Fluorescence Excitation-emission Matrices Research Articles

Fiber optic fluorescence as non-invasive tool to monitor the ripening process of cheeses: Torta del casar and Queso de la Serena

In this work, the use of excitation-emission fluorescence matrices (EEMs) has been addressed to differentiate two kinds of cheeses with protected designations of origin (PDO), “Torta del Casar” and “Queso de la Serena”. The fluorescence signals were recorded directly on cheese samples during the ripening process, by using a fiber optic assembled to the fluorescence spectrometer, and the data were subjected to analysis by the multivariate algorithm parallel factor analysis (PARAFAC). PARAFAC analysis identified the presence of three fluorophores in both cheeses. The scores of the two first components, attributed to the presence of tryptophane, decreased as the ripening time increased. However, the third component, related to retinol (vitamin A), remains almost constant along the ripening period. EEMs of the samples of the two types of cheese were similar in the initial days of the maturation periods. However, when only the samples from day 36 onwards were considered, it was possible to differentiate them with high precision by PARAFAC in combination with linear discriminant analysis (LDA).In addition, a model was built for the quantification of vitamin A and α-tocopherol (vitamin E), by using the EEMs combined with the multivariate unfolded partial least squares (UPLS) algorithm.

Multi-wavelength Fluorescence Monitoring of Faecal Contamination in Waters: A Laboratory-based Quantification

Near real-time monitoring of faecal indicator bacteria (FIB) in waters is currently not feasible, and current monitoring methods require field sampling and laboratory testing that inhibits decision-making within a relevant timeframe. While recent studies identified the potential of using specific fluorescence regions for FIB monitoring, sufficient accuracy often requires site-specific calibration due to minor variations in fluorescence peak locations. In this study, a series of lab experiments were completed to address some of the selectivity issues. Specifically, the study explored correlations between wavelength-specific fluorescence signals acquired through fluorescence excitation-emission matrices (EEM) and the amount of E. coli K-12 (E. coli) and E. faecalis (enterococci) in exponential and stationary phase broth cultures. Subsequently, the experiments quantified how the addition of known concentrations of L-tryptophan amplifies an indole pulse, specifically its concentration and the corresponding fluorescence properties. Results show unique peak excitation/emission (λex/λem) wavelengths (± 5 nm) in EEMs for E. coli cell pellet and in M9 broth (~ 280/ ~ 327 nm), enterococci cell pellet (~ 276/ ~ 324 nm), L-tryptophan (~ 278/ ~ 343 nm and ~ 298/ ~ 344 nm), and indole (~ 232/ ~ 321 nm). The findings demonstrate that L-tryptophan concentrations in E. coli broth were reduced. At the same time, the indole content increased throughout the initiation phase to the stationary phase of the bacteria growth curve, with the peak indole pulse occurring approximately at the time of transition from the exponential to stationary phase. Such unique fluorescence signatures for not only FIB but also indole (whose pulse can be triggered by L-tryptophan) provide foundations for developing reliable and near real-time in situ FIB sensors.

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.

Outwelling of reduced porewater drives the biogeochemistry of dissolved organic matter and trace metals in a major mangrove‐fringed estuary in Amazonia

AbstractMangrove‐fringed estuaries are intertidal ecosystems discharging significant amounts of dissolved organic matter (DOM) into coastal oceans. DOM in these ecosystems is derived from autochthonous production, fluvial input, and mangrove porewater outwelling; however, differentiating between these sources remains challenging. Our incomplete understanding of the biogeochemical factors controlling DOM dynamics and its relationship with nutrient and trace metal cycling still hinders the formulation of elemental budgets in coastal environments. Here, we relate the DOM composition in a mangrove‐fringed estuary in North Brazil (Amazonia) to the redox conditions at the formation sites. We combined molecular DOM analyses via ultrahigh‐resolution mass spectrometry (FT‐ICR‐MS) with parallel factor analysis of excitation–emission fluorescence matrices (EEM‐PARAFAC), nutrient and redox‐sensitive trace metal analyses. During low tide, the influx of oxygen‐depleted porewater carried terrigenous DOM, inorganic nutrients, and trace metals into the mangrove‐fringed creeks. Precipitation of metal(hydr)oxides and microbial turnover controlled nutrient and trace metal dynamics in the estuary. The highest inorganic nitrogen concentrations within the upper mangrove‐fringed estuary indicated outwelling from mangrove sediments as an essential source. Phosphate concentrations were highest within the lower mangrove‐fringed estuary, where available phosphate likely exceeded precipitation with iron(hydr)oxides. We tracked the DOM transport to the coastal ocean using a novel molecular index derived from sulfidic porewater (ISuP). Outwelling of recalcitrant DOM from mangrove habitats is relevant in the context of blue carbon storage. Therefore, applying our molecular proxy (ISuP), together with trace‐metal and optical DOM analyses, is a powerful approach for differentiating contributions of diverse DOM sources in highly complex coastal ecosystems.

