Three-dimensional Excitation-emission Matrix Spectroscopy Research Articles

Characteristics of Soil Organic Carbon and Its Influencing Factors of Different Plant Communities in the Yellow River Delta

Changes in soil organic carbon （SOC） are of great importance to the evolution of soil quality. The distribution characteristics of soil organic carbon （SOC）, easily oxidizable organic carbon （EOC）, dissolved organic carbon （DOC）, and particulate organic carbon （POC） were investigated in the 0-50 cm soil layer of the Phragmites australis, Suaeda salsa, and Tamarix chinensis communities of the supratidal zone in the Yellow River Delta as the research subjects. Then, the composition and sources of soil dissolved organic matter （DOM） were analyzed based on the UV-vis spectroscopy, three-dimensional excitation emission matrix spectroscopy, and parallel factor analysis （PARAFAC）. Finally, the key factors affecting the characteristics of soil organic carbon and DOM fractions of different plant communities were finally revealed in combination with the physicochemical properties of the soil. The results showed that： ① Comparing different communities, the S. salsa community had the highest ω（SOC） at 7.53 g·kg-1, the T. chinensis community had the highest ω（DOC） at 0.98 g·kg-1, and the P. australis community had significantly higher ω（EOC） and ω（POC） than those of the S. salsa and T. chinensis communities at 1.47 g·kg-1 and 0.65 g·kg-1, respectively. The vertical distribution showed a tendency to decrease with deeper soil layers, except for POC concentration. ② The main components of soil DOM of the P. australis, S. salsa, and T. chinensis communities were humus, protein-like substances, and fulvic acid-like substances, of which exogenous components accounted for 55.80%, 56.41%, and 52.81% in the above communities, respectively. ③ Comparing different communities, the humification degree of the P. australis community was significantly higher than that of the S. salsa and T. chinensi communities, but its aromaticity and proportion of biological sources were significantly lower than those of the T. chinensi community. On the vertical profile of the soil, DOM aromaticity and humification degree gradually increased with the deepening of the soil layer, and the deeper soils were mainly dominated by small molecular weight DOM with a lower proportion of hydrophobic fraction. ④ Redundant analysis showed that N （P<0.01）, NO2--N （P<0.01）, and NH4+-N （P<0.05） were the key factors affecting the changes in soil organic carbon and DOM fractions.

Effect of hydrothermal temperature on the optical properties of hydrochar-derived dissolved organic matter and their interactions with copper (II)

Hydrothermal carbonization (HTC) has been regarded as a promising technique for turning wet biomass into hydrochar due to its low energy consumption, low exhaust gas emissions, etc. In addition, hydrochar is an important source of dissolved organic matter (DOM), which plays a crucial part in the migration and destiny of pollutants in the environmental medium. However, there are limited studies that focus on the factors that influence the formation of DOM in hydrochar, such as hydrothermal temperature. Therefore, the current study comprehensively characterized the optical properties of DOM within hydrochar derived from sawdust (HDOM) under different hydrothermal temperatures (150–300 °C) by Ultraviolet–visible (UV–Vis) and fluorescence spectroscopy, as well as its complexation characteristic with Cu(II). The findings revealed that the organic carbon content of HDOM reached a peak of 37.3 mg L−1 when the temperature rose to 240 °C and then decreased as the temperature increased. UV–Vis spectroscopy analysis showed that the absorption capacity of HDOM at 275 nm increases with temperature and reaches a maximum value at 240 °C, indicating that high temperature promotes the formation of monocyclic aromatic compounds. High temperature enhances the aromaticity, hydrophobicity, and humification degree of HDOM, thus improving its stability and aromaticity. The E3/E4 ratios are all greater than 3.5, confirming that the main component of HDOM is fulvic acid, which corresponds to 3D-EEM and Pearson's correlation coefficient analysis. The humification index (HIX) of HDOM increased with the rise in hydrothermal temperature (150–240 °C), as observed by the three-dimensional excitation-emission matrix spectroscopy (3D-EEMs). After reaching its peak at 240 °C, the HIX value gradually dropped in line with the trend of the DOC change. Moreover, the bioavailability (BIX) value of DOM was all high and greater than 1, indicating all the HDOM are readily bioavailable. Two microbial humic substances (C1 and C4), a humic-like substance (C2), and a protein-like substance (C3) were discovered in DOM by integrating 3D-EEMs with parallel factor analysis (PARAFAC). Their fluorescence intensity decreases as the Cu(II) concentration increases, indicating the formation of complexes with Cu(II). As the temperature rises, the binding ability of DOM and Cu(II) changes significantly, reaching the optimum at 300 °C. Meanwhile, the substance C2 has the strongest binding ability with Cu(II). This research emphasizes the significance of spectroscopy analysis in determining the evolution of hydrochar-derived DOM, the potential for heavy metal binding and migration, and its characteristics and features.Graphical

