Fluorescence Spectral Characteristics Research Articles

Study on Rice Origin and Quality Identification Based on Fluorescence Spectral Features

The origin of agricultural products significantly influences their quality and safety. Fluorescence spectroscopy was used to analyse Japonica rice 830, grown in different areas of Jilin Province, by examining rice seed, brown rice, and rice flour from 12 origins. Fluorescence spectra were pre-processed through normalisation and smoothing to remove noise. These processed spectra were input into decision trees, support vector machines (SVMs), K-nearest neighbour (KNN), and neural network models for classification. The analysis revealed that the combined four models achieved an average classification accuracy of 98.05% with a computation time of 180 s, while the reduced-scale models improved accuracy to 98.36% and reduced computation time to 11.25 s. Additionally, prediction models using standard rice starch content values across different states achieved R² values over 0.8. This method provides a rapid, precise approach for assessing rice quality and origin, demonstrating significant potential for application in rice analysis.

Detection of powder samples based on UV Raman-fluorescence spectroscopy

Rapid and accurate analysis of powder samples is crucial for public safety and food security. Raman spectroscopy, noted for its many advantages, traditionally faces issues of low sensitivity and limited detection information when analyzing powder samples. This paper explores a detection method for powder samples using ultraviolet (UV) Raman-fluorescence spectroscopy. By leveraging the principles of Raman and fluorescence spectroscopy, a combined detection optical path was designed. Utilizing a 266 nm laser as the system light source, a UV Raman-fluorescence spectroscopy detection setup was constructed and seven representative powder samples were analyzed. The experimental results demonstrate that the setup effectively detects the Raman spectral features of inorganic powders like baking soda and extracts the fluorescence spectral features of organic powders such as 1,2,4,5-tetramethyltoluene. Additionally, it accurately analyzes the Raman and fluorescence spectral features of amino acids and glyphosate preparation powders. For complex powder samples with issues such as “substances with the same spectrum” and “complex and similar spectra”, UV Raman-fluorescence spectroscopy enhances spectral information dimensions, compensating for the limitations of traditional Raman spectroscopy. Furthermore, a convolutional neural network algorithm was employed to analyze the measured data of the seven powder samples increased the average recognition accuracy (AVG) from 62.53% to 98.41%. This improvement further validates the effectiveness of the proposed method in recognizing the properties of powder samples.

Characteristics of dissolved organic matter during the cyanobacterial degradation in Chaohu Lake, China.

The actual DOM in Chaohu Lake was used to feed cyanobacterial to explore the changes of microbial communities, fluorescence spectral characteristics and molecular composition of DOM during the degradation of cyanobacteria. It is found that cyanobacterial grow periodically depending on the concentration of nutrients with the decreasing concentration of nutrient salts. Both Bacteroidetes and Actinobacteria have strong correlation with algae growth. Bacteroidetes has a positive correlation with algae growth, relationship on the contrary, Actinobacteria has a negative relationship. The humus-like components in the four groups are similar, but the protein-like component (C3) shows periodic changes with the life process of cyanobacteria. The average molecular weight of each sample detected by Orbitrap high-resolution mass spectrometer increases slightly and the DOM increase aromaticity in the end. In this study, the molecule of Carboxyl-Rich Alicyclic Molecules (CRAM) is difficult to be done by photodegradation and biodegradation in the early periods, but some molecules of CRAM are selectively degraded by microorganisms in the final period. The growth of cyanobacterial lead to increasing the concentration of protein-like and carbohydrate-like molecule of DOM in the water. In the final stage, the molecule group of CHO disappear significantly and the molecule group of heteroatomic group increase.