Reclamation of impacted urban phreatic water through nanofiltration technology: Insight on natural organic matter removal by fluorescence spectroscopy

Nanofiltration (NF) is a promising technology called to play a relevant role in water reclamation, which lies in the core of circular economy in the water sector. The aim of this study was to assess two aromatic polyamide-based NF membranes (the looser NF270 and the tighter NF90 ones) for the treatment of urban impacted phreatic water. The focus was centred on the removal of dissolved inorganic and organic solutes and on the differences observed between solutes. Membrane ions rejection was modelled by the Solution-Electro-Diffusion Film Model (SEDFM). DOC was tracked by Fluorescence Excitation-Emission Matrices (FEEM) coupled to Parallel Factor Analysis (PARAFAC) to get insight into the character of DOC rejected by or permeated through the membranes. Results showed that the NF90 membrane systematically achieved upper values in the rejection of ions than the looser NF270 one. Variations between ions could be interpreted by the mechanisms ruling their rejection, i.e. Donnan and dielectric exclusion phenomena. Experimental rejections were also satisfactorily fit by the SEDFM, indicating that that the presence of DOC in the phreatic water did affect modelling of ions transport through the membranes. DOC was rejected at very high percentages (>90%) by both membranes, but FEEM-PARAFAC analysis revealed that humic- and tryptophan- like components were more rejected (>90% for both membranes) than tyrosine-like compounds (45% for NF270 and 57% for NF90). The finding is of relevance from a point of view of disinfection practices, as it has been observed that humic-like substances are strongly correlated with DBPs formation.

MIEX resin and enhanced coagulation treatment of high-bromide natural water: Chlorine reactivity and DBP precursors removal

Both organic and inorganic constituents play a major role in the formation and speciation of disinfection by-products (DBPs) under chlorination. In this study, the removal of organic and inorganic precursors to DBPs by ion exchange and coagulation was examined, and the relationships between characteristics of dissolved organic matter (DOM), chlorine reactivity, and the formation of DBPs in high-bromide natural water were investigated. Formation potential tests were conducted for trihalomethanes (THMs) and haloacetronitriles (HANs) before and after the different treatments (coagulation, magnetic ion exchange (MIEX) resin, and combined MIEX/coagulation). At a low resin dose, MIEX was more effective than coagulation for DOM removal. The advantages of the MIEX resin were more prominent at a high resin dose because substantial amounts of DOM and bromide were simultaneously removed. The maximum bromide uptake on the MIEX resin was 0.02 mg-Br/mL. A 4-component PARAFAC model was developed using a dataset of 148 fluorescence excitation-emission matrices (EEMs) generated from pre-chlorinated and post-chlorinated samples. The maximum fluorescence intensities of humic-like components were found to be strongly correlated to THMs formation (R2 = 0.79–0.89). The MIEX treatment substantially lowered the formation of THMs (19–51%) and HANs (70–95%) due to its ability to remove humic-like DOM and bromide. The fluorescence loss for humic-like DOM was found to increase over a chlorination time of 3 days, suggesting that these compounds had stronger reactivity to chlorine compared to protein-like DOM. The chlorine reactivity of protein-like DOM increased after treatments as the residual chlorine was able to react with the less reactive fractions of DOM after chlorine-reactive compounds were removed.