Rational regulation of 3D N-doped carbon macro-architectures toward low-temperature plasma catalysis: The roles of nitrogen content and hierarchical porous structure

The application of low-temperature plasma technology with optimized catalysts in water treatment has shown a good application prospect. However, the relationships between catalytic performance and composition (N atom-doping) and structure (hierarchical porous) of catalysts is still unclear. Here, 3D N-doped carbon macro-architectures is designed by thermolysis of energetic Zn-MOF, where triazole ligand with ultra-high nitrogen content provided the possibility for effective nitrogen doping and creation of hierarchical porous structure. In the DBD system, a series of energetic MOF-derived carbon (EMC-x) catalysts with different pyrolysis temperatures (from 700 to 1000 °C) were prepared, and the composition/structure-effective relationship was investigated in detail. Degradation mechanisms and pathways were analyzed by bursting experiments, quantitative detection of H2O2 and O3, three-dimensional excitation-emission matrix spectroscopy (3D-EEM), LC-MS. The results confirmed that EMC-10 with high nitrogen content and hierarchical porous structure has a wide range of applications in synergistic plasma removal of TTCH from water bodies.

Preparation of a g-C3N4/Ag3PO4 composite Z-type photocatalyst and photocatalytic degradation of Ofloxacin: Degradation performance, reaction mechanism, degradation pathway and toxicity evaluation

In this study, a g-C3N4/Ag3PO4 composite Z-heterojunction photocatalyst was prepared with a simple in situ deposition method, and was first applied to the degradation of Ofloxacin (OFX). When the theoretical g-C3N4 to Ag3PO4 mass ratio was 1:10 (denoted as AC-10), the OFX degradation was optimal, and the degradation efficiency reached 71.9 % within 10 min. Steady state fluorescence emission spectroscopy (PL), electrochemical impedance spectroscopy (EIS), transient photocurrent (I-t) and N2 adsorption-desorption (BET) studies showed that AC-10 had the best charge separation efficiency and highest specific surface area. Additionally, the effects of AC-10 dosage, OFX concentration, pH value, anions, humic acid and water source on the degradation process were also studied. A cycling experiment showed that AC-10 exhibited good stability. Three-dimensional excitation-emission matrix spectroscopy (3D EEMs), LC-MS data and ECOSAR models were used to explore the process for degradation of OFX and predict the biotoxicities of byproducts, and these results indicated that the catalyst was environmentally friendly. In addition, electron spin resonance (ESR) experiments and capture of the active species showed that photogenerated holes (h+) played a major role in the reaction. Finally, the optical properties and the energy band structure of the catalyst were analyzed by UVvis diffuse reflectance spectroscopy (DRS) and Mott-Schottky (M-S) methods, and a Z-type heterojunction charge transfer mechanism was proposed.

Accelerating anammox nitrogen removal in low intensity ultrasound-assisted ASBBR: Performance optimization, EPS characterization and microbial community analysis

Efficient enrichment of slow-growing anammox species is essential for rapid start-up and stable operation of high-rate anammox reactors. Herein, a low intensity ultrasound (LIU) was introduced into anaerobic sequencing batch biofilm reactors (ASBBRs) to enhance anammox nitrogen removal from nitrogen-rich wastewater. Operation results demonstrated that the maximum total nitrogen (TN) removal efficiency of 91.5% were achieved under the optimal ultrasonic parameters (32.7 °C water temperature, 0.18 W/cm2 ultrasonic intensity and 25.7 min ultrasonication time). Moreover, significant increases of extracellular polymeric substances (EPS) components and contents were observed via the ultrasonication stimulation. A close correlation between nitrogen removal and shifts in transformation and intensity of spectrum peaks was also verified by three-dimensional excitation-emission matrix spectroscopy (3D-EEM) analysis. High-throughput sequencing revealed that the relative abundance of Candidatus Kuenenia as the key anammox consortium significantly increased after applying optimal ultrasonication condition. Furthermore, enhancement mechanisms and future prospect of the LIU-assisted anammox process was elucidated and discussed. This research provides a viable and promising acceleration strategy for anammox-based process in practice.

