Excitation-emission Matrices-parallel Factor Analysis Research Articles

An optimised and validated surrogate analyte A-TEEM-PARAFAC-PLS technique for detecting and quantifying the biological oxygen demand in surface water.

A 5-day test duration makes BOD5 measurement unsatisfactory and hinders the development of a quick technique. Protein-like fluorescence peaks show a strong correlation between the BOD characteristics and the fluorescence intensities. For identifying and measuring BOD in surface water, a simultaneous absorbance-transmittance and fluorescence excitation-emission matrices (A-TEEM) method combined with PARAFAC (parallel factor) and PLS (partial least squares) analyses was developed using a tyrosine and tryptophan (tyr-trpt) mix as a surrogate analyte for BOD. The use of a surrogate analyte was decided upon due to lack of fluorescent BOD standards. Tyr-trpt mix standard solutions were added to surface water samples to prepare calibration and validation samples. PARAFAC analysis of excitation-emission matrices detected the tyr-trpt mix in surface water. PLS modelling demonstrated significant linearity (R2 = 0.991) between the predicted and measured tyr-trypt mix concentrations, and accuracy and robustness were all acceptable per the ICH Q2 (R2) and ASTM multivariate calibration/validation procedures guidelines. Based on a suitable and workable surrogate analyte method, these results imply that BOD can be detected and quantified using the A-TEEM-PARAFAC-PLS method. Very positive comparability between tyr-trypt mix concentrations was found, suggesting that tyr-trypt mix might eventually take the place of a BOD-based sampling protocol. Overall, this approach offers a novel tool that can be quickly applied in water treatment plant settings and is a step in supporting the trend toward rapid BOD determination in waters. Further studies should demonstrate the wide application of the method using real wastewater samples from various water treatment facilities.

Dissolved Organic Matter Behaviour by Conventional Treatments of a Drinking Water Plant: Controlling Its Changes with EEM-PARAFAC

In the last 20 years, several articles related to the use of fluorescence excitation–emission matrices—parallel factor analysis (EEM-PARAFAC) to monitor dissolved organic matter (DOM) in drinking- and wastewater treatment plants were published. Noteworthy, its use in respective quality control laboratories remains scarce. To extend its popularisation, in this work, EEM-PARAFAC was employed to analyse the DOM composition changes along the different stages of the drinking water treatment plant administrated by Società Metropolitana Acque Torino. The best PARAFAC model was the one of three components, indicating that the Po River is constituted, mainly, by humic acid-like (HA-L) and tryptophan-like (Try-L) substances, the tyrosine-like ones being negligible (Tyr-L). Results indicated that physical treatments (sedimentation) did not produce a reduction in the PARAFAC scores; however, a 50% decay in 254 nm absorbance was observed. Fluorescent DOM was only removed with chemical treatments, obtaining ca. 70% HA-L scores decay with ozonation and 40% with chlorination. Furthermore, although ozonation degraded HA-L substances, the Try-L scores increased by 25%, indicating the transformation of HA-L into smaller molecules. On the contrary, total organic carbon measurements only exhibited a significant change when comparing the treatment plant’s inlet and outlet (approximately a 45% decrease), but not within intermediate processes.

Unveiling changes in the complexation of dissolved organic matter with Pb(II) by photochemical and microbial degradation using fluorescence EEMs-PARAFAC

Dissolved organic matter (DOM) is very important in determining the speciation, behaviors, and risk of metal pollutants in aquatic ecosystems. Photochemical and microbial degradation are key processes in the cycling of DOM, yet their effects on the DOM-Pb(II) interaction remain largely unknown. This was studied by examining the complexation of river DOM with Pb(II) after degradation, using fluorescence quenching titration and excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Three humic-like and two protein-like components were identified, with strong removals of humic-like components and decreasing average molecular weight and humification degree of DOM by photo- and photo-microbial degradation. The changes in humic-like abundance and structure resulted in notable weakening of their interaction with Pb(II). The tryptophan-like C2 was also mainly removed by photo-degradation, while the tyrosine-like C3 could be either removed or accumulated. The Pb(II)-binding of protein-like components was generally weaker but was enhanced in some degradation groups, which might be related to the lowering competition from humic-like components. The binding parameters correlated significantly with the DOM indices, which were dominated by photo-degradation for humic-like components but by seasonal variations for the tyrosine-like component. These results have implications for understanding the key mechanisms underlying the variability of the DOM-metal interaction in aquatic environments.