Contrasting occurrence of arsenic concentrations in Quaternary aquifers inside and outside the oxbow lakes along the middle reaches of the Yangtze river

Geogenic arsenic (As) contaminated groundwater poses a threat to drinking water safety and ecological health. Dissolved organic matter (DOM) plays a crucial role in As mobilization in Quaternary groundwater systems. Significant spatial variations in As concentrations in groundwater inside and outside the oxbow lakes were observed, but the controlling mechanisms remains unknown. In this study, carbon stable isotopes and fluorescence excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC) were used to elucidate the influence of DOM on contrasting occurrence of As in both inside and outside groundwater of the oxbow lakes along the middle reaches of the Yangtze River. The results showed that groundwater As concentrations outside the oxbow lakes (0.37–485 μg/L) were significantly higher than those in the groundwater inside (0.75–204 μg/L). Stable carbon isotopes suggest that methanogenesis promotes the reductive dissolution of As-bearing Fe(III) oxides/hydroxides, which is the primary process responsible for As enrichment in groundwater outside of oxbow lakes. In contrast, microbial fermentation dominated As mobilization in the groundwater inside of the oxbow lakes. The DOM in the groundwater outside of the oxbow lakes is characterized by a more reductive, predominantly more highly humified and less biologically active humus, while DOM in the groundwater inside consists mainly of microbial humic-like components that is less humified but more biologically active. This study provides new insight to decipher the controlling mechanism of As mobilization in the alluvial-lacustrine aquifers around typical oxbow lakes and is applicable to similar geogenic As-affected floodplain aquifer systems.

Detection and Quantification of Bisphenol A in Surface Water Using Absorbance-Transmittance and Fluorescence Excitation-Emission Matrices (A-TEEM) Coupled with Multiway Techniques.

In the present protocol, we determined the presence and concentrations of bisphenol A (BPA) spiked in surface water samples using EEM fluorescence spectroscopy in conjunction with modelling using partial least squares (PLS) and parallel factor (PARAFAC). PARAFAC modelling of the EEM fluorescence data obtained from surface water samples contaminated with BPA unraveled four fluorophores including BPA. The best outcomes were obtained for BPA concentration (R2 = 0.996; standard deviation to prediction error's root mean square ratio (RPD) = 3.41; and a Pearson's r value of 0.998). With these values of R2 and Pearson's r, the PLS model showed a strong correlation between the predicted and measured BPA concentrations. The detection and quantification limits of the method were 3.512 and 11.708 micro molar (µM), respectively. In conclusion, BPA can be precisely detected and its concentration in surface water predicted using the PARAFAC and PLS models developed in this study and fluorescence EEM data collected from BPA-contaminated water. It is necessary to spatially relate surface water contamination data with other datasets in order to connect drinking water quality issues with health, environmental restoration, and environmental justice concerns.

Fractionation and transport of compost‐derived dissolved organic matter fractions in saturated red soil and black soil columns

AbstractThe fractionation and transport of compost‐derived dissolved organic matter (DOMC) could affect the transport and fate of nutrients and DOM‐associated pollutants in the soil environment. In this study, the humic acid fraction of DOMC (HAC) and fulvic acid fraction of DOMC (FAC) were selected to investigate the fractionation and transport of DOMC in repacked soil columns of a red soil and a black soil under different KCl concentrations. The effluent DOMC fractions were monitored by ultraviolet (UV)‐visible (Vis) light and fluorescence spectroscopy. The results showed that the molecular weight (MW) of the effluent DOM approached that of the influent DOMC fractions with the injection of DOMC fractions. Three‐dimensional fluorescence excitation emission matrices (3D‐EEMs) coupled with parallel factor analysis resolved three fluorescent components, that is, low MW UV humic‐like substances (C1), high MW UV humic‐like substances (C2), and protein‐like substances (C3). The mobility of HAC and FAC decreased with increasing KCl concentrations (1 mM–50 mM), implying that electrostatic interaction was an important mechanism for the retention of DOMC in soil columns. The fact that the mobility of DOMC fractions in the black soil was greater than that in the red soil could be attributed to the high free Fe oxide content in the red soil. The retained DOMC fractions did not entirely desorb by the background electrolyte solution, suggesting that a part of the DOMC fractions retained in soil columns was strongly bound. These results are helpful in understanding the fractionation and transport of DOMC in soil environments.