Combined forms of Pb and its detoxification and absorption in Cladophora rupestris subcells

This study aims to analyze the combined form, detoxification, and adsorption mechanism of Pb in Cladophora rupestris subcells. The chemical form analysis at different concentrations (0, 0.5, 1.0, 2.5, 5.0, 7.5, and 10 mg/L) indicated that most of the Pb (37%–76%) were integrated with oxalate and undissolved phosphate, which were important to the detoxification of C. rupestris. The characterization of Pb (0, 0.5, and 5.0 mg/L) at the subcellular was conducted via Fourier-transform infrared spectroscopy (FTIR), Three-dimensional excitation-emission matrix spectroscopy (3D-EEM), and protein secondary structure fitting. Results revealed that Pb-polysaccharides ((C6H5)–OO-Pb-OH, C-O-Pb, and symmetric Pb-O-Pb), Pb-functional-groups ((C6H5)–COO-Pb and (C6H5)-P = O-Pb), and Pb-protein complexes (OH-C7H6-CN-Pb-COOH, C9H10-NH-CN-C = O-Pb, Pb-S-C, and Pb-S) were formed. The cell wall produced transport proteins, such as metallothionein and glutathione, which bound and helped Pb2+ enter the cell. After entering the soluble fraction, the Pb–organic acid ((C6H5)–COO-Pb, (C6H5)-O-Pb, and (C6H5)-P = O-Pb) and Pb-sulfhydryl compound (Pb-S-C/Pb-S) assumed the most important role in resisting the toxicity of Pb2+. Pb2+ was absorbed in the organelle and formed (C6H5)-C-O-Pb and (C6H5)-P = O-Pb, and complexed with protein (Pb-C-N) when treated with 5.0 mg/L Pb. Results could help understand the role of subcellular fraction in the algal adaptation to stressful heavy metal conditions.

Comprehensive assessment of flocculation conditioning of dredged sediment using organic polymers: Dredged sediment dewaterability and release of pollutants

Dredged sediment contains various contaminants that are released during the process of dewatering and subsequent utilization. In this study, two organic polymers—chitosan (CS) and cationic polyacrylamide (CPAM) both in samples of varying molecular weights (MWs)—were used as flocculants to improve dewatering and rheological behaviors of dredged sediment, and floc properties were characterized to unravel the mechanisms of flocculation treatment. Moreover, pollutant transfer and release in the flocculation-dewatering process was investigated. Compared to CPAM, CS had better performance in dredged sediment dewatering, and more compact flocs were produced after treatment. The flocculated sediment belonged to the type of yield dilatant fluid and showed good shear resistance. Three-dimensional excitation–emission matrix spectroscopy and PARAFAC showed that protein-like substances were removed after treatment. The MW of CS had insignificant effects on flocculation performance, whereas CPAM removal efficiency for protein-like substances was increased at higher MWs, which may be related to the adsorption bridging effect of CPAM polymer chains. There were significant correlations between the dewatering performance of sediments, MW distribution of organics and rheological properties. CS and CPAM treatments caused the transformation of Fe/Al-P into CaP, which could reduce phosphorus release and its ecological risk. The flocculants contributed to the formation of carbonate-bound forms of As, Cr, Pb, and Ni. Ecological risk assessment results of the geo-accumulation index showed that medium- and low-MW CS reduced risk of sediment contamination, whereas CPAM and high-MW CS increased the ecological risk. CS had a greater effect on the release of VOCs than CPAM, with an increased release of total VOCs at higher flocculant MWs. The study was helpful to understand the dewatering mechanism of dredged sediment and provided a new strategy for pollution release management in sediment dewatering.