Effects of Photodegradation on the Optical Indices of Chromophoric Dissolved Organic Matter from Typical Sources.

Chromophoric dissolved organic matter (CDOM) plays important roles in aquatic environments, and its optical properties provide a series of indices for evaluating the source and composition of dissolved organic matter (DOM). However, little is known about the varying photodegradation of CDOM from different sources and the effects on the optical indices of DOM composition. This was studied for typical natural and anthropogenic sources (plant and leaf litter leachates, the influent and effluent of a wastewater treatment plant, and a river). The CDOM absorption (a280) showed a lower degradability for the plant leachate than other sources, mainly due to its low molecular weight and aromaticity. Four fluorescent components were identified with excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC), namely benzoic acid/monolignol-like C1, humic-like C2 and C3, and tryptophan-like C4. The plant leachate contained mainly C1, which was photodegraded moderately, while other sources had more C2 and C3 with higher photodegradability. C4 was photodegraded in most sources but was photoproduced in the leaf litter leachate. The absorption slope (S275-295) and slope ratio (SR) increased while the humification index (HIX) decreased, suggesting a decreasing molecular weight and humic content by photodegradation. This was consistent with the decreasing %C2 and %C3 but increasing %C4, which indicated preferential removal of humic-like components. The %C1, %C2, biological index (BIX), and fluorescence index (FI) were less affected by photodegradation than other indices for most sources. These results have implications for a better understanding of the photochemistry of CDOM and the applications of optical indices.

Optical characterization of dissolved organic matter in Kuroshio-Oyashio confluence region: Implication for water mass mixing

Chromophoric dissolved organic matter (CDOM) and fluorescent DOM (FDOM) are important components of DOM and play many important roles in biogeochemical processes. Here, we examined the concentration, composition, and distribution of DOM in waters (0–1000 m depth) from the Kuroshio-Oyashio confluence region (Northwestern Pacific), a key area for ocean carbon cycle and an important fishery. Dissolved organic carbon concentration varied between 30.5 and 78.2 μmol L−1 with a higher level in surface waters. Two humic-like components (C1, C3) and one protein-like component (C2) were identified by fluorescence excitation emission matrices-parallel factor analysis. The C1 and C3 intensity generally increased with depth, and positively correlated with apparent oxygen utilization (p < 0.01), whereas the C2 intensity decreased downward, and negatively correlated with apparent oxygen utilization (p < 0.01), suggesting in-situ production of bio-refractory C1 and C3 during the microbial transformation of labile organic matter (like C2). The C1 intensity was significantly different among three water masses (p < 0.01) that was 11.7 ± 2.5 × 10−3 R.U. for Kuroshio Current, 20.1 ± 1.9 × 10−3 R.U. for Oyashio Current, and 26.1 ± 5.8 × 10−3 R.U. for North Pacific Intermediate Water. The application of three-endmember mixing model based on the C1 intensity and salinity revealed variable contributions of Kuroshio, Oyashio, and North Pacific Intermediate Water that were consistent with the predication from water temperature and salinity. Our study suggests that the optical property of DOM is a useful tracer for water masses in the Kuroshio-Oyashio confluence region, consisting with previous reports for other marine environments.

