Tryptophan-like Component Research Articles

Novel insights into variation of dissolved organic matter during textile wastewater treatment by fluorescence excitation emission matrix

In this work, the textile wastewater samples along two full-scale treatment trains (‘biological + oxidative’ process) were characterized by fluorescence excitation emission matrix (EEM). Four fluorescent components (C1–C4) were identified by parallel factor (PARAFAC) analysis. The polarity and apparent molecular weight (MW) of C1–C4 were investigated by high performance liquid chromatography (HPLC). By comparison of EEM spectra and HPLC chromatograms, the tyrosine-like component (C1) and the tryptophan-like components (C2 and C3) were related to Dispersant MF. Component C4 with two emission peaks suggested the formation of an intramolecular exciplex. Despite the remarkable difference of untreated textile wastewater, the polarity and apparent MW of C1–C4 as well as their variations along the treatment trains were highly similar between different wastewater treatment plants. The weights distribution of Dispersant MF among C1–C4 indicates its dominance in the protein-like fluorescence of textile wastewater. Component C1–C4 had different fate in various treatment stages. C1–C4 were poorly removed (<25%) during the anaerobic or anoxic process. A better removal efficiency of C3 (65%–80%) than C1, C2 and C4 (15%–50%) was achieved in the aerobic process. Both Fenton and chlorination process could significantly decrease the concentrations of C1–C4 (70%–100%). The concentration of C2 was strongly correlated with dissolved organic carbon (DOC), chemical oxygen demand (COD) and UV absorbance at 254 nm (UVA254). The fluorescence of C2 could be proposed as an indicator of COD and a supplement to UVA254 to evaluate treatment efficiency of textile wastewater. The results provide a better understanding of DOM variation of textile wastewater during treatment.

Characterizing spatiotemporal variations of chromophoric dissolved organic matter in headwater catchment of a key drinking water source in China.

Natural surface drinking water sources with the increasing chromophoric dissolved organic matter (CDOM) have profound influences on the aquatic environment and drinking water safety. Here, this study investigated the spatiotemporal variations of CDOM in Fengshuba Reservoir and its catchments in China. Twenty-four surface water samples, 45 water samples (including surface water, middle water, and bottom water), and 15 pore water samples were collected from rivers, reservoir, and sediment of the reservoir, respectively. Then, three fluorescent components, namely two humic-like components (C1 and C2) and a tryptophan-like component (C3), were identified from the excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) for all samples. For spatial distributions, the levels of CDOM and two humic-like components in the reservoir were significantly lower than those in the upstream rivers (p<0.01), indicating that the reservoir may act as a reactor to partly reduce the levels of exogenous input including CDOM and humic-like matters from the surrounding catchment. For temporal variations, the mean levels of CDOM and three fluorescent components did not significantly change in rivers, suggesting that perennial anthropic activity maybe an important factor impacting the concentration and composition of river CDOM but not the precipitation and runoff. However, these mean values of CDOM for the bulk waters of the reservoir changed markedly along with seasonal variations, indicating that the hydrological processes in the reservoir could control the quality and quantity of CDOM. The different correlations between the fluorescent components and primary water parameters in the river, reservoir, and pore water samples further suggest that the reservoir is an important factor regulating the migration and transformation of FDOM along with the variations of different environmental gradients.

Characteristics of dissolved organic nitrogen in overlying water of typical lakes of Yunnan Plateau, China

