Fluorescence Excitation−Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter

Abstract

Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the > 10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (phi(i,n)). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (phi(T,n) = sigma phi(i,n)) was observed for hydrophobic neutral DOM fractions, followed by lower phi(T,n) values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

Effect of inoculation with a microbial consortium that degrades organic acids on the composting efficiency of food waste

“…After regulating the scattering using interpolation in the areas affected by first‐ and second‐order Rayleigh and Raman scatter, the FRI technique was adopted for analysis (Chen et al ., 2003). …”

Influence of natural zeolite and nitrification inhibitor on organics degradation and nitrogen transformation during sludge composting

“…3). Following Chen et al (2003), the EEM spectra can be divided into five regions depending on the wavelengths of the organics as follows: regions I and II, aromatic proteins; region III, fulvic acid-like substances; region IV, soluble microbial by-product-like substances; and region V, humic acid-like Fig. 3 Evolution of EEM spectra during sludge composting.…”

Characterization of dissolved organic matter for prediction of trihalomethane formation potential in surface and sub-surface waters

“…Fluorescence excitation-emission matrix (F-EEM) spectra were acquired (Model LS 55, PerkinElmer) to characterize DOM in terms of humic-like (HA), fulvic-like (FA), Protein1 (PI), Protein2 (PII) and soluble microbial protein (SMP)-like components [40]. A series of emission spectra (280-600 nm) were obtained with 0.5 nm increments over excitation wavelength (200-500 nm) with 5 nm increments.…”

“…MQW spectra were subtracted from the measured sample spectra. The method of Chen et al [40] was employed to calculate the relative abundance of each organic group. Samples for F-EEM were pre-diluted by addition of MQW to minimize the inner-filter effect followed by pre-filtering through 0.45 m pre-rinsed sterile cellulose membrane filters.…”

“…In our study, F-EEM spectra of DOM were acquired to identify five different EEM regions (HA, FA, PI, PII and SMP) for each sample and to calculate the relative abundance of each organic group as detailed by Chen et al [40]. DOM present in runoff and sub-surface waters can be characterized based on the relative abundances (as percentages) of these five organic groups i.e., PI, PII, SMP, FA and HA.…”