Solar and water-induced lignin degradation: Catalyzing the acceleration of plant biomass carbon cycling.

Abstract

Photodegradation is an important factor that affects the terrestrial carbon cycle. Lignin is a main component of plant biomass, easily and selectively undergoes photodegradation. Moreover, lignin provides key information that is essential for studying photodegradation of plant biomass. Enzymatic hydrolysis lignin (EHL) was used in a novel investigation of photodegradation of plant biomass in the presence of various quantities of sprayed water. The EHL specimen without sprayed water exhibited obvious photooxidation, cleavage and depolymerization under ultraviolet radiation; its C and H contents declined; its residue yield increased by 1.00 %; and its O/C ratio, C4, and O2 growth rates based on X-Ray photoelectron spectroscopy increased by 15.15 %, 27.11 %, and 132.09 %, respectively. Water has been shown to play an important role in lignin photodegradation, with a moderate amount resulting in the highest oxidation degree. Importantly, photodegradation of lignin accelerates the return of fixated carbon to the atmosphere. EHL sprayed 0.46 g g^-1 water exhibited an obvious decrease in C (-2.64 %), C1s (-6.89 %), C1 (-12.53 %), and C2 (-19.92 %) content after 320 h of UV exposure. This study provides a new perspective to further understand the effects of plant biomass photodegradation on terrestrial carbon cycling.