In this study, Ultraviolet–visible spectroscopy (UV/Vis) and excitation-emission matrix fluorescence combined with parallel factor analysis (the EEM-PARAFAC model) were used for the characterization of the components and structure of the dissolved organic nitrogen (DON) in the overlying water of three typical lakes from Yunnan Plateau, China. Four distinct components of Erhai Lake, three components of Chenghai Lake, and three components of Lugu Lake were identified by the PARAFAC model, based on fluorescence excitation-emission spectra. These included two terrestrial and marine humic-like components (E1 and E3) for Erhai Lake, one terrestrial and marine humic-like component (C1) for Chenghai Lake, and one autochthonous tryptophan-like component (L1) for Lugu Lake. The autochthonous tryptophan-like component S1 (E4, C2, and L3) and autochthonous tyrosine-like component S2 (E2, C3, and L2) were also identified. In addition, the S1 and S2 components were highly similar to one another and had almost identical extraction and emission wavelengths. Both S1 and S2 components were highly prevalent in plateau lakes but rarely appeared in plain lakes. Principal component analysis (PCA) found a great correlation between the S1 and S2 components in all studied lakes, indicating that they had a common source or the same variation trend. To be noted, we found that with the decrease of eutrophication level, relative abundance of S1 and S2 presented significance increase, the relative abundance of S1 and S2 components can be used as an indicator of lake trophic status in the Yunnan Plateau. Special attention should be given to these components with regard to plateau lake protection. PCA score analysis for the studied lakes found obvious quantitative and qualitative differences in the fluorescence components of different regions of Chenghai Lake. No significant discrepancy was found between Erhai Lake regions.

Characterisation of landfill leachate by EEM-PARAFAC-SOM during physical-chemical treatment by coagulation-flocculation, activated carbon adsorption and ion exchange

The combination of fluorescence excitation-emission matrices (EEM), parallel factor analysis (PARAFAC) and self-organizing maps (SOM) is shown to be a powerful tool in the follow up of dissolved organic matter (DOM) removal from landfill leachate by physical-chemical treatment consisting of coagulation, granular activated carbon (GAC) and ion exchange. Using PARAFAC, three DOM components were identified: C1 representing humic/fulvic-like compounds; C2 representing tryptophan-like compounds; and C3 representing humic-like compounds. Coagulation with ferric chloride (FeCl3) at a dose of 7 g/L reduced the maximum fluorescence of C1, C2 and C3 by 52%, 17% and 15% respectively, while polyaluminium chloride (PACl) reduced C1 only by 7% at the same dose. DOM removal during GAC and ion exchange treatment of raw and coagulated leachate exhibited different profiles. At less than 2 bed volumes (BV) of treatment, the humic components C1 and C3 were rapidly removed, whereas at BV ≥ 2 the tryptophan-like component C2 was preferentially removed. Overall, leachate treated with coagulation +10.6 BV GAC +10.6 BV ion exchange showed the highest removal of C1 (39% - FeCl3, 8% - PACl), C2 (74% - FeCl3, 68% - PACl) and no C3 removal; whereas only 52% C2 and no C1 and C3 removal was observed in raw leachate treated with 10.6 BV GAC + 10.6 BV ion exchange only. Analysis of PARAFAC-derived components with SOM revealed that coagulation, GAC and ion exchange can treat leachate at least 50% longer than only GAC and ion exchange before the fluorescence composition of leachate remains unchanged.

Investigating variations of fluorescent dissolved organic matter in wastewater treatment using synchronous fluorescence spectroscopy combined with principal component analysis and two-dimensional correlation

ABSTRACTSynchronous fluorescence spectroscopy (SFS) combined with principal component analysis (PCA) and two-dimensional (2D) correlation was applied to investigate removal efficiencies and variations of dissolved organic matter (DOM) fractions in the wastewater treatment plant (WWTP) with an A2O craft. A decreasing order of total removal efficiencies was tyrosine-like fluorescence component (89.58%) > humic-like fluorescence (HLF) component (39.83%) > tryptophan-like fluorescence component (36.89%) > microbial humic-like fluorescence (HLF) component (12.47%) > fulvic-like fluorescence component (6.37%). The tyrosine-like, tryptophan-like and HLF components were deeply decomposed by anaerobic bacteria in the anaerobic zone. The tyrosine-like component was the preponderant fraction of DOM in the raw water and primary sediment tank. The tyrosine-like component was the dominant component of DOM too in the anaerobic and anoxic zones, but its proportion was slightly more than the tryptophan-like component. The tryptophan-like component was the dominant component in the facultative zone, the oxic zone and the secondary sediment tank. Based on the changing band order of 279 → 304 → 490 → 330 → 380 → 430 nm, the decreasing variation order was tyrosine-like > tryptophan-like > humic-like > microbial humic-like > fulvic-like component. Therefore, the SFS combined with PCA and 2D correlation is an effective tool for not only monitoring the removal of DOM components but also characterizing variations of DOM fractions in the WWTP.