Method for early diagnosis of verticillium wilt in cotton based on chlorophyll fluorescence and hyperspectral technology

Early and accurate detection of verticillium wilt (VW), the most common and devastating disease of cotton, is essential to prevent the spread of VW. However, it remains challenging to achieve accurate detection of VW in cotton before symptoms appear after infection with Verticillium dahliae (asymptomatic phase). This study evaluated the feasibility of detection of VW in the asymptomatic phase based on cotton main stem leaf chlorophyll fluorescence parameters (CFPs) and spectral features extracted based on continuous wavelet transform (CWT) in two different environments. The aim was to achieve accurate detection of cotton VW in the asymptomatic period by convenient methods. Hyperspectral data of cottons inoculated with V. dahliae were collected at different times, and the CFPs of main stem leaves were measured simultaneously. After preprocessing the hyperspectral data with CWT, common wavelet features for all spectral acquisition days and sensitive CFPs were extracted based on the results of ANOVA. Then, the variance inflation factor combined with least absolute shrinkage and selection operator (LASSO-VIF) was used to select the optimal wavelet features. Finally, the support vector machine, logistic regression, and k-nearest neighbors (KNN) were used to construct the models for detecting VW in asymptomatic leaves based on CFPs and optimal wavelet features, and the accuracy of the models were compared.The results showed that the CFPs were significantly affected 24 h after V. dahliae infection. V. dahliae infection reduced the maximum quantum yield (Pm') of photosystem II (PSII) and increased non-photochemical quenching (NPQt) in cotton leaves. Compared with the raw spectrum, the spectral features in the near-infrared region (800–1350 nm) extracted based on CWT could accurately reflect the subtle changes of leaves in the asymptomatic phase. Besides, compared with CFPs, the 4–5 wavelet features selected based on the LASSO-VIF were more helpful to accurately identify asymptomatic cotton leaves infected with V. dahliae, with an accuracy greater than 80 % and a Kappa coefficient higher than 0.6. Among them, the average accuracy of the logistic regression model based on wavelet features was as high as 90.62 %. The results of this study confirm the changes in CFPs in cotton leaves in the VW-asymptomatic period and the feasibility of accurate identification by using wavelet features. This study will provide a reliable reference for accurate large-scale identification of V. dahliae infection in cotton in the asymptomatic phase.

Spatial-temporal distribution and source apportionment of riverine dissolved organic carbon in the Miyun section of the Chaobai River in Beijing, China

Dissolved organic carbon (DOC) is indicative of water quality in drinking source water and has an impact on drinking water treatment. Exploring occurrence of DOC in drinking source water is of great significance for the drinking water safety in Beijing. This study elucidated spatial-temporal DOC dynamics in the Miyun section of Chaobai River in Beijing of China and identified sources of DOC based on DOC fluorescent spectral characteristics. Results showed that the average riverine DOC concentration was 30.60 mg/L. DOC concentrations in the Miyun section of the Chaobai River were 30.40, 30.24, and 31.09 mg/L in spring, summer and autumn, respectively. DOC concentrations at the three segments of the Miyun section of the Chaobai River (the Chaohe River, the Baihe River and the Chaobai River) were 29.93, 30.29 and 32.57 mg/L, respectively. Land use contributed to DOC variations rather than season and river segment. Significant increases in DOC concentration were observed in river water flowing through farmland and urban areas, and DOC concentration presented the highest after flowing through the farmland area. The results of FI, HIX and BIX showed that DOC mainly came from endogenous sources such as aquatic biological activities, and was less affected by terrestrial inputs. Special attentions ought to be paid on prevention and control of endogenous DOC inputs.

New perspective on effect of β-cyclodextrin on nitrification-denitrification and denitrification phosphorus removal in biogenic manganese oxides driven moving bed biofilm reactor: Performance evaluation, microbial community and process