Pretreatment of landfill leachate in near-neutral pH condition by persulfate activated Fe-C micro-electrolysis system

In this study, a novel persulfate combined with iron-carbon microelectrolysis (PS-ICME) system was explored to pretreat the landfill leachate. In the static batch experiments, response surface methodology (RSM) was used to determine the relationship between three independent variables (pH, the ratio of iron to carbon (Fe-C ratio), persulfate dosage) and response values (Chemical oxygen demand (COD) removal efficiency). Experimental results showed that the COD removal efficiency reached to 62.91% under the optimal conditions: initial pH 7, Fe-C ratio 3, and persulfate dosage 85 mM. The dissolved organic matter (DOM) in landfill leachate was characterized by three-dimensional excitation-emission matrix spectroscopy (3D-EEMs). Combined with electron spin resonance (ESR) spectrum investigation, the enhanced mechanism for landfill leachate pretreated by PS-ICE in near-neutral pH was elucidated. In the column continuous flow experiment, it had been confirmed that dissolved oxygen plays an important role in the PS-ICME system. Based on the above conclusions, PS-ICME system has a satisfactory performance on pretreatment of landfill leachate.

Optimization and mechanism studies on cell disruption and phosphorus recovery from microalgae with magnesium modified hydrochar in assisted hydrothermal system

Considering the phosphorus (P) reserve state and its value, recovery of P from microalgae has become a popular topic. In this study, an integrated system of a hydrothermal process for microalgae cell disruption to release P and magnesium modified hydrochar adsorption to capture P was set up. Emission scanning electron microscopy with Energy Dispersive X-ray spectroscopy and Three-Dimensional Excitation Emission matrix spectroscopy with parallel factor analysis were applied to evaluate the P release process from microalgae and found the optimal breaking-wall condition (P release 90.5%, hydrothermal digestion mixture of H2O2 and NaOH at 348 K). Parallel factor analysis showed there was a close relationship between P and humic-like substance. Hydrochar loaded with magnesium exhibited a strong affinity for P, with maximum capacity 89.61 mg/g at 318 K. The P adsorption fitted pseudo-second-order kinetic and Langmuir models. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were applied to reveal the mechanism of hydrochar modification and adsorption. It showed that Mg is loaded on the surface of hydrochar by electrostatic attraction and electron transfer with the carboxylic acid. P absorption was reached through anion exchange.

Water quality assessment and source identification of water pollution in the Banchengzi reservoir, Beijing, China

Water quality in the Banchengzi reservoir in Beijing has been deteriorating year by year, and it was embodied by increasing concentrations of COD and stable but high levels of total nitrogen. In order to identify the causes and to formulate a strategy for pollution prevention and control, we examined the temporal and spatial variations of water pollution and carried out source identification studies. Routine monthly monitoring data for seven water quality and six hydro-meteorological variables of the Banchengzi reservoir from 2007 to 2012 were analyzed by statistical techniques, including correlation analysis and principle component analysis. In addition, water samples at six different sites in the reservoir were collected and analyzed to investigate the spatial variation of water quality and to further identify the water pollution sources by UV–vis spectroscopy, three-dimensional excitation-emission matrix spectroscopy, and nitrogen stable isotope (δ15N) analysis. The results revealed that dissolved organic matter and nitrogen were the main pollutants and were principally derived from anthropogenic point source pollution in the upper areas, which included domestic sewage and livestock farming. We speculated that the biodegradable organic pollutants from sewage were degraded to form soluble microbial products (SMP) by aerobic microorganisms and that nitrogen pollutants were mostly transformed to nitrate by nitrification. These SMP, nitrate, and other refractory pollutants were carried by the upper stream flowing into the Banchengzi reservoir, where it accumulated. Effective control of point source pollution and upper river ecological restoration should be done to improve the water quality and protect the reservoir.

Zinc ferrite catalysts for ozonation of aqueous organic contaminants: phenol and bio-treated coking wastewater

Abstract The studies in ozonation catalysis present a trend in development of advanced oxidation processes (AOPs) applied to the wastewater treatment. The zinc ferrite (ZnFe 2 O 4 , ZFO) catalysts were synthesized hydrothermally (ZFO-H) and using the citrate sol–gel (ZFO-C) method with their characterization by XRD, Raman spectrum, SEM, XPS and FT-IR techniques. The objectives of this study include examining the performance of the catalysts in oxidation of phenol and pollutants in biologically treated coking wastewater (BTCW), compared to non-catalytic ozonation, and evaluating the ozonation reaction kinetics. The changes in the composition of BTCW on course of treatment were determined by ultraviolet–visible (UV) absorption and three-dimensional excitation–emission matrix spectroscopy (3DEEMs) analyses. The experimental results showed the ZFO-H catalyst accelerating the degradation of phenol for about 1.5 times as compared to non-catalytic ozonation. The catalytic activity of ZFO-H surpassed that of ZFO-C in phenol removal, attributed to the larger contact surface area and higher surface hydroxyl group density. The higher catalytic activity of ZFO-H was also confirmed by the ability of decomposing ozone and generating hydroxyl radicals ( OH). The empirical model developed in the research indicates the catalyst concentration and the ozone concentration to be the most significant factors of the reaction apparent rate; the role of pH appeared to be minor. The presence of catalysts leads also to a higher mineralization efficiency of BTCW pollutants compared to non-catalytic ozonation. The UV and 3DEEMs analysis demonstrated effective removal of the aromatic and conjugated structural compounds in BTCW by catalytic ozonation. The performance of the catalysts is determined primarily by their synthesis method defining the surface properties.