Mixing behavior and photobleaching of chromophoric dissolved organic matter in the Changjiang River estuary and the adjacent East China Sea

The distribution and chemical properties of chromophoric dissolved organic matter (CDOM) in the Changjiang River estuary and the adjacent ECS were determined in February and July 2014. CDOM concentration (aCDOM(355)) decreased along the salinity gradient, indicating that terrestrial input significantly influenced CDOM in the study area. The runoff from the Changjiang River with smaller spectral slope ratios (SR) dominated SR variability in our study area in July, and the photodegradation of allochthonous CDOM increased SR in the open sea in February. CDOM excitation/emission matrix spectra subjected to parallel factor analysis identified four components: terrestrial humic-like component (C1), autochthonous protein-like components (C2 and C4), and terrestrial tryptophan-like component (C3). C1 and C3 showed a conservative mixing behavior, whereas C2 and C4 were appeared to be influenced by chlorophyll-a (Chl-a). Our sunlight exposure experiment showed that aCDOM(355) (42% at station C1 and 16% at station A6-8) decreased and SR (27% at station C1 and 9.2% at station A6-8) increased. These findings suggested that CDOM molecules were photochemically degraded from high-molecular weight dissolved organic matter (DOM) into low-molecular weight organic substances. The fluorescence intensities of terrestrially derived C1 and C3 decreased with prolonged illumination in samples from both sites. However, autochthonous C2 and C4 moderately increased after they were exposed to sunlight. Results of this study demonstrated that terrestrially derived DOM was more susceptible to irradiation than autochthonous DOM.

PARAFAC Modeling of Irradiation- and Oxidation-Induced Changes in Fluorescent Dissolved Organic Matter Extracted from Poultry Litter.

Parallel factor analysis (PARAFAC) applied to fluorescence excitation emission matrices (EEMs) allows quantitative assessment of the composition of fluorescent dissolved organic matter (DOM). In this study, we fit a four-component EEM-PARAFAC model to characterize DOM extracted from poultry litter. The data set included fluorescence EEMs from 291 untreated, irradiated (253.7 nm, 310-410 nm), and oxidized (UV-H2O2, ozone) poultry litter extracts. The four components were identified as microbial humic-, terrestrial humic-, tyrosine-, and tryptophan-like fluorescent signatures. The Tucker's congruence coefficients for components from the global (i.e., aggregated sample set) model and local (i.e., single poultry litter source) models were greater than 0.99, suggesting that the global EEM-PARAFAC model may be suitable to study poultry litter DOM from individual sources. In general, the transformation trends of the four fluorescence components were comparable for all poultry litter sources tested. For irradiation at 253.7 nm, ozonation, and UV-H2O2 advanced oxidation, transformation of the humic-like components was slower than that of the tryptophan-like component. The opposite trend was observed for irradiation at 310-410 nm, due to differences in UV absorbance properties of components. Compared to the other EEM-PARAFAC components, the tyrosine-like component was fairly recalcitrant in irradiation and oxidation processes. This novel application of EEM-PARAFAC modeling provides insight into the composition and fate of agricultural DOM in natural and engineered systems.

