Spectroscopic and molecular characterization of humic substances (HS) from soils and sediments in a watershed: comparative study of HS chemical fractions and the origins

Morgane Derrien, Yun Kyung Lee, Jae Eun Park, Penghui Li, Meilian Chen, Sang Hee Lee, Soo Hyung Lee, Jun Bae Lee, Jin Hur*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Optical properties and molecular composition of humic substances (HS) can provide valuable information on the sources and the history of the associated biogeochemical processes. In this study, many well-known spectral and molecular characteristics were examined in eight different HS samples, which were extracted from soils and sediments located in a forested watershed, via two advanced tools including fluorescence excitation emission matrix-parallel factor analysis (EEM-PARAFAC) and high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Two humic-like (C1 and C2) and one protein-like (C3) components were identified from EEM-PARAFAC. Irrespective of the origins, humic acid (HA) fractions were distinguished from fulvic acid (FA) fractions by the HS characteristics of specific UV absorbance (SUVA), the number of formulas, maximum fluorescence intensities of C1 and C2, condensed aromatics, tannins, and CHON, CHOS, and CHONS classes. In contrast, only five HS indices, including C3 intensity, H%, modified aromatic index (AImod), the percentages of carbohydrates, and unsaturated hydrocarbons, were found to be significant factors in discriminating between the two HS origins (i.e., soils and sediments). The ordination of the Bray-Curtis dissimilarity matrix further confirmed that the HS chemical fraction (i.e., HA or FA) was the more important factor to determine the measured HS characteristics than the HS origin. Our results provided an in-depth insight into the chemical and structural heterogeneity of bulk HS, which could be even beyond the differences observed along the two HS origins. This study also delivers a cautious message that the two operationally defined HS chemical fractions should be carefully considered in tracking the origins of different HS samples.

Original languageEnglish
Pages (from-to)16933-16945
Number of pages13
JournalEnvironmental Science and Pollution Research
Volume24
Issue number20
DOIs
StatePublished - 1 Jul 2017
Externally publishedYes

Keywords

  • EEM-PARAFAC
  • FT-ICR MS
  • Fulvic acid
  • Humic acid
  • Sediments
  • Soils

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