Effect of β-cyclodextrin (β-CD) on simultaneous removal of NH4+-N, NO3–-N, COD, and phosphorus (P) in biogenic manganese oxides (BioMnOx) driven moving bed biofilm reactor (MBBR) was investigated. 58.64% and 86.32%, 79.65% and 98.39%, 62.45% and 97.30%, and 24.80% and 95.90% of TN and COD were removed in phases I-IV, indicating that simultaneous nitrification and denitrification (SND) efficiencies were 75.44%, 83.91%, 72.71%, and 35.83%, respectively. Composition and fluorescence spectral characteristics of extracellular polymeric substance (EPS) were evaluated including the removal kinetics of TN and COD. Metabolic activity of Mn2+, decolorization performance of BioMnOx, and reactive oxygen species (ROS) characteristics were determined in biofilm. Furthermore, intermediate Mn3+ and BioMnOx concentration were analyzed. Finally, the removal process of nitrogen (N) and P was proposed based on characterizations of elemental characterization, electrochemistry, and microbial community. This study provides new insights into the N and P removal mediated by BioMnOx and β-CD.

Controllable sidebands of resonance fluorescence of a two-level system driven by bichromatic field

Strong polychromatic driving reshapes characteristics of the resonance fluorescence spectrum of a two-level system. Employing bichromatic driving feild with a low beat-frequency smaller than the emission rate of the system we demonstrate the exotic features of the fluorescence spectrum calculated by the numerical Floquet-Liouville approach and analytical method. It is found that fluorescence spectrum possesses two broadened sidebands in the place of the Rabi sidebands under certain conditions. Moreover, the heights and widths of the sidebands can be controlled by tuning the driving parameters. The properties of the spectrum is determined by the transitions between the Floquet states in a rotating frame. The broadened sidebands result from the quasi-continuous quasienergy spectrum which happens with steering the beat frequency lower. The present study provides insights into the Floquet engineering of the fluorescence spectral features with polychromatic excitation fields.

Fluorescence Spectral Characteristics of Soil Dissolved Organic Matter in Zhengyangguan, Middle Reaches of Huaihe River Basin

Fluorescence Spectral Characteristics of Soil Dissolved Organic Matter in Zhengyangguan, Middle Reaches of Huaihe River Basin

Dual-strategy of Eu2+ sensitization and Ca2+ substitution improves the luminescence properties of phosphor Sr2La8(SiO4)6O2:Eu

A series of novel orange-red phosphors Sr 1.9- x Ca x La 8 (SiO 4 ) 6 O 2 :0.1Eu (2+,3+) (0≤ x ≤ 1.9, Δ x= 0.3) were successfully prepared via high-temperature solid-state reaction. The crystal structure, fluorescence spectral characteristics, thermal stability, fluorescence lifetime, morphological characteristics and Eu valence state of the phosphor were systematically studied. The successful introduction of Eu 2+ broadened the excitation spectrum of Sr 1.9- x Ca x La 8 (SiO 4 ) 6 O 2 :0.1Eu (2+,3+) by more than 100 nm and increased the fluorescence intensity by 200%, realizing the energy transfer between Eu 2+ and Eu 3+ . The fluorescence intensity of Sr 0.4 Ca 1.5 La 8 (SiO 4 ) 6 O 2 :0.1Eu (2+,3+) is increased by 551% through the Ca 2+ substitution strategy, and the Ca 2+ enters the matrix lattice, which promotes the reduction of Eu 3+ to Eu 2+ and improves the energy transfer efficiency. The emission intensity of Sr 0.4 Ca 1.5 La 8 (SiO 4 ) 6 O 2 :0.1Eu (2+,3+) remained at 70.29% at 418 K. The color coordinates of Sr 1.9- x Ca x La 8 (SO 4 ) 6 O 2 :0.1Eu (2+,3+) are all located in the orange-red region, the color coordinates are about (0.59, 0.40), and the color temperature are about 2100 K. Therefore, the excellent optical properties of this series of phosphors make them have potential practical value in the LED field.