Comparison of UV-based advanced oxidation processes for the removal of different fractions of NOM from drinking water

This study examined the effectiveness for degradation of hydrophobic (HPO), transphilic (TPI) and hydrophilic (HPI) fractions of natural organic matter (NOM) during UV/H2O2, UV/TiO2 and UV/K2S2O8 (UV/PS) advanced oxidation processes (AOPs). The changing characteristics of NOM were evaluated by dissolved organic carbon (DOC), the specific UV absorbance (SUVA), trihalomethanes formation potential (THMFP), organic halogen adsorbable on activated carbon formation potential (AOXFP) and parallel factor analysis of excitation–emission matrices (PARAFAC-EEMs). In the three UV-based AOPs, HPI fraction with low molecular weight and aromaticity was more likely to degradate than HPO and TPI, and the removal efficiency of SUVA for HPO was much higher than TPI and HPI fraction. In terms of the specific THMFP of HPO, TPI and HPI, a reduction was achieved in the UV/H2O2 process, and the higest removal rate even reached to 83%. UV/TiO2 and UV/PS processes can only decrease the specific THMFP of HPI. The specific AOXFP of HPO, TPI and HPI fractions were all able to be degraded by the three UV-based AOPs, and HPO content is more susceptible to decompose than TPI and HPI content. UV/H2O2 was found to be the most effective treatment for the removal of THMFP and AOXFP under given conditions. C1 (microbial or marine derived humic-like substances), C2 (terrestrially derived humic-like substances) and C3 (tryptophan-like proteins) fluorescent components of HPO fraction were fairly labile across the UV-based AOPs treatment. C3 of each fraction of NOM was the most resistant to degrade upon the UV-based AOPs. Results from this study may provide the prediction about the consequence of UV-based AOPs for the degradation of different fractions of NOM with varied characteristics.

Comparing the Pb(II) binding with different fluorescent components of dissolved organic matter from typical sources.

Dissolved organic matter (DOM) is important for determining the speciation, environmental behavior, and effects of metal pollutants in aquatic environments. However, little is known about the difference between DOM from natural and anthropogenic sources for binding Pb(II). This study examined the Pb(II) binding with DOM from four typical sources including river, leaf litter leachate, and the influent and effluent of a wastewater treatment plant, using fluorescence quenching titration and excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). Four humic-like and one protein-like fluorescent components were identified, with much higher protein-like fraction and lower humification degree for the influent than for other sources. In the river water and leaf litter leachate, the abundant humic-like components were quenched by 6-17% while the protein-like component kept stable (2-4%) by the addition of Pb(II). In contrast, the influent DOM showed stronger fluorescence quenching of the protein-like component (46%) with higher conditional stability constant and binding fraction of fluorophore than the humic-like components (15-21%). The effluent DOM displayed weak quenching for all fluorescent components (4-6%) and thus weak complexation with Pb(II), indicating notable changes in the chemical composition and metal-binding affinity of DOM by wastewater treatments. These results demonstrated significant impacts of DOM source and chemical composition on its Pb(II) complexation properties, which have implications for understanding the interactions between DOM and heavy metals.

Water- and Base-Extractable Organic Matter in Sediments From Lower Yangtze River–Estuary–East China Sea Continuum: Insight Into Accumulation of Organic Carbon in the River-Dominated Margin

The burial of organic carbon (OC) in the river-dominated margin plays an important role in global carbon cycle, but its accumulation mechanism is not well understood. Here, we examined the concentration and distribution of water-extractable organic matter (WEOM) and base-extractable organic matter (BEOM) in surface sediments from the lower Yangtze River, estuary, and the East China Sea. Chemical characteristics of the WEOM and BEOM were described by multiple ultraviolet-visible and fluorescence spectral indicators. Concentrations of both WEOM and BEOM showed significant correlations with sediment grain size, suggesting that mineral surface area is a key factor for OC loadings on sediments. Three components (C1, C2, and C3) extracted from fluorescence excitation emission matrices-parallel factor analysis were assigned as terrigenous humic-like substance, mixed terrigenous/aquatic humic-like substance, and microbial protein-like substance, respectively. From the lower Yangtze River to the East China Sea, the C1%, specific UV absorbance at 254 nm (SUVA254), and humification index (HIX) of the WEOM decreased, while the C3%, fluorescence index (FI), and biological index (BIX) of the WEOM increased. This suggested the loss of terrigenous OC and addition of microbial OC in the WEOM. While for BEOM, the overall increase of C1% and HIX and the decrease of C3% and FI suggested selective removal of microbial OC and preferential preservation of terrigenous OC. Our study demonstrates complex behaviors of sediment organic matter (OM) during the land-to-sea transport that is largely controlled by the binding strength of OM–sediment association, and that the formation of BEOM is an important pathway for accumulation of terrigenous OM in the river-dominated margin.

