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

Abstract

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 uorescence (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 identi ed the key active MW chromophoric (i.e., 0.5, 7.2. 9.5, 26.3, 30.7, and 83.9 kDa) and uorophoric (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 uorophores, and the 0.55 and 3.5 kDa uorophores → 26.3 and 83.9 kDa chromophores.

Chemical and Molecular Profiling of Dissolved Organic Matter within Varied Compost: A Comprehensive Spectroscopic Study

“…Three compost DOM generally exhibited similar MW distributions, exhibiting a ranging from 0.1 to 300 kDa with three discernible clusters of absorption peaks. This chromatographic feature was similar to the ndings observed in our previous study on compost DOM (Yu et al, 2023). The high-MW absorption peaks for RH and WS DOM were located approximately 91 kDa, while HR DOM displayed a higher one (~ 120 kDa).…”

“…It is well known that more humi ed substances generally have a higher chemical stability (Chen et 1, the FI and BIX values for three compost DOM are all higher than 1.9 and 0.6, respectively, signifying that the DOM in these compost samples is primarily produced by microbial activities. Notably, the HIX values, indicative of the degree of humi cation of compost DOM (Guo et al, 2018;Yu et al, 2023), exhibit signi cant differences among three compost DOM. As shown in Table 1, the HIX values follow the order of RH (7.17) > WS (5.79) > HR DOM (2.95).…”

“…DOM in compost samples were extracted according to the method previously described in our previous study (Yu et al, 2023). Brie y, about 2 g of prepared compost sample was mixed with 20 mL ultrapure water and shaken in an oscillator at a speed of 200 r/min at 25°C for 24 hours.…”

“…The ow rate was maintained at 1 mL/min and a sample injection volume of 100 µL was employed. The column was calibrated using a series of polyethylene glycol (PEG) molecular weight standards with known molecular weights (238, 601, 1020, 3450, 4080, 11100, 17900, and 41300 Da) (Yu et al, 2023). The void volume and exclusion limit were veri ed using polystyrene sulfonate (210 kDa) and acetone (58 Da), respectively.…”

“…MW is an important physical and chemical property that affects the structure of compost DOM, offering insights into the degree of compost maturation to a certain extent (He et al, 2015;Yu et al, 2023). In this study, the MW distributions of the three compost DOM were assessed through HPSEC measurements.…”