Composition of extracellular polymeric substances in a partial nitrification reactor treating high ammonia wastewater and nitrous oxide emission

The objective of this study was to characterize the composition of extracellular polymeric substances (EPS) during the achievement of partial nitrification and subsequent nitrous oxide (N2O) emission treating high ammonia wastewater. After operation of 120days, the reactor achieved high ammonia removal efficiency and stable nitrite accumulation. The average size of sludge flocs in the reactor increased from 102.6 to 258.5μm. The main compositions of EPS, including protein (PN) and polysaccharide (PS), increased to 65.46±3.27 and 21.63±1.08mg/g VSS, respectively. Results of three-dimensional excitation-emission matrix spectroscopy implied that EPS transferred to tryptophan PN-like and humic acid-like substrates. N2O emission accounts for 11.67% of removed nitrogen during the steady state of partial nitrification reactor. The obtained results could contribute a better understanding the achievement of partial nitrification through the composition changes of EPS, and provide more information to determine nitrogen removal by considering N2O emission.

Characteristics and behavior of dissolved organic matter in the Kumaki River, Noto Peninsula, Japan

Dissolved organic matter (DOM) in river water was studied to understand the transport behavior of DOM in a small watershed with forest and paddy fields. Field experiments were conducted under normal flow conditions in the Kumaki River, which is located in the central part of the Noto Peninsula in Japan, during the period 2009–2010. The concentrations and structural properties of fulvic acid-like components, which are the major components of DOM, were determined using three-dimensional excitation–emission matrix spectroscopy and high-performance size-exclusion chromatography. The relative fluorescence intensity for fulvic acid-like components at an excitation wavelength of 305–335 nm and an emission wavelength of 425–440 nm increased from the upper forest area to the lower paddy field area and increased seasonally in this river system in the following order: winter, autumn, spring, summer. Fulvic acid-like components with a higher molecular weight were observed in the summer samples. These results suggest that higher precipitation and agricultural activity in the summer season increase the amount of fulvic acid-like components with higher molecular weight that are transported from the watershed into the river.

Characterizing the release of different composition of dissolved organic matter in soil under acid rain leaching using three-dimensional excitation–emission matrix spectroscopy

Although excitation–emission matrix spectroscopy (EEMS) has been widely used to characterize dissolved organic matter (DOM), there has no report that EEMS has been used to study the effects of acid rain on DOM and its composition in soil. In this work, we employed three-dimensional EEMS to characterize the compositions of DOM leached by simulated acid rain from red soil. The red soil was subjected to leaching of simulated acid rain of different acidity, and the leached DOM presented five main peaks in its EEMS: peak-A, related to humic acid-like (HA-like) material, at Ex/Em of 310–330/395–420 nm; peak-B, related to UV fulvic acid-like (FA-like) material, at Ex/Em of 230–280/400–435 nm; peak-C and peak-D, both related to microbial byproduct-like material, at Ex/Em of 250–280/335–355 nm and 260–280/290–320 nm, respectively; and peak-E, related to simple aromatic proteins, at Ex/Em of 210–240/290–340 nm. EEMS analysis results indicated that most DOM could be lost from red soil in the early phase of acid rain leaching. In addition to the effects of the pH of acid rain, the loss of DOM also depended on the properties of its compositions and the solubility of their complexes with aluminum. HA-like and microbial byproduct-like materials could be more easily released from red soil by acid rain at both higher pH (4.5 and 5.6) and lower pH (2.5 and 3) than that at middle pH (3.5). On the contrary, FA-like material lost in a similar manner under the action of different acid rains with pH ranging from 2.5 to 5.6.