Evaluation of CDOM sources and their links with water quality in the lakes of Northeast China using fluorescence spectroscopy

The spatial distributions of the fluorescence intensities Fmax for chromophoric dissolved organic matter (CDOM) components, the fluorescence indices (FI370 and FI310) and their correlations with water quality of 19 lakes in the Songhua River Basin (SHRB) across semiarid regions of Northeast China were examined with the data collected in September 2012 and 2015. The 19 lakes were divided into two groups according to EC (threshold value=800µScm−1): fresh water (N=13) and brackish water lakes (N=6). The fluorescent characteristics of CDOM in the 19 lakes were investigated using excitation-emission matrix fluorescence spectroscopy (EEM) coupled with parallel factor (PARAFAC) and multivariate analysis. Two humic-like components (C1 and C3), one tryptophan-like component (C2), and one tyrosine-like component (C4) were identified by PARAFAC. The component C4 was not included in subsequent analyses due to the strong scatter in some colloidal water samples from brackish water lakes. The correlations between Fmax for the three EEM-PARAFAC extracted CDOM components C1–C3, the fluorescence indices (FI370 and FI310) and the water quality parameters (i.e., TN, TP, Chl-a, pH, EC, turbidity (Turb) and dissolved organic carbon (DOC)) were determined by redundancy analysis (RDA). The results of RDA analysis showed that spatial variation in land cover, pollution sources, and salinity/EC gradients in water quality affected Fmax for the fluorescent components C1–C3 and the fluorescence indices (FI370 and FI310). Further examination indicated that the CDOM fluorescent components and the fluorescence indices (FI370 and FI310) did not significantly differ (t-test, p>0.05) in fresh water (N=13) and brackish water lakes (N=6). There was a difference in the distribution of the average Fmax for the CDOM fluorescent components between C1 to C3 from agricultural sources and urban wastewater sources in hypereutrophic brackish water lakes. The Fmax for humic-like components C1 and C3 spatially varied with land cover among the 19 lakes. Our results indicated that the spatial distributions of Fmax for CDOM fluorescent components and their correlations with water quality can be evaluated by EEM-PARAFAC and multivariate analysis among the 19 lakes across semiarid regions of Northeast China, which has potential implication for lakes with similar genesis.

Identification and PAC Adsorption of Foulants Responsible for Irreversible Fouling During Ultrafiltration of Dongjiang River Water

Foulants responsible for hydraulic irreversible fouling in Dongjiang River water were identified by ultrafiltration process and their removal by powdered activated carbon (PAC) adsorption treatment was investigated using fluorescent excitation emission matrix and parallel factor analysis (EEM-PARAFAC). A correlation analysis was then carried out for samples between the maximum fluorescence intensities (Fmax) of three PARAFAC components after PAC adsorption and the surface properties of corresponding PAC samples. The results showed that two humic-like (C1 and C3) and one tryptophan-like fluorescent components were obtained through PARAFAC analysis, in which tryptophan-like component C2 was found to be the main substance in hydraulic irreversible foulants extracted from fouled membrane. Furthermore, the results of correlation analysis suggested that microspore area of PAC correlated with PAC adsorption of tryptophan-like fluorescent components, which played an important role in irreversible fouling. Both BET and mesopore+macropore area of PAC correlated with its adsorption of humic-like fluorescent components. The result provided support for selecting PAC in PAC-ultrafiltration hybrid process, which would be more effective for fouling control.

New insights into the source of decadal increase in chemical oxygen demand associated with dissolved organic carbon in Dianchi Lake

Dissolved organic carbon (DOC) can be used an alternative index of water quality instead of chemical oxygen demand (COD) to reflect the organic pollution in water. The monitoring data of water quality in a long-term (1990–2013) from Dianchi Lake confirmed the increase trend of COD concentration in the lake since 2007. The similarities and differences in the DOC components between the lake and its sources and the contribution from allochthonous and autochthonous DOC to the total DOC in this lake were determined to elucidate the reason of COD increase based on C/N atomic ratios, stable isotope abundance of carbon and nitrogen, UV–visible spectroscopy, three-dimensional excitation–emission matrix (3DEEM) fluorescence spectroscopy. The terrigenous organic matter showed humic-like fluorescence, and the autochthonous organic matter showed tryptophan-like components. Agricultural runoff (9.5%), leaf litter (7.5%) and urban runoff (13.2%) were the main sources of DOC in the lake. Sewage tail was a major source of organic materials, 3DEEM for the indicates that sewage tail DOC composition did not change markedly over the biodegradation period, indicating that sewage tail contains a high load of DOC that is resistant to further biodegradation and subsequently accumulates in the lake. The change of land use in the catchment and the increase of sewage tail load into the lake are the key factors for the increase in COD concentration in Dianchi Lake. Thus, the lake should be protected by controlling the pollution from the urban nonpoint sources and refractory composition in point sources.

