Abstract:
Objective The aims were to explore the adsorption mechanism of earthworm mucus (EM) on basalt, to investigate the formation efficiency of EM during the stepwise adsorption process, and analyze the carbon stability of the complexes, so as to provide theoretical support for increasing the soil carbon storage and promoting the sustainable development of agriculture.
Method The sorption experiments were carried out using EM extracted at pH 5.0, 7.0 and 9.0 with basalt. Moreover, the chemical oxidation of EM-B after sequential sorption was conducted at a pH of 7.0. To study the sorption mechanism of EM-B, the efficiency of the formation of EM in the sequential sorption process of basalt and the carbon stability of the complex were investigated using FTIR, XPS and elemental analysis.
Result The results demonstrated that basalt exhibited the strongest affinity for the sorption of EM (EM7) extracted at pH 7.0. The formation efficiency of mineral-associated organic matter (MAOM) increased with repeated additions of EM. EM-B demonstrated a certain degree of carbon stability during the chemical oxidation process, with the complex formed by initial adsorption exhibiting the most robust carbon stability.
Conclusion The adsorption processes between EM and basalt are mainly driven by electrostatic attraction, ligand exchange, and hydrogen bond interactions. In the later stage of the stepwise adsorption, the organic-organic interactions make the main contribution to the adsorption process. Chemical oxidation leads to a notable reduction in the carbon content of EM7-B. However, the hydrophilic and unsaturated fractions have stronger interactions with basalt, thereby protecting the complex from oxidative degradation.
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