Insights into fouling behavior in a novel anammox self-forming dynamic membrane bioreactor by the fluorescence EEM-PARAFAC analysis.

Fouling behavior of the novel anaerobic ammonium oxidation (anammox) self-forming dynamic membrane bioreactor (SFDMBR) was elucidated, which is using nylon mesh as the filter with controlled fouling and successful anammox process. Properties of anammox sludge and foulants in the anammox SFDMBR and MBR (using PVDF microfiltration membrane) were compared to analyze the alleviated fouling in the SFDMBR, of which transmembrane pressure could be kept below 10kPa for 50days in one filtration cycle of 82days with flux of 12Lm-2h-1. Colorimetrical determination and excitation emission matrices-parallel factor (EEM-PARAFAC) analysis of the foulants showed that humic acid content in foulants on nylon mesh was obviously lower than that on PVDF membrane. Considering that the small-sized and flexible humic acids prefer to plug into membrane pores, the alleviated irreversible fouling in the SFDMBR could be attributed to the less microbial humic acid content of foulants (8.8 ± 1.0%) compared with the MBR (20.7 ± 2.9%). The adequate efflux of humic-like substances in the operation with nylon mesh was speculated to be the main mechanism of fouling control in the SFDMBR. These findings highlighted the potential of anammox SFDMBR in practical applications, because of the high humic acid contents in real ammonium-laden wastewater. Our study highlights the important role of humic acids in fouling behavior of the novel anammox SFDMBR to provide guidance for fouling control strategies. Graphical abstract.

Establishing a terrestrial proxy based on fluorescent dissolved organic matter from sediment pore waters in the East China Sea

Terrestrial organic matter occupies an important position in the oceanic organic carbon pool. Some terrestrial proxies, like the Branched and Isoprenoid Tetraether (BIT) index, have been applied successfully to indicate the relative abundance of terrestrial organic matter in marine sediments. A new terrestrial proxy derived from sediment pore water fluorescent dissolved matter (fluorescent dissolved organic matter (FDOM)) was developed in this study. Surface sediment samples were collected from forty-two sites in the coastal region of the East China Sea (ECS) to examine the distributional patterns of FDOM. Three protein-like components (C1, C4 and C5) and two humic-like components (C2 and C3) of FDOM were identified using fluorescence excitation-emission matrices parallel factor analysis (EEMs-PARAFAC). Spatially, the intensity of these five components generally increased from the coast to the ocean with protein-like components showing a more obvious trend, which suggested that all five components had autochthonous contribution. However, the C2 and C3 proportions, especially C2 that mainly corresponds to the proportion of peak A in fluorescence excitation-emission matrices, significantly decreased from the coast to the ocean and significantly correlated with the BIT index from corresponding solid fractions. We posit that part of the humic-like components from terrestrial organic matter in sediments are released into the C2 and C3 pools in pore waters, which may be constrained by specific environmental conditions. Thus, the FDOM from pore waters can be integrated with BIT index to validate the nature of FDOM and use it as a biomarker to reflect the terrestrial input of organic matter mediated by different biogeochemical processes in coastal oceans. The proportion of peak A responsible for the fluorescence of C2 was suggest as a new terrestrial derived from FDOM.

Variations in Colloidal DOM Composition with Molecular Weight within Individual Water Samples as Characterized by Flow Field-Flow Fractionation and EEM-PARAFAC Analysis.