Integrating reverse osmosis and forward osmosis (RO-FO) for printing and dyeing wastewater treatment: impact of FO on water recovery.

Reverse osmosis (RO) alone has low water recovery efficiency because of membrane fouling and limited operating pressure. In this study, a combined reverse osmosis-forward osmosis (RO-FO) process was used for the first time to improve the water recovery efficiency of secondary effluent in printing and dyeing wastewater. The effects of operating pressure and pH on water recovery and removal efficiency of RO-FO were investigated. The results showed that the optimum conditions were an operating pressure of 1.5 MPa and a feed solution pH of 9.0. Under optimal operating conditions, most of the organic and inorganic substances in the wastewater can be removed, and the rejection of total organic carbon (TOC), Sb, Ca, and K were 98.7, 99.3, 97.0, and 92.7%, respectively. Fluorescence excitation-emission matrices coupled with parallel factor (EEM-PARAFAC) analysis indicated that two components (tryptophan and tyrosine) in the influent were effectively rejected by the hybrid process. The maximum water recovery (Rw, max) could reach 95%, which was higher than the current single RO process (75%). This research provided a feasible strategy to effectively recover water from printing and dyeing wastewater.

Understanding the influence of dissolved organic nitrogen characteristics on enhanced coagulation performance for water reuse

With the recent focus on using advanced water treatment processes for water reuse, interest is growing for utilizing enhanced coagulation to remove dissolved chemical species. Up to 85% of the nitrogen in wastewater effluent is made up of dissolved organic nitrogen (DON), but there is a knowledge gap regarding its removal during coagulation, which can be influenced by DON characteristics. To address this issue, tertiary-treated wastewater samples were analyzed before and after coagulation with polyaluminum chloride and ferric chloride. Samples were size-fractionated into four molecular weight fractions (0.45 μm, 0.1 μm, 10 kDa, and 3 kDa) using vacuum filtration and ultrafiltration. Each fraction was further evaluated by coagulating it separately to assess DON removal during enhanced coagulation. The size fractionated samples were also separated into hydrophilic and hydrophobic fractions using C18 solid phase extraction disks. Fluorescence excitation-emission matrices were used to investigate the characteristics of dissolved organic matter contributing to DON during the coagulation process. The results showed that DON compounds of size <3 kDa constituted a majority of the total DON. Coagulation removed more than 80% DON from size fractions 0.45 μm–0.1 μm and 0.1 μm-10 kDa, but less than 20% was removed from 10 kDa to 3 kDa and <3 kDa fractions. Coagulation on pre-filtered samples removed 19% and 25% of the <3 kDa DON fraction using polyaluminum chloride and ferric chloride, respectively. In all molecular weight fractions, hydrophilic DON compounds were found to be dominant (>90%), and enhanced coagulation was not effective in removing hydrophilic DON compounds. LMW fractions respond poorly to enhanced coagulation due to their hydrophilic nature. Enhanced coagulation effectively removes humic acid-like substances, but poorly removes proteinaceous compounds such as tyrosine and tryptophan. This study's findings provide insights into DON behavior during coagulation and factors affecting its removal, potentially improving wastewater treatment strategies.

TreatEEM—A Software Tool for the Interpretation of Fluorescence Excitation-Emission Matrices (EEMs) of Dissolved Organic Matter in Natural Waters

Fluorescence excitation-emission matrices (EEMs) are a useful tool in aquatic sciences for monitoring and studying the biogeochemistry of organic matter in natural waters and engineered systems. Yet, the interpretation of the wealth of information available in EEMs requires the use of appropriate software. Existing software tools for the analysis of EEMs, offered by instrument producers, have limited treatment capabilities, while other freely available tools are based on the MATLAB or R programming languages, which require a certain level of programming skills and a pre-installation of MATLAB or R. Here, we present TreatEEM, the first non-commercial, stand-alone Windows-based software tool that provides comprehensive treatment of EEMs. Its greatest advantage is its user-friendly and interactive graphical user interface, providing a convivial and responsive graphical feedback on any action performed on either a single spectrum (recorded at one excitation wavelength) or EEM. The capabilities of TreatEEM, including (a) basic EEM treatment, such as simple inner filter correction, scatter removal, blank subtraction, Raman normalisation, smoothing, drift alignment etc., (b) extraction of useful parameters for DOM characterisation (Coble peaks and fluorescence indices) and (c) preparation of data for PARAFAC analysis plus presentation/manipulation of obtained PARAFAC components, are described in detail, along with a basic theoretical background on these most commonly used treatment steps of EEMs.