Conformation-dependent photophysical properties of butadiyne-linked π-extended BODIPY dimers

A hitherto unknown butadiyne-linked BODIPY dimer (4) has been synthesized under the conventional Glaser coupling reaction conditions using the ethynyl-substituted pyrrolyl-BODIPY (2) prepared by gold-catalyzed C-H alkynylation. Due to the [Formula: see text]-extended structure of the BODIPY chromophore in 4, a characteristic broad absorption band in the near-infrared (NIR) region has emerged. Upon photoexcitation, the environment-dependent fluorescence spectral features were observed. The fluorescent response varied with solvents, viscosity, and temperature, which was found to originate from the conformational changes between the coplanar and twisted conformers in the otherwise rigid butadiyne-bridged dimer 4. Therefore, the BODIPY dimer 4 would be a potential NIR fluorescence material for use in the probes responding to the distinct viscous environment in biological tissues.

Fluorescence Lifetime and Spectral Characteristics of Subretinal Drusenoid Deposits and Their Predictive Value for Progression of Age-Related Macular Degeneration.

To measure fundus autofluorescence (FAF) lifetimes and peak emission wavelengths (PEW) of subretinal drusenoid deposits (SDD) in age-related macular degeneration (AMD) and their development over time. Fluorescence lifetime imaging ophthalmoscopy (FLIO) was performed in 30 eyes with optical coherence tomography (OCT)-confirmed early or intermediate AMD and SDD. Contrasts of mean lifetimes in short- (SSC) and long-wavelength channels (LSC), PEW, and relative fluorescence intensity were determined as differences of the respective measures at individual SDD and their environment. Measurements were made at baseline and at follow-up intervals 1 (13-36 months) and 2 (37-72 months), respectively. Of 423 SDD found at baseline, 259, 47, and 117 were hypoautofluorescent, isoautofluorescent, and hyperautofluorescent, respectively. FAF lifetimes of SDD were significantly longer than those of their environment by 14.5 ps (SSC, 95% confidence interval [CI], 13.3-15.7 ps) and 3.9 ps (LSC, 3.1-4.7 ps). PEW was shorter by 1.53 nm (1.07-1.98 nm, all contrasts P < 0.001) with higher contrasts for hyperfluorescent SDD. Over follow-up, SDD tended to hyperautofluorescence (relative intensities increased by 3.4% [95% CI, 2.9%-4.1%; P < 0.001] in follow-up 2). Hyperautofluorescence was associated with disruption of the ellipsoid zone on OCT. Disease progression to late-stage AMD was associated with higher lifetime contrast in SSC (15.9ps [14.2-17.6 ps] vs. 11.7 ps [9.9-13.5 ps], P < 0.001) at baseline. SDD show longer FAF lifetimes and shorter PEW than their environments. A high lifetime contrast of SDD in SSC might predict disease progression to late-stage AMD.

Interaction of 3-(1H-tetrazol-5-yl) Coumarin With Bovine Serum Albumin and Calf Thymus DNA: Deciphering the Mode of Binding by In Vitro Studies

Background: Coumarins comprise a large family of heterocyclic compounds with a benzo-a-pyrone moiety. Objectives: This study aimed to analyze the binding affinity of 3-(1H-tetrazol-5-yl) coumarin to bovine serum albumin (BSA) and calf thymus DNA (Ct-DNA) using fluorescence spectroscopy. The quenching of fluorescence was recognized during the interaction between 3-(1H-tetrazol-5-yl) coumarin and BSA, followed by a static mechanism. Methods: The hydrogen bonds, hydrophobic interactions, and Vander Waals forces were regarded as the principal part in the 3-(1H-tetrazol-5-yl) coumarin and BSA complexation process. The fluorescence spectral characteristics demonstrated an enhancement in fluorescence intensity of the 3-(1H-tetrazol-5-yl) coumarin in the presence of ct-DNA solution. Results: The experimental results indicated that the 3-(1H-tetrazol-5-yl) coumarin binds to DNA via interjection, hydrogen bonds, and Vander Waals forces. This work illustrated that BSA fluorescence was quenched by 3-(1H-tetrazol-5-yl) coumarin via a static mechanism and the ct-DNA fluorescence enhancement by 3-(1H-tetrazol-5-yl) coumarin was a static process. The secondary structure of proteins changed upon drug binding. Conclusion: It is deduced that 3-(1H-tetrazol-5-yl) coumarin represents a higher binding affinity to DNA compared to BSA. This finding can be useful in designing more effective new drugs with fewer side effects.