Fluorescence excitation emission matrices (EEM) and parallel factor (PARAFAC) analysis have been widely used in the characterization of dissolved organic matter (DOM) in the aquatic continuum. However, large sample sets are typically needed for establishing a meaningful EEM-PARAFAC model. Applications of the EEM-PARAFAC technique to individual samples require new approaches. Here, flow field-flow fractionation (FlFFF) combined with offline EEM measurements and PARAFAC analysis was used to elucidate the dynamic changes in DOM composition/optical properties with molecular weight within individual samples. FlFFF-derived size spectra of ultrafiltration-isolated colloidal DOM show that peak-C related fluorophores(Ex/Em= 350/450 nm) are present mostly in the 1-3 kDa size range, while peak-T associated fluorophores (Ex/Em = 275/340 nm) have a bimodal distribution with peaks in both the 1-3 kDa and the >100 kDa size fractions. The integrated EEM spectra from FlFFF size-fractionated subsamples closely resembled the bulk EEM spectra, attesting to the convincing comparability between bulk and FlFFF size-fractionated EEMs. The PARAFAC-derived DOM components are distinctive among individual samples with the predominant components being humic-like in river water, but protein-like in a highly eutrophic lagoon sample. This compelling new approach combining FlFFF and EEM-PARAFAC can be used to decipher the dynamic changes in size spectra and composition of individual DOM samples from sources to sinks or across the redox/hydrological/trophic interfaces.

Response of bacterial community in composition and function to the various DOM at river confluences in the urban area

River confluences result in mixture and transformation of dissolved organic matter (DOM), influencing the phylogeny of microbial community, furthermore, the integrity and function of river systems. The relationship between the microbial community and DOM is complex, especially in the confluence zone. Previous reports focused on shifts in the different bacterial community in response to exposure to the same terrestrial DOM. However, the transformation of bacterial community induced by convergent DOM remains unknown. This study showed the shifts of DOM components at the junction via excitation–emission matrices parallel factor analysis. Metabolic differences were also determined via phylogenetic investigation of communities by reconstruction of unobserved states. The results demonstrated a direct link between the microbial metabolism and DOM biodegradation during the heterotrophic process. In response to diverse DOM conditions, the taxonomic composition and metabolic function of the microbial community presented significant differences. Different taxa may be involved in metabolizing various DOM components. As indicative bacteria that are closely associated with DOM components, Proteobacteria (Sphingomonas) are significant for microbial utilization and were important during the DOM-degrading process. Compared with other conditions, the abundance of carbon metabolism was higher in convergences where urban rivers joined with estuary or source water. Furthermore, humic-like DOM, converging in the confluence zone, induced a more active lipid metabolism. This study applied techniques that capture the diversity and complexity of bacterial communities and DOM, and provides new insight on the basis of the interaction between bacterial communities and DOM in confluence processes of biogeochemical significance.

Combination of DGT and fluorescence spectroscopy for improved understanding of metal behaviour in mangrove wetland

Understanding bioavailable metal behaviour in situ is critical for pollution evaluation and contaminant management in mangrove wetland. Here, the diffusive gradients in thin films technique (DGT) was used for characterizing the (bio)available portions of Cr, Zn, Pb, Cu, Fe and Mn in two mangrove wetlands affected by industrial waste discharges (Jiulong Estuary) and domestic discharges (Zhangjiang Estuary), in Fujian Province, China. In addition, fluorescence excitation emission matrices-parallel factor analysis (EEM-PARAFAC) was applied for characterizing the occurrence and behaviour of dissolved organic matter (DOM) in soil solution, as well as their feasibility for assessing behaviours of metals. The results demonstrated that the combination of DGT and EEM, which are well suitable for studying DOM impacted metal behaviors in mangrove sediments. Discharge of difference wastewater into the mangrove wetlands of Jiulong and Zhangjiang Estuaries, gave rise to the DGT-labile metal concentration of Zn > Cu > Cr > Pb and Zn > Cr > Pb > Cu, respectively. A variety of humic-like fluorescent components was characterized here, providing valuable insights into the chemical composition of DOM in rhizosphere and bulk sediment. Terrestrial humic-like compounds indicated a different binding affinity for heavy metals in mangrove sediments. These findings are useful for the future understanding of the metal speciation and molecular binding mechanisms in such mangrove wetlands.