Dynamic changes of dissolved organic matter in membrane bioreactors at different organic loading rates: Evidence from spectroscopic and chromatographic methods

Excitation emission matrix-parallel factor analysis (EEM-PARAFAC) and size exclusion chromatography (SEC) were utilized to explore the dynamics in extracellular polymeric substances (EPS), soluble microbial products (SMP), and effluent for the membrane bioreactors at two different organic loading rates (OLRs). Combination of three different fluorescent components explained the compositional changes of dissolved organic matter. The lower OLR resulted in a higher production of tryptophan-like component (C1) in EPS, while the opposite trends were found for the other two components (humic-like C2 and tyrosine-like C3), signifying the role of C1 in the endogenous condition. Larger sized molecules were more greatly produced in EPS at the lower OLR. Meanwhile, all the size fractions of SMP were more abundant at the higher OLR particular for the early phase of the operation. Irrespective of the OLR, the higher degrees of the membrane retention were found for relatively large sized and protein-like molecules.

Spatio-temporal variability of fluorescent dissolved organic matter in the Rhône River delta and the Fos-Marseille marine area (NW Mediterranean Sea, France).

The spatio-temporal variability of fluorescent dissolved organic matter (FDOM) and its relationships with physical (temperature, salinity) and chemical (nutrients, chlorophyll a, dissolved and particulate organic carbon, nitrogen and phosphorus) parameters were investigated in inland waters of the Rhône River delta and the Fos-Marseille marine area (northwestern Mediterranean, France). Samples were taken approximately twice per month in two inland sites and three marine sites from February 2011 to January 2012. FDOM was analysed using fluorescence excitation-emission matrices (EEMs) coupled with parallel factor analysis (PARAFAC). In inland waters, humic-like components C1 (λEx/λEm: 250 (330)/394nm) and C3 (λEx/λEm: 250 (350)/454nm) dominated over one tryptophan-like component C2 (λEx/λEm: 230 (280)/340nm), reflecting a background contribution of terrigenous material (~67% of total fluorescence intensity, in quinine sulphate unit (QSU)) throughout the year. In marine waters, protein-like material, with tyrosine-like C4 (λEx/λEm: <220 (275)/<300nm) and tryptophan-like C5 (λEx/λEm: 230 (280)/342nm), dominated (~71% of total fluorescence intensity, in QSU) over a single humic-like component C6 (λEx/λEm: 245 (300)/450nm). In inland waters of the Rhône River delta, humic-like components C1 and C3 were more abundant in autumn-winter, very likely due to inputs of terrestrial organic matter from rainfalls, runoffs and wind-induced sediment resuspension. In marine sites, intrusions of the Berre Lagoon and Rhône River waters had a significant impact on the local biogeochemistry, leading to higher fluorescence intensities of humic- and protein-like components in spring-summer. On average, the fluorescence intensities of FDOM components C4, C5 and C6 increased by 33-81% under lower salinity. This work highlights the complex dynamics of FDOM in coastal waters and confirms the link between marine FDOM and the Rhône River freshwater intrusions on larger spatial and temporal scales in the Fos-Marseille marine area.

