| Title |
Evaluation of Optical Tracers for Quantifying TOC Contributions from Non-Point Source in Baseflow of Agricultural Watersheds |
| Authors |
김정훈(Jeong-Hoon Kim) ; 박태준(Tae Jun Park) ; 김규범(Gyoo-Bum Kim) ; 허진(Jin Hur) |
| DOI |
https://doi.org/10.15681/KSWE.2025.41.5.337 |
| Keywords |
Baseflow; Dissolved organic matter; End-member mixing analysis; Non-point sources; Spectroscopic indicators |
| Abstract |
In agricultural watersheds, dissolved organic matter (DOM) from both natural and human-induced sources is transported to streams via baseflow after soil infiltration. Baseflow, a key hydrological component during low-flow periods, significantly contributes to the total organic carbon loads in receiving waters. However, no research has traced DOM sources through baseflow pathways. This study aimed to assess the effectiveness of optical indicators in identifying DOM sources in baseflow using end-member mixing analysis. We selected litter- and compost-derived DOM as contrasting end-members of terrestrial organic matter and compared their spectroscopic characteristics before and after soil interaction through batch adsorption and soil column infiltration experiments. Both end-members showed decreased specific UV absorbance (SUVA) and increased humification index (HIX) and biological index (BIX) after adsorption, indicating a preferential removal of smaller-sized aromatic compounds. Parallel factor analysis (PARAFAC) consistently revealed an increase in humic-like components (C1) and a decrease in protein-/polyphenol-like components (C2). Among the various spectroscopic indices, BIX and the fluorescence index (FI) demonstrated strong linearity (R²: BIX=0.99, FI=0.95) and high source sensitivity (slope-to-standard deviation ratio, S/SD: BIX=0.06, FI=0.05) across different mixing ratios and conditions. These findings suggest that BIX and FI are reliable tracers for quantifying DOM source contributions via baseflow, even after substantial soil interaction. In contrast, PARAFAC-derived components (%C1 and %C2) showed limited applicability under column conditions. This study underscores the value of fluorescence indices?particularly BIX and FI?as effective tools for tracking DOM sources in agricultural landscapes and provides a scientific foundation for managing non-point source pollution through baseflow pathways. |