Structural, vibrational, fluorescence spectral features, Hirshfeld surface analysis, docking and drug likeness studies on 4-(2-bromo-4-methyl-phenoxymethyl)-6-methyl-coumarin derivative: Experimental and theoretical studies

This work is an endeavour to determine the structural, vibrational (IR), absorption, fluorescence spectral and chemical reactivity studies on 4-(2-bromo-4-methyl-phenoxymethyl)-6-methyl-coumarin (4BMPC) molecule. Basically, we have focused on the experimental and computational studies on 4BMPC. The computational studies have been conducted using two different methods such as DFT/B3LYP/6-311++G (d, p) and DFT/PBEPBE/6-311++G (d, p) basis sets with the aid of optimized geometrical parameters. The absorption and fluorescence emission spectra are obtained in various solvents with different solvent parameters, viz., dielectric constant ε and refractive index n. The ground state and excited state dipole moments are experimentally determined by solvatochromic methodology evolved by Bilot-Kawaski, Kawaski-Chamma-Viallet, and Bakshiev.Further, Molecular Electrostatic Potential (MEP) analysis, Frontier Molecular Orbital (FMO) analysis and Natural Bond Orbital (NBO) studies have been conducted. Hirshfeld surfaces analysis reveals intermolecular interactions. Fukui function is used to investigate the local reactivity parameter. Molecular docking is also carried out to predict the preferred binding orientations with the protein surface. Further, the drug likeness properties are also investigated.

Fluorescence Spectral Characteristics of Dissolved Organic Matter in Songhua Lake Sediment

Dissolved organic matter (DOM) has a significant impact on the main pollution indicators of the lake (e.g., COD), and sediment is the main source of pollution in the lake. Research on the fluorescence spectral characteristics of DOM in sediments is important to reveal the mechanism of lake pollution. In this study, sediments were collected from 20 sites in Songhua Lake. The DOM components in the sediment were analyzed using the excitation emission matrix-parallel factor analysis (EEM-PARAFAC) technique, and the properties of the sediment DOM were clarified via spectroscopy. Additionally, the relationship between DOM and eutrophication of the water column was explored. The results showed that four components were identified from the sediment DOM of Songhua Lake:humic-like C1 (330/415 nm), C2 (255/440 nm), C3 (365/470 nm), and protein-like C4 (280/355 nm). The high HIX and low BIX indicated that the source of sediment DOM was mainly terrestrial and included some biological sources. The spatial distribution of the fluorescence intensity of the four components was relatively similar, showing that the fluorescence intensity was higher in the upstream (S1-S7) than that in the downstream (S8-S20). The massive deposition of suspended particulate matter (SPM) carried by the three rivers (Huifa River, Songhua River, and Jiao River) was the main reason for this spatial distribution. Eutrophication status in the water column of Songhua Lake was similar to the fluorescence intensity distribution of sediment DOM. Meanwhile, there was a strong correlation between eutrophication level and sediment DOM fluorescence intensity in the downstream water column of Songhua Lake.

DNA-Templated Modulation in the Photophysical Properties of a Fluorescent Molecular Rotor Auramine O by Varying the DNA Composition.

This work delineates an integrative approach combining spectroscopic and computational studies to decipher the association-induced fluorescence properties of a fluorescent molecular rotor, viz., auramine O (AuO), after interacting with 20-mer duplex DNA having diverse well-matched base pairs. While exploring the scarcely explored sequence-dependent interaction mechanism of AuO and DNA, we observed that DNA could act as a conducive scaffold to the formation of AuO dimer through noncovalent interactions at lower molecular density. The photophysical properties of AuO depend on the nucleotide compositions as described from sequence-dependent shifting in the emission and absorption maxima. Furthermore, we explored such DNA base pair-dependent fluorescence spectral characteristics of AuO toward discriminating the thermodynamically most stable single nucleotide mismatch in a 20-mer sequence. Our results are interesting and could be useful in developing analogues with further enhanced emission properties toward mismatched DNA sequences.