Accumulation of humic-like and proteinaceous dissolved organic matter in zero-discharge aquaculture systems as revealed by fluorescence EEM spectroscopy

Recirculating aquaculture systems (RAS), offering many economic and fish husbandry benefits, are characterized by an accumulation of dissolved organic matter (DOM) and, specifically, humic substances (HS). As reported in a number of studies, HS may affect biological activity in both invertebrates and vertebrates. Given the accumulation of HS in RAS, it is therefore of great interest to characterize DOM and, specifically, its HS fraction in the RAS. The present study was aimed at characterizing long-term changes in fluorescent DOM composition in the culture water of RAS systems, which were operated in a novel, zero water exchange mode. Two such zero-discharge recirculating systems (ZDS) were examined: a freshwater system, stocked with hybrid tilapia (Oreochromis aureus x Oreochromis niloticus) and a marine system, stocked with gilthead seabream (Sparus aurata). Excitation-emission matrices (EEMs) of fluorescence, coupled with parallel factor analysis (PARAFAC), were used to characterize and quantify the different DOM components in the ZDS. In the culture water, one tryptophan-like and four HS-like components were identified. The fluorescence intensities of three of the HS-like components as well as the tryptophan-like component increased at comparable rates during ZDS operation while a much slower accumulation of these compounds was observed in a parallel operated, flow-through, freshwater aquarium. The ZDS examined in this study comprised a sludge digestion stage where a considerable accumulation of all fluorescent components was detected. A HS-like components and a tryptophan-like component in blood of tilapia from the freshwater ZDS were similar to components found in the culture water. Blood levels of both components were higher in fish cultured in the DOM-rich ZDS than in fish raised in the control, flow-through freshwater aquarium. Fluorescence of the HS-like component found in the fish blood increased also with time of ZDS operation. The finding that fish blood contains a HS-like fluorescent component may have important implications for the understanding of the physiological effects of HS in fish and the possible benefits of these substances in aquaculture.

Synchronous fluorescence spectroscopy combined with two-dimensional correlation and principle component analysis to characterize dissolved organic matter in an urban river.

Synchronous fluorescence spectroscopy (SFS) combined with two-dimensional correlation and principle component analysis (PCA) can provide an excellent challenge to capture fluorescent components of dissolved organic matter (DOM) and reveal its spatial variations in an urban river. Water samples were collected from Baitapuhe River along human impact gradient, i.e., the rural, town, and urban regions. DOM in Baitapuhe River was composed of protein-like, microbial humic-like, fulvic-like, and humic-like fluorescent components. The protein-like was the dominant component, which consisted of tyrosine-like and tryptophan-like components. In the rural region, the variation of the microbial humic-like was higher than that of the protein-like according to the band changing order of 335→281nm, and both components changed in the same direction. In the town region, the variation of the microbial humic-like was the highest followed by the protein-like and fulvic-like on the basis of the changing band order of 335→281→369nm, and these components varied in the same trend too. In the urban region, the variation of the protein-like was the highest, followed by the microbial humic-like, fulvic-like, and humic-like based on the changing band order of 282→335→369→470nm, and the protein-like variation was opposite to the other components. The SFS combined with PCA and two-dimensional correlation can be used as a powerful tool in investigating fluorescent components of DOM and revealing spatial variations of these fluorescent components.

Interactions of metal oxide nanoparticles with extracellular polymeric substances (EPS) of algal aggregates in an eutrophic ecosystem

Nanoparticle binding with organic ligands in natural waters is important to understand their environmental behavior and fate. In this study, the interaction of two metal oxide nanoparticles (nano-CuO and nano-Fe3O4) with extracellular polymeric substances (EPS) from algal aggregates was studied through using fluorescence emission-excitation matrix (EEM) quenching titration combined with parallel factor (PARAFAC) analysis. Spectroscopy analysis detected two protein-like peaks in the loosely bound EPS (LB–EPS) fraction, while both protein-, fulvic- and humic-like peaks can be found in the tightly bound EPS (TB–EPS) fraction. PARAFAC analysis identified three independent fluorescence components, including one tryptophan-, one tyrosine- and one humic-like component, from 68 original EEM spectra. A quenching experiment showed that humic-like components in the TB–EPS fraction exhibited higher nanoparticle binding capacities (logKM>6.23) than that in the LB–EPS fraction (logKM: <5.72), while tryptophan-like components were characterized with a high nano-CuO affinity in the LB–EPS fraction (logKM: 5.66). Further analysis revealed that the LB–EPS fraction was responsible for the transportation of nano-CuO (logKM>5.66), while the mobility of nano-Fe3O4 would be influenced by organic ligands in the TB–EPS fraction (logKM>6.28). Based on the results, the toxicity of nanoparticles in the eutrophic waters would be higher than those in the oligotrophic ecosystems. This study facilitates a deeper understanding of the environmental behavior and fate of metal oxide nanoparticles in eutrophic aquatic ecosystems.