Occurrence and behaviors of fluorescence EEM-PARAFAC components in drinking water and wastewater treatment systems and their applications: a review.

Fluorescence excitation emission matrices-parallel factor analysis (EEM-PARAFAC) is a powerful tool for characterizing dissolved organic matter (DOM), and it is applied in a rapidly growing number of studies on drinking water and wastewater treatments. This paper presents an overview of recent findings about the occurrence and behavior of PARAFAC components in drinking water and wastewater treatments, as well as their feasibility for assessing the treatment performance and water quality including disinfection by-product formation potentials (DBPs FPs). A variety of humic-like, protein-like, and unique (e.g., pyrene-like) fluorescent components have been identified, providing valuable insights into the chemical composition of DOM and the effects of various treatment processes in engineered systems. Coagulation/flocculation-clarification preferentially removes humic-like components, and additional treatments such as biological activated carbon filtration, anion exchange, and UV irradiation can further remove DOM from drinking water. In contrast, biological treatments are more effective for protein-like components in wastewater treatments. PARAFAC components have been proven to be valuable as surrogates for conventional water quality parameter, to track the changes of organic matter quantity and quality in drinking water and wastewater treatments. They are also feasible for assessing formations of trihalomethanes and other DBPs and evaluating treatment system performance. Further studies of EEM-PARAFAC for assessing the effects of the raw water quality and variable treatment conditions on the removal of DOM, and the formation potentials of various emerging DBPs, are essential for optimizing the treatment processes to ensure treated water quality.

Fluorescence spectroscopy to study dissolved organic matter interactions with agrochemicals applied in Swiss vineyards.

UV/Vis fluorescence spectroscopy was used to study the possible interactions of dissolved organic matter (DOM) with the herbicide glyphosate and copper-based fungicide used in vineyards. The study focused on the role of DOM in the transport of these micropollutants from parcels to surface waters (river, lake). Soil solution and river water samples were collected in the Lavaux vineyard area, western Switzerland. Their fluorescence excitation emission matrices (EEM) were decomposed using parallel factor (PARAFAC) analysis, and compared to their content in glyphosate and copper. PARAFAC analysis of EEM of both types of samples showed the contribution of protein-like and humic-like fluorophores. In soil water samples, complexes between fulvic-like and humic-like fluorophores of DOM, copper, and glyphosate were likely formed. In surface water, DOM-copper and glyphosate-copper interactions were observed, but not between glyphosate and DOM.

Spatial variation in the origin and reactivity of dissolved organic matter in Oregon-Washington coastal waters

Combining stable carbon isotopic signatures (δ13C-DOC) and optical properties of dissolved organic matter (DOM), we examined spatial variability in the sources and reactivity of DOM from Oregon-Washington coastal waters, with a particular focus on evaluating whether these measurements may reliably trace terrigenous DOM in coastal oceans. We sampled four stations on the continental shelf and four stations on the continental slope near the mouth of the Columbia River, with sampling depths ranging from 0 to 1,678 m. Nitrate and phosphate concentrations were largely controlled by organic matter (OM) regeneration although the river plume may have led to excess nitrates in relation to phosphates near the river mouth and/or the surface. Four fluorescence components (C1 to C4) were identified by using excitation emission matrices-parallel factor analysis. C1 and C2 were assigned as humic-like components which represented degraded DOM rather than OM of allochthonous or autochthonous origin. C3 and C4 were both labile, protein-like components representing autochthonous contributions, while C4 was more sensitive to diagenesis. In the shallow water layer (salinity ≤32.5 and depth ≤50 m), the variation in absorption properties (SUVA254 and ɛ280), fluorescence index, freshness index (β/α), percent fluorescence of C3, and δ13C-DOC revealed that the Columbia River plume exported DOM that was characterized by greater aromaticity, higher molecular weight, and being more decomposed than marine, autochthonous DOM. However, these signatures of terrigenous DOM disappeared rapidly with increasing depth and offshore distance. In the intermediate and deep water layers (salinity >32.5), the DOM indices were most driven by diagenesis, with changes in percent fluorescence components indicating increasing accumulation of humic DOM relative to protein-like DOM with depth. Principal component analysis that collectively assessed the DOM indices suggests that diagenesis was the primary factor driving the spatial variability of DOM properties in the study region, underlining challenges in tracing allochthonous DOM in coastal waters.