Evaluating the Conservation State of Naturally Aged Paper with Raman and Luminescence Spectral Mapping: Toward a Non-Destructive Diagnostic Protocol.

Micro-Raman and luminescence spectroscopy were combined with morphological analysis to study the conservation state of differently degraded paper samples, dated from 1873 to 2021. The aim of the work reported in this paper was to obtain ageing markers based on variations of Raman and fluorescence spectral features. Raman and luminescence spectra were acquired by scanning non-printed areas of books, and Raman and fluorescence maps were built by contrasting spectral parameters point by point, obtaining a micron-scale space resolved imaging of the degradation pattern. Complementary information on paper morphology and surface compactness were obtained by high-resolution scanning electron and atomic force microscopy. The proposed non-destructive procedure is particularly interesting for precious and ancient samples to analyze their degradation processes and to evaluate the performance and effectiveness of restoration treatments.

Improved stability of all-inorganic perovskite nanocrystals in hierarchical ZSM-5 zeolites for multimodal applications

All-inorganic perovskite quantum dots (PQDs) CsPbX3 (X = Cl and Br) are expected a new generation of promising luminescent materials with narrow-band emissions, color-tunability, and high photoluminescence quantum yields (PLQYs), but the instability towards humid environments and high temperatures restrict their practical applicability. In this work, a hierarchically structured zeolite (HSZ) of ZSM-5 (Si/Al = 50) featured micro-mesoporous cross-linked architecture was applied to encapsulate CsPbX3 PQDs through a simple thermal diffusion strategy. The luminescence performances of CsPbX3 PQDs hybridized ZSM-5 nanocomposites can be optimized in the hierarchical micro-mesoporous structures. Particularly, the CsPbBr3-HSZ ZSM-5 composite calcined at 700 °C exhibited highly water-stable luminescence performance with a full-width at half-maximum (FWHM) of 22 nm and a high photoluminescence quantum yield (PLQY, 62%), maintaining 92% of the initial emission intensity even after 100 days of immersion in water. The highly water-resistant and stable luminescent performance of the composite was attributed to the interconnected micro-mesoporous network of HSZ ZSM-5, in which micropores provide a shielding wall to isolate the CsPbBr3 PQDs from the external environment and mesopores help to promote the diffusivity of precursors towards the successful space-confinement of CsPbX3 (X = Cl and Br) PQDs. The temperature-dependent fluorescence intensity and spectral shift characteristics of CsPbBr3-HSZ ZSM-5 composite afford its capacity acting as dual-mode optical thermometers, and the water-stable latent fingerprint identification has been also demonstrated by applying the CsPbBr3-HSZ ZSM-5 nanocomposite.

Fluorescence spectrometry based chromaticity mapping, characterization, and quantitative assessment of dental caries

PurposeDental caries detection, especially the accurate detection of early caries, facilitates prompt interventions. It is reasonably common to use fluorescence imaging for classification and evaluation of caries, but lacks a quantitative, precise and easy-to-use characterization for practical applications. In this study a quantitative approach for caries stage detection by correlating caries spectral and chromatic features was examined. MethodsA 405 nm LED light source was used as the excitation source. A hyperspectral imaging camera is employed to collect 336 spectral data of different caries stages. Four critical intervals for different stages of caries were extracted by fluorescence spectral features. The mapping relationship between caries spectral and chromatic features was established by Fast Formula Fitting (FFF) and Neural Network Fitting (NNF) methods. ResultsThe 470–780 nm spectral power distribution was proved to be the best matching color waveband guiding the selection of filters in future instrument development. The correlation coefficients for the two fitting methods were 0.990 and 0.999, respectively. Both methods achieved caries stage prediction at the pixel level with high accuracy using color information. The visualization region in the chromaticity diagram was created. ConclusionsThis quantitative method enables accurate prediction of caries on the entire tooth surface and facilitates the development of portable and low-cost caries detection instruments.

