Characterizing the photochemical degradation of aquatic humic substances from a dystrophic lake using excitation-emission matrix fluorescence spectroscopy and parallel factor analysis

Abstract

Three-dimensional excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PAR-AFAC) were used to monitor composition and reactivity changes caused by the photochemical degradation of aquatic humic substances (AHS) from a dystrophic lake in Kushiro Wetland, Japan. AHS-rich lake water was exposed to three treatments in summer and winter 2014: radiation with the full solar wavelength range, radiation with the [320-nm solar wavelength range, and no solar radiation. Irradiation caused AHS-like peaks to shift to shorter wavelengths in the EEM contour plots, implying that AHS photodegradation caused the formation of lower-molecular-weight fractions or more simply structured components. Three components were identified from PARAFAC analyses: AHS-1 (excitation/emission wavelengths of maxima: \252 and 315 nm/426 nm), AHS-2 (360 and 261 nm/489 nm), and AHS-3 (276 nm/403 nm). These components had different photosensitivities. AHS-1 was most sensitive to full solar radiation, while AHS-2 was most sensitive to [320-nm radiation. More photodegradation of these components occurred in the summer than in the winter, indicating that photodegradation depended on light intensity. AHS-3 was photoresistant. The different characteristics of the components reflected the in situ dynamics of the components. The AHS-3 fluorescence intensity was positively correlated with the dissolved organic carbon concentration but the AHS-1 and AHS-2 fluorescence intensities were not. The EEM-PARAFAC method was found to be a good tool for tracing AHS-like materials in situ and in the laboratory.

Influence of parasitic chytrids on the quantity and quality of algal dissolved organic matter (AOM)

“…The quality of DOM was analyzed using three-dimensional excitation-emission matrices (EEMs) combined with parallel factor analysis (PARAFAC). EEM-PARAFAC has can be used to detect humic-like and protein-like substances with high sensitivity (Yamashita et al 2010;Senga et al 2017). We also determined the concentrations of carbohydrates without fluorescence properties using a colorimetric method.…”

“…The integration time was 1 s. Each EEM data point was corrected for the inner-filter effect, Rayleigh masking, and Raman scattering using Aqualog v3.6 software. Further details of the procedures used can be found in Senga et al (2017).…”

Mathematical Model Regarding the Application of the Excitation-Emission Matrix Spectroscopy in Nanofiltration Process Using Humic Acid with a TiO2 Ceramic Membrane

“…The humic acid solutions used in the experiments were produced by adding increasing concentrations (10, 25, 50, 75, 100 mg/L) of this reagent (Aldrich Chemistry) to ultrapure water in a tank of 50 L capacity [1,46]. Humic acid was chosen as a pollutant because, according to the literature, humic materials contain, in addition to fulvic acid, many phytochemical nutritional groups including natural sterols, hormones, fatty acids, polyphenols and ketones with subgroups including compounds such as: flavonoids, flavones, flavins, catechins, tannins, quinones, isoflavones, tocopherols and others [47][48][49][50], components that are also commonly found in natural and wastewater treated by the NF process.…”

Ceramic Nanofiltration Membrane Fouling: Application of Mathematical Modelling to the Use of Excitation Emission Matrix Spectroscopy

“…It is made from organic soil (humus) after microbial decomposition of vegetation [1,[27][28][29]. Because humic substances (HS) are naturally occurring compounds, with the highest chemical activity, they simulate organic matter from flowing waters, lakes and ocean waters, which led to the choice of this contaminant for experiments as foulant models [1,[30][31][32].…”