Fluorescent natural organic matter fractions responsible for ultrafiltration membrane fouling: Identification by adsorption pretreatment coupled with parallel factor analysis of excitation–emission matrices

A novel approach using adsorption pretreatment coupled with parallel factor analysis of excitation–emission matrices (PARAFAC-EEMs) was proposed to rapidly identify the role of fluorescent natural organic matter (NOM) fractions in ultrafiltration (UF) membrane fouling for given feed water and membrane. Two anion exchange resins, three polymeric resins and a powdered activated carbon (PAC) with diverse adsorption characteristics were adopted in the adsorption of raw water. The matrix of fluorescent NOM was substantially changed by the adsorption pretreatment, which rapidly enabled a diversity of fluorescent NOM with the components of an identical origin. PARAFAC-EEMs were employed to characterize the variation of fluorescent NOM during the adsorption, which in turn allowed to correlate the fluorescent NOM components with the membrane fouling in the following UF test. The results showed that, for the Songhua River water and PVDF UF membrane (Litree, China), three statistically significant fluorescent components (arbitrarily labeled C1, C2, and C3) were obtained through PARAFAC analysis, in which two humic-like (C1 and C2) and one protein-like (C3) components were identified. Total and irreversible fouling were highly correlated with the maximum fluorescence intensity (Fmax) of C3, while poorly correlated with the Fmax of C1 and C2, suggesting that C3 can act as an indicator for the UF membrane fouling. Moreover, C1, C2 and C3 have a considerable synergistic contribution to the irreversible fouling of the UF membrane with the analysis of multiple linear regression. These results are expected to provide important implications for monitoring and controlling UF membrane fouling.

Parallel factor analysis of EEM of the fluorescence of carbon dots nanoparticles

AbstractThe effect of experimental factors [pH and Hg(II)] on the fluorescence excitation emission matrices (EEMs) of nanosensor carbon dots (CDs) was analyzed by multiway decomposition methods based on parallel factor (PARAFAC) analysis. PARAFAC analysis of the EEM structures identifies three components corresponding to two different‐sized CDs with the Hg(II) and pH profiles highly correlated plus a background. Parallel profiles with Linear Dependences (PARALIND) model with three components in the excitation–emission spectral modes and two components in the Hg(II) or pH mode gave similar results as PARAFAC, but is more useful from a theoretical point of view because PARALIND shows that the two different‐sized CDs have similar chemical reactivity toward Hg(II) and pH. PARAFAC2 was used as a trilinear confirmatory test of the data structures under analysis. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Parallel Factor Analysis of Excitation–Emission Matrices to Assess Drinking Water Disinfection Byproduct Formation During a Peak Formation Period

Parallel factor (PARAFAC) analysis was applied to the fluorescence excitation–emission matrices (EEM) of a water treatment plant's source and coagulated water during a peak chlorinated byproduct formation period. Water plant operations included the use of surface water only and surface/ground water mixtures. Three statistically significant components were obtained through PARAFAC analysis and were correlated to dissolved organic carbon (DOC), chlorine consumption, and individual disinfection byproduct (DBP) formation potential. Multifactor linear regression of select component scores showed linear relationships to individual chloro-DBP compounds providing insight to possible precursor locations within the EEM and organic matter, as well as, organic compound characteristics responsible for chloro-DBP formation. Likewise, linear relationships were also observed between component scores and empirically estimated precursor concentration methods reported in the literature. These results suggest PARAFAC analysis of EEM may be an effective tool for monitoring source water, measuring treatment process effectiveness (removal of specific DBP precursor), and estimating DBP precursor concentrations and individual DBP compound formation potential.