOC, UV254, and SUVA; however, energy required for removal of estrogens was similar between photolysis and photocatalysis.
关键词： granular activated carbon (GAC),estrogens,UV photolysis,dissolved organic carbon (DOC),advanced oxidation process (AOP),natural organic matter (NOM)
更新于2025-09-23 15:21:01
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The application of proximal visible and near-infrared spectroscopy to estimate soil organic matter on the Triffa Plain of Morocco
摘要： Soil organic matter (SOM) is a fundamental soil constituent. The estimation of this parameter in the laboratory using the classical method is complex time-consuming and requires the use of chemical reagents. The objectives of this study were to assess the accuracy of two laboratory measurement setups of the VIS-NIR spectroscopy in estimating SOM content and determine the important spectral bands in the SOM estimation model. A total of 115 soil samples were collected from the non-root zone (0-20 cm) of soil in the study area of the Triffa Plain and then analysed for SOM in the laboratory by the Walkley–Black method. The reflectance spectra of soil samples were measured by two protocols, Contact Probe (CP) and Pistol Grip (PG)) of the ASD spectroradiometer (350-2500 nm) in the laboratory. Partial least squares regression (PLSR) was used to develop the prediction models. The results of coefficient of determination (R2) and the root mean square error (RMSE) showed that the pistol grip offers reasonable accuracy with an R2 = 0.93 and RMSE = 0.13 compared to the contact probe protocol with an R2 = 0.85 and RMSE = 0.19. The near-Infrared range were more accurate than those in the visible range for predicting SOM using the both setups (CP and PG). The significant wavelengths contributing to the prediction of SOM for (PG) setup were at: 424, 597, 1432, 1484, 1830 ,1920, 2200, 2357 and 2430 nm, while were at 433, 587, 1380, 1431, 1929, 2200 and 2345 nm for (CP) setup.
关键词： soil organic matter,SOM analysis.,VIS-NIR spectroscopy,reflectance spectra,SOM estimation
更新于2025-09-23 15:21:01
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Fluorescence spectroscopy of ancient sedimentary organic matter via confocal laser scanning microscopy (CLSM)
摘要： Fluorescence spectroscopy via confocal laser scanning microscopy (CLSM) was used to analyze ancient sedimentary organic matter, including Tasmanites microfossils in Devonian shale and Gloeocapsomorpha prisca (G. prisca) in Ordovician kukersite from North American basins. We examined fluorescence emission as a function of excitation laser wavelength, sample orientation, and with respect to location within individual organic entities and in transects across bedded organic matter. Results from spectral scans of the same field of view in Tasmanites with different laser lines showed progressive red-shift in emission maxima with longer excitation wavelengths. This result indicates steady-state Tasmanites fluorescence emission is an overlapping combination of emission from multiple fluorophore functions. Stokes shift decreased with increasing excitation wavelength, further suggesting the presence of multiple fluorophore functions with different S1 → S0 transition energies. This observation also indicates that at longer excitation wavelengths, less absorbed light energy is dissipated via collisional transfer than at shorter excitation wavelengths and may suggest fewer polar functions are preferentially absorbing. Confirming earlier results, emission spectra observed from high fluorescence intensity regions (fold apices) in individual Tasmanites are blue-shifted relative to emission from other locations in the same microfossil. We suggest high intensity emission is from photoselective alignment of polarized excitation with the fluorophore absorption and emission transition moment. The blue shift observed in regions of high intensity emission may be due to relative absence or realignment of polar species, e.g., bridging ether or ester functions, although variations in O abundance could not be confirmed with preliminary time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis. Tasmanites occurring in consolidated sediments are flattened from original spherical morphology and, in optical microscopy, this burial deformation results in generally parallel extinction (strain-influenced) and positive elongation. The deformation also induces fluorescence anisotropy observed as variations in emission wavelength when individual Tasmanites are measured from their long axis parallel to bedding, whereas this effect is absent in bedding-normal view. Transects from G. prisca-rich source layers into adjacent reservoir layers show decrease in fluorescence intensity and spectral red-shift (increase in full-width half-maximum with increasing red portion of the half-width). These results may suggest an increase in fluorescence quenching across the source-to-reservoir transition zone, consistent with an increase in aromaticity following petroleum expulsion and migration. These observations are supported by increasing reflectance values measured across similar micro-scale transects. Our results highlight the applicability of CLSM as a broad and under-utilized approach for the characterization of sedimentary organic matter and are discussed with perspective toward petroleum processes and thermal indices research.
关键词： Gloeocapsomorpha prisca,Confocal laser scanning microscopy,Tasmanites,Petroleum processes,Fluorescence spectroscopy,Sedimentary organic matter,Thermal indices
更新于2025-09-23 15:21:01
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Impact of Contrasted Weather Conditions on CDOM Absorption/Fluorescence and Biogeochemistry in the Eastern Lagoon of New Caledonia
摘要： New Caledonia (Southwest Pacific), like all tropical Pacific Island countries, is impacted by weather events, climate change, and local anthropogenic forcing. Strong erosion of particles and dissolved organic matter (DOM) from ultramafic rocks, associated with trace metals dissemination (i.e., nickel, manganese and cobalt), potentially affects lagoon waters and coral reefs surrounding the main island. The CALIOPE (CALedonian Inherent Optical PropErties) cruises were performed along the Eastern Lagoon of New Caledonia (ELNC) (400 km, 13 transects from Bay to open ocean, 51 stations) during contrasted meteorological conditions: a dry period (October 2011), a windy situation (March 2014), and a strong rainy event (March 2016). CDOM absorption and fluorescence (FDOM), particulate absorption, backscattering, suspended particulate matter (SPM), total chlorophyll a (TChla), nutrients (NOx), pigment and phytoplankton composition were measured. Among the four CDOM fluorophores, the humic-like component (λEx/λEm: 235/460 nm), assimilated to a photoproduct of terrestrial organic matter, had relatively low fluorescence compared to protein-like fluorophores. As CDOM absorption, particulate absorption, backscattering, SPM, total chlorophyll a (TChla) and nutrient (NOx) concentrations, this humic-like material generally showed the highest values during rainfall events, the latter inducing an increase in riverine terrigeneous inputs and change toward higher phytoplankton size classes. The tyrosine 1-like (λEx/λEm: 220, 275/304 nm) and tryptophan-like fluorophores (λEx/λEm: 230, 300/352 nm) were strongly influenced by wind displaying a 7-fold and 3-fold increase, respectively in windy situation compared to calm conditions. These increases could be related to enhancements of autochthonous biological activities (highest mean concentrations of Synechococcus spp., phycoerythrin, pico- and nano-eukaryotes, heterotrophic bacteria and nanoplankton observed in wind condition) through the inputs of organic and mineral materials issued from the wind-induced sediment resuspension, atmospheric deposition and water mass mixing. By contrast, the tyrosine 2-like fluorophore (λEx/λEm: 245, 275/304 nm) substantially increased during rain events and presented the lowest values in wind conditions. These strong increases may be linked to the stimulation of planktonic activities due to riverine inputs. Therefore, this study emphasizes the significant differential influence of weather conditions (calm/wind/rain) on biogeochemistry and CDOM/FDOM distributions in the ELNC.
关键词： rivers,phytoplankton,New Caledonia,fluorescence,chromophoric dissolved organic matter,bio-optics,lagoons,Tropical Pacific
更新于2025-09-23 15:21:01