Two-way and three-way resolutions of fluorescence excitation-emission dataset for the co-estimation of two pharmaceuticals in a binary mixture

A new comparative study based on applying two-way and three-way data analysis methods to the fluorescence excitation-emission matrices (EEMs) was performed to co-estimate two active pharmaceutical ingredients (amlodipine besylate, AD, and telmisartan, TS) in a binary mixture. Two-way data analysis was carried out by a bilinear model algorithm using multivariate curve resolution-alternative least squares (MCR-ALS). Three-way data analysis was performed by trilinear models using parallel factor analysis (PARAFAC), and Tucker3. Loadings or profiles obtained by applying the MCR-ALS, PARAFAC, and Tucker3 to the EEMs in the presence of the overlapping excitation and emission spectra made it possible to obtain the individual contribution of the target drugs without requiring a chromatographic separation methodology. The excitation-emission spectra of the analytes were identified from the excitation and emission profiles. The quantity of two pharmaceuticals in analyzed samples was obtained from the relative concentration profiles using univariate calibration. The calibration curves were found to be linear in the range of 0.5–5.0 μg/mL for both drugs. The validity of the methods was verified by analyzing validation samples. Then, the applicability of MCR-ALS, PARAFAC, and Tucker3 approaches was tested for the assay of AD and TS in commercial tablets. For a comparison of the proposed bilinear and trilinear approaches, the statistical analyses including the one-way ANOVA and Bartlett tests were applied to the means and variances of the assay results, respectively. The statistical results showed that the precision and accuracy of the experimental results obtained with the MCR-ALS, PARAFAC, and Tucker3 models were comparable for the assay of the two target drugs.

Applying Fluorescence Dissolved Organic Matter Spectra and Phytoplankton Biology Index for Assessing Urban River Quality

The relationship between phytoplankton dynamics and dissolved organic matter (DOM) in aquatic systems based on fluorophore organic matter properties results in poor implementation of methods for water quality monitoring. This study aimed to investigate the relation between fluorophore organic matter and phytoplankton index and to estimate the phytoplankton index by fluorescent organic components for water quality assessment. The research was conducted by sampling urban river water, followed by measuring the biological phytoplankton index and dissolved organic matter during the wet and dry seasons. Fluorescence Excitation Emission Matrices (FEEMs) analysis combined with Parallel Factor (PARAFAC) analysis identified three main components of the fluorescence organic matter, i.e., a fulvic acid-like component (C1) and humic acid-like components (C2 and C3), in the aquatic system, whether in the dry season or the wet season. C1 was mainly generated by phytoplankton species, i.e., Nitzschia sp., Plectonema sp., Navicula sp., and Pinnularia sp., and C2 and C3 had a less significant relationship with phytoplankton species. The diversity of Bacillariophyta had a stronger contribution to the release of DOM than the diversity of Cyanobacteria. The abundance index of a particular phytoplankton species can be used to determine the organic components of FEEM-derived fluorescence organic matter.

