Insight into the evolution characteristics on molecular weight of compost dissolved organic matters using high-performance size exclusion chromatography combined with a two-dimensional correlation analysis

The information on molecular weight (MW) characteristics of DOM and relevant evolution behaviors during composting are limited. In this study, DOM extracted from co-composting of chicken manure and rice husks were comprehensively analyzed by using high-performance size exclusion chromatography (HPSEC) combined with a two-dimensional correlation spectroscopy (2D COS) to explore the evolution characteristics of MW of compost DOM. The HPSEC detected at UV of 254 nm and at fluorescence (FL) Ex/Em wavelengths (315/410, 270/455 nm) all showed a gradual increase in both weight-average and number-average MW for DOM, suggesting that the large MW fractions were continuously generated and polymerized during composting. The 2D COS applied on HPSEC-UV and -FL further identified the key active MW chromophoric (i.e., 0.5, 7.2. 9.5, 26.3, 30.7, and 83.9 kDa) and fluorophoric (i.e., 0.55 and 3.5 kDa) molecules that mainly participated in the transformation processes of compost DOM. Moreover, these active MW species were preferentially formed by the order of small to large molecules. A hetero-2D COS analysis disclosed the change sequence in the order of 0.5 and 7.2 kDa chromophores -> 3.5 kDa fluorophores, and the 0.55 and 3.5 kDa fluorophores & RARR; 26.3 and 83.9 kDa chromophores.

Automated summary

The study comprehensively analyzed the molecular weight characteristics of dissolved organic matter (DOM) during composting of chicken manure and rice husks using high-performance size exclusion chromatography (HPSEC) and two-dimensional correlation spectroscopy (2D COS). The results showed that both weight-average and number-average molecular weight of DOM gradually increased during composting, indicating continuous generation and polymerization of high molecular weight fractions. The 2D COS analysis identified key active molecules involved in the transformation processes of compost DOM, with a preference for smaller molecules. Hetero-2D COS analysis revealed the change sequence of chromophores and fluorophores during the composting process.