中国三江平原河川水中の溶存腐植物質の蛍光特性

Dissolved humic substances in the river waters of Sanjiang Plain, which has undergone a land-use change from wetland marsh to cultivated land, were studied by three-dimensional excitation emission matrix spectroscopy and high-performance size exclusion chromatography to characterize the dissolved organic matter in the river systems. River water samples were collected at 14 points from nine rivers in the summer in 2005. Fulvic like fluorescence maxima were detected for the river waters at an excitation wavelength (Ex.) in the range of 315-335 nm and an emission wavelength (Em.) in the range of 410-430 nm and at an Ex. in the range of 235-260 nm and an Em. in the range of 410-440 nm. The relative fluorescence intensity of fulvic like materials in the river waters from wetlands in the August samples was lower than those of the September samples, but that of the river waters from the cultivated area was higher than those of the September samples. The fluorescent properties of humic substances can be divided into three groups on the basis of river water pH, the relative fluorescence intensity of fulvic like materials and its peak positions. These groups correspond to the land-use types such as wetlands, dry lands and their mixture in the watershed of rivers.

Convenient Characterization of Humic Substances in Deep Groundwaters by Three-Dimensional Excitation Emission Matrix Spectroscopy

三次元蛍光分光光度法を溶存有機炭素濃度が1 mg L−1以下と低く，500 mL程度の試料しか採取できない深部地下水に適用し，溶存腐植物質の簡易特性分析法としての有効性を検討した．岐阜県東濃地域の地下水からdiethylaminoethyl（DEAE）-セルロース樹脂等により分離精製した腐植物質（フミン酸，フルボ酸）と地下水の三次元蛍光スペクトルを比較した結果，地下水試料で検出される励起波長300∼320 nm/蛍光波長430 nmの蛍光ピークはフルボ酸様有機物と考えられる．この方法をボーリング孔の4つの深度から採取した地下水に適用した結果，花崗岩の地下水の三次元蛍光スペクトルには堆積岩の地下水に比べて励起波長で25 nm低波長側に蛍光ピークが検出された．また，堆積岩の種類により異なる相対蛍光強度，紫外吸光度比を示した．これらの結果は，三次元蛍光分光光度法が深部地下水中の腐植物質の特徴と濃度に相当する相対蛍光強度を簡易に把握できる有効な分析法であることが示唆される．

Fluorescence Quenching Studies of Eu-Humic Complexes by Three-Dimensional Excitation Emission Matrix Spectroscopy

Fluorescence Quenching Studies of Eu-Humic Complexes by Three-Dimensional Excitation Emission Matrix Spectroscopy

Molecular mass distribution and fluorescence characteristics of dissolved organic ligands for copper(II) in Lake Biwa, Japan

Molecular mass distribution and fluorescence characteristics of organic ligands for copper(II) in freshwater were, for the first time, investigated using ultrafiltration, immobilized metal ion affinity chromatography (IMAC) and three-dimensional excitation-emission matrix spectroscopy (3DEEM). Two types of humic-like fluorescence (Peaks A and B) were found in all molecular ligand fractions, while an additional type of protein-like fluorescence (Peak C) was only observed in the 0.1 μm-GF/F molecular ligand fractions. The Ex/Em maxima of Peak A in the <5 kDa and 0.1 μm-GF/F molecular ligand fractions were blue-shifted (shift towards the shorter wavelength) relative to that in the 5 kDa–0.1 μm fractions. Contributions of total organic ligands were 1.6–4.0% of the bulk dissolved organic matter (DOM) in the original water, as determined by UV absorbance. In the molecular mass distribution of organic ligands, the relative contribution of the fraction with the <5 kDa molecular masses was dominant (67–79%), while 17–30% of the total organic ligands were in the 5 kDa–0.1 μm fraction, leaving 3–6% in the 0.1 μm–GF/F fraction. Fluorescence at the longer excitation wavelength was more heavily weighted in the lower molecular organic ligands relative to that at the shorter excitation wavelength. The binding affinity of organic ligands increased with their molecular weight. These results have significance for further understanding the nature of organic ligands and their biogeochemical role in the aquatic environment.

Characteristics of the fluorescent substances in the Yodo River system by three-dimensional excitation emission matrix spectroscopy

Characteristics of the fluorescent substances in the Yodo River system by three-dimensional excitation emission matrix spectroscopy