Applying Fluorescence Dissolved Organic Matter Spectra and Phytoplankton Biology Index for Assessing Urban River Quality

The relationship between phytoplankton dynamics and dissolved organic matter (DOM) in aquatic systems based on fluorophore organic matter properties results in poor implementation of methods for water quality monitoring. This study aimed to investigate the relation between fluorophore organic matter and phytoplankton index and to estimate the phytoplankton index by fluorescent organic components for water quality assessment. The research was conducted by sampling urban river water, followed by measuring the biological phytoplankton index and dissolved organic matter during the wet and dry seasons. Fluorescence Excitation Emission Matrices (FEEMs) analysis combined with Parallel Factor (PARAFAC) analysis identified three main components of the fluorescence organic matter, i.e., a fulvic acid-like component (C1) and humic acid-like components (C2 and C3), in the aquatic system, whether in the dry season or the wet season. C1 was mainly generated by phytoplankton species, i.e., Nitzschia sp., Plectonema sp., Navicula sp., and Pinnularia sp., and C2 and C3 had a less significant relationship with phytoplankton species. The diversity of Bacillariophyta had a stronger contribution to the release of DOM than the diversity of Cyanobacteria. The abundance index of a particular phytoplankton species can be used to determine the organic components of FEEM-derived fluorescence organic matter.

The influence of sources and solid phase extraction criteria on dissolved organic matter optical properties in aquatic systems

The integrity of studies investigating the composition of dissolved organic matter (DOM) is heavily dependent on the sampling and instrumental techniques employed. In this study, we aimed to assess the impacts of both the source of the DOM and the solid phase extraction (SPE) criteria on changes to the optical properties of DOM. Samples were collected from various aquatic environments, ranging from headwaters to the open ocean. The extraction kinetics of DOM were monitored throughout the SPE process, with alterations to the DOM verified using optical properties derived from chromophoric dissolved organic matter (CDOM), including absorbance and fluorescence measurements. The fluorescence excitation-emission matrices (EEMs) were further analyzed using PARAllel FACtor analysis (PARAFAC) to resolve the underlying chemical components. Results indicate that the reaction of DOM to acidification required for polystyrene-divinylbenzene polymer sorbent SPE varies across samples. And this variability may stem from differences in functional groups and DOM sources. The maximum carbon loading observed was 9.7 mg C per 1 g PPL, which is a widely used styrene-divinylbenzene polymer sorbent, and no overloading was noted. The dissolved organic carbon (DOC) extraction efficiency (EE) ranged from 51.5-61.5% and 27.6-40.0% for post- and extract- calculations, respectively, with no significant differences in DOC EE observed among different initial DOC concentrations, salinities, and flowrates. The differences in DOC EE across diverse sources and changes in optical proxies resulting from PPL extraction were mainly due to the heterogeneity of DOM. PPL extraction altered the overall molecular characteristics of DOM from more labile to more refractory or degraded in the open ocean and headwater source samples. Notably, high and low flowrates yielded identical SPE-DOM extraction and alterations. The results indicate that DOM sources primarily control SPE EE rather than methodological or other environmental factors. PPL SPE results in a convergence of DOM variability. These findings provide crucial insights into inter-study comparisons and the interpretability of SPE-derived DOM data from samples across diverse aquatic environments.

Acidogenic Fermentation of Brewers’ Spent Grain Monitored through Two-Dimensional Fluorescence Spectroscopy

Biological systems are commonly controlled and monitored through offline and time-consuming tools, which often impairs an effective and real-time response to counteract system disturbances. The feasibility of using two-dimensional (2D) fluorescence spectroscopy as a non-invasive, non-destructive, and real-time procedure to monitor the acidogenic fermentation of brewer’s spent grain (BSG) in a granular sludge reactor was evaluated. For that, the effect of pH fluctuations on the system response was used as a model to ascertain the 2D fluorescence spectroscopy applicability to monitor the process performance, namely, to predict the fermentation products (FP) and the soluble protein (SProt) concentrations in the effluent stream through mathematical analysis. The pH fluctuations over the course of the reactor’s operation altered the granules’ microbiome composition, leading to different effluent FP profiles. Fluorescence excitation–emission matrices (EEMs) were used with projection to latent structures (PLS) modeling to predict the FP and SProt concentrations in the effluent with average errors below 0.75 and 0.43 g L–1, respectively. Both models were able to capture the tendency of the data even when the accuracy of prediction was not so high. The combined approach of using 2D fluorescence spectroscopy and mathematical analysis seemed promising for real-time monitoring of the acidogenic fermentation of complex substrates.

