Key Role of Mineral Support and Biotic Catalyst in the Formation of Highly Polymeric Soil Humic Acids

摘要

Humic substances (HS) are ubiquitous in natural environments and play an important role in biogeochemical processes. However, their formation and stabilization mechanisms still need to be verified. Several theories have been proposed to describe the origin of HS (1). These theories are common in that: 1) HS are mainly derived from decomposition products of higher plants; 2) transformation of structural precursors into HS occurs by oxidative coupling reactions, initiated by enzymes (homogeneous catalysis) or soil minerals (heterogeneous catalysis); 3) HS are stabilized in soil by adsorption on inorganic soil constituents, which protect them from degradation.