Comparison between Soil- and Biochar-Derived Humic Acids: Composition, Conformation, and Phenanthrene Sorption

Area of Science:

• Environmental Chemistry
• Soil Science
• Organic Geochemistry

Background:

• Biochar-derived organic matter (BDOM) influences biochar's soil remediation potential.
• Physicochemical properties and sorption behavior of BDOM, particularly humic acids (HAs), remain underexplored.
• Understanding BDOM is crucial for predicting the fate of hydrophobic organic compounds (HOCs) in amended soils.

Purpose of the Study:

• To characterize biochar-derived humic acids (BDHAs) and soil-derived humic acids (SDHAs).
• To investigate the sorption of phenanthrene, a representative HOC, by BDHAs and SDHAs.
• To elucidate the structural components governing HOC sorption in BDHAs and SDHAs.

Main Methods:

• Extraction of HAs from oxidized biochars and soils.
• Characterization using ¹³C NMR spectroscopy and surface area analysis.
• Phenanthrene sorption experiments and analysis after component removal.

Main Results:

• BDHAs exhibited 13.9-69.3% organic carbon recovery and were rich in aromatic and carboxylic carbon.
• BDHAs showed higher phenanthrene sorption capacity than SDHAs, which were rich in aliphatic carbon.
• Amorphous aromatic carbon regulated phenanthrene sorption in BDHAs, while aliphatic moieties dominated sorption in SDHAs.

Conclusions:

• BDHAs and SDHAs possess contrasting physicochemical properties and HOC sorption behaviors.
• Biochar amendment and weathering significantly alter soil organic matter characteristics.
• These alterations impact the fate and transport of HOCs in biochar-amended soils.