Fluorescence characteristics of molecular weight fractions of dissolved organic matter derived from composts

Abstract

A study was conducted to determine the fluorescence characteristics of various molecular weight (MW) fractions of dissolved organic matter (DOM) derived from different composts based on fluorescence regional integration (FRI) and parallel factor (PARAFAC) modeling of excitation-emission matrix (EEM) fluorescence spectra. The significant differences in the locations of EEM peaks indicated that there were differences in the molecular structures of the MW >5 kDa fraction and the other fractions. FRI indicated that the degree of humification increased with increasing MW for all of the MW fractions, except for the MW >5 kDa fraction, suggesting that FRI was not suitable for analyzing MW fractions with differences in their molecular structures. PARAFAC modeling resulted in three components for the MW >5 kDa fraction and two components for the other MW fractions. Red-shifting occurred in components 1 (Microbial Humic-like) and 2 (Terrestrial Humic-like) as the MW increased. And component 3 was categorized as a protein-like substance. PARAFAC modeling of the MW fractions can isolate more components and resolve more fluorophores than can DOM analysis.