Analysis of the Three-Dimensional Fluorescence Spectroscopy Characteristics of Dissolved Organic Matter in Groundwater from a Subtropical Cave in Dry Season—Daxiao Cave in South China Karst

Groups in dissolved organic matter (DOM) emit fluorescence information at characteristic wavelengths when irradiated by excitation waves, which can reveal the geochemical behavior of dissolved organic matter in the environment and its sources, but there are few relevant studies in cave groundwater systems. In order to investigate the relationship between drip hydrochemistry characteristics and DOM in cave systems after subsurface leakage, in this study, from the perspective of dissolved organic matter in the karst cave water system, the groundwater in the dry season of Daxiao Cave was selected as the research object. Five drip points and one water pool (DX-1, DX-2, DX-3, DX-4, DX-5, and DX-C) in Daxiao Cave were monitored and consecutively sampled for four months. The parallel factor analysis method (PARAFAC), three-dimensional (3D) fluorescence parameters, and excitation-emission matrix fluorescence spectroscopy (EEM), combined with the hydrochemistry characteristics of the drip water and correlation analysis, were used to analyze the 3D fluorescence spectral characteristics of the DOM of the drip water of Daxiao Cave and their influencing factors. The results show that (1) the hydrochemistry type of the drip water in Daxiao Cave was within the Ca–Mg–HCO3 type, and Ca2+, Mg2+, and HCO3− were the dominant ions in Daxiao Cave; (2) the fluorescence fractions of drip water in dry season caves were dominated by C1 (humus-like), C2 (tryptophan-like), and C3 (tyrosine-like), and the fluorescence fractions of drip water DOM were controlled by protein fluorophores; (3) the DOM in the drip water of Daxiao Cave in the dry season was controlled in part by subsurface leakage and was largely the result of microbial degradation; and (4) the DOM of the drip water may be influenced by the chemical composition of the water, but the exact process is not clear.

Assessing the potential to use CDOM as an indicator of water quality for the sediment-laden Yellow river, China

Chromophoric dissolved organic matter (CDOM) in rivers is mainly affected by natural conditions and human activities and can reflect the watershed pollution status to a certain extent. The Yellow River is one of the largest contributors to the global riverine sediment flux from the land to ocean, and there is a paucity of information on how the optical properties of CDOM have the potential to serve as an indicator of water quality for the sediment-laden Yellow River. In this study, a three-dimensional fluorescence parallel factor (PARAFAC) analysis method was applied to investigate the seasonal and spatial variations in CDOM fluorescence components and spectral characteristics from the source region to the estuary in the mainstream of Yellow River. The relationships of CDOM with water quality indicators and trophic state were also analyzed. Six PARAFAC components (C1–C6) were identified and grouped into two categories: humic-like components (C1–C4), which accounted for 85.8 %, and protein-like components (C5 and C6), which accounted for only 14.2 %. The CDOM components, spectral parameters, and their clear correlations with the main ions (Na+ and Cl−) all indicated that the humic-like components may be primarily derived from nonpoint source erosion, and the protein-like components were mainly derived from point source discharges in the watershed. The combination of the CDOM absorption coefficient at 254 nm (a(254)), spectral slope ratio (SR), specific UV absorbance SUVA254, and fluorescence index (FI) had a good predictive ability for the key water quality indicators (total nitrogen (TN), dissolved total nitrogen (DTN), total phosphorus (TP), dissolved total phosphorus (DTP), and chlorophyll a (Chl a)) and trophic state index (TSI). Therefore, some fluorophores and UV spectral parameters of CDOM in the Yellow River can be used for rapid water quality monitoring and pollution source indication, especially pollutants related to nitrogen and phosphorus nutrients in the basin.