Fluorescence spectra of water samples were recorded to characterize the dissolved organic matter and as an indicator of water matrix diversity. PARAFAC analysis was applied to the fluorescence spectra to identify underlying humic-like and protein-like signals (Murphy et al. 2014a). A four-component model was split-half validated and the corresponding extracted components are presented in Supplementary material. To assist in identifying the identity of the extracted components, the validated model was cross-referenced with the OpenFluor database (Murphy et al. 2014b). The extracted components, references to similar components, and possible identity are presented in Table 1.
Fluorescence components identified by PARAFAC and comparison results from the OpenFluor database
| Component . | Excitation/Emission maximum(s) (nm) . | Description and possible identity . | References (>0.98 similarity score in OpenFluor) . |
|---|---|---|---|
| C1 | Ex: ≤ 250, 340 nm Em: 470 nm | Terrestrial humic-like; soli-derived fulvic acid | Kowalczuk et al. (2009) (C1) |
| Osburn et al. (2016) (C1) | |||
| Garcia et al. (2018) (C1) | |||
| Du et al. (2021) (C4) | |||
| C2 | Ex: ≤ 250, 315 nm Em: 405 nm | Microbial humic-like | Kowalczuk et al. (2009) (C3) |
| Osburn et al. (2016) (C2) | |||
| Du et al. (2021) (C2) | |||
| C3 | Ex: ≤ 250 nm Em: 420 nm | Terrestrial humic-like | Kowalczuk et al. (2009) (C2) |
| Peleato et al. (2017) (C2) | |||
| Jutaporn et al. (2022) (C3) | |||
| DeFrancesco & Guéguen (2021) (C4) | |||
| C4 | Ex: 275 nm Em: 335 nm | Protein-like/tryptophan-like | Moona et al. (2021) (C5) |
| Peleato et al. (2017) (C5) |
| Component . | Excitation/Emission maximum(s) (nm) . | Description and possible identity . | References (>0.98 similarity score in OpenFluor) . |
|---|---|---|---|
| C1 | Ex: ≤ 250, 340 nm Em: 470 nm | Terrestrial humic-like; soli-derived fulvic acid | Kowalczuk et al. (2009) (C1) |
| Osburn et al. (2016) (C1) | |||
| Garcia et al. (2018) (C1) | |||
| Du et al. (2021) (C4) | |||
| C2 | Ex: ≤ 250, 315 nm Em: 405 nm | Microbial humic-like | Kowalczuk et al. (2009) (C3) |
| Osburn et al. (2016) (C2) | |||
| Du et al. (2021) (C2) | |||
| C3 | Ex: ≤ 250 nm Em: 420 nm | Terrestrial humic-like | Kowalczuk et al. (2009) (C2) |
| Peleato et al. (2017) (C2) | |||
| Jutaporn et al. (2022) (C3) | |||
| DeFrancesco & Guéguen (2021) (C4) | |||
| C4 | Ex: 275 nm Em: 335 nm | Protein-like/tryptophan-like | Moona et al. (2021) (C5) |
| Peleato et al. (2017) (C5) |