Characterization of Dissolved Organic Matter from Effluents in a Dry Anaerobic Digestion Process Using Spectroscopic Techniques and Multivariate Statistical Analysis

Dissolved organic matter (DOM) collected from a garage-type dry fermentation system was investigated using UV–Vis absorption and fluorescence spectroscopy. Spectral parameters A253/203, biological index and fluorescence index were used to assess the structural characteristics and sources of effluent DOM. The results showed that aromatic rings highly substituted with hydroxyl, carbonyl, ester and carboxylic groups were obtained in the aerobic decomposition stage, and microbially derived organic matter dominated in the dry anaerobic digestion process, suggesting that the hydrolysis of organic macromolecules (lignin) in the aerobic decomposition resulted in the formation of water-soluble intermediates which can be easily assimilated and metabolized by microbial cells in dry anaerobic digestion process. PARAFAC of the excitation–emission matrix spectra revealed five fluorescent components occurring in effluent DOM: four humic-like components (C1–C4) and one protein-like component (C5). The Fmax values of components 1, 2, 3 and 5 showed large fluctuation than that of component C4, suggested the formation and degradation of these components. Component C4, with high aromatic content and higher degree of humification, was more difficult to be utilized and degraded by microorganisms than other components. The PARAFAC–PCA displayed three PCA factors (factors 1, 2 and 3), which accounted for 34.51, 34.20 and 31.11 %, respectively, of the variance in fluorescent components. Humic-like component C4 showed positive factor 1 loadings. Factor 2 was mainly explained by the tryptophan-like component C5. The humic-like components 1, 2 and 3 concurrently showed a relatively high factor 3 loading. The PARAFAC–PCA in this study could separate the characteristics of the DOM fluorescent component namely the source strength of the humic-like components versus the contributions of protein-like components in the total fluorescence analyses.

Characterization of CDOM from urban waters in Northern-Northeastern China using excitation-emission matrix fluorescence and parallel factor analysis.

Chromophoric dissolved organic matter (CDOM) plays an important role in aquatic systems, but high concentrations of organic materials are considered pollutants. The fluorescent component characteristics of CDOM in urban waters sampled from Northern and Northeastern China were examined by excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) to investigate the source and compositional changes of CDOM on both space and pollution levels. One humic-like (C1), one tryptophan-like component (C2), and one tyrosine-like component (C3) were identified by PARAFAC. Mean fluorescence intensities of the three CDOM components varied spatially and by pollution level in cities of Northern and Northeastern China during July-August, 2013 and 2014. Principal components analysis (PCA) was conducted to identify the relative distribution of all water samples. Cluster analysis (CA) was also used to categorize the samples into groups of similar pollution levels within a study area. Strong positive linear relationships were revealed between the CDOM absorption coefficients a(254) (R (2) = 0.89, p < 0.01); a(355) (R (2) = 0.94, p < 0.01); and the fluorescence intensity (F max) for the humic-like C1 component. A positive linear relationship (R (2) = 0.77) was also exhibited between dissolved organic carbon (DOC) and the F max for the humic-like C1 component, but a relatively weak correlation (R (2) = 0.56) was detected between DOC and the F max for the tryptophan-like component (C2). A strong positive correlation was observed between the F max for the tryptophan-like component (C2) and total nitrogen (TN) (R (2) = 0.78), but moderate correlations were observed with ammonium-N (NH4-N) (R (2) = 0.68), and chemical oxygen demand (CODMn) (R (2) = 0.52). Therefore, the fluorescence intensities of CDOM components can be applied to monitor water quality in real time compared to that of traditional approaches. These results demonstrate that EEM-PARAFAC is useful to evaluate the dynamics of CDOM fluorescent components in urban waters from Northern and Northeastern China and this method has potential applications for monitoring urban water quality in different regions with various hydrological conditions and pollution levels.

