[Composition and Evolution Characteristics of Dissolved Organic Matter During Composting Process].

Area of Science:

• Environmental Chemistry
• Soil Science
• Organic Geochemistry

Background:

• Dissolved organic matter (DOM) plays a crucial role in nutrient cycling and pollutant transport in soils.
• Chicken manure is a significant source of organic matter, and its composting alters DOM characteristics.
• Understanding DOM fractionation is key to assessing the environmental impact and agricultural value of composted manure.

Purpose of the Study:

• To fractionate and characterize dissolved organic matter (DOM) from chicken manure composted over different time periods.
• To investigate the structural and compositional changes in DOM fractions during the composting process.
• To elucidate the influence of composting on the humification degree and functional groups of DOM.

Main Methods:

• Fractionation of DOM using XAD-8 resin based on polarity and charge.
• Characterization of DOM fractions using elemental analysis, Fourier-transform infrared (FTIR) spectroscopy, and 1H-nuclear magnetic resonance (NMR) spectra.
• Quantification of hydrophobic acid (HOA), hydrophobic base (HOB), hydrophobic neutral (HON), acid-insoluble matter (AIM), and hydrophilic matter (HIM) fractions.

Main Results:

• Hydrophilic matter (HIM) and hydrophobic acid (HOA) fractions constituted the major portions (32%-44% and 35%-47%) of DOM, respectively.
• Composting led to a decrease in HIM content and an increase in hydrophobic components, signifying enhanced humification.
• Elemental analysis showed increased N, C, and S content and a decreased H/C ratio, while NMR and FTIR revealed significant structural transformations, including degradation of aliphatic groups and enrichment of benzene groups in certain fractions.

Conclusions:

• Composting significantly alters the composition and structure of DOM in chicken manure, increasing its humification degree.
• The relative abundance of hydrophilic and hydrophobic fractions shifts during composting, impacting DOM's environmental behavior.
• Specific functional groups and structural features of DOM fractions are modified by composting, influencing their reactivity and potential applications.