Dataset of Fluorescence EEM and UV Spectroscopy Data of Olive Oils during Ageing

The dataset presented in this study encompasses fluorescence excitation–emission matrices (EEMs) and UV-spectroscopy data of 24 extra virgin olive oils (EVOOs) commercially available at supermarkets in Switzerland. To investigate the effect of thermal degradation, the samples were exposed to accelerated ageing at 60 ∘C up to 53 days. EEMs and UV absorption parameters were measured in 10 ageing steps. The dataset can be used, for example, to predict one or multiple chemical parameters or to classify samples based on their quality from fluorescence spectra.

Arsenic migration at the sediment-water interface of anthropogenically polluted Lake Yangzong, Southwest China

The lability and controlling factors of arsenic (As) at the sediment-water interface (SWI) are crucial for understanding As behaviors and fates in As-contaminated areas. In this study, we combined high-resolution (5 mm) sampling using diffusive gradients in thin films (DGT) and equilibrium dialysis sampling (HR-Peeper), sequential extraction (BCR), fluorescence signatures, and fluorescence excitation-emission matrices (EEMs)-parallel factor analysis (PARAFAC) to explore the complex mechanisms of As migration in a typical artificially polluted lake, Lake Yangzong (YZ). The study results showed that a high proportion of the reactive As fractions in sediments can resupply pore water in soluble forms during the change from the dry season (winter, oxidizing period) to the rainy season (summer, reductive period). In dry season, the copresence of Fe oxide-As and organic matter (OM)-As complexes was related to the high dissolved As concentration in pore water and limited exchange between the pore water and overlying water. In the rainy season, with the change in redox conditions, the reduction of Fe-Mn oxides and OM degradation by microorganisms resulted in As deposition and exchange with the overlying water. Partial least squares path modelling (PLS-PM) indicated that OM affected the redox and As migration processes through degradation. Based on comprehensive analyses of the As, Fe, Mn, S and OM levels at the SWI, we suggest that the complexation and desorption of dissolved organic matter and Fe oxides play an important role in As cycling. Our findings shed new light on the cascading drivers of As migration and OM features in seasonal lakes and constitute a valuable reference for scenarios with similar conditions.

Isotopic and spectral signatures unravel the sources, preservation and degradation of sedimentary organic matter in the Dongzhai Harbor mangrove estuary, southern China

Sedimentary organic matter (SOM) production and transformation processes have a prominent role in regulating biogenic element cycling in mangrove ecosystems. However, aquaculture biodeposits can substantially affect source apportionments and biogeochemical processes of SOM within mangroves. In this study, natural stable isotopes (13C and 15N), spectral techniques, and hydrogeochemical analysis were used to elucidate the sources, preservation, and degradation of SOM across the Dongzhai Harbor (DZH) estuary, southern China, where aquaculture systems are extensive. Along the estuarine salinity gradient, sediment and bottom water samples were collected from the upper fluvial mangrove zones to the lower marine endmember. Results indicated that source contributions to SOM along the estuarine gradient were spatially heterogeneous. Aquaculture-derived organic matter was the largest contributor to the Sanjiang River (44.29 %) in the upper estuary, and terrestrial sources from C3 mangrove forests were highest in the Yanfeng East River (62.87 %) near the middle estuary. Farther seaward, marine plankton sources were elevated in the Dongzhai Harbor channel (64.15 %) and Yanfeng West River (48.83 %) of the lower estuary. The terrestrial/microbial humic-like component (C1), tryptophan-like component (C2), and soil-derived fulvic acid (C3) were identified from the samples using fluorescence excitation emission matrices and parallel factor analysis (EEM-PARAFAC). Results show that in the upper and middle estuary, SOM was preserved by sedimentation due to the abundance of fine-grained aquaculture-derived biodeposits, weak hydrodynamic conditions, and the formation of Fe/Mn-humus complexes. In contrast, in the lower estuary, SOM originated from marine plankton and was rapidly degraded via aerobic respiration. Moreover, correlations between δ13C and δ15N values vs C/N ratios further suggest progressive SOM degradation from initial diagenesis to post-depositional geochemical processes. This study provides new insights into aquacultural and environmental factors controlling SOM preservation and degradation within estuaries. The findings have implications for shoreline stability and the protection and restoration of estuarine mangrove wetlands.