Anthropogenic signature of sediment organic matter probed by UV–Visible and fluorescence spectroscopy and the association with heavy metal enrichment

Sediment organic matter (SOM) was extracted in an alkaline solution from 43 stream sediments in order to explore the anthropogenic signatures. The SOM spectroscopic characteristics including excitation-emission matrix (EEM)–parallel factor analysis (PARAFAC) were compared for five sampling site groups classified by the anthropogenic variables of land use, population density, the loadings of organics and nutrients, and metal enrichment. The conventional spectroscopic characteristics including specific UV absorbance, absorbance ratio, and humification index did not properly discriminate among the different cluster groups except in the case of metal enrichment. Of the four decomposed PARAFAC components, humic-like and tryptophan-like fluorescence responded negatively and positively, respectively, to increasing degrees of the anthropogenic variables except for land use. The anthropogenic enrichment of heavy metals was positively associated with the abundance of tryptophan-like component. In contrast, humic-like component, known to be mostly responsible for metal binding, exhibited a decreasing trend corresponding with metal enrichment. These conflicting trends can be attributed to the overwhelmed effects of the coupled discharges of heavy metals and organic pollutants into sediments. Our study suggests that the PARAFAC components can be used as functional signatures to probe the anthropogenic influences on sediments.

Linkages among fluorescent dissolved organic matter, dissolved amino acids and lignin-derived phenols in a river-influenced ocean margin

Excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) is commonly used to investigate the dynamics of dissolved organic matter (DOM). However, a lack of direct comparisons with known biomolecules makes it difficult to substantiate the molecular composition of specific fluorescent components. Here, coincident surface-water measurements of EEMs, dissolved lignin, and total dissolved amino acid (TDAA) acquired in the northern Gulf of Mexico were used to investigate the relationships between specific fluorescent components and DOM biomolecules. Two terrestrial humic-like components identified by EEM-PARAFAC using samples obtained from river to offshore waters were strongly linearly correlated with dissolved lignin concentrations. In addition, changes in terrestrial humic-like abundance were correlated with those in lignin phenol composition, suggesting such components are largely derived from lignin and its alteration products. By applying EEM-PARAFAC to offshore samples, two protein-like components were obtained. The tryptophan-like component was strongly correlated with TDAA concentrations, corroborating the suggested protein/peptide origin of this component. The ratios of tryptophan-like component to tyrosine-like component or dissolved organic carbon (DOC) concentrations were also correlated with DOC-normalized yields of TDAA, suggesting these proxies are useful indicators of the bioavailability of DOM in marine waters of the studied ecosystem.

Assessing trihalomethanes (THMs) and N-nitrosodimethylamine (NDMA) formation potentials in drinking water treatment plants using fluorescence spectroscopy and parallel factor analysis

The formation of disinfection byproducts (DBPs) is a major challenge in drinking water treatments. This study explored the applicability of fluorescence excitation–emission matrices and parallel factor analysis (EEM–PARAFAC) for assessing the formation potentials (FPs) of trihalomethanes (THMs) and N-nitrosodimethylamine (NDMA), and the treatability of THM and NDMA precursors in nine drinking water treatment plants. Two humic-like and one tryptophan-like components were identified for the samples using PARAFAC. The total THM FP (TTHM FP) correlated strongly with humic-like component C2 (r=0.874), while NDMA FP showed a moderate and significant correlation with the tryptophan-like component C3 (r=0.628). The reduction by conventional treatment was more effective for C2 than C3, and for TTHM FP than NDMA FP. The treatability of DOM and TTHM FP correlated negatively with the absorption spectral slope (S275–295) and biological index (BIX) of the raw water, but it correlated positively with humification index (HIX). Our results demonstrated that PARAFAC components were valuable for assessing DBPs FP in drinking water treatments, and also that the raw water quality could affect the treatment efficiency.